Interactions of Direct-Injection Fuel Sprays with In-Cylinder Air Motions

An experimental investigation of the effects of injector type and orientation, engine speed, in-cylinder air swirl, compression pressure, and fuel type has been conducted in motored visualization engines. A fuel-spray visualization system has been developed and utilized to obtain high-speed stroboscopic movies of the injection and penetration events. Significantly different interactions between the fuel spray and the in-cylinder air motions were found to result from changes in air-swirl ratio, nozzle geometry and injection timing. The maximum spray-tip velocity was found to occur downstream from the injector tip for all conditions tested. For applications requiring minimum fuel-spray penetration, the impinging-jet injector was found to be the most promising candidate.