When the piston compressor is working normally, after the intake is completed, the suction valve is closed; the piston returns to the stroke and begins to compress the gas in the cylinder. The main point of the exhaust valve adjustment technology is to delay the closing time of the suction valve. When the piston starts to return stroke, part of the gas is pushed back to the intake line by the piston. Since the pressure on both sides of the suction valve is not much different during this process, the energy consumption for discharging this part of the return gas is small. When the gas return flow meets the requirements, the suction valve is closed and the gas in the cylinder begins to compress normally. The thrust generated by the hydraulic or pneumatic mechanism acts on the unloading spring, which in turn pushes the fork to open the suction valve. The suction valve piece of this process is subjected to force analysis. The suction valve piece mainly has the following three forces: (1) the force applied by the valve spring to close the suction valve piece; (2) the top applied by the pressure fork The force of opening the suction valve piece; (3) the top thrust applied by the gas flowing through the gas valve, wherein the intake process is the direction of the top open valve, and the return process is the direction of closing the valve. When the pressure of the fork is equal to zero, the intake valve has no opening when the intake is completed, the gas return flow is zero, the compressor works at full load, that is, the rated power; when the pressure of the fork is a certain value greater than zero, After the gas is completed, the valve plate maintains a certain degree of opening, and some of the gas is recirculated, and the compressor realizes partial load work, that is, unloading work. The body reflux flow rate is approximately proportional to the piston movement speed. When the reflow starts, the reflux speed is small. As the piston speed increases, the gas flow rate also increases correspondingly, and the resulting top thrust also increases accordingly. When the sum of the spring force and the valve spring force is just greater than the fork unloading force, the suction valve begins to close, and then the gas valve is completely closed. The gas pressure in the cylinder then rises sharply, ensuring that the valve plate is no longer open. When the piston is running close to the middle of the stroke, its running speed reaches the maximum value, and the gas top thrust also reaches the maximum value. Then the piston movement speed is gradually reduced, and the gas top thrust is also reduced. Therefore, the force of the fork that closes the valve plate when the returning gas reaches the maximum thrust is called the maximum fork force. Adiabatic efficiency analysis Due to the delayed closing of the suction valve, the mechanical partial compression section of the compressor unloading working fluid moves to the left, and the adiabatic efficiency is slightly reduced. Compared with the normal compression, the intake resistance loss is almost unchanged; due to the partial gas return, the suction valve return resistance loss is increased; at the same time, the exhaust volume is reduced, and the exhaust resistance loss is reduced. In summary, the total valve resistance loss remains almost unchanged. If the ratio of the adjusted exhaust volume to the rated exhaust volume is r, then when r=100%, the adiabatic efficiency has the following formula: W compression work adiabatic compression work, actual compression work, compression loss during valve compression, when r is equal to some For a value of X, as mentioned above, only W is reduced, so the adiabatic efficiency is: for example, if the valve resistance loss of a compressor is 5%, when the rated displacement is running, the adiabatic efficiency is: When the displacement is reduced to 60% of the rated displacement, the adiabatic efficiency is: In order to reflect the energy-saving effect of the exhaust valve adjustment system of the top open suction valve, the test workshop of the electric repair workshop of a refinery inspection company adopts D26A electromagnetic The galvanometer (accuracy 0.5) was field tested. Exhaust volume current power ratio power (discharge amount / power) exhaust gas rate reduction rate can be seen, while the compressor displacement is reduced, the motor power is also reduced, that is, the specific power of the compressor is basically maintained. The same, fully reflects its energy-saving effect. Exhaust volume adjustment range Piston compressor In the rated exhaust capacity condition, the calculation formula of the displacement of the piston reciprocating one week is as follows: the gas temperature in the intake line of the T intake line is the gas density in the intake line. The volume coefficient of gas temperature is partially unloaded under the exhaust gas condition. Because the intake valve is delayed, the effective volume coefficient of the cylinder is reduced. The temperature in the intake line is increased from T to T1, and the temperature in the cylinder is T. The calculation of the gas volume is: due to the change of the corresponding value compared with the rated exhaust gas condition, the engineering can be considered equal, then the formula for calculating the displacement adjustment ratio is: Obviously, the higher the volumetric efficiency, the displacement The adjustment range will be larger. Other major factors affecting the range of exhaust gas regulation are: (1) gas compressibility. When the piston speed reaches a maximum value, the top pressure of the return gas has not reached a maximum due to the compressibility of the gas. Obviously, the greater the compressibility of the gas, the greater the time difference between the two, and the greater the range of adjustable displacement. (2) The inertia force of the air valve and the moving parts of the fork. Due to the inertial force of the valve and the moving parts of the fork, it takes a certain time for the valve to close. If the parameters are not properly selected, there is a large rebound after the valve is closed. These will increase the exhaust volume adjustment range. (3) Pressure fluctuations in the intake line. Due to the viscous force of the lubricating oil in the gas valve, the closing motion of the gas valve is generally caused by the fluctuation of the gas pressure in the cylinder, that is, when the pressure difference between the inside and the outside of the valve plate is almost zero, slight gas fluctuation can break the balance. This causes the valve to begin to move. When the displacement adjustment is small or large, the pressure difference between the inside and the outside of the valve is small, and the valve is easily advanced or delayed. Considering the safety factor, the displacement adjustment should not be too large. In recent years, with the wide application of electronics, control and computers, the top-opening suction valve displacement control system has been developed to automation and safety, and its application has many new features. The application of the electronic control system for the top-opening suction valve is generally composed of an industrial computer, a programmable controller and a valve opening mechanism. The upper industrial computer and the lower programmable controller form a closed loop control system. Industrial applications are typically integrated into large DCS control systems or by individual industrial PCs. The main advantages of such systems are: (1) The parameter control response period is very short, and generally can meet the requirements of less than 0.1s. For general displacement adjustment, this response speed is fully achievable. (2) The closed-loop PID control algorithm is simple and practical, and the ordinary differential integration algorithm can be realized. (3) The entire control program is highly integrated and easy to update. Strength Analysis of Forced Components The core force components of this system are the press fork, the fork spring and the valve plate. The valve plate hits the valve seat when the valve is closed. This impact speed is an important parameter affecting the life of the valve. For the stepless adjustable return air valve, the valve impact phenomenon has been significantly improved. This is because the fork member has a certain mass and, when moved together with the valve plate, the acceleration of the valve plate is significantly reduced by the same amount of force as before. At the same time, the polarization of the valve plate almost completely disappears due to the good guiding action of the fork part. Due to the different forces on the sides of the valve when the valve is closed, the valve plate and the fork will have some stress and deformation. Therefore, it must be finite element analysis to determine whether the stress and deformation of the valve plate and the fork meet the material requirements. Noise Elimination The top-opening intake valve displacement control system has a unique phenomenon, namely impact noise. This is caused by a secondary impact of the fork after the valve is closed. During the closing process of the suction valve, the pressing fork and the valve piece hit the valve seat at a certain speed, the valve piece stops moving, the top thrust acting on the pressing fork disappears, the pressing fork moves in the opposite direction, and hits the valve piece. At the same time, since the gas valve is closed, the pressure in the cylinder rises sharply, and the gas pressure acting on the valve plate gradually increases. When the fork hits the valve, the valve opens a small lift and then closes rapidly under increasing gas pressure. Impact noise is generated thereby. Applying the principle of spring oscillator, the pre-compressed spring mechanism is evenly distributed on the fork, which can effectively buffer the secondary impact of the fork on the valve plate, thereby eliminating the impact noise. Application of valve plates and forks to non-metallic materials Conventional valve plates are made of metal. Generally, metal materials have large defects in wear resistance, high temperature resistance and fatigue strength. The application of non-metallic materials for valve plates has been relatively mature, and many manufacturers have begun to use them widely. The fork metal is still in the trial stage. The non-metallic materials currently used to make press forks are mainly: polyimide (PI), polyphenylene sulfide (PPS) and polyetheretherketone (PEEK). Among them, polyetheretherketone is a new type of high temperature resistant material which has been developed recently. Its corrosion resistance, dimensional stability and load carrying capacity at high temperature are superior to general metal and non-metal materials. The application of such materials is still in its infancy. For specific forks, linear (or nonlinear) finite element analysis and material mechanical properties experiments must be performed to check whether the materials meet the requirements. System Work Process The main advantage of computer simulation computer simulation is that it replaces a large number of experiments and can quickly optimize the parameters. When performing computer simulation, first establish a simple (or complex) mathematical model, then program, use the computer to calculate the working condition of the valve under certain parameters, in order to get several key data: the stepless adjustment range of the exhaust volume , changes in adiabatic efficiency and changes in the temperature of the outlet gas. Conclusion (1) When the compressor is large and the gas valve resistance loss is small, the application of the top opening suction valve displacement adjustment technology can make the compressor power consumption and its exhaust volume close to proportional change, showing its excellent energy saving effect. . (2) The top-opening suction valve exhaust gas volume adjustment system is easy to install, and the compressor gas valve modification process is simple and reliable, and it is becoming an indispensable key technical equipment for the compressor. 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