Flow Field Analyses And Optimal Design For Swash Plate Axial Piston Pump Of Pressure Washer

Pressure washer is a kind of fluid machinery which applies in hard spot cleaning application. It has been used broadly in North American and European area. Axial piston pump is the heart of pressure washer machine. This dissertation choose triplex high pressure swash plate axial piston pump as subject investigated base an practical optimizing requirement for pressure washer product. Motion simulation investigation and flow field CFD investigation was introduced in the dissertation, optimal design for internal passage of pump head was applied base on simulation result.Firstly, this dissertation discussed principle and mathematical model of swash plate axial piston pump. Motion simulation was investigated for swash plate and piston mechanism in pump virtual prototyping with Unigraphics software. Numeral simulation result verified the mathematical model. Odd number pistons pump is better than even number pistons pump as classical conclusion base on theory analysis. It has been verified by numeral result according to the comparison for axial piston pump from single to quintuplex pistons pump. Triplex axial piston pump was verified as the most reasonable choice for pressure washer consider to cost and practical requirements.Then, this dissertation discussed flow field inside pump head, Indicated that the flow is unsteady complex turbulent pipe flow of incompressible single phase Newtonian fluid. Inlet integrated passage and outlet integrated passage could be simplified as steady flow field with mean parameters which averaged by time. But piston cavity has a moving boundary which caused by motion of piston, so it just can discussed as unsteady periodic flow field. RNG k-epsilon turbulent model is suitable for flow field simulation inside pump head consider to practical special structure of swash plate axial piston pump. Venturi passage, integrated inlet and outlet passage was simulated base on steady model with RNG k-epsilon turbulent solution; Piston cavity flow field was simulated with dynamic mesh technology base on unsteady model with RNG k-epsilon turbulent solution. Venturi passage simulation is the main topic, the simulation result for venturi passage matched well with theory analysis and practical testing result. UDF was applied for piston cavity flow field dynamic mesh boundary; the pressure distribution during piston cavity ejection phase was simulated. In the end of this dissertation, optimal design was applied for inside passage structure of pump head base on CFD simulation result for venturi passage. Engineering prototype built and verified with practical testing, the testing results shown the optimization achieved intended goals which include decrease unloading balance pressure and reduce pressure drop of venturi passage. It makes pump got better performance.