JPH01203601A - Expansion turbine - Google Patents

Abstract

PURPOSE:To prevent over-speed of a turbine, by connection of a pipe system for introducing higher pressure gas than the pressure in the inside circulating passage, into the circulating path passage of a brake fan. CONSTITUTION:A connection of an introducing pipe 11 for introducing higher pressure gas than the pressure of an inside circulating passage 9, into the circulating passage 9 of a brake fan 6 is provided in said circulating passage 9. When absorptive power of the brake fan 6 is small, a part of high pressure gas 14 is introduced into the circulating passage 9 through a pressure adjusting valve 10. Thereby, absorptive power of the brake fan 6 is increased so as to prevent over-speed of a turbine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an expansion turbine and relates to a structure suitable for increasing the absorption power of a brake fan by 5%.

[Conventional technology]

In conventional expansion turbines, Turbomachinery Vol. 11 No. 7 (1
983), pages 37 to 42, the brake fan of the dual expansion turbine had one closed circulation path.

[Problem to be solved by the invention]

In the above conventional technology, the pressure in the brake fan circulation path is determined by the pressure in the bearing chamber (nozzle outlet pressure), and the structure is such that it cannot handle even if the pressure in the brake fan circulation path is lower than the design value.

There was a problem that the design absorption power could not be satisfied.

An object of the present invention is to easily increase the pressure in the circulation path of a V-fan when the pressure in the circulation path is lower than the design value to satisfy the designed absorption power.

[Failure to solve the problem]

The above object is achieved by forcibly supplying gas at a high pressure from the outside to the circulation path of the turbine fan.

The expansion turbine of the present invention is an expansion turbine in which a main shaft having a turbine blade provided at one end and a brake fan attached to the other end is supported by a journal bearing and a thrust bearing.
The brake fan has a structure in which a piping system is provided in the circulation path of the brake fan so that gas having a pressure higher than that in the circulation path can be introduced from the outside, and the gas can be discharged from the inside of the expansion turbine to the outside. Features.

Examples of embodiments of the present invention are listed below.

(1) A part of the high pressure gas discharged from the compressor is introduced into the circulation path of the brake fan of the expansion turbine.

The expansion turbine has a structure in which gas discharged from the inside of the expansion turbine to the outside returns to the suction side of the compressor.

(2) Branching from the bearing gas supply piping for supplying static pressure gas to the thrust bearing, it is possible to supply gas at a higher pressure into the brake V-fan circulation path of the expansion turbine than in the brake fan circulation path. Having a structure.

(3) In an expansion turbine having a bearing gas outlet pipe that supplies bearing gas to the thrust bearing and discharges it from the inside of the expansion turbine to the outside, the gas in the brake fan circulation path is discharged from the bearing gas outlet pipe.

(4) Having a pressure drop resistor in the artificial part where the gas from the circulation loop of the brake fan enters inside the bearing chamber of the expansion turbine.

[Effect]

To increase the absorption power of the brake fan.

The brake fan circulation path construction 9 also forcibly introduces high pressure gas into the circulation path from the outside, making the pressure in the brake fan circulation path higher than the pressure in the bearing chamber by the differential pressure generated between the brake fan and the bearing chamber. do. Therefore, the power absorbed by the brake fan increases in proportion to the increase in pressure.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure shows, for example, a system diagram of an expansion turbine used in a helium liquefaction refrigerator.

A turbine rotor 3 is attached to the lower end of the shaft that rotates at high speed, and a brake fan 6 is provided to the upper end. 5 is a journal bearing that supports the shaft in the radial direction, and a hydrostatic gas bearing is used to support the shaft in the thrust direction (axial direction).

To explain the gas flow, high-pressure helium gas 1 at the turbine inlet is accelerated by a nozzle 2 and ejected. Next, this ejected gas transmits power to the turbine rotor 3, expands adiabatically, lowers its temperature and pressure, and becomes turbine outlet gas 4, which is guided to other components (for example, a heat exchanger).

On the other hand, a part of the gas from the nozzle outlet passes through the bearing chamber where the journal bearing 5 is located and fills the brake fan circulation path 9 of the brake fan 6 to maintain pressure equilibrium. The brake fan 6 rotates at high speed to compress helium gas and circulate it in the circulation path 9, forming a closed cycle. Further, the compression heat generated at this time is removed from the system by an external heat exchanger (not shown).

Therefore, the power generated by the turbine rotor 3 is absorbed by the power generated by the brake fan 6 to compress helium gas, and the rotational speed is kept constant. Therefore, if the absorption power of the V-key 7 is smaller than the design value, the rotational speed of the turbine becomes overspeed, which disturbs the stable rotation of the turbine.

Alternatively, there was a problem of bearing seizure. In this embodiment, high-pressure gas (for example, led from the high-pressure side of a compressor) 14 for constructing the thrust bearing passes through a static pressure gas pipe 12, passes through a flow rate control valve 13, and passes through a thrust collar 1.
Gas is ejected from the nozzle holes on both sides of the 5 to achieve levitation in the thrust direction. after that.

It passes through the discharge port 16, passes through the pressure regulating valve 18, and is recovered to the low pressure side (for example, the compressor return side).

Further, a part of the high pressure gas 14 passes through the introduction pipe 11, passes through the pressure regulating valve 10, enters the brake circulation path 9 having the brake valve 8, increases the pressure in the circulation path 9, and creates a pressure difference in the labyrinth 7, for example. It passes through the bearing chamber and joins the static pressure gas outlet 16.

Therefore, when the absorbed power of the brake fan is small, by appropriately adjusting the pressure regulating valve 10, V and V are reduced.
- The pressure in the circulation path 9 can be raised above the balance pressure.

Assuming that the work performed by the brake fan is the absorbed power P1, the following equation holds.

Here, λ: power coefficient (characteristic value of the brake fan) r Ni-brake fan suction side gas density u2 Circumferential speed at the Ni-brake fan outer diameter d2 Ni-Brake fan outer diameter b2 Blade height at the Ni-Brake fan outer diameter Therefore If the gas pressure in the circulation path of the brake fan is increased, the gas density also increases, and the absorbed power can be increased as shown by equation (1).

Therefore, according to this embodiment, the structure is simple.

The power absorbed by the brake fan can be increased.

This has the effect of providing a turbine that does not cause overspeed and has excellent stability over one rotation.

In addition, the high-pressure gas at room temperature introduced into the brake circulation path is discharged from the thrust bearing to the outside of the turbine, so it does not enter the low-temperature side of the turbine.

Furthermore, since a labyrinth is provided between the brake fan and the bearing chamber, a pressure difference occurs here, and the pressure in the bearing chamber hardly increases. This prevents room-temperature gas from the bearing chamber from entering the low-temperature side of the turbine.

Turbine efficiency does not decrease. In addition, since the absorption power can be greatly controlled, the pre-cooling stage of the helium refrigerator (
It also has the effect of increasing the turbine flow rate from the cooling stage) and shortening the cool-down time.

FIG. 2 shows an example of a structural diagram of an expansion turbine using a hydrodynamic thrust bearing. Components with the same reference numerals as those in FIG. 1 represent the same components, and therefore their explanation will be omitted. 1
Reference numeral 9 denotes, for example, a V-step type dynamic pressure type gas bearing. The gas introduced from the high-pressure gas supply hole 20 enters the circulation path of the brake fan 6, increases the pressure of the gas in the path, creates a pressure difference in the labyrinth 7, and enters the bearing chamber housing the journal bearing 5. , and is recovered to the low pressure side through the discharge port 16. Therefore, according to this embodiment, the first
As explained in the figure, even in an expansion turbine using a hydrodynamic gas bearing as a thrust bearing, the absorption power of the brake fan can be easily increased.

FIG. 3 shows an embodiment of an expansion turbine using a labyrinth having another structure. The method of increasing the absorption power of the brake fan is the same as in the above embodiment.

A 21 radial labyrinth may be used if the radial vibrations of the shaft are relatively large. In a radial flow labyrinth, the gas flow is inward.

This is advantageous for the seal because the centrifugal force acting on the gas acts in a direction that opposes the leakage flow. Therefore, the radial flow labyrinth used in this example was used.

This has the effect of increasing the absorption power of the brake fan by forcibly introducing high-pressure gas from the outside into the brake fan circulation path.

〔Effect of the invention〕

According to the present invention, the absorption power of the brake fan can be easily increased without increasing the outer diameter of the brake fan, and since the turbine does not overspeed, stable high-speed rotation can be performed. It is effective and has the effect of increasing reliability.

[Brief explanation of the drawing]

Fig. 1 is a convenient system diagram of an expansion turbine showing the principle of the present invention, Fig. 2 is a sectional view of an expansion turbine showing one embodiment of the invention, and Fig. 3 shows another embodiment of the invention. FIG. 2 is a structural diagram of the expansion turbine shown in FIG. 3... Turbine rotor, 5... Journal bearing, 6
...Brake fan, 7...Labyrinth, 11...
・Introduction tube. 15... Thrust collar, 16... Discharge port. 4t-～-'＼ 1 Figure R 3-...Target 50-ta hand 2 2o°-°pressure kaka・shugi machine f G

Claims (1)

[Claims] 1. In an expansion turbine in which a main shaft with a turbine blade attached to one end and a brake fan attached to the other end is supported by a journal bearing and a thrust bearing, there is a pressure in the circulation path of the brake fan that is higher than the pressure in the circulation path. An expansion turbine characterized in that it has a piping system that can introduce high pressure gas from the outside, and has a structure that can discharge gas from inside the expansion turbine to the outside.