In this study, the surface discharge current pulses of polyetheretherketone (PEEK) material under positive repetitive square voltage in a nitrogen atmosphere are measured. The influences of different voltage amplitudes and frequencies on the detail parameters of forward discharge and backward discharge current pulses are statistically analysed. The results show that as the square voltage amplitude increases, the current pulse amplitude, fall time and pulse width of both forward and backward discharge current increase, and the rise time does not change significantly. As the voltage frequency increases, current pulse amplitude, fall time and pulse width of both forward and backward discharge current decrease, and the rise time does not change significantly. Due to the independence of the discharge at different repetitive cycles, the specific discharge process in one cycle is analysed in detail to explain the influence mechanism of the voltage amplitude and frequency on the discharge current. By mean of the Richardson–Schottky and the Cavallini relaxation model, the relationship between discharge voltage ratio and surface charge, and the decay process of surface discharge are analysed. Furthermore, the influences of amplitude and frequency of the positive repetitive square voltage on the PEEK surface current pulses are explained qualitatively.
In this paper, the surface discharge current pulses of PEEK (polyether-ether-ketone) under positive repetitive square voltage are measured. The effects of voltage rise time and fall time on pulse parameters of discharge current, instantaneous voltage of discharge and time-lag of discharge are analyzed in detail. The results show that the amplitude of discharge current and the instantaneous voltage of discharge decrease, and the time-lag of discharge and the dispersion of time-lag increase with the increase of voltage rise time. With the increase of voltage fall time, the amplitude of discharge current decreases and the instantaneous voltage of discharge, the time-lag of discharge and the dispersion of time-lag increase. To analyze the influence mechanism of voltage rise time and fall time on surface discharge, the accumulation of surface charge under repetitive square voltage is regarded as a periodic process. Besides, the correlation between forward discharge and back discharge in the process of discharge is analyzed, and the development of discharge is analyzed by using the time-lag theory. Furthermore, the relationship between instantaneous discharge voltage and voltage slew rate is revealed, and the surface charge accumulation processes under different voltage rise times and fall times are compared to reveal the influence mechanism of rise time and fall time on the surface discharge under positive repetitive square voltage.
To solve the problem of valve noise, a multi-hole sleeve valve with secondary pressure-reducing function is presented in this paper. During the flow design of the valve, the flow resistance coefficient of the valve served as an important parameter. Because of two pressure-reducing components assembled to a multi-hole sleeve valve, the flow resistance coefficient of the valve changed. Thus, correction of the flow resistance coefficient had to be affected. In this paper, the relationship between the flow rate and flow resistance coefficient of the valve was first mapped and established. Then, the flow rate of the sleeve was obtained using SolidWorks simulation software. Locally refined finite element mesh technology was applied to the simulation to improve simulation accuracy. A parallel flow test platform for the regulating valve was established, and the flow rate of the multi-hole sleeve valve was detected at different openings, thus, verifying the reliability of the numerical simulation results. Finally, the simulation flow rate of the valve at different openings was substituted into the mapping relationship formula, in this way, the flow resistance coefficient of the sleeve valve was obtained. By using the modified flow resistance coefficient, the flow rate characteristics of the multi-hole, secondary pressure-reducing sleeve valve were efficiently and accurately established.
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