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Control valves I
Published in Ian C. Turner, Engineering Applications of Pneumatics and Hydraulics, 2020
In the field of control technology, the size and construction of the valve is of less importance than the signal generation and actuation method. Directional control valves can be of the poppet or slide type, with the poppet used for small flow rates and for the generation of input and process signals. The slide valve is able to carry larger flow rates and hence lends itself to use in power and actuator control.
A feature importance ranking based fault diagnosis method for variable-speed screw chiller
Published in Science and Technology for the Built Environment, 2022
Hailong Lu, Xiaoyu Cui, Hua Han, Yuqiang Fan, Yunqian Zhang
The working principle of a variable-speed screw compressor is shown in Figure 9. The gas refrigerant with low temperature and pressure enters the compressor from the suction end, and enters the compression space formed by the male rotor, female rotor and slide valves. The volume gradually decreases from left to right, forming the gas refrigerant with high temperature and pressure, whose temperature is the compressor discharge temperature (TR_dis）。The motor drives the rotor to rotate, and the speed is controlled by inverter, which determines the frequency of refrigerant entering the compression space. The slide valve moves left and right under the joint action of spring and high-pressure lubricating oil, and the volume of single refrigerant suction is determined by the rotor profile. The load regulation of the compressor is affected by the speed of the motor and the position of the slide valve. Because the heat generated by the motor of the compressor is taken away by the refrigerant, the suction temperature will rise after passing through the motor, and the extent of increase is related to the heat output of the motor.
Simulation platform for constant deceleration braking system based on Simulink
Published in Australian Journal of Mechanical Engineering, 2018
Li Juanjuan, Meng Guoying, Wang Aiming, Jia Yifan
The double closed-loop control transforms the roller velocity into electrical signal into the controller through the speed measuring encoder, and forms the speed closed-loop control with the given speed signal of the system, which can improve the control accuracy of the speed of the container. The output of speed closed-loop control and pressure sensor constitute pressure closed-loop control to realise accurate control of brake oil pressure. The output of pressure closed-loop is the control voltage of electro-hydraulic proportional directional valve. By controlling the displacement of slide valve of electro-hydraulic proportional directional valve, the continuous control of positive pressure between brake and brake disc is realised, and the braking effect of constant deceleration is achieved.
Heavy haul train impulse and reduction in train force method
Published in Australian Journal of Mechanical Engineering, 2018
Wei Wei, Jun Zhang, Xubao Zhao, Yuan Zhang
The main reason why brake cylinder charging speed is affected by train pipe pressure reduction speed is that the slide valve(which is located in distribution valve) displacement changes with the train pipe pressure reduction rate, as forces acting on main piston of distributing valve are directly related with train pipe pressure reduction rate. The higher pipe pressure reduction rate can cause larger forces acting on main piston, and consequently main piston moves longer distance, brake cylinder charging orifice has wider opening and brake cylinder charging speed is faster. The relationship between main piston displacement and brake cylinder charging orifice opening area for Chinese 120 (120-1 type) distributing valve is basically linear, as shown in Figure 12. Different charging rate for cars at different positions just explain the difference in main piston travels for cars at different positions in train. This also provides a basis for adjusting orifice area in accordance with piston travel distance.