CN107784156B - Method for calculating parameters of steam discharge system of nuclear power plant - Google Patents

Method for calculating parameters of steam discharge system of nuclear power plant Download PDF

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CN107784156B
CN107784156B CN201710800214.0A CN201710800214A CN107784156B CN 107784156 B CN107784156 B CN 107784156B CN 201710800214 A CN201710800214 A CN 201710800214A CN 107784156 B CN107784156 B CN 107784156B
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steam
temperature
calculating
current moment
heat transfer
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CN107784156A (en
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刘现星
罗小雨
孙海军
程堃
张靖
刘磊
王珺
唐征明
李广围
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719th Research Institute of CSIC
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    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
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Abstract

The invention relates to a method for calculating parameters of a steam discharge system of a nuclear power plant, which comprises the following steps: initializing; calculating steam flow, a pressure reducing device coefficient, an opening degree of a discharge valve and pipeline pressure drop; calculating the steam flow, the water supply flow, the circulation rate, the average heat exchange coefficient, the reactor power, the average temperature of the main coolant, the recirculation water flow and the circulation water flow at the current moment; calculating to obtain the steam temperature at the current moment; acquiring saturated steam pressure at the current moment; acquiring an enthalpy value of outlet water of a heat transfer area at the current moment n; calculating the temperature of the steam-water separation region at the current moment; calculating the temperature of a descending area at the current moment; acquiring an enthalpy value of an inlet of a heat transfer area at the current moment; calculating the heat exchange coefficient of the primary side of the steam generator at the current moment; calculating the temperature of the reactor outlet coolant at the current moment; repeatedly performing steps S2 to S17; upper limits for reactor outlet coolant temperature and vapor pressure are determined. The invention is simple and easy to use.

Description

Method for calculating parameters of steam discharge system of nuclear power plant
Technical Field
The invention relates to steam discharge, in particular to a calculation method of parameters of a steam discharge system of a nuclear power plant.
Background
The steam exhaust system is an important system for ensuring the safe operation of the nuclear power plant. After the load of a steam turbine is suddenly and greatly reduced, the power of the reactor cannot be changed as fast as the load of a steam turbine generator, and the steam discharge system is used for discharging steam directly to a condenser in a controlled manner in the process, so that the temperature transient state and the pressure transient state amplitude of the main coolant of the reactor of the nuclear steam supply system are reduced by providing a 'man-made' load method for the reactor, and the maximum working pressure of the steam system is limited at the same time, so that the safe operation of a nuclear power plant is ensured.
The parameters of the steam exhaust system are designed to fully take the dynamic effect of the system into consideration. The dynamic course of the operation of the steam discharge system involves the reactor, the main coolant system, the steam generator characteristics, and the corresponding control strategies and control logic, and the design of the parameters is difficult to accomplish by static analytical calculations due to the coupling effect of the nuclear power plant operation. The parameter calculation method of the steam exhaust system of the nuclear power plant comprises the following steps: the method comprises the steps of firstly preliminarily determining the discharge capacity and the pressure according to experience, then establishing a nuclear power plant simulation system, optimizing the initially designed discharge capacity and pressure through system simulation research, determining a specific discharge parameter setting value, and finally verifying through a debugging test of an actual nuclear power plant. The nuclear power plant simulation system covers reactor physics, a main coolant system, a two-loop system, an electric power system and a control system, has long development period, high difficulty and high cost, and influences iterative design of a steam discharge system and related systems, thereby influencing the overall design progress of the nuclear power plant.
Therefore, it is necessary to provide a simple and easy-to-use calculation method for calculating the steam pressure and the upper limit value of the temperature of the primary side coolant in the nuclear power plant steam exhaust system under different design exhaust loads of the steam exhaust system.
Disclosure of Invention
The invention aims to provide a simple and easy-to-use calculation method for nuclear power plant steam exhaust system parameters, which can calculate the upper limit values of steam pressure and primary side coolant temperature under different design exhaust loads of a steam exhaust system.
In order to achieve the purpose, the invention adopts the following technical scheme: a method for calculating parameters of a steam exhaust system of a nuclear power plant comprises the following steps:
s1, initialization:
s1.1, enabling n to be 1, and obtaining reactor power P at 0 moment0Average heat transfer coefficient K of steam generator0Cyclic magnification N0Outlet water flow G of secondary side heat transfer area of steam generatorof 0Outlet water enthalpy value h2f 0Outlet steam flow rate G of heat transfer areag 0Outlet steam enthalpy value h2g 0Inlet flow rate G of heat transfer zone2i 0Inlet enthalpy value h2i 0Temperature T of steam-water separation zone3 0Enthalpy value h of recirculated water3f 0Water supply flow rate Gf 0Temperature T of the falling zone1 0；
S1.2, acquiring average temperature of main coolant at 0 moment
Figure BDA0001401347720000021
The average temperature of the main coolant at the time 0 is calculated by the following formula
Figure BDA0001401347720000022
Figure BDA0001401347720000023
In the formula:
Figure BDA0001401347720000024
initial reactor power P0The corresponding main coolant system average temperature, deg.C;
△Tc-reactor coolant control dead band, deg.c;
△Tm-reactor coolant temperature measurement error, deg.c;
△Tcgiven by the control system design,. DELTA.TmThe method is given by a manufacturer for selecting a temperature measuring instrument;
s1.3, obtaining steam temperature T at 0 moments 0：
The steam pressure p at the time 0 is obtained by the following formulas 0：
ps 0＝ps0+△ps(△Tc+△Tm)
In the formula:
ps0-steam generator outlet steam pressure, Pa, at the main coolant design average temperature;
△psthe reactor power is P0When the average temperature of the main coolant is increased by 1 ℃ compared with the design value, the corresponding steam pressure increase value Pa is obtained;
looking up the steam physical property parameter table to obtain the sum ofs 0Corresponding saturated steam temperature, i.e. steam temperature T at time 0s 0；
S2, calculating the steam flow, the coefficient of the pressure reducing device, the opening of the discharge valve at the last moment and the pressure drop of a pipeline from the steam outlet to the discharge valve:
according to the design capacity and pressure of the temperature and pressure reducing device of the steam discharge system and the average temperature deviation of the main coolant, the steam flow corresponding to the target load value of the steam turbine is calculated by the following formula
Figure BDA0001401347720000031
Coefficient k of pressure reducing device1Last time n-1 opening degree k of discharge valve2 (n-1)And pressure drop of steam generator steam outlet to pipeline before discharge valve
Figure BDA0001401347720000032
Figure BDA0001401347720000033
In the formula:
Figure BDA0001401347720000034
the target load value of the steam turbine corresponds to the steam flow rate, kg/s;
P∞-a target load value, W;
G100-100% load corresponds to steam flow, kg/s;
Figure BDA0001401347720000041
in the formula:
k1-a pressure reduction device coefficient;
Gset-total design capacity of the discharge valve, kg/s;
pset-the discharge valve design inlet pressure, Pa;
Figure BDA0001401347720000042
in the formula:
k2-the discharge valve opening degree;
Figure BDA0001401347720000043
-the difference between the actual average temperature of the main coolant and the corresponding average temperature of the target load;
△T100-a design value of mean temperature deviation of the main coolant corresponding to 100% opening of the discharge valve;
△T0-a design value of mean temperature deviation of the main coolant corresponding to a discharge valve opening of 0%;
if it is not
Figure BDA0001401347720000044
Less than DeltaT0Then k is20; if it is not
Figure BDA0001401347720000045
Greater than Δ T0Then k is2＝1；
Figure BDA0001401347720000046
In the formula:
Figure BDA0001401347720000047
-the pressure drop, Pa, of the steam generator steam outlet to the line before the discharge valve;
△pf-the friction pressure drop, Pa, of the steam generator steam outlet to the front stroke of the discharge valve;
△pζ-the partial resistance member shape resistance pressure drop, Pa, before the steam outlet of the steam generator to the discharge valve;
wherein Δ pfAnd Δ pζIf the pipeline has a plurality of sections of parallel pipelines, only one working branch in the parallel pipelines is calculated;
Figure BDA0001401347720000051
Figure BDA0001401347720000052
in the formula:
△Pf,i-the friction pressure drop, Pa, of the i-th section of the pipe before the discharge valve;
△Pζ,j-the jth local resistance member shape resistance pressure drop, Pa, before the discharge valve;
lambda is the pipe friction coefficient, dimensionless;
ζ -local drag element form drag coefficient;
l-pipe length, m;
rho-fluid density, kg/m3；
Pi-circumference ratio;
d-pipe diameter, m, for local resistance, is the interface pipe diameter;
g is steam flow, kg/s;
i-tube section number;
j-local resistance number;
wherein:
Figure BDA0001401347720000053
in the formula:
Figure BDA0001401347720000061
wherein
Eta-dynamic viscosity of the fluid, kg/(m.s);
s3, calculating the steam flow at the current moment:
the steam flow rate corresponding to the target load value of the steam turbine obtained in the step S2
Figure BDA0001401347720000062
Coefficient k of pressure reducing device1And the opening k of the discharge valve at the previous time n-12 (n-1)Pressure drop of pipeline from steam outlet of steam generator to front of discharge valve
Figure BDA0001401347720000063
Calculating the steam flow at the current moment n by the following formula:
Figure BDA0001401347720000064
t is time, s;
tg-discharge valve actuation delay time, s;
Figure BDA0001401347720000065
the initial load value of the steam turbine corresponds to the steam flow rate, kg/s;
ps-steam generator outlet pressure, Pa;
t(n)＝t(n-1)+△t
wherein:
Δ t-time step, s;
s4, calculating the water supply flow:
the feed water flow is calculated by the following formula:
Figure BDA0001401347720000071
in the formula:
Figure BDA0001401347720000072
the initial load value of the steam turbine corresponds to the water supply flow rate in kg/s;
Figure BDA0001401347720000073
the target load value of the steam turbine corresponds to the water supply flow rate, kg/s;
tf-feed water flow change time, s;
Figure BDA0001401347720000074
wherein
Figure BDA0001401347720000075
-a feedwater regulating valve position corresponding to the turbine initial load;
Figure BDA0001401347720000076
-a feedwater regulating valve position corresponding to a target load of the steam turbine;
△tvp-the full travel time of the feed regulating valve, s;
s5, calculating the circulation multiplying power of the current moment:
according to the static characteristic of the steam generator, calculating the circulation multiplying power at the current moment n by the following formula:
Figure BDA0001401347720000077
wherein G isgIs the steam flow rate, f1() The static characteristic data is fitted to obtain a third order or more expression;
s6, calculating the average heat exchange coefficient at the current moment:
according to the static characteristic of the steam generator, calculating the average heat exchange coefficient of the steam generator at the current moment n by the following formula:
Figure BDA0001401347720000078
wherein G isgIs the steam flow rate, f2() The static characteristic data is fitted to obtain a third order or more expression;
s7, calculating the reactor power at the current moment:
the reactor power at the current time n is calculated by the following formula:
Figure BDA0001401347720000081
in the formula:
t is time, s;
tP-control rod action delay time, s;
P0-an initial load, W;
c1-calculating the coefficients;
Figure BDA0001401347720000082
wherein:
P100-100% load, W;
P90-90% load, W;
L100-100% load corresponds to control rod position, mm;
L90-90% load corresponds to control rod position, mm;
v-control rod normal action rate, mm/s;
s8, calculating the average temperature of the main coolant at the current moment:
reactor power P according to current time n(n)And average heat transfer coefficient K of steam generator(n)Calculating the average temperature of the main coolant at the current moment n by the following formula:
Figure BDA0001401347720000083
in the formula:
p-reactor power, W;
Δ t-time step, s;
m-mass of primary circuit coolant or structure, kg;
CPthe specific heat capacity of the primary loop coolant or structure, J/(kg. DEG C);
Figure BDA0001401347720000091
-main coolant average temperature, ° c;
Ts-saturated steam temperature, ° c;
k-average heat transfer coefficient of steam generator, W/(m)2·℃)；
A-heat transfer area of steam generator, m2；
S9, calculating the flow rate of the recirculation water and the flow rate of the circulation water at the current moment:
steam flow G according to current time ng (n)Cyclic magnification N(n)And feed water flow Gf (n)Calculating the recirculation water flow rate G at the current time n by the following formulaof (n)And heat transfer zone inlet flow rate G2i (n)：
Gof (n)＝(N(n)-1)Gg (n)
G2i (n)＝Gof (n)+Gf (n)
Wherein:
Gof-recirculation water flow, kg/s;
Gf-feed water flow, kg/s;
G2i-heat transfer zone inlet flow, kg/s;
s10, calculating to obtain the steam temperature at the current moment:
calculating to obtain the steam temperature of the current moment n through an energy balance equation of a secondary side heat transfer area of the steam generator:
Figure BDA0001401347720000092
in the formula:
m2mass of fluid or structure in the secondary heat transfer area, kg;
cp2the specific heat capacity of the fluid or structure of the secondary heat transfer area, J/(kg. DEG C);
h2i-heat transfer zone inlet enthalpy, J/kg;
h2g-the enthalpy of the steam at the outlet of the heat transfer zone, J/kg;
h2f-the outlet water enthalpy of the heat transfer zone, J/kg;
s11, acquiring saturated steam pressure at the current moment:
steam temperature T according to current time ns (n)Looking up a water and steam physical property parameter database to obtain the saturated steam pressure at the current moment;
s12, acquiring the enthalpy value of outlet water of the heat transfer area at the current moment n:
steam temperature T according to current time ns (n)Looking up a water and steam physical property parameter database to obtain the outlet water enthalpy value h of the heat transfer area at the current moment n2of (n)；
S13, calculating the temperature of the steam-water separation region at the current moment:
calculating to obtain the temperature of the steam-water separation area at the current moment n through a steam-water separation area energy balance equation:
Figure BDA0001401347720000101
in the formula:
m3mass of fluid or structure of the secondary side steam-water separation region is kg;
cp3specific heat of secondary side steam-water separation area fluid or structureJ/(kg. DEG C);
T3-the temperature of the liquid phase of the vapour-water separation zone, DEG C;
h3f-recirculating water enthalpy, J/kg;
s14, calculating the temperature of the descending area at the current moment:
the temperature T of the steam-water separation area according to the current time n3 (n)And steam pressure Ps (n)Looking up a steam physical property parameter database to obtain the enthalpy value h of the recirculated water at the current moment n3f (n)And calculating to obtain the temperature of the descending area at the current moment n through an energy balance equation of the descending area:
Figure BDA0001401347720000111
in the formula:
m1mass of fluid or structure in the secondary side descent region, kg;
cp1the specific heat capacity of the fluid or structure of the secondary side descending area, J/(kg. DEG C);
T1-the liquidus temperature of the descending zone, c;
hf-feed water enthalpy, J/kg;
s15, acquiring an enthalpy value of an inlet of a heat transfer area at the current moment:
temperature T of falling zone according to current time n1 (n)And steam pressure Ps (n)Looking up a water vapor physical property parameter database to obtain the heat transfer area inlet enthalpy value h at the current moment n2i (n)；
S16, calculating the heat exchange coefficient of the primary side of the steam generator at the current moment:
calculating the heat exchange coefficient of the primary side of the steam generator at the current time n by the following formula according to the static characteristic of the steam generator;
Figure BDA0001401347720000112
wherein G isgIs the steam flow rate, f3() To a static stateFitting the characteristic data to obtain a third order or more expression;
s17, calculating the temperature of the reactor outlet coolant at the current moment:
mean temperature T of the main coolant as a function of the current time n(n)Average heat transfer coefficient K of steam generator(n)Heat exchange coefficient alpha with primary side of steam generator1 (n)The temperature of the reactor outlet coolant at the current moment n is obtained by simultaneous calculation of the following equation set
Figure BDA0001401347720000114
Figure BDA0001401347720000113
Figure BDA0001401347720000121
Reactor outlet temperature calculation expression:
Figure BDA0001401347720000122
in the formula:
α1-heat transfer coefficient at primary side of steam generator, W/(m)2·℃)；
Figure BDA0001401347720000123
-main coolant system hot section temperature, deg.c;
Figure BDA0001401347720000124
-temperature of the cold section of the main coolant system, deg.c;
s18, repeatedly executing the step S2 to the step S17:
repeating the steps S2 to S17 until the reactor power is reduced to P +1nUntil then;
wherein:
Figure BDA0001401347720000125
s19, determining upper limit values of the temperature and the steam pressure of the reactor outlet coolant:
and obtaining a curve of the temperature and the steam pressure of the coolant changing along with time according to the calculation result, wherein the maximum values of the two curves are the upper limit values of the temperature and the steam pressure of the coolant respectively, if the upper limit values of the steam pressure and the temperature of the reactor coolant do not exceed the design allowable value, the design parameter meets the requirement, and if not, the discharge capacity is adjusted to recalculate.
The method is based on a primary side energy balance equation of a steam generator to obtain a primary side main coolant temperature expression, and the primary side main coolant average temperature at the moment is obtained through the steam temperature and the main coolant average temperature at the last moment and the reactor power at the moment; dividing the secondary side in the steam generator into three areas, namely a descending area, a heat transfer area and a separating area, establishing a first-secondary-side heat transfer equation of the steam generator and a second-secondary-side energy conservation equation set, bringing the average temperature of the main coolant into the equations, performing time discretization on the equations to obtain three linear equation sets related to the secondary-side heat transfer area, the descending area and the steam-water separating area, and performing simultaneous solution to obtain the temperatures of steam and water in the steam-water separating area, the descending area and the heat transfer area.
By adopting the invention, the maximum values of the steam pressure and the temperature of the primary side coolant under different design discharge loads of the steam discharge system can be calculated, and the maximum values are used as the basis for judging whether the parameter design of the steam discharge system can meet the safe operation of the main coolant system and the secondary loop system, and the design of the steam discharge system can also be guided. The invention is simple and easy to use.
Detailed Description
The present invention is described in further detail below with reference to specific examples, which should not be construed as limiting the invention.
The present embodiment is based on the following assumptions: the temperature negative feedback effect of the moderator and the fuel is not considered; the power is linearly related to the rod position of the control rod; taking into account control rod delay effects; the primary coolant is kept at the same temperature as the adjacent structure; calculating the average temperature of the main coolant by using lumped parameters; integrating the quantity of the steam generators into one set, wherein the integrated parameters comprise flow, fluid and structure quality and heat exchange area; after the load is changed, the water supply flow linearly changes along with the time, and the water supply flow keeps unchanged after reaching the flow corresponding to the target load; after the load is changed, the signal and action delay of the discharge valve are considered, and the steam flow linearly changes along with the time in the delay time; the steam generator cycle rate and average heat transfer coefficient are expressed as a function of steam flow at the static characteristics of the steam generator.
In the embodiment, the steam pressure is designed to be allowed to be 4.8MPa, the reactor coolant temperature is designed to be allowed to be 279.0 ℃, and the heat transfer area of the steam generator is 856.82m2Primary side total heat capacity 1.23 × 105kJ/deg.C (including coolant, pressure vessel, main pipe and primary structure of steam generator), and total heat capacity of secondary heat transfer area of steam generator is 1.01 × 104kJ/deg.C (including water, steam and secondary side structure of steam generator), total separation area heat capacity 2.67X 104kJ/deg.C, total heat capacity of 5.3X 10 in descending area3kJ/DEG C, control rod action delay time of 1s, discharge valve action delay time of 0.5s, feed water flow change time of 5s, feed water temperature of 142 ℃, feed water pressure of 4.2MPa, and auxiliary steam flow of 8.28 kg/s. The time step is selected to be 0.1s, the power of the reactor is 100MW at the initial full load operation, the steam pressure at the outlet of a steam generator is 3.9MPa at the full load operation, the steam flow and the water supply flow are both 45kg/s, and the average temperature of a coolant is 271 ℃; the target load value was 55%.
The calculation results of the main parameters at each moment are shown in table 1:
TABLE 1
Figure BDA0001401347720000141
Figure BDA0001401347720000151
Figure BDA0001401347720000161
Figure BDA0001401347720000171
In the embodiment, a small time step is selected, the calculation accuracy is high, the data size is large, and it can be seen from the table that when the design discharge load is 55%, the upper limit value of the steam pressure can reach 4.62MPa, the maximum value of the reactor coolant temperature is 274.54 ℃, and the maximum value does not exceed the design allowable value.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Details not described in the present specification belong to the prior art known to those skilled in the art.

Claims (1)

1. A method for calculating parameters of a steam exhaust system of a nuclear power plant comprises the following steps:
s1, initialization:
s1.1, enabling n to be 1, and obtaining reactor power P at 0 moment0Average heat transfer coefficient K of steam generator0Cyclic magnification N0Outlet water flow G of secondary side heat transfer area of steam generatorof 0Outlet water enthalpy value h2f 0Outlet steam flow rate G of heat transfer areag 0Outlet steam enthalpy value h2g 0Inlet flow rate G of heat transfer zone2i 0Inlet enthalpy value h2i 0Temperature T of steam-water separation zone3 0Enthalpy value h of recirculated water3f 0Water supply flow rate Gf 0Temperature T of the falling zone1 0；
S1.2, acquiring average temperature of main coolant at 0 moment
Figure FDA0002585985410000011
The average temperature of the main coolant at the time 0 is calculated by the following formula
Figure FDA0002585985410000012
Figure FDA0002585985410000013
In the formula:
Figure FDA0002585985410000014
initial reactor power P0The corresponding main coolant system average temperature, deg.C;
ΔTc-reactor coolant control dead band, deg.c;
ΔTm-reactor coolant temperature measurement error, deg.c;
ΔTcgiven by the control system design, Δ TmThe method is given by a manufacturer for selecting a temperature measuring instrument;
s1.3, obtaining steam temperature T at 0 moments 0：
The steam pressure p at the time 0 is obtained by the following formulas 0：
ps 0＝ps0+Δps(ΔTc+ΔTm)
In the formula:
ps0-steam generator outlet steam pressure, Pa, at the main coolant design average temperature;
Δpsthe reactor power is P0When the average temperature of the main coolant is increased by 1 ℃ compared with the design value, the corresponding steam pressure increase value Pa is obtained;
looking up the steam physical property parameter table to obtain the sum ofs 0Corresponding saturated steam temperature, i.e. steam temperature T at time 0s 0；
S2, calculating the steam flow, the coefficient of the pressure reducing device, the opening of the discharge valve at the last moment and the pressure drop of a pipeline from the steam outlet to the discharge valve:
according to the design capacity and pressure of the temperature and pressure reducing device of the steam discharge system and the average temperature deviation of the main coolant, the steam flow corresponding to the target load value of the steam turbine is calculated by the following formula
Figure FDA0002585985410000021
Coefficient k of pressure reducing device1Last time n-1 opening degree k of discharge valve2 (n-1)And pressure drop of steam generator steam outlet to pipeline before discharge valve
Figure FDA0002585985410000022
Figure FDA0002585985410000023
In the formula:
Figure FDA0002585985410000024
the target load value of the steam turbine corresponds to the steam flow rate, kg/s;
P∞-a target load value, W;
G100-100% load corresponds to steam flow, kg/s;
Figure FDA0002585985410000025
in the formula:
k1-a pressure reduction device coefficient;
Gset-total design capacity of the discharge valve, kg/s;
pset-the discharge valve design inlet pressure, Pa;
Figure FDA0002585985410000026
in the formula:
k2-the discharge valve opening degree;
Figure FDA0002585985410000031
-the difference between the actual average temperature of the main coolant and the corresponding average temperature of the target load;
ΔT100-a design value of mean temperature deviation of the main coolant corresponding to 100% opening of the discharge valve;
ΔT0-a design value of mean temperature deviation of the main coolant corresponding to a discharge valve opening of 0%;
if it is not
Figure FDA0002585985410000032
Less than Δ T0Then k is20; if it is not
Figure FDA0002585985410000033
Greater than Δ T0Then k is2＝1；
Figure FDA0002585985410000034
In the formula:
Figure FDA0002585985410000035
-the pressure drop, Pa, of the steam generator steam outlet to the line before the discharge valve;
Δpf-the friction pressure drop, Pa, of the steam generator steam outlet to the front stroke of the discharge valve;
Δpζ-the partial resistance member shape resistance pressure drop, Pa, before the steam outlet of the steam generator to the discharge valve;
wherein Δ pfAnd Δ pζIf the pipeline has a plurality of sections of parallel pipelines, only one working branch in the parallel pipelines is calculated;
Figure FDA0002585985410000036
Figure FDA0002585985410000037
in the formula:
ΔPf,i-the friction pressure drop, Pa, of the i-th section of the pipe before the discharge valve;
ΔPζ,j-the jth local resistance member shape resistance pressure drop, Pa, before the discharge valve;
lambda is the pipe friction coefficient, dimensionless;
ζ -local drag element form drag coefficient;
l-pipe length, m;
rho-fluid density, kg/m3；
Pi-circumference ratio;
d-pipe diameter, m, for local resistance, is the interface pipe diameter;
g is steam flow, kg/s;
i-tube section number;
j-local resistance number;
wherein:
Figure FDA0002585985410000041
in the formula:
Figure FDA0002585985410000042
wherein
Eta-dynamic viscosity of the fluid, kg/(m.s);
s3, calculating the steam flow at the current moment:
the steam flow rate corresponding to the target load value of the steam turbine obtained in the step S2
Figure FDA0002585985410000043
Pressure reducing deviceCoefficient k1And the opening k of the discharge valve at the previous time n-12 (n-1)Pressure drop of pipeline from steam outlet of steam generator to front of discharge valve
Figure FDA0002585985410000051
Calculating the steam flow at the current moment n by the following formula:
Figure FDA0002585985410000052
in the formula:
t is time, s;
tg-discharge valve actuation delay time, s;
Figure FDA0002585985410000053
the initial load value of the steam turbine corresponds to the steam flow rate, kg/s;
ps-steam generator outlet pressure, Pa;
t(n)＝t(n-1)+Δt
wherein:
Δ t-step of time, s;
s4, calculating the water supply flow:
the water supply flow at the current moment n is calculated by the following formula:
Figure FDA0002585985410000054
in the formula:
Figure FDA0002585985410000055
the initial load value of the steam turbine corresponds to the water supply flow rate in kg/s;
Figure FDA0002585985410000056
-the target load value of the turbine corresponds to the feedwater flowAmount, kg/s;
tf-feed water flow change time, s;
Figure FDA0002585985410000057
wherein
Figure FDA0002585985410000061
-a feedwater regulating valve position corresponding to the turbine initial load;
Figure FDA0002585985410000062
-a feedwater regulating valve position corresponding to a target load of the steam turbine;
Δtvp-the full travel time of the feed regulating valve, s;
s5, calculating the circulation multiplying power of the current moment:
according to the static characteristic of the steam generator, calculating the circulation multiplying power at the current moment n by the following formula:
Figure FDA0002585985410000063
wherein G isgIs the steam flow rate, f1() The static characteristic data is fitted to obtain a third order or more expression;
s6, calculating the average heat exchange coefficient at the current moment:
according to the static characteristic of the steam generator, calculating the average heat exchange coefficient of the steam generator at the current moment n by the following formula:
Figure FDA0002585985410000064
wherein G isgIs the steam flow rate, f2() The static characteristic data is fitted to obtain a third order or more expression;
s7, calculating the reactor power at the current moment:
the reactor power at the current time n is calculated by the following formula:
Figure FDA0002585985410000065
in the formula:
t is time, s;
tP-control rod action delay time, s;
P0-an initial load, W;
c1-calculating the coefficients;
Figure FDA0002585985410000071
wherein:
P100-100% load, W;
P90-90% load, W;
L100-100% load corresponds to control rod position, mm;
L90-90% load corresponds to control rod position, mm;
v-control rod normal action rate, mm/s;
s8, calculating the average temperature of the main coolant at the current moment:
reactor power P according to current time n(n)Average heat exchange coefficient K of steam generator(n)Calculating the average temperature of the main coolant at the current moment n by the following formula:
Figure FDA0002585985410000072
in the formula:
p-reactor power, W;
Δ t-step of time, s;
m-mass of primary circuit coolant or structure, kg;
CPthe specific heat capacity of the primary loop coolant or structure, J/(kg. DEG C);
Figure FDA0002585985410000073
-main coolant average temperature, ° c;
Ts-saturated steam temperature, ° c;
k-average heat transfer coefficient of steam generator, W/(m)2·℃)；
A-heat transfer area of steam generator, m2；
S9, calculating the flow rate of the recirculation water and the flow rate of the circulation water at the current moment:
steam flow G according to current time ng (n)Cyclic magnification N(n)And feed water flow Gf (n)Calculating the recirculation water flow rate G at the current time n by the following formulaof (n)And heat transfer zone inlet flow rate G2i (n)：
Gof (n)＝(N(n)-1)Gg (n)
G2i (n)＝Gof (n)+Gf (n)
Wherein:
Gof-recirculation water flow, kg/s;
Gf-feed water flow, kg/s;
G2i-heat transfer zone inlet flow, kg/s;
s10, calculating to obtain the steam temperature at the current moment:
calculating to obtain the steam temperature of the current moment n through an energy balance equation of a secondary side heat transfer area of the steam generator:
Figure FDA0002585985410000081
in the formula:
m2mass of fluid or structure in the secondary heat transfer area, kg;
cp2the specific heat capacity of the fluid or structure of the secondary heat transfer area, J/(kg. DEG C);
h2i-heat transfer zone inlet enthalpy, J/kg;
h2g-the enthalpy of the steam at the outlet of the heat transfer zone, J/kg;
h2f-the outlet water enthalpy of the heat transfer zone, J/kg;
s11, acquiring saturated steam pressure at the current moment:
steam temperature T according to current time ns (n)Looking up a water and steam physical property parameter database to obtain the saturated steam pressure at the current moment;
s12, acquiring the enthalpy value of outlet water of the heat transfer area at the current moment n:
steam temperature T according to current time ns (n)Looking up a water and steam physical property parameter database to obtain the outlet water enthalpy value h of the heat transfer area at the current moment n2f (n)；
S13, calculating the temperature of the steam-water separation region at the current moment:
calculating to obtain the temperature of the steam-water separation area at the current moment n through a steam-water separation area energy balance equation:
Figure FDA0002585985410000091
in the formula:
m3mass of fluid or structure of the secondary side steam-water separation region is kg;
cp3the specific heat capacity of the secondary side steam-water separation area fluid or structure, J/(kg DEG C);
T3-the temperature of the liquid phase of the vapour-water separation zone, DEG C;
h3f-recirculating water enthalpy, J/kg;
s14, calculating the temperature of the descending area at the current moment:
the temperature T of the steam-water separation area according to the current time n3 (n)And steam pressure Ps (n)Looking up a steam physical property parameter database to obtain the enthalpy value h of the recirculated water at the current moment n3f (n)And is calculated by the energy balance equation of the descending regionCalculating the temperature of the descending area at the current moment n:
Figure FDA0002585985410000092
in the formula:
m1mass of fluid or structure in the secondary side descent region, kg;
cp1the specific heat capacity of the fluid or structure of the secondary side descending area, J/(kg. DEG C);
T1-the liquidus temperature of the descending zone, c;
hf-feed water enthalpy, J/kg;
s15, acquiring an enthalpy value of an inlet of a heat transfer area at the current moment:
temperature T of falling zone according to current time n1 (n)And steam pressure Ps (n)Looking up a water vapor physical property parameter database to obtain the heat transfer area inlet enthalpy value h at the current moment n2i (n)；
S16, calculating the heat exchange coefficient of the primary side of the steam generator at the current moment:
calculating the heat exchange coefficient of the primary side of the steam generator at the current time n by the following formula according to the static characteristic of the steam generator;
Figure FDA0002585985410000101
wherein G isgIs the steam flow rate, f3() The static characteristic data is fitted to obtain a third order or more expression;
s17, calculating the temperature of the reactor outlet coolant at the current moment:
mean temperature of the main coolant as a function of the current time n
Figure FDA0002585985410000102
Average heat transfer coefficient K of steam generator(n)Heat exchange coefficient alpha with primary side of steam generator1 (n)The reactor outlet cooling at the current moment n is obtained by simultaneous calculation of the following equation setsTemperature of the agent
Figure FDA0002585985410000103
Figure FDA0002585985410000104
Figure FDA0002585985410000105
Reactor outlet temperature calculation expression:
Figure FDA0002585985410000106
in the formula:
α1-heat transfer coefficient at primary side of steam generator, W/(m)2·℃)；
Figure FDA0002585985410000111
-main coolant system hot section temperature, deg.c;
Figure FDA0002585985410000112
-temperature of the cold section of the main coolant system, deg.c;
s18, repeatedly executing the step S2 to the step S17:
repeating the steps S2 to S17 until the reactor power is reduced to P +1nUntil then;
wherein:
Figure FDA0002585985410000113
s19, determining upper limit values of the temperature and the steam pressure of the reactor outlet coolant:
and obtaining a curve of the temperature and the steam pressure of the coolant changing along with time according to the calculation result, wherein the maximum values of the two curves are the upper limit values of the temperature and the steam pressure of the coolant respectively, if the upper limit values of the steam pressure and the temperature of the reactor coolant do not exceed the design allowable value, the design parameter meets the requirement, and if not, the discharge capacity is adjusted to recalculate.
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