Heat Transfer into Ceramic Combustion Chamber Wall of Internal Combustion Engines

2003 ◽

Cited By ~ 1

Author(s):

T. Shudo ◽

H. Oka

Keyword(s):

Heat Transfer ◽

Combustion Chamber ◽

Heat Loss ◽

Thermophysical Properties ◽

Internal Combustion Engines ◽

Internal Combustion ◽

Spark Ignition ◽

Hydrogen Combustion ◽

Spark Ignition Engine ◽

Combustion Engines

Hydrogen is a clean alternative to fossil fuels for internal combustion engines and can be easily used in spark-ignition engines. However, the characteristics of the engines fueled with hydrogen are largely different from those with conventional hydrocarbon fuels. A higher burning velocity and a shorter quenching distance for hydrogen as compared with hydrocarbons bring a higher degree of constant volume and a larger heat transfer from the burning gas to the combustion chamber wall of the engines. Because of the large heat loss, the thermal efficiency of an engine fueled with hydrogen is sometimes lower than that with hydrocarbons. Therefore, the analysis and the reduction of the heat loss are crucial for the efficient utilization of hydrogen in internal combustion engines. The empirical correlations to describe the total heat transferred from the burning gas to the combustion chamber walls are often used to calculate the heat loss in internal combustion engines. However, the previous research by one of the authors has shown that the widely used heat transfer correlations cannot be properly applied to the hydrogen combustion even with adjusting the constants in them. For this background, this research analyzes the relationship between characteristics of thermophysical properties of working substance and heat transfer to the wall in a spark-ignition engine fueled with hydrogen.

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Maximum efficiencies for internal combustion engines: Thermodynamic limitations

International Journal of Engine Research ◽

10.1177/1468087417737700 ◽

2017 ◽

Vol 19 (10) ◽

pp. 1005-1023 ◽

Cited By ~ 9

Author(s):

Jerald A Caton

Keyword(s):

Heat Transfer ◽

Internal Combustion Engines ◽

High Efficiency ◽

Pressure Rise ◽

Internal Combustion ◽

Thermodynamic Evaluation ◽

Combustion Engines ◽

Automotive Engine ◽

Specific Heats ◽

Cycle Simulation

The thermodynamic limitation for the maximum efficiencies of internal combustion engines is an important consideration for the design and development of future engines. Knowing these limits helps direct resources to those areas with the most potential for improvements. Using an engine cycle simulation which includes the first and second laws of thermodynamics, this study has determined the fundamental thermodynamics that are responsible for these limits. This work has considered an automotive engine and has quantified the maximum efficiencies starting with the most ideal conditions. These ideal conditions included no heat losses, no mechanical friction, lean operation, and short burn durations. Then, each of these idealizations is removed in a step-by-step fashion until a configuration that represents current engines is obtained. During this process, a systematic thermodynamic evaluation was completed to determine the fundamental reasons for the limitations of the maximum efficiencies. For the most ideal assumptions, for compression ratios of 20 and 30, the thermal efficiencies were 62.5% and 66.9%, respectively. These limits are largely a result of the combustion irreversibilities. As each of the idealizations is relaxed, the thermal efficiencies continue to decrease. High compression ratios are identified as an important aspect for high-efficiency engines. Cylinder heat transfer was found to be one of the largest impediments to high efficiency. Reducing cylinder heat transfer, however, is difficult and may not result in much direct increases of piston work due to decreases of the ratio of specific heats. Throughout this work, the importance of high values of the ratio of specific heats was identified as important for achieving high thermal efficiencies. Depending on the selection of constraints, different values may be given for the maximum thermal efficiency. These constraints include the allowed values for compression ratio, heat transfer, friction, stoichiometry, cylinder pressure, and pressure rise rate.

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A General Rezoning Technique for KIVA3V Internal Combustion Engines CFD Simulations

ASME 2010 Internal Combustion Engine Division Fall Technical Conference ◽

10.1115/icef2010-35147 ◽

2010 ◽

Author(s):

Randy P. Hessel ◽

Ettore Musu ◽

Salvador M. Aceves ◽

Daniel L. Flowers

Keyword(s):

Combustion Chamber ◽

Internal Combustion Engines ◽

Ad Hoc ◽

National Laboratory ◽

Internal Combustion ◽

Computational Time ◽

Combustion Engines ◽

Combustion Chambers ◽

Time Step ◽

Engine Cycle

A computational mesh is required when performing CFD-combustion modeling of internal combustion engines. For combustion chambers with moving pistons and valves, like those in typical cars and trucks, the combustion chamber shape changes continually in response to piston and valve motion. The combustion chamber mesh must then also change at each time step to reflect that change in geometry. The method of changing the mesh from one computational time step to the next is called rezoning. This paper introduces a new method of mesh rezoning for the KIVA3V CFD-combustion program. The standard KIVA3V code from Los Alamos National Laboratory comes with standard rezoners that very nicely handle mesh motion for combustion chambers whose mesh does not include valves and for those with flat heads employing vertical valves. For pent-roof and wedge-roof designs KIVA3V offers three rezoners to choose from, the choice depending on how similar a combustion chamber is to the sample combustion chambers that come with KIVA3V. Often, the rezoners must be modified for meshes of new combustion chamber geometries to allow the mesh to successfully capture change in geometry during the full engine cycle without errors. There is no formal way to approach these modifications; typically this requires a long trial and error process to get a mesh to work for a full engine cycle. The benefit of the new rezoner is that it replaces the three existing rezoners for canted valve configurations with a single rezoner and has much greater stability, so the need for ad hoc modifications of the rezoner is greatly reduced. This paper explains how the new rezoner works and gives examples of its use.

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