Diesel combustion and fuel spray analysis using an optical engine with pressure diagnostics, infrared thermography, and high-speed photography

Infrared and high-speed images along with pressure information have been recorded and used to evaluate events inside an optically accessible Diesel engine. A 6-band a 14-hole nozzle are examined, each at two load conditions. The fuel spray and combustion characteristics are examined and discussed. It is determined from examination of the fuel spray that the 6-hole nozzle penetrates the combustion bowl more quickly but the 14-hole nozzle tends to distribute fuel more uniformly. Comparison of the images recorded from in-cylinder combustion experiments with pressure data demonstrated the differences in performance between the two nozzles. Infrared photography showed a start of combustion earlier than was seen in the high-speed pictures pressure data showed start of combustion earlier than was captured by either camera. High-speed photography showed a possible increase in soot production for the 6-hole nozzle as compared to the 14-hole nozzle. In-cylinder temperatures were estimated from infrared pictures. Overall, higher pressures and temperatures were produced with the 6-hole nozzle while the 14-hole nozzle showed less visible soot while yielding higher IMEP values for these operating conditions. This presentation describes the physics behind these observations, the experimental methods developed for this effort, and the performance of these two combustion systems.