High-pressure piston pumps are a critical component of electro-hydrostatic actuators in aerospace applications. High-speed Rotary lip/Shaft Seals (RSS) are utilised in piston pumps under low medium pressure to prevent leakage of the oil medium from the pump chamber. Although the wear behaviour of RSS has been investigated, existing studies are mainly based on the classical Archard wear model under dry contact conditions and do not account for the dynamic stiffness of surface asperities on micro-scale convex bodies. This approach characterises RSS lubrication behaviour under Mixed Lubrication (ML) conditions without considering micro-scale convex body behaviour. Thus, this study establishes a radial shaft seal model to simulate lubrication performance and tangential contact wear behaviour over a rotational speed range of 5000–10000 r/min and a temperature range of 5–60 ℃. A fluid–solid–wear coupling method is applied to the RSS to simulate micro-scale convex body deformation and its associated wear rate. The wear-induced deformation and volume loss of micro-scale convex bodies are evaluated using the roughness probability density function and interpolation. Furthermore, the description of the RSS failure mechanism associated with the leakage rate is modified beyond the classical Couette flow theory based on wear simulations. This study also re-examines the lubrication mechanism of the RSS in the ML region to clarify its role in maintaining stable suction in piston pumps, thereby extending previous studies.

Servo Motor Pumps (SMP) play a decisive role as central power and control elements for the performance limits in Electro-Hydrostatic Actuators (EHAs). Internationally renowned hydraulic companies such as Moog and Parker have introduced SMPs for aerospace and high value Industrial applications. In recent years, Chinese research in the field of high-performance SMPs has made some progress, but is still far from mature. This article provides a comprehensive overview of SMPs in terms of aerospace applications and also considers other fields such as robotics, marine and industrial applications. Based on the analyzed applications and developments, the five key performance characteristics such as high power-to-weight ratio, high dynamic range, long service life, low noise and intelligence are summarized, and the difficulties in theory and key technologies are discussed to make suggestions for high-performance EHAs and their key components.

Motor-pump assembly is the core component of the Aerospace Electro-hydrostatic Actuator (EHA). Thus, the design of the motor pump can be very challenging under conditions of high speed and wide pressure range, especially in particular working mediums. Our ultimate goal is to pursue better flow characteristics under a wide range of working conditions. In this paper, we built a sub-model of the main friction interfaces and a model of single-shaft coaxial motor-pump assembly adopting the method of hierarchical modeling. The experimental investigation of the output characteristics was mainly carried out in a phosphate ester medium environment. Then, the flow characteristics were compared and analyzed with the simulation results. Results indicated that the flow characteristics of the motor-pump assembly could be accurately simulated by the model and quite severe in a low speed and high-pressure environment.