Influence of Lubricant Temperature, Lubricant Level and Rotational Speed on The Churning Power Loss in an Industrial Planetary Speed Reducer: Computational and Experimental Study

Influence of Lubricant Temperature, Lubricant Level and Rotational Speed on The Churning Power Loss in an Industrial Planetary Speed Reducer: Computational and Experimental Study

Franco Concli Carlo Gorla

Politecnico di Milano, Mechanical Department, Milan, Italy

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Planetary speed reducers are applied in a wide range of applications. Their main advantages are the compact design and high power density. For this reason, the demand for high efficiency gearboxes is continuously increasing and this is also why models to predict the additional churning loss, characteristic of this kind of gearing, are required. The particular configuration of the planetary speed reducers, in fact, entails an additional motion with a circular path around the gearbox axis of the planetary gears due to the rotation of the planet carrier on which they are mounted and this induces an additional source of loss. Having efficiency prediction models allows, in fact, comparison of different solutions during the design step. Literature provides some prediction models for ordinary gears but no models are still available for planetary gears. This report introduces a computational and experimental analysis of this kind of loss. Many simulations have been performed and the influence of many operating conditions like lubricant level and temperature and the rotational speed of the planet carrier have been studied. More- over, the results of an experimental testing campaign on a specially designed gearbox are presented and compared with the computational ones to validate the model. The two approaches give results in good agreement.


Churning loss, efficiency, multiphase flow simulation, planetary speed reducers, volume of fluid


[1] General Catalogue SKF –– SKF Group, December 2006.

[2] Niemann, G. & Winter, H., Maschinenelemente – Band 2: Getriebe Allgemein, Zahn-radgetriebe – Grundlagen, Stirnradgetriebe – 2. Aufl age, Springer: Berlin, 2003.

[3] ISO/TR 14179–1 and –2.

[4] Patankar, S.V., Numerical Heat Transfer and Fluid Flow, Taylor & Francis: USA, 1980.

[5] Concli, F., Gorla, C., Arigoni, R., Cognigni, E. & Musolesi, M., Planetary Speed Reducers:Effi ciency, Backlash, Stiffness, International Conference on Gears, Munich, 2010.

[6] Concli, F., Gorla, C., Arigoni, R. & Musolesi, M., Riduttori di precisione a gioco ridotto ed alta effi cienza, Organi di trasmissione – febbraio 2011, Tecniche Nuove: Milano, 2011.

[7] Csoban, A. & Kozma, M., Infl uence of the oil churning, the bearing and the tooth fric-tion losses on the effi ciency of planetary gears. Journal of Mechanichal Engineering, 56(4), pp. 231–238, 2010.

[8] Concli, F. & Gorla, C., Computational and experimental analysis of the churning power losses in an industrial planetary speed reducer. Advances in Fluid Mechanics 2012 Conference Proceedings, 2012.

[9] Concli, F. & Gorla, C., Churning power losses in planetary speed reducer: computational-experimental analysis. EngineSOFT International Conference 2012 Conference Proceedings, 2011.

[10] Concli, F. & Gorla, C., Analisi numerica e sperimentale delle perdite per sbattimento in un riduttore epicicloidale industriale, Organi di trasmissione – dicembre 2011, Tecniche Nuove: Milano, 2011.

[11] Versteeg, H.K., Malalasekera, W., An Introduction to Computational Fluid Dynamics –The Finite Volume Method, Longman Group: London, 1995.

[12] Comini, G., Fondamenti di termofl uidodinamica computazionale, SGEditoriali: Padova, 2004.