Experimental investigation and theoretical evaluation on the leakage mechanisms of seawater hydraulic axial piston pump under sea depth circumstance

Seawater hydraulic axial piston pump (SHAPP) is an important component of underwater hydraulic system. However, due to the particularity of the deep-sea high-pressure environment, the precise measurement of the SHAPP has not been carried out in the past, and there is a lack of performance evaluation of piston pump based on deep-sea test. In this paper, a testing system of the SHAPP in deep sea environment was designed and established, and the leakage mechanisms of the SHAPP is mainly studied by methods of experimental research and theoretical evaluation. The results indicated that the piston and piston bush produce micron deformation under sea depth circumstance. The compaction coefficient of plane pair (slippers/swashplate and port plate/valve plate) decreases gradually with the increase of sea depth. The main reasons why the leakage increases with the increase of sea depth under a certain load are that the clearance of the piston/piston bush becomes larger, and that the sealing of the plane pair gradually deteriorates due to the reduction of the compaction coefficient. Finally, the method of reducing leakage is given, this paper will provide theoretical and experimental reference for the design and application of the SHAPP in deep-sea environment.