CN114718665A

CN114718665A - Turboset with double-channel adjusting stage, calculation method and operation method

Info

Publication number: CN114718665A
Application number: CN202210214176.1A
Authority: CN
Inventors: 王卫良; 吕俊复
Original assignee: Tsinghua University; Jinan University
Current assignee: Tsinghua University; Jinan University
Priority date: 2022-03-04
Filing date: 2022-03-04
Publication date: 2022-07-08
Anticipated expiration: 2042-03-04
Also published as: CN114718665B

Abstract

The invention provides a steam turbine set with a double-channel adjusting stage, a calculation method and an operation method_xAt full load]Under the high load working condition, the tapered nozzle group is opened, and the machine group runs at [ L ]_x0,L_x]When the working condition is medium or low load, the convergent-divergent nozzle group is opened, steam expands in the convergent-divergent nozzle group and accelerates to supersonic speed, the operating pressure is greatly increased to the maximum allowable pressure, the operating efficiency is improved, and the pressure loss is reduced; the tapered nozzle group is arranged in the outer ring nozzle channel by utilizing the characteristic that the flow area of the inner ring nozzle channel is smaller than that of the outer ring nozzle channelThe convergent-divergent nozzle group is arranged in the inner ring nozzle channel, and when the nozzle group is switched under the working condition of high load and low load, the partial steam admission degree of the convergent-divergent nozzle group in the inner ring nozzle channel is greatly reduced, and the regulation stage efficiency is improved.

Description

Turboset with double-channel adjusting stage, calculation method and operation method

Technical Field

The invention belongs to the technical field of steam turbines, and particularly relates to a steam turbine set with a double-channel adjusting stage, a calculation method and an operation method.

Background

The strategy of 'double carbon' promotes the construction of a novel power system taking new energy as a main body, and with the large-scale grid connection of new energy power such as photovoltaic power, wind power and the like with random fluctuation, basic power taking coal-fired thermal power as a main body is forced to participate in deep peak shaving comprehensively. The design of the coal-fired thermal power generating unit mainly considers the operating efficiency under the rated load working condition, the generating efficiency of the unit under the medium-low load working condition in the deep peak regulation process is rapidly deteriorated, compared with the rated load working condition, the coal consumption of the conventional coal-fired thermal power generating unit under the 30% rated load working condition is increased by 30-40 g/kW.h, the direct reason is that under the operation mode of 'constant-sliding-constant' of main steam pressure, the main steam pressure under the medium-low load is greatly reduced, the circulation efficiency of a thermodynamic system is directly reduced, and meanwhile, the through-flow working efficiency of a steam turbine body is also increased

And (4) loss.

Generally, a nozzle steam distribution mode is adopted in a regulation stage of a large-scale steam turbine, and the flow area of the regulation stage is adjusted by controlling the opening and closing of a regulation valve of a nozzle group, so that the main steam pressure and the flow rate are cooperatively controlled. The nozzle group in the adjusting stage is a tapered nozzle which can accelerate the steam to the local sonic speed under the critical pressure ratio. Under medium and low load, the back pressure of the regulating stage is small, and the great increase of the main steam pressure directly causes the regulating stage pressure ratio to be smaller than the critical pressure ratio, thereby causing huge

And (4) loss. How to ensure the operating efficiency of the coal-fired thermal power generating unit under the low-load working condition in the deep peak shaving process becomes an urgent need of energy transformation in China.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a turboset with a double-channel adjusting stage, a calculation method and an operation method, and mainly aims to solve the problems of low operation efficiency, poor adjusting capability and the like of a coal-fired thermal power generating unit under medium and low loads in the process of participating in deep peak regulation in the prior art.

In order to solve the problems, the technical scheme adopted by the invention is as follows:

in a first aspect, the invention provides a steam turbine set with a dual-channel adjusting stage, which comprises a main steam valve and a high-pressure cylinder, wherein the main steam valve is connected with the high-pressure cylinder, the adjusting stage is arranged in the high-pressure cylinder, the adjusting stage is provided with a first nozzle channel and a second nozzle channel, the first nozzle channel and the second nozzle channel are arranged from inside to outside along the radial direction, the first nozzle channel and the second nozzle channel are respectively provided with a gradually-reduced nozzle group and/or a gradually-reduced nozzle group, and an adjusting valve is arranged between the main steam valve and each of the gradually-reduced nozzle group and the gradually-reduced nozzle group.

Further, the adjusting stage is provided with a pressure stage group, the pressure stage group comprises a first stationary blade cascade, a second stationary blade cascade and a movable blade cascade, the first stationary blade cascade is arranged at the outlet of the first nozzle channel, the second stationary blade cascade is arranged at the outlet of the second nozzle channel, the first stationary blade cascade corresponds to the inner ring part of the movable blade cascade, the second stationary blade cascade corresponds to the outer ring part of the movable blade cascade, and the first stationary blade cascade and the second stationary blade cascade share the movable blade cascade.

Furthermore, the adjusting stage is provided with a first pressure stage group and a second pressure stage group, the first pressure stage group and the second pressure stage group are connected in series, the first nozzle channel is connected with the first pressure stage group, and the second nozzle channel is connected with the second pressure stage group.

Furthermore, the second nozzle passage is composed of a plurality of tapered nozzle groups, the first nozzle passage is composed of a plurality of tapered nozzle groups, a speed recovery stage is arranged behind the tapered nozzle groups, and the speed recovery stage comprises at least two rows of movable blades.

Further, the first nozzle passage is composed of 0 or even number of convergent-divergent nozzle groups and 0 or even number of convergent-divergent nozzle groups; the second nozzle channel is composed of 0 or even number of convergent-divergent nozzle groups and 0 or even number of convergent-divergent nozzle groups.

Furthermore, in the first nozzle channel and/or the second nozzle channel, the tapered nozzle groups are divided into at least one pair of arrangement pairs according to the two tapered nozzle groups, and the two tapered nozzle groups in the same arrangement pair are arranged axially symmetrically along a certain diameter of the circular section of the adjusting stage or arranged centrally symmetrically with the center of the circular section;

the two zooming type nozzle groups are divided into at least one pair of arrangement pairs according to the two zooming type nozzle groups, and the two zooming type nozzle groups in the same arrangement pair are axially and symmetrically arranged along a certain diameter of the circular section of the adjusting stage or are arranged in a central symmetry manner by using the circle center of the circular section.

Further, the tapered nozzle groups and the convergent-divergent nozzle groups are arranged along the circumferential direction of the adjusting stage and are sequentially and alternately arranged in the circumferential direction of the adjusting stage.

Further, the number of the tapered nozzle groups in the first nozzle passage is m₁Each tapered nozzle group has an outlet cross-sectional area S, and S₁≤S₂≤S₃≤…≤S_m1；

The number of the convergent-divergent nozzle groups in the first nozzle passage is n₁-m₁N is₁-m₁Not less than 0, the design pressure ratio of each convergent-divergent nozzle group is pi, and pi_m1+1≤Π_m1+2≤Π_m1+3≤…≤Π_n1；

The cross section area of the outlet corresponding to two tapered nozzle groups in the same arrangement pair group is S_iAnd S_i+1Wherein i is [1, m ]₁]Odd number of (1);

the design pressure ratio corresponding to two convergent-divergent nozzle groups in the same arrangement pair group is pi_jAnd pi_j+1Wherein j is [ m ]₁+1,n₁]Is odd in number.

Further, the number of the tapered nozzle groups in the second nozzle passage is m₂Each of the tapered nozzle groups has an outlet cross-sectional area S' and S ″₁≤S`₂≤S`₃≤…≤S`_m2；

The number of the convergent-divergent nozzle groups in the second nozzle passage is n₂-m₂N is₂-m₂Not less than 0, the design pressure ratio of each convergent-divergent nozzle group is pi', and pi ″, and_m2+1≤Π`_m2+2≤Π`_m2+3≤…≤Π`_n2；

the cross-sectional area of the outlet corresponding to two tapered nozzle groups in the same arranged pair group is S ″_iAnd S_i+1Wherein i is [1, m ]₂]Odd number of (1);

the design pressure ratio corresponding to two convergent-divergent nozzle groups in the same arrangement pair group is pi ″_jII & ltII & gt_j+1Wherein j is [ m ]₂+1,n₂]Is odd in number.

In a second aspect, the present invention provides a calculation method for calculating a flow area of a nozzle block in a first nozzle passage and a second nozzle passage in a steam turbine block having a two-passage adjusting stage as described above, comprising the steps of:

determining an upper load boundary L for a scaled nozzle group workload interval_xThen the design work load interval of the tapered nozzle group is [ L ]_xAt full load]The design work load interval of the convergent-divergent nozzle group is [ L_x0,L_x]Wherein 0 is<L_x0≤30％；

Determining the total flow area A of the tapered nozzle according to the full-load working condition parameters of the unit_1～m1+m2；

Determining the number of the combination of the tapered nozzle groups, and determining the number of valve points operated by the tapered nozzle groups according to the number of the combination;

determining the load factor of each valve point according to the number of the valve points operated by the tapered nozzle groups, and further determining the flow area A corresponding to the combination of each tapered nozzle group₁～A_m1+m2；

Determining the number of the combination of the scaling type nozzle groups, and determining the number of valve points operated by the scaling type nozzle groups according to the number of the combination;

according to a convergent-divergent nozzle groupThe number of the operating valve points, the load factor of each valve point and the outlet area A' corresponding to each zoom type nozzle group are determined₁～A`_{(n1-m1)+(n2-m2)}；

Determining partial steam admission degrees e of the first nozzle group and the second nozzle group according to the flow areas of the nozzle groups contained in the first nozzle channel and the second nozzle channel₁、e₂And leaf height l₁、l₂。

Further, in determining the lower load boundary L of the convergent nozzle group workload interval, the method comprises the following steps: let P_0,maxThe main steam pressure is the maximum main steam pressure allowed by the steam turbine set, r is a pressure loss coefficient caused by steam flowing through a main steam valve, and the value is 0-10%; critical pressure ratio of nozzle group according to formula

Calculating, wherein k is the isentropic index of the superheated steam and takes the value of 1.2 to 1.5; resetting the inlet pressure P of the regulating stage₁＝P_0,maxX (1-r), according to the critical pressure ratio of nozzle group, pi_crDetermining the load L such that the load has a lower regulating-stage back pressure P_bSatisfy P_b/P₁＝Π_cr；

Upper load boundary L in determining scaled nozzle group workload interval_xThe method comprises the following steps: determining minimum convergent nozzle group combination A₁Corresponding load L₁And delta L is the sliding pressure operation interval of the tapered nozzle group, the range is 5-20 percent, and then L is_x＝L₁-ΔL；

Determining the total flow area A of the tapered nozzle_1～m1+m2The method comprises the following steps: obtaining main steam flow D and adjusting stage back pressure P under full load working condition_bAnd setting the main steam pressure to the design pressure P_0,maxThe main valve pressure loss is r. Obtaining the total flow area A of the tapered nozzle according to the flow rate pressure ratio relation formula of the tapered nozzle_1～m1+m2：

Wherein D is the main steam mass flow at full load, unit kg/s; a. the_1～m1+m2Is the total flow area of all the tapered nozzle groups, unit m²；ρ₀Is the inlet steam density in kg/m³；

Determining the flow area A corresponding to each tapered nozzle group₁～A_m1+m2The method comprises the following steps: according to m₁+m₂Setting the work load interval [ L ] of the tapered nozzle group according to the selective result of the area combination_xAt full load]Obtaining the regulating stage back pressure P under the working condition of the valve point_bMain steam flow D and main steam pressure is set to design pressure P_0,maxThe main valve pressure loss is r. Obtaining the flow area A of each tapered nozzle group according to the relationship of the flow rate and the pressure ratio of the tapered nozzles₁～A_m1+m2；

Determining the flow area A' corresponding to each zoom type nozzle group₁～A`_{(n1-m1)+(n2-m2)}The method comprises the following steps: combining and designing the scaling type nozzle groups with the same pressure ratio, and setting the working load interval [0, L ] of the scaling type nozzle groups according to the combination of the scaling type nozzle groups_x]Inner valve point to obtain regulating stage back pressure P under valve point working condition_bMain steam flow D_xAnd setting the main steam pressure to the design pressure P_0,maxThe main valve pressure loss is r. Obtaining the total flow area A of the combination of the convergent-divergent nozzle groups according to a convergent-divergent nozzle flow pressure ratio relation:

wherein D is_xThe unit is kg/s of main steam mass flow during the load; a is the total flow area of the convergent-divergent nozzle group combination, i.e. the total throat area, in m²；Π_crIs the critical pressure ratio.

Determining partial steam admission e of the first and second nozzle groups₁、e₂And leaf height l of leaf height₁、l₂The method comprises the following steps:

the outer diameter of the baffle of the stationary blade grid of the adjusting stage is D₀The first and second diameters of the annular channel of the first nozzle are respectively D₀、D₁Wherein D is₀<D₁(ii) a The first and second diameters of the annular channel of the second nozzle are D₂,D₃In which D is₁<D₂，D₂<D₃At this time, the following relation should be satisfied:

select 0.1<e₁<0.9，0.1<e₂<0.9, and thereby obtaining a first nozzle group blade height of l₁＝0.5×(D₁-D₀) The second nozzle group has a blade height of l₂＝0.5×(D₂-D₁)。

In a third aspect, the invention provides a method for operating a steam turbine having a two-channel regulating stage, comprising the steps of:

when the steam turbine set runs at full load, opening the regulating valves of all the tapered nozzle groups in the first nozzle channel and the second nozzle channel, and closing the regulating valves of all the tapered nozzle groups in the first nozzle channel and the second nozzle channel;

in [ L ]_xAt full load]In the load interval, dividing a plurality of tapered nozzle operation load intervals according to the number of valve points operated by the tapered nozzle group, binding each tapered nozzle operation load interval to one combination of selective results of the tapered nozzle group according to area combination, and in each tapered nozzle operation load interval, operating the steam turbine unit according to a sliding pressure operation mode until the load is reduced to the next valve point position;

when the load of the steam turbine unit falls into a certain operating load interval of the tapered nozzles, opening the regulating valve corresponding to the tapered nozzle group combination, and closing the rest nozzle groups;

in [ L ]_x0,L_x]In the load interval, according to the number of the valve points operated by the zooming type nozzle group,dividing a plurality of operation load intervals of the scaling-type nozzle groups, binding each operation load interval of the scaling-type nozzle groups to one of the set arrangement combinations of the scaling-type nozzle groups, and operating the steam turbine set in a sliding pressure operation mode in each operation load interval of the scaling-type nozzle groups until the load is reduced to the position of the next valve point;

and when the load of the steam turbine set falls in a certain operation load interval of the scaling type nozzle set, opening the regulating valve corresponding to the scaling type nozzle set combination, and closing the rest nozzle sets.

Further, the selective result of the combination of the tapered nozzle groups or the scaled nozzle groups according to the area includes the valves of which the valves are not completely closed or the valves of which the valves are not completely opened, namely, a certain overlap degree is kept between the ascending valve sequence and the descending valve sequence.

Compared with the prior art, the invention at least comprises the following beneficial effects:

two channels which are arranged from inside to outside along the radial direction are arranged in the adjusting stage of the high-pressure cylinder, the two channels are respectively provided with a tapered nozzle group and/or a tapered nozzle group, the two channels are adopted for supplying air to the adjusting stage, the defects of poor effect, uneven air supply and poor adjustability in single channel air supply are overcome, the tapered nozzle group exists in the two channels, and the machine set runs in an L mode when the machine set runs in the L mode_xAt full load]Under the high load working condition, the tapered nozzle group is opened, and the machine group runs at [ L ]_x0,L_x]When the working condition is medium or low load, the convergent-divergent nozzle group is opened, steam expands in the convergent-divergent nozzle group and accelerates to supersonic speed, the operating pressure is greatly increased to the maximum allowable pressure, the operating efficiency is improved, and the pressure loss is reduced;

by utilizing the characteristic that the flow area of the inner ring nozzle channel is smaller than that of the outer ring nozzle channel, the tapered nozzle group is arranged in the outer ring nozzle channel, and the scaled nozzle group is arranged in the inner ring nozzle channel, so that when the nozzle groups are switched under the working conditions of high load and low load, the partial steam admission degree of the scaled nozzle group in the inner ring nozzle channel can be greatly reduced, and the regulation stage efficiency is improved;

in the two nozzle channels, the tapered nozzle groups can be divided into at least one pair of arrangement pairs in pairs, the flow areas of the tapered nozzle groups in the same pair of arrangement pairs are close or equal, the pair of tapered nozzle group arrangement pairs are symmetrically arranged along the axis of the adjusting stage or are symmetrically arranged at the center, and similarly, the pair of tapered nozzle group arrangement pairs with similar or equal pressure ratios are symmetrically arranged along the axis of the adjusting stage or are symmetrically arranged at the center, and the tapered nozzle groups are sequentially and alternately arranged in the circumferential direction of the adjusting stage, so that the mutual acting force generated when the nozzle groups flow steam can be effectively balanced, and the running stability of the steam turbine set is improved;

determining the upper load rate boundary L of the working load interval of the scaling type nozzle group_xTo respectively define the design workload interval [ L ] of the tapered nozzle set_xAt full load]And a design workload interval [ L ] of said convergent-divergent nozzle group_x0,L_x]Then calculating to obtain the total flow area A of the tapered nozzle_1～m1+m2And obtaining the flow area A corresponding to each tapered nozzle group according to the number of the tapered nozzle group combinations₁～A_m1+m2Finally, the flow area A' corresponding to each scaling type nozzle group is calculated according to the combined number of the scaling type nozzle groups₁～A`_{(n1-m1)+(n2-m2)}Determining the flow area of each nozzle;

the operation load intervals correspond to the combinations of the nozzle groups one by one, and when the steam turbine set operates to a specific tapered nozzle operation load interval, the regulating valve corresponding to the combination of the tapered nozzle groups is opened; when the load of the steam turbine unit falls in a specific operation load interval of the scaling type nozzle group, the regulating valve corresponding to the scaling type nozzle group combination is opened, the steam turbine unit operates in a sliding pressure mode in the operation load interval, and the steam turbine unit is guaranteed to operate under the condition that the flow area of the nozzle is adjusted to be proper under different load working conditions, so that the operation pressure of the steam turbine unit is improved, the pressure loss is reduced, and the operation efficiency is improved.

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

Drawings

The invention is further illustrated by means of the attached drawings, but the embodiments in the drawings do not constitute any limitation to the invention, and for a person skilled in the art, other drawings can be obtained on the basis of the following drawings without inventive effort.

Fig. 1 is a schematic illustration of a steam turbine assembly according to the invention with a two-channel regulating stage.

Fig. 2 is a schematic cross-sectional view of a conditioning stage in a steam turbine having a dual path conditioning stage according to the present invention.

Fig. 3 is a schematic representation of the change in section of the regulating stage in the direction of the axis of rotation.

FIG. 4 is a schematic diagram of a pressure stage stack according to one embodiment.

FIG. 5 is a schematic diagram of the configuration of a lower pressure stage set according to another embodiment.

FIG. 6 is a schematic view of a nozzle group of nozzle channels in one embodiment.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, when a specific device is described as being located between a first device and a second device, intervening devices may or may not be present between the specific device and the first device or the second device. When a particular device is described as being coupled to other devices, that particular device may be directly coupled to the other devices without intervening devices or may be directly coupled to the other devices with intervening devices.

Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate.

In a first aspect, referring to fig. 1 to 6, in this embodiment, a steam turbine set with a dual-channel adjusting stage 2 is disclosed, which includes a main steam valve 13 and a high pressure cylinder 6, where the main steam valve 13 is connected to the high pressure cylinder 6, and certainly, as a mechanism matched with a steam turbine, the steam turbine set also includes a steam turbine rotating shaft 1, an intermediate pressure cylinder 7, a low pressure cylinder 8, and a generator 9, the high pressure cylinder 6, the intermediate pressure cylinder 7, the low pressure cylinder 8, and the generator 9 are sequentially installed and arranged along a central axis direction of the steam turbine rotating shaft 1, and an exhaust outlet of the low pressure cylinder 8 is connected to a condenser 10; a condensed water outlet of the condenser 10 is connected with a water feeding inlet of the boiler 12 through a water feeding pipeline, and a condensed water pump 15, a low-pressure heater 16, a deaerator 17, a water feeding pump 11 and a high-pressure heater 18 are sequentially connected on the water feeding pipeline along the water flow direction; the outlet of the boiler 12 is connected with the steam inlet of the high-pressure cylinder 6 through a main steam pipeline, a main steam valve 13 is arranged in the main steam pipeline, and the air outlet of the high-pressure cylinder 6 is connected with the air inlet of the intermediate pressure cylinder 7 through an intermediate regulating door 14 after passing through the boiler 12.

The high-pressure cylinder 6 is internally provided with an adjusting stage 2, the adjusting stage 2 is positioned before a conventional pressure stage of the high-pressure cylinder 6, the adjusting stage 2 is provided with a first nozzle channel 4 and a second nozzle channel 5, the first nozzle channel 4 and the second nozzle channel 5 are arranged from inside to outside along the radial direction, the first nozzle channel 4 and the second nozzle channel 5 can be divided into an inner ring and an outer ring in the channel part, the outer ring surrounds the inner ring in position, but the outlet parts of the first nozzle channel 4 and the second nozzle channel 5 can be arranged from inside to outside or can be arranged in the same diameter;

the first nozzle channel 4 and the second nozzle channel 5 are respectively provided with a tapered and/or convergent-divergent nozzle group, a main steam valve 13 and each tapered nozzle groupThe adjusting valves are arranged between the nozzle groups and the convergent-divergent nozzle groups, and are used for controlling the on-off of each of the convergent-divergent nozzle groups and the convergent-divergent nozzle groups, it should be noted that the arrangement of the nozzle groups of the first nozzle channel 4 and the second nozzle channel 5 can be the same or different, and the nozzle groups of the two channels are independently arranged and independently controlled. At least one of the first nozzle channel 4 and the second nozzle channel 5 is provided with a convergent-divergent nozzle group, because the convergent-divergent nozzle group can only accelerate the steam to the local sound velocity under the critical pressure ratio, when the load working condition is reduced, the back pressure of the adjusting stage 2 is smaller, and the great increase of the main steam pressure directly causes the pressure ratio of the adjusting stage 2 to be smaller than the critical pressure ratio, so that huge pressure difference is caused

Loss; thus, a convergent-divergent nozzle group is provided in the first nozzle channel 4 and/or the second nozzle channel 5, when the group is operating at [ Lx, full load ]]Under high load condition, the tapered nozzle set is opened, and when the set is operated at [ Lx0, Lx]And when the medium-low load working condition is met, the scaling type nozzle group is opened, steam expands in the scaling type nozzle group and accelerates to supersonic speed, the operating pressure is greatly increased to the maximum allowable pressure, the operating efficiency is improved, the pressure loss is reduced, and the high-efficiency operation under the high-medium low full-load working condition is realized.

Additionally, with reference to fig. 2, since the adjusting stage 2 adopts a partial steam admission mode, if a single-channel steam admission easily causes problems of uneven air supply, poor effect, and the like, in this embodiment, a steam admission channel is added in an internal and external double-channel mode, even if each channel still has partial steam admission, the target of uniform steam admission under different load conditions can be still achieved by adjusting the position of the nozzle group in each nozzle channel, so that the air supply effect is improved, and the effect is better when different nozzle groups are adjusted and switched. Referring to fig. 3, the first nozzle passage 4 and the second nozzle passage 5 undergo a change in radial contraction in the axial direction as shown by the adjustment stage stationary blade cascade meridian plane 3.

Furthermore, by utilizing the characteristic that the flow area of the inner ring nozzle channel is smaller than that of the outer ring nozzle channel, the tapered nozzle group is arranged in the outer ring nozzle channel, and the tapered nozzle group is arranged in the inner ring nozzle channel, so that when the nozzle groups are switched under the high-low load working condition, the partial steam admission degree of the tapered nozzle group in the inner ring nozzle channel can be greatly reduced, and the efficiency of the adjusting stage 2 is improved.

For the connection of the first nozzle channel 4 and the second nozzle channel 5 to the pressure stage group in the regulating stage 2, there are at least two ways:

referring to fig. 4, as an embodiment, the pressure stage group includes a first stationary blade cascade 41, a second stationary blade cascade 51 and a movable blade cascade 31, the outlet of the first nozzle channel 4 is provided with the first stationary blade cascade 41, the outlet of the second nozzle channel 5 is provided with the second stationary blade cascade 51, the first nozzle channel 4 is arranged at the inner ring, the second nozzle channel 5 is arranged at the outer ring, the first nozzle channel 4 and the second nozzle channel 5 are arranged from inside to outside along the radial direction, the first stationary blade cascade 41 and the second stationary blade cascade 51 are also arranged sequentially along the radial direction, that is, the projection of the first stationary blade cascade 41 and the second stationary blade cascade 51 along the radial direction are overlapped, wherein the first stationary blade cascade 41 corresponds to the inner ring part 32 of the movable blade cascade 31, the second stationary blade cascade 51 corresponds to the outer ring part 33 of the movable blade cascade 31, the first stationary blade cascade 41 and the second stationary blade cascade 51 share the movable blade cascade 31, which corresponds to one movable blade cascade 31 to two stationary blade cascades, whether the first nozzle channel 4 of the inner ring or the second nozzle channel 5 of the outer ring, after the steam passes through the corresponding static blade cascades, the steam can act on one movable blade cascade 31 in the same way, only the acting parts are different, and the two static blade cascades and the channels thereof are connected in parallel before the movable blade cascade 31; additionally, a gland seal assembly 34 may be provided at the interface of the inner and outer ring portions of the rotor blade cascade 31 to maintain a seal with the turbine stator.

Referring to fig. 5, as another embodiment, the regulation stage 2 is provided with a first pressure stage group 42 and a second pressure stage group 52, the first pressure stage group 42 and the second pressure stage group 52 are connected in series, both arranged before the conventional pressure stage group of the high pressure cylinder 6, the first nozzle channel 4 is connected with the first pressure stage group 42, the second nozzle channel 5 is connected with the second pressure stage group 52, the first pressure stage group 42 is in front, and the second pressure stage group 52 is in back; when the high-load working condition is operated, the second nozzle channel 5 of the outer ring is opened, and only the second pressure stage group 52 is put into operation; when the nozzle is operated under the medium and low load working condition, the first nozzle channel 4 of the inner ring is opened, at the moment, due to the serial connection relation of the first pressure stage group 42 and the second pressure stage group 52, the first pressure stage group 42 and the second pressure stage group 52 are both put into operation, the requirement for multiple pressure stages under the medium and low load is met, meanwhile, the flow area of the inner ring is reduced, the partial steam admission degree of the scaling type nozzle group in the nozzle channel of the inner ring is greatly reduced, and the efficiency of the adjusting stage 2 is improved. Additionally, a non-return valve 53 is provided between the first pressure stage group 42 and the second pressure stage group 52, the non-return valve 53 opening when only the first nozzle passage 4 is admitting air, while blocking the outlet of the second nozzle passage 5; when only the second nozzle channel 5 is admitted, the non-return valve 53 closes, preventing the first pressure stage group 42 from idling.

As for the constitution of each nozzle group in the first nozzle passage 4 and the second nozzle passage 5, there are at least the following cases:

in a possible embodiment, the first nozzle channel 4 is formed by a number of sets of tapered nozzles and a number of sets of convergent-divergent nozzles, and the second nozzle channel 5 is also formed by a number of sets of tapered nozzles and a number of sets of convergent-divergent nozzles.

In another possible embodiment, the first nozzle channel 4 is constituted by a number of sets of tapered nozzles; the second nozzle channel 5 is formed by several convergent-divergent nozzle groups.

In another possible embodiment, the second nozzle passage 5 is formed by a plurality of tapered nozzle groups, the first nozzle passage 4 is formed by a plurality of tapered nozzle groups, and a speed recovery stage is provided after the tapered nozzle groups, the speed recovery stage including at least two rows of movable blades, and the speed recovery stage is provided to improve the operating efficiency and reduce the pressure loss by the speed recovery stage having a plurality of rows of movable blades when the first nozzle passage 4 in the inner ring needs to be switched to at a medium/low load, that is, after the steam is accelerated by the tapered nozzle groups.

In some embodiments, the first nozzle passage 4 is composed of 0 or even number of sets of convergent nozzles and 0 or even number of sets of convergent nozzles; the second nozzle channel 5 is composed of 0 or an even number of sets of tapered nozzles and 0 or an even number of sets of tapered nozzles, i.e., no single set of nozzles exists, no set of nozzles of the same type exists, but an even number of sets of nozzles is present, regardless of whether the first nozzle channel 4 or the second nozzle channel 5 is present.

Further, in the first nozzle passage 4 and/or the second nozzle passage 5, respectively, the following features are provided: the quantity of the tapered nozzle groups is even, the tapered nozzle groups are divided into at least one pair of arrangement pairs according to the fact that the two tapered nozzle groups are a pair, and the two tapered nozzle groups in the same arrangement pair adopt axial symmetry arrangement or central symmetry arrangement according to the circle center of the circular section along a certain diameter of the circular section of the adjusting stage 2;

the number of the zooming type nozzle groups is even, the zooming type nozzle groups are divided into at least one pair of arrangement pairs according to that the two zooming type nozzle groups are a pair, and the two zooming type nozzle groups in the same arrangement pair are arranged in an axial symmetry mode along a certain diameter of the circular section of the adjusting stage 2 or in a central symmetry mode through the circle center of the circular section.

Equivalently, a plurality of tapered nozzle groups are grouped in pairs, so that the operation stability of the steam turbine set is reduced in order to avoid the mutual acting force generated when one nozzle group is used for flowing steam, one nozzle group is also arranged on one side of the axial symmetry or the central symmetry of the nozzle group, and the acting forces generated by the two opposite nozzle groups can be greatly offset so as to reduce the stability influence on the steam turbine set.

Referring to fig. 6, next, each nozzle group of one of the nozzle channels is taken as an example for explanation, wherein

reference numerals

21, 22, 23, and 24 are all tapered nozzle groups, and reference numerals of corresponding regulating valves are 210, 220, 230, and 240, respectively;

reference numerals

25, 26, 27 and 28 are all scaling type nozzle groups, and the reference numerals of the corresponding regulating valves are 250, 260, 270 and 280 respectively; that is, in some embodiments, the tapered nozzle groups and the convergent-divergent nozzle groups are alternately arranged in sequence in the circumferential direction of the adjusting stage 2, that is, one convergent-divergent nozzle group is disposed between two tapered nozzle groups, and one tapered nozzle group is disposed between two convergent-divergent nozzle groups, and the tapered nozzle groups are alternately arranged with each other.

More specifically, the number of tapered nozzle groups in the first nozzle passage 4 is m₁Each tapered nozzle group has an outlet cross-sectional area S, and S₁≤S₂≤S₃≤…≤S_m1The cross section area of the outlet is equivalent to the flow area of the tapered nozzle group;

the number of convergent-divergent nozzle groups in the first nozzle passage 4 is n₁-m₁N is₁-m₁Not less than 0, the design pressure ratio of each convergent-divergent nozzle group is pi_m1+1≤Π_m1+2≤Π_m1+3≤…≤Π_n1；

The cross-sectional area of the outlet corresponding to two tapered nozzle groups in the same arrangement pair group is S_iAnd S_i+1Wherein i is [1, m ]₁]An odd number of (1);

In addition, m is₁The sectional areas of the outlets of the tapered nozzle groups are not necessarily all equal, the sectional areas of the outlets are arranged from small to large, and the tapered nozzle groups are arranged in pairs in sequence to form two tapered nozzle groups in a pair, namely the area S₁、S₂Corresponding tapered nozzle groups as an arrangement pair group, area S₃、S₄Corresponding tapered nozzle groups as an arrangement pair group, area S_m-1、S_mThe corresponding tapered nozzle groups are used as an arrangement pair group, so that when the tapered nozzle groups are arranged along the axial symmetry or the central symmetry of the adjusting stage 2, the acting forces generated by the two nozzle groups of the same arrangement pair group are closer, namely small and small opposite impacts and large opposite impacts, so that the stability of the unit is better in the adjusting process. Similarly, the outlet cross-sectional area is used as a grouping basis in the tapered nozzle groups, the design pressure ratio is used as a grouping basis in the tapered nozzle groups, and two tapered nozzle groups with the same or similar design pressure ratios are used as the grouping basisA pair of arrangement pairs.

In addition, when the tapered nozzle groups and the tapered nozzle groups are arranged alternately in the circumferential direction, the relationship between the outlet cross-sectional area and the design pressure ratio is also referred to, for example, S, which is the smallest outlet cross-sectional area first in the clockwise direction₁The corresponding tapered nozzle group is II with the minimum design pressure ratio_m+1Corresponding convergent-divergent nozzle group, and outlet cross-sectional area S₂The corresponding tapered nozzle group is designed with a pressure ratio pi_m+2Corresponding convergent-divergent nozzle group, and finally S with maximum outlet cross-sectional area_mCorresponding tapered nozzle group, and pi at maximum design pressure ratio_nThe corresponding convergent-divergent nozzle groups are sequentially alternated according to the size order.

Additionally, the number of tapered nozzle groups in the second nozzle passage 5 is m₂Each of the tapered nozzle groups has an outlet cross-sectional area S' and S ″₁≤S`₂≤S`₃≤…≤S`_m2；

The number of convergent-divergent nozzle groups in the second nozzle passage 5 is n₂-m₂N is₂-m₂Not less than 0, the design pressure ratio of each convergent-divergent nozzle group is pi', and pi ″, wherein_m2+1≤Π`_m2+2≤Π`_m2+3≤…≤Π`_n2；

The two tapered nozzle groups in the same arrangement pair group correspond to the outlet cross section area of S ″_iAnd S_i+1Wherein i is [1, m ]₂]Odd number of (1);

The second nozzle channel 5 has the same principle as the first nozzle channel 4 and will not be described herein again, referring to the above description.

In a second aspect, the present embodiment provides a calculation method, applied to the calculation of the flow area of the nozzle block in the first nozzle passage 4 and the second nozzle passage 5 in the steam turbine set with the two-passage adjusting stage 2 as in the above embodiment, including the following steps:

determining an upper load boundary L for a scaled nozzle group workload interval_xThe design workload interval of the tapered nozzle set is [ L ]_xAt full load]The design workload interval of the convergent-divergent nozzle group is [ L ]_x0,L_x]Wherein 0 is<L_x0Less than or equal to 30 percent; by determining L_xThe high-load working condition and the medium-low load working condition are separated, the tapered nozzle group is only allowed to be opened in the high-load working condition, and the tapered nozzle group is only allowed to be opened in the medium-low load working condition;

Determining the number of the combination of the tapered nozzle groups, determining the number of the required area combinations which can be combined according to the set number of the tapered nozzle groups, and determining the number of the valve points of the tapered nozzle groups according to the number of the combinations;

Determining the number of the combination of the scaling type nozzle groups, determining the number of the area combination required by combination according to the set number of the scaling type nozzle groups, and determining the number of valve points operated by the scaling type nozzle groups according to the number of the combination;

determining the load factor of each valve point according to the number of the valve points operated by the convergent-divergent nozzle group, and further determining the outlet area A' corresponding to each convergent-divergent nozzle group₁～A`_{(n1-m1)+(n2-m2)}；

Determining partial steam admission degrees e of the first nozzle group and the second nozzle group according to the flow areas of the nozzle groups contained in the first nozzle channel 4 and the second nozzle channel 5₁、e₂And leaf height l₁、l₂。

More specifically, first, the upper load rate boundary L in the determination of the scaled nozzle group workload interval_xThe method comprises the following steps: assuming an upper load rate bound L for a scaled nozzle group workload interval_xArrangement of nozzle groups of the type which is taperedThe working load interval is measured as [ L_xAt full load]The design workload interval of the convergent-divergent nozzle group is [ L ]_x0,L_x]Wherein 0 is<L_x0Less than or equal to 30 percent, and P is set_0,maxThe steam turbine set is allowed to have the maximum main steam pressure, r is a pressure loss coefficient caused by steam flowing through a main steam valve, and the value of r is 0-10%; critical pressure ratio of nozzle group according to formula

Calculating, wherein k is the isentropic index of the superheated steam and takes the value of 1.2 to 1.5; resetting the inlet pressure P of the regulating stage 2₁＝P_0,maxX (1-r) according to critical pressure ratio pi of nozzle group_crDetermining the load L such that the load is reduced by a back pressure P of the regulating stage 2_bSatisfy P_b/P₁＝Π_cr；

Secondly, the total flow area A of the tapered nozzle is determined_1～m1+m2The method comprises the following steps: obtaining main steam flow D and adjusting stage 2 backpressure P under full load working condition_bAnd setting the main steam pressure to the design pressure P_0,maxThe main valve pressure loss is r. Obtaining the total flow area A of the tapered nozzle according to the flow pressure ratio relation of the tapered nozzle_1～m1+m2：

Wherein D is the main steam mass flow at full load, unit kg/s; a. the_1～m1+m2Is the total flow area of all the tapered nozzle groups, in m²；ρ₀Is the inlet steam density in kg/m³；

Then, the flow area A corresponding to each tapered nozzle group is determined₁～A_m1+m2The method comprises the following steps: according to m₁+m₂Setting the working load interval [ L ] of the tapered nozzle group according to the selective result of the area combination_xAt full load]Obtaining the back pressure P of the regulating stage 2 under the working condition of the valve point_bMain steam flow D and main steam pressure is set to design pressure P_0,maxThe main valve pressure loss is r. Obtaining the flow area A of each tapered nozzle group according to the relationship of the flow rate and the pressure ratio of the tapered nozzles₁～A_m1+m2(ii) a It should be noted that, because each tapered nozzle group has a corresponding outlet cross-sectional area, the tapered nozzle groups are sorted from large to small according to the combination of areas, and a required combination result is selected from the sorted combination results, for example, there are four tapered nozzle groups, and the following combination results are selected: s₁+S₂，S₁+S₃，S₂₊S₃，S₁+S₂+S₃，S₂+S₃+S₄，S₁+S₂+S₃+S₄Respectively, ordered from small to large, there are 6 combined results, which will also be [ L_xAt full load]Dividing the flow area into six valve points, and further obtaining the flow area A of each tapered nozzle group₁～A_m1+m2；

Determining the flow area A' corresponding to each convergent-divergent nozzle group₁～A`_{(n1-m1)+(n2-m2)}The method comprises the following steps: combining and designing the scaling type nozzle groups with the same pressure ratio, and setting the working load interval [0, L ] of the scaling type nozzle groups according to the combination of the scaling type nozzle groups_x]Internal valve points, for example, there are four convergent-divergent nozzle groups whose design pressure ratios have the following relationship pi₅＝Π₆<Π₇＝Π₈When grouping, will Π₅+Π₆Is divided into a group pi₇+Π₈Are divided into a group corresponding to [ L ]_x0,L_x]Two valve points are arranged in the interval; obtaining the back pressure P of the regulating stage 2 under the working condition of a valve point_bMain steam flow rate D_xAnd setting the main steam pressure to the design pressure P_0,maxThe main valve pressure loss is r. Obtaining the total flow area A of the combination of the convergent-divergent nozzle group according to the flow rate-pressure ratio relation of the convergent-divergent nozzle：

the outer diameter of the fixed blade grid clapboard of the adjusting stage 2 is D₀The first and second diameters of the annular channel of the first nozzle are respectively D₀、D₁In which D is₀<D₁(ii) a The first and second diameters of the annular channel of the second nozzle are D₂,D₃Wherein D is₁<D₂，D₂<D₃At this time, the following relation should be satisfied:

In a third aspect, the present embodiment provides an operation method of a steam turbine set with a two-channel adjusting stage 2, it should be noted that, the operation method is applied to the steam turbine set in each of the above embodiments, that is, the first nozzle channel 4, the second nozzle channel 5, and the tapered nozzle group in various arrangement situations, and for convenience of description, the steam turbine set in a specific embodiment will be described below, in this embodiment, the first nozzle channel 4 of the steam turbine set is in an inner ring and is formed by the tapered nozzle group, and the second nozzle channel 5 is in an outer ring and is formed by the tapered nozzle group; the operation method specifically comprises the following steps:

when the steam turbine set runs at full load, the regulating valves of all the tapered nozzle groups in the second nozzle passage 5 are opened, the regulating valves of all the tapered nozzle groups in the first nozzle passage 4 are closed, steam with full load flow of the steam turbine set flows through, and the steam pressure in front of the main steam valve 13 is just the highest running pressure P designed by the steam turbine set_0,max. At this time, after the feed water is heated by the boiler 12 into high-temperature high-pressure superheated steam, the high-temperature high-pressure superheated steam is respectively sent to each tapered nozzle through the main steam valve and the adjusting valve corresponding to the tapered nozzle and is expanded and accelerated, the accelerated steam continues to expand and work in the steam turbine set, and the steam turbine rotating shaft 1 is driven to convert mechanical energy into electric energy. Under the full-load working condition, the steam turbine set of the embodiment only needs to open the tapered nozzle set in the second nozzle channel 5, the operating pressure of the turbine set is the same as that of a conventional turbine set, and the turbine set has equivalent power generation efficiency.

In [ L ]_xAt full load]In each tapered nozzle operation load interval, along with the reduction of the load, the steam flow is reduced, the back pressure of the regulating stage 2 is reduced, and the steam turbine unit operates in a sliding pressure operation mode until the load is reduced to the position of the next valve point; at this time, the superheated steam is sent into the gradual shrinkage type nozzle group in the through-flow state through the main throttle valve and the regulating valve corresponding to the gradual shrinkage type nozzle group in the through-flow state respectively to expand and accelerate, the accelerated steam continues to expand and work in the steam turbine set, and the steam turbine rotating shaft 1 is driven to convert the mechanical energy into the electric energy. At this time, compared with the conventional unit, the steam turbine unit of the present embodiment has a significantly reduced throttling loss due to the regulation stage 2 and generally has a higher main steam pressure, and therefore, the cycle efficiency and the overall power generation efficiency of the steam turbine unit are improved.

When the sliding pressure is operated to the valve point in the operating load interval of the tapered nozzle, the load of the steam turbine unit falls into a certain tapered type along with the gradual reduction of the loadWhen the nozzle operates in the load interval, at the position of each corresponding valve point, the regulating valve of the tapered nozzle group combination corresponding to the flow area of the valve point is opened, the other nozzle groups are closed, the working steam of the valve point is flowed, and the steam pressure in front of the main steam valve 13 is just the highest operating pressure P designed by the steam turbine set_0,max. At this time, the superheated steam is respectively sent into the valve point tapered nozzle group for expansion and acceleration through the main steam valve 13 and the tapered nozzle group regulating valve corresponding to the valve point position, the accelerated steam continues to expand and work in the steam turbine unit, and the steam turbine rotating shaft 1 is driven to convert the mechanical energy into electric energy. At this time, compared with the conventional unit, the operation pressure of the steam turbine unit in the present embodiment at the valve point is increased to the maximum pressure allowed, the cycle efficiency is significantly improved, and the pressure loss of the valve point operating condition adjusting stage 2 is extremely small, so that the present embodiment significantly improves the overall power generation efficiency of the steam turbine unit.

As the load continues to decrease, when decreasing to L_xThen, turn on L_xWhen the load valve point pressure ratio corresponds to the convergent-divergent nozzle group, other nozzle groups are closed, namely the regulating valves of all the convergent-divergent nozzle groups in the second nozzle passage 5 are closed, the corresponding convergent-divergent nozzle group in the first nozzle passage 4 is opened, the working steam of the valve point is flowed through, and the steam pressure before the main steam valve 13 is just the highest operating pressure P designed by the steam turbine unit_0,max. At this time, the superheated steam is respectively sent into the valve point convergent-divergent nozzle group through the main steam valve 13 and the convergent-divergent nozzle group regulating valve corresponding to the valve point pressure ratio to be expanded and accelerated to supersonic speed, the supersonic steam flow continues to expand and work in the steam turbine unit, and the steam turbine rotating shaft 1 is driven to convert the mechanical energy into electric energy. Because the conventional unit mostly adopts sliding pressure operation, at L_xCompared with the prior art, the steam turbine set of the embodiment has the advantages that the running pressure of the valve point is greatly increased to the maximum allowable pressure, the circulation efficiency is remarkably improved, and meanwhile, the pressure loss of the valve point working condition adjusting stage 2 is extremely small, so that the whole power generation efficiency of the steam turbine set is remarkably improved.

In [ L ]_x0,L_x]In the load interval, according to the number of the valve points operated by the zooming type nozzle group,dividing a plurality of operation load intervals of the scaling type nozzle groups, binding each operation load interval of the scaling type nozzle groups to one of the set arrangement combinations of the scaling type nozzle groups, in each operation load interval of the scaling type nozzle groups, reducing the steam flow along with the reduction of the load, reducing the back pressure of the adjusting stage 2, and operating the steam turbine set in a sliding pressure operation mode until the load is reduced to the next valve point position; compared with the prior art, the load interval between valve points of the steam turbine set is narrow, the main steam pressure under the working condition of the valve points is the maximum allowable main steam pressure, even if the load interval is also operated by adopting the sliding pressure, the main steam pressure is still far higher than that of the conventional set, and meanwhile, the pressure loss of the valve point working condition adjusting stage 2 is extremely small, so that the whole power generation efficiency of the steam turbine set is remarkably improved.

When the sliding pressure is operated to the valve point in the operation load interval of the convergent-divergent nozzle group, along with the gradual reduction of the load, the load of the steam turbine unit falls in the operation load interval of a certain convergent-divergent nozzle group, the regulating valve corresponding to the combination of the convergent-divergent nozzle groups is opened, the other nozzle groups are closed, the working steam of the valve point is flowed through, and the steam pressure before the main steam valve 13 is just the highest operation pressure P designed by the steam turbine unit_0,max. At the moment, the superheated steam is respectively sent into the valve point convergent-divergent nozzle groups through the main steam valve 13 and the convergent-divergent nozzle group regulating valves corresponding to the valve point pressure ratios to be expanded and accelerated to supersonic speed, the supersonic steam flow continues to expand and work in the steam turbine unit, and the steam turbine rotating shaft 1 is driven to convert mechanical energy into electric energy. Because the conventional unit mostly adopts sliding pressure operation in L_x0,L_x]The valve point position in the load interval is already slipped to a lower main steam pressure, and the pressure ratio is usually smaller than the critical pressure ratio, and the conventional tapered nozzle can only accelerate the steam to the critical state, thereby causing great pressure loss. Compared with the prior art, the steam turbine set in the embodiment has the advantages that the operating pressure of the valve point of the steam turbine set is greatly increased to the maximum allowable pressure, the cycle efficiency is remarkably improved, the pressure loss of the valve point working condition adjusting stage 2 is extremely small, steam can be accelerated to a supersonic speed state, and the pressure difference energy is fully utilized, so that the steam turbine set in the embodiment extremely has the advantages thatThe method obviously improves the overall power generation efficiency of the turboset.

In the above embodiment, in order to better utilize the characteristic that the flow area of the nozzle passage in the inner ring is smaller than that of the nozzle passage in the outer ring, the first nozzle passages 4 in the inner ring are all set as the convergent-divergent nozzle groups, and the second nozzle passages 5 in the outer ring are all set as the convergent-divergent nozzle groups, so that the characteristic that the flow area of the nozzle passages needs to be reduced under the medium-low load working condition is fully adapted, and therefore, the nozzle groups required by high load and low load are combined and separated, only the first nozzle passages 4 are used under the high load working condition, only the second nozzle passages 5 are used under the low load working condition, and the operation stability and reliability of the unit are improved.

As an embodiment, as an alternative result of the combination of the areas of the tapered nozzle groups or the scaled nozzle groups, the valves including valves that are not completely closed or valves that are not completely opened, i.e., a certain overlap between the ascending and descending valve sequences remains, and the valves may be in a state of not being completely opened or completely closed. When the steam turbine set is transited between two operation load intervals, the combination of the nozzle set corresponding to the previous operation load interval is not completely closed, and the combination of the nozzle set corresponding to the next operation load interval is opened, so that a certain overlapping degree is reserved, and smooth transition of the operation load intervals is facilitated. For example, when the valve point is switched in a transition mode, when the nozzle group combination corresponding to the previous operation load interval is closed until about 10% of the valve rod lift remains, the nozzle group combination corresponding to the next operation load interval is opened in advance, and after a load transition time is kept for a period of time, the regulating valve of the previous operation load interval is completely closed, a period of time is an overlapping state, in the embodiment, the overlapping degree is 1-10%, and in other embodiments, other values can be adopted.

In summary, compared with the prior art, the above embodiments provide a steam turbine set with a dual-channel adjusting stage 2, a calculation method and an operation method, wherein the adjusting stage 2 of the high-pressure cylinder 6 is provided with two channels arranged from inside to outside along the radial direction, the two channels are respectively provided with a tapered and/or a scaled nozzle set, and the dual-channel gas supply is adopted to the adjusting stage 2, so that the defects of poor effect, uneven gas supply and adjustability during single-channel gas supply are overcomeWeak defect, and the two channels have a convergent-divergent nozzle set, when the set is operated at [ L ]_xAt full load]Under the high load working condition, the tapered nozzle group is opened, and the machine group runs at [ L ]_x0,L_x]When the working condition is medium or low load, the convergent-divergent nozzle group is opened, steam expands in the convergent-divergent nozzle group and accelerates to supersonic speed, the operating pressure is greatly increased to the maximum allowable pressure, the operating efficiency is improved, and the pressure loss is reduced;

by utilizing the characteristic that the flow area of the inner ring nozzle channel is smaller than that of the outer ring nozzle channel, the tapered nozzle group is arranged in the outer ring nozzle channel, and the scaled nozzle group is arranged in the inner ring nozzle channel, so that when the nozzle groups are switched under the working conditions of high load and low load, the partial steam admission degree of the scaled nozzle group in the inner ring nozzle channel can be greatly reduced, and the efficiency of an adjusting stage 2 is improved;

in the two nozzle channels, the tapered nozzle groups can be divided into at least one pair of arrangement pairs in pairs, the flow areas of the tapered nozzle groups in the same pair of arrangement pairs are close or equal, the pair of tapered nozzle group arrangement pairs are symmetrically arranged along the axis or the center of the adjusting stage 2, and similarly, the pair of tapered nozzle group arrangement pairs with similar or equal pressure ratios are symmetrically arranged along the axis or the center of the adjusting stage 2, and the tapered nozzle groups are sequentially and alternately arranged in the circumferential direction of the adjusting stage 2, so that the mutual acting force generated when the nozzle groups flow steam can be effectively balanced, and the running stability of the steam turbine set is improved;

determining the upper load rate boundary L of the working load interval of the scaling type nozzle group_xTo respectively define the design workload interval [ L ] of the tapered nozzle set_xAt full load]And the design workload interval [ L ] of the convergent-divergent nozzle group_x0,L_x]Then calculating to obtain the total flow area A of the tapered nozzle_1～m1+m2And obtaining the flow area A corresponding to each tapered nozzle group according to the number of the tapered nozzle group combinations₁～A_m1+m2Finally, calculating the flow area A' corresponding to each zoom type nozzle group according to the combined number of the zoom type nozzle groups₁～A`_{(n1-m1)+(n2-m2)}Thereby determining the throughflow of each nozzleArea;

The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.

Claims

1. The utility model provides a turboset with binary channels regulation level, includes main vapour valve and high-pressure cylinder, the main vapour valve is connected the high-pressure cylinder, be equipped with the regulation level in the high-pressure cylinder, its characterized in that, the regulation level is equipped with first nozzle passageway and second nozzle passageway, first nozzle passageway and second nozzle passageway are arranged along radial from inside to outside, first nozzle passageway and second nozzle passageway are equallyd divide and are equipped with gradual shrinkage type and/or scale type nozzle group respectively, main vapour valve and each be equipped with adjusting valve between gradual shrinkage type nozzle group, the scale type nozzle group.

2. A turbo-set with a dual channel regulation stage according to claim 1, characterized in that the regulation stage is provided with a pressure stage set comprising a first stationary blade cascade, a second stationary blade cascade and a moving blade cascade, the first nozzle channel outlet being provided with the first stationary blade cascade, the second nozzle channel outlet being provided with the second stationary blade cascade, the first stationary blade cascade corresponding to an inner ring part of the moving blade cascade, the second stationary blade cascade corresponding to an outer ring part of the moving blade cascade, the first stationary blade cascade and the second stationary blade cascade sharing the moving blade cascade.

3. A turbo-steam turbine plant with a two-channel regulation stage according to claim 1, characterized in that the regulation stage is provided with a first pressure stage group and a second pressure stage group, which are connected in series, the first nozzle channel being connected to the first pressure stage group and the second nozzle channel being connected to the second pressure stage group.

4. A turbo-set with a two-channel regulation stage according to claim 1, characterized in that the second nozzle channel is constituted by a number of convergent-divergent nozzle groups, the first nozzle channel is constituted by a number of convergent-divergent nozzle groups, after which convergent-divergent nozzle groups a speed-recovery stage is arranged, which comprises at least two rows of moving blades.

5. The turboset with two-channel regulation stage according to claim 1, characterized in that the first nozzle channel is constituted by 0 or an even number of sets of convergent nozzles and 0 or an even number of sets of convergent nozzles; the second nozzle channel is composed of 0 or even number of convergent-divergent nozzle groups and 0 or even number of convergent-divergent nozzle groups.

6. The turboset with a two-channel regulation stage according to claim 5, wherein in the first nozzle channel and/or the second nozzle channel, the plurality of tapered nozzle groups are divided into at least one pair of arrangement pairs according to the two tapered nozzle groups, and the two tapered nozzle groups belonging to the same arrangement pair are arranged axially symmetrically along a certain diameter of the circular cross section of the regulation stage or arranged centrosymmetrically with the center of the circular cross section;

the two zooming type nozzle groups are divided into at least one pair of arrangement pairs according to the fact that the two zooming type nozzle groups are a pair, and the two zooming type nozzle groups in the same arrangement pair are arranged in an axial symmetry mode along a certain diameter of the circular section of the adjusting stage or in a central symmetry mode through the circle center of the circular section.

7. Steam turbine plant with two-channel regulating stage according to claim 6, characterized in that the set of convergent and convergent nozzles is arranged along the circumference of the regulating stage and in succession alternately in the circumference of the regulating stage.

8. Turboset with two-channel regulating stage according to any one of claims 5 to 7, characterized in that the number of tapered nozzle groups in the first nozzle channel is m₁Each tapered nozzle group has an outlet cross-sectional area S, and S₁≤S₂≤S₃≤…≤S_m1；

9. Turboset with two-channel regulating stage according to any one of claims 5 to 7, characterized in that the number of tapered nozzle groups in the second nozzle channel is m₂Each of the tapered nozzle groups has an outlet cross-sectional area S' and S ″₁≤S`₂≤S`₃≤…≤S`_m2；

the cross section area of the outlet corresponding to two tapered nozzle groups in the same arrangement pair group is S ″_iAnd S_i+1Wherein i is [1, m ]₂]Odd number of (1);

10. A calculation method for calculating the flow area of a nozzle block in a first nozzle duct and in a second nozzle duct of a steam turbine group with a two-duct regulating stage according to one of claims 1 to 9, comprising the following steps:

11. A method of computing according to claim 10, wherein:

in determining the lower load boundary L of the convergent nozzle group workload interval, the method comprises the following steps: let P_0,maxThe steam turbine set is allowed to have the maximum main steam pressure, r is a pressure loss coefficient caused by steam flowing through a main steam valve, and the value of r is 0-10%; critical pressure ratio of nozzle group according to formula

Calculating, wherein k is the isentropic index of the superheated steam, and the value is 1.2 to 1.5; resetting the inlet pressure P of the regulating stage₁＝P_0,maxX (1-r) according to critical pressure ratio pi of nozzle group_crDetermining the load L such that the load has a lower regulating-stage back pressure P_bSatisfy P_b/P₁＝Π_cr；

Determining the flow area A' corresponding to each zoom type nozzle group₁～A`_{(n1-m1)+(n2-m2)}The method comprises the following steps: combining and designing the scaling type nozzle groups with the same pressure ratio, and setting the working load interval [0, L ] of the scaling type nozzle groups according to the combination of the scaling type nozzle groups_x]The inner valve point obtains the regulating stage back pressure P under the working condition of the valve point_bMain steam flow rate D_xAnd setting the main steam pressure to the design pressure P_0,maxThe main valve pressure loss is r. Obtaining the total flow area A of the combination of the convergent-divergent nozzle groups according to a convergent-divergent nozzle flow pressure ratio relation:

wherein D is_xThe unit is the main steam mass flow at the load, and the unit is kg/s; a is the total flow area of the convergent-divergent nozzle group combination, i.e. the total throat area, in m²；Π_crIs the critical pressure ratio.

Determining partial steam admission e of the first and second nozzle groups₁、e₂And leaf height of leaf height l₁、l₂The method comprises the following steps:

the outer diameter of the baffle of the stationary blade grid of the adjusting stage is D₀The first and second diameters of the annular channel of the first nozzle are respectively D₀、D₁In which D is₀<D₁(ii) a The first and second diameters of the annular channel of the second nozzle are D₂,D₃Wherein D is₁<D₂，D₂<D₃At this time, the following relation should be satisfied:

12. A method for operating a turboset having a two-channel regulating stage, comprising the following steps:

in [ L ]_x0,L_x]In the load interval, dividing a plurality of operation load intervals of the scaling-type nozzle groups according to the number of valve points operated by the scaling-type nozzle groups, binding each operation load interval of the scaling-type nozzle groups to one of the set arrangement combinations of the scaling-type nozzle groups, and in each operation load interval of the scaling-type nozzle groups, operating the steam turbine set in a sliding pressure operation mode until the load is reduced to the position of the next valve point;

13. Method for operating a turboset with two-channel regulation stage according to claim 12, characterized in that the selective result of the area-combining of the sets of convergent or convergent nozzles comprises valves with valves not completely closed or valves not completely open, i.e. a certain overlap remains between the ascending and descending valve sequences.