Abstract
KEYWORDS: spray impingement, ultra-low temperature, macroscopic characteristics, transient behavior, particle image velocimetry
ABSTRACT
In Direct-Injection (DI) engine, fuel spray impinging on cylinder wall and piston affects the fuel-air mixture formation process which influences engine combustion and emissions. It reduces the engine cold start capability especially in cold regions around the world. In this experimental investigation, a robust low temperature thermostatic bath combined with specially designed heat exchangers are used to reach ultra-low temperature for either fuel or impinging plate. To evaluate the effect of both fuel and plate temperatures on spray impingement process at ultra-low temperature, macroscopic characteristics of the impinging spray is acquired by high-speed imaging. In addition, 2D Particle Image Velocimetry (PIV) is applied to reveal transient flow structure of the impinging spray. It was found that the macroscopic morphology and radial penetration of impinging spray are still dominated by inertia at ultra-low temperature, showing little temperature dependence. However, the results of vortex analyses show that transient behavior is affected by temperatures of fuel and plate to some extent.