The dynamic model of the gas valve takes the intake valve as an example. The working process can be roughly divided into: the end point of the expansion process. The pressure difference between the cylinder and the valve chamber pushes the valve plate away from the valve seat against the spring force, and the cylinder begins to inhale. process. The valve continues to rise until it hits the lift limiter and may bounce. When the piston approaches the dead center position, the intake speed and airflow thrust decrease, and the valve plate falls back from the lift limiter to the valve seat. According to Newton's second law, the equation of motion of the valve plate can be: m(dh2/dt2)=Fg-Fs(1) where m is the sum of the mass of the valve piece and the mass of 1/3 spring; Fg is the gas thrust; Fs For elastic force, Fs=KΔl; K is the elastic coefficient; Δl is the deformation amount; h is the lift; t is the time. Since Fg is proportional to the differential pressure Δp, the collision of the valve piece during the movement and the Fg as the excitation have a complex constraint relationship between t and h, so the motion mechanics model of the valve plate should be regarded as a nonlinear model. Since the installation area reserved for the valve seat by the cylinder is constant, if the valve lift is increased, that is, the flow area of ​​the valve gap is increased, which is advantageous for reducing the flow rate of the valve gap, reducing the pressure loss and improving the efficiency. When the lift is increased until the valve section is equal to the cross section of the valve seat, it is meaningless to increase the lift, because too high a lift will increase the impact speed of the valve and the lift limiter, affecting the life of the valve. The smaller the mass of the valve piece, the better the timeliness of the valve operation and the lowering of the impact force. However, the quality of the valve plate is limited by the area, material and strength of the valve plate. Therefore, only by selecting the appropriate parameters can the performance of the valve be maximized. Gas valve fault diagnosis and failure form The gas valve is the longest and most widely used in the compressor industry because of its easy manufacture and installation. It is a key component of the compressor working cycle, and its failure is caused by low compressor efficiency. The main reason. Due to the special nature of its working environment, the gas valve becomes a faulty component. According to statistics, more than 60% of the failures of reciprocating compressors occur on the gas valve. Therefore, the main research direction to ensure trouble-free operation of the unit should be to improve the operating life of the valve. The main components that affect the operational reliability of the valve are the spring and the valve port. According to the number of inspections of the failure parts, the valve and valve seat sealing surface failure accounted for 55%, the spring failure accounted for 27%, the valve piece fracture accounted for 9%, the valve body installation loose and other 9%. Each failure of the gas valve will cause abnormalities in the thermal performance and dynamic performance of the compressor. The failure will bring abnormal vibration and sound of the compressor, and the pressure and temperature between the stages will change. Therefore, for the thermal performance failure, the test for pressure and temperature can be diagnosed, and for the dynamic performance fault, it can be judged by analyzing the vibration and temperature signals. Among them, the vibration analysis method is a fault analysis based on amplitude, frequency, phase and correlation map after signal acquisition and data processing of mechanical vibration generated by the device. On the one hand, vibration faults have the highest probability of occurrence in all faults of the compressor; on the other hand, the vibration signal contains a wealth of mechanical and operational status information, such as rotors, bearings, couplings, foundations, pipelines, etc. Information on the state of the component during operation and information on the operating status of the speed, flow, inlet and outlet pressure, and temperature and oil temperature. In addition, the vibration signal is easy to pick up, allowing online monitoring and diagnostics to be performed without affecting unit operation. Therefore, vibration analysis is the most widely used and most effective method for compressor fault diagnosis. At the same time, the change of cylinder pressure can directly reflect the valve fault, which is an ideal diagnostic signal. The key to the actual application is the realization of cylinder pressure detection. Due to the complicated structure of the annular valve and the large number of components, it is subject to alternating shock loads at high temperatures for a long time, and is prone to failure. For valves with the same structure, material, manufacturing process and operating conditions, the service life should be similar in theory, that is, the failure time is normally distributed. The valve seat and lift limiter of the valve are generally characterized by medium to long-term failure after use, and the valve plate and spring appear to be short- and medium-term faults in use. It is concluded that due to various failures of the gas valve, the thermal performance and dynamic performance of the compressor will be abnormal. Therefore, in-depth analysis should be carried out from relevant signals such as gas temperature, pressure, flow, noise, vibration, and valve motion, so as to accurately judge the fault. the reason. Hydraulic Tipping Hopper Concrete Drum Mixer
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