Degradation behavior analysis of electro-hydraulic servo valve under erosion wear

This paper presents a simulation analysis method of degradation behavior for electro-hydraulic servo valve (EHSV). Unlike traditional statistical methods, our work is motivated by the failure mechanism of erosion wear. We assume that degradation trend of flow characteristic is related to structure wear in the valve components. Hence, in this paper, twin flapper-nozzle servo valve is considered as an example to analyze the degradation behavior in a simulation way. First, erosion wear rates at the precise structure are obtained in hydraulic oil of contaminant class 12 by the Computational Fluid Dynamics (CFD) models. Then, degradation trends of null leakage are simulated under different erosive wear conditions. Finally, the relationship between wear in the valve structure and degradation in null leakage is obtained by the testing data. The simulation results show that erosion wear happens at three sites i.e. the flapper surface, the nozzle outlet and sharp edges of the spool. Moreover, erosion wear of sharp edges greatly influences the flow rate of null leakage. The feasibility of our approach in analyzing degradation trend of hydraulic components is validated by the simulation experiments.