Patent Application
20120099967
Embodiments basically relate to a steam turbine provided with a structure to remove moisture attaching to rotating blades thereof.
In a steam-power generation plant, a high pressure turbine is combined with an intermediate pressure turbine and a low pressure turbine in many cases. The high pressure turbine is rotated by main steam. The intermediate pressure turbine and the low pressure turbine are rotated also by the main steam which has passed through the high pressure turbine. In the low pressure turbine in which steam pressure is low, temperature and pressure of the steam lower during an expansion process of the steam in a low-pressure stage thereof, and a part of the steam condenses into moisture. Influence of the moisture on the steam turbine will be described below with reference to the drawings.
In
The water droplets 109 cannot move completely into a steam flow as a result of inertia thereof. This event causes the water droplets 109 to collide with the suction side 110 of the turbine rotating blade 102 which is rotating. The collision of the water droplets 109 with the suction side of the turbine rotating blade 102 serves as a retarding force against the rotation of the turbine rotating blade 102, and reduces turbine efficiency. The turbine rotating blade 102 is likely to be eroded because the water droplets 109 attach to the suction side 110 of the turbine rotating blade 102.
As described above, the moisture attaching to the turbine rotating blade 102 has an adverse effect on efficiency and reliability of a turbine. On the other hand, there is known a steam turbine provided with a structure to remove attached moisture. Such a device will be described below with reference to
The device shown in
On the other hand, the device shown in
As mentioned above, the device providing the turbine rotating blade 102 with the grooves 112 has less impact on turbine efficiency than the device providing the turbine rotating blade 102 with a hollow and the slit 111. However, steam is likely to flow out of the grooves 112 to the outside of the rotating blade cover 106.
The nearer the final stage of the turbine rotating blade 102, the more moisture attaching to the turbine rotating blade 102 is. When the number of the grooves 112 is increased to deal with an increase in moisture, the number of the grooves 112 passing through the connected rotating blade covers 106 or the number of exhaust nozzles for water droplets is also increased. This increases an amount of steam flowing out of the rotating blade cover 106.
It is also necessary to enlarge the entrance width of the drain pocket 113 in connection with increasing the number of the grooves 112. When enlarging the entrance width of the drain pocket 113, the amount of the steam flowing into the drain pocket 113 also increases. When the drain pocket 113 is located on the vertically upper side of the turbine rotating blade 102, moisture is likely to collide with the inside wall of the drain pocket 113 having a wide entrance and to reflect on the inside wall. In such a case, the moisture is likely to fall from the wide entrance to the side of the turbine rotating blade 102.
Aspects of this disclosure will become apparent upon reading the following detailed description and upon reference to the accompanying drawings.
As will be described later, in accordance with an embodiment, a steam turbine includes two or more rotating blades and a diaphragm outer ring. Each of the rotating blades includes a tip cover, moisture-trapping grooves, a droplet ejection hole, and a drain guide groove. The tip cover is provided to a tip of each of the rotating blades and is connected in contact with another tip cover adjacent to the tip cover. The moisture-trapping grooves are formed in a longitudinal direction of each of the rotating blades on a trailing edge of each of the rotating blades. The droplet ejection hole is formed so that the droplet ejection hole connects an outside of the tip cover on a side of the diaphragm outer ring with an inside of the tip cover on a side of each of the rotating blade. The drain guide groove is formed so that the drain guide groove connects ends of the moisture-trapping grooves on the side of the tip cover with the droplet ejection hole. The diaphragm outer ring includes a drain pocket which faces the droplet ejection hole.
Embodiments will be described below with reference to the drawings.
A structure of a steam turbine in accordance with a first embodiment will be described below with reference to
The rotating blade 1 is planted on a turbine rotor (not shown). In
Two or more moisture-trapping grooves 2 are formed on the front edge of the rotating blade 1 viewed from the suction side of the rotating blade 1. Moisture comes from the nozzle (not shown) to attach to the moisture-trapping grooves 2. A tip cover 3 is arranged on the upper end of the rotating blade 1. The tip cover 3 connects in contact with another tip cover 3 on the adjacent rotating blade 1, thereby suppressing vibration of the tips of the rotating blades 1. The tip cover 3 also prevents steam from flowing out of a blade row of the rotating blades 1, thereby preventing a reduction in turbine efficiency.
A drain guide groove 4 is formed through the tip cover 3 on the top side of the rotating blade 1. The nearer the rear of the rotating blade 1, the deeper the drain guide groove 4 becomes. The drain guide groove 4 connects to a droplet ejection hole 5 formed on the surface of the tip cover 3.
A diaphragm outer ring 6 is arranged outside the rotating blades 1. A drain pocket 7 is formed in the diaphragm outer ring 6. The drain pocket 7 is located outside the droplet ejection hole 5 when the drain pocket 7 is viewed from the rotation axis of the rotating blades 1. Tip fins 8 are mounted on the diaphragm outer ring 6. The mounting position thereof is located between the diaphragm outer ring 6 and the trailing edge of the rotating blade 1 both facing each other. The tip fins 8 serve as channel resistance of a gap between the tip cover 3 and the diaphragm outer ring 6 to reduce the amount of steam passing through the gap.
The position of the drain guide groove 4 will be described in detail with reference to
A function of the rotating blade 1 having such a structure will be described with reference to
As described above, it is possible to trap moisture attached to the moisture-trapping grooves 2 in the drain pocket 7 by guiding moisture to the droplet ejection hole 5 via the drain guide groove 4. As a result, even when increasing the number of moisture-trapping grooves 2, the number of droplet ejection holes 5 is not needed to be increased. The droplet ejection holes 5 are to be formed so that the side of the tip cover 3 on the side of the rotating blade is in communication with the other side of the tip cover on the side of the diaphragm outer ring 6. Accordingly, it is possible to make smaller the amount of steam which flows out of the droplet ejection hole 5 into the side of the diaphragm outer ring 6 than before.
Increasing the number of the moisture-trapping grooves 2 does not require widening the entrance of the drain pocket 7, thereby allowing it to make the amount of the steam flowing into the drain pocket 7 smaller than before.
As described above, the steam turbine in accordance with the embodiment reduces loss of steam, thereby enabling it to make turbine efficiency higher than before.
The embodiment has been described under the assumption that the nearer the rear of the rotating blade 1, the deeper the drain guide groove 4 is.
Alternatively, the depth of the drain guide groove 4 may be constant if the bottom of the drain guide groove 4 sinks toward the rear of the rotating blade 1 and in the radial direction of the turbine. For example, when the tip of the rotating blade 1 inclines as shown in
A steam turbine in accordance with a second embodiment will be described below with reference to
P/L<0.5 (1)
Evaluating loca of moisture in a blade row of rotating blades 1 clarifies that most of the moisture coming from a nozzle not shown collides with the area of the rotating blade 1 determined by the formula (1). Therefore, forming two or more moisture-trapping grooves 2 in the area determined by the formula (1) enables it to efficiently remove moisture which attaches to the rotating blades 1.
The steam turbine of this embodiment enables it to more efficiently remove moisture attaching to the rotating blades 1 in addition to the same effect as that of the first embodiment.
A steam turbine in accordance with a third embodiment will be described below with reference to
A structure of the second drain guide groove 21 will be described in detail with reference to
A function of the second drain guide groove 21 will be described below. Centrifugal force acts on water droplets coming from a nozzle (not shown) or on moisture in steam. As a result of the centrifugal force, a portion of the water droplets or the moisture is likely to attach to the inside surface of the tip cover 3. Once the droplets or the moisture attached goes into the second drain guide groove 21, the droplets or the moisture moves to a droplet ejection hole 5 as a result of the centrifugal force. Eventually the droplets or the moisture is ejected from the droplet ejection hole 5 to be collected into a drain pocket 7.
In accordance with the steam turbine of this embodiment, the second drain guide groove 21 enables it to remove moisture attached to the surface of the tip cover 3 on the side of the rotating blade 1 in the same way as removing moisture attached to the rotating blade 1. The second drain guide groove 21 is formed on the under surface of the tip cover 3. This is a new effect in addition to that of the first embodiment.
A fourth embodiment will be described below with reference to the drawings. Wherever possible, the same reference numerals as those of the first embodiment will be used to denote the same or like parts throughout the drawings. The same explanation will not be repeated.
The second drain guide groove 31 will be described in detail with reference to
The depth of the second drain guide groove 31 is fixed. The tip cover 3 inclines so that:
In accordance with a steam turbine of the embodiment, it is possible to effectively remove the moisture attached to the surface of the tip cover 3 on the side of the rotating blade 1 in the same way as removing moisture attached to the rotating blade 1. This is a new effect in addition to the same effect of the first embodiment.
A steam turbine in accordance with a modified example of the fourth embodiment will be described with reference to
As described above, arranging the drain guide weir 32 instead of the second drain guide groove 31 allows it to acquire the same effect as that of the fourth embodiment.
A fifth embodiment will be described below with reference to a drawing. Wherever possible, the same reference numerals as those of the first embodiment will be used to denote the same or like parts throughout the drawing. The same explanation will not be repeated.
A function of the sloping surface 41 will be described below. Water droplets 9 jump out of a droplet ejection hole 5 arranged on a tip cover 3, and are collected into the drain pocket 7 while drawing substantially an orbit 42. That is, the water droplets 9 jump out of the droplet ejection hole 5 and collide with the sloping surface 41. Subsequently, the droplets 9 are reflected on the sloping surface 41 to be trapped in the drain pocket 7.
When a bottom face of the drain pocket 7 is parallel to the rotation axis of the steam turbine, water droplets 9 collided with the bottom face is reflected on the bottom face and jump out of the drain pocket 7. The water droplets 9 having jumped out are likely to return to the side of the tip cover 3. However, as described above, forming the sloping surface 41 on the bottom face of the drain pocket 7 allows it to prevent the water droplets 9 from returning to the side of the tip cover 3 from the drain pocket 7.
In this embodiment, the sloping surface 41 has been described as a sloping surface sloping from the leading edge of the turbine over the trailing edge thereof toward the inner circumference thereof. Alternatively, the sloping surface may slope from the trailing edge of the turbine over the leading edge thereof toward the inner circumference thereof.
Although the embodiments have been described above with reference to the drawings, the invention is not limited to the embodiments. The invention may adopt various combinations or modifications of the embodiments within the scope of the invention. For example, it is possible to combine the configurations of the rotating blades 1 described in the first to fourth embodiments with the drain pocket 7 described in the fifth embodiment.
While certain embodiments have been described, those embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-166076 | Jul 2009 | JP | national |
This is a Continuation of PCT Application No. PCT/JP2010/004229, filed on Jun. 25, 2010, which is based upon and claims the benefit of priority from the prior Japanese Patent Application No.2009-166076, filed on Jul. 14, 2009, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2010/004229 | Jun 2010 | US |
| Child | 13340913 | US |
