JPS6153407A - Speed governing system change over device - Google Patents

Abstract

PURPOSE:To control erosion and thermal stress by obtaining a change over device, capable of automatically performing throttling speed governing at starting time and shifting to nozzle cut-out speed governing without fear of generating load change and further performing nozzle cut-out speed governing even in medium and low load area. CONSTITUTION:At starting time of a steam engine, each speed governing change-over instrument 4a-4d is changed over to combined function operation instruments 2a-2d side and, after converting a flow signal from an output control operation instrument 1 into an opening requirement signal of combined governing by each operation instrument 2a-2d, said signal is inputted to steam adjusting valve opening/closing controllers 5a-5d. In case load is raised and a flow signal from the output control operation instrument 1 grows above correspondence with high load area and this condition is detected by a change-over command instrument 6, speed governing instruments 4a-4d are changed over to nozzle function operation instruments 3a-3d side by said change-over command instrument 6 at the time of inputting a change-over command signal. Nozzle cut- out speed governing operation is performed hereafter.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a speed governor for a steam turbine, and in particular, to a method for smoothly and automatically switching the speed governing system between startup and load operation. This invention relates to a speed control system switching device created to obtain the following results.

[Background of the invention]

The speed control of a steam turbine is performed when starting the turbine,
When the load fluctuates after completion of startup, the steam control valve installed in the turbine inlet steam pipe is controlled to open and close, and this speed control includes (1) nozzle shutoff control, (li) throttle control. (
iii) There is a method similar to 3a with combined speed control.

FIG. 2 is an explanatory chart of the above-mentioned nozzle shut-off speed regulation, and illustrates the case where four steam control valves (not shown) are provided.

When starting a turbine and increasing its load from 0% to 100%, first curve one steam control valve ■!
It opens as shown, and then fully opens at around 1/4 load (25%). Around this time, another steam control valve started to open at around 1/4 load, and as shown in the curve, 1/2 load (5
Fully open around 0%). Around this time, one more steam control valve begins to open, and fully opens at around <3/4jl load (75%) as shown in curve 3. Around this time, the last (4)
Start opening the steam control valve (1) and bring it close to fully open at full load.

When the load decreases, the above operation is performed reversibly, and the steam control valves are throttled down and closed one by one.

In this nozzle shut-off speed regulating system, each steam control valve is open or closed at times other than full load and no load, and as a result steam only flows to a portion of the turbine nozzle. Since the turbine flows, the temperature between the various parts of the turbine becomes uneven, resulting in large thermal stress.

The aforementioned throttling speed control is suitable for reducing the temperature difference between each part of the turbine.

FIG. 3 is an explanatory diagram of the above-mentioned throttle #) speed control, and the imaginary line shows the curve in the nozzle closing speed control described above for comparison. In throttle control, all steam control valves are gradually opened in the same manner as in the curve VALL from a no-load state to a full load state. (This diagram represents the curve Vall with four parallel lines, but in reality these four
The curves of the book overlap. In the steam control system, all steam control valves are half-open except at full load or no load, resulting in large energy loss and low efficiency at partial loads.

Which of the two speed control methods (nozzle shut-off speed control or throttle speed control) to select should be determined mainly depending on the frequency of startup and shutdown of the steam turbine plant, and the state of load fluctuations. If the frequency of stoppages is severe, throttle control with gentle thermal stress conditions is suitable, and if there are many partial loads, nozzle shut-off speed control is suitable, but in actual cases the selection is complex and depends on various conditions. I'll come.

Another technical problem other than the above is nozzle erosion.

This erosion is mainly caused by flying objects such as scale from the steam generator side such as a boiler, and these flying objects are most often seen when restarting after a shutdown, and almost never after that.

Therefore, there is a need to improve thermal efficiency by using throttling speed control only when restarting after a shutdown, and switching to the nozzle control speed control system when there are no more flying objects such as scale, regardless of the operating load at that time. Ta.

In order to meet these demands, the above-mentioned combined speed governor has been proposed (Japanese Patent Publication No. 7123/1983).

FIG. 4 is an explanatory diagram of the combined speed control. Depending on the magnitude of the turbine load, a low load area, a medium load area, and a high load area are set as shown in the figure. In this example, a load of less than 20 inches is defined as a low load region, and a load of 50 inches or more is defined as a high load region, but the boundaries of these load regions can be set arbitrarily.

Four curves Vl', V(, Vl - Vl'd,
This shows the opening and closing of the steam control valve.

In the low load region, the four steam control valves are uniformly and gradually opened in the same manner as the curve Vall in the above-mentioned throttle control.

In the medium load region, the two steam control valves are set to curve y,
The steam control valves are gradually opened as shown in curves ', v,' until they are fully open, and the other two steam control valves are gradually closed as shown in curves v3' and y4/.

In the high load region, curves ■1' and ■2' are fully opened υ, curve ■3' is fully opened between 1/2 load and 3/4 load 1, and curve v4' is 3/4 From 4 load to full load, it approaches the fully open state.

When the load is reduced, the above-described operation is followed reversibly.

In the above-mentioned combined speed control (Fig. 4), in low load areas where thermal stress and erosion are a major problem, the speed is controlled by throttle #), and in high load areas where efficiency is important, nozzle closing speed is controlled. Therefore, these problems are rationally solved, making it an extremely excellent speed regulating system.

However, regarding the above combined speed control system,
However, there is room for improvement, such as the lack of staff.

In this combined speed control system, the program is fixed such as throttling speed control in the low load area and nozzle closing speed control in the high load area, so for example 3
There was a problem in that nozzle closing speed regulation was impossible at 0% load, and similarly, throttling speed regulation was impossible at 70% load.

Throttle speed control and nozzle closing speed control have inherent advantages and disadvantages given by their respective valve opening characteristics. Since all valves are opened at the same time in throttle control, steam is distributed evenly throughout the valve, and erosion of the turbine nozzle, etc., progresses evenly. However, since the valve is opened gradually, energy loss is inevitable during throttling, resulting in low efficiency at partial loads. On the other hand, in the nozzle shut-off speed regulating system, each valve is fully opened first, so one valve is fully opened immediately and there is no loss due to throttling, resulting in good efficiency. However, since the steam flows only into one part of the turbine nozzle, only that nozzle receives two lotions, and the heat load is large, so there is a problem that the material deteriorates early. Furthermore, most of the erosion of the nozzle is caused by scale etc. that fly from the steam generator when the steam generator that supplies steam to the turbine is stopped and then restarted. The example shown in No. 46-7123 uses throttle control in the low load range and nozzle shutoff control in the high load range, so at startup, steam flows through all valves and is evenly distributed to each nozzle, preventing erosion. Evenly, one part will not be subject to excessive erosion. However, even in a steady state, there is a problem that the efficiency is not good because the throttle is controlled by p in the low load operating range.

It is also possible to prepare both a nozzle closing speed regulation program and an aperture speed regulating program and switch to any one of these programs in any state (at any time). There is a risk of shocking load fluctuations occurring when switching programs.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and it automatically performs throttling speed control at startup, shifts to nozzle cut-off speed control without the risk of load fluctuations, and operates in the medium to low load range. Another object of the present invention is to provide a speed regulating switching device capable of controlling the nozzle closing and speed.

[Summary of the invention]

In order to achieve the above object, the switching device of the present invention includes a computing unit for controlling the output of a steam turbine, a plurality of steam control valves for regulating the turbine inlet steam flow rate, and a switching device provided by the above-mentioned output control computing unit. A steam turbine equipped with a function calculator that converts a flow rate signal into an opening request signal for a steam control valve, and a valve opening/closing controller that controls the opening of a seven-steam control valve according to an output signal of the function calculator. In the control device, the above-mentioned function calculator (a) performs throttling speed regulation in a low load region, performs nozzle closing speed regulation in a high load region, and transitionally controls the speed regulating method of the above 28M class in an intermediate load region. (b) A function calculator equipped with a combined speed control function that switches between speeds, and (b) a function calculator equipped with a nozzle shutoff speed control function in the full load range, and when the load of the steam turbine is The present invention as described above is characterized in that a speed governor switching device is provided which has a function of selectively switching the output signals of both of the functional calculators and inputting the signals to the valve opening/closing controller in a state of a high load region. The following is a further summary of the outline.

Comparing the nozzle shut-off speed control shown in FIG. 2 with the combined speed control shown in FIG. 4, the curves in both charts are equivalent in the region of 50% load or more. Therefore, from the 50-chi load to the 100% load, there is no risk of load fluctuations even if the nozzle shut-off speed regulation and combined speed regulation are mutually switched. The present invention is constructed focusing on this principle.

FIG. 2 shows one embodiment of the switching device of the present invention.

In this example, the output control calculator 1 controls the total flow rate of the steam control valve.
, a combined function calculator 2a to 2d (one attached to each valve), which outputs a steam control valve opening request signal during combined governor/g based on the flow rate signal from the output controller 1; an output control calculator 1; Nozzle function calculators 3a to 3a which output a steam control valve opening request signal at the time of nozzle shut-off and speed regulation based on the flow rate signal from
3d (one for each valve), and speed control switchers 43 to 4d for switching between combined gapping and nozzle closing speed control.

It is composed of steam control valve opening/closing controllers 5a to 5d that adjust the opening degree according to the opening request signal of each steam control valve, and a switching command device 6 that performs switching of the speed regulating method according to the switching command signal. .

The operation of the switching device (FIG. 1) of this embodiment constructed as described above will now be described.

At startup, the speed governor switching devices 4a to 4d are switched to the combined function calculators 2a to 2d, and the flow rate signal from the output control calculator 1 is transferred to the combined function calculators 2a to 2d.
2d, the signal is converted into a combined gas opening request signal and inputted to the steam control valve opening/closing controllers 53 to 5d to adjust the opening degree of each steam control valve. When the load increases and the flow rate signal from the output control calculator 1 becomes equal to or higher than the above-mentioned high load region, the switching command unit 6 detects this and becomes ready for switching. When a switching command signal is input to the switching command device 6 in this state, the switching command device 6 switches the speed regulators 43 to 4d to the nozzle function calculators 32 to 3d, and from then on, nozzle closing speed regulation is performed. becomes. According to this example,
At startup, throttling control is performed, which prevents only one part of the nozzle from being eroded.Since switching occurs when the opening characteristics are the same, no load fluctuations occur due to switching, and after switching, even at low loads. Highly efficient operation is possible.

〔Effect of the invention〕

As detailed above, according to the switching device of the present invention, the throttle υ is automatically adjusted at startup to reduce damage caused by two lotions, reduce thermal stress, and eliminate the risk of load fluctuations. This has an excellent practical effect in that the nozzle shut-off adjustment is quickly shifted, and then the nozzle shut-off speed is adjusted even in the medium to low load range, thereby reducing energy loss caused by the steam control valve.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing one embodiment of the present invention, Fig. 2 is an explanatory chart of nozzle cut-off speed regulation, Fig. 3 is an explanatory chart of cut-off speed regulation,
FIG. 4 is an explanatory chart of combined speed control.

Claims (1)

[Claims] 1. A computing unit that controls the output of the steam turbine, a plurality of steam control valves that adjust the steam flow rate at the turbine inlet, and converting the flow rate signal given from the output control computing unit into an opening request signal for the steam regulation valve. In the steam turbine control device, the function calculator includes: (a) a function calculator that controls the opening of a steam control valve according to an output signal of the function calculator; A functional calculator equipped with a combined speed control function that performs throttle speed control in the load range, performs nozzle closing speed control in the high load range, and transitionally switches between the above two types of speed control methods in the intermediate load range;
(b) Both function calculators are provided with a function calculator having a nozzle shutoff speed regulating function over all load ranges, and both of the function calculators are installed in a state where the load of the steam turbine is in a high load range. What is claimed is: 1. A speed governing system switching device for a steam turbine, comprising a speed governing switch having a function of selectively switching the output signal of the output signal and inputting the signal to a valve opening/closing controller.