JPH0278703A - Steam turbine - Google Patents

Abstract

PURPOSE:To improve the performance of a steam turbine while ensuring the stability of a turbine shaft by selecting the start point of a partial feeding nozzle on each stage such that a steam force acting on each stage is applied downward to a turbine shaft bearing. CONSTITUTION:In a turbine shaft 1 are planted a first governor stage blade 2 and second to fourth governor stage blades 3-5 on the subsequent governor stages. At the fixed side of a casing 6 for journalling the turbine shaft 1 are provided respectively first to fifth governor stage nozzles 7-10 opposed to the respective governor stage blades 2-5. Then, the position of start point 8t of the second governor stage nozzle 8 is selected at the right side as viewed from the front of the turbine shaft 1 so that a governor stage valve force F1, dead weight F2 of a rotor and the resultant force of second to fourth governor stage steam forces F3, F4, F5 are directed downward.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION Field of Industrial Application The present invention relates to a steam turbine with an improved arrangement of partial feed nozzles.

(Prior Art) In small and medium-sized steam turbines with an output of 10,000 V or less, the height of the steam passage section is generally low. In such a steam turbine, there is a boundary layer flow along the wall of the steam passage, which is generally referred to as a secondary flow.

This flow became a spiral flow due to the influence of the inner and outer walls, which was one of the causes of large losses. The proportion of this secondary loss increases as the height of the passage section decreases, resulting in a major cause of performance deterioration.

(Problem to be Solved by the Invention) In order to reduce this effect, there is a method of decreasing the diameter of the rotor and increasing the height of the separator.

However, this method reduces the rigidity of the rotor, which is likely to cause unstable vibrations in the shaft system.

A turbine that satisfies both performance and shaft system stability is
This is particularly difficult for high-speed turbines with high steam conditions and high rotational speeds.

An object of the present invention is to provide a steam turbine that improves the performance of the steam turbine and takes into consideration the stability of the turbine shaft.

[Structure of the invention]

(Means for Solving the Problems) The steam turbine of the present invention is a turbine employing a partial feed nozzle, in which the steam force acting in each stage is applied to the turbine shaft bearing at the starting point of the partial feed nozzle in each stage. It is characterized by being selected so that it hangs downward.

(Function) In the present invention, a partial feed nozzle is adopted for each speed governor stage, and the height of the blade is increased. Performance degradation can be stopped by reducing secondary losses.

(Embodiments) The present invention will be described below with reference to embodiments shown in the drawings. In FIG. 1 showing the governor stage portion of the nozzle and blades of the steam turbine of the present invention, a turbine shaft 1 includes a first governor stage vane 2, a second governor stage vane 3. A third governor stage vane 4 and a fourth governor stage vane 5 are planted.

On the fixed side of the casing 6 that supports the turbine shaft 1, there is a first speed governor nozzle 7 facing the first speed governor blade 2, and a second WR speed nozzle 8 facing the second speed governor blade 3. 3rd WA
A third i11 speed nozzle 9 is provided facing the speed blade 4, and a fourth governor nozzle 10 is provided opposite the fourth Wi speed blade 5, respectively. In addition, the speed control stage nozzle of each stage 8.9
．． A nozzle packing 11 is provided between the turbine shaft 1 and the turbine shaft 1.

Furthermore, a steam control valve 12 is provided upstream of the first speed governor nozzle 7, and a gland packing 13 is provided between it and the turbine shaft 1. The valve force of this steam control valve 12 acts on the bearing. This valve force is calculated as follows, assuming that the direction of rotation of the steam turbine is clockwise when viewed from the front of the turbine shaft 1.
The valve force of this steam control valve 12 is determined in consideration of stability.

Generally, the bearing load on the turbine shaft 1 is determined by designing the system of the turbine shaft 1 so that the resultant force of the rotor's own weight, steam force, and valve force acts downward under all operating conditions. That is, as shown in FIG. 3, the governor stage valve °force F1. Rotor dead weight F2, 2nd
．． Third. 4th governor stage steam force F,, F,,
Fs, the direction of the second governor steam force F, that is, the position of the starting point 8t of the second governor nozzle 8, is adjusted to the turbine shaft 1 as shown in FIG. 2 so that the resultant force is directed downward. Select the right side when looking from the front.

The second, third, and fourth governor stage nozzles 8, 9, and 10 control the number of stages of the partial feed nozzle, the partial feed rate, and the output of the partial feed stage for each turbine depending on the steam conditions and output. Although the magnitude of the force is different, as shown in Figure 2, the starting points of the partial feeding paragraph are 8t, 9t, and 10t.
It is possible to determine such that the load acts downward on the rotor bearing.

In FIG. 2, 2. 3rd and 4th i! The ll speed nozzles 8, 9 and 10 are each closed by a blind plate 14, and a partial feed nozzle 15 is provided in the middle thereof.

The second, third and fourth governor stage nozzles 8, 9 and l
Each of the partial feed nozzles 15 of O is normally employed in consecutive stages when the height of the steam passage section is approximately 30 m or less when all the same feed nozzles are designed.

At this time, the width of the partial inlet nozzle 15 of each stage is changed at a constant rate from the second stage to the third stage to the fourth stage, taking into account the expansion of steam. When the steam spreads and flows into the next stage, such as from the second stage to the third stage, and from the third stage to the fourth stage, the rotation of the turbine shaft 1 causes a shift in the direction of steam rotation. Therefore, as shown in FIG. The partial feed start point 10t of the fourth governor stage nozzle 10 is also shifted with respect to the rotation direction.In this way, the arrangement of the partial feed nozzle 15 of each governor stage nozzle 8, 9, 10 is adjusted to the partial feed nozzle start point 8t. .

Ot, Lot, partial feed rate, 1 partial feed application stage, rotor stability, etc. are taken into consideration for determination.

Further, FIG. 4 shows bearing load characteristics, in which the horizontal axis represents the starting point angle of the partial feed nozzle, and the vertical axis represents the resultant force of the bearing loads.

In order to keep the bearing surface pressure, which is one parameter for determining bearing stability, within a certain tolerance, the starting points are 8t, Ot, and 10t.
You can decide the position of

That is, the range is indicated by range H in FIG.

〔Effect of the invention〕

As described above, in the present invention, the stability of the turbine shaft system is ensured by determining the starting point of the partial feed nozzle so that it hangs downward on the bearing of the turbine shaft that employs the partial feed nozzle. can be made into something.

[Brief explanation of the drawing]

FIG. 1 is an assembled cross-sectional view of a turbine shaft system showing one embodiment of the steam turbine of the present invention, FIG. 2 is a schematic configuration diagram for explaining the arrangement of partial feed nozzles used in the present invention, and
The figure is a vector diagram of the load acting on the bearing according to the present invention, and FIG. 4 is a characteristic diagram showing the relationship between the bearing load and the starting point of the partial feed nozzle. 1...Turbine shaft 2...-Membrane blade 3.
4.5...Second. Third. 4th governor stage vane 6...Turbine casing 7...-Membrane nozzle 8.9.10.
...Second. Third. 4th governor stage nozzle 11...Nozzle packing 12...Steam control valve 13...Gland packing 14...Blind plate 15...Partial feed nozzle 8t, 9t, Lot...Partial feed Nozzle starting point Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A steam turbine employing a partial feed nozzle, characterized in that the starting point of the partial feed nozzle of each stage is selected such that the steam force acting in each stage is applied downward to the turbine shaft bearing.