A dynamic adjustment method for the surge control line of a magnetically suspended centrifugal air compressor

Abstract

A method for dynamically adjusting the surge control line of a magnetic levitation centrifugal air compressor comprises the following steps: when the magnetic levitation centrifugal air compressor is first started, the compressor is operated at rated power, and 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 are recorded. in , initial intake air temperature value T in ; Then set the surge control line according to the actual measurement; in actual use, according to the current intake pressure value P in ’ And the current intake air temperature value T in , The surge control line is adjusted to prevent over-protection from limiting the safe operating range of the magnetic levitation centrifugal air compressor.

Description

Technical Field

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

[0002] The magnetic levitation centrifugal air compressor is a new type of centrifugal air compressor that is energy-efficient, oil-free, and silent. It consists of a motor and a rotor, each end of which is coated with coils. When the coils are energized, the rotor is magnetically suspended within them by electromagnetic force. High-efficiency centrifugal impellers, a primary and secondary impellers, are located at either end of the rotor. Driven by the motor, the rotor rotates at high speed, driving the primary and secondary impellers to rotate at high speed. The primary impeller draws in and compresses ambient air. The discharged, high-temperature, high-pressure gas is cooled in a heat exchanger and then compressed again by the secondary impeller. It is discharged through the outlet after reaching the process air pressure.

[0003] When the load of a magnetic levitation centrifugal air compressor decreases and the exhaust volume falls below a certain value, the normal delivery of gas is disrupted. The amount of gas discharged fluctuates, and the gas flows in and out at random, producing strong vibrations and a noise similar to that of an asthma patient. At this time, the indications of the gas outlet pressure gauge and flow meter fluctuate greatly. Subsequently, the fuselage will also vibrate violently, and the compressor will produce periodic and intermittent roaring sounds. If timely measures are not taken, the compressor will be seriously damaged. This phenomenon is called surge of the centrifugal compressor, also known as flying.

[0004] The surge control line is drawn with pressure-related values as the ordinate and flow-related values as the abscissa. This is done at different speeds to obtain a series of curves, and the critical operating points of these curves are the surge control lines. There are several ways to obtain the surge control line. For example, one method is to directly measure it through experimental methods. Another method is to change the speed of the centrifugal compressor, calculate the pressure-related values and flow-related values at each speed, and then perform polynomial fitting to obtain the final surge control line. For example, the ratio of the outlet absolute pressure P2 to the inlet absolute pressure P1 is used as the ordinate, and the volume flow rate of the inlet gas is used as the abscissa to draw curves at different speeds. At each speed, there is a peak point of P2 / P1, which is called a hump. Connecting the hump points will yield a surge control line. The portion to the left of the surge control line is the unstable surge zone, and the portion to the right of the surge control line is the safe operating zone.

[0005] The theoretical surge control line is widely used in the industry as the connection line for the safe operating area. However, since the theoretical surge control line is often based on a certain design operating condition, in actual use, the intake conditions vary greatly. For example, altitude, intake temperature, etc. will significantly affect the intake volume. Therefore, the theoretical surge control line often cannot truly and accurately reflect the safe operating area of the unit, and over-protection often occurs, which limits the range of the unit's safe operating area. Summary of the Invention

[0006] In order 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 safe operating 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 magnetically suspended centrifugal air compressor comprises the following steps:

[0008] When the magnetic levitation centrifugal air compressor is turned on for the first time, it is operated at rated power. 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 are recorded. in , initial intake air temperature value T in ; Then the surge control line f(a0) is set by actual measurement;

[0009] 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;

[0010] The method for determining the lower operating limit of a magnetic levitation centrifugal air compressor is:

[0011] According to the current intake pressure value P in ’ The surge control lines under different theoretical working conditions are interpolated to obtain the surge offset f(a i ) to obtain the new surge control line f(a0)+f(a i ), the magnetic levitation 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%;

[0012] The method for determining the upper limit of the operation of the magnetic levitation centrifugal air compressor is: record the current operating current I i and the current motor speed n i , if |I i -I0| / I0<0.05 indicates I i If the difference with I0 is not big, then keep I i Run; if |I i -I0| / I0≥0.05, indicating that I i There is a big difference with I0, so I i Make adjustments. 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, and then decrease or increase n i After a delay of 200-300 seconds, check again to see if it is i -I0| / I0<0.05, until it meets |I i -I0| / I0<0.05.

[0013] Furthermore, after resetting the stable working area of the magnetic levitation centrifugal air compressor, the current intake air temperature value T in , Determine whether to replenish air to the air inlet. When replenishing air, the air source is the gas discharged from the magnetic levitation centrifugal air compressor after air cooling, which passes through the air replenishment regulating valve and then leads to the air inlet of the magnetic levitation centrifugal air compressor.

[0014] Furthermore, the current intake 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;

[0015] Current air temperature value T in , When the temperature is ≤20℃, the air supply regulating valve is closed and the air supply is stopped;

[0016] 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.

[0017] Compared with the prior art, the present invention has the beneficial effect of being able to optimize and adjust the surge control line according to the intake conditions under different intake conditions. DETAILED DESCRIPTION

[0018] The technical solution of the present invention is described clearly and completely below in conjunction with the embodiments of the present invention.

[0019] A method for dynamically adjusting a surge control line of a magnetically suspended centrifugal air compressor comprises the following steps:

[0020] When the magnetic levitation centrifugal air compressor is turned on for the first time, it operates 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. This step is usually completed by the manufacturer before shipment.

[0021] Determining f(a0) is the theoretical surge control line, a technique well-known to those skilled in the art. For example, a curve plotted at different speeds is plotted with the ratio of the outlet absolute pressure P2 to the inlet absolute pressure P1 as the ordinate and the inlet gas volume flow rate as the abscissa. Each speed has a peak P2 / P1 ratio, called a hump. Connecting the hump points yields a surge control line. Alternatively, when the unit is operating under certain characteristics (e.g., a constant inlet valve opening), the unit's operating point can be gradually brought closer to the surge point by adjusting the pipeline characteristics (e.g., closing the outlet valve). Once the unit surges, the outlet vent valve is immediately opened, and the unit's flow rate and pressure during surge are recorded. Repeating the same steps, varying the unit and pipeline characteristics, yields different performance parameters for the unit during surge. These parameters at these surge points are plotted on the performance curve and connected to yield the unit's surge control line.

[0022] In actual use, the actual intake pressure varies greatly due to different operating environments and seasons. For example, when the intake temperature is high, the gas density decreases, resulting in a decrease in intake volume; when the intake temperature is low, the gas density increases, and the intake volume increases. For another example, when the altitude increases, the gas density decreases, resulting in a decrease in intake volume; when the altitude decreases, the density increases, and the intake volume increases. Therefore, the surge control line set at the factory is very likely to not truly and accurately reflect the safe operating area of the unit due to differences in conditions between the usage site and the factory setting site, resulting in over-protection and limiting the range of the unit's safe operating area.

[0023] The effect of altitude on the intake volume can basically be reflected by recording the intake pressure value. The intake temperature has a greater impact on the intake volume, and the effect of intake temperature on the intake volume is difficult to reflect simply by recording the intake pressure value.

[0024] Therefore, in actual use, record the current intake pressure value P in ’ And the current intake air temperature value T in , , if |P in -P in ’ |≥3kPa or |T in -T in , |≥5℃, it proves that the current intake pressure value P in ’ and the initial intake pressure value P inIf there is a large difference, 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 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:

[0025] According to the current intake pressure value P in ’ The surge control lines under different theoretical working conditions (i.e., the surge control lines obtained by theoretical calculation at different speeds, the theoretical calculation method is as described in the background technology section, etc., which will not be repeated here) are interpolated to obtain the surge offset f(a i ) to obtain the new surge control line f(a0)+f(a i ), the magnetic levitation centrifugal air compressor runs to the area near the right side of the new surge control line. At this time, it is 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, it can be tested whether the setting of the area near the right side of the new surge control line is reasonable). Record the current vibration value U of the rotor i ;if U i <U0×110%, that is, the current vibration value U i Only 10% greater than U0, and within an acceptable range, the new surge control line is confirmed; 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 Until <U0×110%.

[0026] The method for determining the upper limit of the operation of the magnetic levitation centrifugal air compressor is: 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, and then decrease or increase n i After a delay of 200-300 seconds, check again to see if it is i -I0| / I0<0.05, until it meets |I i -I0| / I0<0.05.

[0027] The above method is used to determine the upper and lower operating limits of the magnetic levitation centrifugal air compressor, which fully considers the changes in the intake volume under different factors, especially the changes in the temperature on the intake volume. The safe operating area of the magnetic levitation centrifugal air compressor is reset to adapt to the new use environment. The magnetic levitation centrifugal air compressor can operate safely between the upper and lower operating limits.

[0028] In the prior art, air cooling is usually used to cool the unit. Generally speaking, the exhaust gas from the air cooling is discharged into the external environment. In the present invention, after resetting the stable working area of the magnetic levitation centrifugal air compressor, the exhaust gas from the air cooling can be used to replenish air, so that the exhaust gas from the air cooling can be effectively utilized to achieve the purpose of energy saving.

[0029] The specific method of gas replenishment operation is:

[0030] After resetting the stable working area of the magnetic levitation centrifugal air compressor, according to the current intake air temperature value T in , Determine whether to replenish air to the air inlet. When replenishing air, the air source is the gas discharged from the magnetic levitation centrifugal air compressor after air cooling, which passes through the air replenishment regulating valve and then leads to the air inlet of the magnetic levitation centrifugal air compressor.

[0031] Current air temperature value T in , When the temperature is ≥40℃, the air intake temperature is high and the air density is low, so the air intake is insufficient. The air supply regulating valve is fully opened, and the magnetic levitation centrifugal air compressor is cooled by air. All the discharged gas is directed to the air intake of the magnetic levitation centrifugal air compressor.

[0032] Current air temperature value T in , When the temperature is ≤20℃, the air intake temperature is low and the air density is high, so the air intake is sufficient, the air supply regulating valve is closed, and air supply stops;

[0033] 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 (specific power refers to the ratio of the power of the air compressor unit to its volume flow under specific working conditions, with the unit of KW / m³ / min. It reflects the power required for the unit to produce an equal amount of gas at rated pressure. The smaller the specific power, the more energy-efficient the unit is); then open the air supply regulating valve by 30% and delay it 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 supply valve, so close the air supply regulating valve. If SER1<SER0, it means that the energy-saving performance of the unit increases after opening the air supply valve, then open the air supply regulating valve by another 5% and delay it for 200-300 seconds, and record the specific power SER at this time 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.

[0034] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and the embodiments. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, 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 levitation centrifugal air compressor is turned on for the first time, it is operated at rated power. 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 are recorded. 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 magnetic levitation centrifugal air compressor is: According to the current intake pressure value P in ’ The surge control lines under different theoretical working conditions are interpolated to obtain the surge offset f(a i ) to obtain the new surge control line f(a0)+f(a i ), the magnetic levitation 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 upper limit of the operation of the magnetic levitation centrifugal air compressor is: 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, and then decrease or increase n i After a delay of 200-300 seconds, check again to see if it is 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, wherein: After resetting the stable working area of the magnetic levitation centrifugal air compressor, according to the current intake air temperature value T in , Determine whether to replenish air to the air inlet. When replenishing air, the air source is the gas discharged from the magnetic levitation centrifugal air compressor after air cooling, which passes through the air replenishment 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, wherein: 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.