摘要：The control valve of a diesel unit pump fuel system adjusts the pressure of the high-pressure fuel line through rapid opening to achieve fuel cut-off control. Previous research shows that the inner flow of the control valve is a dynamic cavitation flow process, and both the inlet/outlet pressures and valve lift have great influence on this process. However, the effect of the valve needle speed on the flow characteristics is not clear. This study presents an investigation of the effect of the valve needle speed on the flow characteristics within the control valve region during the fuel offloading process of a diesel unit pump fuel system based on a homogenous two-phase unsteady flow numerical model. The results show that under the condition of same inlet/outlet pressures, as the valve needle speed increases, the cavitation intensities of both the conical region and the conical downstream region are weakened. The effects of the valve needle speed on the mass flow rate under the condition of small valve needle opening can be ignored; under the condition of large valve needle opening, the higher the valve needle speed is, the greater the mass flow rate is.
关键词：Diesel engine; control valve; cavitation; unsteady flow; valve needle speed
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