喷孔直径对喷雾碰壁特性的影响研究

The effect of nozzle hole diameter on wall-impinged spray characteristics was investigated under the condition of a constant injection mass. Experiments were performed in a constant volume combustion chamber using a high pressure common-rail injector with a single-nozzle hole, the diameter of which could be changed. A high-speed camera and a Schlieren visualization set-up were used to capture the behavior of impinged liquid- and vapor-phase sprays respectively. Variation laws for the radiuses, heights, and areas of the impinged sprays in both liquid and vapor phases(R_L and R_V, H_L and H_V, as well as A_L and A_v) were obtained by analyzing the images captured in the experiments, and the comparison was made of the wall-impinged spray characteristics at and after the injection end time. The results show that for a constant injection mass, the rate of spray increase before the end of injection is higher than that after the injection. A larger nozzle hole diameter causes higher spray diffusion rate and shorter injection duration. Nevertheless, the diffusion rate of R_V does not change with increased nozzle hole diameter after the injection has ended. At the injection end time, R_L, R_V, H_V, A_V and A_PV(pure vapor-phase impingement spray area) decrease with increased nozzle hole diameter, whereas H_L and A_L increase. Additionally, R_V is close to R_L, whereas H_V is much higher than H_L.