JPS59113210A - Clearance control system for steam turbine - 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 the control of the gap between the tip fin attached to the side wall of the rotor blade tip of a steam turbine and the seal ring, and the efficiency of crushing insects constituting a steam turbine plant. It is effective for improvement.

[Prior art]

With the rise in fuel and construction costs in recent years, there is a strong need to improve the efficiency of power generation plants. To this end, various efficiency improvement measures have been studied, and some have been put into practical use. In particular, improvements in the internal efficiency of steam turbines, which have the greatest impact on thermal efficiency, have steadily achieved great results. Internal efficiency currently reaches 90-92% in many cases, and it is difficult to expect much improvement in the future. Internal leakage losses account for a large proportion of the various losses that control internal efficiency. In order to reduce leakage loss, there are 1) reductions in leakage area, 2) increase in the number of fins, 3) optimization of the shape of the side wall and fins at the tip of the rotor blade, etc. Term 3) linearly reduces loss. reduce

However, in the high and intermediate pressure stages of a steam turbine, the specific volume of steam is small, so the blade length is short and the leakage area is relatively large.

The gap between the side wall at the tip of the rotor blade and the tip fin is determined so that the two do not come into contact, taking into account shaft vibration and thermal deformation that occur from startup to the operating point.

Therefore, the gap must be made large in order to provide sufficient margin for various operating conditions and steam amounts.With conventional uncontrolled methods, there is a limit to reducing the amount of leakage that passes through the gap. .

[Purpose of the invention]

An object of the present invention is to provide a gap control system that improves efficiency by minimizing the gap between the side wall of the tip of a steam turbine blade and the tip fin to reduce the amount of leakage.

[Summary of the invention]

For the above purpose, the present invention provides a tip fin that is opposed to the rotor blade by using supply steam, steam branched from a part of the membrane structure, or steam cooled by a water supply system to fill the gap between the side wall of the tip of the rotor blade and the tip fin. Its unique feature is that it is configured to control the amount of leakage to a minimum by heating or cooling the seal ring with a while measuring the gap, and to recover heat from the steam after use to the exhaust or water supply system. It is something that you have.

[Embodiments of the invention]

Hereinafter, a specific embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3.

FIGS. 1, 2 and 3 show a schematic diagram of a method for controlling a gap in a steam turbine according to the present invention. That is, boiler 1, high pressure turbine 2. Medium pressure turbine 3. In a steam turbine plant consisting of a low pressure turbine 49, a generator 5, a water pump 6, etc., a branch steam system 19 from the main steam 14 is provided and used for gap control. Also 1
Gap side (a return steam system 20 using 1gIvc is installed,
In order to recover this heat, it is configured to be returned to a connecting pipe 17 that communicates with the exhaust system of the intermediate pressure turbine 3.

In the embodiment shown in Fig. 1, the steam outlet is connected to the main steam immediately after the boiler 1, and the return destination of the steam used for gap control in the boiler 1 is guided to the exhaust system of the intermediate pressure turbine. However, this does not have a limited meaning, and depends on the temperature and heat load of the structure of the high-pressure turbine 2, the number of control stages, etc.

For example, as shown in Fig. 2, the steam outlet can be a bleed port from between 20 stages of the high-pressure turbine, and if low-temperature steam is required for gap control, one branch is shown in Fig. 3. The steam 19 is guided to the high pressure feed water heater 13 and the cooled steam can be used for gap control, and as for heat recovery, it can be returned to the high pressure feed water heater 12 as shown in FIG. It is determined from the optimum conditions of the considered plant thermal cycle.

By configuring the steam generation system as described above, it is possible to generate steam that makes it possible to control the gap between the side wall of the tip of the rotor blade of the high-pressure turbine 2 and the tip fin.

Now, using such a steam generation system.

An embodiment of a method for controlling the gap between the tip fin and the side wall of the rotor blade of the high-pressure turbine 2 will be described with reference to FIG.

FIG. 4 shows a detailed configuration for controlling the gap 27 between the side wall 22 and the tip fin 23 at the tip of the rotor blade of the high-pressure turbine.

Side wall 22 at the tip of the rotor blade and a seal ring 24 opposed to it
The casing 31 has a function of uniformly spraying steam onto the tip fins 23 and the seal ring 24 attached to the bottle, and includes a plurality of distributors 25 arranged in the circumferential direction and a casing 31 having steam inlets and outlets.

In this figure, the main steam 19 is led to the inlet 32 through the switching valve 29, is blown onto the seal ring 24 from the distribution pipe 25, and is then used for multiple flows through the outlet 33.

The flow rate of the outflowing steam is controlled through the outlet control valve 28, and then heat is recovered to the exhaust system or the water supply system. The outlet control valve 28 is controlled by the controller 30 so that the gap 27 is measured by the gap sensor 26 and the gap is at a minimum value. Note that if low-temperature steam is required due to design conditions, the low-temperature steam can be guided to the distributor 25 by switching the switching valve 29.

The embodiment shown in Fig. 4 shows a single-stage gap control method, but in the case of multiple stages, the configuration of this embodiment can be adopted for each stage, and the steam system can be arranged in series or parallel. Easily expandable. Furthermore, if there are few fluctuations in steam conditions or heat loads and thermal deformation of the side wall or seal ring at the tip of the rotor blade can be estimated, the switching valve, controller, and gap measuring device can be omitted.

In this example, application to a high-pressure turbine was described.
This gap control method can be applied to both medium-pressure turbines and low-pressure turbines for steam intake.

The extraction system differs depending on each case.

〔Effect of the invention〕

If the above-described gap control method according to the present invention is applied to a steam turbine, the gap can always be kept at a minimum in response to changes in the steam heat load, thereby improving the reliability of the contact between the side wall and the fin. It is possible to reduce the amount of leakage between paragraphs without dropping the container, thereby improving performance. The structure of this method is simple and there are no moving parts.

It is highly reliable and inexpensive, and because the steam used for gap control is returned to the exhaust system or water supply system and used to heat steam or water, deterioration in plant efficiency is minimized.

I! If the thermal deformation of the side wall or seal ring at the tip of JJIL can be predicted, a gap measuring device controller etc. can be omitted and an inexpensive system can be created, which is extremely economical and highly practical.

[Brief explanation of the drawing]

1, 2, and 3 are system diagrams of a steam turbine plant applied to a high-pressure turbine according to an embodiment of the present invention;
The figure is also a partially detailed explanatory diagram. 2...High pressure turbine, 19... Branch steam, 20...
・Return steam, 21... Moving blade, 22... Moving blade tip side wall, 23... Chimp fin, 24... Seal ring,
25... Distributor, 26... Gap measuring device, 28...
Outlet control valve, 29... switching valve, 30... controller, 3
1...Casing.゛Sev

Claims (1)

[Claims] L In a steam turbine plant consisting of a boiler, turbine, condenser, feedwater pump, feedwater heater, etc., a part of the supplied steam, steam branched from two parts of the membrane structure, or steam cooled in the feedwater system is used to cool the rotor blades. While measuring the gap by heating or cooling the cooling ring placed opposite to the cooling ring, the system controls the leakage amount to the minimum according to changes in steam conditions and steam amount, and also directs the heated or cooled steam to the exhaust system. A gap control method for a steam turbine characterized by recovery.