JPH08303206A - Axial-flow turbomachinery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid exergy loss in an extraction chamber by providing a diffuser extending almost radially, inside an extraction chamber, and setting the outflow radius of the diffuser within a specific range. SOLUTION: An extraction chamber 7 is provided inside with a diffuser wall 20 directly behind an extraction opening 6, continuously with it. The diffuser wall 26 along with an outflow side extraction chamber wall 9 forms a diffuser 23 provided with a diffuser outlet 26. The ratio R2/R1 of an outlet radius R2 to an inlet radius R1 is to be larger than 1.3. The ratio of running length L to extraction width H is at least 10. A deflection grid 24 is additionally fitted to the diffuser wall 20 at the diffuser outlet of the diffuser 23. Marked exergy loss can be avoided by thus incorporating the diffuser 23 in the extraction chamber 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an axial flow turbomachine provided with at least one extraction chamber in a casing, and a part of a working medium used for operating the turbomachine in the extraction chamber. Of the type that is discharged through the extraction opening.

[0002]

2. Description of the Related Art Extraction chambers of this kind for axial-flow turbomachines are known. A turbomachine mainly consists of a rotor having rotating blades and a casing containing guide blades.
The rows of rotary vanes are arranged alternately with the rows of guide vanes, respectively. In order to extract the working medium from the turbomachine, the casing is provided with extraction openings between the guide vane rows.
The working medium passes through this extraction opening into the annular extraction chamber arranged in the casing. The working medium is then discharged from this extraction chamber and used subsequently. The kinetic energy is practically completely dissipated when the working medium has a high kinetic energy and a swirling flow into the extraction chamber, which is significantly expanded relative to the extraction opening.
This causes a significant exergy loss. For flows with significant swirl, good thermal conductivity results in another exergy loss due to heat flow. According to Swiss Pat. No. 6,613,19 A5, at least one wall of the extraction opening is chamfered so that the extraction opening is formed as a diffuser. However, the radius ratio of the outlet radius to the outlet radius of this diffuser is small, and as a result, the significant swirl component of the vortex is reduced only insufficiently. As a result, the recovery rate is extremely low. The recovery rate is represented by a numerical value between 0 (zero) and 1, and this numerical value indicates the ratio of kinetic energy recovered. In addition, the non-uniformity of the feed flow into the extraction opening
It causes a complete separation of the flow in the short diffuser, which reduces the recovery rate to zero.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to avoid exergy loss in the extraction chamber in the axial flow turbomachine of the above-mentioned type having the extraction chamber in the casing.

[0004]

According to the present invention, the above-mentioned problems are solved by providing a diffuser extending in a substantially radial direction at the extraction opening inside the extraction chamber, and
The solution is that the radius ratio of the outflow radius to the inlet radius of the diffuser is greater than 1.3 and the ratio of the running length to the extraction width of the diffuser is at least 10.

[0005]

Among other advantages of the present invention, the selected radial extension and long running length of the diffuser ensure that the vertical and tangential components of the flow velocity are reduced. That is. Therefore, the diffuser is stable, in other words insensitive to the inflow conditions at the extraction aperture.

Particularly when the radius ratio is small, it is effective to incorporate a deflection grating in front of the diffuser outlet. This completely eliminates the tangential velocity, which gives the maximum possible recovery.

It is particularly effective if the extraction chamber wall on the outflow side is used as the diffuser wall. This is because in this case the heat flow through the chamber wall is minimal. Moreover, this minimizes configuration costs. That is because only one diffuser wall needs to be made.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will now be described with reference to the drawings based on a low pressure double flow steam turbine.

Only those elements that are important to an understanding of the invention are shown in the drawings. For example, the mechanism for the supply and discharge of steam and the bearings are not shown. The flow direction of the working medium is indicated by arrows.

According to FIG. 1, a rotor 1 consisting of a shaft disk joined together by welding is provided with rotating blades 2, which are arranged in rows 10, 11, 1.
2 and 13 are arranged. The rotor 1 is surrounded by a casing 3, which is divided in the axial direction and is connected via a flange (not shown). Guide vanes 4 are arranged in the casing 3 in a plurality of rows 14, 15, 16, 17 corresponding to the rotary vanes 2.

The steam flow path leads to a torus-shaped supply flow passage 5 in the casing 3 via a supply steam conduit (not shown). The torus-shaped feed flow passage helps to better direct the steam to both streams of the steam turbine. The steam is discharged after passing energy to the rotor 1 via the rotary vanes 2.

The extraction opening 6 is located between the guide blade row 15 and the guide blade row 16 and between the guide blade row 16 and the guide blade row 17. The steam is discharged into the substantially torus-shaped extraction chamber 7 extending around the casing 3 through the annularly extending substantially slit-shaped extraction opening. The steam having the specific heat and the pressure corresponding to each position of the extraction opening 6 is taken out. This extraction vapor (bleed air) is collected in the extraction chamber 7 and then discharged via an extraction conduit (not shown). This extracted steam is used, for example, in a steam circuit for heating the feed water.

As can be seen from FIG. 2, a diffuser wall 20 is provided in the extraction chamber 7 immediately following the extraction opening 6, which diffuser wall together with the extraction chamber wall 9 on the outflow side, A diffuser 23 with a diffuser outlet 26 is formed. The temperature of the extraction chamber wall 9 on the outflow side and the temperature of the base of the guide vanes 4 correspond approximately to the temperature of the extraction steam. For fixing the diffuser wall 20, an annular guide groove 21 is provided at the extraction opening 6 and a guide groove 22 is provided at the rib 8. A plurality of ribs 8 are arranged evenly around the casing 3.

The diffuser wall 20 is manufactured from two parts corresponding to the two-part casing 3 by metal forming, for example, from a thin plate. As a result, the diffuser wall 20 is fitted in the guide grooves 21, 22 in the circumferential direction.

The diffuser 23 has a length ratio L / H of the running length L to the extraction width H at the extraction opening 6.
And the radius ratio of the exit radius R2 to the entrance radius R1 R2 /
Area ratio A of R1 and the outlet area A2 at the diffuser outlet 26 to the inlet area A1 at the extraction opening 6
2 / A1. The ratio of the running length L to the extraction width H is preferably at least 10 (L / H> 10) in order to significantly reduce the vertical and tangential components of the incoming flow velocity. In order to obtain the highest possible recovery, the ratio of running length L to extraction width H is chosen to be greater than 15 in FIG. The diffuser 23 extends widely in the radial direction, and as a result,
The radius ratio R2 / R1 is> 1.3. This reduces the outlet tangential velocity of the diffuser 23 flow at the diffuser outlet 26 as compared to the inlet tangential velocity at the extraction opening 6. It goes without saying that the ratio of the outlet area A2 to the inlet area A1 is selected in accordance with the generally known conditions for a diffuser which does not cause separation. When the ratio of the running length to the extraction width H is at least 10, for example, the inlet area A1
The ratio of the exit area A2 to A is approximately 3 or greater. For example, when the diffuser wall 20 is equidistant from the extraction chamber wall 9 and the required area ratio A2 / A1 cannot be obtained, the guide groove 22 is spaced farther or closer from the extraction chamber wall 9. It should be installed in the place. This gives any ratio of exit area to entrance area.

In addition to the diffuser wall 20 at the diffuser outlet of the diffuser 23, the deflection grating 2
4 can be attached. This deflection grating reduces the residual tangential velocity. This further improves pressure recovery and reduces heat transfer in the extraction chamber.

FIG. 3 shows a deflection grating 24 consisting of vanes 25. The shape of the blade is merely an example. The blade 25 can be manufactured from a thin plate, for example. These blades are fixed to the diffuser wall 20, for example by welding or riveting, prior to mounting the diffuser wall 20 in the extraction chamber 7 in the circumferential direction.

By incorporating a diffuser in the extraction chamber 7, a significant exergy loss is avoided. Next, this will be explained by approximation. The diffuser 23 described above
For, the following conditions for the incoming steam apply:
That is, inflow pressure ≅ to = 250 mbar inflow enthalpy ≅ to = 2600 kJ / kg inflow speed ≅ to = 250 m / s This results in an energy loss of 180 kW per extraction chamber without the diffuser 23. This is 1M for a low pressure double flow steam turbine with three extraction chambers 7 each.
Corresponds to W's exergy loss. Further diffuser 2
According to 3, another exergy loss that is not shown quantitatively,
Avoidance is based on eddy-free flow and consequent reduced heat transfer.

Of course, the invention is not limited to the illustrated embodiment. The integration of the diffuser into the extraction chamber is applicable to any axial flow turbomachine that produces high flow energy in the extraction chamber. The diffuser may be formed by two diffuser walls without the aid of the extraction chamber wall. Furthermore, it goes without saying that the fixing of the diffuser wall can also be carried out by another arbitrary means. The configuration (deflection angle, chord length and split ratio) and position of the deflection grating are determined by the respective flow downstream of the diffuser outlet.

[Brief description of drawings]

1 is a partial vertical cross-sectional view of a steam turbine according to the present invention.

FIG. 2 is a detailed view of a portion surrounded by a circle indicated by reference numeral II in FIG.

FIG. 3 is a partial development view of a deflection grating of a diffuser.

[Explanation of symbols]

1 rotor, 2 rotating blades, 3 casing, 4
Guide vanes, 5 supply flow passages, 6 extraction chambers, 8
Rib, 9 Outflow side extraction chamber wall, 10, 1
1, 12, 13 Row of rotating blades, 14, 15, 16,
17 Row of guide vanes, 20 Diffuser wall, 21
Guide groove on the extraction opening side, 22 Guide groove on the rib side, 2
3 diffuser, 24 deflection grating, 25 blades,
26 Diffuser outlet, A1 inlet area, A2
Exit area, L running length, H extraction width,
R1 entrance radius, R2 exit radius

Claims (7)

[Claims] 1. An axial flow turbomachine with at least one extraction chamber (7) in a casing (3) into which a part of the working medium used for operating the turbomachine. Of the type in which the gas is discharged through the extraction opening (6), the diffuser (2) extending substantially radially in the extraction chamber (7) at the extraction opening (6).
3) is provided, and the radius ratio (R2 / R1) of the outlet radius (R2) to the inlet radius (R1) of the diffuser (23) is larger than 1.3 [R2 / R1> 1.
3] and the ratio of the running length (L) to the extraction width (H) of the diffuser (23) is at least 10 [L /
H ≧ 10], an axial flow turbomachine. 2. The axial turbomachine according to claim 1, wherein a deflection grating (24) is arranged in the diffuser (23) at the diffuser outlet (26). 3. The axial turbomachine according to claim 1, wherein the diffuser (23) is formed by an extraction chamber wall (9) of the extraction chamber (7) and a diffuser wall (20). 4. The diffuser wall (20) has an extraction chamber (7).
The axial flow turbomachine according to claim 3, wherein the turbomachine is inserted therein. 5. The diffuser wall (23) has a guide groove (2).
Axial-flow turbomachine according to claim 4, which is fixed in the extraction chamber (7) via 1, 22). 6. Axial flow turbomachine according to claim 3, wherein the extraction chamber wall (9) is the extraction chamber wall on the outflow side of the turbine. 7. A deflection grating (24) is provided on the diffuser wall (2).
The axial turbomachine according to claim 2, wherein the turbomachine is arranged at 0).