To meet the requirements of fuel pumps with high efficiency, high power density, and low flow ripple for modern advanced aircraft, we hereby propose a two-dimensional piston pump (called 2D pump). A single piston with both rotary and linear motions is used to combine the flow distributing and volumetric varying functions together. The leakage spots are reduced to the clearance between the piston and the cylinder. As the radial force of the piston is balanced, a small piston clearance is selected to reduce leakage. Furthermore, a 2D tandem pump formed by two 2D pump units connected in series was introduced to eliminate the geometric flow ripple. The flow ripple characteristics were studied through analytical techniques, CFD numerical methods, and experiments. The results show that the flow ripple of 2D pump obtained by the measured pressure wave is 6.3%, while the pump has a high volumetric efficiency of up to 96% within a speed range of 1000-8000 r/min, indicating that reducing the leakage increases the average actual flow and reduces the flow ripple. Therefore, the proposed 2D pump is suitable for modern advanced aircraft.
The torque–angle characteristics of electric–mechanical converters are important determinants of the quality of electrohydraulic proportional control systems. It is far more difficult for a rotary electric–mechanical converter (REMC) to obtain flat torque–angle characteristics than traditional proportional solenoid, greatly influencing the promotion and application of rotary valves for electrohydraulic proportional control systems. A simple and feasible regulation method for the torque–angle characteristics of REMCs based on a hybrid air gap is proposed. The regulation is performed by paralleling an additional axial air gap with the original radial air gap to obtain a flat torque–angle characteristic and increase output torque. For comparison, prototypes of REMCs based on hybrid and radial air gaps were manufactured, and a special test rig was built. The torque–angle characteristics under different excitation currents and step responses were studied by magnetic circuit analysis, finite element simulation, and experimental research. The experimental results were consistent with the theoretical analysis. It was shown that REMCs based on a hybrid air gap can obtain a flat torque–angle characteristic with further optimizing of key structural parameters and also increase output torque. This regulation method provides a new approach for the design of proportional rotary electromechanical converters.
In order to improve the volumetric efficiency of the axial piston pump, this paper proposes a novel stacked roller 2D piston pump. It utilizes the alternate communication between the distribution cylinder and the oil intake and discharge ports of the housing to realize the flow distribution. While removing the independent flow distribution mechanism of the traditional piston pump, the leakage loss at the distribution friction pair can be reduced to improve the volumetric efficiency. Based on the flow distribution principle, an analytical model of the volumetric efficiency of the stacked roller 2D piston pump was established. Then, a co-simulation model of the whole pump was built using both the Simulink and AMESim software. The variation curve of output flow and leakage flow under different load pressures and rotational speeds was obtained, as well as the influence of backflow, axial leakage, and circumferential leakage on the volumetric efficiency. On this basis, a prototype of the stacked roller 2D pump was designed and manufactured in order to measure the output flow under different load pressures and rotational speeds, and a dedicated test bench was established. The experimental results are consistent with the simulation results; when the rotational speed is 6000 rpm and the load pressure is 5 MPa, the volumetric efficiency of the prototype pump can reach 98.6%. The research work validates that the novel stacked roller 2D piston pump has high volumetric efficiency.
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