Thermo-energetic behaviour an wear of electrohydraulic compact drives
Research Task/Objectives
Electrohydraulic compact drives feature a number of concept-specific characteristics. These include a hermetically sealed circuit with a small oil volume and the absence of an active cooling. Furthermore it is aimed to do the drives without filtration as well as with a lifespan filling of oil. Under these conditions both the thermo-energetic behaviour and the wear processes are still widely unknown, nevertheless the knowledge of which is important for a temperature stable, low-maintenance and process reliable operation. Goal of the investigation is the analysis of the thermo-energetic behaviour including the simulation-based prediction of operating temperature and the analysis of wear processes in electrohydraulic compact drives.
Approach/Results
The thermo-energetic behaviour is investigated by the example of a demonstrator. A methodology is shown, which allows the simulation of the thermo-energetic behaviour of an electrohydraulic compact drive by means of a lumped parameter model in order to predict the operating temperature with reasonable computational effort. The methodology includes the thermo-energetic analysis of the drive and the thermo-energetic modelling, whereas the latter is based on a thermal resistance network, which is parameterised by the use of analytically determined heat transfer numbers only. The developed thermo-hydraulic model is validated against measurements. The results show that the presented methodology enables a satisfying accurate prediction of the thermo-energetic behaviour of electrohydraulic compact drives in order to support development, optimisation and examination of possible fields of application of electrohydraulic compact drives. On basis of simulation studies the sensitivity of the operating temperature to various influencing factors is highlighted and measures to improve heat rejection capabilities are introduced. Practicable design advices in terms of thermo-optimal design are deduced.
The wear processes in electrohydraulic compact drives are examined experimentally. Two demonstrators of different configuration absolve endurance tests of 40 days. By means of periodic oil analysis, the investigation of pump efficiency before and after the endurance tests as well as visual inspections of the pumps first insights in the wear processes of electrohydraulic compact are given and important knowledge is gained.
Measured and simulated steady-state operating temperature of the demonstrator executing a test cycle
This IGF Project 18051 BR/1 of the Forschungsvereinigung Forschungskuratorium Maschinenbau e.V. - FKM, Lyoner Straße 18, 60528 Frankfurt am Main was supported via AiF within the programme for promoting the Industrial Collective Research (IGF) of the German Ministry of Economic Affairs and Energy (BMWi), based on a resolution of the German Parliament. The final project report can be obtained from Forschungskuratorium Maschinenbau (FKM) (Mailing address: Lyoner Str. 18, 60528 Frankfurt am Main, E-Mail: info@fkm-net.de, Phone: +49 69 6603 1352).