SEWHAPM: development of a water hydraulic axial piston motor for underwater tool systems

Water hydraulic motor (WHM) is an important transmission component in a water hydraulic system. Because of different physicochemical properties of raw water when compared with mineral oil, the design for the WHM would be different from that for a mineral oil one. A static equilibrium-type water hydraulic axial piston motor (SEWHAPM), which is equipped with a global-moment-balanced plate valve and a hydrostatic slipper bearing with a concentric gap damper, is developed in this research. The mechanism of the global-moment-balanced plate valve is analysed to eliminate the irregular wear of the plate valve. Next, the relevant design guideline is constructed. A mathematical model of the hydrostatic slipper bearing is established, and the performance characteristics of the bearing are discussed. The theoretical analyses indicate that the load-carrying capacity of this hydrostatic slipper bearing is not correlated with system pressure, water viscosity, temperature, or rotor speed, and that the lubrication film thickness of the bearing possesses high rigidity. The fundamental principle for designing the hydrostatic slipper bearing is also derived. On the basis of a material-screening experiment, a SEWHAPM is fabricated and tested on a water hydraulic-component-performance test stand. The experimental results show that developed SEWHAPM is feasible, with its volumetric, mechanical, and total efficiencies being similar to 86, 80, and 70 per cent, respectively, under a pressure of 10 MPa. The maximal output torque can reach similar to 19.5 N m; the maximal speed can reach 3000 r/min. As a result of the aforementioned development, the SEWHAPM has been successfully used in an underwater tool system since 2002, and its performance has been tested, demonstrating that the developed equipment can meet the regulated requirements for its practical applications.