Identification and characterization of impingement signatures in a high speed diesel engine using piston surface temperature measurements

The primary area of diesel engine research focuses on the significant reduction of emissions. Spray development, atomization, fuel injectors, and combustion chamber shape and size are areas of significant research in the quest to minimize the production of emissions while maintaining high power output. The focus of this research involves the measurement of instantaneous piston surface temperatures in an attempt to identify and characterize the fuel impingement event on the piston surface. Fuel impingement can lead to increased emissions, shortened lifetime of the piston and increased fuel consumption. Instantaneous piston surface temperature data is limited, especially in the vicinity of spray impingement. Dimensional analysis has led to the development of a tool to predict the occurrence of impingement, given certain operating parameters and geometric variables of the engine. This predictive tool could be used during the design stage of the engine to minimize the occurrence of impingement, knowing the power requirements, dimensions and operating environment.; To conduct the proposed research, one piston from a four cylinder, small bore, high speed diesel engine was modified to accommodate 15 thermocouples and wireless microwave telemetry. Three of the fast response surface thermocouples were installed on the piston bowl lip, at locations of likely impingement. The telemetry transmitted the thermocouple information from the piston to a receiver and then to a high speed data acquisition system. The impingement of a burning spray plume on the piston surface was identified under specific operating conditions of the engine. The impingement signature was positively identified using a rate of change analysis of the piston temperature data. A threshold value of rate of change was used to filter the results into impinging operating conditions and non-impinging operating conditions. The characteristic signature, dT/dtheta, of the impinging spray was able to be predicted using dimensional analysis. It was determined that the presence of impingement on the piston bowl lip significantly affects the temperature distribution on the piston surface. Additionally, spray impingement is strongly correlated to injection pressure and engine speed, as impingement was not identified above engine speeds of 1800 rpm.