Measuring and Prediction of Temperature Distribution in a Spark Ignition Engine Piston and Cylinder Head at Actual Process

摘要

Piston and cylinder head temperature has considerable influence on efficiency, emission, and performance of the SI (Spark Ignition) engine. Purpose of this investigation is measurement of piston transient temperature at several points on the piston and cylinder head, from cold start to steady condition and comparison with results of finite element analysis. From analytical analysis of piston velocity and acceleration forces on the thermocouple wires, due to piston and oil effects were estimated. A flexible compensation wire was employed, and in order to prevent wire entanglement, a suitable pathway was designed. Transient temperatures were measured at ten points on the piston and at five points on the cylinder head. A specially designed low pass electronic filter was used to reduce the spark plug interference and noise. Results show variation of temperature at various points on the piston and cylinder head with time and engine speed. Engine cycle simulation was carried out in order to calculate gas pressure and temperature. From these, coefficients of heat transfer for oil, air, water and boundary condition on contact surfaces were determined. The piston and cylinder head geometry was modeled with AUTOCAD. ANSYS package was used to analysis three-dimensional nonlinear transient thermal model of the piston. Material properties were considered as temperature dependent. Boundary conditions were considered as time dependent. Hence temperature distribution was determined. Comparison with results of measurements, lead a better determination of heat transfer coefficient for the rings groove.