Prediction of Case Temperature of Axial Piston Pumps

It is very important to be able to simulate axial piston pumps in order to under- stand its impact on the velocity, pressure and temperature of the lubricating oil in the pump. These variables have huge impact on the leakage in the lubricating gaps which is strongly related to the amount of power loss in the pump. This thesis main focus have been to further develop a in-house developed FSI (Fluid Structure Interacting model) software called CASPAR, which is developed by MAHA Fluid Power Research Center in order to calculate the velocity, pressure and temperature in an axial piston pump. This software has been further developed in three main research steps. One step was to develop a simplified and fast model that predicts the case temperature in an axial piston pump. The case temperature has previously been proven to have an impact on the power loss due to thermal deformation of the structure in the lubricating gaps. The calculated case temperature with this model should be used as a mixed boundary condition in the calculation tool CASPAR. The case temperature was previously taken from measurements. Measurements regarding the case temperature in an actual axial piston pump has been taken in order to analyze and validate the developed model for the case temperature. The behavior of the model has shown that the gap height is strongly influenced by the case temperature, hence the simplification to use constant gap heights in the lubricating gaps are not a valid approximation. Instead a further investigation has to be done and a recommendation to integrate the developed model with CASPAR, where both gap heights and leakage are calculated. CASPAR is divided into two parts, the Pressure Module and Gap Flow Module. These have been further developed in this thesis in order to improve the efficiency and accuracy of the calculations of axial piston pumps. This was done by using and merging previous versions of the Pressure Module in to one single version and to develop the possibility to simulate the three lubricating gaps in an axial piston pump simultaneously with the Gap Flow Module. The new single version of the Pressure Module is called the Coupled Pressure Module and it is now possible to run simulations while combining different models considering different physical effects. The simultaneous calculations of the lubri- cating gaps is called the Coupled Gap Flow Module. This has improved the time efficiency compared to independently calculated lubricating gaps. Friction forces are transmitted between the gaps in the way it is meant to be and the Coupled Pressure Module and Coupled Gap Flow Module is a part of the step against the development of the new version of CASPAR. The new version of CASPAR should be one improved version where more physics is included compared to the old versions