Working principle and application of control valve
principle of operation
Pressure control: Take the common pressure reducing valve as an example. When the medium flows into the pressure reducing valve, the inlet pressure acts on the valve core. If the inlet pressure is higher than the set value, the valve core moves under the pressure difference, which increases the opening of the throttle, and the pressure decreases when the medium passes through the throttle, and the outlet pressure decreases accordingly until it reaches the set pressure. When the outlet pressure is lower than the set value, the valve core moves in the opposite direction, reducing the opening of the throttle and increasing the outlet pressure, so as to maintain the outlet pressure stability.
Flow control: such as throttle valve, the flow is adjusted by changing the flow area between the valve core and the valve seat. When the valve core moves, the opening of the valve port changes. According to the principle of fluid mechanics, the change of valve port area will lead to the change of fluid velocity and flow rate. For example, in the hydraulic system, the throttle valve can accurately control the flow into the actuator (such as hydraulic cylinder and hydraulic motor), thus adjusting its movement speed.
Directional control: Reversing valve is a typical control valve to realize directional control. It uses the different working positions of the valve core in the valve body to change the flow path of the fluid. The common electromagnetic directional valve makes the valve core move axially by energizing or deenergizing the electromagnetic coil, and switches different oil port communication states, so as to control the fluid to enter different actuators and realize different movement directions of mechanical parts.
application area
Industrial automation: In the automatic production line of manufacturing industry, control valves are used to control various fluid power systems, such as hydraulic systems and pneumatic systems. In the stamping, welding, assembly and other links of automobile manufacturing, the hydraulic control valve accurately controls the action of the hydraulic cylinder, and realizes the stamping forming of plates and the precise assembly of parts. In the pneumatic system, the reversing valve controls the expansion and contraction of the cylinder to complete the operations of material handling and sorting.
Petrochemical: In the process of petroleum exploitation, refining and chemical production, control valves are used to control the parameters of various process fluids. In the distillation column of an oil refinery, temperature and pressure control valves ensure accurate separation of different components. In the feed pipeline of chemical reaction kettle, the flow control valve strictly controls the feed quantity of reactants to ensure the stable chemical reaction and product quality.
Power industry: Control valves are widely used in power stations with different forms of power generation, such as thermal power, hydropower and nuclear power. In the steam system of thermal power plant, the regulating valve controls the steam flow and pressure to ensure the efficient and stable operation of the steam turbine. In the turbine speed control system of hydropower station, the control valve adjusts the opening of the guide vane, controls the water flow, and realizes the adjustment of the turbine speed and output power.
Building and HVAC: In the water supply and drainage system of the building, the pressure control valve keeps the water pressure of the pipe network stable to prevent the pipeline from being broken or the equipment from being damaged due to excessive pressure. In the HVAC system, the temperature control valve automatically adjusts the flow of hot water or cold water according to the indoor temperature to realize the comfortable control of indoor temperature. In addition, the air volume control valve in the fresh air system regulates the fresh air volume to ensure the indoor air quality.
Aerospace: In the hydraulic system of aircraft, the control valve controls the flow direction and pressure of hydraulic oil, and drives the actions of landing gear, flap, rudder and other components of aircraft. In the propulsion system of spacecraft, the control valve accurately controls the flow rate and injection direction of propellant, ensuring the smooth completion of spacecraft orbit adjustment and attitude control tasks.
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