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Numerical analysis of the lubricant gap in external gear pumps considering micro level surface features

Johan Magnusson
Göteborg : Chalmers tekniska högskola, 2011. Diploma work - Department of Applied Mechanics, Chalmers University of Technology, Göteborg, Sweden, ISSN 1652-8557; 2011:49, 2011.
[Examensarbete på avancerad nivå]

The design procedure has made the manufactures through experience aware that the tolerances in gear machines plays a significant influence on the system. In liter- ature there is only a few studies that investigates the phenomena of the geometrical micro details. This due to the complexity of the problem since it involves multiple domains and scales. This work will prove how it is possible to investigate the problem involving micro level details and the goal has been to study the effects with the aim of quantifying and proving the impact of a chamfer on the gears lateral side. The work has been performed by coupling the tooth space pressures solved by HYGESim (Hydralic Gear machines Simulator) with a numerical solver developed in an OpenFOAM environment. The simulations are carried out by solving Reynolds equations which has been proven to give accurate solutions to problems involving fluid films. Simulations involving both with and without the balancing squeeze term has been performed. Two different chamfers has been compared to a case without a chamfer at a fixed and constant gap height. The different cases are compared to each other by first separation the terms in Reynolds equation and then comparing the leakages to the drain and the power losses. It was found out that chamfer generates translational squeeze effects, which makes this study first of its kind. It was also found out that the generated hydrodynamic effects tends to increase with an increased chamfer. When it comes to the leakages, the chamfer has a positive effect, i.e decreased leakages. When comparing the power losses for one of the chamfers, the smaller one gives decreased losses while the bigger one generates increased losses. Simulations are also performed with the normal squeeze term taken into account, this to balance the generated forces by tilting the bushing. The results indicate that the hydrodynamic pressures generated to balance the bushing mainly originate from the tilt and not from the chamfer, even though the chamfer tends to decrease the maximum generated pressure and decreasing the tilt constant, t.

Nyckelord: External gear pump, lateral, bushing, CFD, openfoam, balance, gsl, reynolds



Publikationen registrerades 2011-10-04. Den ändrades senast 2013-04-04

CPL ID: 146840

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