JPS61182403A - Drain discharging apparatus of steam turbine - Google Patents

Abstract

PURPOSE:To prevent the leak of working steam by forming the inlet part of a drain discharge hole formed on the bottom part on the lower half side of a drain catch into semispherical form and installing a float and a cover for preventing the floatation of the float in close to the inlet part. CONSTITUTION:A drain collecting groove 13 is formed on the bottom part 12 on the lower half side of a drain catch, and a drain discharge hole 14 which communicates to an exhaust chamber is formed in the collecting groove part 13. The inlet part 15 of the discharge hole 14 is formed into a semispherical groove, and a spherical float 16 smaller than the semispherical groove and a cover 17 for preventing the floatation of the float 16 are arranged at the inlet part 15. Further, a groove 18 for accommodating the float 16 when it is floated-up is formed onto the cover 17. Further, in order to facilitate the drain catching, cut parts 19 for introducing drain and a roof 20 are formed into the collecting groove 13 and the cover 17. Therefore, only the drain is discharged, and the leak of the working steam having effective energy can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a drain discharge device for a steam turbine, and in particular,
The present invention relates to a drain discharge device suitable for improving turbine performance.

[Background of the invention]

In general, in the low pressure stage of a steam turbine and in all stages of a nuclear power turbine, the steam operates in a humid region, so that a considerable amount of water droplets are generated in the operating steam. For this reason, an energy loss called moisture loss generally occurs in the turbine blade passage, which reduces turbine performance and causes water droplets to collide with the rotor blades and generate two lotions, resulting in problems in terms of performance and reliability. Two major problems arise. Moisture loss includes thermodynamic loss due to increased entropy due to the irreversible exchange of latent heat between water droplets and steam when steam condenses into water droplets, and a relatively large loss caused by condensation. Water droplets accumulate on the trailing edge of the ventral side of the stator blade due to inertial force and are eventually released downstream, but the slow coarse water droplets released from the stator blade are accelerated into a high-speed vapor phase during flight. In order to
Acceleration loss occurs when the steam itself consumes energy due to this acceleration, or the accelerated water droplet collides with the back side of the leading edge of the rotor blade, causing the rotor blade to receive a braking force in the opposite direction of rotation. braking loss, etc.

Further, as described above, the second lotion is generated due to water droplets colliding with the rotor blade, and generally, the higher the humidity at the turbine outlet and the higher the circumferential speed of the rotor blade, the more pronounced the problem.

In order to reduce the above moisture loss and erosion, it is necessary in principle to control the generation of water droplets and to remove the generated water droplets as much as possible. Among these methods, there is a method in which a drain catch is provided so that the drain that has adhered to the casing or the diaphragm is not returned to the flow path, and the drain that has accumulated on the drain catch is discharged from the drain discharge hole into the discharge chamber. For example, Utsukai Sho 59-11650
Publication No. 2 discloses a method in which the total opening area of a plurality of drain holes that discharge drain to the outer shaft of the nozzle diaphragm is set to 0.7% from 0.1% of the total opening area of the nozzle outlet. It is effective in controlling leakage in actuating steam operations that have leaking effective energy. This method has the problem that working steam with effective energy is discharged into the exhaust chamber through multiple drain holes, and that the total opening area of the drain holes is small, resulting in a decrease in drain collection efficiency. .

[Purpose of the invention]

An object of the present invention is to reduce energy loss by discharging only the condensate when discharging water droplets accumulated on the drain catch of a steam turbine to the exhaust chamber or outside the system, thereby preventing leakage of working steam that has effective energy. The object of the present invention is to provide a steam turbine device with less.

[Summary of the invention]

According to the present invention, the entrance part of the drainage hole provided at the bottom of the lower half of the drain catch that captures and accumulates the drain of a steam turbine is formed into a substantially hemispherical groove, and the entrance part of the drainage hole is formed into a substantially hemispherical groove, and the inlet portion is substantially aligned with the groove. Therefore, a substantially spherical float that floats on the drain and a cover to prevent the float from floating are placed at the entrance of the drain discharge hole, and when the drain accumulates, the float that roughly matches the hemispherical groove floats. , the drain is discharged from the drain discharge hole, and when the drain is discharged, the float matches the drain discharge hole inlet groove to prevent discharge of working steam.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 7.

FIG. 1 shows a rotor 3, rotor blades 2 fixed to the rotor 3 at intervals in the circumferential direction, a casing 7, a drain catch 1 constituted by an outer diaphragm 4 held by the rotor 3, and an outer diaphragm. 4 and inner diaphragm 5
1 shows a low-pressure stage structure of an axial steam turbine having an annular row of stationary blades 6 spaced apart from each other in the circumferential direction.

FIG. 2 is an enlarged view of the upper half of the first low-pressure final stage, and the drain catch 1 is composed of a casing 7 and an outer diaphragm 4. Drain adhering to the surfaces of the outer diaphragm 4 and the stationary blades 6 is guided to the drain catch 1 as shown by the arrow in the figure by the inertial force of water droplets given by the swirling flow of steam. Outer diaphragm 4
The inner peripheral surface 4' of the casing 7 is formed on the outer peripheral side in the radial direction than the inner peripheral surface 7' of the casing 7, so that the drain can be easily introduced into the drain catch 1. The condensate that is guided to the drain catch 1 by the inertial force of the water droplets given by the swirling flow of steam does not return back into the flow path in the upper half shown in Figure 2 due to the weight of the drain itself and the swirling flow. As shown, the inner circumferential side of the drain catch is provided with a folded portion 8.9 around the entire circumference.

As shown by the arrows in Fig. 3, the drain guided to the drain catch 1 is guided by the swirling flow and the weight of the drain itself, so that the drain is guided to the inner circumferential side of the drain catch 1 on the upper half side 10 and on the inner circumferential side of the drain catch 1 on the lower half side 11. They flow down the outer periphery of the drain catch 1, are collected at the bottom 12 of the lower half of the drain catch, and are discharged into the exhaust chamber 24.

FIG. 4 shows a detailed view of the bottom part 12 of the lower half of the drain catch. The bottom part 12 is provided with an accumulation groove 13 for accumulating drain, and the accumulation groove 13 also has a drain discharge hole 14 communicating with the exhaust chamber. is set up. Further, the inlet portion 15 of the discharge hole 14 is formed in a hemispherical groove, and a spherical float 1 that is slightly smaller than the hemispherical groove of the inlet portion 15 is formed.
6 and a cover 17 for preventing the float 16 from floating. A groove 18 is formed in the cover 17 to accommodate the float 16 when the float 16 floats.

Furthermore, a drain introduction notch 19 and a drain introduction eaves 20 are formed in the collecting groove 13 and the cover 17, respectively, in order to facilitate the capture of drain.

Next, the operating principle of the drain discharge structure of the drain catch bottom 12 configured as described above will be explained.

FIG. 5 shows a state in which no drain is accumulated in the drain accumulation groove 13. At this time, the relationship between the air force P1 in the collecting groove 13 and the pressure pH in the exhaust chamber 24 is P□>Po, and the float 16 is attracted and fixed to the drain discharge hole entrance 15 due to the pressure difference. FIG. 6 shows a sectional view taken along the line ■-■ in this state.
4 is provided. This gap G is the float 16
The suction force when the float is suctioned to the drain discharge hole entrance part 15 is provided for the purpose of alleviating the force, and by adjusting the size of this gap G, the suction force acting on the float can be adjusted. is possible. In addition, a small amount of steam is sucked in through the gap G, which lowers the pressure P of the drain catch 1 and serves to guide the drain to the drain catch 1.

However, this amount of steam is so small that it does not affect the turbine effect. Since the cross-sectional area of the gap G is smaller than the cross-sectional area required for draining the drain, the drain gradually accumulates in the drain collecting groove 13.
The water level rises.

As the water level of the drain rises, the buoyant force F1 acting on the float 16 increases. A suction force F acting on the float 16 is generated by a pressure difference between the pressure Pi in the accumulation groove 13 and the pressure PI in the exhaust chamber. When the relationship between F and buoyancy F1 becomes F>Fo, the float 16 floats, the inlet 15 of the drain discharge hole becomes open, and the drain is discharged into the exhaust chamber.

FIG. 7 shows this state. In addition, since the cross-sectional area of the drain discharge hole 14 is formed to be large enough to discharge the accumulated amount of drain, the drain collecting groove 1
A portion of the drain accumulated in No. 3 is completely discharged, returning to the state shown in FIG. 5, and the above-described operation is repeated.

According to this embodiment, when drain collected in the drain catch is discharged into the exhaust chamber, leakage of working steam having effective energy can be prevented, contributing to improved performance of the steam turbine.

FIG. 8 shows another embodiment of the invention. In this example,
Casing 7 and outer diaphragm 4 held therein
A steam suction port 2 is connected to a drain catch 1 consisting of a
1, and lower than the pressure inside the drain catch 1,
A steam outlet 22 is provided near the inner circumference in the radial direction of the stator blade 6, and a conduit 23 that passes through the outer diaphragm 4 and the inside of the stator blade 6 and connects the steam inlet 21 and the steam outlet 22 is bored. . Pressure P near the steam suction port 21
The relationship between □ and the pressure P2 of the steam outlet 22 is P□〉P2
Therefore, the pressure P1 of the drain catch 1 is lower than the pressure P near the radially outer peripheral side of the stationary blade 6. This pressure difference between P2 and P not only improves the recovery efficiency of the drain that has adhered to the outer diaphragm 4, etc.
It can also be expected that water droplets flying around the inlet of the drain catch 1 can be collected.

Furthermore, when steam is sucked in through the steam suction port 21 provided in the drain catch 1, there is a risk that accumulated condensate may be sucked in along with the steam, but as shown in FIG. By arranging it in the opposite direction, the drain is prevented from entering the guide IW 23.

In addition, by providing the steam outlet 22 at a position on the radially inner circumferential side of the rotor blade 6 where the steam flow velocity exceeds the speed of sound, the condensate sucked in from the steam suction port 21 is also discharged from the steam outlet 22. It is atomized into a spray according to the relational expression.

Here, We is the Univer number, which is usually 20 to 25. Further, σ is the surface tension of water, ρ7 is the density of steam, Uv is the velocity of steam, UL is the velocity of water droplets, and d is the diameter of water droplets.

Since the maximum speed on the radially inner circumferential side of the low-pressure final stage stationary blades of recent large-capacity steam turbines is about 700 m/s, the diameter of condensate water droplets discharged from the steam outlet 22 can be reduced to several microns or less. It is possible to reduce the impact force when colliding with the rotor blade. By atomizing the water droplets, it is possible to reduce the acceleration loss of the water droplets, the braking loss of the rotor blades, and the like.

〔Effect of the invention〕

According to the present invention, only condensate can be discharged into the exhaust chamber, and leakage of working steam having effective energy can be prevented.
This can greatly contribute to improving turbine performance, and can realize a highly reliable turbine with less double lotion and the like.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a steam turbine low pressure stage according to an embodiment of the present invention, FIG. 2 is an enlarged view of the upper half of the final stage in FIG. 1, and FIG.
1 is a sectional view taken along the arrow ■-■, FIG. 4 is a detailed view of the bottom of the lower half of the drain catch in FIG. 3, and FIGS. 8th @ is an explanatory diagram of another embodiment of the present invention, and FIG. 9 is a sectional view taken along the IK-[arrow in FIG. 8. 1... Drain catch, 2... Moving blade, 6... Stationary blade, 1°... Upper half side drain catch, 11... Lower half side drain catch, 13... Drain accumulation groove, 15...
Drain hole entrance groove, 16...Float

Claims (1)

[Claims] 1. In a steam turbine equipped with a drain catch that captures and collects drain generated from saturated steam that has passed through a stationary blade, the drain provided at the bottom of the lower half of the drain catch is discharged. A substantially hemispherical groove is formed at the entrance of the drain discharge hole, and a substantially spherical float that substantially coincides with the groove and floats on the drain, and a cover for preventing this float from floating are provided at the entrance of the drain discharge hole. 1. A drain discharge device for a steam turbine, characterized in that the drain discharge device is disposed in a section. 2. In claim 1, the drain catch is provided with a suction port, and an air outlet is provided on the radially inner peripheral side of the stator blade portion, and the suction port and the air outlet are connected to the stator blade. A drain discharge device for a steam turbine, characterized in that a conduit is bored through the interior of the steam turbine.