Instantaneous Heat Transfer over the Piston of a Motored Direct injection Type Diesel Engine

The instantaneous heat transfer through the piston was measured in a motored direct injection-type diesel engine. The engine piston was equipped with a fast-response thermocouple on the surface and at a specified distance below the surface thermocouple at a number of locations. In order to record and process the measurement of temperature and cylinder pressure, a personal computer (PC)-based data acquisition system was connected to the probes, A special linkage device was designed and implemented to connect the thermocouple wires between the bottom of the connecting rod and a stationary point on the oil pan. The surface heat flux was calculated using a one-dimensional conduction model with the measured temperature boundary conditions. The in-cylinder pressure data was used to calculate the cylinder air temperature and the instantaneous film heat transfer coefficient was calculated by using those in-cylinder measurements. The results of the experiment were discussed and compared to the previous results and the predictions made by others. The measured heat flux/engine speed relationship agreed with previous results. However, the measurements at various positions and at a range of intake manifold pressures did not check with prior predictions. The discrepancies could be contributed to different engine and operation conditions used.