Instantaneous 2D imaging of temperature in an engine cylinder with flame combustion

To improve internal combustion engines, it is critical to measure the temperature distribution of their walls. However, only a few studies have quantitatively visualized the instantaneous temperature distribution of a wall exposed to flames. Lifetime-based temperature imaging was performed using a simple measurement system consisting of a non-intensified high-speed CMOS camera, a pulsed UV laser, and a phosphor coated quartz glass covered with a thin metal film. The uncertainty in the temperature measurement was ±2.0 °C for measurements of uniform temperature fields in the range 40–250 °C. Single-shot wall temperature measurements were demonstrated for combustion by flames in an engine cylinder. This enabled inhomogeneous temperature distributions in the engine with or without flames to be visualized. Even under motoring conditions, there was a large temperature gradient across the side window at the highest position of the piston. The side window temperature decreased near the intake valve. The intake gas flow had a cooling effect and the intake pressure affected the temperature distribution. The engine speed and the coolant temperature increased the magnitude of temperature but they did not affect the overall temperature distribution, i.e. the spatial distribution and the spatial gradient of the temperature. The instantaneous temperature of the top of the piston was visualized in the transient process after firing had commenced.