JPS5954737A - Restriction of thrust - Google Patents

Abstract

PURPOSE:To eliminate thrust variation and prevent breakage by controlling the air flow-rate in abnormal state in the case when an axial through load is controlled by introducing the air bleeded from a high-pressure side bleeding line into a low-pressure side balance piston part, in a biaxial gas turbine. CONSTITUTION:A thrust restricting valve 15 is installed in a balance air line 8 which is inserted into a balance piston 21 part at the outlet edge of a low-pressure turbine 5 after bleeding from a high-pressure compressor 1. A balance air line 16 which communicates from a balance piston 22 part at the discharge edge of a low-pressure compressor 6 to the inlet of the low-pressure compressor 6 is installed, and an ON/OFF valve 17 is installed midway. A limit valve 15 and the ON/OFF valve 17 operate to be perfecty opened and closed respectively during the rated operation, while when a load is cut-off, the ON/OFF valve 17 is immediately opened, and the limit value 15 is closed after the lapse of a predetermined time and closed to the minimum flow-rate level. Thus, the pressure succeeding to the limit valve 15 is reduced, and also the pressure in the line 16 is reduced, and thus thrust variation is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thrust limiting method for a two-shaft Φ reburning gas turbine.

FIG. 1 shows an air system diagram of a conventional gas turbine. This gas turbine is a twin-shaft reburning type, with two reburners, a compressor in the high-pressure system and a low-pressure system, and uses a two-stage compression system to achieve the highest efficiency point. Tame, Takano I
:, the pressure distribution between the compressor 1 and the low pressure compressor 6 is changed.

In addition, by separating the high-pressure system shaft and the low-pressure system shaft and changing the rotation speed, the decrease in efficiency due to partial negative operation is minimized. For this reason.

As shown in Figure 2, in the low pressure system, there are 11 low 1-E earth shrinkage stations 6
The discharge pressure lO of is 4.8 kf/cni, while the inlet pressure 9 of the low pressure turbine 5 is as high as 8.8 KW/ad. It is 1j12 that it is impossible to balance the thrust. For this reason, the bleed air from the high-pressure compressor 1 is used and connected to a balance piston 21 provided at the output end of the low-pressure turbine 5 to perform forced thrust balance.

In this case, the thrust balance at one rated load point can be achieved by constricting the bleed point of the high-pressure compressor 1, and it is impossible to create the optimal balance by changing the pressure inserted into the balance piston 21. be.

However, in the event of an abnormality such as during load cycling, in order to prevent the overspeed of the low pressure 1 drawing, it is necessary to lower the discharge pressure of the low pressure compression ridge 6 more slowly than the bending pressure. The pressure at point r changes linearly from 1 to no. Figure 2 shows the pressure change under full load and tilting. Also, FIG. 3 shows the thrust change of the low-pressure shaft system at this time.

From this, the thrust at the rated negative point is 26■ (■
(indicates that the thrust is directed toward the peeping machine side), whereas negative F [i after 6 seconds.

○Changes up to 65■. For this reason, it is necessary to use a large thrust bearing 25 that can tolerate loads from 8926°f to f-)65cm.

Since such a large change occurs from the 89 side to the e side, an impact force is applied to the thrust bearing 25.

This can lead to oil film failure, bearing damage, and even turbine damage. Also, as shown in Figure 3, the thrust of the low pressure turbine 5 changes from ■87T to e6T, and the casing of the low pressure turbine 5 also changes from ■ to e due to the reaction force. Change. For this reason, Ku7
The support securing the ring must be fixed in both directions.

It is extremely difficult to manufacture and assemble.

An object of the present invention is to provide an fCIII system that eliminates instantaneous excessive thrust changes that occur in a low-pressure shaft system and has a stable thrust balance even under abnormal conditions.

The gist of the invention is to limit the air flow rod inserted into the balance piston at the outlet end of the low pressure turbine.

FIG. 4 shows an embodiment of the present invention.

In a balance air line 8 that extracts air from the high-pressure compressor 1 and inserts it into the balance piston 21 at the output end of the low-pressure turbine 5, a thrust restriction valve 15 is provided midway through the air line 8. Further, a balance air line 16 is provided that connects the discharge fillyffit balance piston 22 of the low pressure compressor 6 to the inlet of the low pressure compressor 6, and an on-off valve 17 is installed on the way.

The opening and closing procedure of each valve is shown in FIG.

During rated operation, the restriction valve 15 is kept fully open and the on-off valve 17 is kept fully closed. At this point, the presence or absence of both valves 15 and 17 has no effect, and the reconnaissance performance is exactly the same as that of the conventional example.

When the load is cut off, the on-off valve 17 starts to open immediately by the on-off valve control device 24, and is fully opened after 3 seconds. The restriction valve 15 begins to close after 1 second and closes to the lowest flow level after 5 seconds by the restriction valve controller 23.

This minimum flow rate level is set as the minimum required flow rate as a shaft seal inside the low pressure turbine 5. As a result, the balance air line 8 of the low pressure turbine 5 is
After 1 second, the restriction valve 15 is closed and the balance air line 8 is closed.
Since the amount of air passing through is restricted, the pressure after the restriction valve 15 decreases, and the force pushing the low-pressure turbine 5 in the e direction weakens.

Moreover, the pressure of the balance air line 16 of the low pressure compressor 6 is
By opening the on-off valve 17, the inlet pressure of the low-pressure compressor 6 is reduced to the atmospheric pressure, and the thrust in the e direction is reduced similarly to the low-pressure turbine.

Figure 6 shows the pressure change when the present invention is applied.
The figure shows the thrust change at that time.

As a result, the total thrust 14a is from Φ26■,
Although it changes to the lowest e6T 6 seconds after load shedding, the change *i is very small compared to the conventional example. And from the thrust 1,2a4°@86 '@' of the low pressure turbine 5,
It only fluctuates between Φ23T and does not decrease to the e direction. For this reason.

The capacity of the thrust bearing 25 can be small, instantaneous excessive thrust changes are eliminated, U, l111 + selection is avoided, and the structure is such that only the fixed direction of the low pressure turbine 5 can be identified. It becomes possible.

Furthermore, each valve 15.17 is susceptible to fluctuations immediately after load shedding.
After 60 seconds have elapsed, each valve's control device 23 and 24 is operated in the exact opposite manner to the opening/closing operation described above, in order to return the valve to its initial state. do.

In Figure 1, 2 is a high-pressure combustor, 3 is a high-pressure turbine, 4 is a reheater, 7 is a firing ridge, and 11 is an extraction air line pressure collar 13.
a is the low pressure compressor thrust, 18 is the limit valve opening degree, and 19 is the opening/closing valve opening degree.

[Brief explanation of drawings]

Figure 1 is a conventional gas turbine air system diagram, Figure 2 is a conventional pressure change characteristic diagram during negative # connection, Figure 3 is a conventional thrust characteristic diagram during load shedding, and Figure 4 is the present invention. Figure 5 is a diagram showing the valve opening/closing procedure, Figure 6 is a pressure change characteristic diagram during load shedding when the present invention is applied, and Figure 7 is a negative diagram when the present invention is applied. It is a thrust change characteristic diagram at the time of 1457. 8...Extraction air line, 15...fljlJ limit valve,
16...1 air outlet, 17...on/off valve, 2
3... Limiting valve control 11j device, 24... On-off valve opening side 1 device. Agent: Masu Rishi Akio Takaaki [,,. 1 ", Pa□・1 v, 10 '$2 Figure ¥30 60th jump 60 'I throat' 7th flash

Claims (1)

[Scope of Claims] 1. In a method of adjusting shaft thrust by introducing air τ extracted from a high-pressure side oil/air line to a low-pressure side balance piston in a two-shaft gas turbine, the amount of air in the oil/air line A thrust limiting method characterized in that the thrust is controlled at abnormal times. 2. A compressor with a balance piston at the discharge end. A thrust limiting method characterized by controlling the amount of air discharged from the line connecting the balance piston to the low pressure side in the event of an abnormality.