From (16.1) follows the expression for determining the flow rate of fresh steam into the turbine at known values turbine power and steam consumption for heat consumption:
Variable steam extraction turbines have the following features:
1. Depending on the heat load, condensation And cogeneration modes. For the heating mode, depending on the heat load, the turbine can operate according to thermal or electrical schedules. In the first case, the regulators of the LPR are in a stationary state, and the change in the load of the heat consumer and the power of the turbine is provided by the steam distribution elements of the LPR. In this case, a mode is possible when the LPP regulators are closed and all steam is sent to the heat consumer. Only the ventilation flow of steam is directed to the LPH to cool its body and rotor. In operating modes according to the electrical schedule, the LPC regulators can have an arbitrary degree of opening.
2. To prevent emergencies a safety valve is installed on the steam pipeline connected to the controlled extraction chamber. In addition to it, due to the large volume of the steam pipeline, check valves must be installed to prevent the return flow of steam into the turbine during its emergency shutdown.
3. In turbines with controlled steam extraction, due to the variety of modes, nozzle steam distribution is used.
Diagram of turbine regimes with one controlled steam extraction shown in fig. 16.6.
Turbine power determined from the curve ab, corresponds to operation with full steam extraction to the heat consumer ( G 2 =G k = 0). The ventilation pass of steam in LPH (5-10% of the calculated value) is determined by the line a 1 b 1. Grid of dotted lines ( a 1 b 1) determines the operating modes of the turbine with different steam extraction to the heat consumer (diagram area a12ba). Line a 11 b 11 represents the change in turbine power at the calculated passage of steam in the LPP (when the LPP regulators are fully open and the pressure r p (R m) is maintained constant). Line b2 determines the mode of operation with the maximum passage of steam through the HP. Line a 1 2 corresponds to a purely condensing mode of operation, when the steam flow to the extraction is zero. With the calculated passage of steam through the LPH, the maximum power of the turbine is determined by the point b 11(here, the steam flow rate through the HPC is maximum, and the calculated pass through the HPC is equal to G 20 =0,4G 10). Dot a 11 corresponds to the calculated passage of steam in the LPR in the condensing mode and determines the significantly lower power of the turbine, which it can develop at maximum flow through the LPR.
Rice. 16.6. Diagram of modes of the turbine T with controlled steam extraction
If we allow an increase in steam pressure in front of LPP (in controlled extraction), then a greater steam flow can be passed through it and even in the condensing mode, maximum power can be reached. N poppy s for which the generator is designed. In the mode diagram when skipping steam G 20 =0,4G 10 , which corresponds to the line a 11 b 11, the LPH control valves (or rotary diaphragms) will open fully and a further increase in the flow rate through the LPH is achieved by increasing the vapor pressure in the controlled extraction chamber.
To determine the flow rate of the extracted steam in an arbitrary mode (point A in fig. 16.6), the following construction is performed. Dot A in the diagram determines the flow rate of fresh steam into the turbine for a given mode ( G 1 =G o). passing through the point A a line of constant steam passage in the LPH, we will find it at the intersection of the line AB with line condensation regime point IN, which allows you to determine the passage of steam G 2 in CND. The flow rate of the extracted steam is found as the difference G n = G 1 -G 2. Lines of turbine regimes with a constant flow rate of extracted steam G n = const in the diagram are represented by thin solid lines. Sometimes in diagrams instead G P ( G r) lines of constant heat load are built Q t = G sv ( h pr -h about) determined from the values of the enthalpies of the straight line ( h pr) and inverse ( h about) network water passing through the network heater.
Presented turbines are made both with reheating of steam and without it. The gain from reheating here is less than that of condensing turbines, since it is determined in relation to the characteristics of the low pressure cylinder, the average annual steam flow through which is lower in turbines with controlled extraction. For turbines with production steam extraction, which changes little throughout the year, it is advisable that the condensing power be equal to the nominal value, and not more than it, which is typical for turbines with heating steam extractions. The dimensions of the last stage of the LPP of such turbines, with other equal conditions less than that of condensing ones, since turbine plants with heat-extraction turbines, which are usually installed within the city, have an increased temperature of the cooling water during the circulating water supply of the condenser and, accordingly, an increased pressure in the condenser.
On last page This lecture provides a simplified mode diagram that we will use when solving problems on practical exercises. It must be printed and brought to practice.
In contrast to turbines with backpressure, turbines with intermediate controlled extractions and a condenser can generate electricity regardless of the heat load.
Turbine with one selection.
1 part high pressure(ChVD);
2 - part low pressure CND);
3 - generator;
4 - capacitor;
5 - heat consumer;
6 - stop valve;
7 - control valve;
8 - LPH control valve;
9 - safety valve;
10 - shut-off valve;
11 - check valve.
CVP and LPC are groups of stages and can be located in one or different cylinders, respectively in the high pressure cylinder (HPC) and in the low pressure cylinder (LPC).
Fresh steam with parameters R o And t o, passing through valves 6 and 7, expands in the CVP to the pressure R p, which is kept constant. After HPT, the steam flow is divided into a flow G p And G to. the latter goes through 8 to the LPC, where it expands to the pressure in the condenser R to.
Relative internal efficiency of the entire turbine:
Let's define email. power excluding steam extraction for regeneration: N e = η m η eg Ni.
Internal power:
For turbines with controlled extraction it is possible
Condensing;
Heating.
The mode will be completely condensation, If G p= 0 and the turbine operates as a type K turbine. In this case, valve 8 is fully open, shut-off valve 10 is fully closed, load control is performed by valve 7. Shut-off valve 10 is not a control valve. Its possible position: fully open or fully closed.
The mode is called cogeneration, When G p> 0 and shut-off valve 10 is fully open. The necessary electric power at a constant current frequency and the thermal load are provided by the joint regulation of the degree of opening of valves 7 and 8.
As a special case of the heating mode, it is possible to work with backpressure, while the valve 8 is closed, and all the steam is directed to the controlled extraction. But a small amount of steam is forcibly passed in the LPH to remove the heat of friction from the LPH rotor. This steam pass is called ventilation. In the backpressure mode, the electrical load is completely determined by the load of the heat consumer.
Safety valve 9 serves to prevent mechanical damage in case of incorrect operation systems for regulating and exceeding the steam pressure in the extraction chamber in excess of the allowable. If valve 8 does not close during a sudden shutdown of the generator, then the steam from the extraction steam line can go back and enter the LPC and the condenser and can accelerate the turbine to a speed that causes its destruction. To prevent this from happening, a check valve 11 is installed. Forced closing of the shut-off valve 10 is provided.
Turbines with 2 intermediate adjustable steam extractions.
4) generator;
5) capacitor;
6) consumer of low-potential heat (heating extraction);
7) industrial consumer;
8) stop valve;
9) 10) control valve;
11) rotary diaphragm.
Let's depict the expansion process.
0-1 
– steam expansion in HP;
1-2 - throttling in valve 10;
2-3 - expansion in the FRR;
3-4 - throttling in diaphragm 11;
4-5 - expansion of steam in LPH.
Such turbines are characterized by an even greater variety of operating modes compared to turbines with 1 extraction. Available:
Condensing mode (10 and 11 are fully open and shut-off valves are closed);
- 
one of the selections is closed;
In LPC there is only a ventilation passage of steam (electric power is completely determined by the loads of thermal consumers).
Required at any given time e. power with a constant current frequency and thermal loads with given pressures R p And R t are provided by joint regulation of the degree of opening of valves 9 and 10 and diaphragm 11.
Valves 9 and 10 are servomotor operated valves.
The regulating body between the CSD and LPR is usually a rotary diaphragm 11 due to large volumes steam consumption. In this case, the CSD and CND are located in the LPC. In the closed position, some part of the ventilation steam passes into the LPC through small gaps between the blades and the diaphragm windows.
12) nozzle grate of the first stage of the LPH.
Modern cogeneration turbines with a capacity of 50 MW and above have two heating controlled steam extractions for staged heating of network water, carried out in several successively located heaters. The pressure of the extracted steam is determined by the temperature of the water at the outlet of each heating stage. For heating network water, 70-80% of the steam flow to the turbine is used, and the heating temperature is 40-50 °C.
circuit diagram turbine plants with two heating extractions (upper 4 and bottom 5) is shown in fig. 20.2, a. Fresh steam in quantity G O and with parameters p0, t0 is supplied to the turbine through the stopper 8 and regulating 7 valves. In ChVD 1 the steam expands to the pressure in the lower heating outlet 5 and then through the regulating element 6 heading to CND 2. The rest of the equipment of a turbine plant with two heating steam extractions is similar to a turbine with two adjustable steam extractions (Fig. 20.1).
Rice. 20.2. circuit diagram (A) and steam expansion process (b) V h,S- turbine shutdown diagram with two-stage steam extraction.
To the top selection 4 steam with flow G 1 taken at pressure R 1 and with enthalpy h 1 (Fig. 20.2, b), and in the lower one - steam with a flow rate G 2 with parameters R 2 And h 2 . Since there is only one LPR regulator in the turbine, then adjustable pressure at the same time, it can be maintained only in one of the two heating steam extractions: in the upper one - when both extractions are turned on, in the lower one - when the lower extraction is turned on.
Installation for heating network water consists of two heaters (boilers) 9 And 10 surface type. The required temperature of the network water sent to the heat consumer is determined by the steam pressure of the upper extraction. The distribution of the heat load between the upper and lower extractions is determined by the network water temperatures before and after the network heaters, the network water flow rate and the electrical load.
Turbine internal power N i , kW, with two heating taps the pair is determined from the expression (regenerative selections are not taken into account)
N i = N uh / η m η eg = N i " + N i " "+N i """ =
= G o H 0 "η 0i " + (G O –G 1 )H 0 ""η 0i "" + (G O –G 1 –G 2 )H 0 """η 0i """ (20.3)
, kW, isQ t \u003d W c c in (t 2s -t 1s) \u003d G 1 (h 1 -h 1 " ) + G 2 (h 2 -h 2 " ), (20.4)
Where G O ,G p ,G t - steam flow to the turbine, to the upper and lower heating extractions, kg/s; H 0 " , H 0 "" , H 0 """- available turbine stages up to the upper outlet, between the outlets and LPR , kJ/kg; W with - network water consumption, kg/s; c to\u003d 4.19 kJ / (kg K) - heat capacity of water; t 2s,t 1s- water temperature at the inlet and outlet of the heaters, deg; h1, h2 - steam enthalpy in the upper and lower heating extractions, kJ/kg; h1 " , h2 " - enthalpy of condensate of heating steam in heaters 9 And 10, kJ/kg.
Turbines with two-stage steam extraction can have a variety of heating modes of operation depending on the ratio of thermal and electrical loads. In operating modes according to the thermal schedule at a given heat load Q t regulatory body 6 before CND is closed. The turbine power is determined by the thermal load, and the steam flow through the LPR is limited by the value G k.min determined by the conditions reliable operation turbines. When the turbine is operating according to the electrical schedule an independent change in thermal and electrical load is possible. Regulatory body 6 partially or completely open, which allows, with a constant thermal load, to pass through the turbine additional expense fresh steam entering through the LPC into the condenser 3 (Fig. 20.2). This flow provides additional power compared to the heat curve operation with the same heat load. Thus, the steam flow rate through the LPC depends on the given electrical load.
20.3. APPLICATION OF INTEGRATED BEAMS IN CONDENSERS OF HEATING TURBINES
In turbines with controlled steam extraction, when operating with a thermal load, zero steam flow to the condenser is not allowed. Minimum Pass, which serves to cool the LPP stages, is determined turbine design(size of LPP blading, density of LPP regulators, etc.) and its mode of operation(vacuum, pressure in the sampling chamber).
The heat of the steam entering the condenser is transferred to the circulating water and is not used in the power plant cycle. The heat of the steam entering the heat exchangers located on the recirculation line is also transferred to the circulating water: stuffing box heater and ejector coolers. To utilize this heat, which is commensurate with the heat of the maximum steam passage into the condenser, part of the condenser surface is released into a special heating beam. The beam tube is provided with a supply circulating water, and water heating networks. The embedded beam surface is approximately 15% total area the surface of the condenser.
The design of the condenser with a built-in bundle, which has independent water chambers and a steam space common with the main surface, is a typical solution for cogeneration turbines with a capacity of 50 MW and more.
Schematic diagram of a turbine plant with a built-in heat extraction beam in the condenser shown in fig. 20.3, a. To main condenser tube bundle 8 supply of only circulating water is provided, and to the built-in bundle 11 - circulating water and water of heating networks (reverse network or make-up). The rest of the turbine plant equipment has the same purpose and image as in a turbine plant with two-stage steam extraction (Fig. 20.2).
In the mode with condensing power generation only circulating water enters the main and built-in bundles. When working on a heat schedule the circulation water supply to the main and built-in bundles is turned off, and the built-in bundle is cooled by network or make-up water. In this case, the regulator 6 NPV (Fig. 20.3 ,a) is closed and the turbine operates in a mode similar to that of a backpressure turbine.
Rice. 20.3. Schematic diagram (a) and steam expansion process (b) V h,S- a diagram of a turbine plant with a two-stage steam extraction and a built-in heating bundle.
At the same time, the possibility of independent setting of thermal and electrical loads is excluded, since the electric power of the turbine in this mode of operation is determined by the value and parameters of the thermal load.
Switching the turbine to operation using the built-in beam causes a redistribution of pressures and heat drops over the turbine stages. On fig. 20.3, b shows the thermal process of steam expansion in the turbine in h,S-diagram when operating in condensing mode(dashed lines) and switched on heating beam(solid lines). For high pressure turbines operating mode with built-in beam on is associated with an increase in pressures in controlled extractions ( R 1 >R 1 "; R 2 >R 2 "), which leads to a decrease in the power generated on the steam flows to the extractions. In the LPP of the turbine, due to the deterioration of the vacuum in the condenser, the available heat drop sharply decreases ( H 02 " > H 02 ), and its stages operate with a large ratio of speeds i/s f and lower efficiency. IN individual cases energy losses in LPR exceed its available heat drop and LPR stages operate with negative efficiency and consume power (line 1-2 in fig. 20.3b). Under such modes, due to the increase in the temperature of the steam passing through the LPH, the temperature regime turbine exhaust pipe.
CPC. MODE DIAGRAM
IN general case mode diagram expresses in graphic form the relationship between the electric power of the turbine N i, steam consumption G O, thermal load of the consumer Q p (Q t), steam pressure released to the consumer R n(p t), live steam parameters р 0 , t 0, cooling water consumption W With etc., which determine the operation mode of the turbine plant:
F(N e, G 0 , W s, Q p, Q t, R n, p m...) = 0. (1)
Equation (1) is graphically represented on a plane if the number of variables does not exceed three. Otherwise, the image of the diagram of regimes on the plane can be obtained only by replacing the actual relationship of variables with approximate dependencies, which introduces an error into the diagram the greater, the more more number variables of equation (1). Therefore, it is advisable to limit the number of independent parameters involved in the mode diagram. When limiting the number of variables in equation (1), it is taken into account that the influence of individual parameters on power is not the same. For ultimate high precision the mode diagram is performed in the form of several independent graphs. Main chart, commonly called mode diagram , expresses the relationship between turbine power N e and steam consumption G 0 . Additional charts, called correction curves to the mode diagram , determine the effect of changing each of the other parameters of equation (1) on the turbine power. IN the composition of the regime diagram includes also some auxiliary curves: temperature dependence feed water from the flow rate of live steam, the possible minimum pressure in the controlled extraction from the steam and extraction rates, etc.
The main diagram can be made with high accuracy since the number of variables is limited. Correction curves are usually performed with some error. However, the error of the correction curve slightly increases the overall error of the regime diagram, since absolute value the corrections themselves are, as a rule, a few percent of the total power of the turbine.
The presence of the mode diagram allows you to graphically establish the relationship between the parameters of equation (1) and highlight the area of possible modes of operation of the turbine plant. The clarity of presentation, ease of use and sufficient accuracy determined the widespread use of the regime diagram in the design and operation of thermal power plants.
CPC 19.1. Type P backpressure turbine regime diagram. The mode diagram expresses live steam consumption dependence G0 from electric power N e and backpressure r p :
G 0 \u003d f (N e, p p). (2)
which can be represented on a plane in accordance with the available experimental or calculated data. Of the three parameters of equation (2), the final vapor pressure has the least influence r p , and therefore the diagram of the regimes of the turbine with backpressure is performed (Fig. 19.1 SRS) in the form of a grid of curves G 0 \u003d f (N e) , obtained as a result of the intersection of the three-dimensional surface described by equation (2), the planes r p = const.
Rice. 19.1 SRS. Diagram of turbine regimes with backpressure.
SRS 19.2. Diagram of turbine regimes with one controlled steam extraction. In general, the mode diagram expresses electrical power dependence N e from the steam flow to the turbine G0, in selection G p and steam pressure in selection r p.
G 0 \u003d f (N e, G p, r p). (3)
Extraction pressure can be eliminated from this equation r p , replacing its influence with correction curves, which can be performed with a relatively small error. Then dependence (3) can be plotted on a plane in the form of a series of curves G 0 \u003d f (N e) at G p = const.
Consider an example of constructing a regime diagram for a turbine with steam extraction an approximate method based on the use of a linearized dependence of the steam flow to the turbine G0 from power N e and steam consumption in extraction G p:
G 0 \u003d G ko + y p G p \u003d G c.x + r to N e + y p G p \u003d G c.x + d n (1- x)N e + y p G p (4)
Where G ko = G c.x + r to N e - steam flow to the turbine in the condensing mode of operation without extraction; G k.x - steam consumption at idling of the turbine without extraction; r to =(G0 - G k.x )/N e - specific increase in steam consumption in the condensing mode, kg/(kWh); y p = (h p -h k) / (h 0 -h to) - the ratio of the used heat drops of the LPP and the entire turbine (the coefficient of underproduction of power by the extraction steam); d n =G nom/N nom- specific steam consumption at rated load and condensing mode of operation, kg/(kWh); x=G x.x /G0 - idle ratio.
The mode diagram is based on the boundary lines constructed for the most typical turbine operation modes.
condensation mode. Mathematically, the dependence of steam consumption on power is determined by expression (5) at G p =0:
G 0 \u003d G ko \u003d G k.x + d n (1- x) N e (5)
Graphically (Fig. 19.2 SRS) the condensation mode line is constructed using two points: the point TO, the ordinate of which corresponds to the maximum passage of steam into the condenser at rated electric power N nom, and point About 1 , which determines the steam flow to the turbine G k.x at zero power (idle). On the abscissa axis, the condensation regime line passing through the points TO And About 1 , cuts off a segment O O 2 , conditionally determining turbine power losses Δ N x.x to overcome the idle resistance.
In reality, dependency G 0 \u003d f (N e) in the condensation mode it differs from a straight line and has more complex view, determined by the steam distribution system, the nature of the change in the internal relative efficiency, the temperature of the steam exhausted in the HP, etc.
Turbine operation mode with backpressure. The change in steam flow to the turbine is determined by expression (5) at G to =0 And G0 =G p:
G 0 \u003d G o.p \u003d G p \u003d G c.x + d n (1- x) N e + y p G 0,
G 0 \u003d G k.x/(1- y p) + d n (1- x) N e /(1- y p) \u003d G p.x + r p N e (6)
G ko + y p G p \u003d G k.x + r to N e + y p G p \u003d G k.x + d n (1- x)N e + y p G p
Where G p.x =G k.x /(1-y p) - steam consumption for idling in the mode with backpressure, kg/s; r p = r to (1- y p) - specific increase in steam consumption during turbine operation with backpressure, kg/(kWh).
Since the underproduction rate y p is always less than unity, the steam flow rate for idling and the specific increase in steam flow rate when the turbine is operated with back pressure is higher than in the condensing mode in (1 /(1- y n)) once: G p.x >G k.x , r p >r to.
This is explained by a significantly lower heat drop in the turbine before extraction compared to the total heat drop before the condenser and, accordingly, a large specific steam consumption.
Rice. 19.2 SRS. Diagram of turbine regimes with one controlled steam extraction.
The approximate dependence of steam consumption on power in the case when all the steam after the CVP enters the selection, in the mode diagram (Fig. 19.2 SRS) is represented by a straight line passing through the point About 2, characterizing the loss of power at idle, and the point About 3 , wherein G p.x =G0. Dot At 0 , lying on the line of the condensation regime G to = 0 corresponds to the operation mode with the maximum steam flow through the turbine.
In reality, when the turbine is operated with back pressure, a small amount of steam is passed through the condenser. G c.min, which is determined by the conditions for the reliable operation of the elements of the LPP of the turbine (5-10% of the steam flow to the turbine). The straight line K o V , parallel O 2 V 0 and below it. Point ordinate K o characterizes the minimum passage of steam into the condenser G c.min.
Operating mode with constant steam extraction(G p = const). The characteristics of a turbine with constant steam extraction are built according to equation (4). From the comparison of expressions (4) and (5) it is easy to establish that the characteristics of the condensation mode and the mode of operation with constant extraction differ from each other by a constant value y p G p . Therefore, on the mode diagram, the lines depicting the mode G p = const, will be located parallel to the condensation mode line.
The left boundary of the turbine characteristics at G p = const serves as a line of operation of the turbine with back pressure, on which G p = G c.min(in the absence of unregulated steam extractions), and on the right - the line KV n constant rated turbine power N nom. Top part mode diagram is limited to a segment VV n on the line of maximum steam passage through the turbine G 0max = const between lines G c.min = const And N nom = const.
Rated steam extraction G p nom corresponds to the rated electric power N nom and maximum steam flow to the turbine G 0max (dot V n ). If the maximum steam flow to the turbine is achieved when operating with backpressure at an electric power less than the nominal one, then steam extraction is possible more than the nominal one, the so-called limiting extraction, determined at the point IN line crossings G c.min = const And G 0max = const.
In addition to the obligatory family of lines that determine the dependence of the turbine power on the steam flow rate at different values selections G p = const, the mode diagram has a grid of lines G to = const at constant steam flow rates to the condenser (LPD). lines G to = const are straight lines parallel to the characteristic of the turbine operation mode with backpressure G c.min = const. Of this family of lines, the line G k.max = const, corresponding to the maximum passage of steam into the condenser. Typically, a condensing heat and power turbine requires full development electric power in purely condensing mode. In this case, the bottom line of the diagram G p = 0 reaches the line N nom = const at the point TO at G To =G k.max. If the steam extraction is stable and ensured for a long period of turbine operation, then the lower boundary of the right part of the diagram is the line G k.max = const running parallel to the line G c.min = const above point TO line crossings G p = 0 And N nom. In this case, the rated electric power is achieved at a certain selection value.
With the simultaneous maximum passage of steam through the HP and LPP, the turbine can develop maximum power N Max. This power is determined by the abscissa of the point In t line crossings G 0max = const And G k.max = const. The maximum power of the turbine is regulated up to 20% higher than the nominal one.
If we accept that the steam flow through the LPC should not exceed the maximum, then from the diagram (Fig. 19.2 SRS) it can be seen that in the condensation mode ( G p = 0 ) turbine power (point K 1 ) will be less than the maximum. Such a limitation of the power of the turbine with controlled steam extraction when operating in the condensing mode is unjustified. The rated power in the condensing mode can be obtained by increasing the passage of steam through the LPH, which is ensured by increasing the steam pressure before the LPH. Modes with steam flow rates through the LPP that exceed its throughput at fully open LPP control bodies and the nominal steam pressure in controlled extraction are allocated in the regime diagram in the area " high blood pressure in controlled selection”, which in Fig. 19.2 SRS shaded.
The mode diagram allows one to determine the third one by two given terms of expression (3). Determination of the flow rate of extracted steam G p N uh and steam consumption G0 happens as follows. According to famous N uh And G0 find a point A , characterizing the given mode of operation of the turbine. Through the dot A conduct a line of constant passage of steam in the LPH. Point ordinate WITH intersection of this line and the line of the condensation regime G p = 0 determines the steam flow rate in LPH G to . The flow rate of the extracted steam is found as the difference G p =G0-G to .
Fresh steam consumption G0 with known turbine power N uh and consumption of extracted steam G p determined by the ordinate of the intersection point of the lines
N e = const And G p = const.
Turbine power N uh at known flow rates of fresh and exhaust steam G0 And G p determined by the abscissa of the point of intersection of the lines G0 = const And
G p = const.
CPC 20.1. Diagram of turbine regimes with two adjustable steam extractions. N uh, steam consumption for the turbine G0 , steam consumption in the upper (production) and lower (cogeneration) extractions G p And G T:
G 0 \u003d f (N e, G p, G T). (1)
The influence of other parameters of equation (1) is taken into account by correction curves.
When constructing a turbine mode diagram with two controlled steam extractions, it is conditionally replaced by a fictitious turbine with one upper steam extraction. The heat extraction is assumed to be zero, and the steam is sent to the LPR of the turbine and produces additional power there.
ΔN t = G t H i "" η m η eg = kg t (2)
Where H i "" - used heat drop LPH; k - coefficient of proportionality.
Taking into account (2), expression (1) can be reduced to the form
N e = N e conv - ∆N t = f(G0 , G P) - G t H i "" η m η eg (3)
Where N e conv. =f(G0 , G P)- the power developed by the conditional turbine at zero heat extraction.
The regime diagram corresponding to expression (3) can be performed on a plane in two quadrants as follows (Fig. 6.9). Dependence is built in the upper quadrant G 0 \u003d f (N e conv. , G p) , which expresses the regime diagram of a conditional turbine when operating with zero steam flow to the heating extraction. Its construction is carried out in the same way as for a turbine with one steam extraction (Fig. 19.2 SRS). lower bound this diagram is the production selection line Gn = 0 . From above, the diagram is limited by lines of maximum steam flow to the turbine G 0max = const and in production selection G p.max = const, as well as the line G chsd, which characterizes the amount of steam included in the CSD .
Rice. 20.1 SRS. Diagram of turbine regimes with two adjustable steam extractions.
In the lower quadrant, according to (3), a line is drawn OK , linking the lower heating extraction G T with extra power ∆N T, and a grid of lines parallel to it is applied. In addition, limiting lines are applied here. G p = const for heating extraction. They represent the maximum possible production selection. G p.max, which is determined from the total steam balance of the turbine, provided that the steam flow rate at the outlet of the CSR does not exceed the heat extraction by the amount required to cool the LPR stages:
G t.max = G 0max -G p -G kmin .(4)
The construction of these limiting lines is performed as follows: from arbitrarily chosen points 1 And 2 for the same value G p = const draw vertical lines down. points 1" And 2" the intersections of these lines with the values G t.max, calculated by formula (4), are combined for one value G p = const straight line, which is the boundary of possible regimes. From below it, the operation of the turbine is unacceptable due to G T > G t.max .
Using such a diagram (Fig. 20.1 SRS), it is possible to find the fourth one for a turbine with two controlled steam extractions using three known quantities of equation (1). Let, for example, given N uh, G p, G t. Wanted to find G0 . First by N uh And G T find N f: from a point A given power N uh direct AB, parallel OK, before crossing the line constant flow G p = const. Line segment AC depicts the additional power generated by the LPR due to the additional passage of steam in the amount G T. Fictitious turbine power N f is determined at point C. Using top mode diagrams, according to N f determine the required steam flow to the turbine G0 as the ordinate of a point D intersections N f = const And G p = const.
CPC 20.2. Diagram of turbine regimes with two heating steam extractions. The diagram expresses the relationship between turbine power N uh, thermal load Q t, steam consumption for the turbine G0 , network water temperature t s going to the consumer:
F(N e , Q t, G0, t c)=0. (5)
The regime diagram is built according to the method of dividing the flow rate of live steam into two streams: G t 0 and condensation G To 0 . Accordingly, the power of the turbine is conventionally assumed to be equal to the sum of the powers of the heating plant. N te and condensation N to e streams. With this in mind, dependence (5) can be represented as following form:
G0 = f 2 (N te , t 2s) +f 3 (N to e) (6)
The mode diagram is built in three quadrants (Fig. 20.2 SRS).
Rice. 20.2 SRS Diagram of turbine regimes with two heating steam extractions.
The first (top left) shows the dependence of the steam flow on the turbine on the heat load when operating according to the heat schedule G t 0 = f 1 (Q t, t 2s). The second (upper right) quadrant shows the dependence of the steam flow to the turbine on its power at various values t 2s and work on thermal G t 0 = f 2 (N t e, t 2s). The third (lower) quadrant characterizes the operation of the turbine according to the electrical graph and expresses the dependence of the condensing steam flow on the power generated by this flow G to 0 = f 3 (N to e). The total steam flow to the turbine in accordance with (20.2 SRS) is found by summing the steam flow rates obtained in the second and third quadrants. In the third quadrant, a line is also applied for the purely condensing mode of the turbine without thermal load (line A ), which lies below the lines G to 0 = f 3 (N to e).
Examples of using the turbine mode diagram with two heating steam extractions:
1. Determination of turbine power and steam consumption during turbine operation according to the heat curve and known heat load Q t and network water temperature t 2s.
According to the given values Q t And t 2s carried out in quadrants I And II broken line ABCDE(Fig. 20.2 SRS). In the quadrant I at point C find the steam flow G t 0, and in the quadrant II at the point E - turbine power N te.
2. Determination of the steam flow rate for a turbine operating in the condensing mode, with known heat load Q t, power N uh and network water temperature t 2s.
According to the given values Q t And t 2s determine the power N te generated by the steam heat flow. The difference between the given power N uh and found value N te determines the power N to e developed by the condensing steam flow. It corresponds to the segment HEDGEHOG in fig. 20.2 SRS. Then, drawing from the point E line equidistant from the dependency G to 0 = f 3 (N to e), at the point AND its intersection with the line N uh = const find the flow rate of the condensing steam flow G to 0(point coordinate AND in the quadrant III in fig. 20.2 SRS). The steam flow rate for the turbine is determined by summing the values G to 0 And G t 0.
3. Determination of the steam flow to the turbine when the turbine is operating in a purely condensing mode G to 0 according to the given power N uh.
In the quadrant III by known power N uh and curve A determine the desired value of steam flow G to 0(line LMN).
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| Turbine type | Sampling No. Preheater | Pressure, MPa | Temperature, °С | Amount of extracted steam, kg/s |
| PT-12-35/10 (APT-12-1) | 1st selection (PVD) for 5 st 2nd selection (deaerator) for 11 st 3rd selection (HDP) for 13 st | 0,56 0,12* 0,0098 | 2,64 0,97 0,194 | |
| PT-12-90/10 (VPT-12) | 1st selection (PVD No. 5) for 5 st 2nd selection (PVD No. 4) for 9 st 3rd selection (deaerator) * for 12 st 4th selection (HDP No. 3) for 15 st 5th selection (PND No. 2)* for 19 st 6th selection (PND No. 1) for 21 st | 2,51 1,49 0,98/0,59 0,32 0,12 0,007 | 1,22 1,36 0,055+0,47** 0,55 0,22 0,3+0,3** | |
| PT-25-90/10 (VPT-25-3) | 1st selection (PVD No. 5) for 5 st 2nd selection (PVD No. 4*, deaerator*) for 9 st 3rd selection (PND No. 3) for 12 st 4th selection (PND No. 2)* for 15 st 5th selection (PND No. 1) for 17 st | 2.11 0.98/0.59 0.32 0.12 Off | 3,17 1,14/1,11 1,14 0,39 | |
| PT-25-90/10 (VPT-25-4) | 1st selection (PVD No. 5) for 9 st 2nd selection (PVD No. 4) for 13 st 3rd selection (deaerator)* for 16 st 4th selection (HDP No. 3) for 19 st 5th selection (IPA No. 2)* for 21 st 6th selection (IPA No. 1) for 22 st | 2.65 1.57 0.98/0.59 0.24 0.12 Off | 1,57+0,71** 2,39 0,42 0,69 0,33 | |
| PT-60-90/13 | 1st selection (HPA No. 7) for 8 st 2nd selection (HPA No. 6) for 12 st 3rd selection (HPA No. 5*, deaerator*) for 15 st 4th selection (HPA No. 4) for 18 st 5th selection (PND No. 3) for 20 st 6th selection (PND No. 2)* for 24 st 7th selection (PND No. 1) for 26 st | 3,72 2,16 1,27/0,59 0,64 0,36 0,12 0,007 | – | 6,11 4,44/3,05 – 5,83 0,55 – |
| PT-60-130/13 | 1st selection (HPA No. 7) for 9 st 2nd selection (HPA No. 6) for 13 st 3rd selection (HPA No. 5*, deaerator*) for 17 st 4th selection (HPA No. 4) for 20 st 5th selection (PND No. 3) for 22 st 6th selection (PND No. 2)* for 26 st 7th selection (PND No. 1) for 28 st | 4,41 2,55 1,27/0,59 0,56 0,33 0,12 0,006 | – | 5,83 (21) 6,11 (22) 3,89/0,55 3,33 4,17 0,55 – |
| PT-50-130/7 (VPT-50-4) | 1st selection (HPE No. 7) for 9 st 2nd selection (HHP No. 6) for 11 st 3rd selection (HHP No. 5) for 13 st 4th selection (HPE No. 4*, deaerator*) for 16 st 5th selection (PND No. 3)* for 18 st 6th selection (PND No. 2)* for 20 st 7th selection (PND No. 1) for 22 st | 3,33 2,16 1,4 0,69/0,69 0,21 0,093 0,045 | – – | 3,11+0,42** 3,03 3,52 0,83+15,3**/0,55 1,96 0,36 0,083 |
* Steam from adjustable selections
** Steam from seals
Table XIII-15
limits tolerances initial parameters of steam and temperature of intermediate overheating of steam (according to GOST 3618-82)
Note. The operating conditions of the turbines when the parameters are reduced beyond the limits indicated in the table, which may occur with a decrease in the steam output of the boiler, must be established in the regulatory and technical documentation for the turbine.
Table XIII-16
Limits of regulation of steam pressure in selections
and behind the backpressure turbine (according to GOST 3618-82)
Note. At turbine operating modes with a restriction of any steam extraction, it is allowed to increase its absolute pressure above the upper control limit. The permissible pressure increase is set in the regulatory and technical documentation for turbines of specific sizes.
INTRODUCTION
1.1. Settlement and explanatory note
1.2. The grafical part
2. PRELIMINARY CALCULATIONS
2.1. Determination of economic power and preliminary
steam consumption estimate
2.2. Selection of control stage type and its heat drop
2.3. Construction of the turbine expansion process. Consumption refinement
2.4. Determination of the power limit of the turbine and the number of exhausts
2.5. Determination of the number of unregulated turbine stages and
their heat drops
2.5.1. Preliminary calculation of FPV
2.5.2. Preliminary calculation of HR
2.5.3. Preliminary calculation of NPV
3. DETAILED CALCULATION OF THE FLOW PART
4. CALCULATION OF THE LAST STAGE TWIST
5. STRENGTH CALCULATIONS
5.1. Determination of the axial force on the rotor
5.2. Calculation of the last stage blade
5.3. Calculation of the aperture of the first unregulated stage
5.4. Calculation of the disk of the last stage
5.5. Bearing calculation
6. INDIVIDUAL TASK
6.1. Organization of unregulated heat extraction
6.2. Transfer of the condensing turbine to a degraded vacuum
CONCLUSION
Annex I
Appendix II
Page 1
Regulated steam extraction is made from below from the exhaust pipe of the high-pressure cylinder at a pressure of 6 - 8 atm. In addition, there are two unregulated extractions in the low pressure cylinder after the 10th and 13th stages, from which steam enters the feed water heaters. The high-pressure preheater receives steam from controlled extraction in excess of the amount used for production.
Regulated steam extraction from AP turbines has an industrial purpose; for AT turbines, the controlled extraction is intended for heating purposes.
The mode of controlled steam extraction should be such that the turbine always operates with the extraction value close to the nominal one. With a small amount of extraction, it is necessary to check the economic feasibility of keeping the turbine plant in operation.
Regulated steam extraction pressure is the steam pressure in the turbine extraction pipe in front of the shut-off valve.
The pressure of controlled steam extraction is its pressure in the nozzle of the turbine casing through which the extraction is made. The nominal value of the selection is called the largest number steam taken from the turbine, which must be provided at its nominal power.
The turbine had an adjustable steam extraction (important for district heating) from 1 to 2 atm.
Turbines without controlled steam extraction are marked with a star.
The nominal value of the controlled steam extraction from a turbine with one controlled extraction is the largest extraction value at which the turbine develops its rated power; a turbine with two variable steam extractions must develop its rated power at the nominal values of both variable steam extractions.
Rotary diaphragms of adjustable steam extractions are checked before installation in the turbine cylinder. To do this, the assembled diaphragm is placed on the lining so that the side of the steam inlet into the nozzles is located on top. Then a swivel ring is assembled on the diaphragm and through its windows the tightness of the sealing belts is checked. The probe plate with a thickness of 0 05 mm should not pass into their joint. The required density of the joint is achieved by scraping the belts, first by paint, and then by gloss.
Turbines without controlled steam extraction are marked with an asterisk.
Rotary diaphragms of controlled steam extractions are checked before they are installed in the turbine cylinder. To do this, the assembled diaphragm is placed on the lining so that the side of the steam inlet into the diaphragm nozzles is located on top. Then a swivel ring is assembled on the diaphragm and through its windows the tightness of the sealing belts is checked. The probe plate with a thickness of 0 05 mm should not pass into their joint. The required density of the joint is achieved by scraping the belts: first by paint, and then by gloss.
When reserving regulated steam extractions or counterpressure of heating turbines, automatic switching on is especially necessary in cases where, according to the requirements of the production technology, interruptions in the supply of steam are not allowed.
Turbines without controlled steam extraction are marked with an asterisk. The parameter values enclosed in brackets are not recommended for newly designed turbines.
