Abstract
Thermodynamic aspects of hydraulic systems become increasingly important in compact systems where there is no room for heat exchangers. It is therefore desirable to facilitate temperature predictions at an early stage of the design process. In this paper two competing concepts of electro-hydrostatic actuation for aircraft applications are studied in order to examine the necessity of a heat exchanger. To be able to capture the fluid temperature in the system, thermodynamic analyses of hydraulic components have been conducted. For the modelling of hydraulic machines a comprehensive loss-model has been implemented with the intention of accurately model the machine efficiency over a wide speed and pressure range. With the help of these models the two systems have been simulated in the HOPSAN simulation package. The systems inputs have been actual pilot commands and aerodynamic loads collected from real missions. The simulation results show that depending of the ambient temperature and the mission characteristics the fl uid temperature would vary to a great extend, stating the demands of the fluid.
