Research and 3-Dimensional Numerical Simulation about Internal Air Transient Flow Process and Air Flow-Induced Noise of Engine Electronic Control Throttle Quick-Opening Process

Based on the basic structure and operating function of engine throttle, according to the actual structure of throttle, a 3-dimensional air transient flow is simulated to realize throttle rotated from closed position to opened position by using CFD moving mesh technology and user defined program. By applying CFD and CAA coupling method, the influence of the movement of throttle on air flow and flow-induced noise process are studied, the transient opening process is studied and analyzed. The velocity field, pressure field and the principle of flow-induced noise are analyzed under different rotational angle velocity of throttle. Numerical simulation results show that at the beginning period of throttle rotation, two antisymmetric eddy appears in the flow field behind the throttle, the pressure drops distinctly between the front and the back of throttle, the two flow-induced noise fields appear near the top and bottom position of throttle and transmit towards the downstream and then merge gradually, the maximum value of acoustic power appears when the throttle opening near 40°. The velocity field, pressure field and flow noise become steady gradually when throttle is opening completely. The flow-induced noise time-frequency domain numerical simulation results show that the throttle flow-induced noise is a kind of mainly middle and low frequency broadband noise, the main part of noise is below 100 Hz low frequency noise. To clarify the effect of air flow on noise, the three operating conditions of the throttle opening time of 0.5 s, 1 s and 2 s are analyzed respectively, the results show that the sound pressure below 100 Hz is less affected. Reducing below 100 Hz low frequency noise is the key role for the flow-induced noise control of throttle.