JP2005113787A - Steam turbine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a steam turbine improving drain collection efficiency. <P>SOLUTION: A moisture separation duct 7 and a cover 8 are provided on a diaphragm inner wall surface 5 of a steam turbine and a shape thereof is formed in a recessed shape. An inlet shape of a moisture separation duct 7 is tilted and a turn part 13 is provided on a duct side on an opposite side thereof. A part of a duct in a diaphragm lower half is connected to a low pressure part such as a condenser. With the structure mentioned above, moisture 9 such as liquid film transmitting along an outer wheel inner wall surface 5 can be separated and discharged. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a steam turbine provided with a moisture separation structure for separating moisture generated inside a turbine.

  As a conventional technique related to a moisture separation structure of a steam turbine, there is a technique described in JP-A-3-37303.

  In JP-A-61-265305 described above, an annular groove for introducing a drain is provided on the inner peripheral surface of the nozzle diaphragm outer ring, and a drain discharge hole is formed on the outer peripheral surface side of the nozzle diaphragm outer ring from the bottom of the annular groove. In the drilled steam turbine, it is described that a drain return preventing portion having a bowl-shaped cross section is formed on the inner peripheral surface portion of the annular groove.

  JP-A-3-37303 discloses an inner peripheral surface of a nozzle diaphragm outer ring having an opening toward the downstream side at the upstream end of the nozzle diaphragm outer ring separately from the nozzle blade annular groove having a drain discharge hole. The steam turbine provided with the drain collection part which collect | recovers the drain which flows into the said upstream edge part along is described.

JP 61-265305 A (2nd to 4th pages, Fig. 1) JP-A-3-37303 (pages 3 to 6, FIG. 1)

  In low-pressure stages of nuclear turbines and steam turbines, as the steam performs work, the moisture that expands and condenses adheres to the inner wall surface of the stationary blade and diaphragm outer ring, flows as a water film, and after the stationary blade It is torn away from the edge and scattered, causing erosion of the rotor blades and loss of moisture due to moisture.

  However, in the technique described in Japanese Patent Laid-Open No. 61-265305 and Japanese Patent Laid-Open No. 3-37303 described above, the opening for collecting the drain formed in the diaphragm outer ring is formed in the radial direction or downstream of the steam turbine. Since it was opened toward the side, there was a possibility that drain would flow down without entering the opening due to the influence of the steam flow.

  An object of the present invention is to provide a steam turbine with improved drain recovery efficiency.

  In order to achieve the above object, the present invention improves the recovery efficiency by forming the drain recovery hole of the diaphragm outer ring so as to open toward the upstream side of the steam.

  According to the present invention, it is possible to effectively separate and discharge moisture such as a liquid film transmitted through the inner surface of the diaphragm outer ring, and there is an effect that it is possible to provide a steam turbine with improved drain recovery efficiency.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a cross-sectional view of a stationary blade diaphragm used in a steam turbine, FIG. 2 is an enlarged view of a moisture separation duct, and FIG. 3 is a cross-sectional view showing an upper half and a lower half of the diaphragm. Shows a perspective view of the diaphragm.

  As shown in FIG. 1, the diaphragm 4 includes an outer ring 2 that holds the stationary blade 1 and an inner ring 3 that is provided on the root side of the stationary blade 1. The steam flow path is formed by an upper half portion of the diaphragm and a lower half portion of the diaphragm in which the radial ends of the plurality of stationary blades are fixed by the outer ring 2 and the inner ring 3, respectively. In this embodiment, on the upstream side of the stationary blade 1, a moisture separation duct 7 is provided at the tip of the moisture guiding portion 6 that leads from the inner wall surface 5 of the outer ring 2 to the inside of the outer ring. A cover 8 is installed so as to cover it.

Further, as shown in FIG. 2, the radial height h1 of the inlet tip of the cover 8 is made smaller than the height h2 of the inner surface of the outer ring at the same cross-sectional position in the axial direction. It is possible to separate moisture 9 such as a liquid film flowing over the steam stream 10 for driving the turbine. The moisture guiding section 6, the moisture separating duct 7 and the cover 8 are installed over the entire circumference of the diaphragm 4, and the diaphragm upper half 4a and the lower half 4b are connected at the horizontal plane position at the center of the rotor 11. Therefore, the moisture that has flowed into the moisture separation duct 7 in the upper half portion 4a of the diaphragm flows down to the lower half portion 4b of the diaphragm through the duct.

  Next, the moisture separation state will be described in more detail with reference to FIG. 5A is a detailed view of the moisture separation duct of the upper half portion 4a of the diaphragm, and FIG. 5B is a detailed view of the moisture separation duct of the lower half portion 4b of the diaphragm.

  The moisture 9 trapped by the moisture separation duct 7 in the upper half portion 4a of the diaphragm mainly flows through the duct cover 8 and flows down to the lower half portion 4b of the diaphragm. The lower half portion 4b of the diaphragm is provided with a moisture discharge hole 12 for discharging moisture 9 at the lowermost part or in the vicinity thereof, and the moisture flowing down from the upper half of the diaphragm to the moisture separation duct of the lower half, and The moisture trapped by the moisture separation duct in the lower half of the diaphragm is mainly transmitted through the duct portion and discharged from the discharge hole 12 to a low pressure portion such as a condenser (not shown).

  According to such a configuration of the present embodiment, moisture 9 such as a liquid film transmitted through the outer ring inner wall surface 5 can be separated and discharged over the entire circumference of the diaphragm, so that there is no scattering of moisture downstream of the diaphragm. The occurrence of erosion on the rotor blade can be prevented.

  Also, the moisture discharge holes 12 formed in the lower diaphragm half 4b are provided with one to two holes in the vicinity of the lowermost part of the lower diaphragm half as compared with the situation where a large number of holes are installed between the stationary blades of the conventional structure. Therefore, the absolute number is extremely small, and the steam flow for driving the turbine that leaks together with moisture can be reduced, which contributes to the improvement of turbine efficiency. Furthermore, if a drain trap is installed between the moisture discharge hole 12 and the low pressure part, the outflow of the steam flow for driving the turbine can be completely prevented, so that the efficiency improvement by moisture separation becomes more remarkable.

  6 is a cross-sectional view of the AA cross section of FIG. 3 as viewed from the turbine inlet side. As shown in the drawing, the diameter of the flow path of the duct 71 around the moisture discharge hole 12 located at the bottom of the lower half portion 4 b of the diaphragm is formed larger than the diameter of the other moisture separation ducts 7. In this way, by increasing the volume of the moisture separation duct 71 around the lowermost portion of the lower half portion 4b of the diaphragm, even if a large amount of moisture flows down, excess moisture can be absorbed by this portion. Moisture does not overflow into the flow path.

  In addition, by installing the above-described drain trap (not shown) downstream of the moisture discharge hole 12, the moisture 9 is discharged to a predetermined amount in the duct 71 around the lowermost portion having a large volume. The moisture 9 is always stored at a constant level, and the leaking steam flow for driving the turbine can be completely eliminated. As a result, the turbine efficiency can be further improved (note: the drain trap is provided between the discharge hole 12 and the low pressure part).

  Next, the shape of the moisture separation duct will be described. As shown in FIGS. 7 to 9, the opening surface on the steam flow path side that collects drain in the moisture separation duct 7 opens toward the steam upstream side. As shown in FIG. 7, the shape of the moisture separation duct must be such that moisture such as water droplets or liquid film that has flowed along the outer ring inner wall surface 5 can easily flow in, and the trapped moisture does not overflow. . Therefore, as shown in FIG. 8, it is desirable that the moisture separation duct 7 has a concave shape toward the outer side of the outer ring to increase the capture capacity. Furthermore, as a drain outflow prevention member, it is possible to prevent moisture that has entered the duct from flowing out of the duct by forming a shape with a return 13 attached to the cover inlet as shown in FIG. The shape shown in FIGS. 8 and 9 has the effect of securing the capacity and preventing the outflow of moisture to the outside of the duct when applied to either the upper half or the lower half of the diaphragm.

  Next, the duct structure shown in FIGS. 10, 11, and 12 will be described. In the illustrated example, the moisture is collected in the moisture separation duct 7 via the moisture guiding portion 6. And it has the moisture guidance part 6 which guides a drain to the moisture separation duct 7, and opens the opening surface by the side of the steam flow path of a moisture guidance part toward the steam upstream side. Further, the moisture guiding portion 6 sandwiched between the moisture separation duct 7 and the inlet portion of the cover 8 is moved from the upstream side to the downstream side so that moisture flowing along the inner ring inner wall surface can easily flow in the direction toward the outer ring outer wall surface. The shape is inclined toward the front. As a result, moisture transmitted through the inner surface 5 of the outer ring can be accurately guided to the moisture separation duct 7 via the moisture guide 6. In addition to the configuration of FIG. 10, FIG. 11 shows the moisture separation duct 7 having a concave shape toward the outer side of the outer ring to increase the trapping capacity. FIG. 12 shows the moisture separation in addition to the configuration of FIG. In this structure, a return 13 is provided at the inlet of the duct 7 (the outlet of the moisture guide 6).

  Furthermore, in addition to the shapes shown in FIGS. 10 to 12, in FIGS. 13, 14 and 15, the inlet shape 81 on the outer surface of the cover forming the moisture separation duct is changed from the upstream side so as not to block the steam flow. The shape is inclined toward the downstream side. As a result, it is possible to guide moisture to the moisture separation duct, and to guide the turbine to the stationary blade while suppressing disturbance of the steam flow for driving the turbine.

  The moisture separation duct and the cover shape as described above are not only installed on the upstream side of the stationary blade of the diaphragm outer ring, but also installed on the downstream side of the stationary blade as shown in FIG. Moisture flowing along the inner ring wall surface can also be separated.

  Next, a method for attaching the cover forming the moisture separation duct 7 will be described with reference to FIG. The outer ring 2 of the diaphragm to which the cover 8 is attached is provided with a concave groove 14 that is inclined so as to become wider toward the outside of the outer ring. On the other hand, the cover 8 attached to the outer ring is provided with a protrusion 15 having a convex shape that can be fitted into the concave groove 14 in the opposite direction. The cover 8 formed as described above is attached so as to be inserted and fixed from the end face of the diaphragm. The cover 8 that forms the moisture separation duct 7 by being attached to the outer ring 2 functions as a receiving portion for the drain collected in the moisture separation duct 7.

  FIG. 18 shows a structural example in which the cover 8 is joined to the outer ring 2 by welding 16. FIG. 19 shows a structure in which the cover 8 is fixed with screws 17 from the outer side of the outer ring. In any of the attachment methods, the outer surface of the cover forming the moisture separation duct 7 is flush with the inner surface of the outer ring on the downstream side of the moisture separation duct.

BRIEF DESCRIPTION OF THE DRAWINGS Sectional drawing which shows the moisture separation structure of the steam turbine which is one Example of this invention. The enlarged view of a moisture separation duct part. Sectional drawing which shows the whole structure of this invention. The perspective view which shows the whole structure of this invention. Detailed view of moisture separation structure in upper half and lower half of diaphragm. Sectional view of the duct as seen from the turbine inlet side The fragmentary sectional view which shows a duct shape. The fragmentary sectional view which shows a duct shape. The fragmentary sectional view which shows a duct shape. The fragmentary sectional view which shows a duct entrance shape. The fragmentary sectional view which shows a duct entrance shape. The fragmentary sectional view which shows a duct entrance shape. The fragmentary sectional view which shows a cover shape. The fragmentary sectional view which shows a cover shape. The fragmentary sectional view which shows a cover shape. Sectional drawing which installed the moisture separation duct in the downstream of a stationary blade. Explanatory drawing of the cover attachment structure by fitting. Explanatory drawing of the cover attachment structure by welding. Explanatory drawing of the cover attachment structure by screwing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Stator blade, 2 ... Outer ring, 3 ... Inner ring, 4 ... Diaphragm, 5 ... Outer ring inner wall surface, 6 ... Moisture induction part, 7 ... Moisture separation duct, 8 ... Cover, 9 ... Moisture, 10 ... Steam flow , 11 ... rotor, 12 ... moisture discharge hole, 13 ... return, 14 ... groove, 15 ... projection, 16 ... welding, 17 ... screw.

Claims (10)

  In a steam turbine in which a radial end portion of a stationary blade is fixed to a diaphragm outer ring, an opening for collecting drain is provided on the inner wall surface of the diaphragm outer ring, and the opening surface of the opening is opened toward the steam upstream side. A steam turbine characterized by that.   In a steam turbine in which a radial end portion of a stationary blade is fixed to a diaphragm outer ring, an opening for collecting drain is formed in an annular shape on the inner wall surface of the diaphragm outer ring, and the downstream of the annular opening is viewed from the steam flow direction. A steam turbine characterized in that an inner diameter of a side inlet portion is smaller than an inner diameter of an upstream inlet portion.   The diaphragm outer ring has an annular moisture separation duct communicating with an opening for collecting drain, and a drain discharge hole for discharging the drain collected in the moisture separation duct is formed in the lower half of the diaphragm outer ring. The steam turbine according to claim 1, wherein only the steam turbine is formed.   The steam turbine according to claim 1, wherein a member that prevents the drain collected from the opening from flowing down to the steam flow path is provided in the opening.   The steam turbine according to claim 1, wherein a return portion of a drain recovered from the opening is provided in the opening.   The moisture separation duct is characterized in that a volume of at least a part of the moisture separation duct including a portion provided with a drain discharge hole in the lower half of the diaphragm outer ring is formed larger than that of the upper half. The steam turbine according to claim 3.   The steam turbine according to claim 3, wherein a communication portion that communicates the opening and the moisture separation duct is inclined in a turbine axial direction.   The steam turbine according to claim 3, wherein the drain discharge hole is connected to a low pressure portion, and a drain trap is installed between the drain discharge hole and the low pressure portion.   A moisture separation duct is formed on the inner wall surface on the upstream or downstream side of the diaphragm outer ring holding the stationary blade, and a cover is provided to cover the moisture separation duct, and the cover collects drain in the moisture separation duct. A steam turbine characterized in that an opening surface of an opening is formed so as to open toward a steam upstream side. In a steam turbine in which a radial end of a stationary blade is fixed to a diaphragm outer ring, a moisture separation duct having an opening on the inner wall surface of the diaphragm outer ring, and a flow of drain collected covering the opening of the moisture separation duct A cover that forms a path, and a drain guide portion that guides drain to the moisture separation duct, wherein an opening surface on the steam flow path side of the drain guide portion is opened toward the steam upstream side. Steam turbine.

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