CA2138462A1 - Increased output on full arc admission impulse turbines - Google Patents
Increased output on full arc admission impulse turbinesInfo
- Publication number
- CA2138462A1 CA2138462A1 CA 2138462 CA2138462A CA2138462A1 CA 2138462 A1 CA2138462 A1 CA 2138462A1 CA 2138462 CA2138462 CA 2138462 CA 2138462 A CA2138462 A CA 2138462A CA 2138462 A1 CA2138462 A1 CA 2138462A1
- Authority
- CA
- Canada
- Prior art keywords
- nozzle
- stage
- turbine
- passages
- steam
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 230000000903 blocking effect Effects 0.000 claims abstract description 18
- 238000000034 method Methods 0.000 claims abstract description 17
- 230000000712 assembly Effects 0.000 claims description 14
- 238000000429 assembly Methods 0.000 claims description 14
- 230000000737 periodic effect Effects 0.000 claims description 2
- 238000011144 upstream manufacturing Methods 0.000 claims 1
- 230000005284 excitation Effects 0.000 abstract description 2
- 230000000694 effects Effects 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 5
- 230000006872 improvement Effects 0.000 description 5
- 239000012530 fluid Substances 0.000 description 3
- 101100264655 Enterobacteria phage T4 y12B gene Proteins 0.000 description 2
- 101100264657 Enterobacteria phage T4 y12D gene Proteins 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 2
- 230000035939 shock Effects 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 101001132914 Ambystoma mexicanum Metallothionein Proteins 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000009291 secondary effect Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 210000004894 snout Anatomy 0.000 description 1
- 229910000679 solder Inorganic materials 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Control Of Turbines (AREA)
- Turbine Rotor Nozzle Sealing (AREA)
Abstract
A method and apparatus for improving steam turbine heat rate in a multiple stage steam turbine increases the pressure drop across each stage and increases final feedwater temperature. The method reduces the volumetric flow through each of the stages of the turbine by first determining the optimum pressure drop across a first stage of the turbine, then adjusting the reduced volumetric flow of each succeeding stage to distribute the resultant pressure increase across the multiple stages so as to establish the first stage pressure at about the determined optimum pressure. In one form, the method is implemented by blocking steam flow through at least some spaces between nozzle blades in each stage. The blocked spaces are distributed to avoid impulse excitation of vibration on the rotating blades of each stage.
Description
2138~62 -57, 890 IN~R1;~ OU11 .J . ON FUI~-ARC
AnMT.C:.~ION IMPULSE TIJRRTNl~S
RA"KrDOUND OF THE INVENTION
The present invention relates to steam turbines and, more particularly, to a method for increasing the output power of nuclear powered steam turbines using throttling to limit the steam supply system.
5Most of the nuclear turbines sold or designed before 1967 were found to have considerably higher steam flow capacity than the designers had intended. Because of NRC (Nuclear Regulatory Commission) mandated power output limits on the NSSS (Nuclear Steam Supply System), it was necessary to incur excessive valve throttling to limit cycle heat input to the licensed or warranted level. This excess throttling reduced turbine output. The power loss was less severe on partial-arc admission turbines as only one active control valve was throttling as compared to 15 full-arc admission designs in which all of the control -valves would throttle. In the former case, only a fraction of the total flow was throttled while all of the flow was throttled with the latter design.
Most nuclear turbines have four control valves and in the case of partial-arc designs, each control valve supplies steam to a 25% admission arc of the first or control stage. The first stage in this instance must be an -2~38~62 .
2 57,890 impulse (low reaction) stage. It was found that in many instances the fourth control valve (supplying the 75-100%
admission arc) was practically closed and so this admission arc operated at considerably lower inlet pressure than the other three active arcs. In some instances, not only was the fourth valve completely closed but the third valve (supplying the 50-75% admission arc) was also throttling.
The cause of the higher flow capacity is lower than expected exit pressure of the first stage as well as lower pressure for most of the other stages in the high pressure (HP) turbine section. On the first stage the result was poorer conversion efficiency because of off-design pressure ratio (poorer stage velocity ratio). In addition, the first stage did a greater proportion of the HP section work and the downstream stages did less work.
Since the first stage has lower efficiency than the downstream stages, this further reduced the HP section output.
The reason for the lower stage pressure is two-phase or non-equilibrium effects. The term "supersaturation" has been applied to this phenomenon when it initially occurs. For example, if dry or slightly superheated steam is expanded rapidly in a turbine blade passage, moisture droplets are not formed until a condition is reached which is the equivalent to 2~ to 3% moisture, at which condition the moisture droplets suddenly appear.
This 2% to 3% range is called the Wilson zone. Flow capacity increases up to about 3% compared to the level that would occur if the fluid had been in thermal equilibrium.
Turbine designers considered the effects of the Wilson zone in their first stage passage area calculations.
However, the conventional wisdom was that once moisture appeared, the fluid would be in thermal equilibrium. In reality, the fluid (steam-water mixture) continued to exhibit non-equilibrium effects at moisture levels much larger than 3~. Consequently, all of the stages in the HP
21~8462 3 57,890 section operated at different pressure levels than they were designed for (when thermal equilibrium was believed to exist). As a result, the accumulation of reduced pressure drops on the downstream stages reduced the first stage exit pressure. The reduced first stage exit pressure increased the first stage flow coefficient and so the turbine had excess flow capacity. On full-arc admission turbines, the accumulation of reduced pressure drops also reduced first stage inlet pressure.
In the case of partial-arc designs, the flow capacity is reduced by effectively reducing the active first stage nozzle area by closing a valve and/or reducing the nozzle inlet pressure (by control valve activation) on one of the active arcs with a concurrent output loss. If the first HP stage is a full-arc design, it could be either a reaction or impulse type first stage. In the case of partial-arc designs, only impulse stages are a viable and efficient choice. Partial-arc reaction stages would incur much higher efficiency degradation than impulse stages during operation at flows lower than the maximum value.
A number of reaction turbines have been retrofitted with new blading to restore the balance between the work done by the first stage and the downstream stages.
The solutions have included (1) replacing the stationary blades or nozzles with blades having a smaller throat area (reduced gaging), (2) replacing the entire blade path, rotating and stationary row with blades with smaller heights and/or reduced gaging, (3) reducing the height of the first stage nozzles on partial-arc admission designs and (4) various combinations of these changes. The heat rate/power output improvement as well as the capital cost will increase as a greater number of blade rows are replaced. In addition, the changes which involve rotating blades result in longer duration outages and have added costs associated with replacement energy expenditures.
Stationary blade replacements are an alternative that realizes a major fraction of the potential output ~138A62 4 57,890 improvement at minimal outage time. In other instances, the additional kilowatts achieved by a total HP blade path redesign may warrant the purchase of a new rotor and associated stationary parts. However, each of thése solutions represent a major capital cost investment and substantial turbine downtime.
S~nnM~ OF THE INVENTION
It is an object of the present invention to provide a method and apparatus for improving output of a nuclear powered steam turbine having excess flow capacity above the NSSS limits without incurring the expense and downtime common to prior methods. The present invention incorporates closing off of a selected number of nozzle passages in each stage of the turbine to reduce flow area.
The method increases stage pressure ratio to the level intended by the original design but not achieved due to non-equilibrium effects. In an exemplary form, blocks are placed in the flow passages between some of the nozzle blades. The blocks are distributed about each nozzle assembly but are varied in spacing to avoid in-phase disturbances of the flow. The number of blocks is determined as a function of the percent of excess flow margin and the nozzle area to be blocked.
BRIEF n~CRTPTION OF THE DRAWINGS
For a better understanding of the present invention, reference may be had to the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a simplified cross-sectional view of one form of steam turbine;
FIG. 2 is an axial view of a steam turbine nozzle assembly; and FIG. 3 is a radial view showing a partial section of 2138~62 57,890 nozzle and rotating blade assembly with the present invention.
DETATT~n DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention improves turbine power output and improves efficiency by eliminating throttling of the steam supply to a nuclear powered turbine with impulse blading. Starting with the NRC mandated NSSS cycle heat power input, applicant determines the excess flow capacity of the turbine either by recalculation of turbine flow using present day modeling which accounts for non-equilibrium effects or by actual measurement of pressure drop at each stage. Excess flow capacity as a percentage of total turbine flow capacity establishes the amount by which each nozzle flow area should be reduced to meet the mandated power input.
Before turning to the present invention, reference is first made to FIG. 1 which illustrates one form of a steam turbine 10 having a plurality of axially spaced blade stages comprising nozzle blade assemblies 21 and rotating blade assemblies 23. The turbine 10 includes an outer casing or housing 17 and a rotor 19. The rotating blade assemblies 21 are coupled to the rotor 19 while the nozzle blade assemblies are coupled to an inner casing 27 which is coupled to outer casing 17. Steam enters turbine 10 through inlet snout 25 and flows axially outward through the stages.
Referring now to FIGS. 1 and 2, there are shown an axial view of a nozzle assembly 21 and a partial radial view of nozzle assembIy 21 and rotating blade assembly 23, respectively. Each nozzle assembly 21 is made up of a plurality of circumferentially spaced, fixed nozzle blades 29 having a configuration designed to turn steam entering the assembly 21 in the direction of arrows 31 into an optimum path for reacting against rotating blades 33 of assembly 23. Arrows 32 show steam direction exiting the -2~38~G2 -6 57,890 rotating blades 33.
The circumferential area defined by the blades 29 establishes the turbine flow capacity. Applicant proposes to adjust this flow capacity by blocking selected flow paths between some of the blades 29. By way of example, if the nozzle assembly 21 comprises 120 nozzle passages 35 and the excess flow capacity is about 10 per cent, the flow capacity can be reduced by 10 per cent by blocking twelve of the nozzle passages. FIG. 2 illustrates a blocking device 37 inserted between a pair of adjacent blades 29A
and 29B in a nozzle passage.
In a preferred embodiment, a blocking device 37A
fills the nozzle passage 35 from the leading to trailing edges of blades 29 as is shown. The device may be held in a fixed, assembled position by welding the device to the ~ i ng edges of blades 29A, 29B. Alternatively, the device 37 could extend only between the leading edges of the blades 29A, 29B, as is shown by device 37B. It is preferable to position a blocking device 37 at the leading edge of the blades since steam pressure will tend to urge such device into engagement with the blades rather than trying to dislodge such device if attached to the trailing edge of the blades. However, a device 37 at the trailing edge does offer the advantage of preventing steam flow off the trailing edges of adjacent blades 29 from attempting to flow into the blocked nozzle passage 35 and creating - undesirable turbulence in the steam flow. Thus, use of the device 37A filling the entire flow passage satisfies both desirable features of minimizing turbulence and preventing separation of the device from the nozzle assembly. The alternate device 37B could be a flat plate. Attachment can be by welding, silver solder or mechanical connection.
In a preferred form, the blocking devices 37 are distributed about the nozzle assembly 21 rather than grouped together. Grouping would produce undesirable shock loading on the rotating blades 33 as they pass in and out of the blocked steam flow area. However, it is also not :2138462 7 57,890 desirable to close off nozzle passages in a uniform pattern, e.g., every twelve nozzle passage in the illustrative example. Such an arrangement would produce twelve in-phase distllrh~nces in every revolution of the rotating blade assembly 23 and the in-phase excitation could result in a build-up of vibration in the blades leading to possible failure. Accordingly, it is desirable to arrange the blocked nozzle flow passages such that a varied number of un-blocked passages are between the blocked passages. This arrangement would then produce a non-periodic stimulus and any induced vibratory stress on the blades 33 will be lowered. An example would be to space the blocks 37 such that some blocks 37 have as few as eight passages between adjacent blocks while others are spaced apart by as many as sixteen passages. It is also desirable to vary the position of the blocked passages from stage-to-stage to distribute voids in the steam flow and reduce flow connection at each stage.
A study performed on a 900NW nuclear turbine designed and built before non-equilibrium effects were recognized and before a suitable, predictive correlation was developed, showed significant improvement in power output. The turbine was a partial-arc design having a warranted output slightly above 900MW and a 10% excess flow margin beyond the originally designed 5% level of margin for a total 15% flow margin.
Turning to Table I, it can be seen that the increase in power output for this turbine ranges between 10,680 KW and 13,850 RW over a base flow rate power output of 905,750 RW. For the inventive process, sufficient nozzle passage ways are sealed off on downstream stages to reduce the turbine nozzle area by 10%. The first stage nozzle area is reduced by 10% in one example and by 13.5%
in the other example. The second example actually produced a higher net power increase. The improvement is believed best when all stages are adjusted by partial blockage so as to establish an optimum steam velocity and pressure ratio 2138~62 -8 ` 57,890 at each stage. Further performance improvement is also attained from a secondary effect of achieving a higher final feedwater temperature as a result of the increased extraction pressure. Distributing the pressure increase over multiple stages also places the first stage closer to optimum presæure.
TABLE I
Case Output Increased KW RW
Base (Current State) 905,750 0 First Stage Equiv.Adm.=0.90 (Alt.1) 916,430 10,680 First Stage Equiv.Adm.=0.865(Alt.1) 918,730 12,980 First Stage Equiv.Adm.=O.90(Alt.2) 917,300 11,550 First Stage Equiv.Adm.=0.865(Alt.2) 919,600 13,850 Since the present invention only proposes closing or blocking, on an average for a 10% excess flow capacity, one out of every 12 nozzle passages, the flow from adjacent nozzle passages is believed to be sufficient to fill the resulting void in the flow prior to the steam reaching the rotating blade assembly. Accordingly, shock loading is avoided. In a control stage, the blocked passage would be about 0.5 inches in width with about 5.5 inches of open nozzle passages between the blocked passages.
While the invention has been described in what is presently considered to be a preferred embodiment, many variations and modifications will become apparent to those skilled in the art. Accordingly, it is intended that the - invention not be limited to the specific illustrative embodiment but be interpreted within the full spirit and scope of the appended claims.
AnMT.C:.~ION IMPULSE TIJRRTNl~S
RA"KrDOUND OF THE INVENTION
The present invention relates to steam turbines and, more particularly, to a method for increasing the output power of nuclear powered steam turbines using throttling to limit the steam supply system.
5Most of the nuclear turbines sold or designed before 1967 were found to have considerably higher steam flow capacity than the designers had intended. Because of NRC (Nuclear Regulatory Commission) mandated power output limits on the NSSS (Nuclear Steam Supply System), it was necessary to incur excessive valve throttling to limit cycle heat input to the licensed or warranted level. This excess throttling reduced turbine output. The power loss was less severe on partial-arc admission turbines as only one active control valve was throttling as compared to 15 full-arc admission designs in which all of the control -valves would throttle. In the former case, only a fraction of the total flow was throttled while all of the flow was throttled with the latter design.
Most nuclear turbines have four control valves and in the case of partial-arc designs, each control valve supplies steam to a 25% admission arc of the first or control stage. The first stage in this instance must be an -2~38~62 .
2 57,890 impulse (low reaction) stage. It was found that in many instances the fourth control valve (supplying the 75-100%
admission arc) was practically closed and so this admission arc operated at considerably lower inlet pressure than the other three active arcs. In some instances, not only was the fourth valve completely closed but the third valve (supplying the 50-75% admission arc) was also throttling.
The cause of the higher flow capacity is lower than expected exit pressure of the first stage as well as lower pressure for most of the other stages in the high pressure (HP) turbine section. On the first stage the result was poorer conversion efficiency because of off-design pressure ratio (poorer stage velocity ratio). In addition, the first stage did a greater proportion of the HP section work and the downstream stages did less work.
Since the first stage has lower efficiency than the downstream stages, this further reduced the HP section output.
The reason for the lower stage pressure is two-phase or non-equilibrium effects. The term "supersaturation" has been applied to this phenomenon when it initially occurs. For example, if dry or slightly superheated steam is expanded rapidly in a turbine blade passage, moisture droplets are not formed until a condition is reached which is the equivalent to 2~ to 3% moisture, at which condition the moisture droplets suddenly appear.
This 2% to 3% range is called the Wilson zone. Flow capacity increases up to about 3% compared to the level that would occur if the fluid had been in thermal equilibrium.
Turbine designers considered the effects of the Wilson zone in their first stage passage area calculations.
However, the conventional wisdom was that once moisture appeared, the fluid would be in thermal equilibrium. In reality, the fluid (steam-water mixture) continued to exhibit non-equilibrium effects at moisture levels much larger than 3~. Consequently, all of the stages in the HP
21~8462 3 57,890 section operated at different pressure levels than they were designed for (when thermal equilibrium was believed to exist). As a result, the accumulation of reduced pressure drops on the downstream stages reduced the first stage exit pressure. The reduced first stage exit pressure increased the first stage flow coefficient and so the turbine had excess flow capacity. On full-arc admission turbines, the accumulation of reduced pressure drops also reduced first stage inlet pressure.
In the case of partial-arc designs, the flow capacity is reduced by effectively reducing the active first stage nozzle area by closing a valve and/or reducing the nozzle inlet pressure (by control valve activation) on one of the active arcs with a concurrent output loss. If the first HP stage is a full-arc design, it could be either a reaction or impulse type first stage. In the case of partial-arc designs, only impulse stages are a viable and efficient choice. Partial-arc reaction stages would incur much higher efficiency degradation than impulse stages during operation at flows lower than the maximum value.
A number of reaction turbines have been retrofitted with new blading to restore the balance between the work done by the first stage and the downstream stages.
The solutions have included (1) replacing the stationary blades or nozzles with blades having a smaller throat area (reduced gaging), (2) replacing the entire blade path, rotating and stationary row with blades with smaller heights and/or reduced gaging, (3) reducing the height of the first stage nozzles on partial-arc admission designs and (4) various combinations of these changes. The heat rate/power output improvement as well as the capital cost will increase as a greater number of blade rows are replaced. In addition, the changes which involve rotating blades result in longer duration outages and have added costs associated with replacement energy expenditures.
Stationary blade replacements are an alternative that realizes a major fraction of the potential output ~138A62 4 57,890 improvement at minimal outage time. In other instances, the additional kilowatts achieved by a total HP blade path redesign may warrant the purchase of a new rotor and associated stationary parts. However, each of thése solutions represent a major capital cost investment and substantial turbine downtime.
S~nnM~ OF THE INVENTION
It is an object of the present invention to provide a method and apparatus for improving output of a nuclear powered steam turbine having excess flow capacity above the NSSS limits without incurring the expense and downtime common to prior methods. The present invention incorporates closing off of a selected number of nozzle passages in each stage of the turbine to reduce flow area.
The method increases stage pressure ratio to the level intended by the original design but not achieved due to non-equilibrium effects. In an exemplary form, blocks are placed in the flow passages between some of the nozzle blades. The blocks are distributed about each nozzle assembly but are varied in spacing to avoid in-phase disturbances of the flow. The number of blocks is determined as a function of the percent of excess flow margin and the nozzle area to be blocked.
BRIEF n~CRTPTION OF THE DRAWINGS
For a better understanding of the present invention, reference may be had to the following detailed description taken in conjunction with the accompanying drawings in which:
FIG. 1 is a simplified cross-sectional view of one form of steam turbine;
FIG. 2 is an axial view of a steam turbine nozzle assembly; and FIG. 3 is a radial view showing a partial section of 2138~62 57,890 nozzle and rotating blade assembly with the present invention.
DETATT~n DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention improves turbine power output and improves efficiency by eliminating throttling of the steam supply to a nuclear powered turbine with impulse blading. Starting with the NRC mandated NSSS cycle heat power input, applicant determines the excess flow capacity of the turbine either by recalculation of turbine flow using present day modeling which accounts for non-equilibrium effects or by actual measurement of pressure drop at each stage. Excess flow capacity as a percentage of total turbine flow capacity establishes the amount by which each nozzle flow area should be reduced to meet the mandated power input.
Before turning to the present invention, reference is first made to FIG. 1 which illustrates one form of a steam turbine 10 having a plurality of axially spaced blade stages comprising nozzle blade assemblies 21 and rotating blade assemblies 23. The turbine 10 includes an outer casing or housing 17 and a rotor 19. The rotating blade assemblies 21 are coupled to the rotor 19 while the nozzle blade assemblies are coupled to an inner casing 27 which is coupled to outer casing 17. Steam enters turbine 10 through inlet snout 25 and flows axially outward through the stages.
Referring now to FIGS. 1 and 2, there are shown an axial view of a nozzle assembly 21 and a partial radial view of nozzle assembIy 21 and rotating blade assembly 23, respectively. Each nozzle assembly 21 is made up of a plurality of circumferentially spaced, fixed nozzle blades 29 having a configuration designed to turn steam entering the assembly 21 in the direction of arrows 31 into an optimum path for reacting against rotating blades 33 of assembly 23. Arrows 32 show steam direction exiting the -2~38~G2 -6 57,890 rotating blades 33.
The circumferential area defined by the blades 29 establishes the turbine flow capacity. Applicant proposes to adjust this flow capacity by blocking selected flow paths between some of the blades 29. By way of example, if the nozzle assembly 21 comprises 120 nozzle passages 35 and the excess flow capacity is about 10 per cent, the flow capacity can be reduced by 10 per cent by blocking twelve of the nozzle passages. FIG. 2 illustrates a blocking device 37 inserted between a pair of adjacent blades 29A
and 29B in a nozzle passage.
In a preferred embodiment, a blocking device 37A
fills the nozzle passage 35 from the leading to trailing edges of blades 29 as is shown. The device may be held in a fixed, assembled position by welding the device to the ~ i ng edges of blades 29A, 29B. Alternatively, the device 37 could extend only between the leading edges of the blades 29A, 29B, as is shown by device 37B. It is preferable to position a blocking device 37 at the leading edge of the blades since steam pressure will tend to urge such device into engagement with the blades rather than trying to dislodge such device if attached to the trailing edge of the blades. However, a device 37 at the trailing edge does offer the advantage of preventing steam flow off the trailing edges of adjacent blades 29 from attempting to flow into the blocked nozzle passage 35 and creating - undesirable turbulence in the steam flow. Thus, use of the device 37A filling the entire flow passage satisfies both desirable features of minimizing turbulence and preventing separation of the device from the nozzle assembly. The alternate device 37B could be a flat plate. Attachment can be by welding, silver solder or mechanical connection.
In a preferred form, the blocking devices 37 are distributed about the nozzle assembly 21 rather than grouped together. Grouping would produce undesirable shock loading on the rotating blades 33 as they pass in and out of the blocked steam flow area. However, it is also not :2138462 7 57,890 desirable to close off nozzle passages in a uniform pattern, e.g., every twelve nozzle passage in the illustrative example. Such an arrangement would produce twelve in-phase distllrh~nces in every revolution of the rotating blade assembly 23 and the in-phase excitation could result in a build-up of vibration in the blades leading to possible failure. Accordingly, it is desirable to arrange the blocked nozzle flow passages such that a varied number of un-blocked passages are between the blocked passages. This arrangement would then produce a non-periodic stimulus and any induced vibratory stress on the blades 33 will be lowered. An example would be to space the blocks 37 such that some blocks 37 have as few as eight passages between adjacent blocks while others are spaced apart by as many as sixteen passages. It is also desirable to vary the position of the blocked passages from stage-to-stage to distribute voids in the steam flow and reduce flow connection at each stage.
A study performed on a 900NW nuclear turbine designed and built before non-equilibrium effects were recognized and before a suitable, predictive correlation was developed, showed significant improvement in power output. The turbine was a partial-arc design having a warranted output slightly above 900MW and a 10% excess flow margin beyond the originally designed 5% level of margin for a total 15% flow margin.
Turning to Table I, it can be seen that the increase in power output for this turbine ranges between 10,680 KW and 13,850 RW over a base flow rate power output of 905,750 RW. For the inventive process, sufficient nozzle passage ways are sealed off on downstream stages to reduce the turbine nozzle area by 10%. The first stage nozzle area is reduced by 10% in one example and by 13.5%
in the other example. The second example actually produced a higher net power increase. The improvement is believed best when all stages are adjusted by partial blockage so as to establish an optimum steam velocity and pressure ratio 2138~62 -8 ` 57,890 at each stage. Further performance improvement is also attained from a secondary effect of achieving a higher final feedwater temperature as a result of the increased extraction pressure. Distributing the pressure increase over multiple stages also places the first stage closer to optimum presæure.
TABLE I
Case Output Increased KW RW
Base (Current State) 905,750 0 First Stage Equiv.Adm.=0.90 (Alt.1) 916,430 10,680 First Stage Equiv.Adm.=0.865(Alt.1) 918,730 12,980 First Stage Equiv.Adm.=O.90(Alt.2) 917,300 11,550 First Stage Equiv.Adm.=0.865(Alt.2) 919,600 13,850 Since the present invention only proposes closing or blocking, on an average for a 10% excess flow capacity, one out of every 12 nozzle passages, the flow from adjacent nozzle passages is believed to be sufficient to fill the resulting void in the flow prior to the steam reaching the rotating blade assembly. Accordingly, shock loading is avoided. In a control stage, the blocked passage would be about 0.5 inches in width with about 5.5 inches of open nozzle passages between the blocked passages.
While the invention has been described in what is presently considered to be a preferred embodiment, many variations and modifications will become apparent to those skilled in the art. Accordingly, it is intended that the - invention not be limited to the specific illustrative embodiment but be interpreted within the full spirit and scope of the appended claims.
Claims (11)
1. A method for increasing power output of a steam turbine in which cycle heat input is limited to a predetermined value and the turbine has throttle flow capacity in excess of the limited value of heat input, the method comprising the steps of:
calculating the percentage of excess flow capacity for the turbine above the heat input limit;
determining the number of nozzle passages in each of a plurality of nozzle assemblies corresponding to the calculated percentage of excess flow capacity; and blocking steam flow through the number of passages in each assembly obtained by the step of determining.
calculating the percentage of excess flow capacity for the turbine above the heat input limit;
determining the number of nozzle passages in each of a plurality of nozzle assemblies corresponding to the calculated percentage of excess flow capacity; and blocking steam flow through the number of passages in each assembly obtained by the step of determining.
2. The method of claim 1 wherein the step of blocking includes the step of inserting a blocking device in selected nozzle passages between adjacent nozzle blades.
3. The method of claim 2 wherein the step of blocking further includes the step of selecting nozzle passages in spaced relationship about each nozzle assembly.
4. The method of claim 3 wherein the step of selecting includes the step of varying the number of unblocked passages between the blocked passages to establish a non-periodic distribution of blocked passages.
5. The method of claim 4 wherein the step of selecting includes the step of changing the distribution of block passages from stage-to-stage.
6. The method of claim 5 wherein the step of calculating includes the step of measuring pressure drop at each stage of the turbine to determine excess flow capacity.
7. A steam turbine comprising:
a plurality of rotating blade assemblies;
a plurality of nozzle blade assemblies, each of the nozzle blade assemblies being positioned upstream of a corresponding one of the rotating blade assemblies, each of the nozzle blade assemblies comprising a plurality of circumferentially spaced fixed blades for directing steam into the associated one of the rotating blade assemblies at an optimal angle, the spaced blades of the nozzle blade assemblies defining a plurality of steam passages between the spaced blades; and blocking devices positioned in selected ones of the steam passages of each of the nozzle blade assemblies for increasing steam pressure drop across each stage, said blocking devices being distributed about each nozzle assembly in a non-uniform pattern.
a plurality of rotating blade assemblies;
a plurality of nozzle blade assemblies, each of the nozzle blade assemblies being positioned upstream of a corresponding one of the rotating blade assemblies, each of the nozzle blade assemblies comprising a plurality of circumferentially spaced fixed blades for directing steam into the associated one of the rotating blade assemblies at an optimal angle, the spaced blades of the nozzle blade assemblies defining a plurality of steam passages between the spaced blades; and blocking devices positioned in selected ones of the steam passages of each of the nozzle blade assemblies for increasing steam pressure drop across each stage, said blocking devices being distributed about each nozzle assembly in a non-uniform pattern.
8. The steam turbine of claim 7 wherein the blocking devices in each nozzle assembly are arranged in a pattern different from a pattern of blocking devices in adjacent nozzle assemblies.
9. The steam turbine of claim 8 wherein the blocking devices substantially fill each passage from leading edge to trailing edge of adjacent nozzle blades.
10. The steam turbine of claim 8 wherein the blocking devices comprise a plate extending between leading edges of nozzle blades on each side of a nozzle passage.
11. A method of improving steam turbine heat rate in a multiple stage steam turbine by increasing turbine pressure ratio of each stage and increasing final feedwater temperature, the method comprising the steps of:
reducing the volumetric flow through each of the stages of the turbine;
determining the optimum pressure drop across a first stage of the turbine; and adjusting the reduced volumetric flow of each succeeding stage to distribute a pressure increase affected by said step of reducing to establish first stage pressure at about the determined optimum pressure.
reducing the volumetric flow through each of the stages of the turbine;
determining the optimum pressure drop across a first stage of the turbine; and adjusting the reduced volumetric flow of each succeeding stage to distribute a pressure increase affected by said step of reducing to establish first stage pressure at about the determined optimum pressure.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US16925493A | 1993-12-20 | 1993-12-20 | |
| US169254 | 1993-12-20 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2138462A1 true CA2138462A1 (en) | 1995-06-21 |
Family
ID=22614850
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2138462 Abandoned CA2138462A1 (en) | 1993-12-20 | 1994-12-19 | Increased output on full arc admission impulse turbines |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH07208108A (en) |
| CA (1) | CA2138462A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6386829B1 (en) | 1999-07-02 | 2002-05-14 | Power Technology, Incorporated | Multi-valve arc inlet for steam turbine |
| EP3112598A1 (en) * | 2015-06-29 | 2017-01-04 | General Electric Company | Steam turbine nozzle segment for partial arc application, related assembly and steam turbine |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140105720A1 (en) * | 2012-10-11 | 2014-04-17 | Krishna Kumar Bindingnavale Ranga | Method and a system for adjusting nozzle area in steam turbines |
-
1994
- 1994-12-19 CA CA 2138462 patent/CA2138462A1/en not_active Abandoned
- 1994-12-20 JP JP33559694A patent/JPH07208108A/en not_active Withdrawn
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6386829B1 (en) | 1999-07-02 | 2002-05-14 | Power Technology, Incorporated | Multi-valve arc inlet for steam turbine |
| EP3112598A1 (en) * | 2015-06-29 | 2017-01-04 | General Electric Company | Steam turbine nozzle segment for partial arc application, related assembly and steam turbine |
| CN106285789A (en) * | 2015-06-29 | 2017-01-04 | 通用电气公司 | Steam turbine barrier film nozzle segment and diaphragm section thereof and steam turbine |
| CN106285789B (en) * | 2015-06-29 | 2020-07-28 | 通用电气公司 | Steam turbine diaphragm nozzle segment, diaphragm segment thereof and steam turbine |
| US10927688B2 (en) | 2015-06-29 | 2021-02-23 | General Electric Company | Steam turbine nozzle segment for partial arc application, related assembly and steam turbine |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07208108A (en) | 1995-08-08 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2381484C (en) | Gas turbine cooled blade | |
| US11852165B2 (en) | Biased passages for turbomachinery | |
| EP0649975B1 (en) | Metering of cooling air in turbine blades | |
| DE69601283T2 (en) | Flow directing device for a gas turbine engine | |
| EP0170938B1 (en) | Blade and seal clearance optimization device for compressors of gas turbine power plants, particularly of gas turbine jet engines | |
| US7442008B2 (en) | Cooled gas turbine aerofoil | |
| EP0799972B1 (en) | A root attachment for a Turbomachine blade | |
| US9151173B2 (en) | Use of multi-faceted impingement openings for increasing heat transfer characteristics on gas turbine components | |
| EP1798379A2 (en) | Countercooled turbine nozzle vane | |
| US20080199306A1 (en) | Turbomachine casing with treatment, a compressor, and a turbomachine including such a casing | |
| US20080253898A1 (en) | Damper configured turbine blade | |
| US6468031B1 (en) | Nozzle cavity impingement/area reduction insert | |
| JPH076520B2 (en) | Device for optimizing radial blade clearance in an axial compressor of a gas turbine engine | |
| WO1995030075A1 (en) | Variable thickness isogrid case | |
| CA2219421C (en) | Combustion chamber having integrated guide blades | |
| JPH05113101A (en) | Impulse steam turbine with drum type rotor | |
| EP1144808B1 (en) | Method of cooling a combustion turbine | |
| DE112007001870T5 (en) | steam turbines | |
| CA2138462A1 (en) | Increased output on full arc admission impulse turbines | |
| US20020182081A1 (en) | Device for fastening a moving blade to the rotor of a turbomachine | |
| KR20170085956A (en) | Gas turbine blade and manufacturing method | |
| JP2009019631A (en) | Steam turbine blade | |
| US3734645A (en) | Turbine blade assembly | |
| US6270315B1 (en) | Highly loaded turbine blading | |
| CA1229306A (en) | Compressor diaphragm box seal |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Dead |