阅读说明：本技术 一种用于涡轮叶片的凹坑逆向气膜孔结构 (A reverse air film pore structure of pit for turbine blade ) 是由 朱惠人 李鑫磊 刘存良 张丽 许卫疆 徐志鹏 于 2020-11-04 设计创作，主要内容包括：本发明公开了一种用于涡轮叶片的凹坑逆向气膜孔结构,是在逆向气膜孔出口设置鱼鳞型凹坑。鱼鳞型凹坑的横截面为抛物线型,鱼鳞型凹坑间距与气膜孔的展向间距相同,气膜孔出口位于鱼鳞型凹坑底部,且沿气膜孔板展向排列,气膜孔出口下缘与鱼鳞型凹坑底部平齐。二次流冷却气体从气膜孔流出后与主流进行掺混,逆向射流与主流碰撞后流向速度分量减小,横向速度分量增加,其逆向射流相比正向射流可以更好的贴附壁面并且具有较好的横向扩散。此外,鱼鳞型凹坑可以减小主流与二次流掺混造成的流动损失,增强二次流的横向扩散,使得气膜孔中的冷却气流在凹坑内展向扩散后再流过被冷却壁面,射流的展向覆盖能力大大提升。(The invention discloses a pit reverse air film hole structure for a turbine blade, wherein a fish scale pit is arranged at the outlet of a reverse air film hole. The cross section of the fish scale type pit is parabolic, the distance between the fish scale type pits is the same as the span-wise distance between the air film holes, the outlets of the air film holes are positioned at the bottom of the fish scale type pit and arranged along the span-wise direction of the air film hole plate, and the lower edges of the outlets of the air film holes are flush with the bottom of the fish scale type pit. The secondary flow cooling gas is mixed with the main flow after flowing out of the gas film hole, the flow direction velocity component is reduced after the reverse jet flow collides with the main flow, the transverse velocity component is increased, and the reverse jet flow is better in wall surface attachment and better in transverse diffusion compared with the forward jet flow. In addition, the fish scale type pits can reduce the flow loss caused by the mixing of the main flow and the secondary flow, and enhance the transverse diffusion of the secondary flow, so that the cooling airflow in the air film hole flows through the cooled wall surface after being spread and diffused in the pits, and the spreading and covering capacity of the jet flow is greatly improved.)

1. A pit reverse air film hole structure for a turbine blade comprises an air film hole plate, air film holes, scale-shaped pits, an inner cooling channel, pressure surface scale-shaped pit air film holes and suction surface scale-shaped pit air film holes, wherein the pressure surface of the turbine blade is provided with the pressure surface scale-shaped pit air film holes, the suction surface is provided with the suction surface scale-shaped pit air film holes, and the air film holes are communicated with the inner cooling channel;

the depth P of the fish scale type pits ranges from 0.3D_f～1D_fThe width H of the middle section of the fish scale type pit ranges from 1.5D_f～2.5D_fThe span-wise expansion angle alpha of the fish scale type pits ranges from 20 degrees to 35 degrees;

diameter D of the air film hole_fThe value range of (1) is 0.3-2 mm, and the flow direction of the air film holeThe value range of the inclination angle theta is 30-60 degrees; the space S of the fish scale type pits is the same as the span-wise space of the air film holes, and the value range is 3D_f～7D_f。

2. A pit reverse air film hole structure for turbine blades as claimed in claim 1, wherein the lower edge of the outlet of said air film hole is flush with the bottom of fish scale pit.

Technical Field

The invention relates to a cooling technology of a turbine blade of a gas turbine, in particular to a pit reverse air film hole structure for the turbine blade.

Background

With the rapid development of aircraft engines, the turbine inlet temperature is continuously increased, and the turbine inlet temperature of advanced engines reaches about 2000K, which is far beyond the heat resistance limit of turbine blade materials. Currently, film cooling technology is widely used in aircraft engines to cool turbine blades. The film cooling is a cooling technology applied to a gas turbine blade, and means that internal cooling air flows out through discrete holes or slots, a cold air film with lower temperature is formed near the surface of the blade, the wall surface is isolated from high-temperature gas, and radiation heat of part of the high-temperature gas or bright flame to the wall surface is taken away, so that a good protection effect is achieved, and the purpose that the blade is not burnt out by the high-temperature gas is achieved.

The original film cooling configuration was discrete cylindrical film holes, which had insufficient cooling capacity as the turbine inlet temperature increased, and the region between the holes was a weak region to be cooled. Cylindrical film holes are widely used in modern turbine blades due to their easy-to-machine characteristics. The reverse air film hole structure means that the air film hole jet flow direction is opposite to the main flow, and the reverse jet flow can improve the spreading diffusion capacity compared with the forward jet flow so as to solve the problem that the air film jet flow spreading of the cylindrical hole is insufficient in coverage. But the direction of the outlet of the air film hole is opposite to that of the main flow, the collision of the main flow and the secondary flow greatly increases the pressure loss, and the pit can reduce the pressure at the collision position and reduce the pressure loss.

Disclosure of Invention

In order to avoid the defects of the prior art, the invention provides a pit reverse air film hole structure for a turbine blade; the pit reverse air film hole structure can continuously improve the span-wise coverage range of jet flow of the transverse slot holes, reduce the flow resistance of the jet flow and reduce the pressure loss.

The invention solves the technical problem by adopting the technical scheme that the device comprises an air film pore plate, air film holes, scale-shaped pits, an inner cooling channel, pressure surface scale-shaped pit air film holes and suction surface scale-shaped pit air film holes, wherein the pressure surface of a turbine blade is provided with the pressure surface scale-shaped pit air film holes, the suction surface is provided with the suction surface scale-shaped pit air film holes, and the air film holes are communicated with the inner cooling channel;

the depth P of the fish scale type pits ranges from 0.3D_f～1D_fThe width H of the middle section of the fish scale type pit ranges from 1.5D_f～2.5D_fThe span-wise expansion angle alpha of the fish scale type pits ranges from 20 degrees to 35 degrees;

diameter D of the air film hole_fThe value range of (a) is 0.3-2 mm, and the value range of the flow direction inclination angle theta of the air film hole is 30-60 degrees; the space S of the fish scale type pits is the same as the span-wise space of the air film holes, and the value range is 3D_f～7D_f。

And the lower edge of the outlet of the air film hole is flush with the bottom of the fish scale type pit.

Advantageous effects

The invention provides a pit reverse air film hole structure for a turbine blade. The cross section of the fish scale type concave pits is parabolic, the space between the fish scale type concave pits is the same as the span-wise space between the air film holes, and the outlets of the air film holes are positioned at the bottoms of the fish scale type concave pits. The secondary flow cooling gas is mixed with the main flow after flowing out of the gas film hole, the flow direction velocity component is reduced after the reverse jet flow collides with the main flow, and the transverse velocity component is increased, so that the reverse jet flow can be better attached to the wall surface and has better transverse diffusion compared with the forward jet flow; in addition, the fish scale type pits can reduce flow loss caused by mixing of the main flow and the secondary flow, and enhance transverse diffusion of the secondary flow, so that cooling airflow in the air film hole flows through the cooled wall surface after being spread and diffused in the pits, and the spreading and covering capacity of the jet flow is greatly improved.

Compared with a flat reverse jet hole, the concave pit reverse air film hole structure for the turbine blade can reduce the mixing pressure of the main flow and the secondary flow by the fish scale type concave pit, thereby reducing the pressure loss during mixing. Meanwhile, the secondary flow cold air is ensured not to be completely dispersed by the main flow, and certain cooling performance can still be kept at the downstream of the outlet.

According to the invention, a low-pressure area is formed in the fish scale type pits of the pit reverse air film hole structure for the turbine blade, and after the secondary flow and the main flow are mixed, the secondary flow can be more attached to the wall surface due to the pressure effect, so that the wall surface cooling efficiency is improved, and the surface heat flux density is reduced, thereby achieving the effect of protecting the wall surface.

Drawings

The present invention will be described in further detail with reference to the accompanying drawings and embodiments.

FIG. 1 is a schematic view of a reverse pore structure of a hollow bubble.

FIG. 2 is a top view of a reverse cavitation hole configuration of the present invention.

FIG. 3 is a cross-sectional view of a reverse cavitation hole configuration of the present invention.

FIG. 4 is a schematic view of the location of the reverse air film hole structure of the present invention on the turbine blade.

In the drawings

1. Air film pore plate 2, air film pore 3, fish scale type pit 4, internal cooling channel 5, pressure surface fish scale type pit air film pore 6, suction surface fish scale type pit air film pore

A. Main flow gas B, cooling gas C, gas film hole center outflow D, gas film hole lateral outflow E, cooling gas film D_fDiameter of air film hole theta, flow direction inclination angle of air film hole S, pitch of fish scale type pits P, depth of fish scale type pits H, width of section in fish scale type pits alpha and expansion angle of fish scale type pits in spreading direction

Detailed Description

The present embodiment is a dimple reverse film hole configuration for a turbine blade.

Referring to fig. 1, 2, 3 and 4, the concave pit reverse air film hole structure for the turbine blade in the present embodiment is composed of an air film hole plate 1, an air film hole 2, a fish scale type concave pit 3, an internal cooling channel 4, a pressure surface fish scale type concave pit air film hole 5 and a suction surface fish scale type concave pit air film hole 6, wherein the pressure surface of the turbine blade is provided with a pressure surface fish scale type concave pit air filmThe hole 5, the suction surface sets up the suction surface fish scale type pit air film hole 6, the air film hole 2 communicates with inner cooling channel 4; wherein, the outlet part of the reverse air film hole 2 is provided with a fish scale type pit 3, and the outlet of the air film hole 2 is positioned at the bottom of the fish scale type pit 3. The cross section of the fish scale type concave pits is parabolic, the space between the fish scale type concave pits is the same as the span-wise space between the air film holes 2, and the fish scale type concave pits are arranged along the span-wise direction of the air film hole plate 1. The depth P of the fish scale type pit 3 ranges from 0.3D_f～1D_fThe width H of the middle section of the fish scale type pit 3 is 1.5D_f～2.5D_fThe span-wise expansion angle alpha of the fish scale type pits 3 ranges from 20 degrees to 35 degrees. The lower edge of the outlet of the air film hole 2 is flush with the bottom of the fish scale type pit 3.

In the embodiment, the cooling air flow B flows out along the air film holes with a certain inclination angle, wherein the outflow C at the center of the air film holes collides with the main flow gas A at the bottom of the fish scale type pit 3 and then flows out along the rear edge of the fish scale type pit 3 to form a cooling air film; and part of the air flows in the pits in a spreading way under the action of collision of the fish scale type pits 3 to form a lateral outflow D of the air film holes. Due to the collision effect of the main flow and the secondary flow, the lateral outflow D of the air film hole has a transverse flow speed which is equal to the width of the cooling air film E at the downstream of the air film hole, and meanwhile, the geometrical structure of the concave pit changes the rotating direction of the jet flow internal rotating vortex pair at the downstream of the air film hole, and the generated forward vortex pair can press the air film to be attached to the wall surface better without separation, so that the cooling effect is very good. On the other hand, the fish scale type pits can reduce the pressure when the main stream collides with the secondary stream, thereby reducing the pressure loss during blending.

The structure requirement of the fish scale type pit air film hole is as follows:

1. 2 diameter D of the gas film hole_fThe value range of (a) is 0.3-2 mm, and the value range of the flow direction inclination angle theta of the air film hole is 30-60 degrees;

2. the space S between the fish scale type pits 3 is the same as the span-wise space of the air film holes 2, and the value range is 3D_f～7D_f(ii) a Wherein the outlet of the air film hole 2 is positioned at the bottom of the fish scale type pit 3; the depth P of the fish scale type pit 3 ranges from 0.3D_f～1D_fThe width H of the middle section of the fish scale type pit 3 is 1.5D_f～2.5D_fThe span-wise expansion angle alpha of the fish scale type pits 3 ranges from 20 degrees to 35 degrees.

Example one

This embodiment is a dimple reverse film hole configuration for a turbine blade. Pressure surface scale type pit air film holes 5 are arranged on the pressure surface of the turbine blade, suction surface scale type pit air film holes 6 are arranged on the suction surface, and the air film holes 2 are communicated with an inner cooling channel 4; wherein, the outlet part of the reverse air film hole 2 is provided with a fish scale type pit 3, and the outlet of the air film hole 2 is positioned at the bottom of the fish scale type pit 3.

2 diameter D of the gas film hole_f1mm, and the flow direction inclination angle theta of the air film hole 2 is 30 degrees.

The space S between the fish scale type pits 3 is the same as the span-wise space of the air film holes 2, and is 5 times of the space D_fThe value was 5 mm.

The depth P of the fish scale type concave pits 3 is 0.8D_fThe value was 0.8 mm. The width H of the middle section of the fish scale type pit 3 is 2.5D_fThe value was 2.5 mm. The expansion angle alpha of the spanwise direction of the fish scale type pits is 25 degrees. Wherein the lower edge of the outlet of the air film hole 2 is flush with the bottom of the fish scale type pit 3.

In this embodiment, the width of the cross section of the fish-scale pit 3 is 2.5D_fThe spreading angle alpha of the fish scale type pits is 25 degrees, and the value range of the spreading angle alpha is a larger value. The larger cross section width and the expansion angle can effectively increase the transverse speed after secondary outflow, increase the spanwise coverage of the air film and reduce the local thermal stress of the wall surface. The depth P of the fish scale type pit is 0.8D_fThe mixing pressure in the pits can be effectively reduced, so that the air film can be attached to the wall surface after flowing out, the cooling efficiency of the air film is increased, and the heat flux density of the wall surface is reduced.

Example two

This embodiment is a dimple reverse film hole configuration for a turbine blade. Pressure surface scale type pit air film holes 5 are arranged on the pressure surface of the turbine blade, suction surface scale type pit air film holes 6 are arranged on the suction surface, and the air film holes 2 are communicated with an inner cooling channel 4; wherein, the outlet part of the reverse air film hole 2 is provided with a fish scale type pit 3, and the outlet of the air film hole 2 is positioned at the bottom of the fish scale type pit 3.

2 diameter D of the gas film hole_f1mm, air film hole 2The flow direction inclination angle theta is 35 deg..

The space S between the fish scale type pits 3 is the same as the span-wise space of the air film holes 2, and is 5 times of the space D_fThe value was 5 mm.

The depth P of the fish scale type concave pits 3 is 0.4D_fThe value was 0.4 mm. The width H of the middle section of the fish scale type pit 3 is 1.8D_fThe value was 1.8 mm. The spanwise expansion angle alpha of the fish scale shaped pits 3 is 20 degrees. Wherein the lower edge of the outlet of the air film hole 2 is flush with the bottom of the fish scale type pit 3.

The depth P of the fish scale type pits 3 in the embodiment is smaller, so that the pressure loss caused by collision of the main flow and the secondary flow is reduced, meanwhile, the momentum in the vertical direction of outflow of the pits is weakened, and the covering of the air film on the blades is facilitated. Meanwhile, the smaller cross section width and the smaller expansion angle of the pit can reduce the main air flow mixed with the secondary flow and increase the mass flow ratio of the secondary flow, so that the cooling air flow in the air film hole flows through the cooled wall surface after being spread in the pit, the spread coverage capacity of jet flow is greatly improved, and the cooling efficiency of the downstream of the air film is increased.