Verlustanalyse am Kolben-Buchse-Kontakt von Axialkolbenpumpen in Schrägscheibenbauweise

  • Loss analysis at the piston-bushing contact of axial piston pumps in swash plate design

Gärtner, Markus; Murrenhoff, Hubertus (Thesis advisor); Schmitz, Katharina (Thesis advisor)

Düren : Shaker Verlag (2020)
Book, Dissertation / PhD Thesis

In: Reihe Fluidtechnik. D 97
Page(s)/Article-Nr.: xvii, 133 Seiten : Illustrationen, Diagramme

Dissertation, RWTH Aachen University, 2019

Abstract

The piston-bushing contact in axial piston pumps in swash plate design is highly stressed and has a considerable influence on the operating behaviour and the efficiency of the whole displacement unit. The piston-cylinder assembly shows mechanical losses, i.e. by friction forces and by friction torque, volumetric losses, like leakage and compression losses. In this work experimental, analytical and simulative methods are used to describe the losses. The experimental tests are carried out on a well-known single piston test rig in the ifas laboratory. Due to the large adjustable operating range, states under pure viscous friction but also mixed friction can be investigated. Results on axial friction force, leakage and the respective loss work are the basis of the further analysis. Using an analytical approach, the correct leakage calculation can be achieved, if appropriate values for the piston eccentricity are assumed. An improvement of the calculation result is obtained by taking the measured temperature distribution in the sealing gap into account. The compression work is calculated considering the pressure-dependent bulk modulus. The results of the multibody simulation with elastohydrodynamic coupling of the bearings offer further insights that cannot be reliably determined by tests carried out according to the state of the art. Based on three different simulation models of the single piston test rig with different complexity, the radial piston dislocation and the resulting contact pressures are analysed in addition to the loss characteristics of friction force, friction torque and leakage. The influence of the operating point and the piston rotation is given special attention. Each loss share is then plotted as a function of the operating parameters pressure and rotational speed. This shows the cause of main losses. Finally, a comparison of the analysis methods regarding the effort and the possible sources of errors are given.

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