JPS5918526B2 - double casing turbine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a turbine casing with a structure that prevents the working fluid of the turbine from leaking into the atmosphere.

Conventional water-based Rankine cycle turbines are typically single casing turbines with horizontal split surfaces.

However, in the waste heat recovery Rankine cycle, which has been attracting attention in recent years, a low boiling point medium is used as the working medium, and it is well known that the power recovery rate can be improved by doing so.

In this way, when a turbine that uses a working medium outside of wood has a single casing with a horizontally divided surface, there is a risk of lower economic efficiency due to external leakage of the medium at the high pressure section of the divided surface, contamination of the surrounding environment, and internal leakage of the system at the low pressure section. This included various problems such as corrosion of materials within the system due to air intrusion into the system and a decrease in turbine output.

In order to solve the problems of the prior art, the present invention has the following structure.

In other words, the outer casing has no horizontal dividing plane and is cylindrical,
The outer casing has a shape such as a cone, and is provided with a shaft sealing device including a labyrinth and a mechanical seal for one end of the rotor shaft, and a bearing stand including a journal bearing and a thrust bearing, and the end (low pressure side) of the outer casing opposite to the above. Attach an exhaust casing with a shaft sealing device and a bearing pedestal for the opposite end of the rotor shaft.

An inner casing having a horizontally divided surface concentrically with the outer casing is fixed within the outer casing, and the gap between the inner casing and the outer casing is evacuated by communicating with the turbine exhaust vacuum atmosphere, and the gap between the inner casing and the outer casing is evacuated by communicating with the turbine exhaust vacuum atmosphere. Make it difficult for fluid drain to accumulate in the area.

This is the key to the double casing structure solving the above-mentioned problems of the turbine.

In a turbine with this structure, even if the uniform body leaks from the horizontal dividing surface of the internal casing, the internal casing is surrounded by a vacuum atmosphere due to the aforementioned gap, so the leaked medium will not leak further into the outside air than the external casing. do not have.

The external casing has no horizontal dividing surface and is connected to the exhaust casing at the low-pressure end by bolts.This structure is in line with the fact that horizontal dividing surfaces are generally more prone to leaks and vertical dividing surfaces are less likely to leak. .

That is, on the horizontal dividing surface (1) it is not possible to completely stop leakage on the horizontal dividing surface with a practical level of finishing.

(2) Liquid packing often lacks compatibility with the medium.

(3) Since the gasket is cut at the shaft penetration part, it is difficult to completely prevent leakage.

On the other hand, on the vertical split surface, there is no cut part and a ring-shaped gasket can be used, so it can completely prevent leakage, just like a flange gasket.

In addition, the shaft sealing devices and bearings installed on the external casing and exhaust casing can be removed from each shaft end of the rotor without removing the internal casing and rotor from the external casing. The structure is convenient for maintenance.

The shaft seal device uses a combination of a labyrinth and a mechanical seal, similar to conventional turbomachinery, to supply seal oil to the mechanical seal and prevent oil leaking from the sliding surface of the mechanical seal into the center of the turbine and the inside of the turbine. The medium flowing from the shaft through the shaft labyrinth part to the shaft end is led to a pressure balance chamber, and the mixture of oil and medium here is led to a separate separation device and separated into oil and medium. .

Therefore, the medium flowing toward the shaft end through the turbine shaft labyrinth portion does not flow out from the turbine casing penetration portion of the shaft.

The present invention will be explained in detail with reference to FIG.

The main components of the double casing turbine according to the present invention are an outer casing 1, an inner casing 2, and a rotor 3.
, exhaust casing 5, bearing stand 6゜6', journal bearing 6a, 5a', thrust shaft 7, seal box 8
Consists of etc.

The outer casing 1 has a conical shape in the figure, and does not have a casing dividing surface parallel to the turbine axis, that is, a so-called horizontal dividing surface, but consists only of a joint surface that is perpendicular to the turbine axis, so-called a vertical dividing surface with little leakage.

The outer casing 1 is provided with a steam inlet nozzle 1d, an exhaust nozzle 1e, a sealing steam extraction nozzle 1f, etc.
In the illustrated example, the exhaust nozzle 1e is also used as a turbine installation leg.

An inner casing 2 having a horizontal dividing surface is fitted into the outer casing 1, and the inner casing 2 is fitted into the outer casing at a high-pressure side fitting part 1b and a low-pressure side fitting part 1a. 1 and the outer casing 2 are positioned.

Next, the axial positioning of the outer casing 1 and the inner casing 2 is done by the vertical joint surface 1c, and since the inner casing 2 is bolted to the outer casing 1 on this plane, the inner casing can be easily positioned with respect to the outer casing. The structure is such that it can be done.

In order to introduce steam into the inner casing 2 and prevent it from leaking into the gap 2b formed between the outer casing 1 and the inner casing 2, a sleeve 1h with a flange is inserted into the steam inlet nozzle 1d. The flange portion is inserted into the flange portion of the nozzle 1d, and the other end of the sleeve is brought into close contact with the inner casing by a gasket 11, thereby allowing steam to enter the inner casing without affecting the gap portion 2b.

This structure is also used for other sealing steam extraction nozzles 1f that penetrate through the double casing.

The gap 2b between the inner and outer casings formed as described above is connected to the turbine exhaust atmosphere by the communication pipe 1g, and this turbine exhaust atmosphere is connected to a vacuum condenser (not shown), so that the gap 2b is connected to the turbine exhaust atmosphere by the communication pipe 1g. 2b becomes a vacuum atmosphere.

This makes it easier for the liquid drain in the gap to vaporize, so that even if steam leaks from the internal casing dividing surface, it will flow into the condenser through the communication pipe 1g, and even if a crack occurs in the external casing, the medium vapor will be released into the outside air. There is no risk of leakage, and it is effective in preventing loss of media and pollution of the outside air environment.

A partition plate 4 incorporating a nozzle is fitted into the inner casing 2, a table plate 3a with blades is fitted into the inner casing 2, and a rotor 3 into which labyrinth fins 3b are embedded is fitted. It is.

An exhaust casing 5 is bolted to the low-pressure end of the outer casing 1, and its radial positioning is performed by a snug-fit surface 5b, and its axial positioning is performed by an axis-perpendicular vertical surface 5a that prevents leakage. being done.

The flow path formed by the exhaust side guide 2a of the exhaust casing 5 and the internal casing 2 has a shape that smoothly converts turbine exhaust dynamic pressure energy into static pressure energy.

Seals and bearings are built into the high-pressure rotor pipe passage of the external casing 1 and the rotor passage of the exhaust casing 5.
and; The structure allows for easy maintenance and inspection without removing the inner casing 2 from the outer casing 1.

To explain in more detail, taking the shaft seal and bearing section on the high pressure side as an example, a seal box 8 is fitted into the outer casing 1 from the axial end direction of the rotor 3, and is bolted to the outer footing 1.

A circumferential groove 8a is formed between the seal box 8 and the outer casing 1, into which steam taken out from the sealing steam nozzle 1f is supplied after being appropriately pressure-regulated, and this sealing steam is supplied to the rotor 3. and the seal box 8.

Here, some of the sealing steam flows out into the aforementioned gap 2b and some flows into the pressure balance chamber 8d.

On the other hand, a mating ring 8b, which is a mechanical seal, is fitted into the rotor 3, and seal oil is supplied to the annular chamber 8c. It leaks from the sliding surface and reaches the pressure balance chamber 8d.

In the seal balance chamber 8d [. Due to the high temperature of the medium vapor, the oil is vaporized and a mixture of medium and oil is formed.

This air-fuel mixture is separately led to the outside of the turbine, where the medium and oil are separated and reused.

Also, oil leaking from the annular chamber 8c from the sliding surfaces of the seal ring 8f and mating ring 8b fixed to the seal box 8 is mixed with the lubricating oil of the journal bearing 6a + thrust bearing T, and is received by the shaft end cover 11. , from where it is guided to the outside of the turbine.

In this way, only oil flows out from the shaft end of the rotor penetrating portion of the outer casing 10, and no medium flows out.

The mating ring 8b fixed to the circumferential shaft and the sliding seal rings 8e and 8f are pressed against the mating ring 8c with a constant pressure by an axially movable bellow, so that they are not affected by the axial movement of the rotor. However, the sliding surface does not have an excessively large gap, and the seal oil in the above-mentioned portion 8c does not excessively leak out.

Furthermore, a bearing stand 6 is fitted into the seal box 8 from the turbine shaft end side and bolted to the seal box 8, and the bearing stand 6 is equipped with a journal bearing 6a and a thrust bearing 7.

In this way, the seal and bearing parts are constructed so that they can be completely disassembled and assembled from the shaft end.

Note that the low-pressure side seal and bearing section attached to the exhaust casing 5 do not have thrust bearings, and the basic structure of the other parts is the same as that of the high-pressure section.

[Brief explanation of the drawing]

FIG. 1 shows a vertical section through the axis of a double casing turbine according to the invention. 1... External casing, 2... Internal casing, 3
... Rotor, 4... Partition plate, 5... Exhaust casing, 6... Journal bearing, 7... Thrust bearing, 8... Seal box, the arrow indicates the flow direction of the working fluid.

Claims (1)

[Claims] 1. The outer casing without a horizontal dividing surface is provided with a shaft sealing device and a bearing pedestal for one end of the rotor shaft, and the vertical end of the outer casing on the low pressure side is provided with a shaft sealing device and a bearing pedestal for one end of the rotor shaft. A double casing turbine in which an exhaust casing with a shaft sealing device and a bearing pedestal is joined, and an inner casing having a horizontal dividing surface inside the outer casing is fixed concentrically to the outer casing at its end face.