RU2289029C2 - Device to supply cooling air to working of turbine wheel - Google Patents

Abstract

FIELD: mechanical engineering; turbines.

SUBSTANCE: proposed device to supply cooling air to working blades of turbine wheel contains air space limited by rear wall of nozzle assembly and communicating through preliminary air swirling devices with ring mixing chamber formed by ring base of rear wall of nozzle assembly, inner ring aligned with said wall and bottom and communicating with space at working blades. Preliminary swirling devices are made in from of through holes in ring base of rear wall of nozzle assembly. Entry of through holes through ring base of rear wall of nozzle assembly into mixing chamber is arranged at bottom of said mixing chamber.

EFFECT: improved efficiency of cooling of thermally and dynamically stressed of turbine wheel, increased strength of units and parts in field of centrifugal and thermal loads.

4 cl, 5 dwg

Description

The technical solution relates to gas turbine power, in particular to devices for supplying cooling air to the turbine blades.

A device for supplying cooling air to the turbine blades of the turbine is known (see descriptions for patents - analogues, priority 17/12/1977 by Rolls Royce United Kingdom - No. 2010404, MKI F 01 D 5/18, USA - No. 4275990, NCI 416-95, claimed 30 11.1978, France - No. 2411959, MKI F 01 D 5/18).

The device has an air cavity, which is limited by the walls of the box-shaped shell of the stator and the blade web. The cavity is communicated through nozzles that perform the function of pre-swirling cooling air (see the term in GOST 23851-79), and an annular groove in the rim of the disk with cooling channels for the working blades.

Such a device allows to reduce energy costs when supplying cooling air due to its direction in the direction of rotation of the turbine rotor.

In this solution, air has contact with a sufficiently high surface temperature of the impeller disk. This reduces the cooling efficiency of the blades. The description indicates that pressure losses are reduced to a minimum, however, a 90-degree rotation of the flow, on the contrary, creates resistance and increases pressure losses.

Also known is an air-cooled turbine for a gas turbine engine (see descriptions for patents - analogues, priority 07/07/1982 from Rolls Royce - USA - No. 4348157, NKI 416-95, France - No. 2439872, MKI F 01 D 7/18). The turbine sequentially contains a nozzle apparatus and an impeller with blades. Under the nozzle apparatus, an air supply cavity is formed due to the compressor from under the combustion chamber.

The inner rings 18 and 20 with sealing labyrinths form an annular cavity under the nozzle apparatus, in communication with the annular cavity at the locks of the working blades. Above and below the locks, two concentric groups of axial annular grooves are formed, closed by the impeller annular collars introduced into them, and together as seals limit the cavity of the blade locks.

This cavity is in communication with the through cavity of mixing under the rim of the blades of the nozzle apparatus, bounded by the said rings 18 and 20 under the nozzle apparatus. The latter are combined into the internal base of the nozzle apparatus by blades 19, which operate as a means of preliminary swirling of cooling air passing through the through cavity for mixing this base under the nozzle apparatus.

Behind the uprights there remains the free part of this through annular base cavity, communicated with the cavity limited by the seals, and through it with the turbine wheel deflector.

In the deflector, by the number of working blades, tube tubes bent in the direction of rotation are formed. They discretely direct cooling air to the working blades of the locks and their legs.

Such a deflector with tubes complicates the design of the turbine wheel. The known device probably quite effectively performs the function of cooling. In it, the air supplied to the locks of the blades is fenced from the blade web and less heated. However, the design of the device is very complex and involves a wide range of parts. The cutouts in the disk at each blade cause strength problems of the wheel, sufficiently loaded both thermally and dynamically, and therefore, its reliability is reduced.

Due to the features described above, it is practically impossible to use the well-known technical solutions considered in small-sized highly loaded gas turbine engines.

From the description of US patent No. 3791758 (stated on 05/01/1972 Secretary of State for Defense of the UK, US C1 416/116, IPC F 01 D 5/08), a device for supplying cooling air to the working blades of a turbine wheel is known.

The known device comprises an air cavity 20 surrounded by a nozzle apparatus 24 in front of a wall 20A (line 49, description column 2) of the nozzle apparatus and an annular mixing chamber 50 behind said wall 20A. Thus, the mixing chamber 50 is separated from the air cavity 20.

Means for preliminary swirling of air between the specified chamber 50 and the cavity 20 is made in the form of a scapular apparatus 42.

The annular mixing chamber 50 is formed by the inner and outer annular protrusions of the nozzle apparatus.

Moreover, these nozzles of the blade apparatus 42, as a means of swirling, through the mixing chamber 50 and the diffuser cavity 39 are in communication with the channels 48 under the locks 30 of each working blade 27.

The known device also cannot be used in small turbines due to the impossibility of performing a "miniature" blade apparatus for preliminary swirling and directing air to the working blades in the form of a continuous swirling shroud.

Despite these shortcomings, the device according to US patent No. 3791758 was selected as a prototype of the claimed device in terms of the generality of the problem being solved, the proximity of the technical nature and the possibility of its further improvement to obtain a more progressive technical result.

The authors were faced with the task of creating a device for supplying cooling air to the working blades of the turbine, the purpose of which would be directed specifically to small-sized, highly loaded gas turbine engines.

In this case, in comparison with the prototype, it was necessary to obtain an aggregate technical result, consisting of several interrelated and causally progressive technical results, namely:

- improving the cooling efficiency of both the rotor blades and the impeller disk in its most loaded part at the attachment point of the locks of the blades of especially high-loaded turbines of small engines;

- providing (avoiding discreteness of the cooling air jets) a continuous swirling air sheet directed at a particularly thermally and dynamically stressed zone of the turbine wheel;

- simplification of the design of small turbines while improving the manufacturability of their production;

- reduction of the range of necessary parts;

- increasing the strength of components and parts located in the field of centrifugal and thermal loads.

This problem is solved in that in the known device for supplying cooling air to the working blades of the turbine wheel, containing an air cavity bounded by the rear wall of the nozzle apparatus, communicated by means of preliminary air swirling with an annular mixing chamber formed in the said rear wall of the nozzle apparatus by the outer and inner rings and the bottom and communicated with the cavity at the working blades, an improvement is made.

The improvement lies in the fact that these means of pre-twisting made in the form of through holes through the outer ring of the specified mixing chamber.

The inner ring bounding the mixing chamber is removable.

In a section along the longitudinal axis of each of the holes, the latter at their entrance into the mixing chamber are oriented in the circumferential direction to the troughs of the working blades of the turbine wheel.

The entrance of these through holes through the outer ring inside the specified mixing chamber is placed at its bottom.

Moreover, these holes in the section along the longitudinal axis of each are placed uniformly around the circumference, both separate holes and separate groups.

This makes it possible, when passing the length of the mixing chamber instead of many separate discrete, albeit swirling, jets of air from the openings, to obtain a swirling uniform veil of air at the outlet of the mixing chamber, flowing to the bases (locks) and, if necessary, to the cooling channels of the working blades.

If these holes are placed evenly around the circumference in groups of several holes, their diameters can be increased, while observing the requirement that the amount of cooling air passing through them be 1 ... 2% of the amount of air consumed by the engine as a whole.

This arrangement of the guide holes is more technologically advanced than the uniform circular arrangement of the holes of a smaller diameter.

In both cases, cooling is ensured and its efficiency is increased. Compared with the prototype, the design of the device is simplified.

In a particular design, an annular mixing chamber may be formed between the rear wall of the nozzle apparatus and an additional ring aligned with the rear wall. This design is more technological in production.

All of this together provides the above technical results of the proposed solution.

The essence of the proposed technical solution is illustrated by drawings, where:

- Figure 1 is a longitudinal section of a turbine of a gas turbine engine with a supply of cooling air through a nozzle apparatus;

- Figure 2 shows an enlarged fragment A (see figure 1) of a device for supplying cooling air to the working blades of a turbine of a gas turbine engine;

- Figure 3 shows enlarged sections (see figure 1) BB along the axes of the through holes and BB through the working blades of the turbine, with their relative position;

- Figure 4 shows a longitudinal section of a turbine of a gas turbine engine with a supply of cooling air from under an annular once-through combustion chamber;

- Figure 5 is a longitudinal section of a turbine of a gas turbine engine with a supply of cooling air from under a countercurrent combustion chamber.

Presented in FIG. 1, the design of the inventive device for supplying cooling air to the working blades of a turbine wheel comprises a stator housing 1 with openings 2 for supplying air. Hollow blades 3 of the turbine nozzle apparatus are installed in the stator housing 1, further, nozzle blades 3 are placed around the air cavity 4 of the receiver. Behind them is a turbine wheel with rotor blades 6 fixed in its disk 5 with troughs 7.

The nozzle blades 3 have internal shelves, combined in an annular inner bandage 8, protruding along the longitudinal axis (relative to the flow) to the working blades 6 in the disk 5 of the turbine wheel.

Toward and concentrically inside the specified annular inner bandage 8 of the nozzle blades 3, in the direction of the longitudinal axis of the turbine are the internal shelves of the working blades 6 of the disk 5 of the turbine wheel. They form an annular bandage 9 with a common annular protrusion 10, directed (conditionally) against the flow.

The inner bandage 8 of the nozzle blades 3 forms an air cavity 4 of the receiver together with an annular, U-shaped in longitudinal section, the inner casing 11, a concentric bandage 8 and placed radially inside the latter.

The U-shaped inner casing 11 has annular, front 12 and rear 13, inner walls directed radially from the longitudinal axis of the turbine. In each of the walls of the front 12 and rear 13, annular grooves are made radially outward from the longitudinal axis: the front groove 14 and the rear groove 15.

A front ring 16 is inserted into the front groove 14 and is composed of a plurality of radial protrusions of the brace 8 of the nozzle vanes 3.

A rear ring 17 is introduced into the rear groove 15, which is composed of a plurality of rear radial protrusions of the same brace 8 of nozzle blades 3.

The rear wall 13 of the U-shaped housing 11, bounding the air cavity 4 of the receiver, contains an outer annular axial collar 18, directed under the annular protrusion 10 of the blades 6 and placed concentrically to the latter.

The annular inner bandage 8 of the nozzle blades 3, the axial collar 18 and the counter protrusion 10 located between them together form a kind of mechanical seal at the boundary with the gas-dynamic path of the turbine.

The rear wall 13 under the axial shoulder 18 has an annular base 19 concentrically developed for the latter in the axial direction.

While the specified annular base 19 is placed concentrically around the annular protrusion 20 of the disk 5 of the turbine wheel.

In the annular base 19 is formed along the longitudinal axis in the form of an annular gap mixing chamber 21, calculated by known methods. The latter is open only in the direction of the turbine wheel. At the same time, this mixing chamber 21 is in communication with the air cavity 4 of the receiver through the outer wall of the slot through holes 22 with their entrance into the specified mixing chamber 21 within the volume of the latter.

At the same time, these through holes 22 in cross section along the longitudinal axis of each at their entrance into the mixing chamber 21 are oriented in the circumferential direction on the trough 7 of the turbine blades 6.

As a more technologically advanced solution of the device, the mixing chamber 21 can be formed by a slotted annular space, closed from the air cavity 4 of the receiver, between the annular base 19 and the ring 23, additionally installed from the inside of this annular base 19.

On the ring 23 can be made radial pointed shoulder 24, directed to the annular protrusion 20 with the formation of the design gap 25.

Thus, the cavity 26 is arranged under the protrusion 10 of the bandage 9 of the internal shelves of the working blades 6. The cavity 26 is communicated through the mixing chamber 21 with the air cavity 4 of the receiver by a plurality of said through holes 22 in the base 19. The cavity 26 is connected through the gap 25 with the cavity 27 under the U-shaped inner case 11.

Due to the fact that these through holes 22 at their entrance into the mixing chamber 21 are oriented in section along the longitudinal axis of each in the circumferential direction on the trough 7 of the working blades of the turbine wheel, they provide a preliminary air swirl.

In the mixing chamber 21, the air jets are combined, mixed into a common annular uniform air flow running onto the working blades 6 and cooling, in particular, their locks.

The inventive device can be performed and providing the air cavity 4 of the receiver with cooling air from under the shell of the combustion chamber.

We turn to the design of the inventive device for a gas turbine engine with a once-through combustion chamber (see Figure 4).

In this case, the air cavity 29 under the inner shell 30 of the direct-flow combustion chamber is in communication with the air cavity 4 under the nozzle blades 3, which is also in communication with the cavity 26 of the working blades 6 through the preliminary swirling through holes 22 in the annular base 19 and the mixing chamber 21.

At the same time, the annular base 19 with its front wall 28 is jointed simultaneously with the inner bandage 8 of the nozzle blades 3 and the inner shell 30 of the direct-flow combustion chamber.

In the case of the inventive device for a gas turbine engine with a countercurrent combustion chamber (see Figure 5), the air cavity 31 is limited to the shell 33 of the counterflow combustion chamber.

This air cavity 31 is in communication with the air cavity 4 under the nozzle blades 3, which is also communicated with the cavity 26 of the working blades 6 through the described preliminary twist holes 22 in the annular base 19 and then through the mixing chamber 21, which is connected to the cavity 26 in front of the workers blades 6, in particular at their locking parts.

In this case, the annular base 19 with its front wall 32 is jointed simultaneously with the annular inner bandage 8 of the nozzle blades 3 and the shell 33 of the combustion chamber (Figure 5).

Moreover, in any of the described device designs, the entrance into the mixing chamber 21 of the holes 22 is preferably located at the bottom 34 of the specified chamber.

The supply of cooling air to the working blades 6 of the turbine in any of the structures of the claimed device is implemented as follows.

Turn to figure 1. Cooling air is taken off due to the compressor or due to intermediate stages of the compressor and is supplied by known means into the air cavity 4 of the receiver. The pressure in the air cavity of the receiver 4 significantly exceeds the pressure in the cavity of the mixing chamber 21.

Cooling air from the air cavity 4 of the receiver enters the mixing chamber 21 at its bottom 34 through the air guide through holes 22.

In this case, air jets in the section along the longitudinal axis of each hole 22 are formed in the circumferential direction on the trough 7 of the working blades 6.

Discrete jets of cooling air from the holes 22, passing from the bottom 34 of the mixing chamber 21 through its cavity to the outlet, are closed in a continuous annular air curtain, which is then sent to cool the blades 6, in particular, to the place of installation of their locks in the disk 5.

If the inventive device is made, as in Fig. 4 or 5, providing the cavity 4 with cooling air from under the shell of the combustion chamber, the principle of supplying cooling air to the chamber 4 and passing it through the openings 22 and further from the mixing chamber 21 into the cavity 26 is completely identical to the above .

The principle of operation and efficiency of the device are the same in the case of air intake from the cavity 31 under the shell 33 countercurrent combustion chamber.

In this case, the flow of medium from adjacent cavities into the cavity 26 for supplying cooling air is limited:

- from the side of the gas-dynamic path of the turbine — a system of cylindrical scallops, including in total an annular protrusion 8, an axial shoulder 18 and a counter protrusion 10 located between them;

- from the side of the cavity 27 - radial shoulder 24 and the protrusion of the disk 20, also forming a kind of seal.

The cooling efficiency σ of the proposed device is higher than the efficiency of a system with discrete jets.

In this case, the air temperature at the inlet to the working blade 6 is significantly reduced, which is confirmed by the well-known gas-dynamic calculation:

where T ^* _w - air temperature at the entrance to the working blade

T ^* - full temperature of cooling air

u ₁ - peripheral speed of the rotor at the radius of the supply

with _u - circumferential component of the velocity of the supplied air

c _p - heat capacity of air

r is the recovery coefficient

σ is the efficiency of the supply system.

The fact that the twisting holes are placed at their entrance to the mixing chamber at its bottom most effectively ensures the conversion of individual jets into an air curtain. This ensures the supply of cooling air to the working blade in the form of a continuous jet swirling in the same direction as the troughs of the working blades, i.e. rotor rotation.

Elimination of discreteness of leakage of cooling air allows to reduce its temperature at the inlet to the working blade by 20-30 ° C. This ultimately improves the reliability of not only the turbine, but also the reliability and efficiency of the engine as a whole.

The consumption of cooling air is not more than 1 ... 2% of the total consumed by the engine.

The applicability of the proposed technical solution is confirmed by the positive test results of prototypes of aircraft engines TV3-117 VMA-SBM1, D-27, AI-450, developed by the GP "ZMKB Progress" named after A. G. Ivchenko.

Claims (4)

1. A device for supplying cooling air to the working blades of a turbine wheel, comprising an air cavity bounded by the rear wall of the nozzle apparatus and communicated by means of preliminary air swirling with an annular mixing chamber formed by the annular base of the rear wall of the nozzle apparatus, an inner ring aligned with said wall, and the bottom and communicated with the cavity of the working blades, characterized in that the means of pre-twisting made in the form of through holes in the annular base of the rear wall and nozzle apparatus. 2. The device according to claim 1, characterized in that the entrance of the through holes through the annular base of the rear wall of the nozzle apparatus into the mixing chamber is located at the bottom of the specified mixing chamber. 3. The device according to any one of claims 1 and 2, characterized in that said holes in the radial plane are evenly spaced around the circumference. 4. The device according to any one of claims 1 and 2, characterized in that said holes in the radial plane are arranged uniformly around the circumference in separate groups.

Images