| Centrifugal compressor is petroleum chemical industry,fertilizer,pharmacy,metallurgy and so on widely application of the fluid flow impeller rotating machinery,as part of the turbine compressor.In chemical industry production occupies very important position.As in recent years the rapid development of domestic chemical industry,metallurgy and other industries,centrifugal compressor toward the direction of wide flow range and high efficiency.Surge is the inherent characteristics of a centrifugal compressor,it limits the development of centrifugal compressor.The event of a surge of unit as in the whole process of fluctuation is severe,sometimes needs several hours to once again to process adjustment to the state before the surge,surge of compressor damage is larger.In the article,introduces the zhenjiang a site running problems of ammonia pressure unit.The ammonia compressor anti surge control system existence question,resulting in the surge backflow perennial closed tightly.Both the surge valve opening at about 30%,large flow back,a preliminary calculation about 40%of the compressed gas is used for playing back,severe waste of energy consumption.This type of compressor running field problems throughout the country,and the vast majority of customers have not yet realized the problem.Countries are now vigorously advocating energy conservation and emissions reduction,a set of excellent anti surge control system can save a lot of annual energy consumption and reduce carbon emissions.Fixed limit flow method and the variable limit flow method is the most commonly used of the surge,to control the PI or PID control unit.The first method of defect was the cause of the host polytropic efficiency drops,cause the waste of energy;The second method of flaw is that its stability is poor.The traditional PID controller in control compression on the pant has certain limitation,control performance is limited by the setting of parameters,and quick and overshoot amount both there is a problem.At the same time fuzzy control,adaptive control,predictive control and other advanced control technology with the development of control theory.Based on abundant actual operation experience in natural language and expression,the control method is to use higher frequency fuzzy control,fuzzy control is a kind of fuzzy set and fuzzy logic reasoning is converted to digital or digital function and then use the computer to realize control.In this paper,fuzzy control model is established using fuzzy controller to use input quantity and value of both poor and poor rate to complete.With a gear as medium packaged air compressor machine as the prototype,applies only to build up a set of inlet flow rate as control variables of anti surge control system,because of the air compressor inlet conditions relative to other machine is stable and the inlet directly to the atmosphere and inlet pressure,inlet temperature and component of medium is stable,the inlet temperature may change is big,but the relatively small impact on unit surge line.This set of anti surge control system for inlet flow and the surge set flow difference and difference of the derivative of the fuzzy controller of two input,to prevent the surge of the valve opening for the output value,which set the surge flow is done through online number now.The fourth chapter ending reuse on the MATLAB simulation,the construction of a simulation model and the practice situation,inlet flow has given a time for the curve of the 50 s,flow value once every 5 s change,more than the value of the surge flow are also less than the value of surge flow.Anti surge valve to as a simple inertial link processing,the proportion of its delay time is set to 0.05 seconds.Simulation results show that the system can be adjusted according to change in the flow unit imported anti surge valve opening,when the surge line close to the valve switch speed is slow,make whole compressor exit pressure fluctuation is too big,at the time of the surge line far distance,the surge valve open quickly,quickly out of danger,to ensure the safe operation of the unit.Finally using Siemens PLC to realize the anti surge control systems,this system has obtained the good effect of operation on the spot,in the past most of the gear air compressor users are beat anti surge control system to manual mode,automatic mode,like chicken ribs,reason is not only intelligent control systems:if in automatic mode operation process pipe network's volatility,is not conducive to production;Manual mode can guarantee the process pipe network fluctuation is not big,but when surge happened,operators need to manually open the anti surge valve,increase the work intensity of the relevant personnel,there is no guarantee that the first time to exit the surge,has brought the unit running a big risk.The surge of fuzzy control system is effective to solve the two problems,neither let the process pipe network's volatility,and ensure the safety of the unit. |
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