Hydraulic piston pump in civil aircraft: Current status, future directions and critical technologies

The continued development of electro-hydrostatic actuators (EHAs) in aerospace applications has put forward an increasing demand upon EHA pumps for their high power density. Besides raising the delivery pressure, increasing the rotational speed is another effective way to achieve high power density of the pump, especially when the delivery pressure is limited by the strength of materials. However, high-speed operating conditions can lead to several challenges to the pump design. This paper reviews the current challenges including the cavitation, flow and pressure ripples, tilting motion of rotating group and heat problem, associated with a high-speed rotation. In addition, potential solutions to the challenges are summarized, and their advantages and limitations are analyzed in detail. Finally, future research trends in EHA pumps are suggested. It is hoped that this review can provide a full understanding of the speed limitations for EHA pumps and offer possible solutions to overcome them.

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A Review of High-Speed Electro-Hydrostatic Actuator Pumps in Aerospace Applications: Challenges and Solutions

Experimental investigation on the noise reduction of an axial piston pump using free-layer damping material treatment

Analysis of lubricating characteristics of valve plate pair of a piston pump

The suction dynamics of axial piston pumps become more critical if the pump is to be used at high speeds. In order to prevent air-release and cavitation from occurring within the pump it is necessary to pressurise the pump inlet. As the speed of a pump increases so will the required boost pressure, due to the extra losses incurred through the suction line and portplate at the higher flowrates. However, the lack of data regarding axial piston pump behaviour at high speeds creates problems for the system designer in telecting suitable boost conditions and for the pump designer in selecting the portplate configuration that is required to reduce fluid-borne-noise levels. This paper discusses the suction performance of piston pumps, and presents experimental and simulation results exploring the behaviour of a high-speed axial-piston pump. Different air-release and cavitation models that are suitable for simulation studies are investigated

The suction dynamics of positive displacement axial piston pumps

The electro-hydrostatic actuator (EHA) pump of aircraft is usually characterized as high speed for improved power density. High-speed condition leads to a considerable tilting inertia moment acting on the cylinder block, which has a significant effect on the cylinder block balance. Therefore, the cylinder block spline is required to be designed properly to achieve the cylinder block balance at high speed. In this research, the spline design for the cylinder block within a high-speed EHA pump of aircraft will be investigated from the perspective of cylinder block balance. The design criterion for the cylinder block spline is derived based upon the analysis of the cylinder block balance, from which distances of both spline ends from the cylinder block bottom face can be obtained. These two main distances are computed for a series of typical pump designs and then compared with the geometries of actual splines. It is shown that the proposed design criterion for the cylinder block spline corresponds well with the existing data coming from actual products. Finally, a case study on the calculation of the cylinder block spline within a high-speed EHA pump is given, and experiments will be carried out on an EHA pump prototype at speeds of up to about 10,000 rpm.

Spline design for the cylinder block within a high-speed electro-hydrostatic actuator pump of aircraft

A plunger pair friction measurement device with a rotating cylinder body mainly comprises spiral groove type capillary throttling devices, a floating liner, a flow guide boss, a ball head force measurement touch rod, a force measurement connecting rod, a connecting rod chuck, a rotatable multi-dimensional force sensor, a wireless data collection device, the cylinder body, a casing communication oil lead duct, a pressure oil lead duct and a static pressure bearing oil supply hole; the three spiral groove type capillary throttling devices which are distributed on the circumference in an equally spaced mode are used for leading the pressure oil in a plunger chamber into a static pressure chamber which is formed on the outer surface of the floating liner through the pressure oil lead duct and the static pressure bearing oil supply hole to form a static pressure bearing assembly; the cylinder body cylindrical surface of the plunger chamber area is provided with the casing communication oil lead duct; a ball head of the force measurement touch rod is embedded in the floating liner so as to transfer the friction force of a plunger to the rotatable multi-dimensional force sensor through the force measurement connecting rod and the connecting rod chuck; the wireless data collection device is fixed; a small gap is reserved between the wireless data collection device and the sensor; data are transmitted out through a cable which is arranged on the wireless data collection device.

Plunger pair friction measurement device with rotating cylinder body

The invention discloses a multifunctional testing stand for testing an oil film field parameters of a slipper pair of a plunger pump. The multifunctional testing stand comprises a handle, a small circular nut, a hand wheel, a first deep groove ball bearing, a rotating shaft, a hexagonal nut, a crank, a slide bar, a connection shaft and the like. The testing stand changes the angle of an inclined disc seat relative to a housing by rotating a first inclination angle push rod and a second inclination angle push rod, and the handle is rocked to drive a rotary inclined disc to rotate and realize transmission between shafting with changeable axes included angles. The rotary inclined disc rotates under different inclination angles, the positions of sensors installed in the rotary inclined disc relative to the elliptic locus of sliding shoes change, and some sensors (pressure sensors and current vortex displacement sensors) on fixed positions of the rotary inclined disc can be used to measure oil film field parameters on a plurality positions on the elliptic moving locus of the sliding shoes.

Multifunctional testing stand for testing oil film field parameters of slipper pair of plunger pump

A displacement sensor following mechanism for testing the thickness of a sliding boot pair oil film comprises a casing and a casing end cover; a main shaft is arranged in the casing through a bearing; the main shaft is provided with a small gear, a left gear and a right gear; the small gear is used for inputting power; the left gear and the right gear are used for outputting power; a test plunger and a reset spring are arranged in a plunger hole of a cylinder body; an axis line of the test plunger and an axis line of an auxiliary test plunger are located on the same straight line; a test sliding boot and an auxiliary test sliding boot are closely attached to the bilateral sides of an inclined plate respectively; the inclined plate is arranged on the casing through a semicircular bearing; a supporting frame is arranged in a sliding groove formed in a sliding support in a sliding and penetrating mode, wherein the sliding support can slide vertically; the supporting frame sleeves the inclined plate; a sensor installing plate and the auxiliary test sliding boot are fixedly connected with the supporting frame. According to the displacement sensor following mechanism for testing the thickness of the sliding boot pair oil film, the thickness of the sliding boot pair oil film can be continuously measured under the condition that the real motion state of the inclined plate type axial plunger pump sliding boots is simulated.

Displacement sensor following mechanism for testing thickness of sliding boot pair oil film

The invention discloses an automatic-clamping steel cable tension tester and a testing method thereof. The tester comprises a hydraulic power unit and a mechanical unit. The mechanical unit comprises a wedged clamping device, a loading guide unit and a walking device. Execution elements of the hydraulic power unit include a loading cylinder and a clamping cylinder. The free end of a steel cable is clamped directly by two wedged clamp plates of the wedged clamping device driven by the clamping cylinder. The assembly end of the steel cable is connected with a flat lug of a guide connector of the loading guide unit through a pin, the screw end of the guide connector is connected with a force sensor, and a guide is driven by the loading cylinder. The automatic clamping way driven by the hydraulic cylinder brings convenience to clamping, causes low damages to the steel cable as processes such as scattering, cleaning, hooking and lead pouring in production of steel cable samples are omitted, thereby improving stretching efficiency greatly. The automatic-clamping steel cable tension tester has the advantages of compact structure, reliable performance and high mobility, and is adaptable to quality tests of large-stroke and high-safety steel cables and components thereof before being delivered from plants.

Automatic-clamping steel cable tension tester and testing method thereof

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