The Theoretical Bandwidth Frequency of a Three-Way Hydromechanical Valve

In this paper, the dynamic characteristics of the three-way hydromechanical valve are studied using numerical and analytical techniques. The full nonlinear model for this valve is derived by taking into consideration the capacitance of the downstream load chamber and the fluid momentum effects acting on the valve. Using non-dimensional analysis it is shown that the higher order dynamics of the valve itself are negligible compared to other forces acting on the valve, and that the transient flow-forces are also of negligible size. Using this information, a reduced order model is developed for studying the bandwidth frequency in closed form and for employing perturbation techniques to identify the relative impact of various design changes for the valve. In conclusion it is shown that the most significant design change that can be made for increasing the bandwidth frequency of the valve is to reduce the load capacitance by either shrinking the load-chamber volume or increasing the fluid bulk modulus. The impact of other design perturbations is also discussed including the effect of increasing the overall valve size, the supply pressure to the valve, and the mechanical spring rate.