Port and case flow temperature prediction for axial piston machines

Abstract

Researchers at Purdue’s Maha Fluid Power Research Center have developed models that will enable computational design of piston machines. The core of the in-house developed program forms multi-domain models capturing the fluid–structure interaction phenomena taking place in the main lubricating interfaces (piston/cylinder, cylinder block/valve plate, and slipper/swash plate) of axial piston machines. The model allows studying the influence of a given pump or motor design on machine performance, power loss, and energy dissipation in those main lubricating interfaces. The behavior of the fluid film in these lubricating interfaces as well as the shape of the solid parts is temperature and pressure dependent. In order to solve for non-isothermal flow and to consider elasto-hydrodynamic effects, port and case temperatures are needed as boundary condition for the model. In case of analysis and optimization of existing pumps and motors, those boundary conditions can be taken from steady-state measurements; however, when using the model to design a new unit, this information is not available. The temperature prediction model proposed in this paper fills this gap. The model can predict the outlet and case temperature for a chosen inlet temperature based on known fluid properties and calculated energy dissipation in the rotating group of an axial piston pump. The model also considers the temperature change due to fluid compression/expansion and estimated churning losses for a given axial piston machine.