JP2016061243A - Steam turbine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steam turbine that suppresses separation of a steam flow generated in the vicinity of an outer peripheral side wall surface of a steam passage part to lower a pressure loss in the steam turbine.SOLUTION: The steam turbine includes a jetting nozzle for jetting fluid toward a downstream in an axial direction of the turbine, at the outer peripheral side wall surface on an upstream side of a stationary vane.SELECTED DRAWING: Figure 1

Description

The present invention relates to a steam turbine that suppresses flow separation occurring in the vicinity of an outer peripheral wall surface of a steam passage portion of a steam turbine.

In the low pressure part of a steam turbine installed in a thermal power plant or the like, the steam passage is configured to expand in the radial direction toward the downstream side in order to obtain significant expansion of the steam. The flow in such a steam passage has a reverse pressure gradient in which the pressure increases toward the downstream, and in such a flow field, the flow may be separated from the wall surface of the steam passage.

The cause of this separation is the influence of the leakage flow that flows out between the tip of the rotor blade and the outer peripheral side wall surface. This leakage flow has a higher flow velocity than the flow that has passed through the effective part of the blade. The leakage flow suddenly decelerates in the vicinity of the wall surface of the steam passage and the cross-sectional area of the flow path is enlarged, thereby promoting the occurrence of separation. The occurrence of such separation is one of the factors that increase energy loss in the steam turbine. Therefore, it is necessary to suppress the peeling that occurs on the outer peripheral side wall surface and reduce the loss.

Here, a conventional example of a steam turbine will be specifically described with reference to FIGS.
FIG. 5 to FIG. 7 are examples of the steam turbine, and represent a part of the vertical meridional section of the steam turbines 201, 202, 203. 5 and 6 are cross sections of the turbine stage at the final stage and the turbine upstream of the first stage, FIG. 5 shows an example in which the outer peripheral side wall surface is a straight line, and FIG. 6 shows a curve. FIG. 7 is a cross section of the turbine stage at the final stage, and shows a structure in which fluid is sucked into the outer peripheral side wall surface.

As shown in FIG. 5, a steam passage portion 231a is formed between the outer peripheral side wall surfaces 213a and 213b and the inner peripheral side wall surfaces 214a to 214d. The stationary blade 211a is supported between the outer peripheral side wall surface 213a and the inner peripheral side wall surface 214a, and the stationary blade 211b is supported between the outer peripheral side wall surface 213b and the inner peripheral side wall surface 214c. On the downstream side of the stationary blades 211a and 211b, moving blades 212a and 212b implanted in a turbine rotor (not shown) are arranged. Similarly, in FIG.
13a, 213c and inner peripheral side wall surfaces 214a to 214d are formed with a steam passage portion 231b.
, 214c.

In the steam turbine 201 shown in FIG. 5, the outer peripheral side wall surface 213b linearly expands toward the downstream side. In such a passage 231a, the outer peripheral side wall surface 2 is caused by the sudden expansion of the flow path.
In the vicinity of 13b, a flow separation 221c occurs immediately upstream of the inlet of the stationary blade 211b, and a reverse flow region 222a is generated. As a result, the loss increases.

Therefore, in order to suppress such separation of the flow, as shown in FIG.
A part of c may be configured to have a gently curved S-shape. In other words, immediately after the tip of the rotor blade and the outer peripheral side wall surface, the radial spread angle of the outer peripheral side wall surface is made gentle, and then the radial spread angle is once increased at a steep angle and then gently on the downstream side. It is formed to increase. However, even if such a configuration is provided, the flow separation 221e and the reverse flow region 222b are generated only by moving the position where the flow separation 221e occurs to the downstream side. As shown in the figure, a hole 215 and a channel 216 communicating with the hole 215 are provided in the outer peripheral side wall surface 213d, a flow 221f sucked from the hole 215 is generated, and is ejected to the tip portion of the rotor blade 212b through the channel 216. By doing so, peeling may be suppressed (see Patent Document 1). However, a strong suction force is required to prevent peeling near the outer peripheral wall surface 213d.

Further, Patent Document 2 proposes a structure in which gas ejection holes are provided on the surface of the shroud that connects the stationary blades adjacent to each other in the circumferential direction. This prevents the blade from being eroded by water droplets and reduces efficiency. Although it leads to avoidance, the gas jet direction is the longitudinal direction of the stationary blade, that is, the radial direction so that the gas hits the water droplets on the stationary blade. Therefore, there is no effect in suppressing the steam flow.

Further, in Patent Document 3, in the turbine stage of the final stage, in the annular flow path configured between the diaphragm outer ring and the inner ring, a space is provided between the diaphragm outer ring and the stationary blade along the diaphragm outer ring. Although a structure for suppressing the separation of vapor flow has been proposed by attaching an annular air guide plate to the ring, adjustment of the clearance between the annular air guide plate and the outer ring wall surface, There were also problems such as the need for special processing to attach to the stator blades.

JP 2011-99438 A JP 2014-77397 A JP2013-148059A

As described above, even if measures such as changing the shape of the steam passage or sucking the flow from the outer peripheral side wall are used to suppress the occurrence of flow separation in the steam passage, the occurrence of flow separation occurs. It was difficult to suppress. In addition, due to the trend toward longer blades in steam turbines in recent years, the radial expansion of the steam passage section with respect to the axial direction of the turbine rotor tends to increase further. Therefore, the conventional steam turbine has a problem that it is difficult to suppress the occurrence of flow separation that occurs in the vicinity of the outer peripheral side wall surface of the steam passage, and the loss increases.

In the steam turbine, there is a problem that separation occurs near the outer peripheral side wall surface of the steam passage, resulting in an increase in loss. Therefore, in order to suppress separation, the above object is achieved by providing a steam turbine provided with a jet outlet for jetting fluid toward the downstream in the axial direction of the turbine on the outer peripheral side wall surface on the upstream side of the stationary blade. .

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

FIG. 1 is a cross-sectional view of a schematic configuration diagram related to the first embodiment of the present invention, and FIG. 2 is a cross-sectional view of a schematic flow diagram related to the first embodiment of the present invention. FIG. 3 is an enlarged view of the vicinity of the spout of the cross-sectional view of the configuration schematic diagram related to the second and third embodiments of the present invention, and FIG. 4 is a cross-sectional view of the configuration schematic diagram related to the fourth embodiment of the present invention and the spout port. The schematic of the shape of is shown. Here, FIGS. 1 to 4 show cross sections of the turbine stage at the final stage.

FIG. 1 is an example of a steam turbine, and shows a cross section of a turbine stage in the final stage. Steam turbine 101
Then, a steam passage 131 is formed between the outer peripheral side wall surface 113 and the inner peripheral side wall surfaces 114a and 114b. The stationary blade 111 is supported between the outer peripheral side wall surface 113 and the inner peripheral side wall surface 114a.
A moving blade 112 planted in a turbine rotor (not shown) is disposed immediately downstream of the stationary blade 111. The jet port 11 is provided on a wall surface 113a that constitutes a passage portion on the upstream side of the stationary blade 111 in the outer peripheral side wall surface 113 with respect to the steam turbine 101. The fluid supplied from the paragraph upstream of the paragraphs constituting the stationary blade 111 and the moving blade 112 is ejected through the flow path 12 to the ejection port 11. Accordingly, since the ejected fluid has a higher pressure than the fluid to be separated, the fluid is ejected toward the separation flow by the pressure difference.

FIG. 2 specifically shows the flow of the steam, and the main flow 151 from the upstream paragraph is the stationary blade 11.
1. It passes through the moving blade 112 and becomes a flow 152. The flow 153 from the outlet 11 is ejected by the above-described pressure difference with respect to the flow separated in the vicinity of the outer peripheral side wall surface 113, so that momentum is supplied to the outer peripheral side wall surface 113 like the flow 154. It adheres and the backflow area is also eliminated.
As a result, an increase in loss due to flow separation can be prevented.

FIG. 3 shows an enlarged view of the vicinity of the jet outlet according to the second and third embodiments of the present invention. As shown in FIG. 3, if the jet angle 13 is too large with respect to the outer peripheral side wall 113, the flow direction from the jet port 11 becomes the radial direction, which promotes the separation flow. Further, since the momentum cannot be supplied to the entire separation flow even if the jet angle 13 is too small, it is similarly not preferable. Based on such knowledge, the jet port 11 is provided on the outer peripheral side wall surface 113 so that the flow from the jet port is in the range of 30 ° to 45 °. Thus, by setting the ejection angle 13 in the range of 30 ° to 45 °, the momentum can be supplied in a balanced manner in the axial direction and the radial direction with respect to the separated flow. Reattachment to the outer peripheral side wall surface can be promoted.

Furthermore, the flow velocity of the flow 155 ejected from the ejection port is from 1.0 times the flow velocity of the main flow 151 to 1.
Try to be 5 times the range. When a flow slower than the main flow velocity is ejected from the jet outlet, the flow is decelerated and acts in a direction that promotes flow separation, which increases the reverse flow region and increases the loss. In this way, by making the angle of ejection in the range of 30 ° to 45 °, and in the range of 1.0 to 1.5 times the main flow rate, it is more effective without increasing the backflow region. Since the separation can be reattached to the outer peripheral side wall surface, the backflow region is eliminated, and an increase in loss due to the separation of the flow can be prevented more effectively.

FIG. 4 shows a cross-sectional view of a schematic configuration diagram relating to the fourth embodiment of the present invention and a schematic diagram of the shape of a jet port. FIG. 4B shows the shape of the spout as seen from the direction A in FIG. Here, the left side in the figure represents the upstream and the right side represents the downstream. Moreover, all the jet nozzles 14a to 14c have the same shape, which indicates that a plurality of jet nozzles 14a to 14c are provided along the outer peripheral wall surface. The shape of the spout is 14c
As shown by using, two ellipses 15 and 16 are combined. In particular,
Of the two ellipses, the half 15a (blunt ellipse, blunt head) of the ellipse 15 having a smaller value obtained by dividing the major axis of the ellipse by the minor axis is used on the upstream side, and the half 16a (elongated) of the larger ellipse 16 is used. A shape in which an ellipse or a sharp head) is used on the downstream side is used for the jet outlet.

By combining a blunt ellipse on the upstream side and a long and narrow ellipse on the downstream side, the upstream side is blunt, so a uniform flow can be stably ejected in the turbine axis direction, and there are few The flow can be ejected with resistance, and the flow can be ejected in a wide range in the turbine axis direction by using a thin ellipse on the downstream side. As a result, it becomes possible to promote the reattachment of the separated flow more effectively, and thus it is possible to more effectively prevent the loss due to the flow separation.

You may combine the said 1st-4th Example with the jet outlet and the flow to eject.

In this way, by providing a spout on the upstream side of the stationary blade and ejecting the flow to the separated flow near the outer peripheral side wall surface to supply momentum, reattachment is promoted, and the distance from separation to reattachment Can be shortened. As a result, loss due to separation is reduced, and the efficiency of the turbine can be improved.

1 is a schematic configuration diagram relating to the first embodiment of the present invention. Schematic of the flow related to the first embodiment of the present invention Schematic configuration related to second and third embodiments of the present invention Schematic configuration related to the fourth embodiment of the present invention 1 is a schematic configuration diagram (cross-sectional view) relating to an embodiment of the present invention. Configuration schematic diagram 2 (cross-sectional view) relating to the embodiment before the present invention Configuration schematic diagram 3 (cross-sectional view) related to the embodiment before the present invention

A: View point 11: Outlet 12: Outlet channel 13: Outlet angles 14a to 14c: Outlet shapes 15a, 15b, 16a, 16b: Ellipses 101, 201, 202, 203: Steam turbines 111, 211a, 211b: Stator blades 112, 212a, 212b: Rotor blades 113, 213a to 213c: Outer peripheral side wall surfaces 114a, 114b, 214a to 214d: Inner peripheral side wall surfaces 131, 231a to 231c: Steam passage portion 151: Main flow 152, 221d, 221i: Static Flows 153, 155, and 156 that pass through blades and moving blades: Flow 154 from the ejection port 154: Flow that reattaches 215: Hole 216: Channel 221a: Flow 221b that flows into the stationary blade 221: Tip partial leakage flows 221c, 221e: Flow separation 222a, 222b: reverse flow region 221f: suction flow 221g: flow 221h passing through flow path: h Flow to be ejected into the flops part

Claims (5)

In a steam turbine, in which a stationary blade is arranged in a circumferential direction between an outer peripheral side wall surface and an inner peripheral side wall surface constituting a steam passage portion that sequentially expands to a steam flow, and a moving blade is provided downstream of the stationary blade, A steam turbine characterized in that at least one jet outlet for jetting fluid toward the downstream side of the turbine is formed in the peripheral side wall surface on the upstream side of the blade in the circumferential direction. The steam turbine according to claim 1, wherein a fluid is ejected from the ejection port in a range of 30 ° to 45 ° with respect to the outer peripheral wall surface. The steam turbine according to claim 1, wherein a flow velocity of the steam ejected from the ejection port is equal to or greater than a flow velocity of the main flow of the turbine. The shape of the outlet of the jet outlet is a combination of two ellipses, and the ellipse having a larger value obtained by dividing the major axis of the ellipse by the minor axis is used on the downstream side of the steam turbine. 2. The steam turbine according to claim 1, wherein the ellipse having a smaller value is used on the upstream side of the steam turbine. 5. The steam turbine according to claim 1, wherein a jet port is provided in a portion of the outer peripheral side wall surface upstream of the stationary blade and constituting the steam passage portion. 6. .

Images