JPS6336098A - Control method for multistage centrifugal compressor - Google Patents

Abstract

PURPOSE:To increase the region of capacity control for a compressor in the above caption, by initially fixing variable diffuser vanes at the full opening and controlling inlet guide vanes as far as possible, and then, after fixing id inlet guide vanes, controlling said variable diffuser vanes. CONSTITUTION:By fixing variable diffuser vanes 6 of compressors 2, 3 in a full opening state, inlet guide vanes 4 are throttled to the most possible extent to decrease the gas flow. After that, the opening of said inlet guide vanes 4 are fixed and said variable diffuser vanes 6 are controlled instead. Using the above method, diffuser vanes can be adopted for a compressor of any number of stage to increase the region of capacity control without any loss in the efficiency at the design point.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for controlling a multi-stage centrifugal compressor that has multiple stages of compressors and performs capacity control using an inlet guide vane and a variable diffuser vane. be.

[Prior art]

Centrifugal compressors usually have a surging phenomenon, which limits their capacity adjustment range. Therefore, it is desired to have a wider capacity adjustment range. On the other hand, it is necessary to devise ways to improve efficiency at partial loads as much as possible.

Conventional methods for controlling multi-stage centrifugal compressors include methods for controlling capacity by individually controlling inlet guide vanes or variable diffuser vanes. but,
In constant pressure control, one control method using inlet guide vanes has good efficiency in partial load operation, as shown in FIG. 4, but has the disadvantage that the operable range is only about 70% narrow. The other variable diffuser vane solves the drawback that the capacity control range of the diffuser vane, which has been conventionally used for the purpose of improving the efficiency of the design point, is significantly narrowed. However, as shown in the figure, this variable diffuser vane
Although the operable range is wide, up to about 30% in the case of a single stage, the efficiency of partial load operation is inferior to that of inlet guide vanes.

Examples of solutions to such problems include, for example, Japanese Patent Application Laid-open No. 5
As shown in Japanese Patent Nos. 5-60692 to 5-60692, there is a method of establishing a predetermined relationship between an inlet guide vane and a variable diffuser vane and controlling them simultaneously.

However, in the conventional structure described above, the control system for measuring each element of the inlet guide vane and variable differential user, calculating each of these elements, and instructing each part after calculation is complicated, and the configuration is complicated. It had drawbacks such as inviting cost store knobs.

[Object of the Invention] The present invention has been made in consideration of the above conventional problems, and an object of the present invention is to provide a method for controlling a multistage centrifugal compressor that can be easily and efficiently controlled over a wide range. This is the purpose.

[Structure of the invention]

In order to achieve the above object, the method for controlling a multistage centrifugal compressor of the present invention includes an inlet guide vane provided upstream of the first stage compressor, and an inlet guide vane provided in any stage compressor from the second stage onwards. In a method for controlling a multistage centrifugal compressor that controls capacity by controlling the angle of the variable diffuser vane, the first step is to fix the variable diffuser vane in a fully open state and control the inlet guide vane to the extent possible. After that, fix the inlet guide vane and
The present invention is characterized in that it is configured such that good control can be easily performed by controlling the variable diffuser vane.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

A three-stage centrifugal compressor, which is a multi-stage centrifugal compressor, includes a first compressor 1, a second compressor 2, and a third compressor 3, as shown in FIG.
are connected in series. An inlet guide vane 4 is provided at the front stage of the first compressor 1, and the first compressor 1 and the second compressor
On each discharge port side of the compressor 2 and the third compressor,
A fixed diffuser vane 5 and a variable diffuser vane 6 whose angle is variable are provided. The first compressor 1
and the second compressor 2, and between the second compressor 2 and the third compressor 3, there are a first cooler 7 and a second cooler that cool the gas discharged from the compressors 1 and 2, respectively. A cooler 8 is interposed. Further, driving means 9 and 10 are connected to the inlet guide vane 4 and the variable diffuser vanes 6 of the second compressor 2 and the third compressor, respectively, and both driving means 9 and 10 are connected to an electro-pneumatic converter. A control unit 13 that controls both vanes 4 and 6 is connected through the vanes 11 and 12.

On the other hand, as shown in Fig. 2, the three-stage centrifugal compressor has the following features:
A main drive shaft 14 that receives a driving force from the outside, a drive shaft 15 that is driven by this main drive shaft 14 and rotates the first compressor 1 and the second compressor 2, and rotates the third compressor 3. A drive shaft 16 is provided. A first compressor 1 and a second compressor 2 are provided at both ends of the drive shaft 15, respectively, and a third compressor 3 is provided at one end of the drive shaft 16. Each compressor 1 to 3 has 4 to 6 impellers 17...
A suction pipe 18 is connected to the front of the impeller 17. Also, impeller 17...
A diffuser 20 communicating with the discharge flow path 19 is formed on the outer peripheral side of the . And, as mentioned above, the first
A fixed diffuser vane 5 and a variable diffuser vane 6 are disposed in each of the differential users 20 of the compression a1, the second compressor 2, and the third compressor, respectively.

In the above structure, the constant pressure capacity control state of the three-stage centrifugal compressor is as shown in FIG. In the same figure, curve A
represents the surging line, and B represents the design point.

When performing control, first, the variable diffuser vanes 6 of the second compressor 2 and the third compressor are fixed in a state where the differential user 20 is fully opened, and the first The inlet guide vane 4 provided at the front stage of the compressor 1 is narrowed down to the extent possible to reduce the gas flow rate. This state looks like the curve a-'-c. The range in which the inlet guide vane 4 and the subsequent variable diffuser vane 6 are narrowed is determined by the intersection of the surging line and constant discharge pressure line of the corresponding compressor, and is predictable. Next, at the point of curve C, the inlet guide vane 4 is fixed at the opening degree at that time, and the variable diffuser vanes 6 of the second compressor 2 and the third compressor, which had been fixed until then, are narrowed down. , the operating state is as shown by the curve dg.

That is, with capacity control using only the inlet guide vane 4, if the throttle is narrowed down a little from curve C, a surging state will occur and the operation will become impossible. By narrowing down the options, the range of possible operation will be further expanded.

Note that the variable diffuser vane 6 can be arbitrarily installed from the first compressor 1 to the final stage compressor as necessary. For example, in a four-stage centrifugal compressor, the inlet guide vane 11 is arranged before the first compressor, and the inlet guide vane 11
A variable diffuser vane 6 may be installed in the compressor.

〔Effect of the invention〕

As described above, the method for controlling a multistage centrifugal compressor of the present invention includes:
A multi-stage centrifugal compressor that performs capacity control by controlling the angle of the inlet guide vane installed upstream of the first-stage compressor and the variable diffuser vane installed on any compressor from the second stage onwards. In the control method, first,
Fix the variable diffuser vane in the fully open position,
After controlling the inlet guide vane to the extent possible, the inlet guide vane is fixed and the variable diffuser vane is controlled. Therefore, the diffuser vane can be employed in any stage of the compressor, and the efficiency per stage of the compressor can be improved by up to 5%. Therefore, it is possible to widen the capacity control range without sacrificing the efficiency at the design point, and it is possible to improve the partial load efficiency compared to control using only variable differential user vanes. There is no need to perform complex control such as detecting many elements such as pressure and temperature of the machine and sending instruction signals to each part based on the calculation results of these elements, and the control system configuration is simplified. Costs can be reduced.Furthermore, the reliability of operation can be improved due to the simplification of the control system.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of the present invention, FIG. 2 is a sectional view of the three-stage centrifugal compressor shown in FIG. 1, and FIG.
FIG. 4 is a graph showing the relationship between capacity and discharge pressure in the three-stage centrifugal compressor shown in the figure, and FIG. 4 is a graph showing the relationship between capacity, discharge pressure, and shaft power in the conventional example. 1 is the first compressor, 2 is the second compressor, 3 is the third compressor, 4
1 is an inlet guide vane, 5 is a defined diffuser vane, 6 is a variable diffuser vane, 13 is a control unit, 17
is an impeller, and 20 is a differential user. Patent Applicant: Kobe Steel, Ltd. Mi$1 Figure 3 Figure 1--A: Bushing Line B: Vemi+,! , 60' 60 70 E! 0 90 100 valley land (°/
. ) Fig. 4 □In L, ziJ' Takutohan〃1 force---Gashigo 6 Fei, Hehn'Hl・Decoration-1-Boo-self'nk°line X Membrane material, middle 4, G ya ('/,)

Claims (1)

[Claims] 1. By controlling the angle of the inlet guide vane provided upstream of the first stage compressor and the variable diffuser vane provided in any stage compressor from the second stage onwards,
In a method for controlling a multi-stage centrifugal compressor that performs capacity control, first, the variable diffuser vane is fixed in a fully open state, the inlet guide vane is controlled to the extent possible, and then the inlet guide vane is fixed and the variable diffuser vane is fixed. A method for controlling a multistage centrifugal compressor, characterized by controlling vanes.