Experimental recording of unsteady temperatures in the piston of a high-speed diesel engine under transient conditions

Abstract

Unsteady thermal loads on combustion chamber parts in a supercharged diesel engine dictate their service life. In practice, it is crucial to know the dynamic behaviour of temperatures and their gradients for automobile and tractor diesels that often change their operating conditions during running. Most reliable information can be obtained by experimental recording of temperatures on a test bench during engine tests. This information is used for mathematical modelling of temperature fields and temperature stresses. The objective of this research effort is the experimental recording of unsteady piston temperatures when the diesel load is increased and reduced rapidly. Thermocouples were chosen, and their thermal response was evaluated to increase the accuracy of recording piston temperatures. In addition, locations for installing thermocouples were chosen. A continuous-type current sensor was developed and refined to connect the hot junctions of the thermocouples with the recording instrumentation. The unsteady temperatures of the piston (aluminium alloy AL 25) in a high-speed diesel engine were recorded experimentally. Piston temperatures were recorded for cases when the load was increased and reduced rapidly. Treatment of experimental data has yielded the basic dynamic characteristics of the temperature fields in the diesel piston).