电控单体泵锥阀下游区域瞬态流场变化特性研究

Change Characteristics of Transient Flow Field in Poppet Valve Downstream Area of Electronic Unit Pump

电控单体泵导通高低压油路时,锥阀区域流场十分复杂,对泄压断油特性影响比较大,为了研究电控单体泵喷油系统回油过程中锥阀下游区域瞬态流场的变化特性,利用高速摄像方法,对锥阀下游流场进行了可视化试验,提取空化泡群的边界轮廓并计算其亮度,对其空化周期时间和亮度变化进行了分析,并结合Fluent软件对瞬态流场变化进行了仿真计算。结果表明:随着凸轮转速的增加,锥阀下游区域流场发生空化现象的平均空化周期时间近似呈线性减小,平均亮度逐渐增大;随着锥阀阀芯的往复运动,锥阀下游区域出现多个涡流区域,并不断变化;在怠速工况(500 r/min),平均空化周期时间和波动标准偏差最大,分别为4.5 ms和0.15。

Electronic unit pump system is a type fuel injection system with high injection pressure which can be applied to control fuel quantity and timing of insection flexibly. The solenoid valve in the electronic unit pump（ EUP） controls pressure buildup within the high-pressure fuel line. When it is open,high-pressure fuel transfers with high velocity from the narrow cross-section into the low-pressure fuel line. During its operation,the flow in the field of solenoid valve is quite complex that affects the performance of EUP. In order to study the change characteristics of transient flow fields in poppet valve downstream area during the oil return process of an electronic unit pump injection system,a diaphanous glass window was designed in the pump. High-speed photography was introduced to visually investigate the transient flow fields. By means of experiment data,extracted the cavitation image boundaries and calculated the brightness of the cavitation bubble clouds,the cavitation periodic time and the change of brightness were analyzed and calculated. The test results show that with the increase of the cam rotational speed,the average cavitation periodic time was decreased almost linearly,and the average brightness was increased gradually. At the idle condition（ 500 r / min）,the average cavitation periodic time and the standard deviation of fluctuation are maximum,which are 4. 5 ms and 0. 15 respectively. Furthermore,the simulation was conducted based on the test data such as the pressure and the displacement of valve core. The simulation results of cavitation phenomenon occur along opening process of valve. In the process of reciprocating motion of valve core,several swirling regions appear in the flow field of poppet valve downstream area,and keep constantly changing. The streamlines have significant influence on swirling regions.