Improving the performance of a compression ignition engine by directing flow of inlet air
NASA Technical Reports Server (NTRS)
Kemper, Carlton
1946-01-01
The object of this report is to present the results of tests performed by the National Advisory Committee for Aeronautics to determine the effect on engine performance of directing the flow of the inlet air to a 5-inch by 7-inch cylinder, solid injection, compression ignition engine, After a few preliminary tests, comparative runs were made at a speed of 1500 r.p.m. with and without directed air flow. It was found that directing the flow of the inlet air toward the fuel injection valve gave steadier engine operation, and an appreciable increase in power, and decreased fuel consumption. The results indicate the possibility of improving the performance of a given type of combustion chamber without changing its shape and with no change in valve timing. They would also seem to prove that directional turbulence, set up before the inlet valve of a four-stroke cycle engine, continues in the engine cylinder throughout the compression stroke.
Fuel Spray and Flame Formation in a Compression-Ignition Engine Employing Air Flow
NASA Technical Reports Server (NTRS)
Rothrock, A M; Waldron, C D
1937-01-01
The effects of air flow on fuel spray and flame formation in a high-speed compression-ignition engine have been investigated by means of the NACA combustion apparatus. The process was studied by examining high-speed motion pictures taken at the rate of 2,200 frames a second. The combustion chamber was of the flat-disk type used in previous experiments with this apparatus. The air flow was produced by a rectangular displacer mounted on top of the engine piston. Three fuel-injection nozzles were tested: a 0.020-inch single-orifice nozzle, a 6-orifice nozzle, and a slit nozzle. The air velocity within the combustion chamber was estimated to reach a value of 425 feet a second. The results show that in no case was the form of the fuel spray completely destroyed by the air jet although in some cases the direction of the spray was changed and the spray envelope was carried away by the moving air. The distribution of the fuel in the combustion chamber of a compression-ignition engine can be regulated to some extent by the design of the combustion chamber, by the design of the fuel-injection nozzle, and by the use of air flow.
Integrated LTCC Pressure/Flow/Temperature Multisensor for Compressed Air Diagnostics†
Fournier, Yannick; Maeder, Thomas; Boutinard-Rouelle, Grégoire; Barras, Aurélie; Craquelin, Nicolas; Ryser, Peter
2010-01-01
We present a multisensor designed for industrial compressed air diagnostics and combining the measurement of pressure, flow, and temperature, integrated with the corresponding signal conditioning electronics in a single low-temperature co-fired ceramic (LTCC) package. The developed sensor may be soldered onto an integrated electro-fluidic platform by using standard surface mount device (SMD) technology, e.g., as a standard electronic component would be on a printed circuit board, obviating the need for both wires and tubes and thus paving the road towards low-cost integrated electro-fluidic systems. Several performance aspects of this device are presented and discussed, together with electronics design issues. PMID:22163518
Turbulence in Compressible Flows
NASA Technical Reports Server (NTRS)
1997-01-01
Lecture notes for the AGARD Fluid Dynamics Panel (FDP) Special Course on 'Turbulence in Compressible Flows' have been assembled in this report. The following topics were covered: Compressible Turbulent Boundary Layers, Compressible Turbulent Free Shear Layers, Turbulent Combustion, DNS/LES and RANS Simulations of Compressible Turbulent Flows, and Case Studies of Applications of Turbulence Models in Aerospace.
Considerations of Air Flow in Combustion Chambers of High-Speed Compression-Ignition Engines
NASA Technical Reports Server (NTRS)
Spanogle, J A; Moore, C S
1932-01-01
The air flow in combustion chambers is divided into three fundamental classes - induced, forced, and residual. A generalized resume is given of the present status of air flow investigations and of the work done at this and other laboratories to determine the direction and velocity of air movement in auxiliary and integral combustion chambers. The effects of air flow on engine performance are mentioned to show that although air flow improves the combustion efficiency, considerable induction, friction, and thermal losses must be guarded against.
NASA Technical Reports Server (NTRS)
Melcher, Kevin J.
2006-01-01
The Compressible Flow Toolbox is primarily a MATLAB-language implementation of a set of algorithms that solve approximately 280 linear and nonlinear classical equations for compressible flow. The toolbox is useful for analysis of one-dimensional steady flow with either constant entropy, friction, heat transfer, or Mach number greater than 1. The toolbox also contains algorithms for comparing and validating the equation-solving algorithms against solutions previously published in open literature. The classical equations solved by the Compressible Flow Toolbox are as follows: The isentropic-flow equations, The Fanno flow equations (pertaining to flow of an ideal gas in a pipe with friction), The Rayleigh flow equations (pertaining to frictionless flow of an ideal gas, with heat transfer, in a pipe of constant cross section), The normal-shock equations, The oblique-shock equations, and The expansion equations.
NASA Technical Reports Server (NTRS)
Spanogle, J A; Moore, C S
1931-01-01
Presented here are the results of performance tests made with a single-cylinder, four stroke cycle, compression-ignition engine. These tests were made on a precombustion chamber type of cylinder head designed to have air velocity and tangential air flow in both the chamber and cylinder. The performance was investigated for variable load and engine speed, type of fuel spray, valve opening pressure, injection period and, for the spherical chamber, position of the injection spray relative to the air flow. The pressure variations between the pear-shaped precombustion chamber and the cylinder for motoring and full load conditions were determined with a Farnboro electric indicator. The combustion chamber designs tested gave good mixing of a single compact fuel spray with the air, but did not control the ensuing combustion sufficiently. Relative to each other, the velocity of air flow was too high, the spray dispersion by injection too great, and the metering effect of the cylinder head passage insufficient. The correct relation of these factors is of the utmost importance for engine performance.
Piston reciprocating compressed air engine
Cestero, L.G.
1987-03-24
A compressed air engine is described comprising: (a). a reservoir of compressed air, (b). two power cylinders each containing a reciprocating piston connected to a crankshaft and flywheel, (c). a transfer cylinder which communicates with each power cylinder and the reservoir, and contains a reciprocating piston connected to the crankshaft, (d). valve means controlled by rotation of the crankshaft for supplying compressed air from the reservoir to each power cylinder and for exhausting compressed air from each power cylinder to the transfer cylinder, (e). valve means controlled by rotation of the crankshaft for supplying from the transfer cylinder to the reservoir compressed air supplied to the transfer cylinder on the exhaust strokes of the pistons of the power cylinders, and (f). an externally powered fan for assisting the exhaust of compressed air from each power cylinder to the transfer cylinder and from there to the compressed air reservoir.
NASA Technical Reports Server (NTRS)
Runyan, Harry L; Watkins, Charles E
1953-01-01
This report treats the effect of wind-tunnel walls on the oscillating two-dimensional air forces in a compressible medium. The walls are simulated by the usual method of placing images at appropriate distances above and below the wing. An important result shown is that, for certain conditions of wing frequency, tunnel height, and Mach number, the tunnel and wing may form a resonant system so that the forces on the wing are greatly changed from the condition of no tunnel walls. It is pointed out that similar conditions exist for three-dimensional flow in circular and rectangular tunnels and apparently, within certain Mach number ranges, in tunnels of nonuniform cross section or even in open tunnels or jets.
Computer program for compressible flow network analysis
NASA Technical Reports Server (NTRS)
Wilton, M. E.; Murtaugh, J. P.
1973-01-01
Program solves problem of an arbitrarily connected one dimensional compressible flow network with pumping in the channels and momentum balancing at flow junctions. Program includes pressure drop calculations for impingement flow and flow through pin fin arrangements, as currently found in many air cooled turbine bucket and vane cooling configurations.
Compressed air energy storage system
Ahrens, F.W.; Kartsounes, G.T.
1981-07-28
An internal combustion reciprocating engine is operable as a compressor during slack demand periods utilizing excess power from a power grid to charge air into an air storage reservoir and as an expander during peak demand periods to feed power into the power grid utilizing air obtained from the air storage reservoir together with combustible fuel. Preferably the internal combustion reciprocating engine is operated at high pressure and a low pressure turbine and compressor are also employed for air compression and power generation.
Compressed air energy storage system
Ahrens, Frederick W.; Kartsounes, George T.
1981-01-01
An internal combustion reciprocating engine is operable as a compressor during slack demand periods utilizing excess power from a power grid to charge air into an air storage reservoir and as an expander during peak demand periods to feed power into the power grid utilizing air obtained from the air storage reservoir together with combustible fuel. Preferably the internal combustion reciprocating engine is operated at high pressure and a low pressure turbine and compressor are also employed for air compression and power generation.
Compressed air energy storage system
Ahrens, F.W.; Kartsounes, G.T.
An internal combustion reciprocating engine is operable as a compressor during slack demand periods utilizing excess power from a power grid to charge air into an air storage reservoir and as an expander during peak demand periods to feed power into the power grid utilizing air obtained from the air storage reservoir together with combustion reciprocating engine is operated at high pressure and a low pressure turbine and compressor are also employed for air compression and power generation.
29 CFR 1917.154 - Compressed air.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 29 Labor 7 2012-07-01 2012-07-01 false Compressed air. 1917.154 Section 1917.154 Labor Regulations...) MARINE TERMINALS Related Terminal Operations and Equipment § 1917.154 Compressed air. Employees shall be... this part during cleaning with compressed air. Compressed air used for cleaning shall not exceed...
29 CFR 1917.154 - Compressed air.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 29 Labor 7 2013-07-01 2013-07-01 false Compressed air. 1917.154 Section 1917.154 Labor Regulations...) MARINE TERMINALS Related Terminal Operations and Equipment § 1917.154 Compressed air. Employees shall be... this part during cleaning with compressed air. Compressed air used for cleaning shall not exceed...
29 CFR 1917.154 - Compressed air.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 29 Labor 7 2014-07-01 2014-07-01 false Compressed air. 1917.154 Section 1917.154 Labor Regulations...) MARINE TERMINALS Related Terminal Operations and Equipment § 1917.154 Compressed air. Employees shall be... this part during cleaning with compressed air. Compressed air used for cleaning shall not exceed...
29 CFR 1917.154 - Compressed air.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 29 Labor 7 2011-07-01 2011-07-01 false Compressed air. 1917.154 Section 1917.154 Labor Regulations...) MARINE TERMINALS Related Terminal Operations and Equipment § 1917.154 Compressed air. Employees shall be... this part during cleaning with compressed air. Compressed air used for cleaning shall not exceed...
29 CFR 1917.154 - Compressed air.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 29 Labor 7 2010-07-01 2010-07-01 false Compressed air. 1917.154 Section 1917.154 Labor Regulations...) MARINE TERMINALS Related Terminal Operations and Equipment § 1917.154 Compressed air. Employees shall be... this part during cleaning with compressed air. Compressed air used for cleaning shall not exceed...
30 CFR 75.1730 - Compressed air; general; compressed air systems.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Compressed air; general; compressed air systems... Compressed air; general; compressed air systems. (a) All pressure vessels shall be constructed, installed... Safety and Health district office. (b) Compressors and compressed-air receivers shall be equipped...
30 CFR 75.1730 - Compressed air; general; compressed air systems.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Compressed air; general; compressed air systems... Compressed air; general; compressed air systems. (a) All pressure vessels shall be constructed, installed... Safety and Health district office. (b) Compressors and compressed-air receivers shall be equipped...
30 CFR 75.1730 - Compressed air; general; compressed air systems.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Compressed air; general; compressed air systems... Compressed air; general; compressed air systems. (a) All pressure vessels shall be constructed, installed... Safety and Health district office. (b) Compressors and compressed-air receivers shall be equipped...
30 CFR 75.1730 - Compressed air; general; compressed air systems.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Compressed air; general; compressed air systems... Compressed air; general; compressed air systems. (a) All pressure vessels shall be constructed, installed... Safety and Health district office. (b) Compressors and compressed-air receivers shall be equipped...
30 CFR 75.1730 - Compressed air; general; compressed air systems.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Compressed air; general; compressed air systems... Compressed air; general; compressed air systems. (a) All pressure vessels shall be constructed, installed... Safety and Health district office. (b) Compressors and compressed-air receivers shall be equipped...
Chapter 22: Compressed Air Evaluation Protocol
Benton, N.
2014-11-01
Compressed-air systems are used widely throughout industry for many operations, including pneumatic tools, packaging and automation equipment, conveyors, and other industrial process operations. Compressed-air systems are defined as a group of subsystems composed of air compressors, air treatment equipment, controls, piping, pneumatic tools, pneumatically powered machinery, and process applications using compressed air. A compressed-air system has three primary functional subsystems: supply, distribution, and demand. Air compressors are the primary energy consumers in a compressed-air system and are the primary focus of this protocol. The two compressed-air energy efficiency measures specifically addressed in this protocol are: high-efficiency/variable speed drive (VSD) compressor replacing modulating compressor; compressed-air leak survey and repairs. This protocol provides direction on how to reliably verify savings from these two measures using a consistent approach for each.
Compression Shocks of Detached Flow
NASA Technical Reports Server (NTRS)
Eggink
1947-01-01
It is known that compression shocks which lead from supersonic to subsonic velocity cause the flow to separate on impact on a rigid wall. Such shocks appear at bodies with circular symmetry or wing profiles on locally exceeding sonic velocity, and in Laval nozzles with too high a back pressure. The form of the compression shocks observed therein is investigated.
COMPRESSIBLE FLOW, ENTRAINMENT, AND MEGAPLUME
It is generally believed that low Mach number, i.e., low-velocity, flow may be assumed to be incompressible flow. Under steady-state conditions, an exact equation of continuity may then be used to show that such flow is non-divergent. However, a rigorous, compressible fluid-dynam...
NASA Technical Reports Server (NTRS)
Krebs, R. P.
1971-01-01
The computer program described in this report calculates the design-point characteristics of a compressed-air generator for use in V/STOL applications such as systems with a tip-turbine-driven lift fan. The program computes the dimensions and mass, as well as the thermodynamic performance of a model air generator configuration which involves a straight through-flow combustor. Physical and thermodynamic characteristics of the air generator components are also given. The program was written in FORTRAN IV language. Provision has been made so that the program will accept input values in either SI units or U.S. customary units. Each air generator design-point calculation requires about 1.5 seconds of 7094 computer time for execution.
Analytical and experimental study on complex compressed air pipe network
NASA Astrophysics Data System (ADS)
Gai, Yushou; Cai, Maolin; Shi, Yan
2015-09-01
To analyze the working characteristics of complex compressed air networks, numerical methods are widely used which are based on finite element technology or intelligent algorithms. However, the effectiveness of the numerical methods is limited. In this paper, to provide a new method to optimize the design and the air supply strategy of the complex compressed air pipe network, firstly, a novel method to analyze the topology structure of the compressed air flow in the pipe network is initially proposed. A matrix is used to describe the topology structure of the compressed air flow. Moreover, based on the analysis of the pressure loss of the pipe network, the relationship between the pressure and the flow of the compressed air is derived, and a prediction method of pressure fluctuation and air flow in a segment in a complex pipe network is proposed. Finally, to inspect the effectiveness of the method, an experiment with a complex network is designed. The pressure and the flow of airflow in the network are measured and studied. The results of the study show that, the predicted results with the proposed method have a good consistency with the experimental results, and that verifies the air flow prediction method of the complex pipe network. This research proposes a new method to analyze the compressed air network and a prediction method of pressure fluctuation and air flow in a segment, which can predicate the fluctuation of the pressure according to the flow of compressed air, and predicate the fluctuation of the flow according to the pressure in a segment of a complex pipe network.
29 CFR 1926.803 - Compressed air.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 29 Labor 8 2010-07-01 2010-07-01 false Compressed air. 1926.803 Section 1926.803 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR CONSTRUCTION Underground Construction, Caissons, Cofferdams and Compressed Air § 1926.803 Compressed...
Industrial Compressed Air System Energy Efficiency Guidebook.
United States. Bonneville Power Administration.
1993-12-01
Energy efficient design, operation and maintenance of compressed air systems in industrial plants can provide substantial reductions in electric power and other operational costs. This guidebook will help identify cost effective, energy efficiency opportunities in compressed air system design, re-design, operation and maintenance. The guidebook provides: (1) a broad overview of industrial compressed air systems, (2) methods for estimating compressed air consumption and projected air savings, (3) a description of applicable, generic energy conservation measures, and, (4) a review of some compressed air system demonstration projects that have taken place over the last two years. The primary audience for this guidebook includes plant maintenance supervisors, plant engineers, plant managers and others interested in energy management of industrial compressed air systems.
Seneca Compressed Air Energy Storage (CAES) Project
2012-11-30
This document provides specifications for the process air compressor for a compressed air storage project, requests a budgetary quote, and provides supporting information, including compressor data, site specific data, water analysis, and Seneca CAES value drivers.
Flow quality measurements in compressible subsonic flows
NASA Technical Reports Server (NTRS)
Stainback, P. Calvin; Johnson, Charles B.
1987-01-01
The purpose is to re-examine the heat transfer from a hot-wire probe in the compressible subsonic flow regime; describe the three-wire hot-wire probe calibration and data reduction techniques used to measure the velocity, density, and total temperature fluctuation; and present flow quality results obtained in the Langley 0.3 meter Transonic Cryogenic Wind Tunnel and in flight with the NASA JetStar from the same three-wire hot-wire probe.
Recoil Experiments Using a Compressed Air Cannon
ERIC Educational Resources Information Center
Taylor, Brett
2006-01-01
Ping-Pong vacuum cannons, potato guns, and compressed air cannons are popular and dramatic demonstrations for lecture and lab. Students enjoy them for the spectacle, but they can also be used effectively to teach physics. Recently we have used a student-built compressed air cannon as a laboratory activity to investigate impulse, conservation of…
Turbulence modeling for compressible flows
NASA Technical Reports Server (NTRS)
Marvin, J. G.
1977-01-01
Material prepared for a course on Applications and Fundamentals of Turbulence given at the University of Tennessee Space Institute, January 10 and 11, 1977, is presented. A complete concept of turbulence modeling is described, and examples of progess for its use in computational aerodynimics are given. Modeling concepts, experiments, and computations using the concepts are reviewed in a manner that provides an up-to-date statement on the status of this problem for compressible flows.
Turbulence modeling for high speed compressible flows
NASA Technical Reports Server (NTRS)
Chandra, Suresh
1993-01-01
The following grant objectives were delineated in the proposal to NASA: to offer course work in computational fluid dynamics (CFD) and related areas to enable mechanical engineering students at North Carolina A&T State University (N.C. A&TSU) to pursue M.S. studies in CFD, and to enable students and faculty to engage in research in high speed compressible flows. Since no CFD-related activity existed at N.C. A&TSU before the start of the NASA grant period, training of students in the CFD area and initiation of research in high speed compressible flows were proposed as the key aspects of the project. To that end, graduate level courses in CFD, boundary layer theory, and fluid dynamics were offered. This effort included initiating a CFD course for graduate students. Also, research work was performed on studying compressibility effects in high speed flows. Specifically, a modified compressible dissipation model, which included a fourth order turbulent Mach number term, was incorporated into the SPARK code and verified for the air-air mixing layer case. The results obtained for this case were compared with a wide variety of experimental data to discern the trends in the mixing layer growth rates with varying convective Mach numbers. Comparison of the predictions of the study with the results of several analytical models was also carried out. The details of the research study are described in the publication entitled 'Compressibility Effects in Modeling Turbulent High Speed Mixing Layers,' which is attached to this report.
Turbulence modeling for high speed compressible flows
NASA Astrophysics Data System (ADS)
Chandra, Suresh
1993-08-01
The following grant objectives were delineated in the proposal to NASA: to offer course work in computational fluid dynamics (CFD) and related areas to enable mechanical engineering students at North Carolina A&T State University (N.C. A&TSU) to pursue M.S. studies in CFD, and to enable students and faculty to engage in research in high speed compressible flows. Since no CFD-related activity existed at N.C. A&TSU before the start of the NASA grant period, training of students in the CFD area and initiation of research in high speed compressible flows were proposed as the key aspects of the project. To that end, graduate level courses in CFD, boundary layer theory, and fluid dynamics were offered. This effort included initiating a CFD course for graduate students. Also, research work was performed on studying compressibility effects in high speed flows. Specifically, a modified compressible dissipation model, which included a fourth order turbulent Mach number term, was incorporated into the SPARK code and verified for the air-air mixing layer case. The results obtained for this case were compared with a wide variety of experimental data to discern the trends in the mixing layer growth rates with varying convective Mach numbers. Comparison of the predictions of the study with the results of several analytical models was also carried out. The details of the research study are described in the publication entitled 'Compressibility Effects in Modeling Turbulent High Speed Mixing Layers,' which is attached to this report.
University of Arizona Compressed Air Energy Storage
Simmons, Joseph; Muralidharan, Krishna
2012-12-31
Boiled down to its essentials, the grant’s purpose was to develop and demonstrate the viability of compressed air energy storage (CAES) for use in renewable energy development. While everyone agrees that energy storage is the key component to enable widespread adoption of renewable energy sources, the development of a viable scalable technology has been missing. The Department of Energy has focused on expanded battery research and improved forecasting, and the utilities have deployed renewable energy resources only to the extent of satisfying Renewable Portfolio Standards. The lack of dispatchability of solar and wind-based electricity generation has drastically increased the cost of operation with these components. It is now clear that energy storage coupled with accurate solar and wind forecasting make up the only combination that can succeed in dispatchable renewable energy resources. Conventional batteries scale linearly in size, so the price becomes a barrier for large systems. Flow batteries scale sub-linearly and promise to be useful if their performance can be shown to provide sufficient support for solar and wind-base electricity generation resources. Compressed air energy storage provides the most desirable answer in terms of scalability and performance in all areas except efficiency. With the support of the DOE, Tucson Electric Power and Science Foundation Arizona, the Arizona Research Institute for Solar Energy (AzRISE) at the University of Arizona has had the opportunity to investigate CAES as a potential energy storage resource.
Krylov methods for compressible flows
NASA Technical Reports Server (NTRS)
Tidriri, M. D.
1995-01-01
We investigate the application of Krylov methods to compressible flows, and the effect of implicit boundary conditions on the implicit solution of nonlinear problems. Two defect-correction procedures, namely, approximate factorization (AF) for structured grids and ILU/GMRES for general grids, are considered. Also considered here are Newton-Krylov matrix-free methods that we combined with the use of mixed discretization schemes in the implicitly defined Jacobian and its preconditioner. Numerical experiments that show the performance of our approaches are then presented.
Compressed Air/Vacuum Transportation Techniques
NASA Astrophysics Data System (ADS)
Guha, Shyamal
2011-03-01
General theory of compressed air/vacuum transportation will be presented. In this transportation, a vehicle (such as an automobile or a rail car) is powered either by compressed air or by air at near vacuum pressure. Four version of such transportation is feasible. In all versions, a ``c-shaped'' plastic or ceramic pipe lies buried a few inches under the ground surface. This pipe carries compressed air or air at near vacuum pressure. In type I transportation, a vehicle draws compressed air (or vacuum) from this buried pipe. Using turbine or reciprocating air cylinder, mechanical power is generated from compressed air (or from vacuum). This mechanical power transferred to the wheels of an automobile (or a rail car) drives the vehicle. In type II-IV transportation techniques, a horizontal force is generated inside the plastic (or ceramic) pipe. A set of vertical and horizontal steel bars is used to transmit this force to the automobile on the road (or to a rail car on rail track). The proposed transportation system has following merits: virtually accident free; highly energy efficient; pollution free and it will not contribute to carbon dioxide emission. Some developmental work on this transportation will be needed before it can be used by the traveling public. The entire transportation system could be computer controlled.
LOW-VELOCITY COMPRESSIBLE FLOW THEORY
The widespread application of incompressible flow theory dominates low-velocity fluid dynamics, virtually preventing research into compressible low-velocity flow dynamics. Yet, compressible solutions to simple and well-defined flow problems and a series of contradictions in incom...
30 CFR 56.13020 - Use of compressed air.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Use of compressed air. 56.13020 Section 56... MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Compressed Air and Boilers § 56.13020 Use of compressed air. At no time shall compressed air be directed toward a...
30 CFR 56.13020 - Use of compressed air.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Use of compressed air. 56.13020 Section 56... MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Compressed Air and Boilers § 56.13020 Use of compressed air. At no time shall compressed air be directed toward a...
30 CFR 57.13020 - Use of compressed air.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Use of compressed air. 57.13020 Section 57... MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-UNDERGROUND METAL AND NONMETAL MINES Compressed Air and Boilers § 57.13020 Use of compressed air. At no time shall compressed air be directed toward...
30 CFR 77.412 - Compressed air systems.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Compressed air systems. 77.412 Section 77.412... for Mechanical Equipment § 77.412 Compressed air systems. (a) Compressors and compressed-air receivers... involving the pressure system of compressors, receivers, or compressed-air-powered equipment shall not...
30 CFR 56.13020 - Use of compressed air.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Use of compressed air. 56.13020 Section 56... MINE SAFETY AND HEALTH SAFETY AND HEALTH STANDARDS-SURFACE METAL AND NONMETAL MINES Compressed Air and Boilers § 56.13020 Use of compressed air. At no time shall compressed air be directed toward a...
General Equation Set Solver for Compressible and Incompressible Turbomachinery Flows
NASA Technical Reports Server (NTRS)
Sondak, Douglas L.; Dorney, Daniel J.
2002-01-01
Turbomachines for propulsion applications operate with many different working fluids and flow conditions. The flow may be incompressible, such as in the liquid hydrogen pump in a rocket engine, or supersonic, such as in the turbine which may drive the hydrogen pump. Separate codes have traditionally been used for incompressible and compressible flow solvers. The General Equation Set (GES) method can be used to solve both incompressible and compressible flows, and it is not restricted to perfect gases, as are many compressible-flow turbomachinery solvers. An unsteady GES turbomachinery flow solver has been developed and applied to both air and water flows through turbines. It has been shown to be an excellent alternative to maintaining two separate codes.
Modeling the exit velocity of a compressed air cannon
NASA Astrophysics Data System (ADS)
Rohrbach, Z. J.; Buresh, T. R.; Madsen, M. J.
2012-01-01
The use of compressed air cannons in an undergraduate laboratory provides a way to illustrate the connection between diverse physics concepts, such as conservation of momentum, the work-kinetic energy theorem, gas expansion, air drag, and elementary Newtonian mechanics. However, it is not clear whether the expansion of the gas in the cannon is an adiabatic or an isothermal process. We built an air cannon that utilizes a diaphragm valve to release the pressurized gas and found that neither process accurately predicts the exit velocity of our projectile. We discuss a model based on the flow of air through the valve, which is in much better agreement with our data.
Air ejector augmented compressed air energy storage system
Ahrens, F.W.; Kartsounes, G.T.
Energy is stored in slack demand periods by charging a plurality of underground reservoirs with air to the same peak storage pressure, during peak demand periods throttling the air from one storage reservoir into a gas turbine system at a constant inlet pressure until the air presure in the reservoir falls to said constant inlet pressure, thereupon permitting air in a second reservoir to flow into said gas turbine system while drawing air from the first reservoir through a variable geometry air ejector and adjusting said variable geometry air ejector, said air flow being essentially at the constant inlet pressure of the gas turbine system.
Air ejector augmented compressed air energy storage system
Ahrens, Frederick W.; Kartsounes, George T.
1980-01-01
Energy is stored in slack demand periods by charging a plurality of underground reservoirs with air to the same peak storage pressure, during peak demand periods throttling the air from one storage reservoir into a gas turbine system at a constant inlet pressure until the air pressure in the reservoir falls to said constant inlet pressure, thereupon permitting air in a second reservoir to flow into said gas turbine system while drawing air from the first reservoir through a variable geometry air ejector and adjusting said variable geometry air ejector, said air flow being essentially at the constant inlet pressure of the gas turbine system.
Efficiency at Sorting Cards in Compressed Air
Poulton, E. C.; Catton, M. J.; Carpenter, A.
1964-01-01
At a site where compressed air was being used in the construction of a tunnel, 34 men sorted cards twice, once at normal atmospheric pressure and once at 3½, 2½, or 2 atmospheres absolute pressure. An additional six men sorted cards twice at normal atmospheric pressure. When the task was carried out for the first time, all the groups of men performing at raised pressure were found to yield a reliably greater proportion of very slow responses than the group of men performing at normal pressure. There was reliably more variability in timing at 3½ and 2½ atmospheres absolute than at normal pressure. At 3½ atmospheres absolute the average performance was also reliably slower. When the task was carried out for the second time, exposure to 3½ atmospheres absolute pressure had no reliable effect. Thus compressed air affected performance only while the task was being learnt; it had little effect after practice. No reliable differences were found related to age, to length of experience in compressed air, or to the duration of the exposure to compressed air, which was never less than 10 minutes at 3½ atmospheres absolute pressure. PMID:14180485
Compressible turbulent flows: Modeling and similarity considerations
NASA Technical Reports Server (NTRS)
Zeman, Otto
1991-01-01
With the recent revitalization of high speed flow research, compressibility presents a new set of challenging problems to turbulence researchers. Questions arise as to what extent compressibility affects turbulence dynamics, structures, the Reynolds stress-mean velocity (constitutive) relation, and the accompanying processes of heat transfer and mixing. In astrophysical applications, compressible turbulence is believed to play an important role in intergalactic gas cloud dynamics and in accretion disk convection. Understanding and modeling of the compressibility effects in free shear flows, boundary layers, and boundary layer/shock interactions is discussed.
NASA Technical Reports Server (NTRS)
Denery, Dallas G.; Erzberger, Heinz; Edwards, Thomas A. (Technical Monitor)
1998-01-01
The Center TRACON Automation System (CTAS) will be the basis for air traffic planning and control in the terminal area. The system accepts arriving traffic within an extended terminal area and optimizes the flow based on current traffic and airport conditions. The operational use of CTAS will be presented together with results from current operations.
Time accurate simulations of compressible shear flows
NASA Technical Reports Server (NTRS)
Givi, Peyman; Steinberger, Craig J.; Vidoni, Thomas J.; Madnia, Cyrus K.
1993-01-01
The objectives of this research are to employ direct numerical simulation (DNS) to study the phenomenon of mixing (or lack thereof) in compressible free shear flows and to suggest new means of enhancing mixing in such flows. The shear flow configurations under investigation are those of parallel mixing layers and planar jets under both non-reacting and reacting nonpremixed conditions. During the three-years of this research program, several important issues regarding mixing and chemical reactions in compressible shear flows were investigated.
41 CFR 50-204.8 - Use of compressed air.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 41 Public Contracts and Property Management 1 2014-07-01 2014-07-01 false Use of compressed air. 50-204.8 Section 50-204.8 Public Contracts and Property Management Other Provisions Relating to... CONTRACTS General Safety and Health Standards § 50-204.8 Use of compressed air. Compressed air shall not...
41 CFR 50-204.8 - Use of compressed air.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 41 Public Contracts and Property Management 1 2012-07-01 2009-07-01 true Use of compressed air. 50-204.8 Section 50-204.8 Public Contracts and Property Management Other Provisions Relating to Public... General Safety and Health Standards § 50-204.8 Use of compressed air. Compressed air shall not be used...
41 CFR 50-204.8 - Use of compressed air.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 41 Public Contracts and Property Management 1 2013-07-01 2013-07-01 false Use of compressed air. 50-204.8 Section 50-204.8 Public Contracts and Property Management Other Provisions Relating to... CONTRACTS General Safety and Health Standards § 50-204.8 Use of compressed air. Compressed air shall not...
41 CFR 50-204.8 - Use of compressed air.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 41 Public Contracts and Property Management 1 2010-07-01 2010-07-01 true Use of compressed air. 50-204.8 Section 50-204.8 Public Contracts and Property Management Other Provisions Relating to Public... General Safety and Health Standards § 50-204.8 Use of compressed air. Compressed air shall not be used...
PDF approach for compressible turbulent reacting flows
NASA Technical Reports Server (NTRS)
Hsu, A. T.; Tsai, Y.-L. P.; Raju, M. S.
1993-01-01
The objective of the present work is to develop a probability density function (pdf) turbulence model for compressible reacting flows for use with a CFD flow solver. The probability density function of the species mass fraction and enthalpy are obtained by solving a pdf evolution equation using a Monte Carlo scheme. The pdf solution procedure is coupled with a compressible CFD flow solver which provides the velocity and pressure fields. A modeled pdf equation for compressible flows, capable of capturing shock waves and suitable to the present coupling scheme, is proposed and tested. Convergence of the combined finite-volume Monte Carlo solution procedure is discussed, and an averaging procedure is developed to provide smooth Monte-Carlo solutions to ensure convergence. Two supersonic diffusion flames are studied using the proposed pdf model and the results are compared with experimental data; marked improvements over CFD solutions without pdf are observed. Preliminary applications of pdf to 3D flows are also reported.
Seneca Compressed Air Energy Storage (CAES) Project
None, None
2012-11-30
of the designs would perform acceptably. Their general scope of work included development of detailed project construction schedules, capital cost and cash flow estimates for both CAES cycles, and development of detailed operational data, including fuel and compression energy requirements, to support dispatch modeling for the CAES cycles. The Dispatch Modeling Consultant selected for this project was Customized Energy Solutions (CES). Their general scope of work included development of wholesale electric and gas market price forecasts and development of a dispatch model specific to CAES technologies. Parsons Brinkerhoff Energy Storage Services (PBESS) was retained to develop an air storage cavern and well system design for the CAES project. Their general scope of work included development of a cavern design, solution mining plan, and air production well design, cost, and schedule estimates for the project. Detailed Front End Engineering Design (FEED) during Phase 1 of the project determined that CAES plant capital equipment costs were much greater than the $125.6- million originally estimated by EPRI for the project. The initial air storage cavern Design Basis was increased from a single five million cubic foot capacity cavern to three, five million cubic foot caverns with associated air production wells and piping. The result of this change in storage cavern Design Basis increased project capital costs significantly. In addition, the development time required to complete the three cavern system was estimated at approximately six years. This meant that the CAES plant would initially go into service with only one third of the required storage capacity and would not achieve full capability until after approximately five years of commercial operation. The market price forecasting and dispatch modeling completed by CES indicated that the CAES technologies would operate at only 10 to 20% capacity factors and the resulting overall project economics were not favorable for
Comments on compressible flow through butterfly valves
Blakenship, J.G. )
1989-01-01
In the flow analysis of process piping systems, it is desirable to treat control valves in the same way as elbow, reducers, expansions, and other pressure loss elements. In a recently reported research program, the compressible flow characteristics of butterfly valves were investigated. Fisher Controls International, Inc., manufacturer of a wide range of control valves, publishes coefficients that can be used to calculate flow characteristics for the full range of valve movement. This paper describes the use of the manufacturer's data to calculate flow parameters as reported by the researchers who investigated compressible flow through butterfly valves. The manufacturer's data produced consistent results and can be used to predict choked flow and the pressure loss for unchoked flow. 4 refs., 6 figs., 1 tab.
Tunnel Correction for Compressible Subsonic Flow
NASA Technical Reports Server (NTRS)
Baranoff, A. V.
1947-01-01
This report presents a treatment of the effects of the tunnel walls on the flow velocity and direction in a compressible medium at subsonic speed by an approximate method. Calculations are given for the rotationally symmetric and two- dimensionl problems of the flow past bodies, as well for the downwash effect in the tunnel with circular cross section.
Compressible flow in fluidic oscillators
NASA Astrophysics Data System (ADS)
Graff, Emilio; Hirsch, Damian; Gharib, Mory
2013-11-01
We present qualitative observations on the internal flow characteristics of fluidic oscillator geometries commonly referred to as sweeping jets in active flow control applications. We also discuss the effect of the geometry on the output jet in conditions from startup to supersonic exit velocity. Supported by the Boeing Company.
Computational methods for ideal compressible flow
NASA Technical Reports Server (NTRS)
Vanleer, B.
1983-01-01
Conservative dissipative difference schemes for computing one dimensional flow are introduced, and the recognition and representation of flow discontinuities are discussed. Multidimensional methods are outlined. Second order finite volume schemes are introduced. Conversion of difference schemes for a single linear convection equation into schemes for the hyperbolic system of the nonlinear conservation laws of ideal compressible flow is explained. Approximate Riemann solvers are presented. Monotone initial value interpolation; and limiters, switches, and artificial dissipation are considered.
Entropic lattice Boltzmann model for compressible flows.
Frapolli, N; Chikatamarla, S S; Karlin, I V
2015-12-01
We present a lattice Boltzmann model (LBM) that covers the entire range of fluid flows, from low Mach weakly compressible to transonic and supersonic flows. One of the most restrictive limitations of the lattice Boltzmann method, the low Mach number limit, is overcome here by three fundamental changes to the LBM scheme: use of an appropriately chosen multispeed lattice, accurate evaluation of the equilibrium, and the entropic relaxation for the collision. The range of applications is demonstrated through the simulation of a bow shock in front of an airfoil and the simulation of decaying compressible turbulence with shocklets. PMID:26764625
Entropic lattice Boltzmann model for compressible flows
NASA Astrophysics Data System (ADS)
Frapolli, N.; Chikatamarla, S. S.; Karlin, I. V.
2015-12-01
We present a lattice Boltzmann model (LBM) that covers the entire range of fluid flows, from low Mach weakly compressible to transonic and supersonic flows. One of the most restrictive limitations of the lattice Boltzmann method, the low Mach number limit, is overcome here by three fundamental changes to the LBM scheme: use of an appropriately chosen multispeed lattice, accurate evaluation of the equilibrium, and the entropic relaxation for the collision. The range of applications is demonstrated through the simulation of a bow shock in front of an airfoil and the simulation of decaying compressible turbulence with shocklets.
Spectral methods for inviscid, compressible flows
NASA Technical Reports Server (NTRS)
Hussaini, M. Y.; Salas, M. D.; Zang, T. A.
1983-01-01
Report developments in the application of spectral methods to two dimensional compressible flows are reviewed. A brief introduction to spectral methods -- their history and especially their implementation -- is provided. The stress is on those techniques relevant to transonic flow computation. The spectral multigrid iterative methods are discussed with application to the transonic full potential equation. Discontinuous solutions of the Euler equations are considered. The key element is the shock fitting technique which is briefly explained.
Assessment of the market for compressed air services
None, None
2001-01-01
The objective of this report is to provide a comprehensive and balanced view of the market for engineering and consulting services to improve the energy efficiency of plant compressed air systems. The report is intended for use by Compressed Air Challenge and other industrial energy efficiency program operators in developing strategies to encourage the growth of the compressed air system efficiency and enhance the quality of the services it offers.
2010-09-13
GRIDS Project: General Compression has developed a transformative, near-isothermal compressed air energy storage system (GCAES) that prevents air from heating up during compression and cooling down during expansion. When integrated with renewable generation, such as a wind farm, intermittent energy can be stored in compressed air in salt caverns or pressurized tanks. When electricity is needed, the process is reversed and the compressed air is expanded to produce electricity. Unlike conventional compressed air energy storage (CAES) projects, no gas is burned to convert the stored high-pressure air back into electricity. The result of this breakthrough is an ultra-efficient, fully shapeable, 100% renewable and carbon-free power product. The GCAES™ system can provide high quality electricity and ancillary services by effectively integrating renewables onto the grid at a cost that is competitive with gas, coal and nuclear generation.
Seneca Compressed Air Energy Storage (CAES) Project
2012-11-30
This report provides a review and an analysis of potential environmental justice areas that could be affected by the New York State Electric & Gas (NYSEG) compress air energy storage (CAES) project and identifies existing environmental burden conditions on the area and evaluates additional burden of any significant adverse environmental impact. The review assesses the socioeconomic and demographic conditions of the area surrounding the proposed CAES facility in Schuyler County, New York. Schuyler County is one of 62 counties in New York. Schuyler County’s 2010 population of 18,343 makes it one of the least populated counties in the State (U.S. Census Bureau, 2010). This report was prepared for WorleyParsons by ERM and describes the study area investigated, methods and criteria used to evaluate this area, and the findings and conclusions from the evaluation.
Direct simulation of compressible reacting flows
NASA Technical Reports Server (NTRS)
Poinsot, Thierry J.
1989-01-01
A research program for direct numerical simulations of compressible reacting flows is described. Two main research subjects are proposed: the effect of pressure waves on turbulent combustion and the use of direct simulation methods to validate flamelet models for turbulent combustion. The interest of a compressible code to study turbulent combustion is emphasized through examples of reacting shear layer and combustion instabilities studies. The choice of experimental data to compare with direct simulation results is discussed. A tentative program is given and the computation cases to use are described as well as the code validation runs.
78. PIPING CHANNEL FOR FUEL LOADING, FUEL TOPPING, COMPRESSED AIR, ...
78. PIPING CHANNEL FOR FUEL LOADING, FUEL TOPPING, COMPRESSED AIR, GASEOUS NITROGEN, AND HELIUM - Vandenberg Air Force Base, Space Launch Complex 3, Launch Pad 3 East, Napa & Alden Roads, Lompoc, Santa Barbara County, CA
6. DETAIL OF HIGHPRESSURE COMPRESSED AIR HOSE IN SOUTHWEST CORNER ...
6. DETAIL OF HIGH-PRESSURE COMPRESSED AIR HOSE IN SOUTHWEST CORNER OF SHIPPING AND RECEIVING ROOM (109) - Vandenberg Air Force Base, Space Launch Complex 3, Vehicle Support Building, Napa & Alden Roads, Lompoc, Santa Barbara County, CA
Elimination of microorganisms from dental operatory compressed air.
De Ciccio, A; Chan, E C
1998-01-01
Compressed air is used to power high-speed handpieces, as well as to dry and clean surfaces in the oral cavity during patient treatment, in all dental operatories. The compressed air used in the dental operatories located in large institutions such as universities or hospitals is generally obtained from a central source, and is produced by continually running compressors. In operatories located in private practice settings, compressed air is obtained from small on-site air compressors, which may be run less frequently. A survey was made of operatories in the Montreal area to determine the microbial load of the compressed air produced by air compressors. An air sampler was used to collect compressed air and impinge it on a rotating agar medium surface. Compared to the air produced from compressors in constant use, the air collected from compressors that ran intermittently had a very high microbial load. The efficacy of an apparatus designed to sterilize the contaminated air produced by small, on-site compressors was tested. Called a Purilair, this device heats every particle of inflowing compressed air to 250 degrees C and then forces it through a fine-pore ceramic filter. In three private practice operatories, an in-line Purilair effectively sterilized the air being delivered by small compressors. The same result was obtained in the laboratory when lyophilized spores and cells of Bacillus stearothermophilus and conidia of Penicillium notatum and Aspergillus niger were sprayed into the intake line of the apparatus. PMID:9473876
Preliminary Investigation of an Underwater Ramjet Powered by Compressed Air
NASA Technical Reports Server (NTRS)
Mottard, Elmo J.; Shoemaker, Charles J.
1961-01-01
Part I contains the results of a preliminary experimental investigation of a particular design of an underwater ramjet or hydroduct powered by compressed air. The hydroduct is a propulsion device in which the energy of an expanding gas imparts additional momentum to a stream of water through mixing. The hydroduct model had a fineness ratio of 5.9, a maximum diameter of 3.2 inches, and a ratio of inlet area to frontal area of 0.32. The model was towed at a depth of 1 inch at forward speeds between 20 and 60 feet per second for airflow rates from 0.1 to 0.3 pound per second. Longitudinal force and pressures at the inlet and in the mixing chamber were determined. The hydroduct produced a positive thrust-minus-drag force at every test speed. The force and pressure coefficients were functions primarily of the ratio of weight airflow to free-stream velocity. The maximum propulsive efficiency based on the net internal thrust and an isothermal expansion of the air was approximately 53 percent at a thrust coefficient of 0.10. The performance of the test model may have been influenced by choking of the exit flow. Part II is a theoretical development of an underwater ramjet using air as "fuel." The basic assumption of the theoretical analysis is that a mixture of water and air can be treated as a compressible gas. More information on the properties of air-water mixtures is required to confirm this assumption or to suggest another approach. A method is suggested from which a more complete theoretical development, with the effects of choking included, may be obtained. An exploratory computation, in which this suggested method was used, indicated that the effect of choked flow on the thrust coefficient was minor.
Working characteristics of variable intake valve in compressed air engine.
Yu, Qihui; Shi, Yan; Cai, Maolin
2014-01-01
A new camless compressed air engine is proposed, which can make the compressed air energy reasonably distributed. Through analysis of the camless compressed air engine, a mathematical model of the working processes was set up. Using the software MATLAB/Simulink for simulation, the pressure, temperature, and air mass of the cylinder were obtained. In order to verify the accuracy of the mathematical model, the experiments were conducted. Moreover, performance analysis was introduced to design compressed air engine. Results show that, firstly, the simulation results have good consistency with the experimental results. Secondly, under different intake pressures, the highest output power is obtained when the crank speed reaches 500 rpm, which also provides the maximum output torque. Finally, higher energy utilization efficiency can be obtained at the lower speed, intake pressure, and valve duration angle. This research can refer to the design of the camless valve of compressed air engine. PMID:25379536
Working Characteristics of Variable Intake Valve in Compressed Air Engine
Yu, Qihui; Shi, Yan; Cai, Maolin
2014-01-01
A new camless compressed air engine is proposed, which can make the compressed air energy reasonably distributed. Through analysis of the camless compressed air engine, a mathematical model of the working processes was set up. Using the software MATLAB/Simulink for simulation, the pressure, temperature, and air mass of the cylinder were obtained. In order to verify the accuracy of the mathematical model, the experiments were conducted. Moreover, performance analysis was introduced to design compressed air engine. Results show that, firstly, the simulation results have good consistency with the experimental results. Secondly, under different intake pressures, the highest output power is obtained when the crank speed reaches 500 rpm, which also provides the maximum output torque. Finally, higher energy utilization efficiency can be obtained at the lower speed, intake pressure, and valve duration angle. This research can refer to the design of the camless valve of compressed air engine. PMID:25379536
From sideward flow to nuclear compressibility
Pan, Q.; Danielewicz, P.
1993-04-01
The authors use the transport model (BUU) with different optical potentials, combining density and momentum dependence with strong or weak nuclear compressibility, to simulate heavy-ion collisions. Experiment by DIOGENE allows them to show that experimental sideward flow is close to their calculations using optical potential of soft momentum- and density-dependence (Potential I), as well as calculations using optical potential of stiff pure density-dependence (Potential II). On the other hand, the Plastic Ball experiment on sideward flow, mainly due to the instrumental rejection of low transverse momentum particles, allows the authors to tell the differences between Potential I and II, with calculations using Potential I being close to the experimental data. Combining the results above, they see that only potential I with soft nuclear compressibility can describe the experimental data. The uncertainty of NN cross section in the medium leads to the uncertainty in nuclear compressibility, they estimate that the nuclear compressibility K lies between 180 and 235 MeV.
30 CFR 77.411 - Compressed air and boilers; general.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Compressed air and boilers; general. 77.411... COAL MINES Safeguards for Mechanical Equipment § 77.411 Compressed air and boilers; general. All boilers and pressure vessels shall be constructed, installed, and maintained in accordance with...
30 CFR 77.411 - Compressed air and boilers; general.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Compressed air and boilers; general. 77.411... COAL MINES Safeguards for Mechanical Equipment § 77.411 Compressed air and boilers; general. All boilers and pressure vessels shall be constructed, installed, and maintained in accordance with...
30 CFR 77.411 - Compressed air and boilers; general.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Compressed air and boilers; general. 77.411... COAL MINES Safeguards for Mechanical Equipment § 77.411 Compressed air and boilers; general. All boilers and pressure vessels shall be constructed, installed, and maintained in accordance with...
30 CFR 77.411 - Compressed air and boilers; general.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Compressed air and boilers; general. 77.411... COAL MINES Safeguards for Mechanical Equipment § 77.411 Compressed air and boilers; general. All boilers and pressure vessels shall be constructed, installed, and maintained in accordance with...
30 CFR 77.411 - Compressed air and boilers; general.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Compressed air and boilers; general. 77.411... COAL MINES Safeguards for Mechanical Equipment § 77.411 Compressed air and boilers; general. All boilers and pressure vessels shall be constructed, installed, and maintained in accordance with...
Modeling Compressibility Effects in High-Speed Turbulent Flows
NASA Technical Reports Server (NTRS)
Sarkar, S.
2004-01-01
Man has strived to make objects fly faster, first from subsonic to supersonic and then to hypersonic speeds. Spacecraft and high-speed missiles routinely fly at hypersonic Mach numbers, M greater than 5. In defense applications, aircraft reach hypersonic speeds at high altitude and so may civilian aircraft in the future. Hypersonic flight, while presenting opportunities, has formidable challenges that have spurred vigorous research and development, mainly by NASA and the Air Force in the USA. Although NASP, the premier hypersonic concept of the eighties and early nineties, did not lead to flight demonstration, much basic research and technology development was possible. There is renewed interest in supersonic and hypersonic flight with the HyTech program of the Air Force and the Hyper-X program at NASA being examples of current thrusts in the field. At high-subsonic to supersonic speeds, fluid compressibility becomes increasingly important in the turbulent boundary layers and shear layers associated with the flow around aerospace vehicles. Changes in thermodynamic variables: density, temperature and pressure, interact strongly with the underlying vortical, turbulent flow. The ensuing changes to the flow may be qualitative such as shocks which have no incompressible counterpart, or quantitative such as the reduction of skin friction with Mach number, large heat transfer rates due to viscous heating, and the dramatic reduction of fuel/oxidant mixing at high convective Mach number. The peculiarities of compressible turbulence, so-called compressibility effects, have been reviewed by Fernholz and Finley. Predictions of aerodynamic performance in high-speed applications require accurate computational modeling of these "compressibility effects" on turbulence. During the course of the project we have made fundamental advances in modeling the pressure-strain correlation and developed a code to evaluate alternate turbulence models in the compressible shear layer.
Elliptical instability of compressible flow in ellipsoids
NASA Astrophysics Data System (ADS)
Clausen, N.; Tilgner, A.
2014-02-01
Context. Elliptical instability is due to a parametric resonance of two inertial modes in a fluid velocity field with elliptical streamlines. This flow is a simple model of the motion in a tidally deformed, rotating body. Elliptical instability typically leads to three-dimensional turbulence. The associated turbulent dissipation together with the dissipation of the large scale mode may be important for the synchronization process in stellar and planetary binary systems. Aims: In order to determine the influence of the compressibility on the stability limits of tidal flows in stars or planets, we calculate the growth rates of perturbations in flows with elliptical streamlines within ellipsoidal boundaries of small ellipticity. In addition, the influence of the orbiting frequency of the tidal perturber ΩP and the viscosity of the fluid are taken into account. Methods: We studied the linear stability of the flow to determine the growth rates. We solved the Euler equation and the continuity equation. The viscosity was introduced heuristically in our calculations. We assumed a power law for the radial dependence of the background density. Together with the use of the anelastic approximation, this enabled us to use semi-analytical methods to solve the equations. Results: It is found that the growth rate of a certain mode combination depends on the compressibility. However, the influence of the compressibility is negligible for the growth rate maximized over all possible modes if viscous bulk damping effects can be neglected. The growth rate maximized over all possible modes determines the stability of the flow. The stability limit for the compressible fluid confined to an ellipsoid is the same as for incompressible fluid in an unbounded domain. Depending on the ratio ΩP/ΩF, with ΩF the spin rate of the central object in the frame of the rotating tidal perturber, certain pairs of modes resonate with each other. The size of the bulk damping term depends on the modes
Hollow vortices in weakly compressible flows
NASA Astrophysics Data System (ADS)
Krishnamurthy, Vikas; Crowdy, Darren
2014-11-01
In a two-dimensional, inviscid and steady fluid flow, hollow vortices are bounded regions of constant pressure with non-zero circulation. It is known that for an infinite row of incompressible hollow vortices, analytical solutions for the flow field and the shape of the hollow vortex boundary can be obtained using conformal mapping methods. In this talk, we show how to derive analytical expressions for a weakly compressible hollow vortex row. This is done by introducing a new method based on the Imai-Lamla formula. We will also touch upon how to extend these results to a von-Karman street of hollow vortices.
Hollow vortices in weakly compressible flows
NASA Astrophysics Data System (ADS)
Krishnamurthy, Vikas; Crowdy, Darren
2015-11-01
In a two-dimensional, inviscid and steady fluid flow, hollow vortices are bounded regions of constant pressure with non-zero circulation. It is known that for an infinite row of incompressible hollow vortices, analytical solutions for the flow field and the shape of the hollow vortex boundary can be obtained using conformal mapping methods. In this talk, we show how to derive analytical expressions for a weakly compressible hollow vortex row. This is done by introducing a new method based on the Imai-Lamla formula. We will also touch upon how to extend these results to a von-Karman street of hollow vortices.
Multidomain approach for calculating compressible flows
NASA Technical Reports Server (NTRS)
Cambier, L.; Chazzi, W.; Veuillot, J. P.; Viviand, H.
1982-01-01
A multidomain approach for calculating compressible flows by using unsteady or pseudo-unsteady methods is presented. This approach is based on a general technique of connecting together two domains in which hyperbolic systems (that may differ) are solved with the aid of compatibility relations associated with these systems. Some examples of this approach's application to calculating transonic flows in ideal fluids are shown, particularly the adjustment of shock waves. The approach is then applied to treating a shock/boundary layer interaction problem in a transonic channel.
Energy storage by compressed air. [using windpowered pumps
NASA Technical Reports Server (NTRS)
Szego, G. C.
1973-01-01
The feasibility of windpower energy storage by compressed air is considered. The system is comprised of a compressor, a motor, and a pump turbine to store air in caverns or aquifiers. It is proposed that storage of several days worth of compressed air up to 650 pounds per square inch can be used to push the aquifier up closer to the container dome and thus initiate piston action by simply compressing air more and more. More energy can be put into it by pressure increase or pushing back the water in the aquifier. This storage system concept has reheat flexibility and lowest cost effectiveness.
Bi-global Stability Analysis of Compressible Open Cavity Flows
NASA Astrophysics Data System (ADS)
Sun, Yiyang; Taira, Kunihiko; Cattafesta, Louis; Ukeiley, Lawrence
2015-11-01
The effect of compressibility on stability characteristics of rectangular open cavity flows is numerically examined. In our earlier work with two-dimensional direct numerical simulation of open cavity flows, we found that increasing Mach number destabilizes the flow in the subsonic regime but stabilizes the flow in the transonic regime. To further examine the compressibility effect, linear bi-global stability analysis is performed over the same range of Mach numbers to investigate the influence of three-dimensional instabilities in flows over open cavities with length-to-depth ratios of 2 and 6. We identify dominant eigenmodes for varied Mach numbers and spanwise wavelengths with respect to two-dimensional stable and unstable steady states. Over a range of spanwise wavelengths, we reveal the growth/damp rates and frequencies of the dominant global modes. Based on the insights from the present analysis, we compare our findings from global stability analysis with our companion three-dimensional flow control experiments aimed at reducing pressure fluctuation caused by cavity flow unsteadiness. This work was supported by the US Air Force Office of Scientific Research (Grant FA9550-13-1-0091).
NASA Technical Reports Server (NTRS)
Hartfield, Roy J., Jr.; Abbitt, John D., III; Mcdaniel, James C.
1989-01-01
A technique is described for imaging the injectant mole-fraction distribution in nonreacting compressible mixing flow fields. Planar fluorescence from iodine, seeded into air, is induced by a broadband argon-ion laser and collected using an intensified charge-injection-device array camera. The technique eliminates the thermodynamic dependence of the iodine fluorescence in the compressible flow field by taking the ratio of two images collected with identical thermodynamic flow conditions but different iodine seeding conditions.
Theoretical and computational dynamics of a compressible flow
NASA Technical Reports Server (NTRS)
Pai, Shih-I; Luo, Shijun
1991-01-01
An introduction to the theoretical and computational fluid dynamics of a compressible fluid is presented. The general topics addressed include: thermodynamics and physical properties of compressible fluids; 1D flow of an inviscid compressible fluid; shock waves; fundamental equations of the dynamics of a compressible inviscid non-heat-conducting and radiating fluid, method of small perturbations, linearized theory; 2D subsonic steady potential flow; hodograph and rheograph methods, exact solutions of 2D insentropic steady flow equations, 2D steady transonic and hypersonic flows, method of characteristics, linearized theory of 3D potential flow, nonlinear theory of 3D compressibe flow, anisentropic (rotational) flow of inviscid compressible fluid, electromagnetogasdynamics, multiphase flows, flows of a compressible fluid with transport phenomena.
Compressibility effects on flow friction in a fully developed pipe flow
NASA Technical Reports Server (NTRS)
Murthy, Sreedhara V.; Gee, Ken; Steinle, Frank W.
1988-01-01
A method was evolved to account for the effects of compressibility in flows through long circular pipes of uniform diameter. Velocity and density variations across the flow cross section were approximated by profile shapes recommended for a flow past flat plates. The wall of the pipe was assumed to have attained an adiabatic condition. An integral method was used to obtain solutions for the governing equations of flow. The method was then used to analyze the detailed pressure measurements made in a long pipe for flow of air at different flow rate settings. Flow friction values derived from these pressure measurements were compared with the standard incompressible pipe flow data available in existing literature.
Schwarz-Based Algorithms for Compressible Flows
NASA Technical Reports Server (NTRS)
Tidriri, M. D.
1996-01-01
We investigate in this paper the application of Schwarz-based algorithms to compressible flows. First we study the combination of these methods with defect-correction procedures. We then study the effect on the Schwarz-based methods of replacing the explicit treatment of the boundary conditions by an implicit one. In the last part of this paper we study the combination of these methods with Newton-Krylov matrix-free methods. Numerical experiments that show the performance of our approaches are then presented.
Unstructured grid methods for compressible flows
NASA Technical Reports Server (NTRS)
Morgan, K.; Peraire, J.; Peiro, J.
1992-01-01
The implementation of the finite element method on unstructured triangular grids is described and the development of centered finite element schemes for the solution of the compressible Euler equation on general triangular and tetrahedral grids is discussed. Explicit and implicit Lax-Wendroff type methods and a method based upon the use of explicit multistep timestepping are considered. In the latter case, the convergence behavior of the method is accelerated by the incorporation of a fully unstructured multigrid procedure. The advancing front method for generating unstructured grids of triangles and tetrahedra is described and the application of adaptive mesh techniques to both steady and transient flow analysis is illustrated.
Lagrangian computation of inviscid compressible flows
NASA Technical Reports Server (NTRS)
Klopfer, G. H.
1978-01-01
A Lagrangian method is developed to solve the Euler equations of gas dynamics. The solution of the equations is obtained by a numerical computation with the well-known Flux-Corrected-Transport (FCT) numerical method. This procedure is modified so that the boundary treatment is accurate and relatively simple. Shock waves and other flow discontinuities are captured monotonically without any type of fitting procedures. The Lagrangian method is employed so that the problem of mesh generation is completely avoided. The method is applicable to all Mach numbers except the low subsonic range where compressibility effects are small. The method is applied to a one-dimensional Riemann problem (shock tube) and to a two-dimensional supersonic channel flow with reflecting shock waves.
Finite scale equations for compressible fluid flow
Margolin, Len G
2008-01-01
Finite-scale equations (FSE) describe the evolution of finite volumes of fluid over time. We discuss the FSE for a one-dimensional compressible fluid, whose every point is governed by the Navier-Stokes equations. The FSE contain new momentum and internal energy transport terms. These are similar to terms added in numerical simulation for high-speed flows (e.g. artificial viscosity) and for turbulent flows (e.g. subgrid scale models). These similarities suggest that the FSE may provide new insight as a basis for computational fluid dynamics. Our analysis of the FS continuity equation leads to a physical interpretation of the new transport terms, and indicates the need to carefully distinguish between volume-averaged and mass-averaged velocities in numerical simulation. We make preliminary connections to the other recent work reformulating Navier-Stokes equations.
Computation of Thermally Perfect Compressible Flow Properties
NASA Technical Reports Server (NTRS)
Witte, David W.; Tatum, Kenneth E.; Williams, S. Blake
1996-01-01
A set of compressible flow relations for a thermally perfect, calorically imperfect gas are derived for a value of c(sub p) (specific heat at constant pressure) expressed as a polynomial function of temperature and developed into a computer program, referred to as the Thermally Perfect Gas (TPG) code. The code is available free from the NASA Langley Software Server at URL http://www.larc.nasa.gov/LSS. The code produces tables of compressible flow properties similar to those found in NACA Report 1135. Unlike the NACA Report 1135 tables which are valid only in the calorically perfect temperature regime the TPG code results are also valid in the thermally perfect, calorically imperfect temperature regime, giving the TPG code a considerably larger range of temperature application. Accuracy of the TPG code in the calorically perfect and in the thermally perfect, calorically imperfect temperature regimes are verified by comparisons with the methods of NACA Report 1135. The advantages of the TPG code compared to the thermally perfect, calorically imperfect method of NACA Report 1135 are its applicability to any type of gas (monatomic, diatomic, triatomic, or polyatomic) or any specified mixture of gases, ease-of-use, and tabulated results.
Schwarz-based algorithms for compressible flows
Tidriri, M.D.
1996-12-31
To compute steady compressible flows one often uses an implicit discretization approach which leads to a large sparse linear system that must be solved at each time step. In the derivation of this system one often uses a defect-correction procedure, in which the left-hand side of the system is discretized with a lower order approximation than that used for the right-hand side. This is due to storage considerations and computational complexity, and also to the fact that the resulting lower order matrix is better conditioned than the higher order matrix. The resulting schemes are only moderately implicit. In the case of structured, body-fitted grids, the linear system can easily be solved using approximate factorization (AF), which is among the most widely used methods for such grids. However, for unstructured grids, such techniques are no longer valid, and the system is solved using direct or iterative techniques. Because of the prohibitive computational costs and large memory requirements for the solution of compressible flows, iterative methods are preferred. In these defect-correction methods, which are implemented in most CFD computer codes, the mismatch in the right and left hand side operators, together with explicit treatment of the boundary conditions, lead to a severely limited CFL number, which results in a slow convergence to steady state aerodynamic solutions. Many authors have tried to replace explicit boundary conditions with implicit ones. Although they clearly demonstrate that high CFL numbers are possible, the reduction in CPU time is not clear cut.
Acceptance Test Report for 241-U compressed air system
Freeman, R.D.
1994-10-20
This Acceptance Test Report (ATR) documents the results of acceptance testing of a newly upgraded compressed air system at 241-U Farm. The system was installed and the test successfully performed under work package 2W-92-01027.
Improving Compressed Air System Performance: A Sourcebook for Industry
2003-11-01
NREL will produce this sourcebook for DOE's Industrial Technologies Office as part of a series of documents on industrial energy equipment. The sourcebook is a reference for industrial compressed air system users, outlining opportunities to improve system efficiency.
Investigation on wind energy-compressed air power system.
Jia, Guang-Zheng; Wang, Xuan-Yin; Wu, Gen-Mao
2004-03-01
Wind energy is a pollution free and renewable resource widely distributed over China. Aimed at protecting the environment and enlarging application of wind energy, a new approach to application of wind energy by using compressed air power to some extent instead of electricity put forward. This includes: explaining the working principles and characteristics of the wind energy-compressed air power system; discussing the compatibility of wind energy and compressor capacity; presenting the theoretical model and computational simulation of the system. The obtained compressor capacity vs wind power relationship in certain wind velocity range can be helpful in the designing of the wind power-compressed air system. Results of investigations on the application of high-pressure compressed air for pressure reduction led to conclusion that pressure reduction with expander is better than the throttle regulator in energy saving. PMID:14727304
Economic and environmental evaluation of compressed-air cars
NASA Astrophysics Data System (ADS)
Creutzig, Felix; Papson, Andrew; Schipper, Lee; Kammen, Daniel M.
2009-10-01
Climate change and energy security require a reduction in travel demand, a modal shift, and technological innovation in the transport sector. Through a series of press releases and demonstrations, a car using energy stored in compressed air produced by a compressor has been suggested as an environmentally friendly vehicle of the future. We analyze the thermodynamic efficiency of a compressed-air car powered by a pneumatic engine and consider the merits of compressed air versus chemical storage of potential energy. Even under highly optimistic assumptions the compressed-air car is significantly less efficient than a battery electric vehicle and produces more greenhouse gas emissions than a conventional gas-powered car with a coal intensive power mix. However, a pneumatic-combustion hybrid is technologically feasible, inexpensive and could eventually compete with hybrid electric vehicles.
NASA Technical Reports Server (NTRS)
Orlin, W James; Lindner, Norman J; Butterly, Jack G
1947-01-01
The theory of the hydraulic analogy -- that is, the analogy between water flow with a free surface and two-dimensional compressible gas flow -- and the limitations and conditions of the analogy are discussed. A test was run using the hydraulic analogy as applied to the flow about circular cylinders of various diameters at subsonic velocities extending into the supercritical range. The apparatus and techniques used in this application are described and criticized. Reasonably satisfactory agreement of pressure distributions and flow fields existed between water and air flow about corresponding bodies. This agreement indicated the possibility of extending experimental compressibility research by new methods.
Design optimization of natural laminar flow bodies in compressible flow
NASA Technical Reports Server (NTRS)
Dodbele, Simha S.
1992-01-01
An optimization method has been developed to design axisymmetric body shapes such as fuselages, nacelles, and external fuel tanks with increased transition Reynolds numbers in subsonic compressible flow. The new design method involves a constraint minimization procedure coupled with analysis of the inviscid and viscous flow regions and linear stability analysis of the compressible boundary-layer. In order to reduce the computer time, Granville's transition criterion is used to predict boundary-layer transition and to calculate the gradients of the objective function, and linear stability theory coupled with the e(exp n)-method is used to calculate the objective function at the end of each design iteration. Use of a method to design an axisymmetric body with extensive natural laminar flow is illustrated through the design of a tiptank of a business jet. For the original tiptank, boundary layer transition is predicted to occur at a transition Reynolds number of 6.04 x 10(exp 6). For the designed body shape, a transition Reynolds number of 7.22 x 10(exp 6) is predicted using compressible linear stability theory coupled with the e(exp n)-method.
Characteristics of compressible flow of supercritical kerosene
NASA Astrophysics Data System (ADS)
Zhong, Feng-Quan; Fan, Xue-Jun; Wang, Jing; Yu, Gong; Li, Jian-Guo
2012-02-01
In this paper, compressible flow of aviation kerosene at supercritical conditions has been studied both numerically and experimentally. The thermophysical properties of supercritical kerosene are calculated using a 10-species surrogate based on the principle of extended corresponding states (ECS). Isentropic acceleration of supercritical kerosene to subsonic and supersonic speeds has been analyzed numerically. It has been found that the isentropic relationships of supercritical kerosene are significantly different from those of ideal gases. A two-stage fuel heating and delivery system is used to heat the kerosene up to a temperature of 820K and pressure of 5.5MPa with a maximum mass flow rate of 100 g/s. The characteristics of supercritical kerosene flows in a converging-diverging nozzle (Laval nozzle) have been studied experimentally. The results show that stable supersonic flows of kerosene could be established in the temperature range of 730 K-820K and the measurements in the wall pressure agree with the numerical calculation.
Natural Flow Air Cooled Photovoltaics
NASA Astrophysics Data System (ADS)
Tanagnostopoulos, Y.; Themelis, P.
2010-01-01
Our experimental study aims to investigate the improvement in the electrical performance of a photovoltaic installation on buildings through cooling of the photovoltaic panels with natural air flow. Our experimental study aims to investigate the improvement in the electrical performance of a photovoltaic installation on buildings through cooling of the photovoltaic panels with natural air flow. We performed experiments using a prototype based on three silicon photovoltaic modules placed in series to simulate a typical sloping building roof with photovoltaic installation. In this system the air flows through a channel on the rear side of PV panels. The potential for increasing the heat exchange from the photovoltaic panel to the circulating air by the addition of a thin metal sheet (TMS) in the middle of air channel or metal fins (FIN) along the air duct was examined. The operation of the device was studied with the air duct closed tightly to avoid air circulation (CLOSED) and the air duct open (REF), with the thin metal sheet (TMS) and with metal fins (FIN). In each case the experiments were performed under sunlight and the operating parameters of the experimental device determining the electrical and thermal performance of the system were observed and recorded during a whole day and for several days. We collected the data and form PV panels from the comparative diagrams of the experimental results regarding the temperature of solar cells, the electrical efficiency of the installation, the temperature of the back wall of the air duct and the temperature difference in the entrance and exit of the air duct. The comparative results from the measurements determine the improvement in electrical performance of the photovoltaic cells because of the reduction of their temperature, which is achieved by the naturally circulating air.
Chang, Chih-Hao . E-mail: chchang@engineering.ucsb.edu; Liou, Meng-Sing . E-mail: meng-sing.liou@grc.nasa.gov
2007-07-01
In this paper, we propose a new approach to compute compressible multifluid equations. Firstly, a single-pressure compressible multifluid model based on the stratified flow model is proposed. The stratified flow model, which defines different fluids in separated regions, is shown to be amenable to the finite volume method. We can apply the conservation law to each subregion and obtain a set of balance equations. Secondly, the AUSM{sup +} scheme, which is originally designed for the compressible gas flow, is extended to solve compressible liquid flows. By introducing additional dissipation terms into the numerical flux, the new scheme, called AUSM{sup +}-up, can be applied to both liquid and gas flows. Thirdly, the contribution to the numerical flux due to interactions between different phases is taken into account and solved by the exact Riemann solver. We will show that the proposed approach yields an accurate and robust method for computing compressible multiphase flows involving discontinuities, such as shock waves and fluid interfaces. Several one-dimensional test problems are used to demonstrate the capability of our method, including the Ransom's water faucet problem and the air-water shock tube problem. Finally, several two dimensional problems will show the capability to capture enormous details and complicated wave patterns in flows having large disparities in the fluid density and velocities, such as interactions between water shock wave and air bubble, between air shock wave and water column(s), and underwater explosion.
Subsampling-based compression and flow visualization
NASA Astrophysics Data System (ADS)
Agranovsky, Alexy; Camp, David; Joy, Kenneth I.; Childs, Hank
2015-01-01
As computational capabilities increasingly outpace disk speeds on leading supercomputers, scientists will, in turn, be increasingly unable to save their simulation data at its native resolution. One solution to this problem is to compress these data sets as they are generated and visualize the compressed results afterwards. We explore this approach, specifically subsampling velocity data and the resulting errors for particle advection-based flow visualization. We compare three techniques: random selection of subsamples, selection at regular locations corresponding to multi-resolution reduction, and introduce a novel technique for informed selection of subsamples. Furthermore, we explore an adaptive system which exchanges the subsampling budget over parallel tasks, to ensure that subsampling occurs at the highest rate in the areas that need it most. We perform supercomputing runs to measure the effectiveness of the selection and adaptation techniques. Overall, we find that adaptation is very effective, and, among selection techniques, our informed selection provides the most accurate results, followed by the multi-resolution selection, and with the worst accuracy coming from random subsamples.
46 CFR 112.50-7 - Compressed air starting.
Code of Federal Regulations, 2011 CFR
2011-10-01
... AND POWER SYSTEMS Emergency Diesel and Gas Turbine Engine Driven Generator Sets § 112.50-7 Compressed..., and energy storing devices must be in the emergency generator room, except for the main or auxiliary... emergency generator room and a handcranked, diesel-powered air compressor for recharging the air...
46 CFR 112.50-7 - Compressed air starting.
Code of Federal Regulations, 2014 CFR
2014-10-01
... AND POWER SYSTEMS Emergency Diesel and Gas Turbine Engine Driven Generator Sets § 112.50-7 Compressed..., and energy storing devices must be in the emergency generator room, except for the main or auxiliary... emergency generator room and a handcranked, diesel-powered air compressor for recharging the air...
46 CFR 112.50-7 - Compressed air starting.
Code of Federal Regulations, 2013 CFR
2013-10-01
... AND POWER SYSTEMS Emergency Diesel and Gas Turbine Engine Driven Generator Sets § 112.50-7 Compressed..., and energy storing devices must be in the emergency generator room, except for the main or auxiliary... emergency generator room and a handcranked, diesel-powered air compressor for recharging the air...
46 CFR 112.50-7 - Compressed air starting.
Code of Federal Regulations, 2012 CFR
2012-10-01
... AND POWER SYSTEMS Emergency Diesel and Gas Turbine Engine Driven Generator Sets § 112.50-7 Compressed..., and energy storing devices must be in the emergency generator room, except for the main or auxiliary... emergency generator room and a handcranked, diesel-powered air compressor for recharging the air...
Summary of selected compressed air energy storage studies
Allen, R.D.; Doherty, T.J.; Kannberg, L.D.
1985-01-01
A descriptive summarily of research and development in compressed air energy storage technology is presented. Research funded primarily by the Department of Energy is described. Results of studies by other groups and experience at the Huntorf plant in West Germany are included. Feasibility studies performed by General Electric are summarized. The feasibility of air storage in dissolved salt cavities is also demonstrated. (BCS)
Atopy, airway reactivity and compressed air diving in males.
Tetzlaff, K; Neubauer, B; Reuter, M; Friege, L
1998-01-01
A decline in expiratory flow rates in divers has recently been attributed to chronic exposure to hyberbaric air. Airway hyperresponsiveness (AHR) to stimuli due to a hyperbaric environment may play a certain role in this context. The aim of this study was to determine the prevalence of AHR in compressed air divers and to assess the value of bronchial challenges for prediction of fitness to dive. A cross-sectional sample of 59 healthy male volunteers--28 divers and 31 diving candidates (controls)--who had been found fit to dive in a diving medical examination underwent additional allergy screening (skin prick and serum IgE) and a histamine bronchial challenge. Pre- and postchallenge body plethysmography was completed to assess AHR. AHR to histamine was significantly increased among divers and positively related to diving experience whereas divers and controls did not differ significantly with respect to age, anthropometric data, current smoking habits, skin prick reaction, and elevated serum IgE. Our results indicate an increased prevalence of AHR to nonspecific inhalation stimuli in experienced divers. Bronchial challenge tests may be helpful to detect asthmatics in the medical assessment of fitness to dive and for follow-up examinations during a diver's career. PMID:9730792
Planar temperature measurement in compressible flows using laser-induced iodine fluorescence
NASA Technical Reports Server (NTRS)
Hartfield, Roy J., Jr.; Hollo, Steven D.; Mcdaniel, James C.
1991-01-01
A laser-induced iodine fluorescence technique that is suitable for the planar measurement of temperature in cold nonreacting compressible air flows is investigated analytically and demonstrated in a known flow field. The technique is based on the temperature dependence of the broadband fluorescence from iodine excited by the 514-nm line of an argon-ion laser. Temperatures ranging from 165 to 245 K were measured in the calibration flow field. This technique makes complete, spatially resolved surveys of temperature practical in highly three-dimensional, low-temperature compressible flows.
NASA Astrophysics Data System (ADS)
Torizumi, Y.; Hirayama, N.; Maeda, T.
1983-01-01
Flow characteristics of a compressible gas flow through an orifice are investigated experimentally at pressure ratios below the regulation values of JIS and ASME. For practical mass flow measurements, a theoretical method of mass flow estimations is extended using one-dimensional flow theory and experimental data. Using the method, the accuracy of mass flow measurements with orifice meters is about + or 1% in the Reynolds number range of turbulent flows and also in supercritical flows. Tables of the product of flow coefficient and expansion factor are obtained by the method at various diameter ratios, pressure ratios, and specific heats.
Compressed Air System Optimization: Case Study Food Industry in Indonesia
NASA Astrophysics Data System (ADS)
Widayati, Endang; Nuzahar, Hasril
2016-01-01
Compressors and compressed air systems was one of the most important utilities in industries or factories. Approximately 10% of the cost of electricity in the industry was used to produce compressed air. Therefore the potential for energy savings in the compressors and compressed air systems had a big challenge. This field was conducted especially in Indonesia food industry or factory. Compressed air system optimization was a technique approach to determine the optimal conditions for the operation of compressors and compressed air systems that included evaluation of the energy needs, supply adjustment, eliminating or reconfiguring the use and operation of inefficient, changing and complementing some equipment and improving operating efficiencies. This technique gave the significant impact for energy saving and costs. The potential savings based on this study through measurement and optimization e.g. system that lowers the pressure of 7.5 barg to 6.8 barg would reduce energy consumption and running costs approximately 4.2%, switch off the compressor GA110 and GA75 was obtained annual savings of USD 52,947 ≈ 455 714 kWh, running GA75 light load or unloaded then obtained annual savings of USD 31,841≈ 270,685 kWh, install new compressor 2x132 kW and 1x 132 kW VSD obtained annual savings of USD 108,325≈ 928,500 kWh. Furthermore it was needed to conduct study of technical aspect of energy saving potential (Investment Grade Audit) and performed Cost Benefit Analysis. This study was one of best practice solutions how to save energy and improve energy performance in compressors and compressed air system.
Compressible flow computer program for gas film seals
NASA Technical Reports Server (NTRS)
Zuk, J.; Smith, P. J.
1975-01-01
Computer program, AREAX, calculates properties of compressible fluid flow with friction and area change. Program carries out quasi-one-dimensional flow analysis which is valid for laminar and turbulent flows under both subsonic and choked flow conditions. Program was written to be applied to gas film seals.
Low-Reynolds number compressible flow around a triangular airfoil
NASA Astrophysics Data System (ADS)
Munday, Phillip; Taira, Kunihiko; Suwa, Tetsuya; Numata, Daiju; Asai, Keisuke
2013-11-01
We report on the combined numerical and experimental effort to analyze the nonlinear aerodynamics of a triangular airfoil in low-Reynolds number compressible flow that is representative of wings on future Martian air vehicles. The flow field around this airfoil is examined for a wide range of angles of attack and Mach numbers with three-dimensional direct numerical simulations at Re = 3000 . Companion experiments are conducted in a unique Martian wind tunnel that is placed in a vacuum chamber to simulate the Martian atmosphere. Computational findings are compared with pressure sensitive paint and direct force measurements and are found to be in agreement. The separated flow from the leading edge is found to form a large leading-edge vortex that sits directly above the apex of the airfoil and provides enhanced lift at post stall angles of attack. For higher subsonic flows, the vortical structures elongate in the streamwise direction resulting in reduced lift enhancement. We also observe that the onset of spanwise instability for higher angles of attack is delayed at lower Mach numbers. Currently at Mitsubishi Heavy Industries, Ltd., Nagasaki.
29 CFR 1926.803 - Compressed air.
Code of Federal Regulations, 2011 CFR
2011-07-01
... reverse flow. The oxygen system inside the chamber shall be of a closed circuit design and be so designed as to automatically shut off the oxygen supply whenever the fire system is activated. (xii) Be in... system that can be activated inside the lock or by the outside lock tender. (xi) Be provided with...
29 CFR 1926.803 - Compressed air.
Code of Federal Regulations, 2012 CFR
2012-07-01
... reverse flow. The oxygen system inside the chamber shall be of a closed circuit design and be so designed as to automatically shut off the oxygen supply whenever the fire system is activated. (xii) Be in... system that can be activated inside the lock or by the outside lock tender. (xi) Be provided with...
29 CFR 1926.803 - Compressed air.
Code of Federal Regulations, 2013 CFR
2013-07-01
... reverse flow. The oxygen system inside the chamber shall be of a closed circuit design and be so designed as to automatically shut off the oxygen supply whenever the fire system is activated. (xii) Be in... system that can be activated inside the lock or by the outside lock tender. (xi) Be provided with...
Supersonic Air Flow due to Solid-Liquid Impact
NASA Astrophysics Data System (ADS)
Gekle, Stephan; Peters, Ivo R.; Gordillo, José Manuel; van der Meer, Devaraj; Lohse, Detlef
2010-01-01
A solid object impacting on liquid creates a liquid jet due to the collapse of the impact cavity. Using visualization experiments with smoke particles and multiscale simulations, we show that in addition, a high-speed air jet is pushed out of the cavity. Despite an impact velocity of only 1m/s, this air jet attains supersonic speeds already when the cavity is slightly larger than 1 mm in diameter. The structure of the air flow closely resembles that of compressible flow through a nozzle—with the key difference that here the “nozzle” is a liquid cavity shrinking rapidly in time.
Compressed air system upgrade results in substantial energy savings
None, None
2002-01-01
This case study highlights a compressed air system upgrade at BWX Technologies manufacturing plant in Lynchburg, Virginia, which replaced antiquated compressors and dryers and implemented an improved control strategy, resulting in improved energy efficiency and savings in energy and maintenance costs.
46 CFR 112.50-7 - Compressed air starting.
Code of Federal Regulations, 2010 CFR
2010-10-01
... 46 Shipping 4 2010-10-01 2010-10-01 false Compressed air starting. 112.50-7 Section 112.50-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) ELECTRICAL ENGINEERING EMERGENCY LIGHTING AND POWER SYSTEMS Emergency Diesel and Gas Turbine Engine Driven Generator Sets § 112.50-7...
Clustering of inertial particles in compressible chaotic flows
NASA Astrophysics Data System (ADS)
Pérez-Muñuzuri, Vicente
2015-05-01
Clustering of inertial particles is analyzed in chaotic compressible flows. A simplified dynamical model for the motion of inertial particles in a compressible flow has been derived. Clustering enhancement has been observed for intermediate Stokes times and characterized in terms of the number of particles with negative finite-time Lyapunov exponents and the Lyapunov dimension of the model attractor. Cluster formation has been observed to depend on the nature of the flow; vortical or shear. The motion of heavy and light particles is analyzed in terms of the compressibility and correlation length of the density field.
Clustering of inertial particles in compressible chaotic flows.
Pérez-Muñuzuri, Vicente
2015-05-01
Clustering of inertial particles is analyzed in chaotic compressible flows. A simplified dynamical model for the motion of inertial particles in a compressible flow has been derived. Clustering enhancement has been observed for intermediate Stokes times and characterized in terms of the number of particles with negative finite-time Lyapunov exponents and the Lyapunov dimension of the model attractor. Cluster formation has been observed to depend on the nature of the flow; vortical or shear. The motion of heavy and light particles is analyzed in terms of the compressibility and correlation length of the density field. PMID:26066228
A PDF closure model for compressible turbulent chemically reacting flows
NASA Technical Reports Server (NTRS)
Kollmann, W.
1992-01-01
The objective of the proposed research project was the analysis of single point closures based on probability density function (pdf) and characteristic functions and the development of a prediction method for the joint velocity-scalar pdf in turbulent reacting flows. Turbulent flows of boundary layer type and stagnation point flows with and without chemical reactions were be calculated as principal applications. Pdf methods for compressible reacting flows were developed and tested in comparison with available experimental data. The research work carried in this project was concentrated on the closure of pdf equations for incompressible and compressible turbulent flows with and without chemical reactions.
Incipient transition phenomena in compressible flows over a flat plate
NASA Technical Reports Server (NTRS)
Erlebacher, G.; Hussaini, M. Y.
1986-01-01
The full three-dimensional time-dependent compressible Navier-Stokes equations are solved by a Fourier-Chebyshev method to study the stability of compressible flows over a flat plate. After the code is validated in the linear regime, it is applied to study the existence of the secondary instability mechanism in the supersonic regime.
Legal and regulatory issues affecting compressed air energy storage
Hendrickson, P.L.
1981-07-01
Several regulatory and legal issues that can potentially affect implementation of a compressed air energy storage (CAES) system are discussed. This technology involves the compression of air using base load electric power for storage in an underground storage medium. The air is subsequently released and allowed to pass through a turbine to generate electricity during periods of peak demand. The storage media considered most feasible are a mined hard rock cavern, a solution-mined cavern in a salt deposit, and a porous geologic formation (normally an aquifer) of suitable structure. The issues are discussed in four categories: regulatory issues common to most CAES facilities regardless of storage medium, regulatory issues applicable to particular CAES reservoir media, issues related to possible liability from CAES operations, and issues related to acquisition of appropriate property rights for CAES implementation. The focus is on selected federal regulation. Lesser attention is given to state and local regulation. (WHK)
Finite-volume WENO scheme for viscous compressible multicomponent flows.
Coralic, Vedran; Colonius, Tim
2014-10-01
We develop a shock- and interface-capturing numerical method that is suitable for the simulation of multicomponent flows governed by the compressible Navier-Stokes equations. The numerical method is high-order accurate in smooth regions of the flow, discretely conserves the mass of each component, as well as the total momentum and energy, and is oscillation-free, i.e. it does not introduce spurious oscillations at the locations of shockwaves and/or material interfaces. The method is of Godunov-type and utilizes a fifth-order, finite-volume, weighted essentially non-oscillatory (WENO) scheme for the spatial reconstruction and a Harten-Lax-van Leer contact (HLLC) approximate Riemann solver to upwind the fluxes. A third-order total variation diminishing (TVD) Runge-Kutta (RK) algorithm is employed to march the solution in time. The derivation is generalized to three dimensions and nonuniform Cartesian grids. A two-point, fourth-order, Gaussian quadrature rule is utilized to build the spatial averages of the reconstructed variables inside the cells, as well as at cell boundaries. The algorithm is therefore fourth-order accurate in space and third-order accurate in time in smooth regions of the flow. We corroborate the properties of our numerical method by considering several challenging one-, two- and three-dimensional test cases, the most complex of which is the asymmetric collapse of an air bubble submerged in a cylindrical water cavity that is embedded in 10% gelatin. PMID:25110358
Finite-volume WENO scheme for viscous compressible multicomponent flows
Coralic, Vedran; Colonius, Tim
2014-01-01
We develop a shock- and interface-capturing numerical method that is suitable for the simulation of multicomponent flows governed by the compressible Navier-Stokes equations. The numerical method is high-order accurate in smooth regions of the flow, discretely conserves the mass of each component, as well as the total momentum and energy, and is oscillation-free, i.e. it does not introduce spurious oscillations at the locations of shockwaves and/or material interfaces. The method is of Godunov-type and utilizes a fifth-order, finite-volume, weighted essentially non-oscillatory (WENO) scheme for the spatial reconstruction and a Harten-Lax-van Leer contact (HLLC) approximate Riemann solver to upwind the fluxes. A third-order total variation diminishing (TVD) Runge-Kutta (RK) algorithm is employed to march the solution in time. The derivation is generalized to three dimensions and nonuniform Cartesian grids. A two-point, fourth-order, Gaussian quadrature rule is utilized to build the spatial averages of the reconstructed variables inside the cells, as well as at cell boundaries. The algorithm is therefore fourth-order accurate in space and third-order accurate in time in smooth regions of the flow. We corroborate the properties of our numerical method by considering several challenging one-, two- and three-dimensional test cases, the most complex of which is the asymmetric collapse of an air bubble submerged in a cylindrical water cavity that is embedded in 10% gelatin. PMID:25110358
Moving and adaptive grid methods for compressible flows
NASA Technical Reports Server (NTRS)
Trepanier, Jean-Yves; Camarero, Ricardo
1995-01-01
This paper describes adaptive grid methods developed specifically for compressible flow computations. The basic flow solver is a finite-volume implementation of Roe's flux difference splitting scheme or arbitrarily moving unstructured triangular meshes. The grid adaptation is performed according to geometric and flow requirements. Some results are included to illustrate the potential of the methodology.
Reevaluation of compressible-flow Preston tube calibrations
NASA Technical Reports Server (NTRS)
Allen, J. M.
1977-01-01
Revised zero-pressure-gradient, adiabatic wall skin-friction-balance data covering a Mach number range from 1.6 to 4.6 led to a reevaluation of existing compressible flow Preston tube calibration equations.
NASA Astrophysics Data System (ADS)
Yusman, W.; Viridi, S.; Rachmat, S.
2016-01-01
The non-discharges geothermal wells have been a main problem in geothermal development stages and well discharge stimulation is required to initiate a flow. Air compress stimulation is one of the methods to trigger a fluid flow from the geothermal reservoir. The result of this process can be predicted by using by the Af / Ac method, but sometimes this method shows uncertainty result in several geothermal wells and also this prediction method does not take into account the flowing time of geothermal fluid to discharge after opening the well head. This paper presents a simulation of non-discharges well under air compress stimulation to predict well behavior and time process required. The component of this model consists of geothermal well data during heating-up process such as pressure, temperature and mass flow in the water column and main feed zone level. The one-dimensional transient numerical model is run based on the Single Fluid Volume Element (SFVE) method. According to the simulation result, the geothermal well behavior prediction after air compress stimulation will be valid under two specific circumstances, such as single phase fluid density between 1 - 28 kg/m3 and above 28.5 kg/m3. The first condition shows that successful well discharge and the last condition represent failed well discharge after air compress stimulation (only for two wells data). The comparison of pf values between simulation and field observation shows the different result according to the success discharge well. Time required for flow to occur as observed in well head by using the SFVE method is different with the actual field condition. This model needs to improve by updating more geothermal well data and modified fluid phase condition inside the wellbore.
Compressible flow calculations employing the Galerkin/least-squares method
NASA Technical Reports Server (NTRS)
Shakib, F.; Hughes, T. J. R.; Johan, Zdenek
1989-01-01
A multielement group, domain decomposition algorithm is presented for solving linear nonsymmetric systems arising in the finite-element analysis of compressible flows employing the Galerkin/least-squares method. The iterative strategy employed is based on the generalized minimum residual (GMRES) procedure originally proposed by Saad and Shultz. Two levels of preconditioning are investigated. Applications to problems of high-speed compressible flow illustrate the effectiveness of the scheme.
Rupture of sigmoid colon caused by compressed air.
Yin, Wan-Bin; Hu, Ji-Lin; Gao, Yuan; Zhang, Xian-Xiang; Zhang, Mao-Shen; Liu, Guang-Wei; Zheng, Xue-Feng; Lu, Yun
2016-03-14
Compressed air has been generally used since the beginning of the 20(th) century for various applications. However, rupture of the colon caused by compressed air is uncommon. We report a case of pneumatic rupture of the sigmoid colon. The patient was admitted to the emergency room complaining of abdominal pain and distention. His colleague triggered a compressed air nozzle against his anus as a practical joke 2 h previously. On arrival, his pulse rate was 126 beats/min, respiratory rate was 42 breaths/min and blood pressure was 86/54 mmHg. Physical examination revealed peritoneal irritation and the abdomen was markedly distended. Computed tomography of the abdomen showed a large volume of air in the abdominal cavity. Peritoneocentesis was performed to relieve the tension pneumoperitoneum. Emergency laparotomy was done after controlling shock. Laparotomy revealed a 2-cm perforation in the sigmoid colon. The perforation was sutured and temporary ileostomy was performed as well as thorough drainage and irrigation of the abdominopelvic cavity. Reversal of ileostomy was performed successfully after 3 mo. Follow-up was uneventful. We also present a brief literature review. PMID:26973403
Studies of compressible shear flows and turbulent drag reduction
NASA Technical Reports Server (NTRS)
Orszag, S. A.
1981-01-01
Compressible shear flows and drag reduction were examined and three methods are addressed: (1) the analytical and numerical aspects of conformal mapping were summarized and a new method for computation of these maps is presented; (2) the computer code SPECFD for solution of the three dimensional time dependent Navier-Stokes equations for compressible flow on the CYBER 203 computer is described; (3) results of two equation turbulence modeling of turbulent flow over wavy walls are presented. A modified Jones-Launder model is used in two dimensional spectral code for flow in general wavy geometries.
Compressed Air System Optimization Improves Production and saves energy at a Satellite Manufacturer
2002-05-01
In 2001, a compressed air improvement project was implemented following an audit on the compressed air system at Boeing Satellite Systems (formerly Hughes Space & Communications Company) in Los Angeles, California.
NASA Technical Reports Server (NTRS)
Walchner, O
1939-01-01
Errors arising from yawed flow were also determined up to 20 degrees angle of attack. In axial flow, the Prandtl pitot tube begins at w/a approx. = 0.8 to give an incorrect static pressure reading, while it records the tank pressure correctly, as anticipated, up to sonic velocity. Owing to the compressibility of the air, the Prandtl pitot tube manifests compression shocks when the air speed approaches velocity of sound. This affects the pressure reading of the instrument. Because of the increasing importance of high speed in aviation, this compressibility effect is investigated in detail.
THE BERNOULLI EQUATION AND COMPRESSIBLE FLOW THEORIES
The incompressible Bernoulli equation is an analytical relationship between pressure, kinetic energy, and potential energy. As perhaps the simplest and most useful statement for describing laminar flow, it buttresses numerous incompressible flow models that have been developed ...
Environmental and regulatory aspects of compressed-air energy storage
Beckwith, M.A.; Mathur, J.
1981-01-01
The effects of fuel regulations, environmental protection laws, the National Environmental Policy Act, underground injection regulations, and state regulations on the development of compressed air storage systems and power plants are discussed. It is concluded that environmental regulatory concerns of conventional energy technologies are often different from those associated with new technologies such as compressed air energy storage (CAES). Confusion and uncertainty often results when the current environmental regulatory system is applied to new technologies. Evolution of the regulatory system must accompany and rapidly accommodate technological development if the benefits of such development are to be fully realized in a timely manner. Those responsible for technological development in the energy field must be aware of these disparities and conduct their efforts accordingly.
CLASSIFICATION OF THE MGR SUBSURFACE COMPRESSED AIR SYSTEM
R. Garrett
1999-08-31
The purpose of this analysis is to document the Quality Assurance (QA) classification of the Monitored Geologic Repository (MGR) subsurface compressed air system structures, systems and components (SSCs) performed by the MGR Safety Assurance Department. This analysis also provides the basis for revision of YMP/90-55Q, Q-List (YMP 1998). The Q-List identifies those MGR SSCs subject to the requirements of DOE/RW-0333P, ''Quality Assurance Requirements and Description'' (QARD) (DOE 1998).
CLASSIFICATION OF THE MGR SITE COMPRESSED AIR SYSTEM
J.A. Ziegler
1999-08-31
The purpose of this analysis is to document the Quality Assurance (QA) classification of the Monitored Geologic Repository (MGR) site compressed air system structures, systems and components (SSCs) performed by the MGR Safety Assurance Department. This analysis also provides the basis for revision of YMP/90-55Q, Q-List (YMP 1998). The Q-List identifies those MGR SSCs subject to the requirements of DOE/RW-0333P, ''Quality Assurance Requirements and Description'' (QARD) (DOE 1998).
Prefeasibility study on compressed air energy storage systems
NASA Astrophysics Data System (ADS)
Elmahgary, Y.; Peltola, E.; Sipilae, K.; Vaeaetaeinen, A.
1991-08-01
A prefeasibility study on compressed air energy storage (CALS) systems was launched in VTT in the course of the year 1990. The study was undertaken partly in the Laboratory of Electrical and Automation Engineering and partly in the Road, Traffic and Geotechnical Laboratory. Information on existing mines in Finland which could be used as storage caverns were collected (part 2). The costs of excavating rock caverns for compressed air storage and those for forming suitable storage caverns in existing mines were also estimated. This information was used in the first (and present) part of the report to calculate the economics of CAES. In the present part (part 1) of the study, an analysis of the different possible systems was given following a review of literature on CAES. This was followed by an economic analysis which comprised two separate systems. The first consisted of conventional oil fueled gas turbine plants provided with the CALS system. In the second system, wind turbines were used to run the compressors which are used in charging the compressed air storage cavern. The results of the current prefeasibility study confirmed the economic attractiveness of the CAES in the first system. Wind turbines still seem, however, to be too expensive to compete with coal power plants. More accurate and straight-forward results could be obtained only in a more comprehensive study.
Near-wall modelling of compressible turbulent flows
NASA Technical Reports Server (NTRS)
So, Ronald M. C.
1990-01-01
Work was carried out to formulate near-wall models for the equations governing the transport of the temperature-variance and its dissipation rate. With these equations properly modeled, a foundation is laid for their extension together with the heat-flux equations to compressible flows. This extension is carried out in a manner similar to that used to extend the incompressible near-wall Reynolds-stress models to compressible flows. The methodology used to accomplish the extension of the near-wall Reynolds-stress models is examined and the actual extension of the models for the Reynolds-stress equations and the near-wall dissipation-rate equation to compressible flows is given. Then the formulation of the near-wall models for the equations governing the transport of the temperature variance and its dissipation rate is discussed. Finally, a sample calculation of a flat plate compressible turbulent boundary-layer flow with adiabatic wall boundary condition and a free-stream Mach number of 2.5 using a two-equation near-wall closure is presented. The results show that the near-wall two-equation closure formulated for compressible flows is quite valid and the calculated properties are in good agreement with measurements. Furthermore, the near-wall behavior of the turbulence statistics and structure parameters is consistent with that found in incompressible flows.
Compressed-air energy storage field test using the aquifer at Pittsfield, Illinois
Istvan, J.A.; Pereira, J.C.; Roark, P.; Bakhtiari, H. )
1990-02-01
This report describes the design, construction, and operation of a field experiment to examine feasibility of full-scale compressed air energy storage (CAES) within aquifer reservoirs. A summary of data obtained and the conclusions from the field experiment are presented. Two injection/withdrawal wells, two instrument wells, and four logging/sampling wells were drilled and cored. Air was injected in the St. Peter Sandstone to create an air bubble which was cycled with ambient and elevated temperature air in the injection withdrawal pattern contemplated for CAES installations. At its peak content of 111.75 {times} 10{sup 6} scf, the air bubble was 30 ft thick at the I/W well area and reached 18 ft in thickness at a distance of 686 ft from the I/W well. Three post-test core wells were drilled and cored. The caprock, reservoir, and formation water were sampled and analyzed prior to and after exposure to compressed air and associated water. Samples of stored air were collected and analyzed. Items of interest were degree of liquid entrance into flowing well, effects in aquifer of increased air temperature, and changes in oxygen content of air. Prior to plugging and abandoning the well field, an additional well was drilled and cored, outside the air bubble. This work is part of the continuing research by EPRI to investigate the geochemical oxidation process. Reservoir engineering and utilization of geologic media for storing air has many complexities, but it has useable experience from successful natural gas storage. The design, construction, and testing at Pittsfield demonstrates that orientation toward useage of an aquifer air storage facility can be performed successfully. The disappearance of oxygen needs attention for seasonal storage of air but should not dampen enthusiasm for weekly or daily storage cycles.
Computation techniques for the simulation of turbomachinery compressible flows
NASA Astrophysics Data System (ADS)
Veuillot, J. P.; Cambier, L.
Computation techniques for the simulation of turbomachinery compressible flows via the numerical solution of Euler and Navier-Stokes equations are described. In a discussion of the Euler and Navier-Stokes equations for turbomachinery flow calculations, attention is given to equations for a rotating system, quasi-three-dimensional formulation, and turbulence modeling. Examples of Navier-Stokes calculations are presented.
Accounting For Compressibility In Viscous Flow In Pipes
NASA Technical Reports Server (NTRS)
Steinle, Frank W.; Gee, Ken; Murthy, Sreedhara V.
1991-01-01
Method developed to account for effects of compressibility in viscous flows through long, circular pipes of uniform diameter. Based on approximation of variations in density and velocity across pipe cross section by profile equations developed for boundary-layer flow between flat plates.
An implicit Lagrangian lattice Boltzmann method for the compressible flows
NASA Astrophysics Data System (ADS)
Yan, Guangwu; Dong, Yinfeng; Liu, Yanhong
2006-08-01
In this paper, we propose a new Lagrangian lattice Boltzmann method (LBM) for simulating the compressible flows. The new scheme simulates fluid flows based on the displacement distribution functions. The compressible flows, such as shock waves and contact discontinuities are modelled by using Lagrangian LBM. In this model, we select the element in the Lagrangian coordinate to satisfy the basic fluid laws. This model is a simpler version than the corresponding Eulerian coordinates, because the convection term of the Euler equations disappears. The numerical simulations conform to classical results.
Numerical Simulation of Airfoil Vibrations Induced by Compressible Flow
NASA Astrophysics Data System (ADS)
Feistauer, Miloslav; Kučera, Václav; Šimánek, Petr
2010-09-01
The paper is concerned with the numerical solution of interaction of compressible flow and a vibrating airfoil with two degrees of freedom, which can rotate around an elastic axis and oscillate in the vertical direction. Compressible flow is described by the Euler or Navier-Stokes equations written in the ALE form. This system is discretized by the semi-implicit discontinuous Galerkin finite element method (DGFEM) and coupled with the solution of ordinary differential equations describing the airfoil motion. Computational results showing the flow induced airfoil vibrations are presented.
Thermoacoustic compression based on alternating to direct gas flow conversion
NASA Astrophysics Data System (ADS)
Sun, D. M.; Wang, K.; Xu, Y.; Shen, Q.; Zhang, X. J.; Qiu, L. M.
2012-05-01
We present a remarkable thermoacoustically driven compression effect based on the conversion of gas flow from an alternating state to a direct state. The alternating gas flow is generated by the thermoacoustic effect in thermoacoustic engines, whereas direct gas flow is achieved by means of the flow rectification effect of check valves. A demonstrative thermoacoustic compressor consisting of two standing-wave thermoacoustic engines, two reservoirs, and three check valves is constructed for experimental investigation. With nitrogen as a working gas and an initial pressure of 2.4 MPa in all components, a usable pressure difference of 0.4 MPa is achieved, with the average gas pumping rate reaching 2.85 Nm3/h during the first 3 s of the compression process. The simple mechanical structure and thermally driven nature of the compressor show potential in gas compression, power generation, and refrigeration applications.
A compressible Navier-Stokes code for turbulent flow modeling
NASA Technical Reports Server (NTRS)
Coakley, T. J.
1984-01-01
An implicit, finite volume code for solving two dimensional, compressible turbulent flows is described. Second order upwind differencing of the inviscid terms of the equations is used to enhance stability and accuracy. A diagonal form of the implicit algorithm is used to improve efficiency. Several zero and two equation turbulence models are incorporated to study their impact on overall flow modeling accuracy. Applications to external and internal flows are discussed.
Improved fireman's compressed air breathing system pressure vessel development program
NASA Technical Reports Server (NTRS)
King, H. A.; Morris, E. E.
1973-01-01
Prototype high pressure glass filament-wound, aluminum-lined pressurant vessels suitable for use in a fireman's compressed air breathing system were designed, fabricated, and acceptance tested in order to demonstrate the feasibility of producing such high performance, lightweight units. The 4000 psi tanks have a 60 standard cubic foot (SCF) air capacity, and have a 6.5 inch diamter, 19 inch length, 415 inch volume, weigh 13 pounds when empty, and contain 33 percent more air than the current 45 SCF (2250 psi) steel units. The current steel 60 SCF (3000 psi) tanks weigh approximately twice as much as the prototype when empty, and are 2 inches, or 10 percent shorter. The prototype units also have non-rusting aluminum interiors, which removes the hazard of corrosion, the need for internal coatings, and the possibility of rust particles clogging the breathing system.
Smoothness monitors for compressible flow computation
Sjogreen, B; Yee, H C
2008-09-02
In [SY04, YS07] and references cited therein, the authors introduced the concept of employing multiresolution wavelet decomposition of computed flow data as smoothness monitors (flow sensors) to indicate the amount and location of built-in numerical dissipation that can be eliminated or further reduced in shock-capturing schemes. Studies indicated that this approach is able to limit the use of numerical dissipation with improved accuracy compared with standard shock-capturing methods. The studies in [SY04, YS07] were limited to low order multiresolution redundant wavelets with low level supports and low order vanishing moments. The objective of this paper is to expand the previous investigation to include higher order redundant wavelets with larger support and higher order vanishing moments for a wider spectrum of flow type and flow speed applications.
Compressible Turbulent Channel Flows: DNS Results and Modeling
NASA Technical Reports Server (NTRS)
Huang, P. G.; Coleman, G. N.; Bradshaw, P.; Rai, Man Mohan (Technical Monitor)
1994-01-01
The present paper addresses some topical issues in modeling compressible turbulent shear flows. The work is based on direct numerical simulation of two supersonic fully developed channel flows between very cold isothermal walls. Detailed decomposition and analysis of terms appearing in the momentum and energy equations are presented. The simulation results are used to provide insights into differences between conventional time-and Favre-averaging of the mean-flow and turbulent quantities. Study of the turbulence energy budget for the two cases shows that the compressibility effects due to turbulent density and pressure fluctuations are insignificant. In particular, the dilatational dissipation and the mean product of the pressure and dilatation fluctuations are very small, contrary to the results of simulations for sheared homogeneous compressible turbulence and to recent proposals for models for general compressible turbulent flows. This provides a possible explanation of why the Van Driest density-weighted transformation is so successful in correlating compressible boundary layer data. Finally, it is found that the DNS data do not support the strong Reynolds analogy. A more general representation of the analogy is analysed and shown to match the DNS data very well.
NASA Astrophysics Data System (ADS)
Oldenburg, C. M.; Pan, L.
2015-12-01
Although large opportunities exist for compressed air energy storage (CAES) in aquifers and depleted natural gas reservoirs, only two grid-scale CAES facilities exist worldwide, both in salt caverns. As such, experience with CAES in porous media, what we call PM-CAES, is lacking and we have relied on modeling to elucidate PM-CAES processes. PM-CAES operates similarly to cavern CAES. Specifically, working gas (air) is injected through well(s) into the reservoir compressing the cushion gas (existing air in the reservoir). During energy recovery, high-pressure air from the reservoir flows first into a recuperator, then into an expander, and subsequently is mixed with fuel in a combustion turbine to produce electricity, thereby reducing compression costs. Energy storage in porous media is complicated by the solid matrix grains which provide resistance to flow (via permeability in Darcy's law); in the cap rock, low-permeability matrix provides the seal to the reservoir. The solid grains also provide storage capacity for heat that might arise from compression, viscous flow effects, or chemical reactions. The storage of energy in PM-CAES occurs variably across pressure gradients in the formation, while the solid grains of the matrix can release/store heat. Residual liquid (i.e., formation fluids) affects flow and can cause watering out at the production well(s). PG&E is researching a potential 300 MW (for ten hours) PM-CAES facility in a depleted gas reservoir near Lodi, California. Special considerations exist for depleted natural gas reservoirs because of mixing effects which can lead to undesirable residual methane (CH4) entrainment and reactions of oxygen and CH4. One strategy for avoiding extensive mixing of working gas (air) with reservoir CH4 is to inject an initial cushion gas with reduced oxygen concentration providing a buffer between the working gas (air) and the residual CH4 gas. This reduces the potential mixing of the working air with the residual CH4
Simulation of Inviscid Compressible Multi-Phase Flow with Condensation
NASA Technical Reports Server (NTRS)
Kelleners, Philip
2003-01-01
Condensation of vapours in rapid expansions of compressible gases is investigated. In the case of high temperature gradients the condensation will start at conditions well away from thermodynamic equilibrium of the fluid. In those cases homogeneous condensation is dominant over heterogeneous condensation. The present work is concerned with development of a simulation tool for computation of high speed compressible flows with homogeneous condensation. The resulting ow solver should preferably be accurate and robust to be used for simulation of industrial flows in general geometries.
Compressed-air energy-storage technology: Program overview
NASA Astrophysics Data System (ADS)
Kannberg, L. D.
1981-07-01
A new technology designed to reduce the consumption of oil in the generation of electric power was developed. The program has two major elements: reservoir stability studies and second generation concepts studies. The reservoir stability studies are aimed at developing stability criteria for long term operation of large underground reservoirs used for compressed air storage. The second generation concepts studies are aimed at developing new concepts that will require little or no petroleum fuels for operation. The program efforts are outlined and major accomplishments towards the objectives of the program are identified.
Computer aided optimal design of compressed air energy storage systems
NASA Astrophysics Data System (ADS)
Ahrens, F. W.; Sharma, A.; Ragsdell, K. M.
1980-07-01
An automated procedure for the design of Compressed Air Energy Storage (CAES) systems is presented. The procedure relies upon modern nonlinear programming algorithms, decomposition theory, and numerical models of the various system components. Two modern optimization methods are employed; BIAS, a Method of Multipliers code and OPT, a Generalized Reduced Gradient code. The procedure is demonstrated by the design of a CAES facility employing the Media, Illinois Galesville aquifer as the reservoir. The methods employed produced significant reduction in capital and operating cost, and in number of aquifer wells required.
Compressed air energy storage technology program. Annual report for 1980
Kannberg, L.D.
1981-06-01
All of the major research funded under the Compressed Air Energy Storage Technology Program during the period March 1980 to March 1981 is described. This annual report is divided into two segments: Reservoir Stability Studies and Second-Generation Concepts Studies. The first represents research performed to establish stability criteria for CAES reservoirs while the second reports progress on research performed on second-generation CAES concepts. The report consists of project reports authored by research engineers and scientists from PNL and numerous subcontractors including universities, architect-engineering, and other private firms.
Lehigh Southwest Cement Company: Compressed Air System Improvement Saves Energy
2003-10-01
In 2001, Lehigh Southwest Cement Company improved the compressed air system at its cement plant in Tehachapi, California. Consequently, the system was able to operate more efficiently with less compressor capacity and at a lower system pressure. The project yielded total annual savings of 895,000 kWh and $199,000. The initial project cost was $417,000, but Southern California Edison provided a $90,000 incentive payment to reduce the cost to $327,000. Simple payback was about 20 months.
Geothermally Coupled Well-Based Compressed Air Energy Storage
Davidson, Casie L.; Bearden, Mark D.; Horner, Jacob A.; Cabe, James E.; Appriou, Delphine; McGrail, B. Peter
2015-12-20
Previous work by McGrail et al. (2013, 2015) has evaluated the possibility of pairing compressed air energy storage with geothermal resources in lieu of a fossil-fired power generation component, and suggests that such applications may be cost competitive where geology is favorable to siting both the geothermal and CAES components of such a system. Those studies also note that the collocation of subsurface resources that meet both sets of requirements are difficult to find in areas that also offer infrastructure and near- to mid-term market demand for energy storage. This study examines a novel application for the compressed air storage portion of the project by evaluating the potential to store compressed air in disused wells by amending well casings to serve as subsurface pressure vessels. Because the wells themselves would function in lieu of a geologic storage reservoir for the CAES element of the project, siting could focus on locations with suitable geothermal resources, as long as there was also existing wellfield infrastructure that could be repurposed for air storage. Existing wellfields abound in the United States, and with current low energy prices, many recently productive fields are now shut in. Should energy prices remain stagnant, these idle fields will be prime candidates for decommissioning unless they can be transitioned to other uses, such as redevelopment for energy storage. In addition to the nation’s ubiquitous oil and gas fields, geothermal fields, because of their phased production lifetimes, also may offer many abandoned wellbores that could be used for other purposes, often near currently productive geothermal resources. These existing fields offer an opportunity to decrease exploration and development uncertainty by leveraging data developed during prior field characterization, drilling, and production. They may also offer lower-cost deployment options for hybrid geothermal systems via redevelopment of existing well-field infrastructure
Geothermally Coupled Well-Based Compressed Air Energy Storage
Davidson, C L; Bearden, Mark D; Horner, Jacob A; Appriou, Delphine; McGrail, B Peter
2015-12-01
Previous work by McGrail et al. (2013, 2015) has evaluated the possibility of pairing compressed air energy storage with geothermal resources in lieu of a fossil-fired power generation component, and suggests that such applications may be cost competitive where geology is favorable to siting both the geothermal and CAES components of such a system. Those studies also note that the collocation of subsurface resources that meet both sets of requirements are difficult to find in areas that also offer infrastructure and near- to mid-term market demand for energy storage. This study examines a novel application for the compressed air storage portion of the project by evaluating the potential to store compressed air in disused wells by amending well casings to serve as subsurface pressure vessels. Because the wells themselves would function in lieu of a geologic storage reservoir for the CAES element of the project, siting could focus on locations with suitable geothermal resources, as long as there was also existing wellfield infrastructure that could be repurposed for air storage. Existing wellfields abound in the United States, and with current low energy prices, many recently productive fields are now shut in. Should energy prices remain stagnant, these idle fields will be prime candidates for decommissioning unless they can be transitioned to other uses, such as redevelopment for energy storage. In addition to the nation’s ubiquitous oil and gas fields, geothermal fields, because of their phased production lifetimes, also may offer many abandoned wellbores that could be used for other purposes, often near currently productive geothermal resources. These existing fields offer an opportunity to decrease exploration and development uncertainty by leveraging data developed during prior field characterization, drilling, and production. They may also offer lower-cost deployment options for hybrid geothermal systems via redevelopment of existing well-field infrastructure
NASA Technical Reports Server (NTRS)
Dixon, G. V.; Barringer, S. R.; Gray, C. E.; Leatherman, A. D.
1975-01-01
Computer programs and resulting tabulations are presented of pipeline length-to-diameter ratios as a function of Mach number and pressure ratios for compressible flow. The tabulations are applicable to air, nitrogen, oxygen, and hydrogen for compressible isothermal flow with friction and compressible adiabatic flow with friction. Also included are equations for the determination of weight flow. The tabulations presented cover a wider range of Mach numbers for choked, adiabatic flow than available from commonly used engineering literature. Additional information presented, but which is not available from this literature, is unchoked, adiabatic flow over a wide range of Mach numbers, and choked and unchoked, isothermal flow for a wide range of Mach numbers.
Numerical simulation of a compressible homogeneous, turbulent shear flow
NASA Astrophysics Data System (ADS)
Feiereisen, W. J.; Reynolds, W. C.; Ferziger, J. H.
1981-03-01
A direct, low Reynolds number, numerical simulation was performed on a homogeneous turbulent shear flow. The full compressible Navier-Stokes equations were used in a simulation on the ILLIAC IV computer with a 64,000 mesh. The flow fields generated by the code are used as an experimental data base, to examine the behavior of the Reynols stresses in this simple, compressible flow. The variation of the structure of the stresses and their dynamic equations as the character of the flow changed is emphasized. The structure of the tress tensor is more heavily dependent on the shear number and less on the fluctuating Mach number. The pressure-strain correlation tensor in the dynamic uations is directly calculated in this simulation. These correlations are decomposed into several parts, as contrasted with the traditional incompressible decomposition into two parts. The performance of existing models for the conventional terms is examined, and a model is proposed for the 'mean fluctuating' part.
The flow of a compressible fluid past a curved surface
NASA Technical Reports Server (NTRS)
Kaplan, Carl
1943-01-01
An iteration method is employed to obtain the flow of a compressible fluid past a curved surface. The first approximation which leads to the Prandtl-Glauert rule, is based on the assumption that the flow differs but little from a pure translation. The iteration process then consists in improving this first approximation in order that it will apply to a flow differing from pure translatory motion to a greater degree. The method fails when the Mach number of the undisturbed stream reaches unity but permits a transition from subsonic to supersonic conditions without the appearance of a compression shock. The limiting value at which potential flow no longer exits is indicated by the apparent divergence of the power series representing the velocity of the fluid at the surface of the solid boundary.
Raytheon: Compressed Air System Upgrade Saves Energy and Improves Performance
Not Available
2005-04-01
In 2003, Raytheon Company upgraded the efficiency of the compressed air system at its Integrated Air Defense Center in Andover, Massachusetts, to save energy and reduce costs. Worn compressors and dryers were replaced, a more sophisticated control strategy was installed, and an aggressive leak detection and repair effort was carried out. The total cost of these improvements was $342,000; however, National Grid, a utility service provider, contributed a $174,000 incentive payment. Total annual energy and maintenance cost savings are estimated at $141,500, and energy savings are nearly 1.6 million kWh. This case study was prepared for the U.S. Department of Energy's Industrial Technologies Program.
Compressed air energy storage technology program. Annual report for 1979
Loscutoff, W.V.
1980-06-01
The objectives of the Compressed Air Energy Storage (CAES) program are to establish stability criteria for large underground reservoirs in salt domes, hard rock, and porous rock used for air storage in utility applications, and to develop second-generation CAES technologies that have minimal or no dependence on petroleum fuels. During the year reported reports have been issued on field studies on CAES on aquifers and in salt, stability, and design criteria for CAES and for pumped hydro-storage caverns, laboratory studies of CAES in porous rock reservoris have continued. Research has continued on combined CAES/Thermal Energy Storage, CAES/Solar systems, coal-fired fluidized bed combustors for CAES, and two-reservoir advanced CAES concepts. (LCL)
The upper-branch stability of compressible boundary layer flows
NASA Technical Reports Server (NTRS)
Gajjar, J. S. B.; Cole, J. W.
1989-01-01
The upper-branch linear and nonlinear stability of compressible boundary layer flows is studied using the approach of Smith and Bodonyi (1982) for a similar incompressible problem. Both pressure gradient boundary layers and Blasius flow are considered with and without heat transfer, and the neutral eigenrelations incorporating compressibility effects are obtained explicitly. The compressible nonlinear viscous critical layer equations are derived and solved numerically and the results indicate some solutions with positive phase shift across the critical layer. Various limiting cases are investigated including the case of much larger disturbance amplitudes and this indicates the structure for the strongly nonlinear critical layer of the Benney-Bergeon (1969) type. It is also shown how a match with the inviscid neutral inflexional modes arising from the generalized inflexion point criterion, is achieved.
Computational methods for vortex dominated compressible flows
NASA Technical Reports Server (NTRS)
Murman, Earll M.
1987-01-01
The principal objectives were to: understand the mechanisms by which Euler equation computations model leading edge vortex flows; understand the vortical and shock wave structures that may exist for different wing shapes, angles of incidence, and Mach numbers; and compare calculations with experiments in order to ascertain the limitations and advantages of Euler equation models. The initial approach utilized the cell centered finite volume Jameson scheme. The final calculation utilized a cell vertex finite volume method on an unstructured grid. Both methods used Runge-Kutta four stage schemes for integrating the equations. The principal findings are briefly summarized.
A 3-dimensional mass conserving element for compressible flows
NASA Technical Reports Server (NTRS)
Fix, G.; Suri, M.
1985-01-01
A variety of finite element schemes has been used in the numerical approximation of compressible flows particularly in underwater acoustics. In many instances instabilities have been generated due to the lack of mass conservation. Two- and three-dimensional elements are developed which avoid these problems.
Carbon and energy saving markets in compressed air
NASA Astrophysics Data System (ADS)
Cipollone, R.
2015-08-01
CO2 reduction and fossil fuel saving represent two of the cornerstones of the environmental commitments of all the countries of the world. The first engagement is of a medium to long term type, and unequivocally calls for a new energetic era. The second delays in time the fossil fuel technologies to favour an energetic transition. In order to sustain the two efforts, new immaterial markets have been established in almost all the countries of the world, whose exchanges (purchases and sales) concern CO2 emissions and equivalent fossil fuels that have not been emitted or burned. This paper goes deep inside two aspects not yet exploited: specific CO2 emissions and equivalent fossil fuel burned, as a function of compressed air produced. Reference is made to the current compressor technology, carefully analysing CAGI's (Compressed Air Gas Institute) data and integrating it with the PNUEROP (European Association of manufacturers of compressors, vacuum pumps, pneumatic tools and allied equipment) contribution on the compressor European market. On the base of energy saving estimates that could be put in place, this article also estimates the financial value of the CO2 emissions and fossil fuels avoided.
Analysis of the transient compressible vapor flow in heat pipe
NASA Technical Reports Server (NTRS)
Jang, Jong Hoon; Faghri, Amir; Chang, Won Soon
1989-01-01
The transient compressible one-dimensional vapor flow dynamics in a heat pipe is modeled. The numerical results are obtained by using the implicit non-iterative Beam-Warming finite difference method. The model is tested for simulated heat pipe vapor flow and actual flow in cylindrical heat pipes. A good comparison of the present transient results for the simulated heat pipe vapor flow with the previous results of a two-dimensional numerical model is achieved and the steady state results are in agreement with the existing experimental data. The transient behavior of the vapor flow under subsonic, sonic, and supersonic speeds and high mass flow rates are successfully predicted. The one-dimensional model also describes the vapor flow dynamics in cylindrical heat pipes at high temperatures.
On two-dimensional flows of compressible fluids
NASA Technical Reports Server (NTRS)
Bergman, Stefan
1945-01-01
This report is devoted to the study of two-dimensional steady motion of a compressible fluid. It is shown that the complete flow pattern around a closed obstacle cannot be obtained by the method of Chaplygin. In order to overcome this difficulty, a formula for the stream-function of a two-dimensional subsonic flow is derived. The formula involves an arbitrary function of a complex variable and yields all possible subsonic flow patterns of certain types. Conditions are given so that the flow pattern in the physical plane will represent a flow around a closed curve. The formula obtained can be employed for the approximate determination of a subsonic flow around an obstacle. The method can be extended to partially supersonic flows.
Embedded function methods for compressible high speed turbulent flow
NASA Technical Reports Server (NTRS)
Walker, J. D. A.
1989-01-01
Fundamental issues relating to compressible turbulent flow are addressed. The focus has been on developing methods and testing concepts for attached flows rather than trying to force a conventional law of the wall into a zone of backflow. Although the dynamics of the near-wall flow in an attached turbulent boundary layer are relatively well documented, the dynamical features of a zone of reversed turbulent flow are not, nor are they well understood. Incompressibility introduces effects and issues that have been dealt with only marginally in the literature, therefore, the present work has been focussed on attached high-speed flows. The wall function method has been extended up through the supersonic to hypersonic speeds. Algorithms have been successfully introduced into the code that calculates the flow all the way to the wall, and testing is being carried out for progressively more complex flow situations.
Reynolds-constrained large-eddy simulation of compressible flow over a compression ramp
NASA Astrophysics Data System (ADS)
Xiao, Zuoli; Chen, Liang
2015-11-01
A novel large-eddy simulation (LES) method is introduced for numerical simulation of wall-bounded compressible turbulent flows. The subgrid-scale (SGS) model in this method is designed to be composed of two parts depending on the distance to the nearest wall. In the near-wall region, both the mean SGS stress and heat flux are constrained by external Reynolds stress and heat flux to ensure the total target quantities, while the fluctuating SGS stress and heat flux are closed in a traditional fashion but using residual model parameterizations. In the far-wall region, the conventional SGS model is directly employed with necessary smoothing operation in the neighborhood of the constrained-unconstrained interface, which might be different for the stress and heat flux depending on the flow configuration. Compressible flow over a compression ramp is numerically studied using the new LES technique. The results are compared with the available experimental and direct numerical simulation (DNS) data, and those from traditional LES and detached-eddy simulation (DES). It turns out that the Reynolds-constrained large-eddy simulation (RCLES) method can predict the size of the separation bubble, mean flow profile, and friction force, etc. more accurately than traditional LES and DES techniques. Moreover, the RCLES method proves to be much less sensitive to the grid resolution than traditional LES method, and makes pure LES of flows of engineering interest feasible with moderate grids.
Direct simulation of compressible turbulence in a shear flow
NASA Technical Reports Server (NTRS)
Sarkar, S.; Erlebacher, G.; Hussaini, M. Y.
1991-01-01
Compressibility effects on the turbulence in homogeneous shear flow are investigated. The growth of the turbulent kinetic energy was found to decrease with increasing Mach number: a phenomenon which is similar to the reduction of turbulent velocity intensities observed in experiments on supersonic free shear layers. An examination of the turbulent energy budget shows that both the compressible dissipation and the pressure-dilatation contribute to the decrease in the growth of kinetic energy. The pressure-dilatation is predominantly negative in homogeneous shear flow, in contrast to its predominantly positive behavior in isotropic turbulence. The different signs of the pressure-dilatation are explained by theoretical consideration of the equations for the pressure variance and density variance. Previously, the following results were obtained for isotropic turbulence: (1) the normalized compressible dissipation is of O(M(sub t)(exp 2)); and (2) there is approximate equipartition between the kinetic and potential energies associated with the fluctuating compressible mode. Both of these results were substantiated in the case of homogeneous shear. The dilatation field is significantly more skewed and intermittent than the vorticity field. Strong compressions seem to be more likely than strong expansions.
Toward the large-eddy simulation of compressible turbulent flows
NASA Technical Reports Server (NTRS)
Erlebacher, G.; Hussaini, M. Y.; Speziale, C. G.; Zang, T. A.
1990-01-01
New subgrid-scale models for the large-eddy simulation of compressible turbulent flows are developed and tested based on the Favre-filtered equations of motion for an ideal gas. A compressible generalization of the linear combination of the Smagorinsky model and scale-similarity model, in terms of Favre-filtered fields, is obtained for the subgrid-scale stress tensor. An analogous thermal linear combination model is also developed for the subgrid-scale heat flux vector. The two dimensionless constants associated with these subgrid-scale models are obtained by correlating with the results of direct numerical simulations of compressible isotropic turbulence performed on a 96(exp 3) grid using Fourier collocation methods. Extensive comparisons between the direct and modeled subgrid-scale fields are provided in order to validate the models. A large-eddy simulation of the decay of compressible isotropic turbulence (conducted on a coarse 32(exp 3) grid) is shown to yield results that are in excellent agreement with the fine grid direct simulation. Future applications of these compressible subgrid-scale models to the large-eddy simulation of more complex supersonic flows are discussed briefly.
Dynamic PIV measurement of a compressible flow issuing from an airbag inflator nozzle
NASA Astrophysics Data System (ADS)
Lee, Sang Joon; Jang, Young Gil; Kim, Seok; Kim, Chang Soo
2006-12-01
Among many equipment for passenger safety, the air bag system is the most fundamental and effective device for an automobile. The inflator housing is a main part of the curtain-type air bag system, which supplies high-pressure gases in pumping up the air bag-curtain which is increasingly being adapted in deluxe cars for protecting passengers from the danger of side clash. However, flow information on the inflator housing is very limited. In this study, we measure the instantaneous velocity fields of a high-speed compressible flow issuing from the exit nozzle of an inflator housing using a dynamic PIV system. From the velocity field data measured at a high frame-rate, we evaluate the variation of the mass flow rate with time. The dynamic PIV system consists of a high-repetition Nd:YLF laser, a high-speed CMOS camera, and a delay generator. The flow images are taken at 4000 fps with synchronization of the trigger signal for inflator ignition. From the instantaneous velocity field data of flow ejecting from the airbag inflator housing at the initial stage, we can see a flow pattern of broken shock wave front and its downward propagation. The flow ejecting from the inflator housing is found to have very high velocity fluctuations, with the maximum velocity at about 700 m/s. The time duration of the high-speed flow is very short, and there is no perceptible flow after 100 ms.
Assessment of chemistry models for compressible reacting flows
NASA Astrophysics Data System (ADS)
Lapointe, Simon; Blanquart, Guillaume
2014-11-01
Recent technological advances in propulsion and power devices and renewed interest in the development of next generation supersonic and hypersonic vehicles have increased the need for detailed understanding of turbulence-combustion interactions in compressible reacting flows. In numerical simulations of such flows, accurate modeling of the fuel chemistry is a critical component of capturing the relevant physics. Various chemical models are currently being used in reacting flow simulations. However, the differences between these models and their impacts on the fluid dynamics in the context of compressible flows are not well understood. In the present work, a numerical code is developed to solve the fully coupled compressible conservation equations for reacting flows. The finite volume code is based on the theoretical and numerical framework developed by Oefelein (Prog. Aero. Sci. 42 (2006) 2-37) and employs an all-Mach-number formulation with dual time-stepping and preconditioning. The numerical approach is tested on turbulent premixed flames at high Karlovitz numbers. Different chemical models of varying complexity and computational cost are used and their effects are compared.
A skin friction law for compressible turbulent flow
NASA Technical Reports Server (NTRS)
Barnwell, Richard W.; Wahls, Richard A.
1989-01-01
An algebraic skin friction law is derived for adiabatic, compressible, equilibrium, turbulent boundary layer flow. An outer solution in terms of the Clauser defect stream function is matched to an inner empirical expression composed of compressible laws of the wall and wake. The modified Crocco temperature-velocity relationship and the Clauser eddy viscousity model are used in the outer solution. The skin friction law pertains for all pressure gradients in the incompressible through supersonic range and for small pressure gradients in the hypersonic range. Excellent comparisons with experiment are obtained in the appropriate parameter ranges. The application to numerical computation is discussed.
Compressibility Corrections to Closure Approximations for Turbulent Flow Simulations
Cloutman, L D
2003-02-01
We summarize some modifications to the usual closure approximations for statistical models of turbulence that are necessary for use with compressible fluids at all Mach numbers. We concentrate here on the gradient-flu approximation for the turbulent heat flux, on the buoyancy production of turbulence kinetic energy, and on a modification of the Smagorinsky model to include buoyancy. In all cases, there are pressure gradient terms that do not appear in the incompressible models and are usually omitted in compressible-flow models. Omission of these terms allows unphysical rates of entropy change.
Analytical modeling of a hydraulically-compensated compressed-air energy-storage system
McMonagle, C.A.; Rowe, D.S.
1982-12-01
A computer program was developed to calculate the dynamic response of a hydraulically-compensated compressed air energy storage (CAES) system, including the compressor, air pipe, cavern, and hydraulic compensation pipe. The model is theoretically based on the two-fluid model in which the dynamics of each phase are presented by its set of conservation equations for mass and momentum. The conservation equations define the space and time distribution of pressure, void fraction, air saturation, and phase velocities. The phases are coupled by two interface equations. The first defines the rate of generation (or dissolution) of gaseous air in water and can include the effects of supersaturation. The second defines the frictional shear coupling (drag) between the gaseous air and water as they move relative to each other. The relative motion of the air and water is, therefore, calculated and not specified by a slip or drift-velocity correlation. The total CASE system is represented by a nodal arrangement. The conservation equations are written for each nodal volume and are solved numerically. System boundary conditions include the air flow rate, atmospheric pressure at the top of the compensation pipe, and air saturation in the reservoir. Initial conditions are selected for velocity and air saturation. Uniform and constant temperature (60/sup 0/F) is assumed. The analytical model was used to investigate the dynamic response of a proposed system.Investigative calculations considered high and low water levels, and a variety of charging and operating conditions. For all cases investigated, the cavern response to air-charging, was a damped oscillation of pressure and flow. Detailed results are presented. These calculations indicate that the Champagne Effect is unlikely to cause blowout for a properly designed CAES system.
Compressible potential flow around a helicopter rotor in arbitrary motion
NASA Astrophysics Data System (ADS)
Röttgermann, A.; Uhl, B.; Wagner, S.
1996-09-01
To consider compressible transonic flow effects a vortex lattice method for the computation of helicopter rotor flow is coupled with a field panel method. For this purpose Cartesian grids are used which are not adapted to the contour and only discretise the domain of the nonlinear flow. The basis of this procedure is the separation of the full potential equation into the Laplacian operator and the nonlinear terms. Several methods, including the panel-clustering technique are presented to reduce the computational effort of the method. The developed program ROFPM is validated at several experimental test cases of the Caradonna rotor.
A Two-Dimensional Compressible Gas Flow Code
Energy Science and Technology Software Center (ESTSC)
1995-03-17
F2D is a general purpose, two dimensional, fully compressible thermal-fluids code that models most of the phenomena found in situations of coupled fluid flow and heat transfer. The code solves momentum, continuity, gas-energy, and structure-energy equations using a predictor-correction solution algorithm. The corrector step includes a Poisson pressure equation. The finite difference form of the equation is presented along with a description of input and output. Several example problems are included that demonstrate the applicabilitymore » of the code in problems ranging from free fluid flow, shock tubes and flow in heated porous media.« less
Effects of Air-Fuel Spray and Flame Formation in a Compression-Ignition Engine
NASA Technical Reports Server (NTRS)
Rothrock, A M; Waldron, C D
1937-01-01
High-speed motion pictures were taken at the rate of 2,500 frames per second of the fuel spray and flame formation in the combustion chamber of the NACA combustion apparatus. The compression ratio was 13.2 and the speed 1,500 revolutions per minute. An optical indicator was used to record the time-pressure relationship in the combustion chamber. The air-fuel ratio was varied from 10.4 to 365. The results showed that as the air-fuel ratio was increased definite stratification of the charge occurred in the combustion chamber even though moderate air flow existed. The results also showed the rate of vapor diffusion to be relatively slow.
Finite element solver for 3-D compressible viscous flows
NASA Technical Reports Server (NTRS)
Reddy, K. C.; Reddy, J. N.
1986-01-01
The space shuttle main engine (SSME) has extremely complex internal flow structure. The geometry of the flow domain is three-dimensional with complicated topology. The flow is compressible, viscous, and turbulent with large gradients in flow quantities and regions of recirculations. The analysis of the flow field in SSME involves several tedious steps. One is the geometrical modeling of the particular zone of the SSME being studied. Accessing the geometry definition, digitalizing it, and developing surface interpolations suitable for an interior grid generator require considerable amount of manual labor. There are several types of grid generators available with some general-purpose finite element programs. An efficient and robust computational scheme for solving 3D Navier-Stokes equations has to be implemented. Post processing software has to be adapted to visualize and analyze the computed 3D flow field. The progress made in a project to develop software for the analysis of the flow is discussed. The technical approach to the development of the finite element scheme and the relaxation procedure are discussed. The three dimensional finite element code for the compressible Navier-Stokes equations is listed.
Compressed-air energy storage: Pittsfield aquifer field test
Bui, H.V.; Herzog, R.A.; Jacewicz, D.M.; Lange, G.R.; Scarpace, E.R.; Thomas, H.H. )
1990-02-01
This report documents the results of a comprehensive investigation into the practical feasibility for Compressed Air Energy Storage (CAES) in Porous Media. Natural gas porous media storage technology developed from seventy years of experience by the natural gas storage industry is applied to the investigation of CAES in porous media. A major objective of this investigation is the geologic characterization, deliverability prediction, and operations analysis of the Pittsfield CAES aquifer experiment, conducted in Pike County, Illinois during 1981--85 under EPRI/DOE sponsorship. Emphasis has been placed on applying accepted petroleum engineering concepts to the study of deliverability and on the characterization and quantification of oxygen losses which reportedly occurred at Pittsfield. Other objectives are to apply the natural gas underground storage technology and approach to a general study of CAES feasibility in porous media reservoirs, with emphasis on the practical risks and constraints of air storage in aquifer and depleted natural gas reservoirs, the effects of water on CAES operation, corrosion effects, and a review of air dehydration options.
Compression Shocks in Two-Dimensional Gas Flows
NASA Technical Reports Server (NTRS)
Busemann, A.
1949-01-01
The following are arguments on the compression shocks in gas flow start with a simplified representation of the results of the study made by Th. Meyer as published in the Forschungsheft 62 of the VDI, supplemented by several amplifications for the application.In the treatment of compression shocks, the equation of energy, the equation of continuity, the momentum equation, the equation of state of the particular gas, as well as the condition Of the second law of thermodynamics that no decrease of entropy is possible in an isolated system, must be taken into consideration. The result is that, in those cases where the sudden change of state according to the second law of thermodynamics is possible, there always occurs a compression of the gas which is uniquely determined by the other conditions.
Erikson, R.L.
1983-12-01
The long-term stability of a sandstone reservoir is of primary importance to the success of compressed air energy storage (CAES) in aquifers. The purpose of this study was to: develop experimental techniques for the operation of the CAES Porous Media Flow Loop (PMFL), an apparatus designed to study the stability of porous media in subsurface geologic environments, conduct experiments in the PMFL designed to determine the effects of temperature, stress, and humidity on the stability of candidate CAES reservoir materials, provide support for the CAES field demonstration project in Pittsfield, Illinois, by characterizing the thermophysical stability of Pittsfield reservoir sandstone under simulated field conditions.
Proceedings: Second international conference on compressed air energy storage
Not Available
1992-12-01
These proceedings provide documentation of the Second International Conference on Compressed-Air Energy Storage (CAES). Sponsored by EPRI and hosted by PG E, the conference was held July 7--9, 1992 in San Francisco. CAES topics for papers included: the first US CAES plant in McIntosh, Alabama; CAES turbomachinery and system components; geological considerations for storage in salt, porous-media, and rock formations; advanced CAES cycles; economic screening and evaluation software; environmental assessments; international projects; and US host-utility program results. There were 49 papers presented, with 125 attendees from 83 organization. Presentations included papers from Germany, Israel, Japan, Luxembourg, Norway, Sweden, the United Kingdom, and the United States. Individual papers are indexed separately.
Recent Research in Compression Refrigeration Cycle Air Source Heat Pumps.
NASA Astrophysics Data System (ADS)
Arai, Akira; Senshu, Takao
The most important theme for heat pump air conditioners is the improvement of energy saving and comfort. Recently, cycle components, especially compressores and heat exchangers have been improved greatly in their performance and efficiency. As for compressors, large progress in their efficiencies have been made by detailed analysises such as mechanical losses and by the development of a new type compression mechanism. As for heat exchangers, various high heat transfer surfaces have been developed together with the improvement of the production technologies for them. Further, the effect of the capacity-modulated cycle is evaluated quantitatively through the improvements of static and transient cycle simulation technologies. And in order to realize this cffect, the electrically driven expansion valves heve been marketed. This review introduces the trends of these energy-saving technologies as well as comfort improvement studies.
Compressive Earth observatory: An insight from AIRS/AMSU retrievals
NASA Astrophysics Data System (ADS)
Ebtehaj, Ardeshir M.; Foufoula-Georgiou, Efi; Lerman, Gilad; Bras, Rafael L.
2015-01-01
We demonstrate that the global fields of temperature, humidity, and geopotential heights admit a nearly sparse representation in the wavelet domain, offering a viable path forward to explore new paradigms of sparsity-promoting data assimilation and compressive recovery of land surface-atmospheric states from space. We illustrate this idea using retrieval products of the Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (AMSU) on board the Aqua satellite. The results reveal that the sparsity of the fields of temperature is relatively pressure independent, while atmospheric humidity and geopotential heights are typically sparser at lower and higher pressure levels, respectively. We provide evidence that these land-atmospheric states can be accurately estimated using a small set of measurements by taking advantage of their sparsity prior.
Unsteady compressible flows in channel with varying walls
NASA Astrophysics Data System (ADS)
Pořízková, P.; Kozel, K.; Horáček, J.
2014-03-01
This study deals with numerical solution of a 2D and 3D unsteady flows of a compressible viscous fluid in 2D and 3D channel for low inlet airflow velocity. The unsteadiness of the flow is caused by a prescribed periodic motion of a part of the channel wall, nearly closing the channel during oscillations. The channels shape is a simplified geometry of the glottal space in the human vocal tract. Goal is numerical simulation of flow in the channels which involves attributes of real flow causing acoustic perturbations. The system of Navier-Stokes equations closed with static pressure expression for ideal gas describes the unsteady laminar flow of compressible viscous fluid. The numerical solution is implemented using the finite volume method and the predictor-corrector MacCormack scheme with artificial viscosity using a grid of quadrilateral cells. The unsteady grid of quadrilateral cells is considered in the form of conservation laws using Arbitrary Lagrangian-Eulerian method. The application of developed method for numerical simulations of flow fields in the 2D and 3D channels, acquired from a developed program, are presented for inlet velocity u=4.12 m/s, inlet Reynolds number Re=4481 and the wall motion frequency 100 Hz.
Conjugate Compressible Fluid Flow and Heat Transfer in Ducts
NASA Technical Reports Server (NTRS)
Cross, M. F.
2011-01-01
A computational approach to modeling transient, compressible fluid flow with heat transfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heat transfer in solid propellant rocket motor nozzle joints during motor start-up, but the approach is relevant to a wide range of analyses involving rapid pressurization and filling of ducts. Fluid flow is modeled through solution of the spatially one-dimensional, transient Euler equations. Source terms are included in the governing equations to account for the effects of wall friction and heat transfer. The equation solver is fully-implicit, thus providing greater flexibility than an explicit solver. This approach allows for resolution of pressure wave effects on the flow as well as for fast calculation of the steady-state solution when a quasi-steady approach is sufficient. Solution of the one-dimensional Euler equations with source terms significantly reduces computational run times compared to general purpose computational fluid dynamics packages solving the Navier-Stokes equations with resolved boundary layers. In addition, conjugate heat transfer is more readily implemented using the approach described in this paper than with most general purpose computational fluid dynamics packages. The compressible flow code has been integrated with a transient heat transfer solver to analyze heat transfer between the fluid and surrounding structure. Conjugate fluid flow and heat transfer solutions are presented. The author is unaware of any previous work available in the open literature which uses the same approach described in this paper.
A multiple-scale model for compressible turbulent flows
NASA Technical Reports Server (NTRS)
Liou, William W.; Shih, Tsan-Hsing
1993-01-01
A multiple-scale model for compressible turbulent flows is proposed. It is assumed that turbulent eddy shocklets are formed primarily by the 'collisions' of large energetic eddies. The extra straining of the large eddy, due to their interactions with shocklets, enhances the energy cascade to smaller eddies. Model transport equations are developed for the turbulent kinetic energies and the energy transfer rates of the different scale. The turbulent eddy viscosity is determined by the total turbulent kinetic energy and the rate of energy transfer from the large scale to the small scale, which is different from the energy dissipation rate. The model coefficients in the modeled turbulent transport equations depend on the ratio of the turbulent kinetic energy of the large scale to that of the small scale, which renders the model more adaptive to the characteristics of individual flow. The model is tested against compressible free shear layers. The results agree satisfactorily with measurements.
Embedded function methods for compressible high speed turbulent flow
NASA Technical Reports Server (NTRS)
Walker, J. D. A.
1994-01-01
This is the final report on the work performed on the grant 'Embedded Function Methods for Compressible High Speed Turbulent Flow' carried out at Lehigh University during the contract period from September, 1987, to October of 1991. Work has continued at Lehigh on this project on an unfunded basis to the present. The original proposed work had two separate thrusts which were associated with developing embedded function methods in order to obviate the need to expend computational resources on turbulent wall layers in Navier Stokes and boundary-layer calculations. Previous work on the incompressible problem had indicated that this could be done successfully for two-dimensional and three-dimensional incompressible flows. The central objective here was to extend the basic approach to the high speed compressible problem.
Tollmien-Schlichting/vortex interactions in compressible boundary layer flows
NASA Technical Reports Server (NTRS)
Blackaby, Nicholas D.
1993-01-01
The weakly nonlinear interaction of oblique Tollmien-Schlichting waves and longitudinal vortices in compressible, high Reynolds number, boundary-layer flow over a flat plate is considered for all ranges of the Mach number. The interaction equations comprise of equations for the vortex which is indirectly forced by the waves via a boundary condition, whereas a vortex term appears in the amplitude equation for the wave pressure. The downstream solution properties of interaction equations are found to depend on the sign of an interaction coefficient. Compressibility is found to have a significant effect on the interaction properties; principally through its impact on the waves and their governing mechanism, the triple-deck structure. It is found that, in general, the flow quantities will grow slowly with increasing downstream co-ordinate; i.e. in general, solutions do not terminate in abrupt, finite-distance 'break-ups'.
Compressible, turbulent flow computation and drag optimization for axisymmetric afterbodies
NASA Astrophysics Data System (ADS)
Cummings, Russell Mark
A new parallel implicit adaptive mesh refinement (AMR) algorithm is developed for the prediction of unsteady behaviour of laminar flames. The scheme is applied to the solution of the system of partial-differential equations governing time-dependent, two- and three-dimensional, compressible laminar flows for reactive thermally perfect gaseous mixtures. A high-resolution finite-volume spatial discretization procedure is used to solve the conservation form of these equations on body-fitted multi-block hexahedral meshes. A local preconditioning technique is used to remove numerical stiffness and maintain solution accuracy for low-Mach-number, nearly incompressible flows. A flexible block-based octree data structure has been developed and is used to facilitate automatic solution-directed mesh adaptation according to physics-based refinement criteria. The data structure also enables an efficient and scalable parallel implementation via domain decomposition. The parallel implicit formulation makes use of a dual-time-stepping like approach with an implicit second-order backward discretization of the physical time, in which a Jacobian-free inexact Newton method with a preconditioned generalized minimal residual (GMRES) algorithm is used to solve the system of nonlinear algebraic equations arising from the temporal and spatial discretization procedures. An additive Schwarz global preconditioner is used in conjunction with block incomplete LU type local preconditioners for each sub-domain. The Schwarz preconditioning and block-based data structure readily allow efficient and scalable parallel implementations of the implicit AMR approach on distributed-memory multi-processor architectures. The scheme was applied to solutions of steady and unsteady laminar diffusion and premixed methane-air combustion and was found to accurately predict key flame characteristics. For a premixed flame under terrestrial gravity, the scheme accurately predicted the frequency of the natural
Solution of Reactive Compressible Flows Using an Adaptive Wavelet Method
NASA Astrophysics Data System (ADS)
Zikoski, Zachary; Paolucci, Samuel; Powers, Joseph
2008-11-01
This work presents numerical simulations of reactive compressible flow, including detailed multicomponent transport, using an adaptive wavelet algorithm. The algorithm allows for dynamic grid adaptation which enhances our ability to fully resolve all physically relevant scales. The thermodynamic properties, equation of state, and multicomponent transport properties are provided by CHEMKIN and TRANSPORT libraries. Results for viscous detonation in a H2:O2:Ar mixture, and other problems in multiple dimensions, are included.
Simulator Of Rain In Flowing Air
NASA Technical Reports Server (NTRS)
Clayton, Richard M.; Cho, Young I.; Shakkottai, Parthasarathy; Back, Lloyd H.
1989-01-01
Report describes relatively inexpensive apparatus that creates simulated precipitation from drizzle to heavy rain in flowing air. Small, positive-displacement pump and water-injecting device positioned at low-airspeed end of converging section of wind tunnel 10 in. in diameter. Drops injected by array entrained in flow of air as it accelerates toward narrower outlet, 15 in. downstream. Outlet 5 in. in diameter.
Investigation of Compressibility Effect for Aeropropulsive Shear Flows
NASA Technical Reports Server (NTRS)
Balasubramanyam, M. S.; Chen, C. P.
2005-01-01
Rocket Based Combined Cycle (RBCC) engines operate within a wide range of Mach numbers and altitudes. Fundamental fluid dynamic mechanisms involve complex choking, mass entrainment, stream mixing and wall interactions. The Propulsion Research Center at the University of Alabama in Huntsville is involved in an on- going experimental and numerical modeling study of non-axisymmetric ejector-based combined cycle propulsion systems. This paper attempts to address the modeling issues related to mixing, shear layer/wall interaction in a supersonic Strutjet/ejector flow field. Reynolds Averaged Navier-Stokes (RANS) solutions incorporating turbulence models are sought and compared to experimental measurements to characterize detailed flow dynamics. The effect of compressibility on fluids mixing and wall interactions were investigated using an existing CFD methodology. The compressibility correction to conventional incompressible two- equation models is found to be necessary for the supersonic mixing aspect of the ejector flows based on 2-D simulation results. 3-D strut-base flows involving flow separations were also investigated.
Compressive high speed flow microscopy with motion contrast (Conference Presentation)
NASA Astrophysics Data System (ADS)
Bosworth, Bryan; Stroud, Jasper R.; Tran, Dung N.; Tran, Trac D.; Chin, Sang; Foster, Mark A.
2016-03-01
High-speed continuous imaging systems are constrained by analog-to-digital conversion, storage, and transmission. However, real video signals of objects such as microscopic cells and particles require only a few percent or less of the full video bandwidth for high fidelity representation by modern compression algorithms. Compressed Sensing (CS) is a recent influential paradigm in signal processing that builds real-time compression into the acquisition step by computing inner products between the signal of interest and known random waveforms and then applying a nonlinear reconstruction algorithm. Here, we extend the continuous high-rate photonically-enabled compressed sensing (CHiRP-CS) framework to acquire motion contrast video of microscopic flowing objects. We employ chirp processing in optical fiber and high-speed electro-optic modulation to produce ultrashort pulses each with a unique pseudorandom binary sequence (PRBS) spectral pattern with 325 features per pulse at the full laser repetition rate (90 MHz). These PRBS-patterned pulses serve as random structured illumination inside a one-dimensional (1D) spatial disperser. By multiplexing the PRBS patterns with a user-defined repetition period, the difference signal y_i=&phi_i (x_i - x_{i-tau}) can be computed optically with balanced detection, where x is the image signal, phi_i is the PRBS pattern, and tau is the repetition period of the patterns. Two-dimensional (2D) image reconstruction via iterative alternating minimization to find the best locally-sparse representation yields an image of the edges in the flow direction, corresponding to the spatial and temporal 1D derivative. This provides both a favorable representation for image segmentation and a sparser representation for many objects that can improve image compression.
On the linear stability of compressible plane Couette flow
NASA Technical Reports Server (NTRS)
Duck, Peter W.; Erlebacher, Gordon; Hussaini, M. Yousuff
1991-01-01
The linear stability of compressible plane Couette flow is investigated. The correct and proper basic velocity and temperature distributions are perturbed by a small amplitude normal mode disturbance. The full small amplitude disturbance equations are solved numerically at finite Reynolds numbers, and the inviscid limit of these equations is then investigated in some detail. It is found that instability can occur, although the stability characteristics of the flow are quite different from unbounded flows. The effects of viscosity are also calculated, asymptotically, and shown to have a stabilizing role in all the cases investigated. Exceptional regimes to the problem occur when the wavespeed of the disturbances approaches the velocity of either of the walls, and these regimes are also analyzed in some detail. Finally, the effect of imposing radiation-type boundary conditions on the upper (moving) wall (in place of impermeability) is investigated, and shown to yield results common to both bounded and unbounded flows.
NASA Astrophysics Data System (ADS)
Mizrahi, Guy; Weisbrod, Noam; Furman, Alex
2015-04-01
Entrapped air effects on infiltration under ponding conditions could be important for massive infiltration of managed aquifer recharge (MAR) or soil aquifer treatment (SAT) of treated wastewater. Earlier studies found that under ponding conditions, air is being entrapped and compressed until it reaches a pressure which will enable the air to escape (unstable air flow). They also found that entrapped air could reduce infiltration by 70-90%. Most studies have dealt with entrapped air effects when soil surface topography is flat. The objective of this study is to investigate, under ponding conditions, the effects of: (1) irregular surface topography on preferential air flow path development (stable air flow); (2) preferential air flow path on infiltration; and (3) hydraulic head on infiltration when air is trapped. Column experiments were used to investigate these particular effects. A 140 cm deep and 30 cm wide column packed with silica sand was used under two boundary conditions: in the first, air can only escape vertically upward through the soil surface; in the second, air is free to escape through 20 ports installed along the column perimeter. The surface was flooded with 13 liters of water, with ponding depth decreasing with time. Two soil surface conditions were tested: flat surface and irregular surface (high and low surface zones). Additionally, Helle-show experiments were conducted in order to obtain a visual observation of preferential air flow path development. The measurements were carried out using a tension meter, air pressure transducers, TDR and video cameras. It was found that in irregular surfaces, stable air flow through preferential paths was developed in the high altitude zones. Flat surface topography caused unstable air flow through random paths. Comparison between irregular and flat surface topography showed that the entrapped air pressure was lower and the infiltration rate was about 40% higher in the irregular surface topography than in the
Viscous and gravitational fingering in multiphase compositional and compressible flow
NASA Astrophysics Data System (ADS)
Moortgat, Joachim
2016-03-01
Viscous and gravitational fingering refer to flow instabilities in porous media that are triggered by adverse mobility or density ratios, respectively. These instabilities have been studied extensively in the past for (1) single-phase flow (e.g., contaminant transport in groundwater, first-contact-miscible displacement of oil by gas in hydrocarbon production), and (2) multi-phase immiscible and incompressible flow (e.g., water-alternating-gas (WAG) injection in oil reservoirs). Fingering in multiphase compositional and compressible flow has received much less attention, perhaps due to its high computational complexity. However, many important subsurface processes involve multiple phases that exchange species. Examples are carbon sequestration in saline aquifers and enhanced oil recovery (EOR) by gas or WAG injection below the minimum miscibility pressure. In multiphase flow, relative permeabilities affect the mobility contrast for a given viscosity ratio. Phase behavior can also change local fluid properties, which can either enhance or mitigate viscous and gravitational instabilities. This work presents a detailed study of fingering behavior in compositional multiphase flow in two and three dimensions and considers the effects of (1) Fickian diffusion, (2) mechanical dispersion, (3) flow rates, (4) domain size and geometry, (5) formation heterogeneities, (6) gravity, and (7) relative permeabilities. Results show that fingering in compositional multiphase flow is profoundly different from miscible conditions and upscaling techniques used for the latter case are unlikely to be generalizable to the former.
Air flow cued spatial learning in mice.
Bouchekioua, Youcef; Mimura, Masaru; Watanabe, Shigeru
2015-01-01
Spatial learning experiments in rodents typically employ visual cues that are associated with a goal place, even though it is now well established that they have poor visual acuity. We assessed here the possibility of spatial learning in mice based on an air flow cue in a dry version of the Morris water maze task. A miniature fan was placed at each of the four cardinal points of the circular maze, but only one blew air towards the centre of the maze. The three other fans were blowing towards their own box. The mice were able to learn the task only if the spatial relationship between the air flow cue and the position of the goal place was kept constant across trials. A change of this spatial relationship resulted in an increase in the time to find the goal place. We report here the first evidence of spatial learning relying on an air flow cue. PMID:25257773
Long-wave linear stability theory for two-fluid channel flow including compressibility effects
NASA Astrophysics Data System (ADS)
Segin, Tetyana M.; Kondic, Lou; Tilley, Burt S.
2006-10-01
We present the linear stability of the laminar flow of an immiscible system of a compressible gas and incompressible liquid separated by an interface with large surface tension in a thin inclined channel. The flow is driven by an applied pressure drop and gravity. Following the air-water case, which is found in a variety of engineering systems, the ratio of the characteristic values of the gas and liquid densities and viscosities are assumed to be disparate. Under the lubrication approximation, and assuming ideal gas behaviour and isothermal conditions, this approach leads to a coupled non-linear system of partial differential equations describing the evolution of the interface between the gas and the liquid and the streamwise density distribution of the gas. This system also includes the effects of viscosity stratification, inertia, shear and capillarity. A linear stability analysis that allows for physically relevant non-zero pressure-drop base state is then performed. In contrast to the zero-pressure drop case which is amenable to the classical normal-mode approach, this configuration requires numerically solving a boundary-value problem for the gas density and interfacial deviations from the base state in the streamwise coordinate. We find that the effect of the gas compressibility on the interfacial stability in the limit of vanishingly small wavenumber is destabilizing, even for Stokes flow in the liquid. However, for finite wavenumber disturbances, compressibility may have stabilizing effects. In this regime, sufficient shear is required to destabilize the flow.
Three-dimensional lattice Boltzmann model for compressible flows.
Sun, Chenghai; Hsu, Andrew T
2003-07-01
A three-dimensional compressible lattice Boltzmann model is formulated on a cubic lattice. A very large particle-velocity set is incorporated in order to enable a greater variation in the mean velocity. Meanwhile, the support set of the equilibrium distribution has only six directions. Therefore, this model can efficiently handle flows over a wide range of Mach numbers and capture shock waves. Due to the simple form of the equilibrium distribution, the fourth-order velocity tensors are not involved in the formulation. Unlike the standard lattice Boltzmann model, no special treatment is required for the homogeneity of fourth-order velocity tensors on square lattices. The Navier-Stokes equations were recovered, using the Chapman-Enskog method from the Bhatnagar-Gross-Krook (BGK) lattice Boltzmann equation. The second-order discretization error of the fluctuation velocity in the macroscopic conservation equation was eliminated by means of a modified collision invariant. The model is suitable for both viscous and inviscid compressible flows with or without shocks. Since the present scheme deals only with the equilibrium distribution that depends only on fluid density, velocity, and internal energy, boundary conditions on curved wall are easily implemented by an extrapolation of macroscopic variables. To verify the scheme for inviscid flows, we have successfully simulated a three-dimensional shock-wave propagation in a box and a normal shock of Mach number 10 over a wedge. As an application to viscous flows, we have simulated a flat plate boundary layer flow, flow over a cylinder, and a transonic flow over a NACA0012 airfoil cascade. PMID:12935242
Air flow through poppet valves
NASA Technical Reports Server (NTRS)
Lewis, G W; Nutting, E M
1920-01-01
Report discusses the comparative continuous flow characteristics of single and double poppet valves. The experimental data presented affords a direct comparison of valves, single and in pairs of different sizes, tested in a cylinder designed in accordance with current practice in aviation engines.
Viscous compressible flow direct and inverse computation and illustrations
NASA Technical Reports Server (NTRS)
Yang, T. T.; Ntone, F.
1986-01-01
An algorithm for laminar and turbulent viscous compressible two dimensional flows is presented. For the application of precise boundary conditions over an arbitrary body surface, a body-fitted coordinate system is used in the physical plane. A thin-layer approximation of tne Navier-Stokes equations is introduced to keep the viscous terms relatively simple. The flow field computation is performed in the transformed plane. A factorized, implicit scheme is used to facilitate the computation. Sample calculations, for Couette flow, developing pipe flow, an isolated airflow, two dimensional compressor cascade flow, and segmental compressor blade design are presented. To a certain extent, the effective use of the direct solver depends on the user's skill in setting up the gridwork, the time step size and the choice of the artificial viscosity. The design feature of the algorithm, an iterative scheme to correct geometry for a specified surface pressure distribution, works well for subsonic flows. A more elaborate correction scheme is required in treating transonic flows where local shock waves may be involved.
Water droplet evaporation in air during compression in a gas turbine engine. Technical memo
Quandt, E.
1996-04-01
A water fog concept is being considered for evaporative cooling of the air as it is compressed in a ship gas turbine engine. The following analysis is presented to clarify the physics associated with liquid droplet evaporation in this situation, to understand the conditions affecting the cooling, and to identify any further information required to achieve such a concept. The vaporization of small liquid drops in a warm ideal gas is controlled by the outward motion of the vapor and the inward flow of heat to cause evaporation. Following the standard analysis of Spalding, as given in `Principles of Combustion` by Kuo, it is assumed that the process is `quasi steady.` This means that the conditions far removed from the drop are constant, and that there are no time varying terms in the Eulerian description of the mass and energy flows.
Harold Schock; Farhad Jaberi; Ahmed Naguib; Guoming Zhu; David Hung
2007-12-31
This report describes the work completed over a two and one half year effort sponsored by the US Department of Energy. The goal was to demonstrate the technology needed to produce a highly efficient engine enabled by several technologies which were to be developed in the course of the work. The technologies included: (1) A low-pressure direct injection system; (2) A mass air flow sensor which would measure the net airflow into the engine on a per cycle basis; (3) A feedback control system enabled by measuring ionization current signals from the spark plug gap; and (4) An infinitely variable cam actuation system based on a pneumatic-hydraulic valve actuation These developments were supplemented by the use of advanced large eddy simulations as well as evaluations of fuel air mixing using the KIVA and WAVE models. The simulations were accompanied by experimental verification when possible. In this effort a solid base has been established for continued development of the advanced engine concepts originally proposed. Due to problems with the valve actuation system a complete demonstration of the engine concept originally proposed was not possible. Some of the highlights that were accomplished during this effort are: (1) A forward-backward mass air flow sensor has been developed and a patent application for the device has been submitted. We are optimistic that this technology will have a particular application in variable valve timing direct injection systems for IC engines. (2) The biggest effort on this project has involved the development of the pneumatic-hydraulic valve actuation system. This system was originally purchased from Cargine, a Swedish supplier and is in the development stage. To date we have not been able to use the actuators to control the exhaust valves, although the actuators have been successfully employed to control the intake valves. The reason for this is the additional complication associated with variable back pressure on the exhaust valves when
Thermodynamic considerations in the numerical simulation of steady compressible flow
NASA Astrophysics Data System (ADS)
Thyagaraja, A.
1980-03-01
The notion of thermodynamic consistency of a finite difference scheme is introduced in connection with steady compressible flow simulation. This concept requires that the finite difference scheme must lead to solutions which are consistent with the Second Law of Thermodynamics, whatever the grid sizes employed. Thus, in addition to the usual consistency with the conservation equations of mass, momentum and energy, the solutions of the finite difference equations must satisfy thermodynamic restrictions. The scheme proposed by Singhal and Spalding for the computation of plane, isentropic flow is generalized in a thermodynamically consistent way to handle inviscid, adiabatic but nonisentropic plane flow. Numerical solutions are obtained for a model problem using both the original and the extended methods. The results are compared with analytical predictions of shock-expansion theory. The effectiveness and the thermodynamic consistency of the new formulation is demonstrated.
Achieving acoustic cloak by using compressible background flow
NASA Astrophysics Data System (ADS)
Zhang, Ruo-Yang; Zhao, Qing; Ge, Mo-Lin
2016-08-01
We propose a scheme of acoustic spherical cloaking by means of background irrotational flow in compressible fluid. The background flow forms a virtual curved spacetime and directs the sound waves to bypass the cloaked objects. To satisfy the laws of real fluid, we show that spatially distributed mass source and momentum source are necessary to supply. The propagation of sound waves in this system is studied via both geometric acoustics approximation and full wave approach. The analytic solution of sound fields is obtained for plane wave incidence. The results reveal the effect of phase retardation (or lead) in comparison with the ordinary transformation-acoustic cloak. In addition, the ability of cloaking is also evaluated for unideal background flows by analyzing the scattering cross section. Project supported by the National Natural Science Foundation of China (Grant Nos. 11475088 and 11275024) and the Fund from the Ministry of Science and Technology of China (Grant No. 2013YQ030595-3).
Optical phase distortion due to compressible flow over laser turrets
NASA Technical Reports Server (NTRS)
Fuhs, A. E.; Fuhs, S. E.
1980-01-01
Analytical models for optical phase distortion due to compressible flow over a laser turret are developed. Phase distortion is calculated for both blunt and small perturbation turrets. For the blunt turret, the Janzen-Rayleigh technique is used to determine the flow field. Phase distortions of 2.2 wavelengths at 3.8 microns are calculated for the blunt turret. For small perturbation turrets, a versatile analytical model is developed for a turret on a fuselage with circular cross section. With a two dimensional Fourier series representation of the turret, any shape can be considered. Both subsonic and supersonic flows can be calculated. Phase distortions of 1.2 wavelengths at 3.8 microns are calculated for one turret at high subsonic Mach number. In addition to being of value for laser turrets, the methods are applicable to reconnaissance aircraft using photographic equipment and cruise missiles using celestial navigation.
A real-time interferometer technique for compressible flow research
NASA Technical Reports Server (NTRS)
Bachalo, W. D.; Houser, M. J.
1984-01-01
Strengths and shortcomings in the application of interferometric techniques to transonic flow fields are examined and an improved method is elaborated. Such applications have demonstrated the value of interferometry in obtaining data for compressible flow research. With holographic techniques, interferometry may be applied in large scale facilities without the use of expensive optics or elaborate vibration isolation equipment. Results obtained using holographic interferometry and other methods demonstrate that reliable qualitative and quantitative data can be acquired. Nevertheless, the conventional method can be difficult to set up and apply, and it cannot produce real-time data. A new interferometry technique is investigated that promises to be easier to apply and can provide real-time information. This single-beam technique has the necessary insensitivity to vibration for large scale wind tunnel operations. Capabilities of the method and preliminary tests on some laboratory scale flow fluids are described.
Rutqvist, J.; Kim, H. -M.; Ryu, D. -W.; Synn, J. -H.; Song, W. -K.
2012-02-01
We applied coupled nonisothermal, multiphase fluid flow and geomechanical numerical modeling to study the coupled thermodynamic and geomechanical performance of underground compressed air energy storage (CAES) in concrete-lined rock caverns. The paper focuses on CAES in lined caverns at relatively shallow depth (e.g., 100 m depth) in which a typical CAES operational pressure of 5 to 8 MPa is significantly higher than both ambient fluid pressure and in situ stress. We simulated a storage operation that included cyclic compression and decompression of air in the cavern, and investigated how pressure, temperature and stress evolve over several months of operation. We analyzed two different lining options, both with a 50 cm thick low permeability concrete lining, but in one case with an internal synthetic seal such as steel or rubber. For our simulated CAES system, the thermodynamic analysis showed that 96.7% of the energy injected during compression could be recovered during subsequent decompression, while 3.3% of the energy was lost by heat conduction to the surrounding media. Our geomechanical analysis showed that tensile effective stresses as high as 8 MPa could develop in the lining as a result of the air pressure exerted on the inner surface of the lining, whereas thermal stresses were relatively smaller and compressive. With the option of an internal synthetic seal, the maximum effective tensile stress was reduced from 8 to 5 MPa, but was still in substantial tension. We performed one simulation in which the tensile tangential stresses resulted in radial cracks and air leakage though the lining. This air leakage, however, was minor (about 0.16% of the air mass loss from one daily compression) in terms of CAES operational efficiency, and did not significantly impact the overall energy balance of the system. However, despite being minor in terms of energy balance, the air leakage resulted in a distinct pressure increase in the surrounding rock that could be
Integration of Wind Turbines with Compressed Air Energy Storage
NASA Astrophysics Data System (ADS)
Arsie, I.; Marano, V.; Rizzo, G.; Moran, M.
2009-08-01
Some of the major limitations of renewable energy sources are represented by their low power density and intermittent nature, largely depending upon local site and unpredictable weather conditions. These problems concur to increase the unit costs of wind power, so limiting their diffusion. By coupling storage systems with a wind farm, some of the major limitations of wind power, such as a low power density and an unpredictable nature, can be overcome. After an overview on storage systems, the Compressed Air Energy Storage (CAES) is analyzed, and the state of art on such systems is discussed. A Matlab/Simulink model of a hybrid power plant consisting of a wind farm coupled with CAES is then presented. The model has been successfully validated starting from the operating data of the McIntosh CAES Plant in Alabama. Time-series neural network-based wind speed forecasting are employed to determine the optimal daily operation strategy for the storage system. A detailed economic analysis has been carried out: investment and maintenance costs are estimated based on literature data, while operational costs and revenues are calculated according to energy market prices. As shown in the paper, the knowledge of the expected available energy is a key factor to optimize the management strategies of the proposed hybrid power plant, allowing to obtain environmental and economic benefits.
Pencil: Finite-difference Code for Compressible Hydrodynamic Flows
NASA Astrophysics Data System (ADS)
Brandenburg, Axel; Dobler, Wolfgang
2010-10-01
The Pencil code is a high-order finite-difference code for compressible hydrodynamic flows with magnetic fields. It is highly modular and can easily be adapted to different types of problems. The code runs efficiently under MPI on massively parallel shared- or distributed-memory computers, like e.g. large Beowulf clusters. The Pencil code is primarily designed to deal with weakly compressible turbulent flows. To achieve good parallelization, explicit (as opposed to compact) finite differences are used. Typical scientific targets include driven MHD turbulence in a periodic box, convection in a slab with non-periodic upper and lower boundaries, a convective star embedded in a fully nonperiodic box, accretion disc turbulence in the shearing sheet approximation, self-gravity, non-local radiation transfer, dust particle evolution with feedback on the gas, etc. A range of artificial viscosity and diffusion schemes can be invoked to deal with supersonic flows. For direct simulations regular viscosity and diffusion is being used. The code is written in well-commented Fortran90.
A finite element solver for 3-D compressible viscous flows
NASA Technical Reports Server (NTRS)
Reddy, K. C.; Reddy, J. N.; Nayani, S.
1990-01-01
Computation of the flow field inside a space shuttle main engine (SSME) requires the application of state of the art computational fluid dynamic (CFD) technology. Several computer codes are under development to solve 3-D flow through the hot gas manifold. Some algorithms were designed to solve the unsteady compressible Navier-Stokes equations, either by implicit or explicit factorization methods, using several hundred or thousands of time steps to reach a steady state solution. A new iterative algorithm is being developed for the solution of the implicit finite element equations without assembling global matrices. It is an efficient iteration scheme based on a modified nonlinear Gauss-Seidel iteration with symmetric sweeps. The algorithm is analyzed for a model equation and is shown to be unconditionally stable. Results from a series of test problems are presented. The finite element code was tested for couette flow, which is flow under a pressure gradient between two parallel plates in relative motion. Another problem that was solved is viscous laminar flow over a flat plate. The general 3-D finite element code was used to compute the flow in an axisymmetric turnaround duct at low Mach numbers.
The treatment of convected vortices in compressible potential flow
NASA Technical Reports Server (NTRS)
Steinhoff, J.; Ramachandran, K.; Suryanarayanan, K.
1983-01-01
A method is described for incorporating line vortices into the three dimensional compressible potential flow equation. A modified Biot-Savart law is used to compute a vortical velocity field, which is added to the gradient of the potential to form a total velocity. A rapidly converging approximate factorization (AFZ) scheme is then used to compute a potential such that the modified potential flow equation as well as the appropriate boundary conditions, based on total velocity, are satisfied. As part of a coupled iteration procedure, the positions of the line vortices are computed so that they convect with the total flow. The method is used to compute the field due to a single line vortex convecting past a wing. This represents an approximation of the effect of a canard or other lifting surface ahead of the wing, which sheds a tip vortex. It is seen that the flow field is substantially modified by the passage of the vortex. Unlike Euler equation schemes, which are also used to compute these flows, the solutions exhibit no numerical diffusion: The convected vortices retain their initial upstream width. Euler solutions, on the other hand, involve a vorticity which is numerically convected in an Eulerian frame and, unless extensive adaptive grid refinement is used they result in vortices with spread as they convect. Also, the potential flow method requires approximately two orders of magnitude less computing time and much less computer storage than the Euler methods.
40 CFR 91.416 - Intake air flow measurement specifications.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Intake air flow measurement... Procedures § 91.416 Intake air flow measurement specifications. (a) If used, the engine intake air flow measurement method used must have a range large enough to accurately measure the air flow over the...
Simple numerical method for predicting steady compressible flows
NASA Technical Reports Server (NTRS)
Vonlavante, Ernst; Nelson, N. Duane
1986-01-01
A numerical method for solving the isenthalpic form of the governing equations for compressible viscous and inviscid flows was developed. The method was based on the concept of flux vector splitting in its implicit form. The method was tested on several demanding inviscid and viscous configurations. Two different forms of the implicit operator were investigated. The time marching to steady state was accelerated by the implementation of the multigrid procedure. Its various forms very effectively increased the rate of convergence of the present scheme. High quality steady state results were obtained in most of the test cases; these required only short computational times due to the relative efficiency of the basic method.
Two-dimensional subsonic compressible flow past elliptic cylinders
NASA Technical Reports Server (NTRS)
Kaplan, Carl
1938-01-01
The method of Poggi is used to calculate, for perfect fluids, the effect of compressibility upon the flow on the surface of an elliptic cylinder at zero angle of attack and with no circulation. The result is expressed in a closed form and represents a rigorous determination of the velocity of the fluid at the surface of the obstacle insofar as the second approximation is concerned. Comparison is made with Hooker's treatment of the same problem according to the method of Janzen and Rayleight and it is found that, for thick elliptic cylinders, the two methods agree very well. The labor of computation is considerably reduced by the present solution.
Pseudo-compressibility methods for the incompressible flow equations
NASA Technical Reports Server (NTRS)
Turkel, Eli; Arnone, A.
1993-01-01
Preconditioning methods to accelerate convergence to a steady state for the incompressible fluid dynamics equations are considered. The analysis relies on the inviscid equations. The preconditioning consists of a matrix multiplying the time derivatives. Thus the steady state of the preconditioned system is the same as the steady state of the original system. The method is compared to other types of pseudo-compressibility. For finite difference methods preconditioning can change and improve the steady state solutions. An application to viscous flow around a cascade with a non-periodic mesh is presented.
Scalar/Vector potential formulation for compressible viscous unsteady flows
NASA Technical Reports Server (NTRS)
Morino, L.
1985-01-01
A scalar/vector potential formulation for unsteady viscous compressible flows is presented. The scalar/vector potential formulation is based on the classical Helmholtz decomposition of any vector field into the sum of an irrotational and a solenoidal field. The formulation is derived from fundamental principles of mechanics and thermodynamics. The governing equations for the scalar potential and vector potential are obtained, without restrictive assumptions on either the equation of state or the constitutive relations or the stress tensor and the heat flux vector.
Coherent structures in compressible free-shear-layer flows
Aeschliman, D.P.; Baty, R.S.; Kennedy, C.A.; Chen, J.H.
1997-08-01
Large scale coherent structures are intrinsic fluid mechanical characteristics of all free-shear flows, from incompressible to compressible, and laminar to fully turbulent. These quasi-periodic fluid structures, eddies of size comparable to the thickness of the shear layer, dominate the mixing process at the free-shear interface. As a result, large scale coherent structures greatly influence the operation and efficiency of many important commercial and defense technologies. Large scale coherent structures have been studied here in a research program that combines a synergistic blend of experiment, direct numerical simulation, and analysis. This report summarizes the work completed for this Sandia Laboratory-Directed Research and Development (LDRD) project.
Visualization, Extraction and Quantification of Discontinuities in Compressible Flows
NASA Technical Reports Server (NTRS)
Samtaney, Ravi; Morris, R. D.; Cheeseman, P.; Sunelyansky, V.; Maluf, D.; Wolf, D.
2000-01-01
Scientific visualizations of two-dimensional compressible flow of a gas with discontinuities are presented. The numerical analogue to experimental techniques such as schlieren imaging, shadowgraphs, and interferograms are discussed. Edge detection techniques are utilized to identify the discontinuities. In particular, the zero crossing of the Laplacian of a field (usually density) is recommended for extracting the discontinuities. An algorithm to extract and quantify the discontinuities is presented. To illustrate the methods developed in the report, the example chosen is that of an unsteady interaction of a shock wave with a contact discontinuity.
Efficacy of Micromobile Foot Compression Device in Increasing Lower Limb Venous Blood Flow
Weatherall, Mark
2013-01-01
Background. A novel, micromobile foot compression device (MMC) has been developed to reduce the risk of venous thromboembolism associated with prolonged seated immobility. Objective. To compare the efficacy of the MMC with graduated compression stockings in augmenting lower limb venous blood flow. Patients/Methods. Twenty participants were randomised to wear the MMC or a graduated compression stocking (GCS) on either the left or right leg while seated. Doppler ultrasound measurements of popliteal vein blood flow and leg circumference measurements were made −30 and −10 minutes (baseline) and +30 and +60 minutes following application of the interventions. The primary outcome variable was peak systolic velocity. A mixed linear model was used, with covariates including baseline measurement, randomised side, time, and a time by interaction term. Results. The mean popliteal vein peak systolic velocity at 60 minutes with the MMC was 20.1 cm/s which was significantly higher than with the GCS (difference 14.1 cm/s 95% CI 12.1–16.2), representing a 3.8-fold increase from baseline. Conclusion. The MMC resulted in a marked increase in lower limb venous blood flow which suggests that it may have efficacy in reducing the risk of venous thromboembolism associated with prolonged seated immobility, such as long distance air travel. PMID:24319596
Three dimensional inviscid compressible calculations around axial flow turbine blades
NASA Astrophysics Data System (ADS)
Fourmaux, Antoine; Petot, Bertrand
1991-12-01
The application of a three dimensional (3D) method to the prediction of steady inviscid compressible flows in highly loaded stator bladings is presented. The complete set of Euler equations is solved by a finite difference method using a time marching two step Lax-Wendorff algorithm. The treatment of the boundary conditions is based on the use of the characteristic relations. This technique offers a great versatility and allows to prescribe conditions close to the physics of flows encountered in turbomachines. The code was adapted in order to build a 3D design tool able to run in different types of turbine blade geometries. Two types of multidomain structured meshes were tested (H+0+H and H+C). The H+C type of grid was finally choosen for industrial applications. Two applications to turbine nozzles are presented. The first is a low pressure turbine vane with evolutive flow path outer diameter. The results demonstrate the ability to predict flow features that cannot be computed via the classical two dimensional approach. The second is a high pressure inlet guide vane at transonic conditions. The strong radial evolution of pressure distribution and the trailing edge flow pattern are correctly predicted.
Numerical modeling of a compressible multiphase flow through a nozzle
NASA Astrophysics Data System (ADS)
Niedzielska, Urszula; Rabinovitch, Jason; Blanquart, Guillaume
2012-11-01
New thermodynamic cycles developed for more efficient low temperature resource utilization can increase the net power production from geothermal resources and sensible waste heat recovery by 20-40%, compared to the traditional organic Rankine cycle. These improved systems consist of a pump, a liquid heat exchanger, a two-phase turbine, and a condenser. The two-phase turbine is used to extract energy from a high speed multiphase fluid and consists of a nozzle and an axial impulse rotor. In order to model and optimize the fluid flow through this part of the system an analysis of two-phase flow through a specially designed convergent-divergent nozzle has to be conducted. To characterize the flow behavior, a quasi-one-dimensional steady-state model of the multiphase fluid flow through a nozzle has been constructed. A numerical code capturing dense compressible multiphase flow under subsonic and supersonic conditions and the coupling between both liquid and gas phases has been developed. The output of the code delivers data vital for the performance optimization of the two-phase nozzle.
Thermodynamic analysis of five compressed-air energy-storage cycles. [Using CAESCAP computer code
Fort, J. A.
1983-03-01
One important aspect of the Compressed-Air Energy-Storage (CAES) Program is the evaluation of alternative CAES plant designs. The thermodynamic performance of the various configurations is particularly critical to the successful demonstration of CAES as an economically feasible energy-storage option. A computer code, the Compressed-Air Energy-Storage Cycle-Analysis Program (CAESCAP), was developed in 1982 at the Pacific Northwest Laboratory. This code was designed specifically to calculate overall thermodynamic performance of proposed CAES-system configurations. The results of applying this code to the analysis of five CAES plant designs are presented in this report. The designs analyzed were: conventional CAES; adiabatic CAES; hybrid CAES; pressurized fluidized-bed CAES; and direct coupled steam-CAES. Inputs to the code were based on published reports describing each plant cycle. For each cycle analyzed, CAESCAP calculated the thermodynamic station conditions and individual-component efficiencies, as well as overall cycle-performance-parameter values. These data were then used to diagram the availability and energy flow for each of the five cycles. The resulting diagrams graphically illustrate the overall thermodynamic performance inherent in each plant configuration, and enable a more accurate and complete understanding of each design.
A Theory of Unstaggered Airfoil Cascades in Compressible Flow
NASA Technical Reports Server (NTRS)
Spurr, Robert A.; Allen, H. Julian
1947-01-01
By use of the methods of thin airfoil theory, which include effects of compressibility, rela.tio^as are developed which permit the rapid determination of the pressure distribution over an unstaggered cascade of airfoils of a given profile, and the determination of the profile shape necessary to yield a given pressure distribution for small chord gap ratios, For incompressible flow the results of the theory are compared with available examples obtained by the more exact method of conformal transformation. Although the theory is developed for small chord/gap ratios, these comparisons show that it may be extended to chord/gap ratios of order unity, at least for low speed flows. Choking of cascades, a phenomenon of particular importance in compressor design, is considered.
A Cartesian grid approach with hierarchical refinement for compressible flows
NASA Technical Reports Server (NTRS)
Quirk, James J.
1994-01-01
Many numerical studies of flows that involve complex geometries are limited by the difficulties in generating suitable grids. We present a Cartesian boundary scheme for two-dimensional, compressible flows that is unfettered by the need to generate a computational grid and so it may be used, routinely, even for the most awkward of geometries. In essence, an arbitrary-shaped body is allowed to blank out some region of a background Cartesian mesh and the resultant cut-cells are singled out for special treatment. This is done within a finite-volume framework and so, in principle, any explicit flux-based integration scheme can take advantage of this method for enforcing solid boundary conditions. For best effect, the present Cartesian boundary scheme has been combined with a sophisticated, local mesh refinement scheme, and a number of examples are shown in order to demonstrate the efficacy of the combined algorithm for simulations of shock interaction phenomena.
Aerodynamic force by Lamb vector integrals in compressible flow
NASA Astrophysics Data System (ADS)
Mele, Benedetto; Tognaccini, Renato
2014-05-01
A new exact expression of the aerodynamic force acting on a body in steady high Reynolds number (laminar and turbulent) compressible flow is proposed. The aerodynamic force is obtained by integration of the Lamb vector field given by the cross product of vorticity times velocity. The result is obtained extending a theory developed for the incompressible case. A decomposition in lift and drag contribution is obtained in the two-dimensional case. The theory links the force generation to local flow properties, in particular to the Lamb vector field and to the kinetic energy. The theoretical results are confirmed analyzing numerical solutions obtained by a standard Reynolds Averaged Navier-Stokes solver. Results are discussed for the case of a two-dimensional airfoil in subsonic, transonic, and supersonic free stream conditions.
Combined PDF/SPH method for compressible turbulent flows
NASA Astrophysics Data System (ADS)
Welton, Walter Christian
A particle method which applies the probability density function (PDF) method to compressible turbulent flows is presented. Solution of the PDF equation is achieved using a Lagrangian/Monte Carlo approach which combines techniques borrowed from the field of smoothed particle hydrodynamics (SPH). This combination gives the method a unique ability to extract mean quantities, including the mean pressure gradient, directly from the particles using a grid-free approach. Two algorithms which greatly reduce the computational work for SPH in 1D and 2D have been developed to implement the method; for a simulation with N particles the computational work scales purely as {cal O}(N). The particle method has also been combined with a variance-reduction technique which can significantly reduce statistical error in first and second moments of selected mean flow quantities. When used with a second-order accurate predictor/corrector scheme, the resulting particle method provides a feasible way to obtain accurate PDF solutions to compressible turbulent flow problems. Results are presented for a variety of quasi-1D and 2D flows to demonstrate the method's robustness. These include solutions to both statistically stationary and nonstationary problems, and use both periodic and characteristic-based inflow/outflow boundary conditions. A 2D plane wake simulation also includes comparisons with experimental data and shows good agreement in spite of the simple turbulence model used. Comprehensive studies of numerical errors have also been performed, including a convergence study of the method. Detailed results are presented which confirm the expected behavior of each error.
The Compressible Flow Past Various Plane Profiles Near Sonic Velocity
NASA Technical Reports Server (NTRS)
Goethert, B.; Kawalki, K. H.
1949-01-01
In an earlier report UM No.1117 by Gothert,the single-source method was applied to the compressible flow around circles, ellipses, lunes, and around an elongated body of revolution at different Mach numbers and the results compared as far as possible with the calculations by Lamla ad Busemann. Essentially, it was found that with favorable source arrangement the single-source method is in good agreement with the calculations of the same degree of approximation by.Lamla and Busemann. Near sonic velocity the number of steps must be increased considerably in order to sufficiently approximate the adiabatic curve. After exceeding a certain Mach number where local supersonic fields occur already, it was no longer possible, in spite of the substantially increased number of steps, to obtain a systematic solution because the calculation diverged. This result,was interpreted to mean that above this point of divergence the symmetrical type of flow ceases to exist and changes into the unsymmetrical type characterized by compressibility shocks.
Predicting the stability of a compressible periodic parallel jet flow
NASA Technical Reports Server (NTRS)
Miles, Jeffrey H.
1996-01-01
It is known that mixing enhancement in compressible free shear layer flows with high convective Mach numbers is difficult. One design strategy to get around this is to use multiple nozzles. Extrapolating this design concept in a one dimensional manner, one arrives at an array of parallel rectangular nozzles where the smaller dimension is omega and the longer dimension, b, is taken to be infinite. In this paper, the feasibility of predicting the stability of this type of compressible periodic parallel jet flow is discussed. The problem is treated using Floquet-Bloch theory. Numerical solutions to this eigenvalue problem are presented. For the case presented, the interjet spacing, s, was selected so that s/omega =2.23. Typical plots of the eigenvalue and stability curves are presented. Results obtained for a range of convective Mach numbers from 3 to 5 show growth rates omega(sub i)=kc(sub i)/2 range from 0.25 to 0.29. These results indicate that coherent two-dimensional structures can occur without difficulty in multiple parallel periodic jet nozzles and that shear layer mixing should occur with this type of nozzle design.
NASA Technical Reports Server (NTRS)
Hartfield, Roy J., Jr.; Hollo, Steven D.; Mcdaniel, James C.
1992-01-01
A unified laser-induced fluorescence technique for conducting planar measurements of temperature, pressure and velocity in nonreacting, highly compressible flows has been developed, validated and demonstrated. Planar fluorescence from iodine, seeded into air, was induced by an argon-ion laser and collected using a liquid-nitrogen cooled CCD camera. In the measurement technique, temperature is determined from the fluorescence induced with the laser operated broad band. Pressure and velocity are determined from the shape and position of the fluorescence excitation spectrum which is measured with the laser operated narrow band. The measurement approach described herein provides a means of obtaining accurate, spatially-complete maps of the primary flow field parameters in a wide variety of cold supersonic and transonic flows.
NASA Technical Reports Server (NTRS)
Liu, J.; Tiwari, Surendra N.
1994-01-01
The two-dimensional spatially elliptic Navier-Stokes equations have been used to investigate the radiative interactions in chemically reacting compressible flows of premixed hydrogen and air in an expanding nozzle. The radiative heat transfer term in the energy equation is simulated using the Monte Carlo method (MCM). The nongray model employed is based on the statistical narrow band model with an exponential-tailed inverse intensity distribution. The spectral correlation has been considered in the Monte Carlo formulations. Results obtained demonstrate that the effect of radiation on the flow field is minimal but its effect on the wall heat transfer is significant. Extensive parametric studies are conducted to investigate the effects of equivalence ratio, wall temperature, inlet flow temperature, and the nozzle size on the radiative and conductive wall fluxes.
Operability test procedure for 241-U compressed air system and heat pump
Freeman, R.D.
1994-08-31
The 241-U-701 compressed air system supplies instrument quality compressed air to Tank Farm 241-U. The supply piping to the 241-U Tank Farm is not included in the modification. Modifications to the 241-U-701 compressed air system include installation of a 15 HP Reciprocating Air Compressor, Ingersoll-Rand Model 10T3NLM-E15; an air dryer, Hankinson, Model DH-45; and miscellaneous system equipment and piping (valves, filters, etc.) to meet the design. A newly installed heat pump allows the compressor to operate within an enclosed relatively dust free atmosphere and keeps the compressor room within a standard acceptable temperature range, which makes possible efficient compressor operation, reduces maintenance, and maximizes compressor operating life. This document is an Operability Test Procedure (OTP) which will further verify (in addition to the Acceptance Test Procedure) that the 241-U-701 compressed air system and heat pump operate within their intended design parameters. The activities defined in this OTP will be performed to ensure the performance of the new compressed air system will be adequate, reliable and efficient. Completion of this OTP and sign off of the OTP Acceptance of Test Results is necessary for turnover of the compressed air system from Engineering to Operations.
Optimization study on a single-cylinder compressed air engine
NASA Astrophysics Data System (ADS)
Yu, Qihui; Cai, Maolin; Shi, Yan; Xu, Qiyue
2015-11-01
The current research of compressed air engine (CAE) mainly focused on simulations and system integrations. However, energy efficiency and output torque of the CAE is limited, which restricts its application and popularization. In this paper, the working principles of CAE are briefly introduced. To set a foundation for the study on the optimization of the CAE, the basic mathematical model of working processes is set up. A pressure-compensated valve which can reduce the inertia force of the valve is proposed. To verify the mathematical model, the prototype with the newly designed pressure-compensated intake valve is built and the experiment is carried out, simulation and experimental results of the CAE are conducted, and pressures inside the cylinder and output torque of the CAE are obtained. Orthogonal design and grey relation analysis are utilized to optimize structural parameters. The experimental and optimized results show that, first of all, pressure inside the cylinder has the same changing tendency in both simulation curve and experimental curve. Secondly, the highest average output torque is obtained at the highest intake pressure and the lowest rotate speed. Thirdly, the optimization of the single-cylinder CAE can improve the working efficiency from an original 21.95% to 50.1%, an overall increase of 28.15%, and the average output torque increases also increases from 22.047 5 N • m to 22.439 N • m. This research designs a single-cylinder CAE with pressure-compensated intake valve, and proposes a structural parameters design method which improves the single-cylinder CAE performance.
Proceedings: Geotechnology workshop on compressed-air energy storage in porous media sites
Not Available
1987-07-01
The extensive experience of the natural gas industry with gas storage in underground porous media is directly applicable to the storage of air for compressed-air energy storage plants. In this workshop, natural gas industry representatives provided utility personnel with a basic understanding of the geology of porous media and strategies for developing air storage reservoirs.
Nitric oxide flow tagging in unseeded air.
Dam, N; Klein-Douwel, R J; Sijtsema, N M; Meulen, J J
2001-01-01
A scheme for molecular tagging velocimetry is presented that can be used in air flows without any kind of seeding. The method is based on the local and instantaneous creation of nitric oxide (NO) molecules from N(2) and O(2) in the waist region of a focused ArF excimer laser beam. This NO distribution is advected by the flow and can be visualized any time later by laser-induced fluorescence in the gamma bands. The creation of NO is confirmed by use of an excitation spectrum. Two examples of the application of the new scheme for air-flow velocimetry are given in which single laser pulses are used for creation and visualization of NO. PMID:18033499
40 CFR 89.414 - Air flow measurement specifications.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 40 Protection of Environment 20 2011-07-01 2011-07-01 false Air flow measurement specifications. 89.414 Section 89.414 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Emission Test Procedures § 89.414 Air flow measurement specifications. (a) The air flow measurement...
40 CFR 89.414 - Air flow measurement specifications.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Air flow measurement specifications. 89.414 Section 89.414 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Emission Test Procedures § 89.414 Air flow measurement specifications. (a) The air flow measurement...
Upgrade of Compressed Air Control System Reduces Energy Costs at Michelin Tire Plant
2002-01-01
This case study highlights the upgraded compressed air system at a Michelin tire manufacturing plant in Spartanburg, South Carolina. The controls upgrade project enabled multiple compressor operation without blow-off, and significantly reduced energy costs.
Engineering Task Plan Supporting Rupture of Compressed Air Lines in Contaminated Areas USQ
JANICEK, G.P.
2001-11-30
This Engineering Task Plan (ETP) defines the Tasks and organizational responsibilities for obtaining Tank Farm data relative to pit structures and soil contamination levels for purposes of resolving the rupture of compressed air/gas lines unreviewed safety question.