JPS59119096A - multistage compressor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a multi-stage compressor in which a flow rate control device is provided on the inlet side of a first-stage compressor, and an intercooler is provided between each stage of compressors. It is.

[Prior art]

A compressor with an intercooler installed between each stage is used when high efficiency is required, with the purpose of lowering the suction temperature of the stage and reducing the shaft power. It is well known that efficiency in this reduction operation is important because it is rarely used at one point and is often operated at a flow rate smaller than the specified point.

As means for performing the above-mentioned reduction operation, when the first stage is a centrifugal type or an axial flow type, an entry rope control and a stator vane variable pinch are generally used, respectively. The weight loss characteristics are shown in FIGS. 1 and 2, in which the horizontal axis represents the flow rate and the vertical axis represents the pressure. Curves A and B in FIG. 1 represent the specification state and any reduced operation state, respectively, and the straight line S represents the plant resistance line (compressor operating line). In fact, the compressor is operated at the intersections A, B, of the curves A, B and the straight line B.

Figure 2 shows flow rate on the horizontal axis and efficiency on the vertical axis, with curves C and D corresponding to curves A and B in Figure 1, respectively, and curve E representing the first curve. It connects the efficiencies on the resistance line S in the figure.

Usually, the intersection point Ao of the curve A and the resistance line S is selected as the design point, and the efficiency at this point is the highest, and the efficiency decreases as the weight is reduced.

This decrease in efficiency during weight reduction will be explained with reference to FIG. 3, which shows the characteristics of the second and subsequent stages.

That is, curves F and G indicate the flow rate and efficiency characteristic curves of the stage, and point A21 A3 corresponds to curve A and resistance curve S in Fig. 1.
It corresponds to the intersection Ao with the point Ao, and also the point B2.

B3 is the intersection B of the curve B and the resistance curve S in FIG.

This corresponds to The design point of the stage in Figure 3 is A
2, the efficiency at this point A2 is the highest, and this point A
2. Efficiency decreases as the flow rate increases or decreases.

Figure 4 shows the characteristics of the first stage, and the curves Fl, F
2 and G+, G2 indicate flow rate and efficiency characteristic curves.

Moreover, the curves F+ and G1 represent the initial stage characteristics in the specification state corresponding to the curve A in FIG. 1, and the curve F2. G2 shows the characteristics of the first stage in the reduced operating state corresponding to curve B in FIG. 1, respectively. A is the design point on the curve Fl
At point 4, the efficiency is maximum, and at the time of weight loss, the efficiency decreases at point B5 than at point A5.

As described above, in the conventional six-stage multi-stage compressor, the efficiency of each stage decreases during the reduction operation, so the overall efficiency decreases. Furthermore, even during reduced operation, the same amount of cooling water is supplied to the intercooler, which has the disadvantage of being disadvantageous from the viewpoint of operating costs, especially when used in areas where water is at a premium.

[Purpose of the invention]

In view of the above, it is an object of the present invention to operate the compressors of each stage at the highest efficiency point possible to improve the overall efficiency and to reduce the amount of cooling water during reduced operation.

[Summary of the invention]

In order to achieve the above object, the present invention provides a multistage compressor in which a capacity control device is provided on the inlet side of the first stage compressor, and an intercooler is provided between the compressors in each stage. Install a temperature sensor on the suction side of any compressor,
The temperature sensor is connected to the capacity control device via a computing unit, and the computing unit operates a flow rate control valve provided at the inlet or outlet side of the cooling water of each intercooler. It is characterized by this.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 5, 1 to 3 are compressors of the first stage, second stage, and third stage, and 4 and 5 are intercoolers installed between each of the first stage compressors. ,5
Pipes 9 and 10 through which cooling water circulates penetrate through the pipes 9 and 10, respectively. Reference numeral 6 denotes a flow rate control device provided on the suction side of the first stage compressor 1, and a working gas suction pipe 7 is connected to this flow rate control device 6. As the flow rate control device 6, an inlet vane control is used when the compressor 1 is a centrifugal type, but a stator vane variable mechanism is used when the compressor 1 is an axial flow type.

8 is a discharge pipe connected to the discharge side of the compressor 3 in the final stage (3rd stage in the figure); 11 is a temperature sensor attached to the thread path between the intercooler 4 and the second stage compressor 2; 12 is a computing unit connected to the flow rate control device 6, temperature sensor 11 and solenoid valve 13.14, and the solenoid valve 13.14 is connected to the intercooler 4.
, 5, respectively, are provided on the inlet side (or outlet side) of the cooling water pipes 9, 1o that penetrate through the tubes 9, 5, respectively.

The present embodiment has the above-mentioned configuration, in which the working gas flows into the first stage compressor 1 through the suction pipe 7 and the flow rate control device 6, is pressurized, and then passes through the intercooler 4 to the second stage compressor 2.
After passing through the intercooler 5, the air flows into the final stage compressor 3, where the pressure is further increased, and is then fed to a predetermined section through the discharge pipe 8.

In this case, if the characteristics of the compressor in each stage are known, it is possible to calculate to what temperature the suction temperature of the compressor in the second and subsequent stages should be set during the reduction operation. The relationship between these, ie, the relationship between the second-stage suction temperature and the opening degree of the flow rate control device, is as shown in FIG.

In the above-mentioned embodiment (FIG. 5), the relationship shown in FIG. 6 is set in the calculator 12, and the suction temperature of the second stage compressor 2 is determined from the opening signal of the flow control bag 1 and 6. The cooling pipe 9 in the intercooler 4 is connected via the solenoid valve 13 to the suction temperature of
Adjusts the amount of cooling water flowing through. Such operations are similarly performed in the intercooler 5 and the third stage compressor 3.

That is, the computing unit 12 calculates the difference between the signal value from the temperature sensor 11 and the target temperature, and when this difference is a positive value, the solenoid valves 13 and 14 are opened, and when the difference is a negative value, the solenoid valves 13 and 14 are opened. Close 13.14. A series of processing procedures in the arithmetic unit 12 as described above is shown in block diagram No. 9.
It will look like the figure. In this case, since it is difficult to make the actual suction temperature Ts of the second stage compressor match the target suction temperature Ts, the control is terminated once the actual suction temperature Ts falls within a certain range.

Second stage compressor and third stage compressor in this embodiment 2.
The characteristics of 3 are shown in Figure 7.
, H2 + As t B2 + B3, etc. are the same as those in FIG. 3, so their explanation will be omitted.

In other words, curves F and G show the characteristics of the 5th and 3rd stage compressors, respectively, and even if the operating point of the entire compressor is the same, the distribution of pressure rise in each stage will change. Therefore, the performance of each of the second and third stage compressors also shifts from point B2 to point B'.

Even in such a state, the flow rate and discharge amount of the compressor do not change, and the changes in the second and third stage compressors can be covered by capacity control of the first stage compressor.

Now, when the amount of cooling water decreases, the suction temperature increases [1,.

Since the suction flow rate (volume flow rate) increases, the operating points of the second and third stage compressors shift from B2 to 82' and from B3 to 83', respectively, so the efficiency of the third stage compressor also increases. As shown by point B3', the operating point B3 is also higher. When the operating point moves in this way, the operating point B2 + B
As is clear from the comparison of 3/, the pressure in each of the second and third stage compressors is insufficient. Therefore, in order to make the final discharge pressure the same, the discharge pressure of the first stage compressor must be increased.

Therefore, as shown in Fig. 8, the characteristic curve showing the operation of the first stage compressor shifts from F2 to F2', and the operating point also changes from B4 to B.
Move to 4/. At this time, it is clear from the efficiency characteristic curve that the efficiency of the first stage compressor also increases slightly from B5 to B5/.

As described above, according to this embodiment, the efficiency of each membrane compressor can be improved by reducing the amount of cooling water during the reduction operation. At the same time, when considering the long-term operating conditions of the compressor, it is possible to significantly reduce the average amount of cooling water by saving cooling water during reduced operation.

〔Effect of the invention〕

As explained above, according to the present invention, the efficiency of the multistage compressor can be further improved and the amount of cooling water can be reduced, so that the operating cost can be significantly reduced.

[Brief explanation of the drawing]

Figures 1 to 3 are diagrams showing the pressure characteristics and efficiency characteristics of a conventional multistage compressor, and the characteristics of each membrane compressor from the second stage onward, respectively.
Fig. 4 is a diagram showing the characteristics of a first stage compressor equipped with a flow rate control device, Fig. 5 is a system diagram showing an embodiment of the multistage compressor of the present invention, and Fig. 6 is a diagram showing the characteristics of the same embodiment. 9 are block diagrams showing the processing contents of the arithmetic unit of the same embodiment. 1... First stage compressor, 2... Second stage compressor, 3...
3rd stage compressor, 4, 5... Intercooler, 6... Capacity control device, 11... Temperature sensor, 12... Arithmetic unit,
13.14...Solenoid valve. ■ 1 Figure 1 Army Z Figure 5 Turtle! Punishment 4 Figure 5 Figure 5 Z z Figure 7 Figure 7

Claims (1)

[Claims] In a multistage compressor in which a capacity control device is provided on the inlet side of the first stage compressor and an intercooler is provided between the compressors in each stage, a temperature sensor is installed on the suction side of any compressor from the second stage onwards. The temperature sensor is connected to the flow rate control device via a computing unit, and the computing unit is configured to operate a flow rate control valve provided at the inlet side or outlet side of the cooling water of each of the intercoolers. A multi-stage compressor characterized by: