耦合内部流动的喷孔积碳对柴油机喷雾影响研究

摘要

针对柴油机喷油器喷孔积碳大小及分布特点,建立了喷孔积碳条件下的内部流动模型,利用流体体积法计算了喷孔积碳对内部流动的影响.耦合内部流动计算结果,结合KH-ACT喷雾破碎模型,建立了定容喷雾模型,计算了喷孔积碳对喷雾特性的影响.利用喷油泵试验台架,通过喷油规律试验、喷雾试验对内部流动模型以及喷雾模型进行了验证.研究结果表明:喷孔内部积碳导致喷孔内部流动速度减小、空化效应减弱,造成喷雾贯穿距减小、索特平均直径减小;喷孔出口积碳导致喷孔内部流动速度增加、空化效应增强,但对喷雾贯穿距影响较小,索特平均直径在喷射初期有所增大,喷射后期变化较小.%An internal flow model is established based on the size and distribution characteristics of diesel injector nozzle deposit.The effect of nozzle deposit on internal flow is calculated by the way of VOF (volume of fluid) method.A constant volume spray model is established based on KH-ACT breakup model and the calculated result of coupled internal flow.The effect of nozzle deposit on spray characteristics is calculated.The internal flow model and spray model are verified through the injection flow-rate and spray tests on the fuel injection pump test bench.The research results show that the internal deposit could result in reducing the internal flow velocity,weakening the cavitation effect,and decreasing the penetration distance and the Sauter mean diameter (SMD).The outlet deposit leads to an increase in the internal flow velocity and the enhanced cavitation effect,whereas its effect on penetration distance is small.The SMD increases in the early stage of injection,and the change of the late stage is small.