JP2001107747A - Steam cooling gas turbine and its bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a bearing from the thermal deformation of a shaft part due to cooling steam. SOLUTION: In a steam cooling gas turbine, a steam passage 16 for penetrating the shaft part 14 of the rotor tail end part 10 in an axial direction is provided, and a bearing 12 for rotatably supporting the shaft part 14 measures a gap G between the shaft part 14 and the bearing 12, to control lubricating oil flow rate supplied to the gap G so as to make the gap G have a given value, thereby preventing the damage to the bearing 12 based on the thermal deformation of the shaft part due to cooling steam flowing in the passage 16.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a steam-cooled gas turbine and its bearing.

[0002]

2. Description of the Related Art In order to increase the efficiency of a gas turbine, the temperature of the expansion gas inlet of the combustion gas of the gas turbine has been increasing year by year, and a gas turbine having a temperature of 1500 ° C. has recently been proposed. . In order to protect the stationary blades and the moving blades of the gas turbine from such high-temperature combustion gas, a so-called steam-cooled gas turbine that cools with relatively low-temperature steam instead of conventional air cooling has been developed.

Referring to FIG. 3, there is shown a cross-sectional view perpendicular to the central axis of a rotor tail end of a steam-cooled gas turbine. FIG. 3A shows a so-called cold state in which the steam-cooled gas turbine is stopped, and FIG. 3B shows a so-called hot state in which the steam-cooled gas turbine rises to a predetermined operating temperature after startup. . In FIG. 3, the shaft portion 100 at the tail end of the rotor is a bearing 10 forming a tilting pad.
A steam passage 102 rotatably supported by 4 and for supplying steam for cooling the moving blades (hereinafter simply referred to as cooling steam) is formed along the center axis thereof.

[0004] When the steam-cooled gas turbine is started, cooling steam is supplied to the moving blades (not shown) through the steam passage 102. The shaft 1 at the tail end of the rotor
00 is heated and the shaft portion 100 thermally expands, in comparison with a conventional air-cooled gas turbine, that is, an air-cooled gas turbine cooled by a part of combustion air compressed by a compressor of the gas turbine. Significantly larger.

[0005]

The gap between the shaft portion 100 and the bearing 104 changes due to the thermal expansion of the shaft portion 100.
That is, the gap G1 in the hot state (FIG. 3B) is smaller than the gap G0 in the cold state (FIG. 3A). This is because, even in an air-cooled gas turbine, since the shaft of the gas turbine rotor rises in temperature due to the operation of the gas turbine, the gap between the shaft of the gas turbine rotor and the bearing generally has a shaft. It is determined in consideration of the thermal expansion of the part. However, as described above, in the steam-cooled gas turbine, the shaft at the tail end of the rotor thermally expands more than the general rotor shaft due to the cooling steam, so that the gap between the shaft and the bearing changes. That is, the change in the absolute value of the difference between G0 and G1 is significantly greater than in an air-cooled gas turbine. Therefore, if the gap G1 between the shaft portion 100 and the bearing 104 is selected so as to be optimal in the hot state, the gap G0 becomes too large in the cold state, so that the surface pressure acting on the bearing becomes large and the bearing is damaged. Is generated.

An object of the present invention is to solve such problems of the prior art, and to protect a bearing from thermal deformation of a shaft portion caused by cooling steam.

[0007]

According to a first aspect of the present invention, there is provided a steam-cooled gas turbine, wherein the steam-cooled gas turbine is provided with a steam passage extending axially through a shaft at a tail end portion of the rotor. A bearing for rotatably supporting the shaft portion, means for measuring a gap between the shaft portion and the bearing, and a lubricating oil flow rate supplied to the gap so that the gap has a predetermined value. And a means for controlling the temperature of the shaft, thereby preventing damage to the bearing due to thermal deformation of the shaft caused by cooling steam flowing through the steam passage.

According to the present invention, the gap between the shaft portion and the bearing is monitored, and the flow rate of the lubricating oil supplied to the gap is controlled so that the outer gap has a predetermined value. In consideration of the thermal deformation of the shaft due to the cooling steam flowing through the steam passage formed in the shaft, the inner diameter of the bearing is optimized based on the diameter of the shaft in the hot state. However, when the steam-cooled gas turbine is started from the cold state, it is possible to prevent the bearing from being damaged due to excessive surface pressure acting on the bearing.

The gap can be determined from the distance between the outer surface of the shaft and three predetermined measurement points to determine the diameter and the center of the shaft, and based on them. Also,
An oil passage may be penetrated and formed in the bearing in the radial direction, and lubricating oil may be supplied to the gap from outside the bearing via an external oil passage.

In accordance with another aspect of the present invention, there is provided a bearing for a steam-cooled gas turbine as described above.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described with reference to FIGS. The shaft portion 14 of the rotor tail end portion 10 is rotatably supported by a bearing 12 forming a tilting pad, and a steam passage 16 for supplying steam for cooling the moving blade is formed along a central axis thereof. It is formed. The bearing 12 is formed with an oil passage 12a penetrating through the bearing pad in the radial direction, so that the lubricating oil pressurized by the lubricating oil recovery and supply device 20 is supplied to the gap G from outside via the oil passage 12a. It has become. The surface of the shaft portion 14 may be subjected to a surface treatment such as chrome plating to enhance the lubricity of the bearing 12.

A sensor 30 as a means for measuring a gap G between the shaft portion 14 and the bearing 12 is provided near the outer peripheral surface of the shaft portion 14 of the rotor tail end portion 10. The lubricating oil collecting and supplying device 20 includes an oil pan 22, a hydraulic pump 24, and a lubricating oil cooler 2 that collect and store the lubricating oil supplied to the gap G.
6. Flow control device 2 as means for controlling lubricating oil flow
8 as a major component. Lubricating oil cooler 2
Reference numeral 6 includes a temperature sensor for detecting the temperature of the lubricating oil supplied to the gap G, a heat exchanger for lowering the temperature of the lubricating oil, a refrigeration cycle, and the like. The temperature of the lubricating oil to be maintained is maintained at a predetermined temperature level.

The sensor 30 can be a non-contact type distance sensor using light or ultrasonic waves. In addition, the sensor 30
Is connected to the flow control device 28 and the flow control device 2
8 obtains the value of the gap G from the distance between the sensor 30 measured by each sensor 30 and the surface of the shaft portion 14, and controls the flow rate of the lubricating oil so that the value of the gap G becomes a predetermined value. I do. Here, from the distance between the sensor 30 and the surface of the shaft portion 14 measured by the sensor 30, the gap (G) can be obtained by obtaining the center (axial center) coordinate and the diameter of the shaft portion 14. Further, a strong correlation is recognized between the center coordinate of the shaft portion 14 and the change of the diameter, and the value of the gap G can be predicted by only one of the center coordinate and the diameter of the shaft portion 14. Therefore, the flow rate of the lubricating oil may be controlled simply by one of the center coordinate and the diameter of the shaft portion 14.

The flow control device 28 can include, as main components, a flow control valve, a valve drive device, and a control device for controlling the valve drive device based on the measurement value of the sensor 30. The control device includes, for example, a digital / analog converter connected to the sensor 30 and the valve driving device, an input / output port connected to the digital / analog converter, a CUP (central processing element), a ROM, a RAM, A writing output port, and the CUP (central processing element), R
It can include a bidirectional bus for connecting the OM and the RAM. Also, as shown in FIG. 2, on the inner peripheral surface of the bearing 12,
In the oil passage 12a, a concave portion 12b surrounding an end opening to the gap G and a substantially 8-shaped concave groove 12c communicating with the concave portion 12b are formed.

Hereinafter, the operation of the present embodiment will be described step by step from the cold state in which the steam-cooled gas turbine is completely stopped, to the operation after the rated operation state, and again to the stop. When in the cold state, the shaft portion 14 of the rotor tail end portion 10 is contracted and the gap G between the shaft portion 14 and the bearing 12 is wide, as described in the description of the related art.
Therefore, the surface load applied to the bearing 12 is high, and if the rotor starts rotating in this state, the bearing 12 is damaged. Therefore, prior to the start of the steam-cooled gas turbine, the hydraulic pump 24 is started, and relatively high-pressure lubricating oil is supplied to the gap G between the shaft portion 14 and the bearing 12 via the oil passage 12a.
The shaft portion 14 floats with respect to the bearing 12 by the static pressure of the lubricating oil. At this time, since the concave portion 12b and the concave groove 12c are formed on the inner peripheral surface of the bearing 12, hydraulic pressure can be applied to the entire gap G, and the shaft portion 14 can be effectively levitated. It becomes possible.

The floating of the shaft portion 14 is detected by the sensor 30, and when the floating is confirmed, the steam-cooled gas turbine is started. After that, the steam-cooled gas turbine goes through a so-called turning state in which the turbine rotates at a low speed, and the rotation speed becomes about 700
The state shifts to a spin state up to rpm. During this time, the sensor 30 continues to monitor the distance to the shaft portion 14,
Based on this, the flow control device 28 determines that the shaft portion 14 and the bearing 1
The supply amount of the lubricating oil supplied to the gap G is controlled so that the value of the gap G between the two becomes a predetermined value. When the number of rotations of the rotor increases, the amount of lubricating oil discharged from the gap G increases. Therefore, the amount of lubricating oil supplied to the gap G gradually increases as the number of rotations increases.

When the rotation of the steam-cooled gas turbine is stabilized in the spin state, the steam-cooled gas turbine starts increasing its speed to a rated rotation speed, for example, 3000 rpm or 3600 rpm. During this time, the shaft portion 14 is affected by the floating action due to the dynamic pressure of the lubricating oil flowing through the gap G, but the flow control device 28 determines the gap between the shaft portion 14 and the bearing 12 based on the measurement value of the sensor 30. The supply amount of the lubricating oil is controlled so that G becomes a predetermined value. Since the rotation speed of the shaft portion 14 gradually increases, the amount of lubricating oil discharged from the gap G increases,
Although the supply amount of the lubricating oil required to maintain the floating amount of the shaft portion 14 increases, since the lubricating oil in the gap G also flows at a high speed, the pressure (static pressure) in the gap G decreases and the supply amount increases. The supply pressure (static pressure) of the lubricating oil required to maintain the pressure decreases. Further, although the temperature of the lubricating oil gradually increases due to the viscous resistance of the lubricating oil, the lubricating oil cooler 26 maintains the temperature of the lubricating oil supplied to the gap G at a predetermined temperature.

Even after the rotation speed of the rotor has reached the rated value, the flow control device 28 lubricates the gap G between the shaft portion 14 and the bearing 12 to a predetermined value based on the value measured by the sensor 30. Keep controlling oil supply.

When the rotation speed of the rotor gradually decreases while the steam-cooled gas turbine is stopped from rotating at the rated value, the shaft portion 14 due to the dynamic pressure of the lubricating oil flowing through the gap G
The levitation effect of is gradually reduced. The flow control device 28 detects the sensor 3
Since the supply amount of the lubricating oil is controlled based on the measured value of 0 so that the gap G between the shaft portion 14 and the bearing 12 becomes a predetermined value, the floating of the shaft portion 14 by the dynamic pressure of the lubricating oil is performed. The decrease in operation is compensated for by the lubricating oil supplied from the lubricating oil recovery and supply device 20. That is, the supply amount of the lubricating oil gradually decreases, but the supply pressure (static pressure) gradually increases. Then, when the rotor stops, the minimum flow rate of the lubricating oil required to maintain the predetermined gap G is supplied, and at this time, the lubricating oil supply pressure becomes maximum.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a steam-cooled gas turbine according to an embodiment of the present invention, which is perpendicular to a center axis of a shaft at a tail end of a rotor.

FIG. 2 is a plan view of an inner peripheral surface of a bearing.

FIG. 3 is a sectional view similar to FIG. 1 of a shaft portion at a rotor tail end according to the prior art, (a) showing a gap between the shaft portion and a bearing in a cold state, and (b) showing a gap between the shaft portion and the bearing in a cold state; The gap between the shaft and the bearing in the hot state is shown.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Rotor tail end part 12 ... Bearing 14 ... Shaft part 12a ... Oil passage 16 ... Steam passage 20 ... Lubricating oil collection and supply device 22 ... Oil pan 24 ... Hydraulic pump 26 ... Lubricating oil cooler 28 ... Flow control device 30 ... Sensor

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16C 17/03 F16C 17/03 17/22 17/22 33/10 33/10 Z (72) Inventor Hirokawa Kazunari 2-1-1, Aramachi-cho, Niihama, Takasago City, Hyogo Prefecture Mitsubishi Heavy Industries, Ltd. Takasago Works (72) Inventor Naoya Kagawa 2-1-1, Araimachi Shinhama, Takasago City, Hyogo Prefecture F-term in Takasago Works, Mitsubishi Heavy Industries, Ltd. Reference) 3J011 AA08 BA14 JA02 KA02 LA06 MA26

Claims (7)

[Claims] 1. A steam-cooled gas turbine, wherein the steam-cooled gas turbine is formed with a steam passage penetrating in an axial direction in a shaft portion at a rotor tail end, and a bearing rotatably supporting the shaft portion. Has a means for measuring a gap between the shaft portion and the bearing, and a means for controlling a flow rate of lubricating oil supplied to the gap so that the gap has a predetermined value. A steam-cooled gas turbine that prevents damage to bearings caused by thermal deformation of the shaft due to cooling steam. 2. The means for measuring the gap determines a diameter and a center of the shaft from a distance between an outer surface of the shaft and three predetermined measurement points, and based on the distance, determines the bearing. The steam-cooled gas turbine according to claim 1, wherein a gap between the shaft and the shaft is calculated. 3. The steam-cooled gas turbine according to claim 1, wherein an oil passage penetrates and is formed in the bearing in a radial direction, and lubricating oil is supplied to the gap from outside the bearing via an external oil passage. 4. An oil pan for collecting and temporarily storing lubricating oil discharged from the gap, a hydraulic pump for sucking lubricating oil from the oil pan and discharging the lubricating oil at a predetermined pressure, The lubricating oil cooler that adjusts the temperature of the lubricating oil to a predetermined temperature, and a flow control device that controls a lubricating oil flow supplied to the gap based on a value measured by the sensor. Steam-cooled gas turbine. 5. A bearing rotatably supporting a shaft at a tail end of a rotor of a steam-cooled gas turbine having a steam passage formed therethrough in an axial direction, wherein a gap between the shaft and the bearing is measured. Steam cooling that controls the flow rate of lubricating oil supplied to the gap so that the gap has a predetermined value, thereby preventing damage to the bearing due to thermal deformation of the shaft caused by cooling steam flowing through the steam passage. Gas turbine bearings. 6. A diameter and a center of the shaft portion are obtained from a distance between an outer surface of the shaft portion and three predetermined measurement points,
The bearing according to claim 5, wherein a gap between the bearing and the shaft is calculated based on the calculated values. 7. The bearing according to claim 5, wherein the bearing has an oil passage that penetrates in a radial direction.