Effect of Fluid Visco-Temperature Properties on Pilot-Operated Relief Valve Stability

The viscosity of fluid varies with temperature, and the dynamic behavior of the relief valve may be impacted in this situation. After obtaining the oil visco-temperature properties, the dynamic mathematical model of a pilot-operated relief valve is derived. To obtain the effect of the visco-temperature properties on the stability of pilot-operated relief valves, the system transfer function block diagram is constructed. The frequency-domain analysis method was then utilised to investigate its dynamic behavior. The results suggest that the viscosity of the oil is thin at high temperatures, resulting in low flow resistance in the dynamic feedback orifice. In this case, the mass-spring vibration system composed of the main poppet and mechanical spring has a natural frequency close to the relief valve’s operating frequency, which is not conducive to the stability of the relief valve. The oil inside the main valve spring chamber, however, is equivalent to a liquid spring with an extraordinarily high stiffness since the viscosity of the fluid is thicker at low temperatures, which decreases the flow capacity of the orifice. The main valve’s mass spring vibration system has a natural frequency in this instance that is significantly higher than the valve’s operating frequency, enhancing the stability of the relief valve. Finally, the numerical simulation results demonstrate the rationality of the theoretical analysis.