JPH0363641B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a steam turbine operation monitoring device,
In particular, the present invention relates to an operation monitoring device that can appropriately relax restrictions on the operating range provided to prevent damage to low-pressure final stage rotor blades.

[Descriptive background of the invention and its problems]

In recent years, steam turbines have been required to expand their operating load range and condenser pressure range. In other words, in line with the base load operation of nuclear power generation in domestic thermal power generation models, the power adjustment function has been expanded even in the latest large-capacity models, and the minimum load is lowered to, for example, 15% or less. Further, in a turbine having a cooling tower type condenser in which the condenser pressure varies greatly depending on the atmospheric temperature, the condenser pressure may be specified in the range of 5 to 50 KPa.

However, when expanding the operating range in this way, the low-pressure final stage rotor blades, which are easily affected by operating conditions, are used in a state far away from the design point, especially under low loads or high condenser pressures. During operation, the excitation force that the blades receive from the fluid increases, increasing the vibration level of the rotor blades. Therefore, it is necessary to limit the operating range of the turbine and protect the rotor blades from damage due to vibration.

In other words, when the load is reduced or the condenser pressure is increased, the volumetric flow rate passing through the final stage decreases, and as the volumetric flow rate decreases, the static pressure difference between the inlet and outlet disappears at the root of the rotor blade, causing a reverse flow. Become. Therefore, when the flow rate is further reduced, as shown in FIG. 7, the reverse region grows in the blade height direction, and the flow is biased radially outward. This results in massive countercurrent vortices and extreme radial outward flow.
Due to this backflow, the rotor blades receive a large excitation force over a wide frequency band.

By the way, in order to confirm the vibration resistance strength of the final stage rotor blade, vibration stress measurements have been carried out during operation in model turbines and actual machines, and a large amount of data has been collected. Figure 8 is a diagram showing the relationship between the axial Matsuha number M _a (average axial speed ÷ sound velocity) and the vibration stress of the rotor blade, showing a typical measurement side, where the axial Matsuha number M _a is 0.2.
It becomes minimum at ~0.3, and increases at lower Matsuha numbers.

Figure 9 is a diagram showing the permissible operating range of the turbine set in consideration of rotor blade vibration at low flow rates, where the vertical axis is loading (mass flow rate per unit annular area of the final stage) and the horizontal axis is condensate water. Indicates vessel pressure. In this example, to prevent the final stage outlet temperature from rising, the condenser pressure is limited to 25KPa or less, and furthermore, to prevent vibration from increasing, the condenser pressure is limited to 17KPa or less when the load is below 30% turbine low load line L. ing.
In other words, operation is stopped on the right side of the CDEF line in the diagram, and the alarm device is activated in the area surrounded by BCDE.

FIG. 10 is a block diagram of an operation monitoring device for performing the above-mentioned operation restriction, and shows the condenser pressure P _c detected by the pressure detection device that detects the condenser pressure, and the load that detects the turbine load. The turbine load W detected by the detection device is compared with the condenser pressure limit value set in advance in the judgment device.
By comparing PE ₁ , PE ₂ (PE ₁ < PE ₂ ), and the turbine load limit value Wo, a stop signal is issued when Pc > PE ₂ , a stop signal is issued when W≦W ₀ and P _c > PE ₁ , and W >W ₀ and PE ₂ ≧P _c >PE ₁ , an alarm signal is output, and the alarm device or stop device is activated. Note that here W ₀ is an output at a certain ratio to the rated output.

However, when the limit value of the allowable operating range is set according to the output as described above, there is a problem that the limit loading of the final stage differs from unit to unit. For example, the loading at point D in Figure 9 will be smaller in a turbine with a large amount of extracted air in the intermediate stage.
Vibration stress increases. In other words, the vibration limit value would be different for each unit, which is unreasonable. Also,
According to the vibration measurement results of the rotor blade, the vibration stress at point D in FIG. 9 is larger than the vibration stress in the operating range surrounded by triangle DEF. Therefore, there is a problem in that allowing operation at point D and not allowing the range surrounded by DEF only unnecessarily narrows the operating range of the turbine.

[Purpose of the invention]

In view of these points, the present invention maximizes the operating range of the turbine and minimizes the turbine stop area to the necessary minimum, especially for operation under low load and high condenser pressure. The purpose of the present invention is to obtain a steam turbine operation monitoring device that can perform the following functions.

[Summary of the invention]

The present invention has a database of detection signals from a pressure detection device that detects the exhaust pressure of a steam turbine and a flow rate detection device that detects the condenser flow rate, a turbine output signal, a final stage exhaust annular area, a part of a steam table, etc. an arithmetic device that receives data signals from the storage device and calculates an axial Matsuha number based on these input signals and a signal corresponding to the temperature of the final stage of the steam turbine; The calculated axial Matsuha number and the exhaust pressure detected by the pressure detection device are input, and the axial Matsuha number and exhaust pressure are set to the preset axial Matsuha number and exhaust pressure limit value. The present invention is characterized in that it includes a comparison and determination device that outputs a stop signal or an alarm signal by comparing each of them.

[Embodiments of the invention]

FIG. 3 is a schematic system diagram of a steam turbine device, in which a final stage temperature detection device 11 for detecting the final stage temperature TL is arranged in the steam passage section of the final stage of the turbine 10, and a final stage rotor blade in the axial direction of the turbine. An exhaust pressure detection device 12 for detecting the exhaust pressure PX is installed at the same position and in a substantially horizontal plane, and a condensate detector 12 for detecting the condensate flow rate FC is installed at the outlet of the condenser 13 and upstream of the condensate pump 14. A flow meter 15 is provided. The final stage temperature detection device 11 includes a fourth
As shown in the figure, a detector 19 is protruded from the inner wall surface of the nozzle diaphragm outer ring 18 on the exit side of the final stage nozzle 17 disposed upstream of the final stage rotor blade 16 to guide the detection signal to the outside. There is. That is, since the final stage outlet is cooled with spray water during low load, the temperature at the rotor blade outlet is not appropriate, and it is preferable to detect the nozzle outlet temperature.

By the way, FIG. 1 is a block diagram showing one embodiment of the operation monitoring device of the present invention, and FIGS.
C is a diagram showing an operation flowchart of the device, in which the final stage temperature TLi (i=1 to 4) detected by the final stage temperature detection device 11, the exhaust pressure PX detected by the exhaust pressure detection device 12, and the condensate flow rate detected by the condensate flow rate detection device 15
Each FC signal is input to the arithmetic device 20, respectively.

On the other hand, the arithmetic unit 20 has, as a database, the final stage exhaust annular area S, a part of the steam table,
and the final stage temperature calculated in advance for each operating condition of the turbine unit and the flow rate G _d (e.g. drain amount,
A storage device 21 in which the amount of seal steam, etc.) is stored.
is connected.

Therefore, the following calculation is performed in the above-mentioned calculation device.

That is, the final stage temperature TLi (i=1 to 4)
The final stage average temperature is calculated based on the above, and the humidity X calculated in advance and stored in the storage device 21, the final stage average temperature TL and exhaust pressure PX, and the steam table data are used. Then, the specific volume U, specific heat ratio K, and pressure PL of steam are calculated, and the sound velocity a in the final stage is calculated as follows: a=√×
It is calculated as ×PL×U. Note that A is a constant.

In addition, the flow rate G d flowing into the condenser without passing through the final stage is stored in the storage device as a function of the condensate flow rate FC detected by the condensate flow rate detection device 15 and the turbine output _{P w} calculated in advance. Therefore, the mass flow rate G passing through the final stage is calculated as G=FC− _Gd .

Furthermore, V = mass flow rate G x (1 x X) x specific volume U
The volumetric flow rate V passing through the final stage is calculated by , and the axial Matsuha number M _a is calculated using the final stage exhaust annular area S stored in the storage device. M _a = volumetric flow rate V ÷ annular area ÷ sound velocity Calculated by a.

Further, in the arithmetic unit, the limit value M _a ' for the axial flow Matsuha number is calculated in the following procedure. That is,
Generally, in a similar steam state, the sound velocity a is a constant value, so M _a ∝V, and furthermore, when the exhaust pressure PX is constant, the loading is ∝V, so in the end, the loading is M _a ∝. Therefore, in Fig. 6, the lower limit value, that is, the limit value M _a ′ of the axial Matzha number M _a with respect to the exhaust pressure PX is the axial Matzha number at point J on the FD, and the axial Matzha number at point D is Assuming M _a0 ,
It can be approximated by M _a ′=M _a0 ×JG/KG.

On the other hand, from Figure 6, JG=DH×FG/FH, KG=DH×OG/OH Therefore, M _a ′=M _a0 ×FG/FH×OH/OG, FG=PX−PE ₁ , FH=PE ₂ −PE ₁ , OH= _PE2 ,
From OG=PX, M _a ′=M _a0 PX−PE ₁ /PE ₂ −PE ₁ ×PE ₂ /PX = M _a0 PE ₂ /PE ₂ −PE ₁ ×PX−PE ₁ /PX. Then, the two set values PE ₁ and PE ₂ (PE ₁ < PE ₂ ) related to the exhaust pressure and the set value M _a0 related to the axial flow Matsuha number are read from the storage device, and then the axial flow Matsuha number relative to the exhaust pressure PX is calculated. Limit other M _a ′
is calculated using the following formula.

M _a ′=PE ₂ /PE ₂ −PE ₁・PX−PE ₁ /PX・M _a0 In this way, the limit value M _a ′ of the axial flow Matsuha number calculated by the calculation device and detected by the exhaust pressure detection device The exhaust pressure PX thus obtained is input to the comparison/judgment device 22.

Therefore, the exhaust pressure PX is compared with two set values PE ₁ and PE ₂ regarding the exhaust pressure, and the axial Matsuha number M _a is compared with its limit value M _a '.
If PX > PE ₂ , and PX≦PE ₂ and M _a ≦
In the case of M _a ′, a stop signal is output and the stop device 23
is activated, and when PE ₂ ≧PX>PE ₁ and M _a >M _a ', an alarm signal is output and the alarm signal 24 is activated.

By the way, when applying the present invention to an existing unit etc. that is not equipped with a final stage temperature detection device, it is most appropriate to apply the above saturation temperature at exhaust pressure PX instead of the final stage temperature. In this case, the configuration of the monitoring device does not include a temperature detector as shown in FIG. 5, and the temperature is calculated by the saturation temperature with respect to the exhaust pressure PX from the steam table in the calculation device.

Therefore, as shown in Fig. 6, the alarm activation range and stop range in the operation monitoring device of the present invention are the stop range to the right of the line connecting C-D-F, and the stop range is surrounded by B, C, D, and F. The area where the alarm occurs becomes the warning area. Therefore, compared to the conventional allowable operating range,
The triangular area surrounded by DEF will be expanded as the drivable area. Moreover, since the above-mentioned point D is defined by the set point PE ₂ related to the exhaust pressure and the set value M _a0 related to the axial flow Mach number, the flow conditions at the D point are uniquely determined, and the This eliminates the possibility of different vibration limit values.

〔Effect of the invention〕

Since the present invention is configured as described above, the permissible operating range of the turbine can be expanded to the maximum,
Particularly for operations under low load and high condenser pressure, which will become important in the future, the turbine stop area can be kept to the necessary minimum, making it possible to support flexible power generation formats.

[Brief explanation of drawings]

Fig. 1 is a system block diagram of the operation monitoring device of the present invention, Figs. 2 A to C are operational flowcharts of the device of the present invention, and Figs. 3 and 4 are explanatory diagrams of the mounting position of the detection device in the device of the present invention. , FIG. 5 is a system block diagram of another embodiment of the present invention, FIG. 6 is a diagram explaining the operating tolerance range of the device of the present invention, and FIG. 7 is a diagram showing the operating range under low steam turbine load or high condenser pressure. A schematic explanatory diagram of the flow around the final stage, Fig. 8 is an explanatory diagram of the relationship between the axial flow Mach number and the vibration stress of the rotor blade, Fig. 9 is an explanatory diagram of the operating range of a general turbine unit, and Fig. 10 is an explanatory diagram of the conventional operation. FIG. 3 is a system block diagram of a monitoring device. 10...Turbine, 11...Final stage temperature detection device, 12...Exhaust pressure detection device, 13...Condenser, 14...Condensate pump, 15...Condensate flow rate detection device, 20...Arithmetic device , 21...Storage device, 2
2... Comparison/judgment device, 23... Stopping device, 24...
...Alarm device.

Claims (1)

[Claims] 1. Detection signals from a pressure detection device that detects the exhaust pressure of the steam turbine and a flow rate detection device that detects the condenser flow rate, a turbine output signal, the final stage exhaust annular area, a part of the steam table, etc. Data signals from a storage device storing a database are input, and these input signals are combined with a temperature signal from a temperature detection device that detects the temperature of the final stage of the steam turbine or a saturation temperature of steam with respect to exhaust pressure. Therefore, a calculation device that calculates the axial flow Matsusha number, and an axial flow Matsusha number calculated by the calculation device and the exhaust pressure detected by the pressure detection device are used to calculate the axial flow Matsusha number and the exhaust gas that are set in advance. A steam turbine operation monitoring device comprising: a comparison and determination device that outputs a stop signal or an alarm signal by comparing the pressure with a limit value. 2. The comparison/judgment device outputs an alarm signal when the exhaust pressure is between a first set value and a second set value larger than the first set value and the axial Matsuha number is larger than the limit value, and the steam exhaust pressure is between the second set value and the second set value. , or when the exhaust pressure is below a second setting value and the axial Matsuha number is below its limit value, the stop signal is output as described in claim 1. steam turbine operation monitoring device.