| The control valve is the core part of the high pressure fuel system of diesel engines. The opening/closing of the control valve determine the connection/disconnection between the high-pressure and low-pressure fuel lines, which is to control the fuel injection process. In order to seal high-pressure fuel and achieve rapid opening and closing, the fuel system control valve is usually in the form of cone valve. When the control valve is opened, high-pressure fuel flows rapidly into the low-pressure fuel line. During this process, because the flow cross section of the control valve is small and there are great pressure difference between the valve inlet and the outlet, passenger valve mouth of small flow area and the import and export pressure, it is easy to cause the fuel vaporization to generate cavitation flow phenomenon. Cavitation will change the fuel flow cone valve area, cause the spool vibration and the pressure fluctuation in the pipeline, which influences greatly the fuel injection performance of the whole fuel injection system. In addition, the rupture of the bubbles will produce cavitation corrosion, resulting in mechanical damage to the cone valve, which affects the reliability of the fuel system.This paper takes the fuel system control valve as the research object. A visual cone valve test device was designed, and the test bench for cavitation flow characteristic test of the cone valve were set up. During the experiment, the inlet and the outlet pressure of the control valve were adjusted by a fuel pump. A high-speed video camera was used to observe the flow near the conic valve area. The mass flow rate of the control valve was based on the weighing method. The cavitation characteristics of the optical cone valve were tested under conditions of different valve openings and inlet/outlet pressures. The test results show that when the inlet pressure of the cone valve is fixed, the cavitation increases with the decrease in the outlet pressure. In the non-cavitation stage, the flow rate increases with the decrease in the outlet pressure, and the flow coefficient remains unchanged. The appearance of cavitation can lead to the saturation of flow rate and the decrease of the flow coefficient. The enhancement of cavitation will lead to the decrease of fuel discharge capacity, flow rate and flow coefficient of the valve. When the flow rate is saturated, the corresponding cavitation number is 2, and the inlet pressure does not affect the critical cavitation number. The spool opening has a great influence on the flow saturation point. The greater the degree of opening more prone to saturation. Fixed outlet pressure conditions, with the increase of inlet pressure the flow rate tends to increase mitigation and flow coefficient reduces, but does not cause flow saturation. |
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