JP2902702B2 - Pelton turbine - Google Patents

Description

The present invention relates to a Pelton turbine, and more particularly to a Pelton turbine having an improved bucket wheel structure as a runner.

(Prior Art) Various models such as Pelton turbine, Francis turbine, mixed flow turbine, Kaplan turbine, etc. are known as hydraulic machines used in hydroelectric power plants. These are selected according to the topographical conditions and flow conditions of the installed hydropower station. Above all, Pelton turbines are for high heads and are suitable mainly when water volume is relatively small. Therefore, Pelton turbines are often installed in hydropower stations in steep mountainous areas.

FIG. 4 shows a schematic configuration of a general Pelton turbine. A bucket wheel 2 is attached to a main shaft 1 that drives a generator, thereby forming a runner. The bucket wheel 2 includes a bucket portion 3 that receives the injection water,
The disk unit 4 is connected to the main shaft 1. The nozzle 5 is arranged in the connection direction of the bucket part 3,
Pressurized water 7 is guided to the nozzle 5 from an iron pipe line 6a traversing the casing 6.

Then, the pressure water 7 guided from the iron pipe line 6a traversing the casing 6 is converted into spray water 8 by the nozzle 5, as shown in FIG. After colliding with and performing work, it is discharged to a water discharge channel (not shown). The bucket wheel 2 has a nozzle 5
Is driven to rotate by the jet force of the high-pressure jet water 8 applied to the bucket portion 3 from the outlet. The rotating drive of the bucket wheel 2 drives a generator (not shown) via the main shaft 1 to generate power.

As described above, the Pelton turbine is a so-called impulse turbine, and the jet force is an unsteady flow depending on time. Therefore, the root of the bucket portion 3 of the bucket wheel 2 is:
Repeated stresses are generated and are subjected to extremely severe stress conditions.

The runner of the hydraulic machine is a part that converts the energy of the head of water flowing from a high place to a low place into rotational energy. For this reason, it is necessary to maintain the strength of the portion receiving the pressurized water at a high level. To keep the strength high, the runner is usually made of cast steel. However, cast steel as a raw material almost inevitably causes defects such as shrinkage cavities, sand scum, slag entrainment, blowholes, etc. at the stage of its production. For this reason, it is common to detect defects on the surface layer and inside the material by non-destructive inspection, and repair by welding or the like.

Non-destructive inspection methods for cast steel materials include the following two methods for detecting defects on the surface layer and near the surface layer (inside the material at a depth of 2 to 3 mm from the surface). The first method is a liquid penetration inspection method (hereinafter, referred to as PT), and the second method is a magnetic particle inspection method (hereinafter, referred to as MT). Further, an ultrasonic flaw detection method (hereinafter referred to as UT) is employed for detecting a defect in a deep portion in a material.

In the detection of the defect of the bucket wheel 2, the entire PT and MT are performed on the material. And, especially at the root of the bucket portion 3 which is exposed to severe conditions in terms of stress,
Further, UT for the inner part is used together.

In this way, nondestructive inspection is performed on the material, and appropriate repairs are made to the detected defects to prevent accidents that could cause the defects to develop during operation and lead to the destruction of the runner. Preventing.

(Problems to be Solved by the Invention) By the way, the bucket wheel 2 has a configuration in which the bucket portion 3 and the disk portion 4 are integrally cast, so that the cost is low. Therefore, when there is no casting capacity at the time of material production, dimensional restrictions at the time of transportation, and weight restrictions, as shown in FIG. 6 and FIG.
Is often cast in one piece. However, when the non-destructive inspection is performed, the bucket wheel 2 of the integral casting type has a PT or
There is no particular problem in MT, but the following problems occur when implementing UT.

In other words, it is most suitable to apply the probe beam of the UT at right angles to the direction of the defect, both in terms of detection capability and detection accuracy. However, defects existing in the cast steel material do not have uniformity in direction, and the defect detection rate is poor in flaw detection from only one direction. Further, a range of a depth of about 10 mm from the surface of the material is a non-flaw-detectable area called a dead zone, and is difficult to inspect.

Therefore, as means to eliminate the untestable area of such a flaw detection zone, a vertical flaw detector using a vertical probe that can emit a beam at right angles to the contact surface and an oblique probe that can emit a beam obliquely are available. The angle of flaw detection used is also used.

FIG. 8 illustrates a case in which UT is applied to the root of the bucket portion 3 of the integrally cast bucket wheel 2. The vertical probe 9 and the oblique angle probe 10 are arranged with respect to the flaw detection zone A represented by the hatched lattice portion.

However, the vertical probe 9 must be arranged on the inner bottom surface of the bucket 3 due to structural restrictions, and an appropriate distance from the flaw detection zone A cannot be secured. In other words, the flaw detection zone A within a depth range of about 10 mm from the surface layer becomes a dead zone for the vertical probe 9, so that flaw detection becomes impossible. Therefore, flaw detection zone A
In this case, the flaw detection cannot be performed vertically, and only the bevel flaw detection by the bevel probe 10 is used.

When the runner is large, the bucket wheel is often divided. For example, FIG. 9 and FIG.
As shown in the figure, a bucket wheel 21 is divided into a single type divided bucket portion composed of a large number of single wing-shaped bucket elements.
22 and a disk unit 23 to which each single-type split bucket unit 22 is attached. Each single-type split bucket portion 22 and the disk portion 23 are fixed and positioned by a reamer bolt 24 and a nut 25, a wedge 26 for fixing an angle, and the like.

Further, as shown in FIGS. 11 and 12, there is also a configuration in which a bucket wheel 31 is divided into a twin-type split bucket section 32 composed of twin-wing-shaped bucket elements and a disk section 33. In this case, fixing and positioning are performed by the reamer bolt 24, the nut 35, the angle fixing wedge 36, and the like.

In the above configuration, the single type divided bucket section
In both cases of 22 and the twin split bucket section 32,
There are enough surfaces on which the vertical probe 9 and the oblique probe 10 can be placed. Therefore, the flaw detection inspection of the flaw detection zone A by the UT can be performed without any problem.

However, since the bucket portion is configured as a single type or twin type, the number of machining locations increases, and the number of mounting parts and fastening assembly locations of the rotating portion increase. For this reason, a problem occurs in maintenance. In addition, the cost is considerably higher than that having an integrally cast bucket wheel.

The present invention has been made in view of such circumstances, and it is possible to sufficiently perform flaw detection inspection by UT and improve maintainability at a root portion of a bucket portion, which is a main stress portion of a bucket wheel, and furthermore, it is possible to achieve a high performance. An object of the present invention is to provide a Pelton turbine that can effectively achieve quality and cost reduction.

[Configuration of the invention]

(Means for Solving the Problems) In a Pelton turbine according to the present invention, a bucket wheel as a runner rotatably driven by injection water is provided on a disk portion provided on a main shaft, and provided separately from the disk portion, and In the Pelton turbine including a bucket portion joined to an outer peripheral portion of a disc portion, the bucket portion is formed by integrally forming all bucket elements on a ring-shaped base, and the base has a flat edge. A bucket element base end portion formed into a base plate and a disk connection piece extending in a flange shape, and the bucket element base end portion is made thicker than the disk connection piece to form a step, while the disk of the base is formed. A connecting piece is fixedly connected to the disk part.

(Operation) According to the present invention, the base body of the bucket portion is divided into a bucket element base end having a flat edge and a flange-shaped disk connecting piece, and the bucket element base is connected to the disk. Since the step is formed thicker than the piece, it is possible to secure a sufficient installation distance for the flaw detection inspection by the UT, to secure a stable installation posture, and to improve maintainability. In addition, since the bucket wheel is divided into a bucket part integrally cast in a ring shape and a disk part connected to the main shaft, the bucket part and the disk part can be fastened by a small number of coupling members. Therefore, the number of components is small, and high quality and low cost can be effectively achieved.

Embodiment An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 is an axial sectional view showing a bucket wheel portion of the Pelton turbine according to the present embodiment, FIG. 2 is an exploded perspective view, and FIG.
The figure shows the flaw detection effect of the UT probe.

As shown in FIGS. 1 and 2, the bucket wheel
Reference numeral 41 denotes a divided bucket 42 as a bucket unit integrally formed in a ring shape, and a disk unit 43. That is, in the divided bucket 42, all the bucket elements 42b are integrally formed on a ring-shaped base 42a. The base body 42a is divided into a bucket element base end 42d having an edge 42c formed flat and a flange-shaped disk connection piece 42e extending toward the disk portion 43. Shoulder 42f thicker than 42e
And the divided bucket 42 and the disk part
43 is fastened by several, for example, six reamer bolts 44 and nuts 45 as connecting members. The disk unit 43 is connected to the main shaft 46, and the main shaft 46
Is connected to a generator (not shown).

According to such a configuration, as shown in FIG. 3, the base 42a of the divided bucket 42 is divided into a bucket element base end 42d having a flat edge 42c and a flange-shaped disk connecting piece 42e. Connect the element base end 42d to the disk connection piece 4
Since the step 42f was formed thicker than 2e, the vertical probe 4
The distance 7 and the installation position required for the flaw detection inspection can be sufficiently secured for the 7 and the angle probe 48. That is, the divided bucket 42
, The distance required for the flaw detection inspection by the UT can be sufficiently maintained, and a surface parallel to the longitudinal direction of the flaw detection band B can be sufficiently ensured. Therefore, it is possible to perform sufficient vertical inspection under very favorable conditions.Non-destructive inspection can be performed on the material, and the detected defect can be repaired appropriately. It is possible to prevent the occurrence of an accident that causes the runner to be destroyed by progress.

Further, as described above, since assembly and fixing are performed simply by using several reamer bolts 44 and nuts 45, the cost can be effectively reduced.

According to the above-described embodiment, the bucket wheel 41 has a divided configuration of the divided bucket 42 and the disk portion 43, and the base 42a of the divided bucket 42 has a base end portion of a bucket element having a flat edge 42c. 42d and a flange-shaped disk connection piece 42e, and the bucket element base end 42d is thicker than the disk connection piece 42e to form a stepped portion 42f, while the divided bucket portion 42 and the disk portion 43 are formed in a small number. Since the fastening is performed by the coupling member, it is possible to secure a sufficient installation distance for the flaw detection inspection by the UT, to secure a stable installation posture and to improve the maintainability, and to effectively achieve high quality and low cost.

〔The invention's effect〕

As described above, according to the Pelton turbine according to the present invention,
At the root of the bucket part, which is the main stress part of the bucket wheel, it is possible to carry out sufficient inspections for flaw detection using UT, thereby improving maintainability and effectively achieving high quality and low cost. Is played.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, FIG. 2 is an exploded perspective view, FIG. 3 is a view showing a state of UT detection, FIG. 4 is a schematic sectional view of a general Pelton turbine, FIG. FIG. 5 is a view showing a state of collision of the jet water with respect to a bucket portion, FIG. 6 is a partial cross-sectional view showing an integral casting type bucket wheel as a conventional example, FIG. 7 is a plan view of FIG. 6, and FIG. The figure which shows a contact state, 9th
FIG. 10 is a sectional view showing a single type split bucket structure as another conventional example, FIG. 10 is a plan view of FIG. 9, FIG. 11 is a view showing a twin type bucket structure as still another conventional example, and FIG. Is the eleventh
It is a top view of a figure. 41 ... bucket wheel, 42 ... divided bucket (bucket part), 42a ... base, 42b ... bucket element, 42c ... edge, 42d ... bucket element base end, 42e ... disk connecting piece, 42f ... step, 43 ... disk Part, 44 ... reamer bolt (joining member), 45 ... nut (joining member), 46 ... spindle.

Claims (1)

(57) [Claims] A bucket wheel as a runner rotatably driven by jet water is provided on a disk portion provided on a main shaft, and a bucket portion provided separately from the disk portion and joined to an outer peripheral edge of the disk portion. In the Pelton turbine configured by the above, the bucket portion is configured such that all bucket elements are integrally formed on a ring-shaped base, and the base is a bucket element base end having a flat edge, and a flange-shaped base. The disk element is divided into a disk connecting piece extending in the direction of the arrow, and the base end of the bucket element is made thicker than the disk connecting piece to form a step, and the disk connecting piece of the base is fixedly connected to the disk part. Pelton turbine characterized by that.