A new methodology for the prediction of the no load losses of gears: CFD and experimental investigation of the efficiency of a planetary gearbox
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Specific models to predict power losses of planetary gearboxes, in which additional churning losses arise with respect to ordinary gearboxes, 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 losses. The availability of models to predict efficiency , is of great help because it allows the comparison of different solutions since the design phase. While in literature several models for ordinary gears are available, additional work should be done with respect to planetary gears. For this reason a theoretical and experimental research programme, aimed at the definition of model for the investigation of efficiency of planetary gears has been performed. A methodology to calculate the load independent losses of gears is here presented. This methodology is based on CFD: using a VOF together with some specific tools in order to manage the discretisation of the complex geometries of a gearbox, it is possible to correctly solve the velocity and pressure field inside the gearbox. On the base of this results, the no-load power losses of a gear can be calculated. Previous works presented by the authors have shown that the accuracy of this methodology is extremely high. In addition to the general methodology a specific industrial case-study regarding an industrial gearbox has been presented. Many simulations have been performed and the influence of several operating conditions like lubricant level and temperature and rotational speed of the planet carrier have been studied. Moreover, the results of an experimental testing campaign on a real planetary gearbox are presented and compared with the computational ones in order to validate the model. The two approaches gives results in good agreement.
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Computational and experimental analysis of the churning power losses in an industrial planetary speed reducer Concli F; Gorla C (WIT press, 2012)Advantages of planetary speed reducers are well known and due to their compact design and power density they are suitable for a wide range of applications. Efficiency is becoming more and more of a main concern in the ...
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