A Thermodynamic Analysis for Detonation-Free Engine Performance

1970 ◽  
Vol 92 (3) ◽  
pp. 231-238 ◽  
Author(s):  
C. K. Powell ◽  
R. N. Alford ◽  
T. N. Chen ◽  
V. Kevorkian
Keyword(s):  
Thermodynamic Analysis ◽  
Combustion Engine ◽  
Pressure Ratio ◽  
Engine Performance ◽  
Constant Volume ◽  
Analytical Prediction ◽  
Wide Range ◽  
Performance Map ◽  
Constant Volume Combustion ◽  
Detonation Limit

A method of thermodynamic analysis of power cycles incorporating more complete expansion and turbocharging with after-cooling is presented; it predicts the performance of constant volume combustion engines under detonation-free conditions. The analysis involves expressing the detonation limit in terms of the firing pressure and a theoretical adiabatic end-gas temperature. Expressing the detonation limit in this form, the performance map for any constant volume combustion engine can be predicted. The map yields detonation-free operation over a wide range of bmep and bsfc by identifying the required combinations of fuel-air ratio, compression ratio, expansion ratio, and blower pressure ratio. The analysis requires information on the combustion characteristics of the specific engine, namely, the deviations of the thermal efficiency and the firing pressure from those derived from the equivalent fuel-air cycle. Analysis showed that a significant gain of engine output can be realized without detonation occurring by employing higher blower pressure ratio and firing pressure. The lower limit of fuel consumption is determined directly by the performance of the turbocharger and indirectly by the heating of the inlet air and the detonation limit. Tests performed on a 17-in-bore single cylinder gas engine at two different expansion ratios verified the analytical prediction of detonation-free operation over a wide range of bmep, from 135 to 346 psi. The type of performance map resulting from this analysis is useful in the selection of engine performance and engine parameters for the development of new engines.

A New Approach to Maximize the Potential of Reciprocating Engines Operating on Bio-Fuel Energy

2011 ◽  
Author(s):  
Henry Lam ◽  
Mark Richter ◽  
Geoff Ashton
Keyword(s):  
Combustion Engine ◽  
Pressure Ratio ◽  
Waste Water Treatment ◽  
Pressure Sensors ◽  
Bulk Temperature ◽  
Lean Burn ◽  
Fuel Gas ◽  
Heating Value ◽  
Combustion Performance ◽  
Wide Range

Since the Industrial Revolution one of the oldest and “greenest” bio-fuel energy sources has been the byproduct of sewage and landfill. These biogases also known as Land Fill Gas or Digester Gas can be used as a fuel in an internal combustion engine, the clear choice for their efficiency in heat recovery and utility as a prime mover. The problem with bio-fuels is their unpredictable and varying fuel heating values which creates a challenge for maintaining air fuel ratio (AFR). If AFR is not controlled this can lead to engine instability and an increase in NOx, CO and THC emissions. With today’s ever increasing scrutiny of combustion pollutants this could spell the end of these types of fuels in combustion engines. AETC has embraced this challenge to provide a system that addresses the seasonal fuel gas quality, Low Heating Value (LHV) fluctuation to operate engines at best achievable emissions. This case study focuses on two Caterpillar 3516 Generator Engines rated 1000VA, at 1200 rpm, lean burn gas and turbocharged, running on renewable energy source supplementing power to a waste water treatment facility in California. The engines operate on wide range of fuel mixture including landfill, digester gas and air blended natural gas over a heating value range from 350–650 BTU. The fuel gas LHV constantly varies depending on fuel availability controlled by pressure switches within the individual fuel headers. Determining fuel heating values by using a gas calorimeter is not a viable option due to its high cost and poor reliability when operating in the environment of unfiltered Digester and landfill gas. AETC installed their Advanced Monitoring System (AMS) to utilize the engine as a calorimeter and to determine the fuels LHV. As part of the AMS functionality, the system acquired all the existing AFRC parameters such as kilo-Watt, RPM, Fuel Flow, Air Manifold Pressure and Temperature to determine the combustion performance. This simple approach offers surprisingly good performance while tying together basic thermodynamics, combustion performance and emissions. The system can also be used to parametrically determine engine emissions, based on the calculated combustion pressure without installing pressure sensors. The AMS monitors and determines emissions based on Trapped Equivalence Ratio, Effective Bulk Temperature or Pressure Ratio on single or multiple fuels providing a green/red light as an indicator of in/out of compliance accurately meeting today’s most stringent regulatory conditions.

The flame behaviour of liquefied petroleum gas spray impinging on a flat plate in a constant volume combustion chamber

2005 ◽  
Vol 219 (5) ◽  
pp. 655-663 ◽  
Author(s):  
Kweonha Park
Keyword(s):  
Combustion Chamber ◽  
Ambient Pressure ◽  
Constant Volume ◽  
Chamber Pressure ◽  
Cylinder Wall ◽  
Liquefied Petroleum Gas ◽  
Wide Range ◽  
Constant Volume Combustion ◽  
Constant Volume Combustion Chamber ◽  
Ignition Site

Liquefied petroleum gas (LPG) sprays and diffusion flames are investigated in a constant volume combustion chamber having an impingement plate. The spray and flame images are visualized and compared with diesel and gasoline images over a wide range of ambient pressure. The high-speed digital camera is used to take the flame images. The injection pressure is generated by a Haskel air-driven pump, and the initial chamber pressure is adjusted by the amount of pumping air. The LPG spray and flame photographs are compared with those of gasoline and diesel fuel at the same conditions, and then the spray and flame development behaviour is analysed. The spray photographs show that the dispersion characteristics of LPG spray are sensitive to the ambient pressure. In a low initial chamber pressure LPG fuel in the liquid phase evaporates quickly and does not reach down easily to the impinging plate having a hot coil for ignition. That makes the temperature and equivalence ratio low near the ignition coil, thus making ignition diffcult. On the other hand, in a high initial chamber pressure the spray leaving the nozzle gathers around the ignition site after impinging on the plate, which makes an intense flame near the plate. If applied to small-sized direct injection engines that are not able to avoid spray impinging on a cylinder wall, LPG will have faster and cleaner combustion than diesel or gasoline fuels. However, the chamber geometry should be carefully designed to enable a sufficient amount of vaporized fuel to get to the ignition site

Multiphysics Numerical Investigation of an Aeronautical Lean Burn Combustor

2019 ◽  
Author(s):  
D. Bertini ◽  
L. Mazzei ◽  
A. Andreini ◽  
B. Facchini
Keyword(s):  
Fluid Dynamics ◽  
Pressure Ratio ◽  
Computational Cost ◽  
Engine Performance ◽  
Pollutant Emissions ◽  
Strong Interactions ◽  
Inlet Temperature ◽  
Test Case ◽  
Lean Burn ◽  
Wide Range

Abstract The importance of the combustion chamber has been underestimated for years by aeroengine manufacturers that focused their research efforts mainly on other components, such as compressor and turbine, to improve the engine performance. Nevertheless, stricter requirements on pollutant emissions have contributed to increase the interest on combustor development and, nowadays, new design concepts are widely investigated. To meet the goals of ACARE FlightPath 2050 and future ICAO-CAEP standards one of the most promising results is provided by the Lean Burn technology. As this combustion mode is based on a lean Primary Zone, the air devoted to liner cooling is restricted and advanced cooling systems must be exploited to obtain higher overall effectiveness. The pushing trends of Turbine Inlet Temperature and Overall Pressure Ratio in modern aeroengine are not supported enough by the development of materials, thus making the research branch of liner cooling increasingly relevant. In this context, Computational Fluid Dynamics is able to predict the flow field and the complex interactions between the involved phenomena, supporting the design of modern Lean Burn combustors in all stages of the process. RANS approaches provide a solution of the problem with low computational cost, but can lack in accuracy when the flow unsteadiness dominates the fluid dynamics and the strong interactions, as in aeroengine combustors. Even if steady simulations can be easily employed in the preliminary design, their inaccuracy can be detrimental for an optimized combustor design and Scale-Resolving methods should be preferred, at least, in the final stages. Unfortunately, having to deal with a multiphysics problem as Conjugate Heat Transfer (CHT) in presence of radiation, these simulations can become computationally expensive and some numerical treatments are required to handle the wide range of time and space scales in an unsteady framework. In the present work the metal temperature distribution is investigated from a numerical perspective on a full annular aeronautical lean burn combustor operated at real conditions. For this purpose, the U-THERM3D multiphysics tool was developed in ANSYS Fluent and applied on the test case. The results are compared against RANS and experimental data to assess the tool capability to handle the CHT problem in the context of scale-resolving simulations.

An Optically-Accessible Combustion Apparatus for Direct-Injection Natural Gas Ignition Studies

2007 ◽  
Author(s):  
Mark A. Fabbroni ◽  
Stewart Xu Cheng ◽  
Vito Abate ◽  
James S. Wallace
Keyword(s):  
Natural Gas ◽  
Initial Conditions ◽  
Direct Injection ◽  
Engine Performance ◽  
Constant Volume ◽  
Compression Process ◽  
Compression Ignition Engine ◽  
Engine Cylinder ◽  
Experimental Apparatus ◽  
Constant Volume Combustion

Research investigating direct injection natural gas (DING) diesel engines shows many attractions in engine performance including higher thermal efficiency and higher power output as well as significant improvement of exhaust emissions. However, ignition of injected natural gas is difficult and requires some form of ignition assist, such as a diesel pilot or a glow plug. This paper introduces the experimental apparatus used for compression ignition engine studies in the Engine Research and Development Laboratory (ERDL) at University of Toronto. The apparatus consists of an optically accessible constant volume combustion bomb coupled to a single-cylinder Cooperative Fuel Research (CFR) engine through its spark plug port. The engine provides rapid compression to create realistic engine conditions in the combustion bomb and also scavenges the combustion products. During the engine compression process, the piston pushes the air from the engine cylinder to the constant volume combustion bomb, generating high-pressure, high-temperature initial conditions and a strong swirling air flow in the constant volume combustion bomb. Experiments were conducted to measure temperatures and pressures in the constant volume combustion bomb for a range of initial conditions. The experiments were complemented by numerically modeling the whole domain of the CFR engine cylinder, the constant volume combustion bomb, and the port connecting them using a modified KIVA-3V code. The code computes spatially and temporally resolved pressure, temperature and swirl intensity in the constant volume combustion bomb during the compression process. The experimental and the numerical results are in satisfactory agreement and provide validation of the initial conditions in the constant volume combustion bomb for subsequent studies of injection and ignition.

Influence of pressure pulsation on the performance of compression system and turbocharged engine

2021 ◽  
pp. 095440702110304
Author(s):  
Zeng Hanxuan ◽  
Wang Baotong ◽  
Zou Wangzhi ◽  
Zheng Xinqian
Keyword(s):  
Pressure Pulsation ◽  
Combustion Engine ◽  
Characteristic Curve ◽  
Pressure Ratio ◽  
Engine Performance ◽  
Concave Function ◽  
Transient Pressure ◽  
Compression System ◽  
Compressor Inlet ◽  
The Impact

Pressure pulsation widely exists in power machinery combining compression components and pipelines. It has substantial effects on the performance of compressor as part of the compression system, as well as the engine. In this paper, the pressure pulsations under different excitation frequencies are measured and analyzed in the intake system of a turbo-charged and inter-cooled internal combustion engine. It is pointed out that the amplification of the pressure pulsation at the compressor inlet and outlet is caused by the coupling effects within the compression system, which consequently lead to the formation of a stable standing wave. Further research indicates that the pulsation at the compressor boundary will cause its pressure ratio to fluctuate. Additionally, because the compressor characteristic curve resembles a concave function, the fluctuation of transient pressure ratio will further cause the time-averaged pressure ratio to decline. Finally, the impact on engine performance is evaluated based on a well-validated simulation model.

The Time Required for Constant-Volume Combustion

1952 ◽  
Vol 19 (1) ◽  
pp. 72-76
Author(s):  
A. S. Campbell
Keyword(s):  
Temperature Distribution ◽  
Flame Front ◽  
Thermodynamic Analysis ◽  
Burning Velocity ◽  
Combustion Process ◽  
Constant Volume ◽  
Time Rate ◽  
Constant Volume Combustion ◽  
Time Required ◽  
Normal Burning Velocity

Abstract By combining the results of an elementary thermodynamic analysis of the temperature distribution in the burned gases of a constant-volume bomb with an examination of the velocity relations at the flame front, it is possible to relate the “normal burning velocity” to the time rate of production of burned gases. Integration of this equation leads to an estimate of the time required for the combustion process.

A Method to Estimate the Performance Map of a Centrifugal Compressor Stage

2012 ◽  
Vol 135 (2) ◽  
Author(s):  
Michael Casey ◽  
Chris Robinson
Keyword(s):  
Centrifugal Compressor ◽  
Pressure Ratio ◽  
Flow Coefficient ◽  
Compressor Stage ◽  
Algebraic Equations ◽  
Centrifugal Compressor Stage ◽  
Novel Approach ◽  
Wide Range ◽  
Performance Map ◽  
Vaneless Diffusers

A novel approach to calculate the performance map of a centrifugal compressor stage is presented. At the design point four nondimensional parameters (the flow coefficient φ, the work coefficient λ, the tip-speed Mach number M, and the efficiency η) characterize the performance. In the new method the performance of the whole map is also based on these four parameters through physically based algebraic equations which require little prior knowledge of the detailed geometry. The variable empirical coefficients in the parameterized equations can be calibrated to match the performance maps of a wide range of stage types, including turbocharger and process compressor impellers with vaned and vaneless diffusers. The examples provided show that the efficiency and the pressure ratio performance maps of turbochargers with vaneless diffusers can be predicted to within ±2% in this way. More uncertainty is present in the prediction of the surge line, as this is very variable from stage to stage. During the preliminary design the method provides a useful reference performance map based on earlier experience for comparison with objectives at different speeds and flows.

Sign in / Sign up

Export Citation Format

Share Document