Abstract
External gear pumps are among the most popular fluid power positive displacement pumps, however they often suffer of excessive flow pulsation transmitted to the downstream circuit. To meet the increasing demand of quiet operation for modern fluid power system, a better understanding of the ripple source of gear pumps is desirable. This paper presents a novel approach for the analysis of the ripple source of gear pumps based on decomposition into a kinematic component and a pressurization component. The pump ripple can be regarded as the superposition of the displacement solution and the pressurization solution. The displacement solution is driven by the kinematic flow, and it can be derived from the kinematic flow theory; instead, the pressurization solution can be approximated by overlapping the pressurization flow for a single displacement chamber. Furthermore, in this way the changes of these two components with modification of the delivery circuit are determined in both analytical and numerical ways. The result of this analysis provides a good interpretation of the pulsation simulated by a detailed lumped-parameter simulation model, thus showing its validity. The result also indicates that the response of two ripple sources to the change of the loading in the downstream hydraulic circuit is very different. These findings reveal the limitation of the traditional experimental method for determining the pump ripple, that new experimental methods which are more physics-based can be potentially formulated based on this work.
Highlights
External gear pumps (EGPs) are very successful in applications that require robust and inexpensive fixed displacement machines
These findings reveal the limitation of the traditional experimental method for determining the pump ripple, that new experimental methods which are more physics-based can be potentially formulated based on this work
Like other positive displacement machines, the operation of EGPs is characterized by port flow fluctuations
Summary
External gear pumps (EGPs) are very successful in applications that require robust and inexpensive fixed displacement machines. The most significant works on dynamic lumped parameter models are represented by the contributions by Vacca and Guidetti [18], Mucchi et al [19] and their subsequent works [20,21] Both mentioned approaches were validated on the basis of experimental results, but it is important to notice their different emphasis: the CFD model provides information for local fluid flow phenomena, but the successful simulation of EGP requires high mesh density and a high computational cost. Most of the simulation methods mentioned above (both CFD based or lumped parameter) are still too complicated for an analysis involving an entire system that include the pump and its delivery apparatus This leads to the purpose of this paper, which is to propose a simplified approach to provide a basic interpretation of the pressure ripple sources and to provide a simplified method for a system modeling. More details on the model implementation and assumptions can be found in [18,20]
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