JPS6241904A - Steam turbine - Google Patents

Abstract

PURPOSE:To reduce pressure loss and improve efficiency by providing a flow path regulating plate for changing the area of a steam path according to turbine load in an outlet of a final stage moving blade of a turbine. CONSTITUTION:In an outlet of a final stage moving blade 37 of a turbine exhaust chamber is provided a flow path regulating plate 50. And the regulating plate 50 is controlled to provide an optimum steam path area for steam flow according to turbine load. Thus, the pressure loss in the outlet of the final stage moving blade can be reduced to improve efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a steam turbine in which a steam passage from a final stage rotor blade outlet to an exhaust chamber is improved so as to reduce energy loss.

[Technical background of the invention and its problems]

In recent years, in steam turbine power plants, there has been a tendency to increase the capacity of a single steam turbine.

In this case, the amount of steam passing through the turbine becomes enormous, and energy loss due to hydrodynamic resistance occurring in the steam passage cannot be ignored.

In particular, energy loss occurring in the steam passage from the final stage of the low-pressure turbine to the condenser is an important issue because it has a large effect on the efficiency of the entire power plant.

In addition, with the increase in the amount of electricity generated by nuclear power generation in recent years,
Thermal power generation plans 1~ and newly built thermal power plants, which have traditionally been operated under base operation, are now operating under intermediate load operation.

In general, the final stage has a large effect on the efficiency of the entire plant, and the exhaust loss occurring in the steam path from the final stage to the condenser accounts for a considerable proportion of the turbine loss. On the other hand, steam passages such as the final stage and exhaust chamber are 100%
The steam passage is designed to be optimal during load operation. Therefore, in the case of intermediate load operation, the area of the passage is too wide for the flow rate of steam flowing inside the turbine, resulting in regions where steam hardly flows or regions where reverse flow occurs, increasing internal losses and reducing power plant efficiency. It's arousing.

Incidentally, the exhaust loss occurring in the steam passage from the final stage rotor blades to the condenser of the low-pressure turbine accounts for a considerable proportion of the loss of the entire turbine.

This tendency is particularly noticeable in the case of intermediate load operation, and is a major problem as it increases turbine loss and causes a significant drop in power plant efficiency.

In conventional low-pressure turbines, the steam passage section is designed to optimize the flow of steam during 100% load operation. During partial load operation, the steam flow rate is lower than during 100% load operation, so the steam pressure in the turbine stage is lower than during 100% load operation. Further, at the inlet of a turbine rotor blade, the pressure at the tip of the blade is usually higher than the pressure at the root of the blade. However, the degree of vacuum in the condenser is almost the same during partial load operation as it is during 100% load operation, and the outlet pressure of the final stage rotor blades is also almost the same between partial load operation and 1.00% load operation. . Therefore, during partial load operation, the outlet pressure of the final stage rotor blade becomes higher than the pressure at the inlet root portion of the final stage rotor blade or the root portion within the steam passage portion of the final stage rotor blade.

As a result, as shown in FIG. 7, in the conventional low-pressure turbine, during partial load operation, there is no steam flow at the root of the final stage motion g37, and the flow = 3.
- Separation occurs and there is a region where steam does not flow even at the exit of the final stage rotor blade 37. Since the pressure in this region is low, it ultimately becomes a backflow region 41, creating a large vortex and causing a very large pressure loss.

Therefore, as shown in the relationship diagram between specific turbine efficiency and turbine load shown in Fig. 6, in conventional steam turbines, as the turbine load decreases as shown in characteristic T, the specific turbine efficiency decreases, especially It suddenly decreases from around 60% load. As a result, conventional steam turbines have had the problem of significantly reducing power plant efficiency during partial load operation. Note that the specific turbine efficiency shown on the vertical axis in FIG. 6 is a value obtained by multiplying the turbine efficiency by the turbine efficiency at 100% load.

[Purpose of the invention]

The purpose of the present invention is to change the steam flow path area at the outlet of the final stage rotor blade of a low-pressure turbine according to the load condition of the turbine, eliminate the backflow region that has been a problem in conventional examples, and reduce pressure loss due to backflow. , Power generation plan 1 - attempts to provide a steam turbine capable of improving efficiency.

[Summary of the invention]

A steam turbine according to the present invention is a steam turbine in which an exhaust chamber connected to an outlet of a final stage rotor blade of a turbine rotor formed at a side end of a turbine casing is opened directly into an upper end opening of a condenser main body body. A plurality of flow path adjustment plates are provided at the root of the final stage rotor blade outlet, one end of which is rotatably attached to the turbine shaft side, and the other end of which can be opened and closed radially. It is.

[Embodiments of the invention]

The present invention will be explained below with reference to the embodiments shown in FIGS. 1, 2, and 3. In FIG. 1 showing the low pressure turbine, an inner casing 32 is provided inside an outer casing 30 with a reinforcing plate 33 interposed therebetween. In the turbine rotor 34, turbine blades 36 and final stage rotor blades 37 are arranged radially in an annular row. Further, a nozzle 35 is held in the inner casing 32 so as to be installed between each row of turbine blades.

A steam pipe 31 is connected to the outer casing 30 and the inner casing 32, and driving steam is injected from the steam pipe 31 into the inner casing 32 and flows into a turbine stage provided therein. Further, as shown by the arrow 40, the steam performs work in the turbine stage, and after leaving the final stage rotor blade 37, it flows into the condenser installed at the bottom of the outer casing 30, where it is condensed and then condensed. bawl.

The present invention is characterized in that a flow path adjusting plate 50 is provided on the exhaust chamber internal cone wall 57 facing the root portion of the final stage rotor blade 37 of the external casing 30 of the low pressure turbine. As shown in FIG. 4, one end of the flow path adjusting plate 50 is swingably attached to a fixture 52 provided on the turbine rotor 34 side of the cone wall 57 inside the exhaust chamber with a pin 54. The free end extends in the direction of steam flow arrow 40 as shown. A push-up rod 56 is attached to the free end of the flow path adjustment plate 50 via a pin 53, and this push-up rod 56 connects the push-up rods 1 to 5 provided on the outside of the external casing 30. has been done.

Therefore, the tip of the flow path adjusting plate 50 is connected to the push-up piston 51.
As a result of this operation, it swings about the pin 54 in the direction of the arrow 55, and its angle O can be arbitrarily set by the piston 51. In addition, the flow path adjustment plate 50 is divided into a plurality of pieces as shown in FIG. There is. As the steam passage portion, it is possible to form a state in which there is no gap on the surface of the flow path adjustment plate 50. The opening pressure PA of the opening of the flow path adjustment plate 50 and the mounting pressure PB are pA=
The steam does not become PB and flow into the back side of the flow path adjustment plate 50. This is because the flow of steam is guided in the direction of the arrow 40 by the flow path adjustment plate 50, and there is no flow path for steam to flow between the divided flow path adjustment plates 50.

As shown in FIG. 4, the opening adjustment device for the flow path adjusting plate 50 inputs a signal input from a turbine load detector M1 that detects the turbine load to an opening calculation unit M2. The opening degree of the flow path adjusting plate 50 is set to H based on
Calculate J and output the opening signal.

The opening adjuster M3, which receives this opening signal, outputs an opening adjustment signal that changes the amount of expansion and contraction of the push-up rod 56 of the push-up rod 51 of the pusher nib 1 hem 51 corresponding to this opening signal. It is sent to the push-up piston 51 to adjust the opening of the flow path adjusting plate 50. Note that oil or air is used as the working medium for the push-up piston 51.

However, in conventional low-pressure turbines, when the turbine load decreases, the steam flow rate decreases.
The steam passage section at the exit of the final stage rotor blade could not be changed at all, and the area of the steam passage section was too wide, causing backflow and large pressure loss.

In contrast, in the present invention, as shown in FIG. 5, the steam passage area is optimized for the steam flow rate according to the turbine load by means of a flow passage adjustment plate 50 that adjusts the opening according to the turbine load. It is possible to change it like this.

In addition, the area where backflow conventionally occurred during intermediate loads is surrounded by the flow path adjustment plate 50 and the cone wall 57 inside the exhaust chamber, and furthermore, the opening pressure PA and the mounting pressure pa can be maintained equal, thereby preventing backflow. This eliminates the occurrence of large pressure loss, which has been a problem in the past, and it is possible to significantly improve the efficiency of the power plant, as shown by the broken line characteristic T2 shown in FIG.

〔Effect of the invention〕

As described above, in the present invention, by providing a flow path adjusting plate at the outlet of the final stage rotor blade, which changes the area of the steam passage part to be optimal for the steam flow rate according to the turbine load, the final stage rotor blade A highly efficient steam turbine can be obtained that significantly reduces pressure loss at the outlet.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the low-pressure turbine section of a steam turbine according to the present invention, FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1, and FIG. 3 is a final stage rotor blade of the low-pressure turbine section. FIG. 4 is a block diagram for explaining the opening control mechanism of the flow path adjusting plate provided according to the present invention, and FIG. 5 is a cross-sectional view showing the enlarged portion of the flow path adjusting plate provided according to the present invention. FIG. 6 is a characteristic diagram showing the relationship between the opening degree and turbine load. FIG. 6 is a characteristic diagram showing the relationship between the specific turbine efficiency and turbine load of the present invention and a conventional steam turbine. FIG. It is an explanatory diagram showing a flow. 30... External casing 31... Steam pipe 32.
...Inner casing 34...Turbine rotor 37
...Final stage rotor blade 40...Steam flow 50.
・Flow path adjustment plate 51 ・Push-up piston 52 ・
... Fixture (8733) Agent Patent Attorney Yoshiaki Inomata (1 idiot) Figure 4 D 10 10.3040,! ;D 60 70
δ0'/D 100 No Don Divine Goods (X) D IOZO3040♂D GC) 7080
'IP0100 No Ton Kyousei (X) Figure 6

Claims (3)

[Claims] (1) In a steam turbine in which an exhaust chamber connected to the outlet of the final stage rotor blade of the turbine rotor formed at the side end of the turbine casing is opened directly to the upper end opening of the condenser body shell, the exhaust chamber A steam turbine characterized in that a plurality of flow path adjustment plates are provided at the roots of stage rotor blade outlets, one end of which is rotatably attached to the turbine shaft side, and the other end of which can be opened and closed radially. (2) It is equipped with a push-up piston that opens and closes the flow path adjusting plate, and further includes a turbine load detector that detects the steam turbine load, and an output signal from this turbine load detector is input, and the flow path is adjusted based on this output signal. The present invention is characterized by comprising an opening calculator that calculates the opening of the adjustment plate and outputs an opening signal, and an opening adjuster that outputs an opening adjustment signal to the push-up piston based on the opening signal. A steam turbine according to claim 1. (3) The steam turbine according to claim 1, wherein the plurality of flow path adjustment plates are configured such that their peripheral edges overlap in a petal shape to form a steam flow path.