A high speed on-off valve (HSV) under the control of high-frequency pulse width modulation (PWM) can make control as linear as proportional valve do, since its valve opening is adjusted linearly by the duty ratio within a certain effective range. It is essential for HSV to achieve linear control performance precisely. In practice the performance is influenced by not only the control strategy, but also by the structural parameters of the valve, such as the valve core diameter, the conical seat angle, and so on.
In this article, it is indicated that the effects of the structural parameters on the linear control performance of HSV is exerted by flow force, because different structural parameters bring about different valve opening-flow force characteristics. Hence the relation between the valve structural parameters and the flow force is emphasized. First, the mathematical model of HSV is established, including the flow force mathematical formula being derived in detail. Furthermore, the steady flow field of the HSV is simulated via the method of computational fluid dynamics (CFD). In conclusion, the valve core diameter and the conical seat angle are the crucial structural parameters, which impact mostly the gradient of flow force versus the valve opening. Meanwhile, the linearity of the gradient decisively affects the linear control performance of the HSV. The results are verified by experiments, which constitute a meaningful reference to design HSV.