JPS63230998A - Control method for centrifugal compressor - Google Patents

Abstract

PURPOSE:To improve controllability of a flow rate and efficiency, by a method wherein, after a flow rate a flow rate attains an approximate target value based on a flow rate characteristic function and an efficiency characteristic function, a flow rate is regulated to an approximate target value as a flow rate and efficiency are actually measured by an external insertion method. CONSTITUTION:Inlet guide vanes 11-14 and diffuser vanes 15-18 are driven and controlled by means of signals from flow rate, temperature, pressure, and number of revolutions sensors 20, 21, 22, and 24. First, a flow rate is caused to attain an approximate target value based on a flow rate characteristic function and an efficiency characteristic function by a mounting method as high efficiency is maintained. Thereafter, a flow rate is regulated to an approximate target value as a flow rate and efficiency are actually measured by an external insertion method. This method enables control of a flow rate simultaneously with improvement of efficiency.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to centrifugal compressors such as raw air compressors, factory air source compressors, and gas compressors for chemical plants used in oxygen production plants and various plants. It relates to a method for controlling the capacity and pressure of.

[Prior Art] Generally, a centrifugal compressor having a multi-stage configuration is used in an oxygen production plant or various plants. In such a multistage centrifugal compressor, as shown in Fig. 8,
The centrifugal compressor 1 includes a first stage compressor 4, which is driven by a power transmission gear 3 that speeds up rotation from a drive machine 2. 2nd stage compressor 5° 3rd stage compressor 6 and 4th stage compressor 7
In addition, an intercooler 8 is provided between the compressors 4 and 5, an intercooler 9 is provided between the compressors 5 and 6, and an intercooler 9 is provided between the compressors 6 and 7.
An intercooler 10 is provided in between.

Note that the compressors 4 and 5 and the compressors 6 and 7 are respectively overhanged on the same shaft end.

In such a centrifugal compressor 1, the air sucked into the first stage compressor 4 is sequentially compressed and cooled by each compressor 5 to 7 and intercooler 8 to 10, and is then compressed and cooled by the fourth stage compressor 4. From the compressor 7 it is sent to the process.

Variable angle inlet guide vanes (GV) 11 to 14 are provided on the inlet side of the compressors 4 to 7 in each stage, and by adjusting the angles of these inlet guide vanes 11 to 14, each The air capacity flowing into the compressors 4 to 7 can be adjusted.

Furthermore, diffuser vanes (DV) 15 to 18 are provided on the outlet side of the compressors 4 to 7 in each stage, and by adjusting the angles of these diffuser vanes 15 to 18, the The air capacity flowing out from 7 can be adjusted.

The angles of these inlet guide vanes 11 to 14 and diffuser vanes 15 to 18 are each adjusted to arbitrary values by a drive device 19.

Furthermore, this centrifugal compressor 1 as a whole or each stage compressor 4
Operating state quantities 1 to 7, for example, air flow rate, temperature, pressure, etc., are determined by the flow rate sensor 20. Temperature sensor 2
1. It is detected by a detection means such as the pressure sensor 22. A control device 23 is provided between each of the sensors 20 to 22 and the drive device 19.

Conventionally, in order to control the multistage centrifugal compressor described above so that a predetermined air volume (flow rate) can always be obtained with optimum operating efficiency according to various operating conditions, there has been a conventional method using a control table and the current pressure feeding method. A method using the differential pressure between po and set pressure Pc has been proposed.

In the former control means, the inlet guide vane of each stage is used as a manipulated variable to realize the optimum operating state for various operating states based on the characteristics of the entire centrifugal compressor 1 or the compressors 4 to 7 of each stage. The optimal combination values of the angles of the vanes 11 to 14 and the diffuser vanes 15 to 18 are programmed and stored in advance in the storage section in the control device 23 as a control table. Then, the control device 23 controls the sensors 20 to
22, an appropriate inlet guide vane 11-1 is used to change the flow rate to a predetermined value based on the detected value.
4 and the diffuser vanes 15 to 18 are uniquely determined from the control table, and based on the combination value, the inlet guide vanes 11 to 14 and the diffuser vanes 15 to 18 are driven to control the flow rate. .

In addition, in the latter control means, based on the compressor characteristics in advance,
The increase/decrease relationship between the differential pressure between the current sending pressure PD and the set pressure pc and the operation amount of the inlet guide vanes 11 to 14 and the diffuser vanes 15 to 18 is given. Inlet guide vane 1 of each stage as a manipulated variable to achieve the optimum operating state for the situation
The optimal combination values of the angles of the vanes 1 to 14 and the angles of the diffuser vanes 15 to 18 are also stored in advance in the control device 2 as a control table.
It is stored in the storage section of 3. When the differential pressure is large, control is performed using the control table similar to that described above, while when the differential pressure is small, the inlet guide is set such that the sending pressure P, ) becomes the set pressure pc based on the increase/decrease relationship. Vanes 11-14 and diffuser vanes 15-1
8 to control the flow rate.

In any of the above-mentioned control means, after the flow rate reaches the target flow rate, the angles of the inlet guide vanes 11 to 14 and the diffuser vanes 15 to 18 at that time are set as initial values, and the efficiency is optimized. Fine-tune by trial and error so that

This series of control operations is performed in order to quickly adjust the pressure in accordance with changes in the operating state of the compressor, and is repeated at the necessary intervals to maintain high efficiency.

[Problems to be Solved by the Invention] However, in any case, in the conventional centrifugal compressor control means as described above, the inlet guide vanes 11 to 14
The combination of the angle of the angle of There is a problem in that a huge amount of data is required to preset the necessary and particularly optimal combinations.

In addition, the former control means requires a large control table for a wide range of flow rates and minute changes in flow rate, especially when setting a flow rate that is not given in the control table as a target value.
The inlet guide vane angle α and the diffuser vane angle β must be determined by interpolation from the data in the control table, but at this time, as shown in FIG. 9, the interpolation values do not give the optimum values.

Furthermore, in the latter control means, there is no guarantee of efficiency if the differential pressure control means is used alone, so it is necessary to combine the control means with a control table.

The present invention aims to solve these problems, and is effective, versatile, and effective for any target flow rate without requiring the above-mentioned test run period or huge amount of data. The object of the present invention is to provide a centrifugal compressor control method that quantitatively guarantees efficiency during control.

[Means for Solving the Problems] Therefore, the method for controlling a centrifugal compressor of the present invention provides (a) a control method for controlling the inlet guide vane and the diffuser vane on a vane angle plane determined by the angles of the inlet guide vane and the diffuser vane; After setting in advance a flow rate characteristic function and an efficiency characteristic function that are a function of the angle of Regarding these current angles, the vector in the normal direction of the constant flow rate curve determined by the above flow rate characteristic function, which is directed toward the target flow rate, is determined as the first vane angle manipulated variable vector, and the vector in the tangential direction of the constant flow rate curve is determined as the first vane angle manipulated variable vector. After determining the direction in which the efficiency increases as determined by the above efficiency characteristic function as the second vane angle operation amount vector, these first vane angle operation amount vector and second vane angle operation amount vector are is added to obtain the third vane angle operation amount vector,
The flow rate of the centrifugal compressor is controlled based on the angles of the inlet guide vane and the diffuser vane determined by this third vane angle operation amount vector, and the difference between the flow rate of the centrifugal compressor and the target flow rate is set to a predetermined value. (b) Measure the actual flow rate and effective efficiency at at least three points by operating the above-mentioned inlet guide vanes and diffuser vanes, and then adjust the above-mentioned inlet guide vanes so as to surround these measurement points. Develop multiple extrapolation points for the angle of the diffuser vane and the angle of the diffuser vane, predict the flow rate and efficiency for each of these extrapolation points from the above actual measurement points, and then select the one that is close to the target flow rate and has high efficiency from among these extrapolation points. The flow rate of the centrifugal compressor is controlled based on the angles of the inlet guide vane and the diffuser vane determined by the selected extrapolation point.

[Embodiments of the Invention] Hereinafter, a method for controlling a centrifugal compressor as an embodiment of the present invention will be explained with reference to the drawings. FIG. 1 is a flowchart thereof. First, before explaining the method according to the present embodiment, The configuration of a centrifugal compressor to which the method of this embodiment is applied will be explained with reference to FIG. Note that in FIG. 7, the same reference numerals as those in FIG. 8 indicate substantially similar parts, and therefore the explanation thereof will be omitted. However, in the multistage centrifugal compressor to which the control device of the present embodiment shown in FIG. 7 is applied, the compressors 4 to 7 are all overhanged on the same shaft end, and the power transmission gear 3 is omitted, as shown in FIG. It is different from the multi-stage centrifugal compressor in

As shown in FIG. 7, in the multistage centrifugal compressor of this embodiment, inlet guide vanes (GV) 11 to 14 are driven by inlet guide vane drive devices 19a to 19d, respectively, and diffuser vane (DV) 15 ~1
8 are diffuser vane drive devices 19e to 19, respectively.
It is designed to be driven by h. Further, as a sensor, a flow rate sensor 20. Temperature sensor 2/1. In addition to the pressure sensor 22, a rotation speed sensor 24 for detecting the compressor rotation speed and a humidity sensor 27 are provided.

The detection signals from the sensors 20 to 22, 24, and 27 are all input to a control device 28, which controls the inlet guide vane in order to control the flow rate in the centrifugal compressor 1. In order to adjust the angles of the diffuser vanes 11 to 14 and the diffuser vanes 15 to 18, appropriate control signals can be calculated and output to the respective drive devices 19a to 19h upon receiving each detection signal.

Next, the case where the control method of this embodiment is applied to the centrifugal compressor as described above will be explained using FIGS. 1 to 6.

First, before starting the control, the storage section of the control device 28 stores information on the vane angle plane (αβ plane) determined by the angles (α, β) of the inlet guide vanes 11 to 14 and the diffuser vanes 15 to 18. The flow characteristic function f□=Q(α,β
) and efficiency characteristic function f2=η (α, β) are each mathematically modeled and set in advance, and the surging line SL (second (see figure) also g=G(α,β)=
It is mathematically modeled and set in advance as O.

Note that the flow rate characteristic function f2 and the efficiency characteristic function f2 are shown by the dotted line and solid line in Fig. 2, respectively, and these can be easily determined by selecting appropriate samples and approximating them based on short-term actual machine operation data. .

In the control method in this embodiment, as shown in FIG. 1, a control method called a hill-climbing method is carried out in steps A4 to All, and then a control method called an extrapolation method is carried out in steps 81 to B12. It is characterized in that the flow rate of the centrifugal compressor 1 is controlled by a control device 28. Note that, as described later, steps A12 to A14 are for implementing a surging elimination method, and steps A15 to A17 are for implementing a surging avoidance method.

When controlling the flow rate of the centrifugal compressor 1, first.

After setting the target flow rate QFXN (step An), the inlet guide vanes 11 to 14 and the diffuser vane 1
Measure the current angles (α, β) of 5 to 18 (step A
2). Then, from the measured vane angles (α, β),
It is determined whether or not this current angle is within a preset surging region (Step A3). If it is within the surging region [when G(α,β) is O], the process moves to Step A12, which will be described later.

On the other hand, if it is not within the surging area, proceed to the next step A.
Move on to 4. At this time, the vane angle (α).

The current flow rate QNO%I at β) can be obtained (estimated) using a preset flow rate characteristic function f1.

If the current vane angle (α, β) is not within the surging region, first, the first vane angle operation amount vector (Δα1.Δβ□) toward the target flow rate QvN is determined as follows. In other words, the constant flow rate curve Q(
α, β) “About QNOW.

Normal direction of this equal flow rate curve Caf□/aα, af1/a
β), the vane angle (
If α, β) are driven, the shortest operation path can be obtained, so this normal direction vector directed toward the target flow rate QFIN is the first vane angle operation amount vector (Δα8.
Δβ, ). Here, the flow rate modified based on the vane angle manipulated vector (Δα1.Δβ,) is Δ
If Q, ΔQ = (a f , /clα)A (E1+ (a
It is expressed as f −/a β)A βt (1), and the vane angle operation amount Δα0. Since Δβ is proportional to the difference between the target flow rate QFIN and the current flow rate QNow,
Considering the above normal direction, the first vane angle operation amount vector (Δα1゜Δ
β□) can be obtained. Note that K means a tuning parameter.

In this way, after the first vane angle operation amount vector (Δα1.Δβ1) is determined in step A4,
It is determined whether the current vane angle (α, β) is near the surging line SL shown in FIG. 2 (step A
5). If it is near the surging line SL [when G (α, β) <ea; however, if eQ is a positive value close to O, the process moves to step A15, which will be described later; if it is not near the surging line SL, Next step A6
Move to.

In step 86, for the first vane angle operation amount vector (Δα4.Δβ1) determined to approach the target flow rate QF1N via the shortest path, the efficiency is increased without changing the flow rate. A second vane angle operation amount vector (Δα2.Δβ2) is determined. In other words, as in the case of flow rate control in step A4 described above, the current vane angle (α,
Regarding the iso-efficiency curve η (α, β) = ηNCIW in β), the normal direction of this iso-efficiency curve (af2/aα, δf
, /aβ) and the vane angle (α, β) is driven in a direction in which the improved efficiency Δη becomes positive, the efficiency η is improved. here.

The efficiency Δη improved based on the second vane angle operation amount vector (Δα2.Δβ2) is A 7+ = (afz/aα)A rx, +Caf, /
aβ)Δβ2...(3) It is expressed as follows. At this time, in order to prevent the flow rate from changing due to efficiency improvement operations, the vane angle operation amount Δα2
．． In order to make the flow rate change ΔQ due to Δβ2 zero, from equation (1), (a f Lea a )A az + (a f−
/aβ) Δβ2=0 (4) The vane angle operation amount Δα2. Determine Δβ2. That is, the improvement efficiency Δη>0 in the tangential direction vector of the constant flow rate curve is (3).

When calculated from equation (4), the second vane angle operation amount vector (Δα2゜Δ
β2) can be obtained. Note that K2 indicates a tuning parameter.

Then, the first vane angle operation amount vector (Δα1.Δ
β, ) and the second vane angle manipulated amount vector (Δα2
．． By adding Δβ2), the flow rate becomes the target flow rate QF
A third vane angle operation amount vector (Δα3.Δβ,) that can increase efficiency while approaching IN is determined and output as a vane angle operation amount vector (Δα, Δβ) (
Step A7). That is, calculations based on the following equation (6) are performed.

After this, each vane angle operation amount Δα is determined.

If Δβ exceeds the maximum allowable operating amount of the inlet guide vanes 11 to 14 and the diffuser vanes 15 to 18, in other words, the angle that can be driven at one time may be exceeded, the vane angle operating amount Δα or Δβ , the third
Substitute it into the limiter function FL(X) as shown in the figure, and reduce the vane angle operation amount Δα or Δβ if it exceeds the maximum allowable operation amount (step A8
). Furthermore, when the vane angle (α, β) is driven based on the vane angle operation amount vector (Δα, Δβ) obtained up to step A8, the new vane angle ( When it is determined that α+Δα, β+Δβ) falls within the surging region, the magnitude of the vane angle operation amount vector (Δα, Δβ) is reduced and output (step A9).

The vane angle operation amount vector (Δ
The drive bag [19a
Output a control signal to ~19h and inlet guide vane 11~
14 and diffuser vanes 15 to 18 are driven and controlled (step A10).

Then, it is determined whether or not the flow rate changed by one or more vane drive controls has reached the vicinity of the target flow rate QFN (Step A11). If it has not reached it, the process returns to Step A4 again and the vane is moved by the ascending method. While the angle control is continued, if it is determined that the flow rate has reached the vicinity of the target flow rate QFIN, the flow moves to the first step B1 using the next extrapolation method. Here, the determination method in step All is as follows.

(Based on the current vane angle (α, β) obtained by the vane drive control described above, the current flow rate Q sow is estimated from a preset flow rate characteristic function f, and this estimated value QN
If the difference between the two is within a certain value εδ, that is, lQNow QFINI≦ij, it is determined that the target flow rate QFN has been reached.

(ii) Vane angle operation amount Δα, Δβ is 1Δα1≦ε
1 and 1Δβ1≦E2 (when there is no further operation), it is determined that the target flow rate QFIN has been reached.

(nu) Vane angle operation amount Δα, Δβ is Δα + (Δ
β) 2≦ε.

When this happens, it is determined that the flow rate has reached the vicinity of the target flow rate QF1N.

As described above, the starting point of the vane angle (α
. , β, ), the vane angle control is performed so that the flow rate approaches the target flow rate QFIN and achieves high efficiency.

Next, the surging elimination method in steps A12 to A14 and the surging avoidance method in steps A15 to A17 will be explained. First, if it is determined in step A3 that the current vane angle (α., β.) is within the surging region [when G (α, β) < O],
As shown in FIG. 5(a), the shortest operating path to eliminate surging is naturally the surge line SL [g=G(
α, β) = 0] normal direction (δg/δα, δg/aβ)
Since this is the direction heading out of the surging area, this normal direction vector, which is heading out of the surging area, is the vane angle operation amount vector for surging cancellation (Δα,).

Δβ4). Here, the manipulated variable is the boundary line G(α
, β) = O and the current surging function value G(α.

β. ) is proportional to the difference between

...(7) As the vane angle operation amount vector for eliminating surging (
Δα, Δβ,) are obtained (step A12) and output as a vane angle operation amount vector (Δα, Δβ) (step A13).

Then, as in the case of step A8, the obtained vane angle operation amounts Δα and Δβ are
4 and diffuser vanes 15 to 18, the vane angle operation amount Δα or Δβ
After reducing the size, a control signal is output to the driving bags [119a to 19h to drive and control the entrance guide vanes 11 to 14 and the diffuser vanes 15 to 18 (step A1
4).

After this, the process returns to step A2 again, and in step A3 it is determined whether the vane angle is within the current surging area, and the above steps A12 to A14 are repeated until the vane angle (α, β) is outside the surging area. ,.

Also, in step A5, the current vane angle (α,
When β) is near the surging line SL, [G(α,
β)<ea; However, eQ is a positive value close to 0] If it is determined that As shown in Figure (b), it is determined whether or not the vehicle is heading into the surging region (step A15), and if it is not, steps A6 and A7 are performed without calculating the second vane angle operation amount vector. By skipping step A17 and outputting the first vane angle operation amount vector (Δα□, Δβ,) as the vane angle operation amount vector (Δα, Δβ) as it is, and moving to step A8, consider improving efficiency. It is possible to quickly avoid the vicinity of the surging line SL.

On the other hand, in step A15, if it is determined that the first vane angle operation amount vector (Δα8.Δβ,) is heading into the surging region as shown in FIG. By removing the component toward the surging region from the first vane angle operation amount vector (Δα1.Δβ1) in this way, the vane angle operation amount vector for surging avoidance along the surging line (Δα6.Δβ
,) in search of.

Avoid surging. Here, if the unit vector l in the normal direction of the surging line SL heading into the surging region is n(i...(8), then the first vane angle can be calculated using this equation (8). From the operation amount vector (Δα8.Δβ,), the surging avoidance vane angle operation amount vector (Δα6
．． Δβ, ) is calculated.

...(9) It is.

In this way, the first vane angle operation amount vector (Δ
α4. The surging avoidance vane angle operation amount vector (Δα1.) in the direction along the surging line SL from Δβ1.
Δβ, ) (Step A16), and output this vane angle manipulated amount vector (Δα6.Δβ,) as the vane angle manipulated amount vector (Δα, Δβ) (Step A17).
By moving to step 88, the flow rate of the centrifugal compressor 1 is controlled without considering efficiency improvement and while avoiding entering the surging region.

Incidentally, since the procedure from step A8 onwards is as described above, the explanation thereof will be omitted.

Next, while eliminating or avoiding surging as described above, it is determined that the target flow rate QPIN has been reached in the vicinity of the target flow rate QPIN according to the map of the flow rate characteristic function and efficiency characteristic function on the modeled vane angle plane using the hill climbing method. Steps 81 to B in FIG.
Moving on to the extrapolation method based on actual measurements according to 12, vane angle control is performed to more accurately reach the target flow rate QFN.

In this extrapolation method, first, on the vane angle plane (αβ plane), as shown in FIG. , C
(step B1), and.

Regarding the selected three points A, B, and C, the control device 28 and the driving bags @ 19 a to 19h actually operate the inlet guide vanes 1 to 14 and the dip user vanes 15 to 18.
is driven, and the flow rate Q and efficiency η at each point A, B, and C are
is actually measured (step B2).

Here, the flow rate Q is detected by the flow rate sensor 20, while the efficiency η is calculated by the control device 28 based on detection signals from the sensors 20-22.

By the way, as shown in FIG. 2, the flow rate Q generally has a relationship between the vane angle and the increase/decrease in the flow rate, such that the flow rate Q always increases as the vane angles α and β become larger. By setting and storing the settings in the storage section of step B2, the reliability of the flow rate value actually measured in step B2 can be verified in step B3. Perform by B4.

That is, for the first measurement points A to C shown in FIG. 6(a), the flow rate at point B is always larger than the flow rate at point A between measurement points A and B due to the above increase/decrease relationship. Since it is clear, each actual measurement point A in step B2
- Compare actual measurement points A and B of the actual measured flow rate of C with the pre-stored flow rate increase/decrease relationship (step B3), and if the increase/decrease relationship is reversed, the comparison result will cause a logical contradiction. In step B4), it is determined that the measurement error by the flow rate sensor 20 is large, the data acquisition based on this actual measured flow rate is canceled, and the process returns to step B2 to obtain the actual measured flow rate again. At this time,
The number of times a logical contradiction has occurred is checked in step B5, and if the number of times is less than the set value N, the process returns to step B2 as described above, while if the number of times is greater than the set value N, an actual measurement point is set. Return to step B1 to correct the problem.

Further, if it is determined that the above comparison result does not cause a logical contradiction (step B4), the next step B6
Move to. In this way, by verifying the reliability of the actual measured flow rate, vane angle control can be performed without losing the direction of the target flow rate due to fluctuations in the measured flow rate or measurement errors during control execution. Become so.

In step B6, on the vane angle plane.

Expand and set a plurality of first extrapolation points (nine in this example) so as to surround the first actual measurement points A-C6. Then, at each extrapolation point The flow rate and efficiency are predicted from the actual flow rate and actual efficiency at measurement points A to C (step B7). In other words, the flow rate characteristic curve and the efficiency characteristic curve are estimated from the actual flow rate and effective efficiency at the three actual measurement points A to C by plane approximation or curved surface approximation, and then, based on the estimated characteristic curve, each outer The flow rate and efficiency at interpolation points ■ to ■ are predicted.

Then, from among these first extrapolation points (1) to (2), an extrapolation point where the predicted flow rate is close to the target flow rate QFIN and the predicted efficiency is high is selected (step B8).

Next, in step B9, it is determined whether or not the extrapolation point selected in step B8 falls within the surging region. In other words, if the selected extrapolation point is within the surging region [0( α.

β) In the case of <0>, select the one whose predicted flow rate is close to the target flow rate QF-IN and whose predicted efficiency is high from the extrapolation points other than the extrapolation point selected this time. (Step BIO) In step B9 again, it is checked whether the extrapolated point falls within the surging region. By repeating this, an extrapolation point that is close to the target flow rate QFIN and has high efficiency is selected from extrapolation points other than the extrapolation points within the surging region. In this way, it is possible to reliably prevent surging from occurring due to vane angle control.

When an extrapolation point that is close to the target flow rate and has high efficiency and is not in the surging region is selected [here, it is assumed that the extrapolation point in Fig. 6(a) has been selected], this extrapolation The vane angle (α) is the coordinate of point ■.

β) from the control device 28 to the drive device! l 9 a~
19h, and output the control signal to the inlet guide vane 11~
14 and diffuser vanes 15 to 18 are driven and controlled (step B11).

After this, the flow rate Q changed by one or more vane drive controls
and the target flow rate QFIN is smaller than the allowable flow rate ΔQv in vane angle control (step B).
12) If the flow rate difference is smaller than the flow rate allowable value ΔQv, vane angle control by extrapolation is terminated at that point, while if the flow rate difference is greater than or equal to the flow rate allowable value ΔQV,
Return to step B1 again, select three new actual measurement points, and
Steps 81 to B12 are performed in the same manner as described above for these second actual measurement points and second extrapolation points expanded to surround the second actual measurement points.

Here, the actual measurement points selected for the second time are shown in Fig. 6(a).
As shown in , one of the first actual measurement points, one of the extrapolation points selected in the first time, and the remaining extrapolation points among the first extrapolation points are selected. Regarding these actual measurement points, there are three points marked with ■.

Nine points are developed as extrapolation points: first extrapolation points ■, ■, ■, actual measurement points B and C, and new extrapolation points p1 to p4.

In this way, until the conditions in step B12 are met, actual measurement points are selected and extrapolation points are expanded to find an extrapolation point that is close to the target flow rate QFIN and has high efficiency, and vane angle control is performed by extrapolation. I will do it.

As described above, according to this embodiment, first, the flow rate of the centrifugal compressor 1 is determined by the hill climbing method (steps A4 to A11) while maintaining high efficiency on the map of the flow rate characteristic function and the efficiency characteristic function. After reaching the vicinity of , the flow rate can be actually measured using the extrapolation method (steps 81 to B12), and the flow rate can be reliably brought close to the target flow rate QFN while maintaining high efficiency. Therefore, flow rate control and efficiency improvement can be performed at the same time. This makes it possible to quantitatively guarantee efficiency during control, and to obtain a general-purpose centrifugal compressor control method that is effective for any target flow rate QFIN.

In addition, when implementing the control method of the above embodiment, the inlet guide vanes 11 to 14 and the diffuser vanes 15 to 18 of all stages may be controlled separately according to the above control method for each stage, or the control method of all stages may be separately controlled. The inlet guide vanes 11 to 14 and the diffuser vanes 15 to 18 may be driven and controlled at the same angle.
14 and the angles of the diffuser vanes 15 to 18 are set to a set of non-dimensional inlet guide vane angles and non-dimensional values such that the operating flow rate of the centrifugal compressors 4 to 7 in each stage has a similar operating flow rate in the same ratio to the design flow rate. The angles of the inlet guide vanes 11 to 14 and the diffuser vanes 15 to 18 of each stage may be expressed as a diffuser vane angle, and the vane angle may be controlled by regarding the angles of the inlet guide vanes 11 to 14 and the diffuser vanes 15 to 18 as one set.

In addition, in the hill climbing method of the above embodiment, in order to improve the approximation accuracy of the mathematical model, the characteristic function f1. f, the
It is conceivable to use means such as using a higher-order equation, dividing the region and expressing it with a plurality of functions, or modifying the parameters in the characteristic function based on actual measured values. In addition, in the hill climbing method of the above embodiment, the characteristic functions f, , f, are
Temperature and humidity as a function of the angles of the inlet guide vanes 11-14 and diffuser vanes 15-18.

It may also be formulated including terms such as rotation speed.

Furthermore, in the extrapolation method of the above embodiment, the expansion of the extrapolation points among the actual measurement points is limited to nine linear extrapolation points, as shown in FIG. 6(a). As shown in Figure 6 (b), 15 secondary extrapolation points are selected between the 9 primary extrapolation points, and the flow rate and efficiency are also predicted for these extrapolation points. However, although the number of actual measurement points is three in this embodiment, it is not limited to this, and may be four or more. Furthermore, the way in which the extrapolation points are developed is not limited to that shown in FIGS. 6(a) and 6(b), and the area around the extrapolation points may be changed arbitrarily.

Further, although the above embodiment shows a case where the method of the present invention is applied to a multi-stage centrifugal compressor, it can be similarly applied to a single-stage centrifugal compressor.

[,:,,1. :ei! fli, :J:jzi:r,
*f11. . After the flow rate of the centrifugal compressor reaches the target flow rate while maintaining high efficiency based on the flow rate characteristic function and the efficiency characteristic function i using the method, the flow rate and efficiency are measured by the extrapolation method to ensure that the target flow rate is reached. Since the flow rate can be approximated, flow rate control and efficiency improvement can be performed at the same time, and efficiency during control is quantitatively guaranteed, making it a versatile centrifugal compressor that is effective for any target flow rate. This has the effect of providing a control method.

[Brief explanation of the drawing]

Figures 1 to 7 show a centrifugal compressor as an embodiment of the present invention.
Fig. 1 is a flowchart of the control method; Fig. 2 is a graph showing a model example of a flow rate characteristic function, efficiency characteristic function, and certan line; Fig. 3 is a graph showing an example of a limiter function; FIG. 4 is a graph showing an example of vane angle control using the hill climbing method, FIG. 5(a) is a graph for explaining a method for eliminating surging, and FIG. 5(b) is a graph for explaining a method for avoiding surging. Figure 6 (
a). (b) is a vane angle plane for explaining the external method, FIG. 7 is a block diagram of the remaining centrifugal compressor to which the method of this embodiment is applied, and FIG. 8 is a conventional general multistage compressor. FIG. 9, a block diagram showing a centrifugal compressor, is a reference for explaining the effects of the conventional centrifugal compressor control method. In the figure, 1-centrifugal compressor, 11-14-population guide vane, 15-18-defuser vane, 19a-1
9d-Person log guide vane drive. 19f to 19h- diffuser vane drive device, 20-
Flow rate sensor, 21 - Temperature sensor, 22 - Pressure sensor, 2
4-rotation speed sensor, 27...-humidity sensor, 28-control device.

Claims (1)

[Claims] When controlling the flow rate in the centrifugal compressor by adjusting the angles of the inlet guide vane and the diffuser vane, for a centrifugal compressor having variable angle inlet guide vanes and diffuser vanes on the inlet side and the outlet side, respectively, A flow rate characteristic function and an efficiency characteristic function that are functions of the angles of the inlet guide vane and diffuser vane on the vane angle plane determined by the angles of the inlet guide vane and diffuser vane, and give the flow rate and efficiency according to these angles, respectively. After setting in advance, measure the current angle of the above inlet guide vane and diffuser vane,
Regarding these current angles, the vector in the normal direction of the constant flow rate curve determined by the above flow rate characteristic function, which is directed toward the target flow rate, is determined as the first vane angle manipulated variable vector, and the vector in the tangential direction of the constant flow rate curve is determined as the first vane angle manipulated variable vector. After determining the direction in which the efficiency increases as determined by the above efficiency characteristic function as the second vane angle operation amount vector, these first vane angle operation amount vector and second vane angle operation amount vector are to determine a third vane angle operation amount vector, and control the flow rate of the centrifugal compressor based on the angles of the inlet guide vane and diffuser vane determined by the third vane angle operation amount vector, After the difference between the flow rate of the centrifugal compressor and the target flow rate falls within a predetermined value, the actual flow rate and effective efficiency are measured at at least three points by operating the inlet guide vane and diffuser vane, and these Develop multiple extrapolation points for the angles of the inlet guide vane and diffuser vane so as to surround the actual measurement points, predict the flow rate and efficiency for each of these extrapolation points from the actual measurement points, and then calculate these extrapolation points. Select an extrapolation point that is close to the target flow rate and has high efficiency from among the interpolation points, and calculate the flow rate of the centrifugal compressor based on the angles of the inlet guide vane and diffuser vane determined by the selected extrapolation point. 1. A method of controlling a centrifugal compressor.