JP2006037791A - Radial flow type steam turbine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly efficient radial flow type steam turbine in which steam flows in radial direction on a plane substantially perpendicular to a turbine rotary shaft. <P>SOLUTION: This radial flow type steam turbine includes a pair of rotary plates 3, 5 arranged in the direction substantially perpendicular to the turbine shaft and a plurality of blades 3a-3d, 5a-5d alternately provided on a surface facing a pair of the rotary plates 3, 5 to overlap in a radial direction from an inner circumference toward an outer circumference, and steam flows toward an outer circumference part from an inner circumference part between the blades. An interval of blade steps is 0.5 times or more of the minimum interval between adjoining blades of a high pressure side front step. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radial flow steam turbine in which steam flows radially in a plane substantially perpendicular to the turbine rotation axis.

A typical example of a radial flow type steam turbine in which steam flows radially in a plane substantially perpendicular to the turbine rotation axis is a Jungstrom turbine.
FIG. 8 is an explanatory diagram for explaining the outline of the Jungstrom turbine. As shown in FIG. 8, the Jungstrom turbine is rotatably supported by a casing 101 and extends inward from both sides of the casing 101, and a rotating plate attached to the rotating shafts 103 and 105. 107 and 109. The rotating plates 107 and 109 are provided with a plurality of blades 111 and 113 in the radial direction.

A steam chamber 115 is provided inside the casing 101, and steam introduction pipes 117 and 119 are connected to the steam chamber 115 from the outside of the casing 101. The steam chamber 115 and the space 121 sandwiched between the rotating plates 107 and 109 communicate with each other, and steam introduced into the steam chamber 115 from the steam introduction pipes 117 and 119 is introduced into the space 121. The introduced steam flows in a radial direction from the space 121 between the moving blades 111 and 113, and the moving blades 111 and 113 arranged adjacent to each other in the radial direction serve as guide blades for the other moving blade. Thus, the rotating plates 107 and 109 rotate in the opposite direction at the same speed (for example, see Non-Patent Document 1).
Nishikawa et al., “Steam Turbine Understanding”, Nissin Publishing Co., Ltd., April 30, 1999, 6th edition p179-180 (text, Fig. 9 ・ 17)

The radial flow type steam turbine has a feature that it can be efficiently and downsized with a relatively small number of stages. Further, since the peripheral speed is constant over the entire length of the turbine blades in each stage, it has characteristics such as higher efficiency than an axial flow turbine in which steam flows in the rotation axis direction.
However, in recent years, the need for large-output steam turbines with a large power generation scale has been the mainstream, so axial-flow turbines that are easy to increase in size are the mainstream. Almost no suggestion.
Accordingly, an object of the present invention is to provide a high-efficiency radial flow steam turbine.

FIG. 1 is a cross-sectional view of the radial flow steam turbine according to the present invention along the rotational axis, and FIG. 2 shows a part of the cross section taken along the line AA of FIG. FIG. 3 is an enlarged view of a part of FIG. 2 (a part of the third and fourth stages). Hereinafter, the background and contents of the present invention will be described with reference to FIGS.
In the radial flow type steam turbine having the structure as shown in FIG. 1, the steam outflow speed of the previous stage (N-1 stage in FIG. 3) is used as the inflow speed of the N stage as shown by the arrow in FIG. Therefore, the output can be improved by improving the speed utilization rate at this time.

This point will be described in more detail.
As shown in FIG. 3, steam having an outflow rate: C ₂ flows into the N stage from the upstream stage (N−1 stage) on the steam high pressure side. At this time, the outflow speed: C ₂ becomes the inflow speed: C ₀ in the N stage, and can be expressed as C ₀ = εC ₂ (ε: speed utilization factor). If there is no loss when steam flows from the N-1 stage to the N stage, ε = 1. However, ε takes a value smaller than 1 due to various losses.
Therefore, it is necessary to reduce various losses in order to improve the speed utilization factor and approach ε = 1.
As a result of intensive studies on how to reduce the various losses, the inventors have obtained the knowledge that the blade stage spacing is one of the important parameters related to the speed utilization rate improvement.
Here, as shown in FIG. 4, the blade stage interval refers to the minimum interval between the N−1 stage blade rear end and the N stage blade front end, specifically, Δr shown in FIG. 4.

In order to know the relationship between the blade stage spacing and the speed utilization factor, the inventors first performed a simulation of how the speed utilization factor would be by making the blade stage spacing as narrow as possible, as shown in FIG. In this case, however, the rate utilization rate was not very large.
The reason for this is considered as follows. As shown in FIG. 5, since the N-1 stage blades and the N stage blades rotate in the opposite directions, steam instantaneously flows into the blade stage interval even if the blade stage interval is narrowed. Moreover, since the blade stage interval is set narrow, the steam flow flowing into the blade stage interval becomes high speed. This high speed steam flow collides with the steam flow of the main stream from N-1 stage to N stage (the flow of the thick arrow in FIG. 5) and disturbs this flow, so that the speed utilization rate is impaired. it is conceivable that.

  From this study, we thought that it was necessary to prevent the flow velocity of the steam flowing into the blade stage interval from becoming too high compared to the main stream, as long as steam inflow into the blade stage space was unavoidable. That is, the main flow is defined by the outlet speed of the preceding stage (N-1 stage), and this outlet speed is the minimum distance S between the adjacent blades of the preceding stage (in other words, the minimum distance between the blade trailing edge and the adjacent blade) ( Therefore, in order to prevent the steam flow velocity flowing into the blade stage interval from becoming very high with respect to the main flow, the blade stage interval Δr is set to a certain value or more with respect to the minimum interval S. I found that it was necessary.

  On the other hand, as shown in FIG. 6, when the blade stage interval Δr was set larger than a certain interval, a similar simulation was performed, and the speed utilization rate was low. As a result of examining this reason, as shown in FIG. 6, since the flow passage area between the blade stages is increased by widening the blade stage interval Δr, the speed decreases while passing between the stages. As a result, it is considered that the inflow speed in the N stage is lower than the outlet speed in the previous stage (N-1 stage) and the speed utilization rate is impaired.

From the results of the above examination, the inventors further analyzed and tested, and as a result, optimally designed the minimum spacing S between adjacent blades and the blade stage spacing Δr in the upstream side (N-1 stage) of the high pressure side. The knowledge that the utilization rate can be improved was obtained.
Therefore, further simulation was performed to know the relationship between the speed utilization factor ε and A = Δr / S, and the result shown in FIG. 7 was obtained. In FIG. 7, the vertical axis represents the speed utilization factor ε, and the horizontal axis represents A = Δr / S.
As can be seen from FIG. 7, there is a fixed relationship between the speed utilization factor ε and A = Δr / S, and it is clear that the speed utilization factor ε can be improved by setting A = Δr / S to an optimum value. Became. As can be seen from FIG. 7, the optimum value of A here is a value at which the speed utilization rate exceeds 0.8, A = 0.5 to 5, and a more preferable optimum value is speed utilization. It is a value when the rate exceeds 0.9, and A = 0.75 to 2.5.
The present invention has been made based on the above findings.

(1) A radial flow steam turbine according to the present invention includes a pair of plate-like members opposed to each other installed in a direction substantially perpendicular to the turbine shaft, and an inner surface on opposite surfaces of the pair of plate-like members. A plurality of blades alternately provided so as to overlap each other in the radial direction toward the outer periphery, and the steam flows between the blades from the inner peripheral portion toward the outer peripheral portion, and the interval between the blade stages Is 0.5 times or more the minimum distance between adjacent blades on the upstream side of the high pressure side.
The pair of plate-like members may be rotating plates that rotate together, and the blades provided on them may be moving blades, or one of the pair of plate-like members may be a rotating plate and the other fixed. The blades provided as the plates may be moving blades and stationary blades.

(2) Further, in the above (1), the interval between the blade stages is not more than 5 times the minimum interval between the adjacent blades on the high pressure side front stage.

  In the present invention, by setting an appropriate stage interval, it is possible to provide a turbine with a high speed utilization factor of the upstream steam outflow speed, and it has become possible to effectively use energy more reliably than before.

  FIG. 1 is an explanatory view illustrating the structure of a radial flow steam turbine 1 according to the present embodiment. In the radial flow steam turbine 1 according to the present embodiment, a plurality of moving blades are alternately arranged in a plane substantially perpendicular to the turbine shaft so as to overlap each other in the radial direction from the inner peripheral portion toward the outer peripheral portion. The steam flows in a radial direction between the plurality of blades, and the blade interval is set to 7 mm, and the minimum interval between adjacent blades on the high pressure side front is set to 5 mm. Hereinafter, the configuration of the radial flow type steam turbine 1 will be described in more detail.

The radial flow type steam turbine 1 has a pair of rotating plates 3 and 5 that are opposed to each other with a predetermined distance, and on the opposing surface side of these rotating plates 3 and 5, the radius is increased from the center side toward the outer peripheral side. A plurality of moving blades 3a, 3b, 3c, 3d and moving blades 5a, 5b, 5c, 5d are respectively attached in the direction. The rotor blades 3 a to 3 d and the rotor blades 5 a to 5 d are installed alternately adjacent to each other in the radial direction of the rotary plates 3 and 5. A plurality of blade rows extending in the radial direction are provided in the circumferential direction of the rotary plates 3 and 5.
These moving blades 3a to 3d and 5a to 5d are reaction blades, and the flow passage area is narrowed toward the outlet, and the introduced steam is accelerated and dropped as it goes to the outer periphery. At this time, a rotational force is generated in the rotor blade by the action of converting the heat energy into the rotational energy.

A steam introduction space 4 is formed in the central portion on the opposite side of the rotary plates 3 and 5. A steam introduction path (not shown) communicates with the steam introduction space 4 so that steam can be introduced from the outside.
Further, rotary shafts 9 and 11 are respectively attached to the central portions of the rotary plates 3 and 5, and the rotary shafts 9 and 11 are rotatably supported by bearings 13a and 13b and 15a and 15b, respectively.
One end portions of the rotary plates 3 and 5 and the rotary shafts 9 and 11 as described above are accommodated in the casing 17, and the casing 17 and the bearings 13a and 13b and 15a and 15b are supported by a fixed portion (not shown). The casing 17 and the rotary shafts 9 and 11 are sealed with seals 19 respectively.

FIG. 2 shows a part of a cross section taken along line AA of FIG. The operation of this embodiment will be described below with reference to FIG.
Steam (for example, a temperature of 400 ° C. and a pressure of 4 MPa) is supplied to the steam introduction space 4 from a steam introduction path (not shown).
The introduced steam supplied to the steam introducing space 4 flows to the outer peripheral portion while passing through the plurality of moving blades 3a to 3d and 5a to 5d (see broken line arrows in FIG. 2). At this time, the minimum gap between adjacent high-pressure side adjacent blades is set to 5 mm, and the blade stage interval is set to 7 mm, (blade stage interval / minimum distance between adjacent high-pressure side adjacent blades) A = 1. Therefore, a high rate utilization rate (about 0.95) is obtained (see FIG. 7).

The pressure of the steam gradually decreases as it goes to the outer peripheral portion, and is converted into rotational energy as, for example, 0.025 MPa as condensate pressure when passing through the outermost moving blade 5d. In such a process of steam flow from the inner periphery to the outer periphery, a rotational force is generated by the action of converting thermal energy into rotational energy.
The steam that has passed through the outermost rotor blade 5d is recovered from the inside of the casing 15 to a condenser (not shown).

  In the present embodiment, by setting the minimum gap between adjacent blades on the high pressure side front stage and the gap between the blade stages to the optimum values, a turbine with a high speed utilization rate of the front stage steam outflow speed can be realized. Compared to conventional examples that have not been devised, it has become possible to use energy more reliably.

  In the present embodiment, an example in which a blade provided with two opposing plate-like members as rotating plates 3 and 5 is used as a moving blade, but a stationary blade with one of the rotating plates as a fixed plate is shown. Even when the structure is provided, the same effect as that of the present embodiment can be obtained by setting the minimum distance between adjacent blades on the high pressure side front stage and the distance between the blade stages to the optimum values according to the present invention.

It is explanatory drawing of the radial flow type steam turbine which concerns on one embodiment of this invention. It is a figure which shows a part of cross section which follows the AA line of FIG. It is explanatory drawing explaining the flow of the steam in a radial flow type steam turbine. It is explanatory drawing of the space | interval (DELTA) r of the blade stage in a radial flow type steam turbine, and the minimum space | interval S between the adjacent blades of a high pressure side front stage. It is explanatory drawing explaining a steam flow when the space | interval (DELTA) r of a blade stage is set narrowly in a radial flow type steam turbine. It is explanatory drawing explaining a steam flow when the space | interval (DELTA) r of a blade stage is set widely in a radial flow type steam turbine. 6 is a graph showing a relationship between a speed utilization factor ε and (blade stage interval / minimum gap between adjacent blades on the high pressure side front stage) A. It is explanatory drawing explaining the outline | summary of the conventional Jungstrom turbine.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Radial flow type steam turbine, 3, 5 rotary plate, 3a-3d, 5a-5d Rotor blade, 9,11 rotating shaft, 17 casing.

Claims (2)

A pair of opposed plate-like members installed substantially perpendicular to the turbine shaft and alternately provided on opposite surfaces of the pair of plate-like members so as to overlap each other in the radial direction from the inner circumference to the outer circumference. A radial flow type steam turbine in which steam flows between the blades from the inner periphery toward the outer periphery, and the interval between the blade stages is the minimum between adjacent blades on the high pressure side front stage. A radial flow type steam turbine characterized by being 0.5 times or more of the interval. The radial flow steam turbine according to claim 1, wherein the interval between the blade stages is not more than 5 times the minimum interval between adjacent blades on the upstream side of the high pressure side.

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