Lateral Force Acting on the Sliding Spool of Control Valve Due to Radial Flow Force and Static Pressure

Abstract

The hydraulic sliding-spool valve is a key component to control the flow rates and thus pressures in different hydraulic volumes. The lateral force on the spool is one of the important effects resulting from moving resistance. This paper presents research aimed at understanding the effects of radial flow force and static pressure upon the lateral force. The radial flow force is calculated from three types of control surfaces labelled with square land, 45 • conical, and round curved surfaces, for discovering the effects of control profile, combined with inlet and outlet control conditions. The pressure difference effect is analyzed along with six cases under the same orifice opening, and the radial flow force is found to vary linearly with the pressure difference. The results also indicate that the radial force for the inlet control mode is less than that of the outlet control mode. The jet angle is discovered to not only be related to the annular orifice opening and gap clearance, but is also influenced by the flow direction and control surface profile. The static pressure is the predominant factor in the lateral force compared to the radial flow force. The results indicate that the static pressure variation on the surface of the cylindrical spool shoulder increased linearly with the inlet pressure; and two stagnation points can be observed in the case of the valve cavity with oil passages on the same section, and square land control edge profile. The lateral force on the spool increases with the pressure, and could reach to the maximum of 300 N, implying that this force should be taken into account in the selection of an actuator, especially in high pressure applications.

An Accurate Mathematical Model and Experimental Research of Pressure Distribution in the Spool Valve Clearance Film

“…Meanwhile, the volume fow leakage increases with the increase of P 1 since the volume fow leakage is positively proportional to the diferential pressure according to (16). As the sole driving energy of the spool, the diferential pressure, as shown in (21), decreases when the volume fow leakage is too much. In other words, too much volume fow leakage causes the reduction of the driving force of the spool, to reduce the dynamic characteristic of the valve:…”

“…Equation (17) presents the pressure distribution in the clearance flm between the spool and the sleeve, which can be used to calculate the lateral force by integrating the pressure P in the clearance flm, as shown in (20). Te decrease rate of the absolute value of the lateral force refects the efect of eliminating the uneven pressure distribution around the spool [21]. Te smaller the lateral force, the better the efect of eliminating the uneven pressure distribution:…”

“…Terefore, Hong and Kim [20] used computational fuid dynamics (CFD) based on the NS equation to compare spiral grooves' migrating uneven pressure distribution efects and traditional grooves. Te uneven pressure distribution was simulated for diferent inlet pressure conditions [21]. It was found that the uneven pressure increased linearly with the inlet pressure.…”

“…It was found that the uneven pressure increased linearly with the inlet pressure. Unfortunately, the study [21] did not investigate the efect of grooves on eliminating uneven pressure. Meanwhile, CFD was widely utilized to study the efect of diferent types of grooves on improving load-carrying capacity and flm stifness in gas face seals [22][23][24][25].…”

Study on the Influence of Triangular Groove Structure on Steady-State Flow Force Compensation Characteristics

“…The discharge coefficient, as a function of groove geometry, flow condition, fitting coefficients and its stable value, was deduced, proving to be quite consistent in their experimental result. Lu [13,14] researched the effects of radial flow force and static pressure upon the lateral force. The jet angle was discovered not only to be related to the annular orifice opening and gap clearance but was also influenced by the flow direction and control-surface profile.…”