DE102008062078B4 - Entry level for a steam turbine - Google Patents

Abstract

An inlet stage for a steam turbine, with a nozzle ring (2, 3, 4) for acting on an impeller with steam, said nozzle ring having a plurality of circumferentially juxtaposed nozzles (2.1, 2.2, 2.3, 2.4, 3.1, 3.2, 3.3, 3.4) , which are arranged in a nozzle box, characterized in that the nozzle ring is formed such that the sizes (t2.3, t2.4) and / or distances of the nozzles of the nozzle ring (2; 4) to each other over its circumference so mutually vary in that a steam mass flow density through the nozzles is substantially constant over its circumference, the distances of the nozzles of the nozzle ring (2; 4) from each other increasing towards a vapor entry into the nozzle ring.

Description

The invention relates to an inlet stage, in particular a control stage, for a steam turbine, with a nozzle ring for impinging an impeller with steam, wherein the nozzle ring has a plurality of circumferentially juxtaposed nozzles which are arranged in a nozzle box.

For example, from the WO 2006/024 597 A1 a steam turbine with multiple inlet stages according to the preamble of claim 1 is known. In typically for control stages of such steam turbines, the nozzle ring on several sub-rings or nozzle segments, which can be selectively controlled by valves to control the turbine by shutting off one or more sub-rings and thus selectively operate in the partial load range.

The in the WO 2006/024 597 A1 Only schematically indicated partial rings each have a nozzle box in which a plurality of nozzles are arranged in the circumferential direction next to each other. 1 shows a left upper nozzle box 1 with several nozzles or nozzle sections 1.1 to 1.4 as known from in-house practice. In this steam flows substantially vertically, is guided through the inner contour of the nozzle box to the individual nozzles and exits through this in the axial direction to apply a control wheel behind the nozzle ring. By selective blocking of each of the four distributed over the circumference of the nozzle boxes, the control wheel is acted upon in quadrants.

The hydraulic diameter in the circumferential direction is, as in the WO 2006/024 597 A1 and 1 to detect, in the areas outside of the steam inlet constant. The size and spacing of the individual nozzles to each other are constant over the circumference.

In particular due to friction and deflection losses as well as dead zones and backflow of the vapor in such conventional nozzle rings, a mass flow density which is highly inhomogeneous over the circumference sets in. For example, in the in 1 shown partial ring as well as in the nozzle segments of WO 2006/024 597 A1 less vapor to those nozzles which are furthest away from the steam inlet, which adversely results in non-uniform loading of the nozzles and the impeller disposed behind and lowers the efficiency of the steam turbine.

The US 5 823 742 A also discloses an inlet stage for a steam turbine according to the preamble of claim 1.

From the DE 19 10 200 A Further prior art is known.

Object of the present invention is therefore to improve a steam turbine.

To solve this problem, an entry stage according to the preamble of claim 1 is further developed by the characterizing features.

Claim 10 provides protection for a steam turbine with at least one such inlet stage.

The subclaims relate to advantageous developments.

An inlet stage for a steam turbine has a one-part or multi-part nozzle ring for acting on an impeller arranged behind it in the flow direction with a plurality of circumferentially juxtaposed nozzles, which are arranged in a nozzle box. The individual nozzles may likewise be integrally formed with the nozzle box or may be detachably or non-detachably fastened thereto and in particular be defined by guide vanes.

According to the invention, the nozzle ring is designed according to plan such that the sizes and / or distances of the nozzles of the nozzle ring vary in such a way vary over its circumference that a steam mass flow density through the nozzles is substantially constant over its circumference, wherein the distances of the nozzles of the nozzle ring to each other increase in steam inlet into the nozzle ring. As a result, the efficiency of the steam turbine can be improved and a load of impeller and nozzles can be distributed more uniformly over the circumference.

The mass flow density depends on the density of the steam with which the nozzle ring is charged, for example, by a steam boiler, its flow velocity, in particular its meridian component, and the distribution and formation of the individual nozzles. Accordingly, the person skilled in the art can realize the constant steam mass flow density according to the invention in particular by appropriate design of one or more of these parameters.

In particular, the sizes, ie the hydraulic diameters of the nozzles of the nozzle ring in the meridian direction, can decrease toward a vapor entry into the nozzle ring, preferably monotonically, in particular strictly monotonously. As a rule, the highest vapor mass flow density in the nozzle ring is present in the vicinity of this vapor inlet, whereas due to the flow losses mentioned at the beginning, this decreases towards the nozzles which are more remote from the vapor inlet. This can be compensated be that these remoter nozzles have a larger hydraulic diameter, so that results in loss-related lower vapor velocity multiplied by the larger hydraulic diameter again the same vapor mass flow density as a product of the passage area and flow rate normal to this.

The distances between the nozzles of the nozzle ring to each other to a steam inlet into the nozzle ring can monotonically, in particular strictly monotonously increase. As a result, there are more nozzles in areas in which lower steam flow rates are due to the loss, more nozzles can pass through them at the lower speed and thus in turn can have substantially the same mass flow density over the circumference.

By appropriate variation of the distances of the nozzle sections to one another, the outflow from the nozzle ring and thus the flow velocity of the vapor in the nozzle ring over its circumference can advantageously be set substantially constant.

Additionally or alternatively, an inner contour of the nozzle box may be formed such that a steam mass flow density is substantially constant over its circumference.

For example, a hydraulic inner diameter of the nozzle box in the circumferential direction, in particular substantially over its entire circumference, decrease from a Dampfeinritt, preferably monotonically, in particular strictly monotonous. As (strictly) monotonically decreasing, a variation of a parameter, for example of nozzle size, distance or diameter of the inner contour, is designated in a customary manner in which the parameter is always smaller (strictly monotonous) or smaller or the same at a rearward position in the circumferential direction (monotonic) is as at a circumferentially forward position. In particular, in such a nozzle box with an inner contour tapering towards the nozzles entering the steam inlet, advantageously, the meridional velocity of the steam in the nozzle ring can be set substantially constant over its circumference.

An inlet stage according to the invention can be designed, in particular, as a control stage whose nozzle ring has at least two, in particular at least four, selectively controllable partial rings. Then preferably at least one partial ring, preferably several, in particular all partial rings are formed such that a steam mass flow density is substantially constant over the circumference thereof.

• 1 einen linken oberen Teilring einer Regelstufe nach betriebsinternen Praxis im Querschnitt;
• 2 einen linken unteren Teilring einer Regelstufe nach einer ersten Ausführung der vorliegenden Erfindung in 1 entsprechender Darstellung;
• 3 einen rechten oberen Teilring einer Regelstufe nach einer zweiten Ausführung der vorliegenden Erfindung in 1 entsprechender Darstellung; und
• 4 einen rechten unteren Teilring einer Regelstufe nach einer dritten Ausführung der vorliegenden Erfindung in 1 entsprechender Darstellung.

Further advantages and features emerge from the subclaims and the exemplary embodiments. This shows, partially schematized:

• 1 a left upper part ring of a control stage according to internal practice in cross section;
• 2 a left lower sub-ring of a control stage according to a first embodiment of the present invention in 1 corresponding representation;
• 3 a right upper part ring of a control stage according to a second embodiment of the present invention in 1 corresponding representation; and
• 4 a right lower sub-ring of a control stage according to a third embodiment of the present invention in 1 corresponding representation.

The figures show as a whole the arrangement of four partial rings or nozzle boxes 1 to 4 along the circumference, so that by controlled blocking of individual partial rings by (not shown) valves at the respective steam inlet into the nozzle box, the steam turbine can be operated controlled in part-load operation. As a control is referred to a pure control without feedback of measured values. In this case, the individual figures show partial rings of different designs for a better representation together, wherein in each embodiment the other three partial rings are to be considered replaced by the partial ring of the respective embodiment.

1 shows the initially explained upper left part ring 1 a control level, as known from in-house practice. The control stage has, as stated above, four identical partial rings, so that by replacing the 2 to 4 by appropriately mirrored 1 a plan view of the entire control stage in the flow direction results.

In 1 are four nozzles or nozzle sections 1.1 to 1.4 indicated with t1.3 = t1.4 the size of the corresponding nozzle sections in the circumferential direction. With a1.1 = a1.2, the hydraulic flow diameter in the circumferential direction is designated at two different locations outside the steam inlet.

It can be seen that the size of all nozzle sections in the circumferential direction and the hydraulic flow diameter outside the steam inlet in the known partial ring 1 are constant. Through flow losses, a highly inhomogeneous distribution of the flow velocities and thus the mass flow density sets, which designates the amount of steam that passes through the individual nozzles per unit time.

Therefore, in a first embodiment of the present invention vary in the four identical partial rings 2 of which a lower left in 2 is shown, the nozzle sizes. As in 2 As can be seen, the nozzle sizes in the circumferential direction, starting from the steam inlet towards the nozzles which are farther away from it, increase strictly monotonically, so that in particular t2.4> 12.3 applies. A larger nozzle can also be realized in that in the region of this nozzle more equal sized individual nozzles are arranged as in another area, so that the distances of such individual nozzles of the nozzle ring to each other increase toward the Dampfeinritt. As in the more remote from the steam inlet areas of the partial ring 2 more or larger nozzles are arranged, the loss-related lower flow velocity is compensated in these edge regions, so that essentially sets a constant steam mass flow over the circumference.

In a second embodiment of the present invention is an inner contour of the nozzle box of the four identical partial rings 3 of which a right upper in 3 is designed such that a steam mass flow density is substantially constant over its circumference. For this purpose, the hydraulic inner diameter of the nozzle box decreases in the circumferential direction over its entire circumference from the steam inlet from strictly monotonous, so that in particular a3.1 <a3.2 applies. As a result, the steam is in the more remote from the vapor inlet areas of the partial ring 3 accelerated, so that the loss-related reduction of the flow velocity is compensated in these edge regions and sets a substantially constant mass flow of vapor over the circumference.

In a third embodiment of the present invention, the first and second embodiments are combined so that in the four identical partial rings 4 of which a right lower in 4 is shown, the nozzle sizes increase in the circumferential direction, starting from the steam inlet to the more distant from this nozzle, the hydraulic inner diameter of the nozzle box, however, decreases.

LIST OF REFERENCE NUMBERS

1

partial ring

1.1 ... 1.4

jet

2

partial ring

2.1 ... 2.4

jet

3

partial ring

3.1 ... 3.4

jet

4

partial ring

a1.1, a1.2,

a3.1, a3.2

hydraulic inner diameter

t1.3, t1.4,

t3.4, t3.4

nozzle size

Claims (10)

An inlet stage for a steam turbine, with a nozzle ring (2, 3, 4) for acting on an impeller with steam, said nozzle ring having a plurality of circumferentially juxtaposed nozzles (2.1, 2.2, 2.3, 2.4, 3.1, 3.2, 3.3, 3.4) , which are arranged in a nozzle box, characterized in that the nozzle ring is formed such that the sizes (t2.3, t2.4) and / or distances of the nozzles of the nozzle ring (2; 4) to each other over its circumference so mutually vary in that a steam mass flow density through the nozzles is substantially constant over its circumference, the distances of the nozzles of the nozzle ring (2; 4) from each other increasing towards a vapor entry into the nozzle ring. Entry level after Claim 1 , characterized in that the sizes (t2.3, t2.4) of the nozzles of the nozzle ring (2, 4) decrease towards a steam inlet into the nozzle ring. Entry level after Claim 1 or 2 , characterized in that the flow velocity of the vapor in the nozzle ring is substantially constant over its circumference. Entry step according to one of the preceding claims, characterized in that an inner contour of the nozzle box is formed such that a steam mass flow density is substantially constant over its circumference. Entry level after Claim 4 , characterized in that a hydraulic inner diameter (a3.1, a3.2) of the nozzle box decreases in the circumferential direction of a Dampfeinritt from. Entry level after Claim 5 , characterized in that the hydraulic inner diameter (a3.1, a3.2) of the nozzle box decreases substantially over its entire circumference from the vapor inlet. Entry step according to one of the preceding claims, characterized in that the meridional velocity of the vapor in the nozzle ring is substantially constant over its circumference. Entry level after one of Claims 1 to 7 , characterized in that it is a control stage, and that the nozzle ring at least two selectively controllable partial rings (2; 3; 4), wherein at least one partial ring is formed such that a steam mass flow density is substantially constant over its circumference. Entry level after Claim 8 , characterized in that the nozzle ring has at least four selectively controllable partial rings (2; 3; 4). Steam turbine with an inlet stage, which has an impeller and a nozzle ring for acting on the control wheel, characterized in that the inlet stage according to one of Claims 1 - 9 is formed such that a steam mass flow density is substantially constant over its circumference.

Images