Nghiên cứu tính toán động cơ | Comparisons of instructional and complete versions of thermodynamic engine cycle simulations for sparkignition engines JERALD A. CATON Texas A M University Department of Mechanical Engineering College Station TX 77840 USA. jcaton@ Received 6th July 1999 Revised 21st March 2000 Instructional and complete versions of thermodynamics engine cycle simulations for sparkignition engines were compared. The instructional version of the cycle simulation used constant specific heats as compared to using variable properties and composition for the complete simulation. For the proper selection of constant properties the global engine performance parameters obtained from the instructional version of the cycle simulation were in close agreement to the values obtained from using the complete version of the simulation. The specific values of items such as maximum pressure and temperature however were not exactly duplicated. Examples are given based on a commercial spark-ignition engine. For the cases studied here the brake power and thermal efficiency as obtained from the constant property version of the simulation for a ratio of specific heats of and a gas constant of kJ kg K were in excellent agreement with the same parameters from the complete simulation for a range of operating conditions. Key words engine simulation modeling thermodynamics INTRODUCTION In teaching the subject of internal combustion engines the use of engine cycle simulations has proved to be an effective way to help students understand engine thermodynamics and operation. By integrating the development and use of engine simulations with the other class material the students acquire a much deeper and fuller appreciation of the subject. Thermodynamic engine cycle simulations have been developed and used since at least the early 1960s 1-5 Over the years these simulations have evolved into complex and computationally intensive computer programs. A major component of the complexity is the
