Influence of hydraulic oil viscosity on the volumetric losses in a variable capacity piston pump

Jan Koralewski

doi:10.2478/v10012-011-0018-7

Abstract

The variable capacity piston pumps are elements of the great power and highest energy efficiency hydrostatic drives. They are used in the drive systems of ship equipment such as deck cranes, steering gears, main propulsion of smaller vessels. The laboratory and simulation investigations of the influence of liquid viscosity on the variable capacity displacement pump energy losses have not been so far performed. The paper presents results of the investigations of impact the hydraulic oil viscosity has on the volumetric losses in a piston pump operating in the full range of its capacity and oil pressure.

Highlights

A hydraulic system with variable capacity pump, as a structure allowing to change the motor speed, is a hydrostatic drive solution with the highest energy efficiency
A hydraulic drive system designer or user has at his disposal, provided only by some manufacturers, results of the energy efficiency tests of machines in the systems, tests performed with a selected oil viscosity
The relation between coefficient k1|ν calculated at the oil viscosity ν changing during the drive system operation and coefficient k1 is the following: (7). It results from the presence of two types of volumetric losses in the pump: dominating leaks of the laminar flow and leaks of not fully developed turbulent flow

Summary

Introduction

A hydraulic system with variable capacity pump, as a structure allowing to change the motor speed, is a hydrostatic drive solution with the highest energy efficiency. Coefficient k1 of the volumetric losses QPv, determined during one shaft revolution of a constant or variable capacity pump, at the pressure increase ∆pPi equal to the hydraulic system nominal pressure ∆pPi = pn and at the viscosity νn, the losses related to the pump theoretical working volume qPt, is described by the formula: (5)

Results

Conclusion