Abstract
In this paper, the dynamic evolution of cavitation flow in the solenoid valve area and the flow coefficients during the opening process of the valve in an electronic unit pump (EUP) are studied. Firstly, the pressures of high-pressure fuel and low-pressure fuel, the displacement curve of the control valve, and the flow image in the EUP in the period are obtained by an optical experiment. Then, setting the test results as the boundary conditions, a transient CFD simulation of cavitation flow in the valve region during the opening process including rebounds is carried out using dynamic mesh technology. Then the evolution and forming mechanism of cavitation during the process are analyzed. Cavitation is affected by the jet from the valve port which varies with the pressure differential, the geometry of the domain and the movement of the valve. By comparing with the mass flow rate, velocity coefficient, area coefficient and flow coefficient under conditions without cavitation and without rebound, it is found that cavitation can increase the velocity of the fuel, but significantly reduce the effective flow area, which finally affects the flow capacity of the EUP.
Highlights
With the increasing demand for low emissions and high efficiency of diesel engines, electronically controlled fuel systems need to be more stringent to meet the characteristics of ‘‘high-pressure, strong transient’’ for modern engines
Payri et al [12] investigated the internal flow in a transparent nozzle under cavitating conditions using an optical experimental system with a charge-coupled device (CCD) camera, and the results showed that the cavitation occurs before the mass flow collapse that takes place once the cavitation is fully developed through the whole orifice
The dynamic cavitation flow in the control valve area and the flow characteristics during the opening process including the rebound of the valve in an electronic unit pump are studied by optical experiments and numerical simulations
Summary
With the increasing demand for low emissions and high efficiency of diesel engines, electronically controlled fuel systems need to be more stringent to meet the characteristics of ‘‘high-pressure, strong transient’’ for modern engines. Qiu et al [1] have conducted a two-dimensional numerical simulation to study the unsteady internal flow of the control valve during the fuel-offloaded process in a EUP According to their results, cavitation occurs during the valve opening process, which induces choking flow and results in the delay of the stop of fuel injection. Another study reported that the unsteady flow in the valve is induced by the movement of the valve, and unsteady flow in the control valve greatly influences the fuel offloading process [30] These works did not consider the rebound movement of the valve caused by the high-velocity impact. The dynamic cavitation flow in the control valve area and the flow characteristics during the opening process including the rebound of the valve in an electronic unit pump are studied by optical experiments and numerical simulations.
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