RU2701661C1 - Cooled turbine blade element - Google Patents

Abstract

FIELD: turbines or turbomachines.

SUBSTANCE: cooled turbine blade element (1) comprises cooling air channel (4) made inside blade in radial direction along inlet edge (5), connected by inlet convergent in direction of cooling air flow channels (6) through dispensing header (7) with supply channel, and outlet channels (8) with outer surface of blade (3). Inlet confuser (6) and outlet channels (8) are made tangentially relative to cooling air channel (4), which is equipped with transit pipeline (9) installed eccentrically inside it, with variable gap relative to its inner wall (10). In flow direction of air flow in cooling channel (4) there is confuser short curvilinear channel (12), on inner wall (10) of which in zone of inlet edge (5) spherical recesses (11) are made in radial direction, which is connected to input convergent channels (6), forming common channel with ratio of total cross-sectional areas at input to input (6) and output channels (8) in interval 1.4<F_{in.chan.in.sec.}/F_{out.chan.in.sec.}<1.8. Output channels (8) are cylindrical with diffuser outlet sections, length of which relative to length of output channels (8) is l_d=0.5L. In addition, geometrical parameters of location and dimensions of spherical recesses are determined.

EFFECT: invention allows to reduce thermal stresses and increase blades working life.

4 cl, 3 dwg

Description

The invention relates to gas turbine construction, and in particular to turbine blades and can be applied in aircraft engine building and power engineering.

It is known that modern aviation gas turbines can operate at temperatures reaching 1950 K. As shown in the monograph “Aircraft Engine PS-90A” / A.A. Inozemtsev, E.A. Konyaev, V.V. Medvedev, A.V. Neradko, A.E. Ryassov; under the editorship of A.A. Inozemtseva. - M .: FIZMATLIT, 2007. - 320 s, the maximum temperature stresses occur at the inlet edges and on the outer shelves of the nozzle blades and the retaining shelves of the working blades, which can lead to burnouts and their failure. Therefore, improving the cooling system of the most heated elements of turbine blades is an urgent problem.

A possible solution to this problem is the use of heat transfer intensifiers of various types, for example, tear-off spherical recesses (hereinafter referred to as spherical recesses), in which their relative depth is h / d> 0.2, where h is the maximum depth of the recess, and d is the hydraulic the diameter of the recess in the plan, the value of which is determined by the formula d = 4F / P, where F is the area of the recess in the plan, and P is its perimeter. When a heat-transfer surface flows around a heat-transfer surface with spherical recesses, self-organizing large-scale vortex structures appear in them, intensifying the heat transfer process (see the monograph “Intensification of heat transfer by spherical recesses under the influence of perturbing factors” / A. V. Schukin, A. P. Kozlov, R. S. Agachev, Y.P.

Chudnovsky; under the editorship of Acad. V.E. Alemasova. Kazan: Kazan Publishing House, state tech. University, 2003 .-- 143 s).

Known cooled blade of a gas turbine (see RF Patent No. 2388915, IPC F01D5 / 18, publ. 05/10/2010, Bull. No. 13), in which on the inner wall of the feather of the blade from the side of its convex and concave outer surfaces are made recesses in the form of spherical recesses, which, according to the authors of this patent, allows you to abandon the deflector for internal air convective cooling of the blades and significantly simplify the process of their manufacture.

However, this design of the blade does not provide for the use of heat transfer intensifiers in the form of spherical recesses on the inner wall of the blade feather in the area of the inlet edge, the most heated element of the gas turbine, where maximum temperature stresses arise that can lead to burnout and failure of the blades.

A modern way to increase the cooling efficiency of the inlet edges of turbine blades is to cyclone them.

The generalized data on cyclone cooling are known (see the monograph “Heat transfer and hydrodynamics during cyclone cooling of gas turbine blades”) / Halatov A.A., Romanov V.V., Borisov I.I., Dashevsky Yu.Ya., Severin S.D. . / Institute of Technical Thermal Physics FLAH Ukraine. - Kiev. - 2010. - 317 c), which shows a large number of schemes for cyclone cooling of the inlet edges of turbine blades. This monograph clearly shows that the cyclone process of swirling the working fluid can occur only in a hollow cylinder (see the indicated monograph in Fig. 2.1, 2.6, 2.8, 2.13, 2.23, 2.31, etc.), in which a central tornado-like whirlwind is organized upon supply into it cooling air through tangential channels made in the body of the scapula. The occurrence of a cyclone process contributes to a significant increase in peripheral speed in a radial cylindrical channel, made in the input edge of the blade, which improves the efficiency of its cooling. The results of detailed physical studies in the above monograph by A. Halatov and others clearly show that cyclone cooling can increase heat transfer in a cylindrical channel by 3 ... 4.9 times as compared with an axial non-swirling flow with a concomitant increase in hydraulic resistance by 6.2 ... 13 times.

However, the use of cyclone cooling leads to a decrease in the cold storage of cooling air drawn into the tornado vortex, which repeatedly passes in rotational motion near the cooled wall. The consequence of this is insufficient cooling of the inlet edge, as well as the outer shelves of the nozzle and retaining shelves of the turbine blades.

A known element of a cooled blade of a turbomachine, the closest in technical essence to the claimed invention and adopted as a prototype (see RF Patent No. 2479726, IPC F01D 5/18, publ. 04/20/2013, Bull. No. 11), containing a channel for cooling air, made inside the blade in the radial direction along the input edge, connected by input channels through the distributing manifold with a supply channel, and output channels with the outer surface of the blade, while the input and output channels are tangentially relative to the channel for cooling air, which is equipped with a transit pipe installed inside it with a gap relative to its inner wall. In this invention, the main novelty is the installation of a transit pipeline in the radial channel for supplying cooling air to the outer shelf of the nozzle blade or to the retaining shelf of the working blade.

However, in a known technical solution, the authors take an annular channel between the inner wall of the radial channel for cooling air, made inside the blade in the radial direction along the inlet edge, and the outer wall of the transit pipeline for a cylindrical hollow channel in which a tornado-like vortex arises, generating cyclone cooling of the turbine inlet edge blades, which allows to increase heat transfer in this zone by about 4 times.

Available publications clearly indicate that the installation of a central body (transit pipeline) in a cylindrical hollow channel transfers the flow from a vortex cyclone flow through a short curved channel with a decrease in heat transfer from a 4-fold increase to 1.3 ... 1.35 times compared with a smooth channel (see the monograph "Heat transfer and hydrodynamics near curved surfaces" / Khalatov A.A., Avramenko A.A., Shevchuk I.V. / Kiev. - Naukova Dumka, 1992. - 136 p.). The reason is the lack of conditions in the coaxial (ring) channel for the organization of the central tornado-like vortex, which contributes to a significant increase in the peripheral speed in the cyclone.

It follows that in the prototype the transit pipeline located in the cooling channel of the inlet edge of the turbine blade performs only one function: moving cooling air to other parts of the blade (outer shelves at nozzle blades or retaining shelves at turbine blades). While another function - the function of providing a 4-fold increase in heat transfer at the input edge portion, cannot be realized in the prototype design. Because in the cyclone mode, such a cooling channel cannot work. It works only in the short curved channel mode with the excess of heat transfer over a straight smooth channel no more than 1.3 ... 1.35 times.

The technical problem to which the invention is directed is to increase the efficiency of the turbine blade cooling system.

The technical result, the achievement of which the present invention is directed, is to reduce the temperature of the wall of the turbine blades and the temperature stresses in the area of their input edges, which will increase the gas temperature in front of the turbine and obtain its higher specific parameters (circumferential force on the working blades, specific power on shaft), and also increase the working life of the turbine blades.

а на внутренней стенке короткого криволинейного конфузорного канала в радиальном направлении выполнены сферические выемки, кроме того входные каналы выполнены конфузорными по направлению движения охлаждающего воздуха.The technical result is achieved in that in the element of the cooled turbine blade containing a channel for cooling air, made inside the blade in a radial direction along the inlet edge, connected by input channels through the dispensing manifold to the supply channel, and output channels to the outer surface of the blade, while the input and the output channels tangentially relative to the channel for cooling air, which is equipped with a transit pipe installed inside it with a gap relative to its inside of the front wall, it is new that the transit pipeline is eccentric relative to the channel for cooling air, and between them two short curved channels are formed in the direction of movement of the cooling air, one of them located along the inner surface of the input edge in the area between the input and output channels, made confusory, another short curved channel located between the output and input channels along the wall of the distributing manifold, made diffuser, with a ratio of total cross-sectional areas at the entrance to the input and output channels in the interval

and on the inner wall of the short curved confuser channel in the radial direction, spherical recesses are made, in addition, the input channels are made confuser in the direction of movement of the cooling air.

The output channels are cylindrical with diffuser output sections, the length of which relative to the length of the output channels is l _D = 0.5L.

Spherical grooves are staggered, with their density

Spherical recesses are made with their relative depth h / d = 0.35 ... 0.5.

The proposed invention is presented in figures 1-3 where:

FIG. 1 is a transverse section through an element of a turbine blade;

FIG. 2 is a 3D model of an element of a turbine blade in the region of the input edge;

FIG. 3 - the influence of the degree of confusion of the channel on the intensification of the average heat transfer by spherical recesses.

Where:

1 - element of the cooled turbine blades;

2 - convex external surface of the scapula;

3 - concave outer surface of the scapula;

4 - channel for cooling air;

5 - input edge of the blade;

6 - input channels;

7 - a distributing collector;

8 - output channels;

9 - transit pipeline;

10 - the inner wall of the channel for cooling air;

11 - spherical recesses;

12 - confuser short curved channel;

13 - diffuser short curved channel;

14 - the wall of the dispensing manifold in the middle of the profile

turbine blades;

h is the depth of the spherical recess;

d is the hydraulic diameter of the spherical recess in plan;

L is the length of the output channels;

l _D - the length of the diffuser output sections of the output channels;

F _{in.can.in.in.ch} - total area of input channels 6 in the input cross section;

F _{out.channel in.sec.} - the total area of the output channels 8 in the input cross section.

- направление движения основной части потока охлаждающего воздуха;

- the direction of movement of the main part of the flow of cooling air;

- направление движения меньшей части потока охлаждающего воздуха;

- the direction of movement of a smaller part of the flow of cooling air;

The blade element of the turbine 1 with convex 2 and concave 3 outer surfaces works as follows. The cooling air from the distributing manifold 7, made inside the blade (see Fig. 1 and 2) and connected to the supply channel (not shown in the drawing), enters the inlet, confuser in the tangential plane of the cross section in the direction of movement of the cooling air, channels 6 and enters the cylindrical annular channel 4 for cooling air, in which the transit pipe 9 is eccentrically placed, through which cooling air is supplied to the outer shelves of the nozzle or retaining shelves of the working turbine blades approx. As a result of the displacement of the transit pipe 9 relative to the concentric position between the inner wall 10 of the cooling air channel 4 and the outer wall of the transit pipe 9, two interconnected short curved channels are formed in the direction of the cooling air: a confuser channel 12 located along the inner surface 10 of the input edge 5 between input channels 6 and output channels 8, and a diffuser channel 13 located between the output 8 and input channels 6 along the wall 14 of the dispenser and 7.

Getting into the confuser short curvilinear channel 12, cooling air moves along the inner wall 10, on which spherical recesses 11 are made in the area of the inlet edge 5. The depth of these recesses h is selected from the condition h = (0.35 ... 0.5) d. When flowing around the recesses 11 is the intensification of heat transfer due to separation and connection of the air flow. After its attachment, a return flow forms in the region of the outlet edge of the recess, through which the air flow moves in the opposite direction to the external flow. In this case, the acceleration of the return flow after connection first increases, and then decreases. The authors of the present invention experimentally showed that under conditions of acceleration of the external flow, the return flow in the spherical recess due to relaxation becomes at first less confuser compared to the flow of the recess in a gradientless flow, and at higher values of the acceleration coefficient of the external flow - diffuser. As a result of this, as well as due to the occurrence of a return flow on the concave surface of the recess with the generation of Taylor-Gertler microvortices and microseparations, the intensity of self-organizing large-scale vortex structures, and, as a result of this, mass transfer and heat transfer in the recess significantly increase.

As our experiments showed, with the value of the external flow acceleration coefficient K equal to 5.2⋅10 ^{-6, the} heat transfer in spherical recesses increases 2.2 times as compared to the flow around them with a gradientless external flow (see the monograph “Wall-mounted heat transfer intensification for complex boundary conditions ”/ Shchukin A.V., Ilinkov A.V. - Kazan: Kazan Publishing House, State Technical University, 2014. - 252 s).

Here

where ν is the kinematic coefficient of viscosity of the flow; x is the longitudinal coordinate; W∞ is the velocity of the external flow flowing around the recesses.

From the same monograph it follows that in a gradientless flow, spherical recesses increase the heat transfer, in comparison with a smooth channel, by 1.5 ... 2.5 times. In this case, it turns out that the total increase in heat transfer for the matrix of spherical recesses with h / d = 0.35 and K = 4⋅10 ^-6 is about 4 times.

In FIG. 3 shows the change in relative average

зависимости от коэффициента ускорения внешнегоStanton

depending on the external acceleration coefficient

flow K, which characterizes the intensifying effect of the external negative pressure gradient on the heat transfer in these recesses, which is additional to the notches deposited on the surface of the channel.

- число Стентона, характеризующее среднюю теплоотдачу в сферической выемке, обтекаемой ускоряющимся внешним потоком;

число Стентона, характеризующее среднюю теплоотдачу в сферической выемке, обтекаемой безградиентным внешним потоком. На фиг. 3 светлыми значками показаны результаты исследований теплоотдачи при обтекании одиночной сферической выемки; темными значками - результаты исследований при обтекании матрицы сферических выемок.

is the Stanton number characterizing the average heat transfer in a spherical recess streamlined by an accelerating external flow;

Stanton number, which characterizes the average heat transfer in a spherical recess flowed around by a gradientless external flow. In FIG. 3 bright icons show the results of studies of heat transfer during flow around a single spherical recess; with dark icons are the results of studies when flowing around a matrix of spherical recesses.

The physical process of increasing heat transfer in the cavity of a spherical recess streamlined by an accelerating stream (negative pressure gradient) is as follows. As the acceleration of the external flow increases, a relaxation process occurs in the return flow of the spherical recess — the process of reducing the acceleration of the return flow. With more intensive acceleration of the external flow in a spherical recess, a diffuser (decelerating) return flow is organized. This process of relaxation of the flow in the return flow causes an increase in the intensity of large-scale vortex structures self-organizing in the recess — the main factor in increasing heat transfer in the spherical recess. Moreover, as mentioned above, an increase in the acceleration coefficient K of the external flow (see Fig. 3) from 0 to 4 до10 ^-6 leads to an increase in heat transfer in a hemispherical recess, and at K≈4⋅10 ^{-6 the} heat transfer doubles with its gradientless flow.

Здесь

- суммарная площадь в плане, занимаемая сферическими выемками 11 на внутренней стенке 10 конфузорного короткого криволинейного канала 12 в зоне входной кромки 5, F_гл.пов - площадь гладкой поверхности этого канала свободной от сферических выемок 11.Thus (see Fig. 1), the sequential movement of cooling air through the inlet confuser channels 6 and the confuser short curved channel 12, on the inner wall 10 of which in the region of the inlet edge 5 in the radial direction there are spherical recesses 11, leads to an increase in the total heat transfer in about the inlet edge 5 of the turbine blade on the cooling air side is about 4 times. The best option for intensifying heat transfer in the area of the input edge of the turbine blades using spherical recesses 11 is to perform them in a checkerboard pattern with a density

Here

- the total area in the plan occupied by the spherical recesses 11 on the inner wall 10 of the confuser short curved channel 12 in the area of the inlet edge 5, F _glp - the area of the smooth surface of this channel free of spherical recesses 11.

Moreover, the common smooth channel formed by the inlet confuser channels 6 and the confuser short curved channel 12 narrows in the direction of movement of the cooling air with the ratio of the total cross-sectional areas at the entrance to the inlet 6 and outlet 8 channels in the interval

Note that the confuser shape of the input channels 6 provides the restructuring of the speed profile from the standard to confuser within their length. Only in this case, the confuser short curved channel 12 will completely flow over the entire length along the confusor stream. The number of input confuser channels 6 and their main geometric parameters are determined by thermohydraulic and strength calculations.

After the confused short curved channel 12, the flow of cooling air is divided into two unequal parts. The main part of the flow (in Fig. 1 is indicated by arrows from the solid line) enters through the outlet channels 8, made cylindrical tangentially relative to the channel for cooling air 4, to the concave outer surface 3 of the blade for organizing film cooling. Moreover, in order to increase the potential energy of the cooling air stream and increase the area of coverage with a protective film formed on the outer surface of the blade, the output sections of the channels 8 are made diffuser at a distance l _d = 0.5L, where L is the length of the output channels. The number of output channels 8 and their main geometric parameters are determined by thermohydraulic and strength calculations.

A smaller (by an order of magnitude) part of the flow (indicated in Fig. 1 by an arrow from the dashed line) enters the diffuser short curved channel 13, where it slows down and mixes with cooling air leaving the inlet confuser channels 6.

As indicated in the above monograph (authors A.V. Schukin, A.V. Il'inkov), the accelerated external flow leads to an increase in the intensity of the formation of wall microvortices and microseparations in the return flow, and allows for much more powerful self-organizing large-scale vortex structures in spherical recesses compared with the case of flow around a spherical recesses with a gradientless flow. Therefore, the total heat transfer on the inner surface of the cooling channel 4 on its inner wall 10, where the spherical recesses 11 are made, in the region of the input edge 5 increases by about 2 times (the acceleration coefficient of the external flow K = 4) compared to the average heat transfer in the spherical recesses streamlined gradientless flow (acceleration coefficient of the external flow K = 0). Since spherical recesses with a relative depth h / d = 0.35 ... 0.5 in a gradientless flow increase heat transfer by 2 ... 2.5 times, the total increase in heat transfer in the recesses will be 4 ... 5 times. The resulting total intensifying effect created by spherical recesses themselves and using the superimposed external longitudinal acceleration of the flow practically coincides with the intensifying effect of cyclone cooling (an increase of 3 ... 4.9 times). It is important that the hydraulic resistance is also reduced. But the determining factor here is that the present invention allows, while maintaining the transit pipeline in the cooling channel, designed to perform the tasks, significantly (3.0 ... 3.8 times) to increase heat transfer between the portion of the inlet edge and the cooling air compared to the prototype .

Claims (4)

1. An element of a cooled turbine blade, comprising a channel for cooling air, made inside the blade in a radial direction along the inlet edge, connected by input channels through the dispensing manifold to the supply channel, and output channels to the outer surface of the blade, while the input and output channels are tangential relative to the channel for cooling air, which is equipped with a transit pipe installed inside it with a gap relative to its inner wall, characterized in that the transit the second pipeline is eccentrically installed relative to the channel for cooling air, and between them in the direction of movement of the cooling air two short curved channels are formed, one of them, located along the inner surface of the input edge in the area between the input and output channels, is made confuser, the other short curved channel located between the outlet and inlet channels along the wall of the distribution manifold, made diffuser, with the ratio of the total cross-sectional areas at the input de in the input and output channels in the range of 1.4 <F _{I. canal} / F _out . _canal <1.8, and on the inner wall of the short curved confuser channel in the radial direction, spherical recesses are made, in addition, the inlet channels are made confuser in the direction of movement of the cooling air. 2. The element of the cooled turbine blade according to claim 1, characterized in that the output channels are cylindrical with diffuser output sections, the length of which relative to the length of the output channels is l _d = 0.5L. 3. The element of the cooled turbine blades according to claim 1, characterized in that the spherical recesses are staggered, with a density of their arrangement

4. The element of the cooled turbine blade according to claim 1, characterized in that the spherical recesses are made of a tear-off type with their relative depth h / d = 0.35 ... 0.5.

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