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Experimental and numerical study on pressure oscillation in a combustor with rotary valve 被引量:2
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作者 Yunzhi XI Ningfei WANG +2 位作者 Junwei LI Zhihui ZHANG Lei HAN 《Chinese Journal of Aeronautics》 SCIE EI CAS CSCD 2021年第5期298-314,共17页
A rotary valve coupled in a combustor assembly can generate periodic pressure oscillations inside the combustor and can be used to study the combustion instability in the combustion chamber of a rocket engine.This pap... A rotary valve coupled in a combustor assembly can generate periodic pressure oscillations inside the combustor and can be used to study the combustion instability in the combustion chamber of a rocket engine.This paper proposes a cold gas flow experimental system based on a rotary valve and a corresponding rotation model.A 3 D numerical model is proposed to obtain the transient flow inside the rotary valve,and the dynamic mesh technique and User-Defined Functions(UDFs)are adopted to implement a swing motion instead of a rotary motion.Several cold gas flow experiments are carried out at rotating speeds of 75225,and 375 rpm to verify the validity of the numerical model.The effects of rotating speed,stroke length ratio and radius of the RED(Rotor Exhaust Duct)on the pressure oscillations are studied using this numerical model.The results show that the maximum and peak-to-peak values of the pressure oscillations gradually decrease with increasing rotating speed.The ratio of the corresponding peak-to-peak value to the maximum pressure(pressure amplitude ratio)is reduced from 1.81 to 0.6%.The stroke length ratio affects the pressure waveform because it leads to a change in the time spent in the non-exhaust stage.When the stroke length ratio is 0,the waveform closely resembles a sine wave.With the increase in the stroke length ratio,the pressure waveform exhibits a more square or a triangular wave shape.Finally,a high-frequency and high-amplitude pressure oscillation can be obtained by appropriately increasing the radius of the RED. 展开更多
关键词 Cold gas test Dynamic mesh Numerical simulation Pressure oscillation rotary valve
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Experimental Study on the Performance of ORC System Based on Ultra-Low Temperature Heat Sources
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作者 Tianyu Zhou Liang Hao +2 位作者 Xin Xu Meng Si Lian Zhang 《Energy Engineering》 EI 2024年第1期145-168,共24页
This paper discussed the experimental results of the performance of an organic Rankine cycle(ORC)system with an ultra-low temperature heat source.The low boiling point working medium R134a was adopted in the system.Th... This paper discussed the experimental results of the performance of an organic Rankine cycle(ORC)system with an ultra-low temperature heat source.The low boiling point working medium R134a was adopted in the system.The simulated heat source temperature(SHST)in this work was set from 39.51°C to 48.60°C by the simulated heat source module.The influence of load percentage of simulated heat source(LPSHS)between 50%and 70%,the rotary valve opening(RVO)between 20%and 100%,the resistive load between 36Ωand 180Ωor the no-load of the generator,as well as the autumn and winter ambient temperature on the system performance were studied.The results showed that the stability of the system was promoted when the generator had a resistive load.The power generation(PG)and generator speed(GS)of the system in autumn were better than in winter,but the expander pressure ratio(EPR)was lower than in winter.Keep RVO unchanged,the SHST,the mass flow rate(MFR)of the working medium,GS,and the PG of the system increased with the increasing of LPSHS for different generator resistance load values.When the RVO was 60%,LPSHS was 70%,the SHST was 44.15°C and the resistive load was 72Ω,the highest PG reached 15.11 W.Finally,a simulation formula was obtained for LPSHS,resistance load,and PG,and its correlation coefficient was between 0.9818 and 0.9901.The formula can accurately predict the PG.The experimental results showed that the standard deviation between the experimental and simulated values was below 0.0792,and the relative error was within±5%. 展开更多
关键词 ORC load percentage of simulated heat source resistive load rotary valve opening power generation
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Regulation Method for Torque-Angle Characteristics of Rotary Electric-Mechanical Converter Based on Hybrid Air Gap 被引量:1
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作者 Bin Meng Yongjiang Lai Xinguo Qiu 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2020年第2期100-110,共11页
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 c... 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. 展开更多
关键词 rotary valve rotary electric-mechanical converter Torque-angle characteristic Hybrid air gap Axial air gap Radial air gap
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Vibration Frequency Characteristic Study of Two-stage Excitation Valve Used in Vibration Experiment System 被引量:1
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作者 Yongping WU Chengwei XIONG +2 位作者 Yi LIU Jiafei ZHENG Mingxuan ZOU 《Mechanical Engineering Science》 2020年第1期30-35,共6页
To satisfy the demands of higher frequency and amplitude in hydraulic vibration experiment system,the two-stage excitation valve is presented,and a mathematical model of two-stage excitation valve is established after... To satisfy the demands of higher frequency and amplitude in hydraulic vibration experiment system,the two-stage excitation valve is presented,and a mathematical model of two-stage excitation valve is established after analyzing the working principle of two-stage excitation valve,then the influence of relevant parameters on the displacement of main spool of two-stage excitation valve is studied by using Matlab/Simulink to calculate and analyze.The results show that the displacement of main spool will be smaller with bigger diameter and more secondary valve ports.When the reversing frequency is higher and the oil supply pressure is lower as well as the axial guide width of valve ports is smaller,the maximum displacement of main spool is smaller.The new two-stage excitation valve is easy to adjust reversing frequency and flow.The high frequency can be achieved by improving the rotation speed of servo motor and adding the number of secondary valve ports;the large flow can be realized by increasing the axial guide width of secondary valve ports and oil supply pressure.The result of this study is of guiding significance for designing the rotary valve for the achievement of higher reversing frequency and larger flow. 展开更多
关键词 two-stage excitation valve rotary valve control mathematical modelling numerical analysis
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A rotary pneumatic actuator for the actuation of the exoskeleton knee joint 被引量:1
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作者 Jobin Varghese Akhil V.M. +1 位作者 Rajendrakumar P.K. Sivanandan K.S. 《Theoretical & Applied Mechanics Letters》 CAS CSCD 2017年第4期222-230,共9页
Rotary pneumatic actuators that are made out of linear one are always best suited for exoskeleton joint actuation due to its inherent power to weight ratio. This work is a modified version of knee actuation system tha... Rotary pneumatic actuators that are made out of linear one are always best suited for exoskeleton joint actuation due to its inherent power to weight ratio. This work is a modified version of knee actuation system that has already been developed and major modifications are made in order to make it more suitable for human wearing and also to reduce its bulkiness and complexity. The considered actuator system is a rotary actuator where a pulley converts the linear motion of the standard pneumatic piston into the rotary motion. To prove the capability of the actuator, its performance characteristics such as torque and power produced are compared to the required torque and power at the knee joint of the exoskeleton in swing phase and are found to be excellent. The two-way analysis of variance(ANOVA)is performed to find the effect of the throat area valve on knee angle. The ANOVA shows the significant effect of the throat area variation on the knee angle flexion made by the proposed actuator. A relationship between the throat area of flow control valve, that is connected to the exit port of the direction control valve, and angular displacement of the knee joint has been formulated. This relationship can be used to design a control system to regulate the mass flow rate of air at the exit and hence the angular velocity of the knee joint can be controlled. 展开更多
关键词 Driven pulley Flow control valve rotary Pneumatic cylinder
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Waveforms analysis and optimization of new electro-hydraulic excitation technology 被引量:3
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作者 韩冬 龚国芳 +2 位作者 杨华勇 刘毅 廖湘平 《Journal of Central South University》 SCIE EI CAS 2014年第8期3098-3106,共9页
A new electro-hydraulic exciter that consists of rotary valve and micro-displacement double-functioned hydraulic cylinder was proposed to realize different kinds of waveforms.Calculated fluid dynamics(CFD) simulation ... A new electro-hydraulic exciter that consists of rotary valve and micro-displacement double-functioned hydraulic cylinder was proposed to realize different kinds of waveforms.Calculated fluid dynamics(CFD) simulation of rotary valve orifice reveals that orifice exists the two-throttle phenomenon.According to the finding,the revised flow area model was established.Vibration waveforms analysis was carried out by means of mathematic model and the related experiments were validated.Furthermore,as a new analysis indicator,saturation percentage was introduced first.The experimental results indicate that the revised flow area model is more accurate compared to the original one,and vibration waveforms can be optimized through suitable spool parameters and the revised cylinder structure. 展开更多
关键词 rotary valve micro-displacement double-functioned hydraulic cylinder two-throttle phenomenon revised flow areamodel saturation drift motion
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