Hydrostatic Bearing Characteristics Investigation of a Spherical Piston Pair with an Annular Orifice Damper in Spherical Pump

The spherical pump is a totally new hydraulic concept, with spherical piston and hydrostatic bearing, in order to eliminate the direct contact between the piston and cylinder cover. In this paper, the governing Reynolds equation under spherical coordinates has been solved and the hydrostatic bearing characteristics are systematically investigated. The operating sensitivities of the proposed spherical hydrostatic bearing, with respect to the piston radius, film beginning angle, film ending angle, film thickness, and temperature, are studied. The load carrying capacity, pressure drop coefficient, stiffness variation of the lubricating films, leakage properties, and leakage flow rates are comprehensively discussed. The related findings provide a fundamental basis for designing the high-efficient spherical pump under multiple operating conditions. Besides, these related results and mechanisms can also be utilized to design and improve other kinds of annular orifice damper spherical hydraulic bearing systems.

Analysis of lubrication and sealing performance on textured piston pair with multi-factor coupling

Purpose This paper aims to study the lubrication and sealing performance on the textured piston pair under the cross action of the shape and structure parameters. This paper further carries out the optimization design of low energy consumption hydraulic impact piston pair. Design/methodology/approach Based on the characteristics of the ring gap seal piston pair, the flow field analysis model of the whole film gap is established for its periodic treatment. The friction power loss of the piston pair is defined as the evaluation index of the lubrication performance and the leakage power loss as the evaluation index of the sealing performance. The orthogonal test design and CFD software were used to analyze the lubrication and sealing performance of the textured piston pair. Findings The cross action of shape and structure factors has a great influence of the lubrication and sealing performance on the textured piston pair. Clearance and shape parameters have great influence on it, while seal length and depth diameter ratio have little influence. The sealing performance of conical textured piston pair is good, while the lubrication performance of square textured piston pair is good. The primary and secondary order of influence of shape and structure on energy consumption on piston pair is B (seal clearance) > C (texture shape) > D (area ratio) > A (seal length) > E (depth diameter ratio). Originality/value Breaking the defect of local optimization design on traditional piston pair structure, then find the matching relationship of structural parameters on textured piston pair. Further improve the lubrication and sealing performance of the piston pair, and provide reference for the global optimization design of the low energy consumption hydraulic impact piston pair.

Effect of Texture on Energy Consumption for High Frequency Hydraulic Impact Piston Pair

Limited by the influence of the traditional clearance seal structure on the leakage and friction loss of the piston pair, the energy utilization ratio of the hydraulic impactor is difficult to improve. As such, a novel clearance seal structure with cylindrical texture for the impact piston is proposed to solve it. Considering the leakage and friction loss of impact piston pair, an energy consumption evaluation index is put forward. Based on the average Reynolds equation, an energy consumption analysis model for a textured high-frequency hydraulic impact piston pair is established, and the influence of piston texture parameters for the YG45 hydraulic impactor on energy consumption under rated working conditions is studied. The results show that energy consumption of an impact piston pair accounts for 29.77% of total energy loss. The variation of area ratio textured makes the ratio of energy consumption to the piston pair decline 1.32%~10.98%, where the optimum area rate textured is 0.64 ~ 0.7. The variation of depth ratio textured leads to the reduction of the ratio of energy consumption to piston pair by 3.21% ~ 5.68%, where the optimum depth ratio textured is 1 ~ 1.1.The texture structure of the piston pair significantly reduces the energy consumption of the impact piston pair, and it is an effective approach to avoid the design dilemma for the conventional impact piston pair.

Dynamic characteristics of the nozzle opening pressure based on the fluid–structure interaction for a double-solenoid-valve fuel injection system

The nozzle opening pressure of fuel injection systems affects the initial fuel atomization, the fuel injection quantity, the emission characteristics and the operation stability of diesel engines. This paper presents an investigation on the dynamic characteristics of the nozzle opening pressure for a double-solenoid-valve fuel injection system. A numerical model for the nozzle opening pressure based on the fluid–structure interaction theory is established, including the models for the physical properties of the fuel, the leakage rate of the piston pair and the elastic deformation of the piston chamber and the piston pair. Also, experiments were carried out to validate the proposed model. Good agreement was found between the simulated results and the measured results. Based on this model, the effects of some factors on the nozzle opening pressure are analysed. The results show that the rotational speed of the cam, the initial clearance of the piston pair and the sealing length of the piston pair have slight effects on the nozzle opening pressure but that the diameter of the piston, the initial fuel temperature and the residual volume greatly influence the nozzle opening pressure.

A Nonisothermal Fluid-Structure Interaction Analysis on the Piston/Cylinder Interface Leakage of High-Pressure Fuel Pump

In this paper, a nonisothermal fluid-structure interaction mathematical model for the piston/cylinder interface leakage is presented. Full account is taken of the piston eccentricity, elastic deformations of the piston pair, the nonisothermal flow in the interface, and the physical properties of the fluid such as the pressure-viscosity and temperature-viscosity effects. The numerical method for the solution of the model is given, which can simultaneously solve for the fluid pressure distribution and leakage rate in the interface. The model is validated by comparing the calculated leakage rates with the measurements. Results show the good accuracy of the model. The impacts of parameters such as the piston diameter, the initial clearance between the piston pair, and the piston velocity on the leakage rate are discussed. Some of the conclusions provide good guidance for the design of high-pressure fuel pumps.