Evaluation of the Effect of Geometry Proportional Valves on Volumetric Losses in Hydraulic Power Transmission Systems

Document Type : Research Paper

Author

• Pezhman Nikandish

Assistant Professor, Department of Mechanical Engineering, Jundi-Shapur University of Technology, Dezful, Iran

Abstract

Keywords

• Volumetric Losses
• Orifice
• Propertinal Valve
• Clearence

Main Subjects

• mechanic

EXTENDED ABSTRACT

Introduction

Proportional directional valves allow continuous control of the magnitude and direction of flow in hydraulic systems. In industrial applications, they are used to control hydraulic motors. In the spool valve, due to manufacturing inaccuracies and the need for good sliding properties, leaks occur between the spool and the sleeve. These leaks result in internal fluid leakage. Fluid leakage is undesirable but inevitable. In many spool valve applications, internal leakage is an important factor affecting the design of hydraulic systems. Internal fluid leakage can cause energy losses in the hydraulic system or unwanted movement of the unloaded hydraulic motor. Initial studies show that the geometric quantities of directional control valves affect their volumetric losses. In this paper, the effect of the clearance and diameter of the moving component, as well as the size of the proportional directional control valve, on the quantities related to volumetric losses was investigated using both experimental and analytical methods.

Materials and Methods

In this paper, at the beginning of the work, a mathematical model was presented to determine the volumetric losses in proportional directional control valves. For this purpose, it is necessary to determine three functional characteristics, including pressure sensitivity, internal leakage flow, and flow gain, in proportional control valves. To estimate the sensitivity of pressure and internal leakage flow in directional control valves, it is necessary to block the channels associated with the hydraulic actuator. In this situation, after calculating the oil flow rate through the orifices resulting from the spool movement and its clearance, it is possible to determine the oil pressure in each of the actuator ports. The pressure sensitivity of the directional control valve is obtained by evaluating the trend of changes in the oil pressure difference in the actuator ports versus the spool displacement. Similarly, in the case of blockage of the actuator ports, the volume of oil passing through the orifices resulting from the spool clearance and its displacement, at the distance between the inlet and outlet ports (P and T ports in the structure directional control valve), will be representative of the internal leakage flow in the directional control valve. Also, the flow gain of the directional control valve is obtained by calculating the oil flow rate passing through the orifices resulting from the spool clearance and its displacement, at the distance between the two actuator ports, under the condition of connecting actuator ports. Finally, in order to evaluate the accuracy of the presented mathematical model under different working conditions and to measure the quantities related to oil leakage in the directional control valve including the spool, a hydraulic power transmission system is designed and manufactured.

Findings

Investigations showed that the average difference between the results obtained from the experimental measurements of dependent quantities with analytical results is less than 5%. The evaluation resulting from solving the set of mathematical relations governing the flow passing through the orifices resulting from the spool displacement and its clearance shows that with the increase of the spool clearance, from 3μm to 4μm, and from 4μm to 5μm, the maximum oil leakage flow rate from the control valve increases, 68.6 and 48.9%, respectively. The pressure sensitivity of the valve decreased by about 34% for every 1μm increase in clearance. On the other hand, a 50% increase in the diameter of the spool resulted in a 46.7% increase in the maximum leakage oil flow rate and a 47% increase in the flow gain in the directional control valve. The maximum oil leakage in the NG16 and the NG22 valves was determined to be 2.9 and 5.5 times that of the NG10 valve, respectively. Also, the oil flow rate through the actuator ports in the NG16 and NG22 valves, in the neutral position, was 2.6 and 3.6 times that of the NG10 valve, respectively.

Conclusions

The results of the present study demonstrated the high ability of the presented mathematical model to predict the quantities related to volumetric losses in directional control valves including a spool-shaped moving component. The continuity of the process of internal oil leakage changes, pressure sensitivity and flow gain in different spool displacements, especially in the neutral position, are the advantages of the mathematical model presented in this study.

Data Availability Statement

Data available on request from the authors.

Ethical considerations

The study was approved by the Ethics Committee of the University of ABCD (Ethical code: IR.UT.RES.2024.500). The authors avoided data fabrication, falsification, plagiarism, and misconduct.

Conflict of interest

The author declares no conflict of interest.