Aerospace Technic and Technology

The subject of study in the article is the amount of leaks of the working fluid in the gap between the plunger and the bushing of an aircraft axial-plunger pump, depending on the position of the plunger relative to the bushing. The level of fluid leaks in the gap between the plunger and the cylinder block bushing is a component of volumetric losses, affects the thermal state, wear, the state of the plunger-bushing pair, as well as the level of pressure pulsations of the working fluid and, ultimately, the change in the efficiency of the axial-plunger pump. Researches deal with the influence of piston defects in a bushing on losses through a gap between them that is not discovered in existent literature. The aim of this work is theoretical research of the influence of piston defect on the leakage of working liquid through a gap between the piston and cylindrical bushing in aviation axial-piston pump under workloads. The tasks are: it is necessary to define the losses quantity for the three cases: the axes of piston and bushing coincide; piston is displaced (axes are parallel) with a maximal eccentricity ε = 0.99; piston is twisted in a bushing so that the edges of piston touch a bushing. For the problem-solving methods as follows were used. The task of thin film laminar flow in a gap between piston and bushing was solved by a numeral method in finite-element software. Losses on a piston are considered as a sum of the losses, related to the motion of the piston at a speed W and losses due to the pressure gradient dp/dz. The results are: to obtain the laws of geometrical parameters influence on the losses amount investigation for one piston was undertaken in the first part of the study. It is marked that most losses take place for piston displaced in parallel, and the least - for twisted. Total losses for the real pump on different operational behaviors are considered and volume loss-of-flows are obtained in the second part of the article. Conclusions. Dependences of losses through a gap at the different gap sizes and relative length of bushing for twisted piston are first time obtained. The results allow estimating the losses quantity in a pump on the efficiency of his work at planning and exploitation.

axial-piston pump; gap; piston-bushing; laminar flow; leakage; piston skew

Dotsenko, V. N., Likhosherst, I. G. Analiz nagruzhennosti i rezhimov treniya v tribosopryazhenii plunzher-vtulka gidrodvigatelya (gidronasosa) [Analysis of the loading and friction conditions of the plunger-bushing tribo-conjugation in a hydraulic motor (hydraulic pump)]. Aviacijno-kosmicna tehnika i tehnologia – Aerospace technic and technology, 2017, no. 4 (139), pp. 64–69.

Bashta, T. M. Gidravlicheskie privody letatel'nykh apparatov [Hydraulic drives of aircraft]. Moscow, Mashinostroenie Publ., 1967. 496 p.

Bergada, J. M., Kumar, S., Davies, D. Ll., Watton, J. A complete analysis of axial piston pump leakage and output flow ripples. Applied mathematical modelling, 2012, no. 36, pp.1731–1751.

Xingjian, W., Siru, L., Shaoping, W., Zhaomin, H., Chao, Zh. Remaining useful life prediction based on the Wiener process for an aviation axial piston pump. Chinese Journal of Aeronautics, 2016, no. 29, pp. 779–788.

Blackburn, J. F., Shearor, J. L., Reethof, G. Fluid power control. Cambridge, MA : MIT Press Publ., 1960. 251 p.

Zmen, Z., Sinanolu, C., Caliskan, A., Badem, H. H. Prediction of Leakage from an Axial Piston Pump Slipper with Circular Dimples Using Deep Neural Networks. Chin. J. Mech. Eng., 2020, no. 33, pp. 1–11.

Kumar, N., Sarkar, B. K., Maity, S. Leakage based condition monitoring and pressure control of the swashplate Axial piston pump. Proceedings of ASME 2019 Gas Turbine India Conference, Chennai, Tamil Nadu, India, 2019. DOI: 10.1115/GTINDIA2019-2385.

Jihai, J., Jiang, J., Kelong, W., Zebo, W., Yi, S. The impact of bushing thickness on the piston/cylinder interface in axial piston pump. IEEAccess, 2019, no. 7, pp. 24971–24977.