Design of Asymmetric Gerotor Pumps

Author(s):  
Andrew J. Robison ◽  
Andrea Vacca
Keyword(s):  
Author(s):  
Lozica Ivanović ◽  
Miloš Matejić

Gerotor pumps are well known by a compact design, simple structure and low noise level, which makes them suitable for use in the automotive industry, and especially in hydraulic systems for engine lubrication. One of the main disadvantages of gerotor pumps is the inability to adjust to wear, which significantly reduces the pump efficiency. In order to mitigate the negative effect of the inevitable wear process, this paper presents a methodology for determining the optimal combination of trochoid gears design parameters for a defined aspect. An appropriate mathematical model has been developed to analyze the effect of changes in gear design parameters in relation to maximum contact stresses, pressure changes in gerotor pump chambers and wear rate proportional factor (WRPF). Verification of the developed models was performed by realizing physical pairs of gears and laboratory experiments with simulation of pump operating conditions. The results and conclusions presented in this paper, with an emphasis on the actual work processes, bring very important perspectives for the gerotor pumps design with improved performance.


Author(s):  
Andrew J. Robison ◽  
Andrea Vacca

A computationally efficient gerotor gear generation algorithm has been developed that creates elliptical-toothed gerotor gear profiles, identifies conditions to guarantee a feasible geometry, evaluates several performance objectives, and is suitable to use for geometric optimization. Five objective functions are used in the optimization: minimize pump size, flow ripple, adhesive wear, subsurface fatigue (pitting), and tooth tip leakage. The gear generation algorithm is paired with the NSGA-II optimization algorithm to minimize each of the objective functions subject to the constraints to define a feasible geometry. The genetic algorithm is run with a population size of 1000 for a total of 500 generations, after which a clear Pareto front is established and displayed. A design has been selected from the Pareto front which is a good compromise between each of the design objectives and can be scaled to any desired displacement. The results of the optimization are also compared to two profile geometries found in literature. Two alternative geometries are proposed that offer much lower adhesive wear while respecting the size constraints of the published profiles and are thought to be an improvement in design.


Author(s):  
L Ivanovic ◽  
G Devedzic ◽  
N Miric ◽  
S Cukovic

This article presents the analyses of the forces and moments between gears in contact with a gerotor pump. The objective was to reach a more accurate solution for the problems related to load distribution in trochoidal pumps with fixed shaft axes. Calculation of contact forces is complex due to the simultaneous contact of several trochoidal teeth during the load transfer and additional compressive fluid forces that act on the teeth flanks. A simple physical model and a suitable analytical model are used for this analysis. Compressive fluid forces are simulated with single force applied in the middle of the line that separates the suction and upward pressure zone. During the teeth engagement there is also a change in fluid volumes between teeth. This creates pressure change that needs to be considered and calculated at an arbitrary moment of the engagement process. Finite element analysis (FEA) was used to determine the reaction forces that depend on instantaneous moments as well. Analysis shows that if a chamber pressure variation is taken into account, higher values of driving moment and support reaction forces will be generated. Designers can use the obtained results to develop a higher efficiency gerotor pumps.


Author(s):  
D C H Yang ◽  
J Yan ◽  
S-H Tong

This article presents a research on the flowrate formulation and displacement analysis of gerotor pumps. The flowrate formula is based on the deviation function and is applicable to gerotors with any pitch curves and generating curves that are either circular or non-circular. For gerotors with the circular pitch curves and generating curves, the derivation of the formula proposed here is much simpler than the current available one. Two dimensionless parameters, the lobe non-circularity and the pitch non-circularity, are then introduced so that gerotor performance can be analysed systematically. As examples, the specific flowrate and displacement curves with the combinations of sinusoidal and polynomial pitch curves and deviation functions are illustrated. Based on these case studies, it is found that in general the specific displacement increases according to the lobe non-circularity, whereas the pitch non-circularity has only the minimum effects on the performance of pumping displacement. The results of the given case studies also show that the pumps with less lobe numbers are capable to have relatively larger specific displacements.


Meccanica ◽  
2016 ◽  
Vol 52 (8) ◽  
pp. 1851-1870 ◽  
Author(s):  
M. Pellegri ◽  
A. Vacca

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Daniel C. H. Yang ◽  
Jia Yan ◽  
Shih-Hsi Tong

This paper derives formulas for evaluating the flowrate of gerotor pumps. The flowrate formulas are based on a deviation function, and the pitch and generating curves can be circular or noncircular. Two dimensionless parameters, the lobe noncircularity and the pitch noncircularity, are introduced so that gerotor performance can be analyzed systematically.


2011 ◽  
Vol 63-64 ◽  
pp. 948-951
Author(s):  
Yi Hung Tsai ◽  
Shen Jenn Hwang ◽  
Yunn Lin Hwang

This paper proposes a new type of rack-cutter can generates the circular and noncircular conjugate tooth profiles. Based on the envelope theory and coordinate transformation method, the mathematical and geometric models for the conforming rotors design are proposed. A selected smooth continuous curve equation can be assigned as the initial profile for the rack-cutter. Results from this research can be successfully applied to different kinds of tooth profile design of gerotor pumps and rotary machines.


2021 ◽  
Vol 11 (3) ◽  
pp. 1190
Author(s):  
Juan Pareja-Corcho ◽  
Aitor Moreno ◽  
Bruno Simoes ◽  
Asier Pedrera-Busselo ◽  
Ekain San-Jose ◽  
...  

In the context of generation of lubrication flows, gear pumps are widely used, with gerotor-type pumps being specially popular, given their low cost, high compactness, and reliability. The design process of gerotor pumps requires the simulation of the fluid dynamics phenomena that characterize the fluid displacement by the pump. Designers and researchers mainly rely on these methods: (i) computational fluid dynamics (CFD) and (ii) lumped parameter models. CFD methods are accurate in predicting the behavior of the pump, at the expense of large computing resources and time. On the other hand, Lumped Parameter models are fast and they do not require CFD software, at the expense of diminished accuracy. Usually, Lumped Parameter fluid simulation is mounted on specialized black-box visual programming platforms. The resulting pressures and flow rates are then fed to the design software. In response to the current status, this manuscript reports a virtual prototype to be used in the context of a Digital Twin tool. Our approach: (1) integrates pump design, fast approximate simulation, and result visualization processes, (2) does not require an external numerical solver platforms for the approximate model, (3) allows for the fast simulation of gerotor performance using sensor data to feed the simulation model, and (4) compares simulated data vs. imported gerotor operational data. Our results show good agreement between our prediction and CFD-based simulations of the actual pump. Future work is required in predicting rotor micro-movements and cavitation effects, as well as further integration of the physical pump with the software tool.


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