Jiangsu Electric Engineering Volume Flow Centrifugal Hollow Machine Constant Pressure When Flow Pressure Characteristic Curve 2.2 Air Compressor Throttle Surge Centrifugal Hollow Machine Import Pressure Change Flow Pressure Characteristics As shown, when the air compressor inlet door is fully open, it can be ignored The inlet gate throttling loss, so the air compressor inlet pressure does not change with the flow, the air compressor inlet pressure can be regarded as an atmospheric pressure. As the opening degree of the inlet door becomes smaller, the pressure difference between the inlet and the front of the inlet door will become larger, and the inlet pressure of the air compressor will gradually decrease, so the actual outlet pressure of the air compressor will also decrease, corresponding to the outlet of the air compressor. The pressure and flow curves will shift to the left, so that the actual operating point of the air compressor will gradually shift to the left. As the air compressor inlet door closes to a certain opening degree, it eventually moves to the surge zone, causing surge. This surge is called air compressor throttling, also known as minimum current surge.
Value, the air compressor will surge, this kind of surge is called natural surge. The air compressor's outlet pressure (exhaust pressure) is set to be less than the calibration pressure (natural surge pressure) during operation to avoid the surge of the air compressor.
/surge line volume flow centrifugal air compressor inlet pressure change flow pressure characteristic curve set the minimum current of the air compressor, that is, when the air volume required by the air compressor is reduced to the minimum inlet current corresponding to the inlet opening degree, the air compressor The inlet door will no longer be closed, but the bypass valve will adjust the air supply of the pipeline system, and the current of the air compressor will not be reduced, so that the air volume of the air compressor will not be reduced, thus avoiding the air compressor. The occurrence of throat surge. In order to ensure that the air compressor has a certain amount of throttling, at present, there are 4 air compressors for the first phase of the company, which are all 1CV14MX2 double-stage centrifugal air compressors produced by Ingersoll Rand of the United States. It mainly supplies the power source of each pneumatic door of the main plant in the first phase. The operation mode of the first phase air compressor is 2 sets of operation, 2 sets of standby, constant pressure control mode, that is, the air volume of the automatic tracking system is adjusted by the opening degree of each air compressor through the inlet regulating valve. When multiple air compressors are running at the same time, how to distribute the system flow and how the pressure changes are coordinated is difficult to control. If the load is improperly distributed when the air compressor is running in parallel, the flow of the single air compressor is too small to cause the surge of the air compressor. On the one hand, it affects the safe operation of the air compressor equipment, and on the other hand, it also affects the safe operation of the entire unit. In the actual operation process, the instrument air compressor D sometimes appears to be easy to surge phenomenon, the instrument air compressor A, B, C outlet display pressure is between 724730kPa, while the air compressor D is only 705kPa. The reasons and solutions for the air compressor surge are analyzed, and suggestions for improvement of the air compressor optimization operation are proposed.
1 Mechanism of air compressor surge formation Surge is the inherent characteristic of centrifugal air compressor. When the system gas pressure is greater than the air compressor outlet pressure, the check valve at the air compressor outlet is closed, the air compressor has no output, and the air is in The internal pressure of the air compressor is gathered, and the outlet pressure of the air compressor is continuously increased until the outlet pressure is greater than the system pressure, and the check valve is opened; if the check valve is opened, the air compressor does not have sufficient flow of gas to continuously output, the air compressor The outlet pressure drops again, the check valve closes again, and so on, causing the pressure of the air compressor output and the motor current to fluctuate drastically. The check valve frequently moves, and the machine makes a "squeaky" sound. This phenomenon is the air compressor. Vibration. Surging will not only affect the fluctuation of the pipe network pressure, but also cause damage to the air compressor in severe cases.
2 Air compressor surge failure analysis 2.1 Natural surge of the air compressor Centrifugal hollow machine inlet pressure is constant When the flow pressure characteristic is as shown, when the air compressor outlet pressure increases to a fixed value, the air compressor operating point is moved to On the left side of the surge line, under the operating conditions, the operating pressure of the air compressor has exceeded the maximum instrument air compressor surge that can be compressed by the air compressor. Analysis and solution Liu Lianlin, Lu Jingchun (Jiangsu Guoxin Yangzhou Power Generation Co., Ltd., Yangzhou, Jiangsu 225131, China) Preventive measures. Combined with the phenomenon that a company's air compressor is easy to surge in the first phase, the recommendation for the operation of the air compressor is given.
The minimum current setting of the air compressor is 53A. 2.3 Several reasons for the air compressor surge The natural surge and throttling of the air compressor are inherent characteristics of any air compressor. Generally, the air compressor can be used. Air compressor operating parameters are set to avoid surge. The real reason for the air compressor surge is that the system pressure is greater than the air compressor outlet pressure due to insufficient air volume entering the air compressor. The analysis is as follows.
(1) The air compressor inlet filter has a high differential pressure. The dust in the air blocks the inlet filter of the air compressor. On the one hand, the air intake of the air compressor is reduced, causing the output pressure of the air compressor to be insufficient, forming a surge fault, and the pressure difference of the filter is increased, causing the inlet pressure of the air compressor to drop. The flow characteristic curve of the air compressor is shifted to the left to increase the probability of surge. The company's first instrument air compressor specification stipulates that the air compressor inlet filter differential pressure should be less than 2.1 kPa. (2) air compressor inlet air temperature changes as shown, with the air compressor inlet temperature rise, air pressure The machine flow characteristic curve is shifted to the left, so that the characteristic curve of the air compressor is easy to approach the surge region, and the more likely the surge phenomenon occurs. The main reason is that as the temperature rises, the density of the air decreases, and the same volume of air volume, the actual compressed air flow of the air compressor decreases, resulting in insufficient output pressure of the air compressor, forming a surge phenomenon.
In actual use, summer is more prone to surge than winter.
/Brain line volume flow rate air compressor inlet temperature change flow characteristic curve (3) air cooler becomes dirty. The air compressed by the air compressor not only increases the pressure, but also increases the temperature. The outlet temperature of the first- and second-stage air compressors of the company can reach 90*C or more when it is not cooled in the cooler, so the air compressor In the two-stage cylinder, a cooler and a water-gas separator are arranged, and the high-temperature gas is cooled to below 48*C by the cooler, and the water-gas separator condenses the moisture in the gas, and condenses through the steam trap. Water is drained. Although the air compressor inlet filter can block the dust of larger particles, there are still many fine dust in the air and the particles generated by the air compressor itself are easily adhered to the cooler and the water gas separator, causing the cooler and The water vapor separator is partially blocked, resulting in a decrease in air flow, and the output pressure of the air compressor is insufficient to form a surge phenomenon. At the same time, due to the blockage of the cooler, the heat exchange effect of the cooler is affected, thereby increasing the air suction of the air compressor. The temperature, especially the blockage of the primary cooler, makes it difficult for the air compressor to draw insufficient air to form a surge phenomenon.
(4) Air compressor impeller and diffuser wear. Under normal circumstances, 70% of the pressure increase of the air compressor is completed by the impeller, and 30% is completed by the diffuser. Therefore, when the air compressor impeller and the diffuser wear out, the characteristics will be changed, and the flow angle or pressure angle of the impeller and the diffuser will change. The flow angle change mainly affects the gas flow of the air compressor, resulting in a decrease in gas flow. The pressure angle change mainly affects the output of the air compressor, which causes the output pressure of the air compressor to decrease, so that surge is easily formed.
(5) The inlet and bypass doors of the air compressor are faulty. Once the inlet or bypass door of the air compressor has a jamming phenomenon, the adjustment is not working. When the system pressure changes, it will directly cause the air compressor to surge.
3 Control and prevention of surge failure (1) Inspect the pressure difference of the inlet filter of the air compressor in time, when the pressure difference reaches the set value, stop the air compressor, replace the new filter, and prevent the air compressor. The pressure difference of the imported filter becomes larger.
(2) Since the air inlet temperature changes with the change of the ambient temperature, the inlet temperature of the air compressor is designed to be 23.5*C. In fact, the inlet temperature of the air compressor in summer is often higher than 23.5*C, but due to The parameters of the throttling surge and the natural surge of the fixed air compressor have a certain margin. Therefore, during the summer operation, the air compressor generally does not cause surge due to the increase of the inlet temperature, if it is confirmed that it is due to The high inlet temperature of the air causes the air compressor to surge, and the surge is controlled only by reducing the outlet pressure of the air compressor.
(3) Regularly clean the air compressor cooler, soak the cooler for 20h with a special cleaning agent, and then rinse it. If the effect is still not satisfactory, a new cooler should be replaced to completely solve the problem that the air compressor cooler is dirty and the air compressor output is reduced and surge occurs.
(4) Under normal circumstances, the impeller is less worn, and the diffuser is more susceptible to corrosion and wear. Therefore, the diffuser should be periodically disassembled and inspected. When the diffuser wears heavy, it needs to be replaced in time.
(5) The inlet and bypass doors of the air compressor are not flexible. Under normal circumstances, the valve is mainly caused by the valve jam. The valve can be dismantled and repaired by stopping the air compressor, so that the valve can be switched flexibly and replaced if necessary. valve. There is also a special case. Due to the defects of the system control software, the sensitivity of the valve of the air compressor is not enough, and the air compressor will surge. In this case, only the control software is upgraded to increase the reaction speed of the regulating valve. Thereby avoiding surge due to valve regulation failure.
4. Suggestions for the optimization of air compressor operation. At present, the first phase air compressor of the company is operated in parallel mode. During the operation, the air compressor D sometimes has an easy surge phenomenon, mainly two air compressors. The load distribution of the machine is uneven. When the system uses less air, the instrument air compressor D first adjusts the load through the door; when the inlet door is closed to the lowest current, further adjustment needs to open the bypass door. If the air compressor bypass door is not adjusted in time, it will appear. The phenomenon that the flow rate in the air compressor impeller is too low. In addition, due to the deviation of the air compressor D and the control software series used by the other three air compressors, the display pressure of the air compressor D is quite different from that of the other three air compressors. At present, the air compressors A and B are used. The output of C outlet shows that the pressure is between 724730kPa, and the air pressure Jiangsu motor engineering Liu Kui Lin, etc.: the reason for the surge of the air compressor used in the instrument and the solution machine D is only 705kPa. In this case, once it participates in the operation, the air pressure Machine D will be brought to the highest current operation. When the system user decreases and the pressure rises, air compressor D will close the inlet door and open the bypass door. At present, the main problem is that the opening speed of the bypass door is slow, which causes the surge of the air compressor, and no abnormality of the disintegration valve is found. The analysis should be aging of the control software and need to be upgraded.
According to the actual operation of the company, the air load of one air compressor is not enough, and the two air compressors are too many. Therefore, under the condition that the air compressor D control software is not upgraded, the adjustment of the air compressor D is minimized, and the air compressor is replaced. The set pressure of D is about 25 kPa higher than the other three air compressors, so that it is always fully loaded, thereby reducing the surge probability of the air compressor D. From the adjustment effect, the surge condition of the instrument air compressor D has improved.
To completely solve the surge problem of the air compressor D of the instrument, the air compressor D control system software needs to be upgraded to AMB control. The advantages of the control software can be calculated and analyzed according to the system pressure change, the bypass valve and the inlet. The valve can be adjusted to a certain opening at the same time, shortening the adjustment time and reducing the chance of surge. When the air compressor D feels the change of the system pressure, the valve can be quickly adjusted to avoid surge.
The company's first-stage instrument air compressor is controlled by a single air compressor. In order to reduce the surge, the motor current limit of each air compressor is increased. After the current adjustment, the surge problem of the air compressor is solved, but Increased plant power consumption and increased costs. Therefore, in order to further balance the load capacity of four air compressors, it is recommended that the first phase of four air compressors install load distribution (ASC.) centralized control system, through the installation of the system can achieve joint control of four air compressors, according to the system The pressure automatically realizes the functions of starting, loading, unloading and stopping of the air compressor; it automatically realizes the load sharing of the air compressor. It is also possible to perform real-time monitoring of the operating data of the air compressor and record all operating data curves. This not only saves electricity for the plant, but also extends the life of the motor and air compressor.
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