Laser-Induced Phosphorescence Thermography of Combustion Chamber Wall of Diesel Engine

In order to investigate the mechanism of heat transfer on the chamber wall of direct-injection diesel engines, 2-D temperature imaging and heat flux measurement in the flame impinging region on the chamber wall were conducted using laser-induced phosphorescence technique. The temperature of the chamber wall surface was measured by the calibrated intensity variation of the 355nm-excited laser-induced phosphorescence from an electrophoretically deposited thin layer of La2O2S:Eu phosphor on a quartz glass plate placed in a rapid compression and expansion machine (RCEM). Instantaneous 2-D images of wall temperature at different timings after start of injection and time-resolved (10kHz) heat flux near the flame impinging region were obtained for combusting and non-combusting diesel sprays with impinging distance of 23.4mm at different injection pressures (80 and 120MPa). The measured temperature images of the chamber wall for the combusting spray exhibited finely structured temperature distribution, while a smoother temperature distribution was observed for the non-combusting spray. The temperature increase due to spray and flame impingement was observed both for combusting and non-combusting sprays, but observed in a much larger area extending downstream for the combusting spray. The increase of injection pressure advanced and enhanced the heat transfer due to spray impingement.