Characterizing Spray Propagation of GDI Injectors under Crossflow Conditions

In DISI engines spray distribution and atomization directly influence mixture formation, the quality of combustion and the resulting emissions. Constant Volume Chambers (CVC) are commonly used to characterize sprays of gasoline injectors. The CVCs provide good optical access but the flow condition of the engine cannot be reproduced. Optically accessible engines in contrast deliver realistic flow conditions but have restricted optical access. In former investigations we compared the spray propagation of different injectors in constant volume chambers and in optical accessible engines. These results showed a clear difference of the spray propagation in the CVC and the engine, especially at high charge motion conditions in the engine. To find an appropriate way to investigate the impact of different charge motion a flow channel was built with adjustable crossflow velocities from 5-50 m/s. The spray propagation during the injection process was measured with high-speed shadowgraphy. Two main parameters are introduced to describe the crossflow stability. The location of the intensity center represents the global spray deflection. The second parameter is the ratio between the areas of high and low optical spray density to express the spray “blow-out” under crossflow conditions. Five different injectors were investigated at injection pressures between 100 bar and 170 bar to determine their stability and behavior under crossflow conditions. The results show a clear dependence of the spray propagation on crossflow velocities. With increasing injection pressure the stability against crossflow is increasing. Furthermore, the injectors show different behavior at the same conditions due to their different nozzle designs.