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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.

An experimental study was conducted to characterize the dynamics and spray behavior of a wide range of minisac and Valve-Covered-Orifice (VCO) nozzles using a high-pressure diesel common-rail system. The measurements show that the resultant injection-rate is strongly dependent on common-rail pressure, nozzle hole diameter, and nozzle type. For split injection the dwell between injections strongly affects the second injection in regards to the needle lift profile and the injected fuel amount. The minisac nozzle can be used to achieve shorter pilot injections at lower common-rail pressures than the VCO nozzle. Penetration photographs of spray development in a high pressure, optical spray chamber were obtained and analyzed for each test condition. Spray symmetry and spray structure were found to depend significantly on the nozzle type.