JPH0559901A - Balance piston for turbine - Google Patents

Abstract

PURPOSE:To control thrust applied to a thrust baring within a small value. CONSTITUTION:In a balance piston for a turbine, an outlet pressure of a piston 3 disposed in a rotor 2 is introduced to a low pressure portion by a balance connecting pipe 5 so as to generate reverse thrust, thus reducing thrust applied to a thrust bearing 4 of the rotor. The balance piston comprises a control valve 6 provided on the way of the balance connecting pipe 5, and a controller for controlling the control valve 6 on the basis of a temperature of the thrust bearing 4 or a position thereof in the axial direction of the rotor 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a balance piston of a turbine applied to thermal power generation and the like.

[0002]

2. Description of the Related Art FIGS. 4 and 5 are explanatory views of a balance piston of a conventional steam turbine used for thermal power generation. In the figure, a thrust bearing 4 is attached to the steam turbine in order to support the thrust generated in the rotor 2 when the steam introduced into the casing 1 passes through the moving blades 2a. However, when the output of the steam turbine increases, the rotor 2
Since the thrust force generated in the engine is too large to be supported only by the thrust bearing 4, a balance piston is provided in the rotor 2 to generate a counter thrust force in the direction opposite to the thrust force by the steam and reduce the thrust force applied to the thrust bearing 4. There is. Reference numeral 3 is its piston, 5 is a balance connecting pipe, and 4a is a radial bearing of the rotor 2. The outlet pressure of the piston 3 is connected to an intermediate stage in the vehicle interior 1 or an exhaust port via a balance connecting pipe 5. There may be a plurality of balance connecting pipes 5.

[0003]

In the conventional balance piston of the steam turbine as described above, the reaction thrust F _D generated in the piston 3 is F _D = π / 4 × (D ₁ ² −D ₂ ² ) × ( P ₁ -P ₂ ) ... Represented in (1). However, D ₁ is the outer diameter of the piston 3, D ₂ is the inner diameter, P ₁ is the inlet pressure acting on the piston 3, and P ₂ is the outlet pressure. The reaction thrust F _D generated in the piston 3 is proportional to the pressure difference between the inlet pressure P ₁ and the outlet pressure P ₂ of the piston 3,
Although it increases as the output of the steam turbine increases, the thrust F _S generated by the steam in the rotor 2 may become maximum at a certain output point of the steam turbine as shown in FIG. 5A. This is remarkable when the exhaust gas is constantly controlled to a high pressure like a back pressure turbine. In this case, the thrust F _S −F _D applied to the thrust bearing 4 largely changes from positive to negative at a certain output point of the steam turbine as shown in FIG. It is necessary to use a large one so that it can withstand a large thrust in the direction of, and the amount of lubricating oil required for the thrust bearing 4 also increases, resulting in a large bearing loss and a disadvantage in terms of steam turbine efficiency. is there.

[0004]

A balance piston for a turbine according to the present invention is intended to solve the above problems.
A balance piston of a turbine that guides the outlet pressure of a piston provided on a rotor to a low pressure portion by a balance connecting pipe to generate a reaction thrust on the piston to reduce the thrust applied to a thrust bearing of the rotor. And a means for controlling the control valve based on the temperature of the thrust bearing or the position of the rotor in the axial direction.

[0005]

That is, in the balance piston of the turbine according to the present invention, the outlet pressure of the piston provided on the rotor is guided to the low pressure portion by the balance connecting pipe to generate a reaction thrust on the piston, which is applied to the thrust bearing of the rotor. A control valve is attached to the balance connecting pipe in the balance piston of the turbine that reduces thrust, and it is controlled based on the temperature of the thrust bearing or the axial position of the rotor. The control valve is controlled based on the temperature of the bearing or the axial position of the rotor, and the thrust generated on the rotor and the reaction thrust generated on the piston are balanced, so that the thrust applied to the thrust bearing is controlled within a small value.

[0006]

1 to 3 are explanatory views of a balance piston of a steam turbine according to an embodiment of the present invention. In the figure, the balance piston of the steam turbine according to the present embodiment is that of a steam turbine used for thermal power generation, and as shown in FIG. 1, the steam introduced into the casing 1 of the steam turbine has moving blades 2a. A thrust bearing 4 is mounted to support the thrust generated in the rotor 2 when passing. However,
When the output of the steam turbine becomes large, the thrust generated in the rotor 2 becomes too large to be supported only by the thrust bearing 4. Therefore, a balance piston is provided in the rotor 2 to generate a reaction thrust in the opposite direction to the thrust generated by the steam and The thrust applied to the bearing 4 is reduced. Reference numeral 3 is its piston, 5 is a balance connecting pipe, and 4a is a radial bearing of the rotor 2.
The outlet pressure of the piston 3 is connected to an intermediate stage in the vehicle interior 1 or an exhaust port via a balance connecting pipe 5. There may be a plurality of balance connection pipes 5.

A control valve 6 is provided on the balance connecting pipe 5.
2 and the thrust bearing 4 as shown in FIG.
Based on the temperature and as shown in FIG.
The opening of the control valve 6 is monitored based on the position of the monitor switch 1
0, AND gate 11 etc.
It has been burned. That is, on both sides of the thrust bearing 4, a thermocouple 7,
8 is provided, and the temperature T of the thrust bearing 4 is₇, T₈Is total
Is being measured. Temperature T of thermocouple 7₇High
If so, the thrust F applied to the thrust bearing 4_S-F_DIs positive and this
To make it smaller, the reaction force F generated in the piston 3_DLarger
do it. On the contrary, the temperature T of the thermocouple 8₈The higher the thrust
F_S-F_DIs negative, and to reduce it, reaction force F_DTo
You can make it smaller. Temperature T in normal operation₇, T₈Is about
Within 100 ° C, but temperature T of thermocouple 7₇Is 8
If the temperature rises above 5 ° C, install it on the balance connecting pipe 5.
By opening the control valve 6 that is open, the outlet pressure of the piston 3
Power P₂Lower the pressure difference P between the piston 3 inlet and outlet₁−
P₂To increase. As a result of this
Force F_DIs also large, the thrust F applied to the thrust bearing 4_S
-F_DIs controlled small. On the contrary, the temperature T of the thermocouple 8₈
Control valve 6 is closed when the temperature exceeds 85 ° C, for example.
As a result, the outlet pressure P of the piston 3₂Go up and fixie
3 Pressure difference P between inlet and outlet₁-P₂Becomes smaller
And the reaction force F_DAlso becomes smaller, the thrust applied to the thrust bearing 4
F_S-F_DIs also controlled small. In addition, the thermocouple 7,8
Temperature T₇, T₈Is 75 ° C or less, thrust F_SWhen
Reaction force F _DIs balanced, so change the opening of control valve 6
The opening of the control valve 6 is maintained as it is.
Also, the temperature T of the thermocouples 7 and 8₇, T₈Is 75 ℃
Thrust F acting on thrust bearing 4 between 85 ° C_S-F_DIs
Not large but reaction force F_DAnd thrust F_SWhen
Reaction force F_D75 ° C <T to almost balance ₇<
Open control valve 6 slightly at 85 ℃, 75 ℃ <T₈Slightly closed at <85 ° C
To In this way thrust F_SAnd reaction force F_DAnd almost
Thrust F applied to thrust bearing 4 by balancing_S-F
_DIs controlled within a small value.

A position sensor 9 is provided at the shaft end of the rotor 2.
It is provided to measure the axial position of the rotor 2.
Growling. The position measured by this position sensor 9
If the position L of the rotor 2 is positive, the thrust applied to the thrust bearing 4
F_S-F_DIs positive, and conversely if the position L is negative, thrust F
_S-F_DIs negative. Position L is ± 0.9 in normal operation
Although the range is up to 1.0 mm, the position L is temporarily +0.5 m.
When it becomes larger than m, open the control valve 6 fully and
Stone 3 outlet pressure P₂Lower the piston 3
Thrust F_DThe thrust applied to the thrust bearing 4 by increasing
Force F_S-F_DTo be small. Conversely, if the position L is
If it becomes smaller than -0.5 mm, the control valve 6
Is fully closed, and the outlet pressure P of the piston 3₂Raise the reaction force
F_DThrust F by reducing_S-F_DIs smaller
To do so. Thrust F when position L is zero_SAnd reaction force F
_DSince it is balanced with the
To have. Also, if -0.5 mm <L <0 mm, counteract
Force F_DIs thrust F_SIs slightly larger than the control valve 6
And the reaction force F_DTo a little smaller thrust F_SAnd reaction force F
_DAlmost balance with. Also, 0 mm <L <+0.5 m
Thrust F when m_SIs the reaction force F_DA little bigger than
Therefore, the control valve 6 is opened slightly and the reaction force F is increased._DA little larger
Thrust F_SAnd reaction force F_DAlmost balance with. in this way
And thrust F_SAnd reaction force F_DBy balancing and
And thrust F applied to the thrust bearing 4_S-F _DWithin a small value
Controlled by. In addition, for example, a numerical value of 75 is used as a control standard.
℃, 85 ℃, ± 0.5mm, etc. are examples only.
It may be changed depending on the size of the force bearing 4.

As described above, in this balance piston, the balance connecting pipe 5 is provided with the control valve 6, and the opening degree of the control valve 6 is controlled by the control device to control the temperatures T ₇ , T ₈ of the thrust bearing 4 and the axial direction of the rotor 2. Is controlled based on the position L of the rotor 2. When a large thrust is generated in the rotor 2, the temperatures T ₇ and T _{8 of the} thrust bearing 4 are increased and the position L of the rotor 2 is changed to control by the control device. The opening degree of the valve 6 is controlled, the outlet pressure P ₂ of the piston 3 changes, and the reaction thrust F _D generated in the piston 3 is controlled. Therefore, although the thrust force F _S generated in the rotor 2 is the same, the reaction thrust force F _D generated in the piston 3 is controlled and the thrust force F _S and the reaction thrust force F _D are substantially balanced as shown in FIG. 3A. thrust F _S -F _D exerted on thrust bearing 4 is controlled within a small constant value regardless of the output of the steam turbine as shown in FIG. (b).

[0010]

The balance piston of the turbine according to the present invention is constructed as described above, and even if a large thrust is generated in the rotor, the thrust applied to the thrust bearing is controlled within a small value. In addition to being able to reduce the amount, the amount of lubricating oil required for the thrust bearing is also reduced, and bearing loss is also reduced, which is advantageous in terms of turbine efficiency.

[Brief description of drawings]

FIG. 1 is a sectional view of a balance piston of a steam turbine according to an embodiment of the present invention.

FIG. 2 is a block diagram thereof.

FIG. 3 is an explanatory view of its operation.

FIG. 4 (a) is a sectional view of a balance piston of a conventional steam turbine, and FIG. 4 (b) is a sectional view of essential parts.

FIG. 5 is an explanatory diagram of its operation.

[Explanation of symbols]

 1 Cabin 2 Rotor 2a Moving Blade 3 Piston 4 Thrust Bearing 4a Radial Bearing 5 Balance Connection Tube 6 Control Valve 7 Thermocouple 8 Thermocouple 9 Position Sensor 10 Monitor Switch 11 AND Gate

Claims (1)

[Claims] 1. A balance piston of a turbine for guiding an outlet pressure of a piston provided in a rotor to a low pressure portion by a balance connecting pipe to generate a reaction thrust to the piston to reduce a thrust applied to a thrust bearing of the rotor. A balance piston for a turbine, comprising: a control valve mounted on a balance connecting pipe; and means for controlling the control valve based on the temperature of the thrust bearing or the axial position of the rotor.