Experimental Analysis of the Fuel Spray Characteristics for DI High Speed Engines Using a Ram Tuned Injection System

In the application of direct fuel injection to an SI engine the fuel spray characteristics such as droplets velocity and diameter, as well as the penetration length in the combustion chamber - but especially their variation with engine speed and injected quantity - are determining criteria for a mixture formation with the required quality. These characteristics are of particular importance for high speed engines because of the large range of speed variation and become stringent for high speed two-stroke engines where a very short mixture formation time is imposed. This paper presents the results of measured spray characteristics of a ram tuned injection system using LDA techniques for different injector types and opening pressures in the range of speed and injected quantity corresponding to a representative high-speed two-stroke engine Using the ram tuned injection a constant fuel atomization and spray geometry is obtained for a large operating range of the engine, and favourable conditions for good mixture formation in compact combustion chambers, respectively for mixture stratification as well.