Non-air-assisted urea dosing systems (NAUDSs) with diaphragm pump are usually used in selective catalytic reduction (SCR) systems to supply the urea water solution. The system pressure pulsation caused by diaphragm pump can significantly reduce the injecting precision of NAUDSs and further decrease the conversion efficiency of the SCR systems. Therefore, this study aimed to reduce the system pressure pulsation by installing a bladder accumulator in a NAUDS. The bladder accumulator could effectively absorb the system pressure pulsation. A numerical model was proposed to study the effects of the bladder accumulator on the pressure pulsation of the NAUDS. The software Amesim 15.0 R and ADINA 9.3 R were used to develop a new submodel for the bladder accumulator and the diaphragm pump in the NAUDS. Simulation results show that the pressure pulsation of the NAUDS mainly depended on the bladder accumulator parameter. Reducing bladder thickness, bladder elasticity modulus, and bladder accumulator stiffness significantly decreased the system pressure pulsation. When the stiffness of the bladder accumulator was lower than 5×10 11 Pa/m 3 , the pulsation ratio of system pressure reduced to below 5%. A test system was built to validate the numerical model. The test data of the system pressure showed almost the same change trend as the simulation results. Thus, the proposed numerical model can effectively predict the dynamic behavior of the NAUDS, and the results may serve as a reference for the design of similar NAUDSs.INDEX TERMS Selective catalytic reduction (SCR), non-air-assisted urea dosing system (NAUDS), diaphragm pump, pressure pulsation, bladder accumulator.

A plate-type port valve with rubber valve plate in a miniature diaphragm pump is presented. To investigate the dynamic characteristics of this type of discharge valve, a two-way fluid structure interaction model is proposed. The interaction between the dynamic behavior of the fluid and rubber is considered in the fluid structure interaction model. Based on the fluid structure interaction model, the internal flow of the pump, the deflection of the diaphragm and discharge valve plate is calculated. To verify the validity of the numerical model, a prototype pump is fabricated and tested. The experimental pressures in the working chamber of the pump show the same overall trends with the numerical results. The deviations between the numerical and experimental flowrates are less than 7.2%. The experimental results prove that the numerical model is effective in predicting a complete discharge process of the pump. There is a big difference between the deflection of the center of the valve plate and the edge of the valve plate. The oscillation period of the pressure in the working chamber of the pump is approximately double that of the discharge valve plate. When the pump speed is lower than 2500 r/min, it has little influence on the lag angles of the discharge valve under rated pressure. The lag angles at rated pump speed increase when the backpressures increase. The stress of the discharge valve plate reaches a peak when the valve plate impact on the valve limiter or valve seat.

High response, stable operation, small volume active vibration damping system and other intelligent hydraulic equipment have become the inevitable trend of future development. A compact low-pulsation gerotor pump is designed to meet these requirements, the theoretical flow pulsation of 8/9 tooth gerotor pump is analysed, and its pressure pulsation characteristics are also studied in this paper. The combined pulsation buffer is placed at the bottom valve plate high-pressure port of pumps. High-pressure oil passes through the honeycomb damping hole and enters the diaphragm volume chamber of the accumulator to form a combined pulsation buffer. Considering the effect of the pulsation buffer structure to reduce flow pulsation at different speeds, a test bench for high-speed gerotor pump pulsation characteristics is built, and the pressure pulsation of the gerotor pump with and without pulsation buffer is analysed at different speeds. Results show that the pressure pulsation frequency increases with pump speed. When the speed reaches 5500 r/min, 8/9 tooth gerotor pump without pulsation buffer outlet pressure pulsation reached 13.797% and that with pulsation buffer outlet pressure pulsation decreased to 9.871%, showing a 28.46% decline rate. At pump rotation speeds are 1500 r/min and 2500 r/min, the pulsation reduction ratios are 37.78% and 35.36%. The pressure pulsation of the gerotor pump can be evidently reduced by designing a combined pulsation buffer in this paper. Therefore, this high-speed and low-pulsation gerotor pump is suitable for active vibration damping system and other intelligent hydraulic equipment. INDEX TERMS Active vibration damping system, gerotor pump, low pulsation, pulsation buffer.

The motions of port valves are a primary aspect to consider in achieving superior reliability and performance of a diaphragm pump, and it is necessary to perform detailed analyses to stabilize the motions of port valves. A transient 3D fluid-structure interaction (FSI) model was proposed to simulate a complete working process of a diaphragm pump and the motions of port valves. The dynamic mesh technique was used, and the deformation of the diaphragm was considered. Detailed descriptions of the FSI model creation development and the simulation methodology for the diaphragm pump were provided. Based on the FSI model, the influences of the back pressure and pump speed on the dynamic characteristics of port valves were analyzed, and the flow rate of the prototype was tested under different conditions on a test rig. The simulation results indicate that an increase in the back pressure and pump speed can lead to a reduction in the flow rate. The motions of the port valves are dependent on the back pressure and pump speed, and the deformation of the diaphragm is only dependent on the back pressure. The opening lag angles of the port valves increase significantly as the back pressure increases, but they are independent of the pump speed. In addition, the opening velocities of the port valves increase with increasing back pressure and pump speed. Finally, the simulation results also show agreement with the experimental data, and the FSI simulation method can predict the dynamic characteristics of port valves in a diaphragm pump. INDEX TERMS Diaphragm pump, port valves, dynamic characteristics, fluid structure interaction (FSI), dynamic mesh technique.

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