Static characteristics of a piston-type pilot relief valve

Abstract

An oil hydraulic pilot relief valve was empirically investigated to fully understand its static performance. Constriction components which dominate the flow in the valve were individually examined in detail, revealing that the static relation between the pressure drop, flowrate and opening area for a constriction can be represented, not by the traditional hydraulic orifice equation which has always been used for the purpose, but by a new one including an additional pressure loss proportional to the flowrate and the fluid viscosity as well as inversely proportional to the square of the opening area. The new characteristic equation has consistently proved to predict the experimental findings in which a rise in oil temperature results in an increase in the piston displacement but causes little change as regards regulated pressure. It also turns out that, contrary to common preconceptions, the fluid force exerted on a poppet is negligible in the present case. It was discovered, on the other hand, that fluid force on a piston can be influential and works to increase the pilot flow.

Unsteady Characteristics of Nonlinear Pressure Loss in a Flow through a Restrictor

“…In pursuing a mathematical model of a variable restrictor free from the defect, the present authors previously found out that the product of the pressure drop and the square of the opening area is uniquely related to the flow rate by the following quadratic equation (2) (α , β ; constants independent of q, p…”

“…(1) and (2) can be used to express their dynamic ones in an unsteady flow or not. In the field of acoustics, this issue has attracted attention from the old days as the nonlinear behavior of an orifice impedance, and it has been experimentally known there that as the amplitude of an acoustic wave increases, the resistive part of the impedance increases, whereas the reactive one decreases (4) (5) .…”

Flow model and dynamic characteristics of a direct spring loaded poppet relief valve

“…Poppet valves have been extensively used in the hydraulic circuits for relief-type functions for the sake of providing safety within high-powered systems. [1][2][3][4] Compared with the spool valves, poppet valves have many advantages such as no leakage if they are closed, do not require precise machining and are capable of adjusting themselves to wear. Moreover, they are insensitive to contamination particles due to self-flushing.…”

Modeling of Dynamic Behaviors of a Poppet Valve

“…From that point of view, the present authors previously measured in detail the static relation among the differential pressure across, the flow rate through and the opening area of a poppet valve and proposed a new model for its static characteristics (3). The primary finding then was that an additional pressure loss, which is proportional to the flow rate and inversely proportional to the square of the opening area, needs to be taken into account in the modeling of the static characteristics of poppet valves.…”