Measurement of Liquid Phase Penetration of vaporating Spray in a DI Diesel Engine 971645
This paper introduced a very simple method to measure the liquid phase of spray in an optically accessible DI diesel engine. Particular attention was paid to easy usage and maintaining the compression ratio of the real engine. As a result, a less-expensive 4 W argon laser was used as the beam source and an E-10 high-speed camera was used for continuously observing the elastic-scatter liquid phase image. Meanwhile, the compression ratio can be kept as the real engines by this method.
Through this method, the effects such as injection pressure, nozzle specification, intake air boost and temperature on liquid phase penetration before ignition were investigated. Reducing nozzle hole diameter decreased the length of the liquid phase. Increasing injection pressure hastened the evolution of liquid phase, while the liquid phase length varied complexly. Increasing intake air boost considerably shortened the liquid phase penetration and ignition delay. Higher intake air temperature also had the effect of suppressing liquid phase penetration.
LIQUID PHASE PENETRATION could be very important for designing the combustion chamber in small high speed DI engines to achieve lower emissions and higher performance. In low speed and low load conditions, avoiding the impingement of the liquid phase of sprays on the combustion chamber wall will be of benefit to hydrocarbon emission. In high speed and high load, matching the sprays with combustion chamber shape will reduce smoke emission. Therefore, for further emission reduction based on combustion improvement, the need for measuring the liquid phase penetration of the evaporating spray in DI engine is growing. In early studies, Browne et al. measured the effects of fuel properties and nozzle diameter in an IDI engine, Kamimoto et al. investigated the liquid phase with different injection pressures in a rapid compression machine. Recent, using laser elastic-scatter images, Bower and Foster  used an engine-fed combustion chamber and a copper vapor laser (8-10W) to measure the liquid phase of split injection, and Espey and Dec  investigated the effects of TDC density and temperature on liquid phase penetration in an optical-access DI diesel engine with YAG laser. All of these studies have contributed much for understanding the characteristics of liquid phase in evaporating spray, however, in the viewpoint of easy usage and maintaining the conditions close to the real engines, much work is needed. In this paper, the authors intend to introduce a very simple method using laser beam elastic-scatter imaging, by which the compression ratio can be easily maintained at that of real engine. The light source of the laser beam was a less-expensive 4W argon laser, and the elastic-scatter image of the liquid phase was recorded by an easy handling E-10 high-speed camera.
As results, the effects of nozzle hole diameters, injection pressures, intake air boosts and temperatures on the liquid phase penetration of evaporating spray were investigated. Some of the results agreed with the early studies and some new insight was obtained.