Thermal loading and surface temperature analysis of the piston of a small HSDI diesel engine

Diesel engines have long known to be ideal for large scale, mostly commercial vehicles. However, despite their emission and noise issues, there's a demand for using diesel engines in passenger vehicles and military applications due to their efficient operation added to the lower cost of diesel fuel. Hence, there's an increasing motive for obtaining higher power densities from diesel engines.; Higher power output can partly be achieved by increasing the speed which Diesel engines lack compared to gasoline engines. Benefiting from new technologies, such as new injection systems, that enhance the mixing of fuel with air, it is now possible to reach higher speeds and higher power outputs from Diesel engines.; Increased output, however, possesses higher combustion temperatures and pressures that yield higher thermal loads on combustion chamber components. Consequently, component failures, such as thermal stress cracking, are more imminent, shortening the life span of engines and limiting higher power. A better understanding of the heat transfer phenomenon is therefore necessary inside the combustion chamber components to shed light into the process of choosing the right material and improving the design of these components.; One of the pistons of a 2.0L small HSDI diesel engine with common rail technology was instrumented with eight fast response surface, and seven slow response imbedded thermocouples to capture instantaneous temperatures during the fired operation. Measurements were transferred from the engine by means of wireless telemetry rather than the traditional linkage arm, which allowed for testing conditions practically at every engine speed and loading possible. High speed acquisition of cylinder pressure, injection pulse signals and crank position were also recorded along with the temperature measurements.; Measurements were done at different speed and load conditions, and two different injector rotation positions to capture on spray axis and off spray axis instantaneous temperatures. Results were supplied as boundary conditions to a 2D finite element model of the piston cross section developed to solve for instantaneous thermal loading. 1D semi-infinite analytical heat transfer solutions were developed that use instantaneous piston surface temperature measurements as boundary conditions. Heat transfer results from FE model were compared with these analytical solutions to study the extent of semi-infinite behavior of piston surface.; Results also included instantaneous and time-averaged heat transfer distribution to different parts of the piston at different running conditions and at On/Off Spray Axis. Further investigation was made about the significant frequency content of the piston surface temperature.