JPS5979005A - Axial-flow turbine having widthwise-flow type speed governing step attached with variable nozzle - Google Patents

Abstract

PURPOSE:To reduce the valve pressure loss in the inlet port of the titled turbine and to facilitate the mounting of the variable nozzle by a method wherein the widthwise-flow step is provided on the turbine inlet side of a rotor having the axial-flow step and the variable nozzle is provided in the widthwise-flow step. CONSTITUTION:The rotor 11 is formed of the widthwise-flow step 12 on the side of the steam inlet port and the axial-flow step 13 having blades 14 embedded therein. Further, the variable nozzle 16 is provided on the side of the inlet port of the widthwise-flow step 12 so that the opening degree of the nozzle 16 is adjusted and the quantity of steam corresponding to the opening degree of the nozzle is flowed in. Thus, since no valve used, the valve pressure loss can be reduced. Moreover, due to the provision of the widthwise-flow step in the turbine inlet port, it is possible to mount the variable nozzle easily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an axial flow turbine, and provides an axial flow turbine having a radial flow governor stage with a variable nozzle.

2. Description of the Related Art Steam turbines, gas turbines, and gas expanders that are widely used for power generation and motive power generally adopt a multistage axial flow type because the operating conditions include large pressure ratios and large flow rates.

In addition, steam flow control by nozzle shutoff is adopted for load control of these axial flow turbines, and a plug-type valve as shown in Fig. 1 is used for this nozzle shutoff. In order to improve this, a multi-verbal system is generally used.

In FIG. 1, 1 is a plug-type control valve, 2 is a nozzle, 3 is a rotor, 4 is a nozzle chamber, 5 is a nozzle chamber partition plate, 6 is a lift rod, and 7 is a steam inlet.

However, in such a multi-valve nozzle shutoff control system, the valve pressure loss cannot be ignored, and the valve pressure loss decreases the turbine first stage nozzle inlet pressure, reducing the effective heat drop in the turbine. It means to do. this is,
This has a big effect when the valve starts to open, especially when the number of valves is small. Figures 2 and 3 show the relationship between the valve opening and the valve pressure loss and the relationship between the valve opening and the effective heat drop when the number of valves is four, respectively. It shows a relationship.

On the other hand, in recent years, there has been a growing trend toward energy conservation, and a large number of waste heat recovery power generation facilities are being planned and operated.However, since the heat source side (exhaust heat amount) of such power generation facilities cannot be controlled, turbine control is difficult. Adopts inlet pressure control instead of load control. The load on the turbine is determined by the amount of exhaust heat, and the turbine is often operated at a low load during periods of low operating efficiency or when the amount of exhaust heat changes daily depending on the process, and the turbine is operated at a point where valve pressure loss is large. Since such exhaust heat recovery turbines have a relatively small output, they are often high-speed turbines in consideration of cost reduction, and therefore, due to their high speed, the number of stages is relatively small, so they are particularly sensitive to the effects of valve pressure drop. The important point is to improve performance at low loads and to make it easy to accept.

The present invention was made in view of the above circumstances, and aims to improve efficiency and save energy during low-load operation and turbine inlet pressure control operation of a multistage axial flow turbine by reducing valve pressure loss at the turbine inlet. shall be.

The present invention adopts a multi-stage axial flow turbine inlet flow rate control acupuncture nozzle system, and also uses this variable nozzle. In order to make it easier to install, a special feature is the adoption of a radial type (radial type) as the type of governor stage.

An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 4 shows an example of the basic structure of an axial flow turbine according to the present invention, in which the rotor 11 is an impeller (stream stage) on the steam inlet side.
12 and several stages of disks (axial stages) 13 in which blades 14 are installed.

Thus, the steam enters the spiral nozzle chamber 15 after passing through the main stop valve. After that, the steam is transferred to the variable nozzle 1
6 and flows into the impeller 12 from a direction perpendicular to the turbine axis, and at the impeller outlet flows in the direction of the turbine axis, passes through the nozzle 17 and the blade 14, and reaches the exhaust port 18.

Note that the structure other than the impeller 12 and variable nozzle 16 is almost the same as that of a conventional axial flow turbine.

FIG. 5 shows the basic mechanism of the variable nozzle. This mechanism is
Conventionally, the variable nozzle 16 has been used in many radial flow turbines (impeller 12 in FIG. 4), and the variable nozzle 16 is attached to a rotating ring 22 via a connecting rod 21. By rotating this rotating ring 22 left and right, the variable nozzle 16 rotates left and right around the point at which the connecting rod is attached, adjusting the opening degree of the nozzle 16 and keeping the steam pressure in front of the nozzle constant. The amount of steam flows in according to the nozzle opening degree. The rotation of the rotating ring 22 is caused by the movement of the servo oil cylinder 23 via the interlocking lever 24. This is done by being transmitted via the lift rod 25.

FIG. 6 shows a comparative example of the partial load characteristics of a fixed nozzle using a conventional valve control method and a variable nozzle according to the present invention. This example is a comparison with a fixed nozzle using a single valve, so there is no difference in performance (at 50% flow rate, the output is about half the difference).

As described above, the present invention provides a radial flow stage on the turbine inlet side of a rotor having an axial flow stage, and this radial flow stage is provided with a variable nozzle for controlling the inlet flow rate. Effects can be obtained.

(1) Since there is no valve pressure loss, partial load performance is improved.

(21) Since a radial flow stage with different steam flow diameters is used at the turbine inlet, the number of stages is reduced compared to a full stage axial flow type in order to absorb a large amount of heat drop due to the large inlet diameter. be able to.

(3) In steam conditions where the heat drop and pressure ratio are relatively small, such as in a back-pressure turbine, a multiple-stage radial flow turbine was possible; When this happened, the radial flow turbine also became multi-stage, making the structure complex and difficult to adopt.

However, by combining the radial flow type and the axial flow type as in the present invention, it is possible to bring out the advantages of both, improve partial load characteristics, and create a turbine with a high thermal drop.

As described above, according to the present invention, there is provided an axial flow turbine having a variable nozzle-equipped radial flow regulating stage which is extremely useful industrially.

[Brief Description of the Drawings] Fig. 1 is a diagram showing a multi-valve nozzle shut-off control system in a conventional axial flow turbine, and Fig. 2 is a diagram showing the relationship between valve opening degree and valve pressure loss in this nozzle shut-off control system. 3 is a diagram similarly showing the relationship between the valve opening degree and the effective heat drop, FIG. 4 is a diagram showing an example of the basic structure of the axial flow turbine according to the present invention, and FIG.
The figure shows the basic mechanism of the variable nozzle, taken in the direction of arrow A in FIG. 4, and FIG. 6 is a diagram showing a comparison of the partial load characteristics of the variable nozzle according to the present invention and a conventional fixed nozzle. 11. Rotor, 12. Impeller, 13. Fist disk, 14. Φ blade, 16. Variable nozzle No. 1 Fig. 2 Fig. 39 Valve opening degree Blue leap Fig. 4 Fig. 5 Sea bream

Claims (1)

[Claims] An axial flow turbine characterized in that a radial flow stage is provided on the turbine inlet side of a rotor having an axial flow stage, and a variable nozzle for controlling the inlet flow rate is provided in the radial flow stage.