Experimental study of diesel spray characteristics and atomization

An experimental study was carried out to understand the transient characteristics of high-pressure diesel injections with a technically advanced injection system. The study consists of two phases: spray characteristics and spray atomization. High-speed photography and digital imaging were applied to investigate the diesel spray characteristics and atomization.; In the first phase, an optical setup with a high-speed movie camera was used to obtain sequential high-speed photographs of transient sprays in a constant volume spray chamber. The spray images were analyzed with a light extinction technique to provide spray characteristics which include the spray tip penetration length, spray angles, spray dispersion, and overall spray size. Experiments were conducted to investigate the effects of eight parameters on spray characteristics. The parameters investigated included injection pressure, ambient density, nozzle diameter, nozzle injection angle, number of nozzle hole, nozzle inlet geometry, fuel viscosity and injection pattern (multiple injection). Some of these parameters were studied with single hole nozzles while the others were with multi-hole nozzles.; In the second phase, a high-speed digital camera was used to record the dynamic process of diesel spray atomization which occurs at the nozzle exit. A long distance microscope lens was utilized with the high-speed digital camera to obtain sequential, high-magnification spray images. The measured parameters were the spray initial divergence angle and the fuel jet diameter at the nozzle exit. Efforts were made to measure the size of the droplets formed in the periphery of the fuel jet near the nozzle exit and the fuel jet surface wave. Experiments were performed to study the effects of injection pressure, ambient density, nozzle diameter, and nozzle injection angle on the spray atomization.