JPH04116605U - Steam turbine low pressure exhaust chamber - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce pressure loss and improve pressure recovery in the main stream of exhaust flow. [Structure] A flow guide 22 and a bearing cone 23 define an annular exhaust diffuser 21. In the flow guide 22, a position 2 curved from the axial direction to the radial direction
4 is formed of a porous wall 25, and is connected to the annular exhaust diffuser 21 via the porous wall 25, and an annular bleed chamber 28 having an exhaust port on the side of the alighting compartment is provided.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

The present invention relates to a low pressure exhaust chamber of a steam turbine.

0002

[Conventional technology]

Figures 3 and 4 show the low-pressure exhaust chamber of a conventional steam turbine. In these figures, The exhaust flow 2 from the final stage rotor blade 1 is transmitted through a flow guide 3 and a bearing cone 4. It passes through a defined annular exhaust diffuser 5 and is further surrounded by an inner compartment 6 and an outer compartment 7. The exhaust gas is led to the disembarking room 9 through the space 8, and finally to the condenser (not shown). be done.

0003 In addition, in a compact exhaust chamber in which the axial length H of the low-pressure exhaust chamber is shortened, an annular The exhaust diffuser 5 has a flow path that is sharply curved from the axial direction to the radial direction. The flow guide 3 that defines the annular exhaust diffuser 5 also has a short axial length, and It is greatly curved in the radial direction. In addition, in FIG. 3, the reference numeral 10 indicates a stationary blade. show.

0004

[Problem that the idea aims to solve]

FIG. 5 shows the pressure recovery coefficient Cp of the exhaust chamber as a function of the rotor blade shaft outflow Mach number M. Here, Cp is expressed by the following formula. However, P _B , ρ _B , and V _B represent the rotor blade outlet pressure, density, and outflow velocity, respectively, and P _c represents the condenser inlet pressure. As shown by the solid line A in Fig. 5, Cp tends to decrease as M increases due to the compressibility of the flow, but in the transonic region where M > 0.7, the loss sharply decreases due to the compressibility effect. As a result, pressure recovery is significantly reduced, and Cp<0, resulting in extremely poor exhaust chamber performance.

[0005] The cause of this is that in the annular exhaust diffuser 5, from the exit of the rotor blade 1 in the axial direction, Because the exhaust flow 2 is largely deflected by approximately 90 degrees in the radial direction and the Mach number is high, 3, the flow 11 along the flow guide 3 has a local supersonic region 12. The pressure loss is caused by the separation region 14 caused by the shock wave 13 as a reaction. This is due to an increase. In addition, since the peeling area 14 becomes larger, the annular exhaust The effective flow area of the diffuser 5 becomes narrower, reducing the pressure recovery of the main stream of the exhaust flow 2. do.

[0006] This invention was devised to solve the problems of the conventional technology. It is possible to reduce losses and improve pressure recovery in the mainstream of the exhaust flow. The purpose is to provide a low pressure exhaust chamber for a steam turbine.

[0007]

[Means to solve the problem]

In order to solve the above problems, this invention combines a flow guide and a bearing cone. in a low pressure exhaust chamber of a steam turbine defining an annular exhaust diffuser at A part of the low guide is formed by a wall having a large number of openings, and An annular bleed chamber is installed that communicates with the annular exhaust diffuser and has an exhaust port on the exit compartment side. It's huge.

[0008]

[Effect]

According to the above means, the main flow of the exhaust flow from the final stage rotor blade is connected to the flow guide and the base. It passes through an annular exhaust diffuser defined by a ring cone and then into the interior passenger compartment. It passes through a space surrounded by the outer car compartment, is guided to the alighting compartment, and is finally led to the condenser. It will be done. Additionally, the flow near the flow guide can be circularized through a wall with numerous openings. After being guided to the bleed room, the air is exhausted to the exit compartment from an exhaust port provided on the exit compartment side.

[0009]

【Example】

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2. Figure 1 2 is a vertical cross-sectional view showing the low-pressure exhaust chamber of the steam turbine according to this embodiment, and FIG. 2 is II of FIG. -II line sectional view.

0010 In these figures, an annular exhaust diffuser 21 is connected to a flow guide 22 and a bearing. It is defined by a ring cone 23. In the flow guide 22, whether in the axial direction or A portion downstream of the position 24 that curves in the radial direction is formed of a porous wall 25, and It communicates with the annular exhaust diffuser 21 through the porous wall 25, and exhausts the air to the alighting compartment 26 side. An annular bleed chamber 28 having an opening 27 is provided. In addition, porous wall 2 5 has an aperture ratio of 5 to 20%. In addition, in FIG. 1, the reference numeral 29 indicates a stationary blade; 0 indicates the final stage rotor blade.

[0011] Next, the effect will be explained. First, the main stream 31 of the exhaust flow from the final stage rotor blade 30 is an annular exhaust diffuser defined by a flow guide 22 and a bearing cone 23; After passing through the passenger compartment 21, the vehicle passes through a space 34 surrounded by an inner compartment 32 and an outer compartment 33. , to the alighting compartment 26, and finally to a condenser (not shown).

0012 On the other hand, the flow 35 near the flow guide 22 passes through the perforated wall 25 into the annular bleed chamber 2. After being guided to the exit compartment 26, the air is exhausted from the exhaust port 27 provided on the exit compartment 26 side to the exit compartment 26. .

[0013] Now, when exhausting air from the final stage rotor blade 30 at a high Mach number (M > 0.7), whether it is axially A local supersonic region 36 appears on the flow guide 22 which curves greatly in the radial direction. However, due to the bleed action of the porous wall 25, a shock wave 37 and the accompanying separation area 38 are generated. Since the occurrence of is alleviated and suppressed, pressure loss is reduced. Also, the size of the peeled area 38 In order to reduce the size, the effective flow area of the annular exhaust diffuser 21 is ensured. This is effective in recovering the pressure of the main stream 31.

[0014] In addition, as a modification, instead of the porous wall 25 in the above-mentioned embodiment, a multi-groove wall may be used. Of course, it is also possible to adopt a configuration in which .

[0015]

[Effect of the idea]

As described above, according to the present invention, in the low pressure exhaust chamber of a steam turbine, A part of the low guide is formed by a wall having a large number of openings, and An annular bleed chamber is installed that communicates with the annular exhaust diffuser and has an exhaust port on the exit compartment side. By adopting a beam structure, the shock wave and accompanying peeling are prevented by the bleed action of the wall. Since the occurrence of separation can be suppressed, pressure loss can be reduced.

[0016] Additionally, since the size of the separation area can be reduced, the effective flow path surface of the annular exhaust diffuser can be reduced. This makes it possible to secure a sufficient amount of fuel and contribute to improving the pressure recovery of the main stream of the exhaust flow. It also has this effect.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing a low-pressure exhaust chamber of a steam turbine according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG. 1;

FIG. 3 is a longitudinal cross-sectional view showing a conventional steam turbine low-pressure exhaust chamber.

FIG. 4 is a sectional view taken along the line IV-IV in FIG. 3;

FIG. 5 is a diagram showing the relationship between Mach number and pressure recovery coefficient.

[Explanation of symbols]

21 Annular exhaust diffuser 22 Flow guide 23 Bearing cone 25 Porous wall 26 Getting off room side 27 Exhaust port 28 Annular bleed chamber

Claims (1)

[Scope of utility model registration request] Claims: 1. A low-pressure exhaust chamber of a steam turbine in which a flow guide and a bearing cone define an annular exhaust diffuser, wherein a portion of the flow guide is formed by a wall having a plurality of openings; A low-pressure exhaust chamber for a steam turbine, characterized in that an annular bleed chamber is connected to an annular exhaust diffuser and has an exhaust port on the side of an alighting chamber.