This paper presents a comprehensive study to estimate the total torque losses which contribute to the hydro-mechanical efficiency in external gear machines (EGMs). A study of these losses at different operating conditions is an important design factor in prototyping many positive displacement machines to achieve efficient and reliable designs.

Although semi-empirical models for the description of the steady-state behavior of positive displacement machines accounting for both volumetric and torque losses are available in literature, their fidelity is often based on the availability of reliable experimental data. In the case of EGMs, it is difficult to consider intricate operating features such as the micro-motion of the different components in these generic models. A numerical evaluation of these special features in an EGM using dedicated models for EGMs can potentially contribute to an accurate prediction of the hydro-mechanical efficiency of a given design.

In the present work, different sources of the torque losses are methodically determined for a reference EGM unit through various numerical models which were previously developed and validated in the authors’ research team. The cumulative predictions of the torque losses from the different simulation models are then validated against the corresponding measured experimental torque losses at various operating conditions for the reference EGM unit.

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