JPS61155697A - Optimum control device of compressor - Google Patents

Abstract

PURPOSE:To enable a power loss to be reduced to a minimum, by previously storing a characteristic, which shows a relation between the actual suction quantity and the head in a compressor, in a function generator and controlling a delivery pressure using an output of the function generator, inputting the actual suction quantity, as a head target value. CONSTITUTION:A control device, while a compressor 3 is in compressing action, receives by an arithmetic device 25 an output P1 of a pressure detector 21, output width(s) of a temperature detector 23 and an output DELTAP of a differential pressure detector 24, obtaining an actual suction quantity Qa. A function generator 26 previously stores a characteristic curve showing a relation between the actual suction quantity Qa and its corresponding surge control line. While the function generator 26, outputting a head target value SV corresponding to the actual suction quantity Qa to be given to a head adjusting meter 29 and performing an arithmetic control operation in relation to a head deviation quantity (PV-SV), partly releases compressed air by giving an opening instruction MV to an air release valve 12. Thus a working point is reset to return onto the surge control line. In this way, the control device, enabling said line to be set approaching to the surge line and suppressing the release of air when the compressor is in low load operation, enables a power loss to be reduced to a minimum.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an improvement of an i+l control device for a pressure 4M machine.

(Prior Art) Pressure JI machines are widely used in various process applications. FIG. 7 is a diagram showing an example of a characteristic curve of air pressure Sl [(hereinafter simply referred to as compressor) of an example of a commonly used suction guide vane. In the figure, the horizontal axis is 1M <Nl
3,/h), and the vertical axis is the discharge pressure (Kg/ci+'
) is shown. The figure shows a characteristic curve with the guide vane angle as a parameter. /1 is the surge line. In this excellent compressor, the discharge pressure increases as the flow rate is reduced, but when this pressure exceeds a certain value, it becomes abnormally operating (vibrations and abnormal noises occur). The envelope of this critical pressure is the surge line.

12 is a constant pressure line, and control is normally performed such that the discharge pressure of the compressor is placed on this constant pressure line/2. 13 is the surge control line, and the discharge pressure is surge line/I
There is a line in front of it before it reaches! ! Subtracting 3, care has been taken to ensure that the compressor does not cause surging under any circumstances.

Figure 8 shows compressed IlliI1gI with surging prevention.
FIG. 1 is a configuration diagram showing an example of a device. Air that has passed through the suction filter 1 enters the compressor 1I3 via the guide vane 2 and is compressed. Compressed air is supplied to the load via the control valve 4. In some cases, compressed air from other compressors may also be added as shown in the figure. The discharge pressure on the compressor outlet side is detected by pressure detection 115,
Sent to pressure regulation Hf 6. The wA pressure regulator 6 drives the guide vane 2 via the load distributor 7 so that the pressure measurement value matches a predetermined target W value.

As a result, as the required load FitIIl decreases, the blade angle of the guide vane 2 is changed, and a constant-pressure dividing section is performed that moves along the line 12 in FIG. 7 in the direction of the arrow. Here, the control point is the surging control line Il! of FIG. When the flow Il detector 8. is reached, the flow Il detector 8. Square root calculator 9. Function generator 10
．． A surging prevention device composed of a surge controller 11 and a blowoff valve 12 works to release compressed air from the blowoff valve 12 to lower the discharge pressure and prevent the occurrence of surging.

Next, the operation of the surging prevention 1t[Il will be summarized as follows. After the flow rate of the compressor 3 is detected by the flow rate detector 8, it enters the square root calculator 9. The output of the square root operation a9 enters the function generator 10, and the function generator 11
10 supplies the discharge pressure corresponding to the flow rate to the surge controller 11 with a target of 1 m5v. On the other hand, the actual discharge pressure is
The pressure is detected by a pressure) J detector 13 provided on the discharge side, and is provided to the surge controller 11 as a measured value P■. Surge XI! When PV is about to exceed S, the operating output MV is applied to the blowoff valve 12, which opens the valve to release a portion of the compressed air and lower the discharge pressure.

(Problems to be Solved by the Invention) It is thought that the conventional control system described above can also appropriately control the discharge pressure of the compressor while preventing surging. However, the characteristics of the compressor shown in FIG. 7 are not fixed and constant, but change depending on operating conditions such as suction pressure, i degree, and gas constant Wl (in the case of a process gas pressure wi machine). Therefore,
In order to perform accurate and stable pressure control, it is necessary to automatically change the surge control line /3 in FIG. 7 according to changes in the characteristics of the compressor 3. However, it is difficult to implement such a method in reality, and therefore, in actual control, changes in the characteristics of the compressor 3 are taken into consideration, and
The surge control line/3 had to be set with a considerable margin in relation to the surge line It. This means that the blow-off valve 12 is opened earlier by the margin to start blowing air, which becomes a major cause of power loss during low-load operation, making it impossible to operate efficiently. Ta.

The present invention has been made in view of these points, and
The purpose is to realize an optimal control system for a compressor that can set the surge control line just close to the surge line and perform efficient operation.

(Means for Solving the Problems) The present invention, which solves the above-mentioned problems, stores characteristics indicating the relationship between the actual suction amount of the compressor and the head in advance in a function generator, and temperature.

The present invention is characterized in that the actual suction layer is numbed from the pressure, and the discharge pressure of the compressor is controlled using the output of the function generator, which inputs the actual suction amount, as a head target value.

The gist of the present invention is that the characteristics of the compressor are not determined by the relationship between the discharge pressure and 1 m that can be directly measured, but by using a head (isothermal head or adiabatic head) that indicates the true operating state of the compressor.
It is understood by converting it into the relationship between this and the actual suction layer.

As a result, the characteristics of the compressor are uniquely fixed and do not change, so the function generator allows the surge control line to be set to the very edge of the surge line based on the relationship between the head and the actual suction amount using the polygonal number.

This reduces unnecessary emissions during low-load operation,
The aim is to minimize power loss.

Furthermore, by understanding the compressor characteristics in terms of the head and actual suction layer, the characteristic curve remains constant regardless of the operating conditions, so it can be displayed as a static image on a CRT display, and the operating point can be determined from this point. It can be displayed dynamically on the top. For this reason, the operator can easily visually recognize at what point in the operating range the initial state of compression printing is being operated.

(Example) Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the drawings.

I'! FIG. 1 is a configuration block diagram showing an embodiment of the present invention. Components that are the same as those in FIG. 8 are designated by the same numbers. In the figure, 21 and 22 are pressure detectors that detect the pressure of the compressor 3 intake section, 23 is a temperature detector that detects the temperature of the air in the compressor 3 intake section, and 24 is the orifice differential pressure of the 3rd intake section of the compressor. This is a differential pressure detector that detects 25
are the output Pt of the pressure detector 21 and the output Δ of the differential pressure detector 24
P and the output TS of the temperature sensor 23, the actual intake air volume (hereinafter abbreviated as actual intake volume) Q is determined from these process fluctuations.
The first performance unit 26 calculates a, and 26 is the first calculation 112
This function generator receives the output Qa of No. 5 as input and outputs the head amount corresponding to the actual intake amount Qa as the target value Sv. That is, the function generator 26 stores a characteristic curve showing the relationship between the actual suction IQa, which shows the true operating state of the compressor 3, and the head.

Figure 2 shows the actual inhalation IQa [U3. ．． /h] and head (insulated head or isothermal head) [s ka, /ka
FIG. 3 is an example diagram of a characteristic curve showing a relationship between In the figure, the horizontal axis shows the actual suction ff1Qa, and the vertical axis shows the head. 1
11 is a surge line, /Iin is a surge control line with a broken line configuration, l! 11 is a driving headline. Similar to the characteristic curve shown in FIG. 7, the characteristics shown in the figure also change using the guide vane angle as a parameter.

27 is the temperature Ts at the inlet of the compressor 3, the compressor 3i: [previous pressure Ps (output of the pressure detector 22) and the compressor 3
This is a second computing unit that calculates the generated head of the compressor 3 based on the immediately after pressure pd (output of the pressure detector 28). Note that the second computing unit 27 is further provided with a gas constant and a specific heat ratio.

29 is the output of the function generator 26 as head a*SV.

In a head controller in which the output of the second computing unit 27 is head measurement *pv, the operation output MV of the II meter 28 is the blowoff valve 1.
2 is applied, and air is blown out 11 meters.

30 is a numerical number generator which receives the output (head measurement value) of the second arithmetic unit 27 as an input and generates a characteristic curve as shown in the figure. The opening number generator 3O is used to avoid interference between the blow-off valve 12 and the guide vane 2 below a certain operating point.From the intersection of the surge control line/12 and the characteristic curve of the constant guide vane opening, It is a fold line unit that provides maximum adjustment angle for each head.

31 is a function occurrence! 130 output and load arrangement! The low selector 30 receives the output of the low selector 30 and outputs the lower value.The output of the low selector 30 drives the guide vane 2. 32 is a CRT display illustrating the relationship between the actual intake lQa and the measuring head. The operation of the device configured as described above will be explained as follows.

First, normal pressure Ill III will be explained. The pressure detector 5 measures the discharge pressure of the compression 113 and provides it to the pressure regulator 6 as measurement 1 [PV. The pressure regulator 6 is
The measured value P■ is compared with a predetermined target value Sv, and an operation signal MV corresponding to the deviation between them is output. The output of this pressure regulator 6 passes through a negative and dual distributor 7 to an O-selector 3.
1 is given. The low selector 31 selects the smaller value of the output of the pressure regulator 6 and the output of the function generator 30 and transmits it to the guide vane 2 . As a result, the guide vane 2 changes the blade angle of the guide vane according to the output of the low selector 31 and keeps the discharge pressure of the compression 1113 constant.

On the other hand, while the compression 113 is performing the compression operation, the first operation! 525 receives the output P1 of the pressure detector 21, the output cuff s of the concentration detector 23, and the output ΔP of the differential pressure detection 624,
Calculate and find the actual inhalation IQa.

On the other hand, the function generator 26 stores in advance a characteristic curve as shown in FIG. 2 based on the relationship between the actual suction ff1Qa and the corresponding surge control line.

/12 in FIG. 2 is the surge control line, which is stored as a broken line function as shown in the figure. This actual inhalation IQa
As mentioned above, the characteristic curve showing the relationship between the head and the head is unique to the compression 113 and is uniquely determined with respect to the vane angle.

The vertical axis in FIG. 2 is the compressor head, which may be an adiabatic head or an isothermal head. As the compression FjA3, a multi-stage compressor is usually used, and in this case, since there is intermediate cooling, an isothermal head is often used. The function generator 26 generates a head target ias v corresponding to the actual intake IQa.
is output and given to the head controller 29.

On the other hand, the second arithmetic unit 27 is used immediately before compression 1113.

! Later pressures Ps, Pd, fil! The head measurement value is calculated from Ts, gas constant, and specific heat ratio using the following formula.

Had −(k, / (k−1)′t −RTs
x: (Pd/Ps)exp ((k-1)/k)
-1] His-RTs 10(le (Pd /Ps
) (2) However, Had has a heat insulating head, l-
1is indicates an isothermal head. R is a gas constant, and K is a specific heat ratio. The computing unit 27 performs the computation for either head given by equations (1) and (2), and provides the result to the head controller 29 as the head measurement mpv.

Now that the load is decreasing, the pressure regulator 6 indicates that the second
Assume that the guide vane angle changes in the direction of the arrow on the line in Figure 13 and reaches point B on the surge control line 11z. FIG. 3 is an enlarged view of the vicinity of 8 points. 8
When this point is reached, the low selector 31 switches the output from the pressure regulator 6 to the function generator 30 and supplies it to the guide vane 2. Therefore, since the guide vane angle does not change any further, the operating point tends to proceed in the direction of the arrow from point 8 toward the surge line /++ as shown in FIG.

Then, the head deviation (PV-8V) is reversed from negative to positive. The head controller 29 is
Ill all bullets are applied to the tin bridge, an opening command MV is given to the air discharge valve, a portion of the compressed air is released, and the operating point is set to the surge control line I as shown in Figure 3.
! 12 Pull back up. In this way, the compressor 3 will be operated just at the edge of the surge control line/12.

Note that the compressor 3 in the operating state is determined by the second computing unit 27.
It is not easy to directly calculate the head using equations (1) and (2). Therefore, as shown in the fourth factor, the head is calculated by a combination of a calculation unit and a calculation unit. In other words, Ps and Pd are calculations! ! Enter 141 and P
The division of d/PS is performed and the following function is generated! 142, (Pd /Ps) exp ((kl),'k
) -1 or 1toae (Pd /Ps
) is output. The output of the function generator 42 is
3, head 1-1ad shown in equations (1) and (2)
Alternatively, HIS is calculated.

FIG. 5 is a timing chart showing operation waveforms of each part. In the figure, fl indicates the load flow rate, 2 indicates the guide vane angle, 3 indicates the head target value S, f4 indicates the compressor head measurement (ltlPV), and t5 indicates the output of the head controller 29. Assume that the load flow rate, which was constant before time t1, begins to decrease at time 1.The discharge pressure of the compressor 3 is controlled to a constant pressure by the pressure regulator 6 by adjusting the guide vane angle ( In other words, when the load flow rate further decreases and reaches point 8 (compressor head - head target 1llI), and the flow rate continues to decrease even after time 2, the head 111 given by the first lIl@ generation fi26 The capacity of the can is greatly reduced, and a positive deviation is generated on the controller as shown in the figure.In order to cancel this deviation, the head controller 1129 issues an opening command to the blow-off valve 12, thereby increasing the suction amount and increasing the suction amount to the compressor. The operating point is returned to point 8 in FIG.

The movement of the operating points as shown in FIG. 5 can be clearly observed by the operator on the CRT display 32.

FIG. 6 is a diagram showing an example of a display on the CRT display 32. By expressing the characteristics of compression 13 in terms of the head and actual suction amount as shown in Figure 2, it is possible to obtain special 1! E curve is inhalation state,
CR is fixed regardless of changes in the physical properties of the gas.
It can be displayed as a background image on the T display 32 as a still image. Furthermore, the digital tllI manufactured by the applicant
If you display the head and actual intake amount as a video using the G-DATA function of the I2D device CENTUM,
The operating point is displayed as the intersection of two straight lines, and the actual operating state can be easily recognized. Furthermore, if not only the head curve but also efficiency and shaft power are displayed, comparison with actual measurements can be used as a guideline for maintenance.

In the above description, the compressor 3 is driven by constant speed rotation, but a variable speed drive type compressor has a capacity of 1111! !
In this case, the present invention can be directly applied to a variable speed drive type compression condyle by considering the parameter (guide vane opening degree) in FIG. 2 as the rotation speed.

(Common Effect) As explained in detail above, according to the present invention, the characteristics of the compressor are not understood as the relationship between the discharge pressure, which is an actual value, and the $1 quasi-state llA sieve flow m. By understanding the relationship between the head and the actual suction rod, the compressor characteristics can be fixed and unaffected by changes in suction conditions and gas physical properties. Therefore, it is no longer necessary to take the above-mentioned fluctuation into account as a safety margin when setting the surge prevention line, and the control line can be set close to the compressor surge line. This is realized by the control Xl arrangement C already described. This makes it possible to suppress unnecessary M wind during low-load operation as much as possible.
Unnecessary loss of fishing power is saved.

In addition, since the compressor characteristic curve is uniquely fixed as unique to the compressor, the characteristic curve can be displayed on a CRT, and the compressor operating point can be dynamically superimposed on this characteristic curve. I can do it. As a result, not only the operation of the surge control W device but also the operating state of the compressor can be grasped more comprehensively than with individual indicators, and the operator can more easily grasp the overall operating state.

[Brief explanation of drawings]

FIG. 1 is a configuration block diagram showing one embodiment of the present invention, and FIG.
The figure shows the characteristics of the compressor, and Figure 3 is a partially enlarged view.
Figure 4 is a diagram showing the specific configuration of the arithmetic unit, Figure 5 is a timing chart showing the operation of each part, Figure 6 is a diagram showing an example of a display on a CRT display, and Figure 7 is the characteristics of the compressor. FIG. 8 is a diagram showing an example of a conventional device. 1... Suction filter 2... Guide vane 3.
··compression! 114... Valve 5.21, 22.28... Pressure detector 6... Pressure regulator 7... Load distributor 8... Flow rate detector 9.25.27... Performance fliB 10 .26.30... Function generator 11... Surge controller 12... Air discharge valve 23...
・Temperature detector 24...Differential pressure detector 29...Head controller 31...Low selector 32...CR
T display 41. 43...Arithmetic unit 42...Function generator Patent applicant tR Kawakita Tatsu m1 machine Co., Ltd. 2 diagram M4 diagram

Claims (1)

[Claims] Characteristics indicating the relationship between the actual suction amount of the compressor and the head are stored in advance in the function generator, the actual suction amount is calculated from the temperature and pressure of the compressor input section, and the actual suction amount is input. An optimal control device for a compressor, characterized in that the discharge pressure of the compressor is controlled using the output of a function generator as a head target value.