A Cycle Simulation Including the Second Law of Thermodynamics for a Spark-Ignition Engine: Implications of the Use of Multiple-Zones for Combustion
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A thermodynamic cycle simulation using multiple zones for the combustion process was used to obtain the performance, energy and availability characteristics for an automotive spark-ignition engine. In addition to the traditional formulations based on the first law of thermodynamics, the simulation also included considerations based on the second law of thermodynamics. The characteristics of the engine combustion process and the impact of the multiple-zone formulation were determined. The burned gases were divided into an adiabatic core and boundary layer. The heat transfer of the burned gases was assigned in total to the boundary layer. From the start of combustion until 90aTDC, the difference between the temperatures of the adiabatic core and the burned gases increased from zero to about 250 K. The implications of this temperature increase on nitric oxide computations are discussed. The specific entropy values during combustion from the multiple zone simulation are less than from a similar single-zone simulation. This was shown to be largely a result of the higher burned gas temperatures of the multiple zone simulation which resulted in less entropy production. The overall change of entropy for the complete combustion process was the same for both approaches. The overall cycle values for the transfers and destruction of availability were essentially identical with the values obtained from a similar single-zone simulation. Copyright 2002 Society of Automotive Engineers, Inc.
