Theoretical Analysis and Design of a Variable Delivery External Gear Pump for Low and Medium Pressure Applications

[+] Author and Article Information
Srinath Tankasala

Maha Fluid Power Research Center, Purdue University, 1500 Kepner dr., Lafayette, Indiana, USA

Andrea Vacca

Maha Fluid Power Research Center, Purdue University, 1500 Kepner dr., Lafayette, Indiana, USA

1Corresponding author.

ASME doi:10.1115/1.4041351 History: Received June 07, 2018; Revised August 29, 2018


This paper describes a unique design concept, capable of electronically controlling flow delivered by an external gear pump (EGP). The principle used for varying the flow relies on the variable timing concept which has been previously demonstrated by the author's research team for EGP's operating at high pressures (p>100 bar). This principle permits varying the flow within a certain range, without introducing additional sources of power loss. In this paper, the above concept has been applied to formulate a design for a variable delivery EGP for low pressure applications (p < 30 bar), suitable for direct electric actuation. Specific design principles for the gear and the flow variation mechanisms are introduced to limit the force required by the electric actuation, and maximize the flow variation range. The low target pressure allows the variable timing principle to be realized with an asymmetric solution, with only one variable timing element present at one side of the gears. A detailed analysis concerning the relationship between the position of the flow varying element and the theoretical flow delivered by the pump is also presented. This analysis is used to formulate expressions for the flow rate and the flow non-uniformity of the pump. The paper details the design principle of the proposed pump, and describes the multi-objective optimization approach used for sizing the gears and flow variation mechanism. The paper also discusses the experimental activity performed on a prototype of the proposed unit, able to achieve a flow variation of 31%.

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