Thermal effects on the cavitation flow characteristics in the control valve for the diesel injector

Abstract

The control valve is a critical actuator component of the diesel injector, and the fuel flow characteristics within its millimeter-scale microchannels directly determine the dynamic response of the injector. The fuel within the control valve is highly prone to cavitation, accompanied by intense transient thermal effects, which in turn influence the cavitation flow. In this paper, to reveal the coupling mechanisms between thermal effects and cavitation in the control valve, the modified turbulence and cavitation model incorporating thermal effects were proposed, and a three-dimensional simulation study of the fuel flow characteristics was conducted. The results show that the fuel temperature inside the ball valve chamber increases significantly and unevenly, with the highest temperature rise of up to 115 K occurring near the surface of the ball valve chamber. The cavitation within the ball valve chamber also exhibits an uneven distribution, and it is influenced by the temperature rise distribution. Thermal effects influence cavitation in two ways. On the one hand, the temperature rise reduces fuel density, creating a large density gradient between the surface of the ball valve chamber and the central flow region. This gradient generates strong vorticity, increasing dynamic pressure and reducing static pressure, which promotes cavitation. On the other hand, the temperature rise raises the critical cavitation pressure, making cavitation more likely to occur. On the surfaces of the ball and the ball seat, the changes in temperature rise and cavitation are influenced by both position and pressure difference.