JPS61275504A - Mixed pressure turbine - Google Patents

Abstract

PURPOSE:To significantly lessen total pressure loss in a mixed pressure turbine by arranging a set of shutter members for shutting and opening a secondary vapor passage near the outlet end of the secondary vapor passage connected at a specified angle to the primary vapor passage of the turbine. CONSTITUTION:A mixed pressure turbine has a primary vapor passage 5 for allowing primary vapor A to flow in form the first stage 4 of the turbine. A secondary vapor passage 9 smoothly sloping to the downstream of and communicating with the passage 5 is formed at an intermediate stage of the turbine. The slope of the secondary vapor passage 9 is set so that the angle alpha formed between an extension line of an outlet end 9a of the passage 9 and the central axis of a turbine rotor falls within a range between zero and pi/3: 0<=alpha<=pi/3. In this case, a shutter member 19 consisting of both a ring-shaped rotary plate 20 projecting from a nozzle diaphragm outer ring 18 located on the downstream side of the passage 9 into the passage 9 and a ring-shaped fixed plate 21 projecting from a casing 10 located on the downstream side of the passage 9 is arranged at the said outlet end 9a so that the passage 9 can be opened or closed.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a mixed pressure turbine that combines primary steam introduced from the first stage of the turbine with secondary steam introduced from an intermediate stage of the turbine. Concerning the structure near the steam confluence.

(Technical background of the invention and its problems) In geothermal power plants, when the well is relatively shallow and the pressure and temperature of the geothermal steam is not very high, a two-stage flash using a mixed pressure turbine is used to effectively utilize the geothermal steam. Geothermal turbines are widely used.

As shown in FIG. 12, this two-stage flash type geothermal turbine extracts geothermal steam from a well 1 and separates this geothermal steam into hot water and saturated steam in a primary steam flash tank 2. This saturated steam passes through the water/fish trachea 3 to the water/fish air from the turbine first stage 4 to the primary steam passage 5.
is flowing into the country.

The separated hot water is sent to a secondary steam flash tank 6 whose pressure is lower than that of the flash tank 2, where it is flashed and separated into saturated steam and hot water. This hot water is returned to the reduction well 7, and the saturated steam passes through the secondary steam pipe 8 and flows as secondary steam B into the secondary steam passage 9 in the middle stage of the turbine.

The secondary steam B that has flowed out of the secondary steam passage 9 flows into the primary steam passage 5 as shown in FIG. 13, and joins the water that has already worked in the upstream stage. At this time, the secondary steam B is considerably smaller than the axial flow velocity of the primary steam at the confluence point, so it does not completely mix with the primary steam, and on the downstream side of the confluence point, the secondary steam flows toward the casing 10. -Waterfish air rotor 1191. In other words, it flows along the root side of the nozzle 12 and the blades 13 and performs their respective work. In this way, by adopting a mixed pressure turbine, geothermal energy can be effectively utilized in the form of primary steam and secondary steam.

In a power generation plant, partial load operation of the turbine is required in response to fluctuations in electric power demand m, and in a mixed pressure turbine, the amount of secondary steam is adjusted during this partial load operation. However, conventional mixed pressure turbines suffer from problems such as total pressure loss and damage to turbine blades due to a decrease in the amount of secondary steam.

This occurs due to the reasons detailed below. When the amount of secondary steam becomes zero due to partial load operation as shown in FIG.
Because there is no inflow of secondary steam, it expands rapidly.

However, the water/fish air A cannot follow such a rapid expansion of the primary steam passage, and a large separation area 14 with vortices is generated at this expansion portion. Further, due to this reaction, a separation region 15 or a reverse flow region accompanied by a vortex is generated near the root of the blade 13 on the downstream side of the merging point. These double-headed ti
Due to R14°15, a large total pressure loss occurs, and at the same time, the flow becomes non-uniform in the circumferential direction, and an exciting force is generated on the blade 13, damaging the blade and shortening its life. Figure 15 shows the nozzle 12i:i when there is no inflow of secondary steam.
The graph shows the subsequent dynamic pressure distribution, where the horizontal axis represents the circumferential position θ, and the vertical axis represents the dynamic pressure C1 immediately after the nozzle 12, which has been made dimensionless using the average value of the dynamic pressure immediately before the confluence as the reference value. It represents. In the blade root part shown in Actual 1i1R and the tip part shown by the broken line T, the dynamic pressure decreases significantly compared to the center of the flow path shown by the dashed line P, and the fluctuation in the circumferential direction is large, and these parts become the separation area. It can be seen that a vortex is generated.

The problems that occur when there is no inflow of secondary steam due to partial load operation have been described above, but in conventional mixed pressure turbines, the following problems also occurred when secondary steam was flowing in.

In a conventional mixed pressure turbine, as shown in Fig. 13, secondary steam B flows into primary steam A at a nearly right angle, and the speed of this inflow is non-uniform in the circumferential direction. A secondary flow accompanied by a vortical motion is generated, and most of the kinetic energy of the secondary steam is consumed in a direction perpendicular to the secondary airflow, resulting in a large energy loss. Furthermore, although the flow velocity of the secondary steam B is slower than that of the primary steam, it is approximately 60 m/s to 1 at the confluence point.
00 m/S, and *m can reach 50% of the primary steam flow rate in some cases, so the secondary steam B from the secondary steam velocity path 9 can follow flow path changes of up to 90°. First, a separation region wt16 is generated in the boundary layer between the nozzle diaphragm outer ring and the casing 10, causing vortex loss. Figure 16 shows the dynamic pressure distribution downstream of the nozzle immediately after the confluence when the secondary steam flow is -30% of the water, fish, and air, and the solid line R
represents the dynamic pressure at the root, where the total pressure loss due to the collision between water, fish, and secondary steam is significant, and 90
This shows that the static pressure increases due to the direction change of the secondary steam over a degree of degree, and a large dynamic pressure drop occurs. Broken line ■
represents the dynamic pressure at the tip portion, and shows that the dynamic pressure is lowered due to the peeled region 16. -Linear 11P
indicates the dynamic pressure at the center. The root part R, tip part T, and center part P all have large fluctuations in the circumferential direction of the dynamic pressure. This is due to the fact that the circumferential non-uniformity of the airflow is amplified. Such non-uniformity in the circumferential direction of the speed generates an excitation force on the blade, causing self-excited vibration (flutter) and the like to shorten the life of the blade.

Furthermore, there is a problem in that the steam pressure in the two-stage flash tank 6 increases by the total pressure loss at the confluence point of the secondary steam, resulting in a decrease in the amount of flash steam.

(Objective of the Invention) Therefore, the object of the present invention is to provide a mixed pressure turbine that significantly reduces the total pressure loss of the flow and also equalizes the circumferential velocity of the flow, thereby greatly improving the efficiency. .

[Summary of the invention]

In order to achieve this object, the first invention of the present application provides a primary steam passage formed along the turbine rotor through which primary steam flowing from the first stage of the turbine flows to rotate the turbine, and a primary steam passage formed in the middle stage of the turbine. , a mixed pressure turbine comprising a secondary steam passage connected at a predetermined angle to the primary steam passage at an outlet end and introducing secondary steam into the primary steam passage from an intermediate stage of the turbine; The present invention is characterized by comprising a shielding member provided near the end A1 to open and close the secondary steam passage. The angle α between the extended line of this slope and the rotor center line is 0<
It is characterized in that α≦π/3 is satisfied.

[Embodiments of the invention]

Hereinafter, one embodiment of the mixed pressure turbine according to the present invention will be described as a 12th embodiment.
The explanation will be made with reference to FIGS. 1 to 11, in which the same parts as in FIGS. 1 to 14 are denoted by the same reference numerals.

In FIGS. 1 and 2, water, fish, and air A flows into the primary steam passage 5 from the first stage 4 of the turbine. This primary steam passage 5
is formed in a ring shape along the rotor 11 between the turbine casing 10 and the turbine rotor 11. The secondary steam passage 9 is provided in the middle stage of the turbine, and this passage 9
The outlet portion 9a is formed by the casing 10, an upstream nozzle diaphragm outer ring 17J3, and a downstream nozzle diaphragm outer ring 18 that sandwich the passage 9 in the axial direction. The outlet portion 9a of the secondary steam passage 9 is smoothly inclined toward the downstream side of the primary steam passage 5.

This inclination means that the angle α (hereinafter referred to as secondary steam outflow angle) between the extension line of the outlet portion 9a and the central axis of the rotor 11 is 0.
It is determined to satisfy <α≦π/3.

A shielding member 19 that can open and close the secondary steam passage 9 is provided at the secondary steam passage outlet 9a.

This shielding member 19 includes a ring-shaped rotary plate 20 discharged into the passage 9 from the nozzle diaphragm outer ring 18 on the downstream side of the passage 9.
and a ring-shaped fixing plate 21 protruding into the passage 9 from the casing 10 on the downstream side of the secondary steam passage 9.

As shown in FIGS. 3 to 5, the rotating plate 20 is composed of a plurality of rectangular protrusions 20a arranged at equal angular intervals, and adjacent to the circumferential length 11 of these protrusions 20a. The gap between the projecting pieces 20a, that is, the circumferential length 92 of the opening is determined to be approximately equal to the circumferential length 92 of the opening.

The fixed plate 21 also has the same shape as the rotary plate 20 and is composed of a plurality of rectangular protrusions 21a spaced at equal intervals. Further, the rotating plate 20 and the fixed plate 21 overlap each other in the flow direction of the secondary steam. Therefore, when the rotary plate 20a and the protrusion 21a of the fixed plate 21 completely overlap as shown in FIGS. 1 and 4, about 50% of the total cross-sectional area of the secondary steam passage 9 is opened, and the second Both projecting pieces 20a and 21 as shown in the figure and FIG.
When the passages 8 and 8 are alternated, the passage 9 is completely shielded and becomes a total square.

The downstream nozzle diaphragm outer ring 18 immediately after the secondary steam passage 9 is rotatably supported in the circumferential direction by the circumferential groove 22 of the casing 10, unlike the other nozzle diaphragm outer rings. To explain this in detail, the groove 22 of the casing 10
A plurality of rollers 23 and 24 are attached to the outer circumferential wall and the downstream wall at approximately equal angular intervals in the circumferential direction.

The downstream outer ring 18 is rotatably supported in the circumferential direction by these rollers 23 and 24. As shown in FIG. 3, sawtooth grooves 25 are formed on the outer peripheral surface of the outer ring 18 at equal angular intervals. The pitch of the grooves 25 is the same as that of the protrusion 20a.

It is set at half the pitch of 21a. Casing 1
For 0? A rotation prevention member 26 that can be secured to the lN 23 is provided, and the rotation prevention member 26 is slidable and tight in the longitudinal direction from the outside of the casing, and when engaged with the groove 25, prevents rotation of the outer ring 18 and prevents the outer ring 18 from rotating. Allow rotation when exiting from. The positional relationship between the rotation preventing member 26 and the outer ring 18 is such that when the member 26 engages with the groove 25, for example, the protrusions 20a and 218 completely overlap, that is, they are in phase, and the secondary steam passage 9 is Open and 11' next to it again! 25, the protrusions 20a and 218 are in opposite phase and are designed to block the passage 9.

Further, the shielding member 19 of the passage outlet portion 9a forms a part of the outer circumferential wall of the temporary steam passage 5 when in the full n state, and is inclined outwardly toward the downstream side. The primary steam passage 5 from the stage vane 27 to the stage nozzle 12 immediately after the passage 9 is gradually expanded. Shielding member 19 from the front stage blade 27 to the rear stage nozzle 12
The angle of inclination of the outer peripheral wall of the primary steam passage including That is, the axial coordinates X of the outlet of the blade 27 and the inlet of the nozzle 12 are respectively XB.

When XA is the inclination angle at an arbitrary point of the outer peripheral wall in the meridian plane, the average inclination angle β (hereinafter referred to as the average opening angle) is defined as follows.

Here, the integral of the numerator represents the line integral along the outer peripheral wall cut along the meridian plane. The inclination of the outer peripheral wall including the shielding member 19 is determined as O≦ using the average opening angle β defined as above.
It is determined to satisfy β≦0.3π.

Hereinafter, the operation of the mixed pressure turbine according to the present invention will be explained.

(a>When the shielding member is fully m) As shown in FIGS. 1 and 4, when the rotating plate 20 and the fixed plate 21 are in phase and the shielding member 19 is in the full state,
While passing through the secondary steam passage 9, the secondary steam B gradually changes direction along the secondary steam passage 9, and the shielding member 1 shown in FIG.
When passing through a large number of equally spaced openings 19a of 9, it is made uniform in the circumferential direction and gently merges into the water Δ with an outflow angle α of less than □.

As a result, the occurrence of vortices and separation is suppressed, the total pressure loss at the merging section is significantly reduced, and there is also little circumferential flow fluctuation, which reduces the unsteady fluid force applied to the blades downstream of the merging section, thereby extending the life of the blades. It can be extended by about 1.5 to 2.0 times.

Furthermore, since the secondary steam merges at an inlet angle of less than π □, the secondary steam with low humidity flows on the tip side of the blade without immediately mixing with the secondary steam.
The highly humid primary steam flows along the root side of the blade. Therefore, erosion of the tip of the blade due to wet steam is reduced.

The above-mentioned effects will be described in Example 3 below using graphs.

FIG. 6 is a graph showing the results of a basic test using a channel model, in which the horizontal axis represents the secondary steam outflow angle α and the vertical axis represents the total pressure loss coefficients a and b. The total pressure loss due to merging is h,
The average velocity after merging is v2°.The cross-sectional area of each of the secondary steam and secondary steam is A, A, 2. - Water and fish air flow rate 01. When the secondary steam flow mountain is Q2, the steam coefficients a and b are defined by the following equations.

Since the coefficients a and b are functions of m, FIG. 6 shows a and b when m-2. As can be seen from this graph, when the secondary steam outflow angle α is 0 to □, the coefficients a and b are relatively small, and therefore the total pressure loss is also small during this period. Since the coefficients a and b that exceed the threshold value rise rapidly, the total pressure loss also rises rapidly. The total pressure loss is at least half or less for all water sources where the outflow angle is 0≦α≦π/3.

FIG. 7 shows the change in the circumferential direction of the dynamic pressure distribution of direct penetration into the nozzle 12 when the flow rate of secondary steam B is 30% of the primary steam A in the steam example, and shows the change in the circumferential direction of the dynamic pressure distribution directly intruding into the nozzle 12. It can be seen that the dynamic pressure loss is reduced compared to the pressure type turbine, and the fluctuation in the circumferential direction is also sufficiently small.

Figure 8 shows the unsteady fluid force that is the cause of vibrations applied to the blade 13, and the horizontal axis represents the height direction IH of the blade 13.
, and the vertical axis is the steady fluid force F.

" Let us take the dimensionless unsteady fluid force Fu.

The mixed pressure turbine of this embodiment, indicated by the actual IN, is compared to the conventional mixed pressure turbine of FIG. 12, indicated by the broken line 0. (b) Total m of the shielding member.

When it becomes necessary to stop the secondary steam B and reduce the load during operation, the rotation blocking member 26 shown in FIG. 3 is temporarily pulled up to disengage the nozzle diaphragm outer ring 18 from the nozzle 25. The reaction force of the steam flowing out is always acting on the nozzle 12, and the circumferential component of this reaction force becomes a torque that rotates the nozzle diaphragm outer ring 18 in the opposite direction to the rotation of the rotor 11. Therefore, when the rotation blocking member 26 and the ring 25 are disengaged, the nozzle diaphragm outer ring 18 rotates the rotating plate 20, which has rotated in the opposite direction to the rotor, relative to the fixed plate 21. When this rotation is completed by one pitch of the groove 25, the rotation of the outer ring 18 is prevented by engaging the rotation prevention member 26 with the groove 25, and the positional relationship between the rotary plate 20 and the fixed plate 21 becomes reversed. The shielding member 19 is fully closed as shown in FIGS. 2 and 5.

As a result, the secondary steam passage 9 is completely shielded at the outlet portion 9a, and the average opening angle β is 0.
A gradually expanding flow path of 3π or less is formed. When the primary steam A that has flowed out of the front stage vane 27 passes through this gradually expanding flow path, it spreads gently without creating any eddies or separation, and flows into the rear stage nozzle 12. Of course, since the secondary steam passage 9 is completely shielded, the secondary steam will not leak into the secondary steam passage 9 and cause any loss.

FIG. 9 shows the relationship between the average frontage angle β of the outer peripheral surface of the primary steam passage and the flow total pressure loss coefficient.The total pressure loss coefficient is within the average frontage angle range of 0 to 0. At 3π, it is very small, but when it exceeds 0.3π, it increases rapidly, especially at βζ□, which corresponds to the conventional mixed pressure turbine shown in FIG. It turns out that it has more than doubled.

FIG. 10 shows the nozzle 12 when the shielding member 19 is fully closed.
This figure shows the distribution of dynamic pressure in the downstream direction of the turbine.The drop in dynamic pressure at the root section R and tip section T is significantly reduced compared to the conventional turbine shown in Fig. 15, and circumferential fluctuations are also sufficiently small. I know that there is.

This is considered to be because the occurrence of the peeled areas 14.degree. 15 in FIG. 14 is prevented in this example.

Figure 11 shows the radial distribution of the unsteady fluid force applied to the blade 13 when the shielding member is fully closed.
In this embodiment, the dotted line 0-C is 5, which is indicated by 1N. It can be seen that the excitation force to the blade 13 is significantly reduced.

Note that the rotation prevention member 26 that is operated when switching the shielding member 19 from fully open to fully open or from fully open to fully closed includes:
This is biased downward, that is, in the direction of engagement with the full 25'.
It is recommended to attach a spring that As a result, the timing for lowering the rotation blocking member 26 to engage with the groove 25 does not have to be exactly aligned with the completion of rotation of the outer ring 18 by one pitch of full 25, but can be set much earlier than that. be able to.

In the above-described embodiment, the nozzle diaphragm outer ring 18 is made rotatable, the rotary plate 20 is fixedly attached to the nozzle diaphragm outer ring 18, and the rotary plate 20 is rotated using the reaction force of the working steam. However, the present invention is not limited to this, and the nozzle diaphragm outer ring 18 may be fixed, the rotary plate 20 may be configured to be rotatable independently of the outer ring 18, and may be rotationally driven by a pulse motor or the like. Further, a drift plate or a guide vane may be provided in the secondary steam passage 9 in order to promote direction change of the secondary steam and make the flow more uniform in the circumferential direction.

〔Effect of the invention〕

As is clear from the above description, according to the first invention,
A shielding member that can open and close the secondary steam passageway is provided near the outlet of the secondary steam passageway, so by fully closing the shielding member and shielding the secondary steam passageway during partial load operation, secondary steam can be It is possible to prevent leakage to the secondary steam passage, and also to prevent turbulence of the primary steam at the connection with the secondary steam passage, and to significantly reduce total pressure loss.

Further, according to the second invention, since the inclination angle α near the outlet of the secondary steam passage is set to 0≦α≦π/3, the secondary steam smoothly merges with the primary steam, reducing the total pressure loss. can be significantly reduced,
Also, the excitation force applied to the blades can be reduced. Furthermore, since secondary steam with low humidity flows through the tips of the blades, erosion of the blades caused by wet steam can be prevented.

[Brief explanation of drawings]

Figures 1 and 2 are longitudinal sectional views showing an embodiment of the mixed pressure turbine according to the present invention, with Figure 1 showing the shield plate fully open and Figure 2 showing the shield plate fully closed. There is. Third
The figure is a cross-sectional view showing the relationship between the nozzle diaphragm outer ring and the rotation prevention member in Figure 1, and Figures 4 and 5 are sectional views taken along lines IV--IV in Figure 1 and v-vsi in Figure 2, respectively. 12 is a schematic diagram showing a conventional two-stage flash geothermal turbine, and FIGS. 13 and 14 are graphs showing the fluid characteristics of the present invention. 15 and 16 are graphs showing the fluid characteristics of the turbine shown in FIG. 12. FIGS. 4... Turbine first stage, 5... Primary steam passage, 9...
...Secondary steam passage, 9a...Secondary steam passage outlet part, 1
9... Shielding member, 20... Rotating plate, 21... Fixed plate, A...-water vapor, B... secondary steam. Applicant's representative Setsu Ino Figure 1 Figure 2 Figure 3 Figure 6 Figure 7 Blade height IHr Figure 8 Average aperture angle β Figure 9 Figure 1O Figure 11 Figure 13

Claims (1)

[Claims] 1. A primary steam passage formed along the turbine rotor, through which primary steam flowing from the first stage of the turbine flows to rotate the turbine, and a primary steam passage formed in the middle stage of the turbine,
In a mixed pressure turbine comprising a secondary steam passage connected at a predetermined angle to the primary steam passage at an outlet end and introducing secondary steam into the primary steam passage from an intermediate stage of the turbine, near the exit end of the secondary steam passage. A mixed pressure turbine, characterized in that it is provided with a shielding member that opens and closes the secondary steam passage. 2. The mixed pressure turbine according to claim 1, wherein the angle α between the extension line of the secondary steam passage and the rotor center axis satisfies 0≦α≦π/3. 3. The shielding member forms an outer circumferential wall of the primary steam passage when the secondary steam passage is shielded, and this outer circumferential wall is arranged at the center of the rotor so that the primary steam passage expands toward the downstream side. The mixed pressure turbine according to claim 2, wherein the turbine is inclined with respect to the axis, and the average inclination angle @β@ satisfies 0≦β≦0.3π. 4. The shielding member is disposed in the secondary steam passage,
The present invention includes a ring-shaped fixing plate having a plurality of openings at predetermined intervals, and a rotatable ring-shaped rotating plate arranged so as to overlap this fixing plate and having a plurality of openings corresponding to the fixing plate openings, 2. The mixed pressure turbine according to claim 1, wherein the secondary steam passage is opened and closed by rotation of a rotating plate. 5. The rotary plate is fixed to the nozzle diaphragm outer ring immediately after the secondary steam passage, and the nozzle diaphragm outer ring is supported by the turbine casing so as to be rotatable in the circumferential direction, and is supported by a rotation prevention member that can be operated from outside the turbine. 5. The mixed pressure turbine according to claim 4, wherein the mixed pressure turbine is prevented from rotating. 6. A primary steam passage formed along the turbine rotor and flowing through to rotate the primary steam turbine that flows in from the first stage of the turbine, and a primary steam passage formed in the middle stage of the turbine and connected to the primary steam passage at the outlet end at a predetermined angle. is,
In a mixed pressure turbine equipped with a secondary steam passage that introduces secondary steam from a stage midway through the turbine to the primary steam passage, the vicinity of the outlet of the secondary steam passage is directed toward the downstream side of the primary steam passage. The angle α between the extension line of this slope and the rotor center line is 0<α≦π/3.
A mixed pressure turbine characterized by satisfying the following.