Surge control line dynamic adjusting method of magnetic suspension centrifugal air compressor

Abstract

A surge control line dynamic adjusting method of a magnetic suspension centrifugal air compressor comprises the following steps that when the magnetic suspension centrifugal air compressor is started for the first time, the magnetic suspension centrifugal air compressor operates at rated power; recording the rotating speed n0 of the motor under the rated power, the current I0 under the rated power, the vibration value U0 of the rotor under the rated power, the initial air inlet pressure value Pin and the initial air inlet temperature value Tin; then actually measuring and setting a surge control line; in the actual use process, the surge control line is adjusted according to the current air inlet pressure value Pin'and the current air inlet temperature value Tin, so that the situation that the safety work operation range of the magnetic suspension centrifugal air compressor is limited due to the excessive protection phenomenon is prevented.

Description

Technical Field

[0001] The present invention relates to the technical field of air compression, and particularly to a method for adjusting the surge control line of a magnetic levitation centrifugal compressor. Background Art

[0002] A magnetic levitation centrifugal air compressor is a new type of centrifugal air compressor that is energy-saving, oil-free, and silent. The magnetic levitation centrifugal air compressor includes a motor and a rotor. Coils are sleeved on both ends of the rotor. After the coils are energized, the rotor is magnetically levitated therein under the action of electromagnetic force. High-efficiency centrifugal impellers are provided at both ends of the rotor, namely a first-stage impeller and a second-stage impeller. The rotor rotates at a high speed driven by the motor, thereby driving the first-stage impeller and the second-stage impeller to rotate at a high speed. External air is inhaled and compressed by the first-stage impeller, and the discharged high-temperature and high-pressure gas enters the second-stage impeller for further compression after being cooled by a heat exchanger, and is discharged from the air outlet after reaching the process gas pressure.

[0003] When the load of the magnetic levitation centrifugal air compressor decreases and the exhaust volume is less than a certain value, the normal transportation of gas is damaged. The discharged volume of gas is sometimes more and sometimes less, coming in and going out suddenly, generating strong oscillations, and emitting a noise like the gasping of an asthma patient. At this time, it can be seen that the indications of the gas outlet pressure gauge and the flow meter fluctuate greatly. Subsequently, the fuselage will also vibrate violently, and the compressor will produce periodic and intermittent roaring sounds. If no measures are taken in time, the compressor will be severely damaged. This phenomenon is called the surge of the centrifugal compressor, also known as surging.

[0004] The surge control line is drawn with the pressure-related value as the ordinate and the flow-related value as the abscissa at different speeds, obtaining a series of curves. The critical operating points of these curves are the surge control lines. There are various methods to obtain the surge control line. For example, one is to directly measure it through experimental methods; another is to change the speed of the centrifugal compressor, calculate the pressure-related value and the flow-related value at each speed, and then perform polynomial fitting to obtain the final surge control line. For example: taking the ratio of the absolute pressure P2 at the air outlet to the absolute pressure P1 at the air inlet as the ordinate and the volume flow of the gas at the air inlet as the abscissa to draw curves at different speeds. There is a highest point of P2 / P1 at each speed, and this point is called the hump. Connecting these hump points can obtain a surge control line. The part on the left side of the surge control line is the unstable surge area, and the part on the right side of the surge control line is the safe operating area.

[0005] In the industry, the theoretical surge control line is widely used as the wiring for the safe operation area. However, since the theoretical surge control line is based on a certain design condition, in actual use, the intake conditions vary greatly. For example, the altitude, intake temperature, etc. will significantly affect the intake air volume. Therefore, the theoretical surge control line often cannot truly and accurately reflect the safe operation area of the unit, and overprotection often occurs, restricting the range of the safe operation area of the unit. Summary of the Invention

[0006] To overcome the above problems in the prior art, the present invention provides a method for dynamically adjusting the surge control line of a magnetic levitation centrifugal air compressor, which can optimize the range of the safe operation area of the unit.

[0007] To achieve the above object, the technical solution of the present invention is as follows: A method for dynamically adjusting the surge control line of a magnetic levitation centrifugal air compressor includes the following steps: When the magnetic levitation centrifugal air compressor is started for the first time, it operates at the rated power, and records the motor speed n0 at the rated power, the current I0 at the rated power, the vibration value U0 of the rotor at the rated power, the initial intake pressure value P in , the initial intake temperature value T in ; then measure and set the surge control line f(a0). During actual use, record the current intake pressure value P again in ’ and the current intake temperature value T in , , if |P in -P in ’ |≥3 kPa or |T in -T in , |≥5 °C, then it is necessary to reset the stable working area of the magnetic levitation centrifugal air compressor and determine the lower limit and upper limit of the operation of the magnetic levitation centrifugal air compressor. The method for determining the lower limit of the operation of the magnetic levitation centrifugal air compressor is as follows: According to the current intake pressure value P in ’ of the surge control line under different theoretical working conditions, perform interpolation operation to obtain the surge offset f(a i ), so as to obtain a new surge control line f(a0)+f(a i ). The magnetic levitation centrifugal air compressor operates in the area near the right side of the new surge control line, and records the current vibration value U of the rotor i ; if U i <U0×110%, then confirm the new surge control line; if U i>U0×110%, then shift the new surge control line 2% to the right and check again whether U i <U0×110% until it meets U i <U0×110%; The method for determining the upper operating limit of the magnetic levitation centrifugal air compressor is as follows: Record the current operating current I i and the current motor speed n i , if |I i -I0| / I0 < 0.05, it indicates that I i does not differ much from I0, then maintain the operation at I i ; if |I i -I0| / I0 ≥ 0.05, it indicates that I i differs greatly from I0 and I i needs to be adjusted. At this time, if I i >I0, then adjust the current motor speed n i at a rate of 100 revolutions per minute. If I i <I0, then adjust the current motor speed n i at a rate of 100 revolutions per minute. After reducing or increasing n i , delay for 200 - 300 seconds and check again whether |I i -I0| / I0 < 0.05 until it meets |I i -I0| / I0 < 0.05.

[0008] Furthermore, after resetting the stable operating area of the magnetic levitation centrifugal air compressor, then determine whether to supplement air to the air inlet according to the current intake air temperature value T in , . When supplementing air, the air supplement source is the gas discharged from the air-cooled cooling of the magnetic levitation centrifugal air compressor, which passes through the air supplement regulating valve and then leads to the air inlet of the magnetic levitation centrifugal air compressor.

[0009] Furthermore, when the current intake air temperature value T in , ≥ 40°C, the air supplement regulating valve is fully open, and all the gas discharged from the air-cooled cooling of the magnetic levitation centrifugal air compressor leads to the air inlet of the magnetic levitation centrifugal air compressor; When the current intake air temperature value T in , ≤ 20°C, the air supplement regulating valve is closed and the air supplement stops; When 20°C < T in ,When the temperature is below 40°C, first close the air replenishing control valve and record the specific power SER0 at this time; then open the air replenishing control valve by 30% and delay for 200 - 300 seconds, and record the specific power SER1 at this time; if SER1 > SER0, close the air replenishing control valve, if SER1 < SER0, then increase the opening of the air replenishing control valve by another 5% and delay for 200 - 300 seconds, and record the specific power SER i+1 , and determine whether SER1 - SER i+1 / SER1 ≤ 0.01, if SER1 - SER i+1 / SER1 ≤ 0.01, then as long as the intake pressure at this time is less than the alarm value, the opening degree of the air replenishing control valve can be maintained. If SER1 - SER i+1 / SER1 > 0.01, then repeat increasing the opening of the air replenishing control valve by another 5% until SER1 - SER i+1 / SER1 ≤ 0.01.

[0010] Compared with the prior art, the beneficial effect of the present invention is that the present invention can optimize and adjust the surge control line according to the intake conditions under different intake conditions. Detailed implementation mode

[0011] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0012] A method for dynamically adjusting the surge control line of a magnetic levitation centrifugal air compressor includes the following steps: When starting up for the first time, the magnetic levitation centrifugal air compressor operates at the rated power, and record the motor speed n0 at the rated power, the current I0 at the rated power, the vibration value U0 of the rotor at the rated power, the initial intake pressure value P in , the initial intake temperature value T in ; then actually measure and set the surge control line f(a0). This step is usually completed by the manufacturer before leaving the factory.

[0013] The determination of f(a0) is the theoretical surge control line, which is a means well-known to those skilled in the art. For example, taking the ratio of the absolute pressure P2 at the outlet to the absolute pressure P1 at the inlet as the ordinate and the volumetric flow rate of the gas at the inlet as the abscissa, curves at different rotational speeds are plotted. At each rotational speed, there is a highest point of P2 / P1, which is called the hump. Connecting these hump points can obtain a surge control line. Or, when the unit is operating under a certain characteristic (such as a certain opening degree of the inlet valve), by adjusting the pipeline characteristic (such as closing the outlet valve of the machine), the operating point of the unit is gradually approached to the surge point. Once the unit surges, immediately open the outlet vent valve of the machine, and record the flow rate and pressure of the unit during surge. Repeat the same steps, change the unit and pipeline characteristics, obtain the performance parameters of the unit during different surges, mark the parameters of these surge points on the performance curve diagram, and connect them to obtain the surge control line of the unit.

[0014] During actual use, the actual inlet pressure varies greatly due to different usage environments and seasons. For example, when the inlet temperature is high, the gas density decreases, resulting in a decrease in the inlet air volume; when the inlet temperature is low, the gas density increases, and the inlet air volume will increase. Another example is that when the altitude increases, the gas density decreases, resulting in a decrease in the inlet air volume; when the altitude decreases, the density increases, and the inlet air volume will increase. Therefore, the surge control line set at the factory is very likely to be unable to truly and accurately reflect the safe operating area of the unit due to the differences in conditions between the usage site and the factory setting site, resulting in overprotection and restricting the range of the safe operating area of the unit.

[0015] The influence of altitude on the inlet air volume can basically be reflected by the recorded inlet pressure value. The factor that has a greater impact on the inlet air volume is still the inlet temperature, and the influence of the inlet temperature on the inlet air volume is difficult to be reflected only by recording the inlet pressure value.

[0016] Therefore, during actual use, record the current inlet pressure value P in ’ and the current inlet temperature value T in , , if |P in - P in ’ | ≥ 3 kPa or |T in - T in , | ≥ 5 °C, it proves that the current inlet pressure value P in ’ and the initial inlet pressure value P inIf there are significant differences, it is necessary to reset the stable operating range of the magnetic levitation centrifugal air compressor, determine the lower and upper operating limits of the magnetic levitation centrifugal air compressor, and the unit can operate between the upper and lower operating limits. The method for determining the lower operating limit of the magnetic levitation centrifugal air compressor is as follows: According to the current intake pressure value P in ’ On the surge control lines under different theoretical operating conditions (i.e., the surge control lines obtained by theoretical calculation at different rotational speeds, and the theoretical calculation method is the method described in the background technology part, etc., which will not be elaborated here), perform interpolation operations to obtain the surge offset f(a i ), in order to obtain a new surge control line f(a0)+f(a i ). The magnetic levitation centrifugal air compressor operates in the area near the right side of the new surge control line. At this time, it is already close to the new surge control line (it is not difficult for those skilled in the art to determine the degree of closeness, as long as it is close to the area near the right side of the new surge control line to check whether the setting of the area near the right side of the new surge control line is reasonable), and record the current vibration value U of the rotor i ; if U i < U0×110%, that is, the current vibration value U i is only 10% larger than U0, which is controlled within an acceptable and reasonable range, then confirm this new surge control line; if U i > U0×110%, then shift the new surge control line 2% to the right, and check again whether U i < U0×110% at this time, until it meets U i < U0×110%.

[0017] The method for determining the upper operating limit of the magnetic levitation centrifugal air compressor is as follows: Record the current operating current I i and the current motor speed n i . If |I i - I0| / I0 < 0.05, then maintain the operation at I i ; if |I i - I0| / I0 ≥ 0.05, at this time if I i > I0, then adjust the current motor speed n i to decrease at a rate of 100 revolutions per minute. If I i < I0, then adjust the current motor speed n i to increase at a rate of 100 revolutions per minute. After decreasing or increasing n i , delay for 200 - 300 seconds and check again whether |I i - I0| / I0 < 0.05, until it meets |I i - I0| / I0 < 0.05.

[0018] By determining the upper and lower operating limits of the magnetic levitation centrifugal air compressor through the above method, the changes in the intake air volume under different factors are fully considered, especially the change in the intake air volume due to temperature. The safe operating area of the magnetic levitation centrifugal air compressor is reset to adapt to the new usage environment, and the magnetic levitation centrifugal air compressor can operate safely between the upper and lower operating limits.

[0019] In the prior art, the air-cooling method is usually also adopted to cool the unit. Generally, the gas discharged by air-cooling is emptied into the external environment. After resetting the stable working area of the magnetic levitation centrifugal air compressor in the present invention, the gas discharged by air-cooling can be used for air replenishment, so that the gas discharged by air-cooling can be effectively utilized to achieve the purpose of energy conservation.

[0020] The specific method of the air replenishment operation is as follows: After resetting the stable working area of the magnetic levitation centrifugal air compressor, according to the current intake air temperature value T in , Judge whether to replenish air to the air inlet. When replenishing air, the air replenishment source is the gas discharged by air-cooling the magnetic levitation centrifugal air compressor, which passes through the air replenishment regulating valve and then leads to the air inlet of the magnetic levitation centrifugal air compressor.

[0021] The current intake air temperature value T in , When the current intake air temperature value T ≥ 40°C, since the intake air temperature is relatively high, the density of the air is relatively low at this time, so the intake air volume is insufficient. The air replenishment regulating valve is fully opened, and all the gas discharged by air-cooling the magnetic levitation centrifugal air compressor leads to the air inlet of the magnetic levitation centrifugal air compressor; The current intake air temperature value T in , When the current intake air temperature value T ≤ 20°C, since the intake air temperature is relatively low, the density of the air is relatively high at this time, so the intake air volume is sufficient. The air replenishment regulating valve is closed to stop air replenishment; When 20°C < T in , < 40°C, first close the air replenishment regulating valve, and record the specific power SER0 at this time (the specific power refers to the ratio of the power of the air compressor unit to its volumetric flow rate under specific working conditions, with the unit of KW / m³ / min. It reflects the power required for the unit to generate an equal gas volume under the rated pressure. The smaller the specific power, the more energy-efficient the unit is); then open the air replenishment regulating valve by 30% and delay for 200 - 300 seconds, and record the specific power SER1 at this time; if SER1 > SER0, it means that the energy-saving performance of the unit decreases after opening the air replenishment valve, so close the air replenishment regulating valve. If SER1 < SER0, it means that the energy-saving performance of the unit increases after opening the air replenishment valve, then increase the opening of the air replenishment regulating valve by 5% and delay for 200 - 300 seconds, and record the specific power SER i+1, and determine whether SER1 - SER i+1 / SER1 ≤ 0.01. If SER1 - SER i+1 / SER1 ≤ 0.01, then as long as the intake pressure at this time is less than the alarm value, the opening degree of the air make-up regulating valve can be maintained. If SER1 - SER i+1 / SER1 > 0.01, then repeat to increase the opening of the air make-up regulating valve by another 5% until SER1 - SER i+1 / SER1 ≤ 0.01.

[0022] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details.

Claims

1. A method for dynamically adjusting the surge control line of a magnetically suspended centrifugal air compressor, characterized in that The following steps are involved: When the magnetic suspension centrifugal air compressor is started for the first time, it runs at rated power, and records the motor speed n0 at rated power, the current I0 at rated power, the vibration value U0 of the rotor at rated power, and the initial intake pressure value P in , initial intake air temperature value T in ; Then the surge control line f(a0) is set by actual measurement; In actual use, record the current intake pressure value P again in ’ And the current intake air temperature value T in , , if |P in -P in ’ |≥3kPa or |T in -T in , |≥5℃, it is necessary to reset the stable working area of ​​the magnetic levitation centrifugal air compressor and determine the lower and upper operating limits of the magnetic levitation centrifugal air compressor; The method for determining the lower operating limit of a magnetically suspended centrifugal air compressor is: According to the current intake pressure value P in ’ The surge control line under different theoretical conditions is interpolated to obtain the surge offset f(a i ) to obtain the new surge control line f(a0)+f(a i ), the magnetic suspension centrifugal air compressor runs to the area near the right side of the new surge control line, and the current vibration value U of the rotor is recorded. i ;if U i <U0×110%, confirm the new surge control line; if U i >U0×110%, move the new surge control line to the right by 2%, and check again whether U i <U0×110%, until it meets U i <U0×110%; The method for determining the operating upper limit of the magnetic suspension centrifugal air compressor is as follows: record the current operating current I i and the current motor speed n i , if |I i -I0| / I0<0.05, then keep I i Run; if |I i -I0| / I0≥0.05, then if I i >I0, adjust the current motor speed n i At a rate of 100 rpm, if I i <I0, adjust the current motor speed n i Increase at a rate of 100 rpm, while decreasing or increasing n i After a delay of 200-300 seconds, check again whether i -I0| / I0<0.05, until it meets |I i -I0| / I0<0.

05.

2. The method for dynamically adjusting the surge control line of a magnetically suspended centrifugal air compressor according to claim 1, characterized in that: After resetting the stable working area of ​​the magnetic levitation centrifugal air compressor, according to the current intake air temperature value T in , It is determined whether to supplement air to the air inlet. When supplementing air, the air source is the gas discharged from the magnetic levitation centrifugal air compressor after air cooling, and the gas passes through the air supplement regulating valve and then leads to the air inlet of the magnetic levitation centrifugal air compressor.

3. The method for dynamically adjusting the surge control line of a magnetically suspended centrifugal air compressor according to claim 1, characterized in that: Current air temperature value T in , When the temperature is ≥40℃, the air supply regulating valve is fully opened, and the magnetic levitation centrifugal air compressor is cooled by air, and all the discharged gas is led to the air inlet of the magnetic levitation centrifugal air compressor; Current air temperature value T in , When the temperature is ≤20℃, the air supply regulating valve is closed and the air supply is stopped; 20℃<T in , When the temperature is less than 40℃, first close the air supply regulating valve and record the specific power SER0 at this time; then open the air supply regulating valve by 30% and delay for 200-300 seconds, and record the specific power SER1 at this time; if SER1>SER0, close the air supply regulating valve; if SER1<SER0, open the air supply regulating valve by another 5% and delay for 200-300 seconds, and record the specific power SER i+1 , and determine whether SER1-SER i+1 / SER1≤0.01, if SER1-SER i+1 / SER1≤0.01, as long as the intake pressure is less than the alarm value, the opening degree of the air supply regulating valve can be maintained. i+1 / SER1>0.01, then repeatedly open the air supply regulating valve by 5% until SER1-SER i+1 / SER1≤0.01.