Optical Technique Using Nano-Spark Lightsource for Macro and Microscale Image Acquisition to Study Diesel Spray Atomization

Abstract

Atomization and fuel-air mixing is an important process in diesel combustion. It directly affects the combustion and emission of diesel engine. Optical technique has the advantage of being unobtrusive in nature when compared to other technique. nanospark unit that has spark duration of 30ns was used as a lightsource to capture high resolution spray image using still film camera. The very short duration of the spark freeze the fast movement of the spray droplet, and sharp image of fuel droplet to be successfully captured by the camera, and then analyzed for sizing and spatial distribution. In addition, by using a more elaborate optical setup, dual image of the same spray can be captured, with a very short time interval between each of them. This provides the means to study dynamic behaviors of the diesel spray and also the droplets, as the progression of the spray and trajectory and velocity of the droplet can be analyze from these images. With the proposed optical technique and optical arrangement, microscopic detail of the diesel engine spray can be captured. Critical data such as droplet sizing can be extracted from this high resolution image. Furthermore, by introducing a more sophisticated optical arrangement coined dual -nano spark photography method, the droplet dynamic behaviors such as flying angle and velocity can be study.