WO2021104002A1

WO2021104002A1 - Curvilinear exhaust slit structure for trailing edge of turbine blade

Info

Publication number: WO2021104002A1
Application number: PCT/CN2020/127687
Authority: WO
Inventors: 吕东; 孔星傲; 王晓放; 王楠; 孙一楠
Original assignee: 大连理工大学
Priority date: 2019-11-29
Filing date: 2020-11-10
Publication date: 2021-06-03
Also published as: WO2021104002A9; CN111022127B; CN111022127A

Abstract

A curvilinear exhaust slit structure for a trailing edge of a turbine blade, comprising a hollow turbine blade (1), an inner cavity cooling gas passage (2), trailing edge exhaust slit passages (3) and trailing edge slit ribs (4). The inner cavity cooling gas passage (2) is provided inside the hollow turbine blade (1) for a low-temperature cooling gas to flow inside the blade, so as to cool the blade. The trailing edge of the hollow turbine blade is provided with the trailing edge slit ribs (4) arranged side by side, and the trailing edge exhaust slit passages (3) are formed between the trailing edge slit ribs (4) arranged side by side, so as to discharge the cooling gas out of the blade. Slits of the trailing edge of the blade is designed to perform exhaust in an inclined curvilinear manner, reducing the turning angle of the cooling gas in the slits, so that the turning process is continuous and gentle, thereby reducing the flow resistance and loss of the cooling gas in the inner cavity of the blade, and reducing the flow resistance by about 20%.

Description

Curved exhaust slit structure for trailing edge of turbine blade

Technical field

The invention belongs to the technical field of aeroengine turbine cooling, and relates to a curved exhaust split structure at the trailing edge of a turbine blade.

Background technique

Increasing the gas temperature in front of the turbine can greatly improve the performance of aeroengines and gas turbines. However, the current gas temperature in front of the turbine is far beyond the limit of the materials used. Therefore, it is urgent to develop more effective turbine blade cooling technology. At present, the hollow design is generally used for turbine blades, and the use of the cooling gas in the interior of the enhanced convection heat transfer and the formation of a gas film to isolate the gas heating when discharging the blades is the main solution to the cooling problem of the turbine blades. At the same time, the blades are required " “Larger internal heat exchange area”, “lower resistance to cold air flow”, “higher heat exchange efficiency”, “larger air film coverage area”, and “less damage to structural strength” are the key points and reasons for blade cooling design. the goal that is pursued.

The trailing edge area of the turbine blade is heated by the gas from both the bowl side and the back side of the blade. In addition, the structure is thinner and difficult to form a hollow cooling structure. Therefore, it is the area in the blade that is more difficult to cool, and the wall temperature is relatively high during operation. High and ablation-prone areas are problems that need to be addressed in the blade cooling design. At present, the cooling of the blade trailing edge often adopts a half-open horizontal exhaust split structure, which can turn the cold air flowing in the radial direction in the internal cooling channel of the blade into a chord direction, and form an intensified convection cooling on the channel wall and the rib structure. , And then discharged from the narrow slits (called slits) on the side edge of the blade basin, and form a gas film covering the tail edge to isolate the heating of the gas. The typical structure is shown in Figure 1, and its basic feature is the horizontal row of slits. gas. This type of trailing edge split cooling structure has greater flow resistance and lower cooling effect, and it also damages the strength of the blade structure to a certain extent.

technical problem

In view of the shortcomings of the existing horizontal exhaust trailing edge splitting cooling technology, a curved exhaust splitting structure for the trailing edge of the turbine blade is provided. By designing the trailing edge splitting of the turbine blade as a curved inclined exhaust, it can be effectively Reduce the turning angle of the cooling air, improve the smoothness of the cooling air flow, reduce the flow resistance, increase the air film coverage width, strengthen the heat exchange effect, improve the structural load resistance, and improve the casting process of the blade.

Technical solutions

The technical scheme of the present invention:

A trailing edge curved exhaust slit structure of a turbine blade , comprising a hollow turbine blade, an inner cavity cold air channel, a trailing edge exhaust slit channel and a trailing edge split rib;

The hollow turbine blade is provided with an inner cavity cold air passage for low-temperature cooling gas to flow inside the blade to cool the blade. The trailing edge of the hollow turbine blade is provided with trailing edge split ribs arranged side by side, and the trailing edge splitting ribs arranged side by side form a trailing edge exhaust split channel for cooling air to exit the blade, and at the same time, the trailing edge of the blade Air film cover cooling. The structure of the trailing edge split ribs can not only increase the heat exchange area inside the blade, but also guide the cooling air in the inner cavity of the blade to change the flow direction.

The structural shape of the trailing edge splitting ribs is controlled by the centerline of the separating ribs. The centerline of the separating ribs is a circular arc or a spline curve, and the corresponding trailing edge splitting ribs form a circular arc or spline shape. The width of the trailing edge split ribs is symmetrically distributed along the center line of the ribs. The angle between the tangent direction of the trailing edge exhaust slit centerline at the cold air inlet and outlet ends of the hollow turbine blade and the horizontal plane is the incident angle ∠A1 and the exit angle ∠A2, and ∠A1>∠A2, the cold air enters the trailing edge slit The angle between the subsequent flow direction and the flow direction before entering the trailing edge split is less than 90°.

Further, the incident angle ∠A1 can be 15~45°, the exit angle ∠A2 can be 0~30°, and the cooling air turning angle ∠A is at this time.

In the original structure, as shown in Figure 1, the centerline of the ribs is a horizontal straight line, and the air inlet/outlet angles ∠A1 and ∠A2 are both 0° in the tail edge split. At this time, the air-conditioning turning angle ∠A is about 90 °, if the turning angle is too large, the flow loss is large, and the air film coverage area is small and the strength damage is large. In the solution of the present invention, when the centerline of the rib becomes an inclined curve, the air inlet/outlet angles ∠A1 and ∠A2 in the tail edge split are both acute angles, and the cooling air turning angle becomes an acute angle accordingly, and The cold air flows in the curved channel, the turning process is more continuous and gentle, and the flow is smoother, thereby reducing the flow resistance and loss, while increasing the air film coverage area and improving the load resistance of the hollow structure of the trailing edge.

Principle of the present invention:

1. The inclined curve structure of the present invention reduces the flow resistance and loss of cold air in the inner cavity of the blade:

Compared with the original horizontal exhaust trailing edge split structure, the present invention has beneficial effects first of all to reduce the flow resistance and loss of cold air. For the horizontal exhaust trailing edge split structure, the cooling air needs to complete a 90° turn at a high speed in a narrow space. This type of flow will form an approximate step flow on the leeward side of the end of the rib, resulting in a low-speed vortex, such as As shown in Figure 3, the vortex flow not only generates energy dissipation due to its strong friction, but also squeezes the main flow to force it to produce additional direction turning and energy loss. The driving of the cold air flow requires the extraction of energy from the entire engine. Therefore, this type of high resistance flow will increase the power consumption of the entire machine, resulting in a decrease in efficiency. When the ribs of the split are changed from horizontal to a sloping curve structure, the turning angle of the cooling air in the split changes from an approximate right angle to an acute angle, and the value is reduced by more than 40%. In addition, when the cold air flows in the curved channel, the turning process becomes more continuous and gentle, especially on the leeward side of the ribs. No obvious steps are formed on the leeward side of the ribs, and the vortex cannot be formed, making the flow smoother. Under the same flow rate, While reducing the flow resistance and loss, it will also increase the efficiency of the engine.

2. The inclined curve structure of the present invention improves the air film covering effect of the trailing edge area of the blade:

When the cooling air is discharged through the slits of the trailing edge, it will form an air film covering the trailing edge structure of the blade to isolate it from heating by the gas on the side of the blade basin. For the horizontal exhaust trailing edge split, the direction of the cold air flow is almost parallel to the gas, and the cold air will not deflect in the radial direction under the entrapment of the gas. Therefore, for a single split, the width of the air film coverage is equal to that of the gas. The actual width of the slit is nearly the same. The barrier rib area between two adjacent slits can hardly be covered by the gas film. The area that the gas film cannot cover is called the “dead zone” of the gas film. The cooling effect here is poor, and it is easy to cause high temperature. Ablation. For the slant curve exhaust trailing edge split, the gas film outflow direction and the gas flow direction are at a certain angle, which can be approximated as ∠A2, because the gas entraps the gas film outflow, so that the cold air flows in the direction of flow. Shows a tendency to deflect and gradually parallel to the gas flow direction, thereby realizing the coverage of part of the rib area, so that the coverage width of the actual gas film outflow is greatly increased relative to the slit width, as shown in Figure 4 . It is even possible to optimize the design so that the original air film covering "dead zone" between two adjacent splits is completely eliminated, forming an air film covering all the trailing edges of the blades, reducing the blades without increasing the amount of air-conditioning. Temperature level, so as to realize the improvement of engine safety under the premise of ensuring economy.

3. The inclined curve structure of the present invention improves the load resistance of the hollow structure of the trailing edge of the blade:

Turbine blades are mainly subjected to the following loads during operation: centrifugal load caused by high-speed rotation, aerodynamic load imposed by gas flow, and vibration load caused by vibration. These loads exert tension, torsion and bending on the blade base. Wait for the deformation tendency and produce the corresponding stress, in addition to the thermal stress caused by the uneven thermal expansion. These stresses are coupled together and act on the component for a long time and alternately, and damage will occur when the material exceeds the limit that the material can withstand. The design of the blade structure needs to optimize the use of the least materials to withstand these loads to avoid the existence of high stress areas and blade damage. The trailing edge split structure is a vulnerable area with high stress levels in the turbine blade. This area is first located at the thinnest part of the airfoil. In addition, the hollow structure of the split greatly weakens the strength, so that the opening of the split There will be stress concentration. As shown in Figure 5(b), the stress level of the trailing edge split structure shows a periodic law along the blade height direction under the action of radial tensile load, and the stress peak appears at the split opening, while at the ribs Then there is a trough. For horizontal exhaust trailing edge splitting, because at the cross-sectional position shown in Figure 5(a), the material at the trailing edge has a high degree of hollowing and lacks effective support and reinforcement, so this periodicity is more obvious. , And the peak value is also higher. When adopting the slanted curve exhaust trailing edge split structure, as shown in Figure 5(c), it can be realized that there is a rib structure at any cross-sectional position to connect the two sides of the basin back of the blade, thereby strengthening the trailing edge structure , The stress level is improved, the structure's anti-load ability is improved, and the safety and reliability of the whole machine are also improved. From the comparison of the trailing edge stress distribution along the blade height shown in Figure 5(b), it can be seen that the peak stress of the inclined curve exhaust trailing edge split structure is significantly smaller than that of the horizontal exhaust mode.

4. The inclined curve structure of the present invention improves blade casting processability:

Turbine blades are parts with higher manufacturing costs. They usually use precision casting with no margin, and the pass rate is low, especially for single crystal turbine blades (the molten metal crystallizes into a crystal grain when solidified, which is more expensive than polycrystalline blades). Better mechanical properties and gas corrosion resistance at high temperatures), it is necessary to adopt a directional solidification process, that is, the molten metal is gradually cooled from bottom to top to a solidified state. Because the volume of the metal decreases from liquid to solid, the structural design of the blade and the corresponding manufacturing process design must ensure that the liquid metal has good fluidity in the casting shell and can be supplemented in time to solidify and shrink The resulting space is called feeding. If the feeding path of the molten metal is blocked and the feeding is insufficient, dense small holes will be generated when the molten metal in the corresponding area solidifies, which is called a loose phenomenon. The looseness will cause the mechanical properties of the material and the load resistance of the blade to drop significantly, which is a serious quality problem and must be scrapped. For the horizontal exhaust trailing edge split structure, as shown on the left side of Figure 6, the liquid-solid interface of the metal will show a slightly downwardly concave shape due to the lower temperature on the outside of the blade than the inside, which will result in a part of the rib structure. The feeding path is blocked, so the horizontal rib structure is prone to looseness, and the blade casting process is poor. As for the trailing edge split structure of the inclined curve exhaust gas, as shown on the right side of Figure 6, the rib structure and the liquid-solid boundary are at a certain angle, and the inclined rib structure just forms a channel for liquid metal feeding. , To avoid the generation of looseness, thereby improving the casting process of the blade.

Beneficial effect

The curved exhaust trailing edge split cooling structure of the turbine blade proposed in the present invention, by designing the trailing edge splitting of the blade into an inclined curved exhaust, reduces the turning angle of the cooling gas in the split, so that the turning process is continuous and gentle , Thereby reducing the flow resistance and loss of cold air in the inner cavity of the blade, which can reduce the flow resistance by about 20%. The gas film outflow direction of the inclined curve exhaust gas is at a certain angle with the gas flow direction, so that the gas has a binding effect on the gas film outflow to improve the gas film coverage effect of the trailing edge area of the blade, which can increase the heat exchange by about 11% . By designing the ribs into an inclined curve structure to strengthen the hollow structure of the blade trailing edge, compared with the horizontal exhaust trailing edge split cooling structure, the load resistance of the blade trailing edge structure can be increased by about 21%. In addition, the inclined rib structure can form a channel for liquid metal feeding, thereby improving the manufacturability of the blade casting, and can increase the casting qualification rate by about 15%.

Description of the drawings

Figure 1 (a) The existing horizontal exhaust split structure diagram of the trailing edge of the turbine blade.

Figure 1(b) C-C cross-sectional view of the existing horizontal exhaust split structure at the trailing edge of the turbine blade.

Figure 1(c) is a partial enlarged view of the existing horizontal exhaust slit structure at the trailing edge of the turbine blade.

Figure 2 (a) The structure diagram of the curved exhaust slit at the trailing edge of the turbine blade.

Figure 2(b) A partial enlarged view of the curved exhaust slit structure of the trailing edge of the turbine blade.

Figure 3 Comparison of the flow of cooling air in the two trailing edge split structures.

Figure 4 Comparison of air film covering effects of two trailing edge split structures.

Fig. 5(a) is a schematic diagram of the cross-sectional shape of the blade profile of the existing horizontal exhaust split structure at the trailing edge of the turbine blade.

Figure 5(b) Comparison of stress levels between two trailing edge split structures.

Figure 5(c) Schematic diagram of the cross-sectional shape of the blade profile of the curved exhaust slit structure at the trailing edge of the turbine blade.

Figure 6 Comparison of the processability of directional solidification casting with two trailing edge split joint structures.

In the picture: 1. Hollow turbine blade; 2. Inner cavity cold air passage; 3. Tail-edge exhaust slit passage; 4. Tail-edge split ribs; 5. Central line of ribs; 6. Tail-edge exhaust slits Centerline; 7. Incident angle ∠A1; 8. Exit angle ∠A2; 9. Cold air turning angle ∠A; 10. Cold air channel partition wall; 11. Cold air film coverage area; 12. Air film coverage width; 13. Cleavage High stress area at the opening; 14. Low stress area at the split rib.

Embodiments of the present invention

In order to make the content of the present invention easier to be understood clearly, the following further describes the present invention in detail based on specific embodiments in conjunction with the accompanying drawings.

Example 1:

Please refer to Figure 2. A trailing edge curved exhaust slit structure of a turbine blade, comprising a hollow turbine blade 1, an inner cavity cold air channel 2, a trailing edge exhaust slit channel 3, and a trailing edge split rib 4;

The hollow turbine blade 1 is provided with an inner cavity cold air passage 2 for low-temperature cooling gas to flow inside the blade to cool the blade. The trailing edge of the hollow turbine blade 1 is provided with trailing edge splitting ribs 4 arranged side by side, and a trailing edge exhaust splitting channel 3 is formed between the trailing edge splitting ribs 4 arranged side by side for cooling air to exit the blades, and at the same time. The trailing edge of the blade is cooled by air film covering. The structure of the trailing edge split ribs 4 can not only increase the internal heat exchange area of the blade, but also guide the cooling air in the inner cavity of the blade to change the flow direction.

The structural shape of the trailing edge split ribs 4 is controlled by the centerline 5 of the ribs. The centerline 5 of the ribs is a circular arc or a spline curve, which corresponds to the trailing edge split ribs 4 to form an arc or spline curve. . The width of the trailing edge split ribs 4 is symmetrically distributed along the center line 5 of the ribs. The angle between the tangent direction of the trailing edge exhaust split centerline 6 at the cold air inlet and outlet ends of the hollow turbine blade 1 and the horizontal plane is the incident angle ∠A1 and the exit angle ∠A2, and ∠A1>∠A2. Typical values can be ∠A1=45° and ∠A2=30°. At this time, the cooling air turning angle ∠A is about 45°.

Example 2:

The structural shape of the trailing edge splitting ribs 4 is controlled by the centerline 5 of the separating ribs. The centerline 5 of the separating ribs is a circular arc or a spline curve, and the corresponding trailing edge splitting ribs 4 form a circular arc or spline shape. The width of the trailing edge split ribs 4 is symmetrically distributed along the center line 5 of the ribs. The angle between the tangent direction of the trailing edge exhaust split centerline 6 at the cold air inlet and outlet ends of the hollow turbine blade 1 and the horizontal plane is the incident angle ∠A1 and the exit angle ∠A2, and ∠A1>∠A2. Typical values can be ∠A1=15° and ∠A2=0°, at this time the air-conditioning turning angle ∠A is about 75°.

Example 3:

The structural shape of the trailing edge splitting ribs 4 is controlled by the centerline 5 of the separating ribs. The centerline 5 of the separating ribs is a circular arc or a spline curve, and the corresponding trailing edge splitting ribs 4 form a circular arc or spline shape. The width of the trailing edge split ribs 4 is symmetrically distributed along the center line 5 of the ribs. The angle between the tangent direction of the trailing edge exhaust split centerline 6 at the cold air inlet and outlet ends of the hollow turbine blade 1 and the horizontal plane is the incident angle ∠A1 and the exit angle ∠A2, and ∠A1>∠A2. Typical values can be ∠A1=25° and ∠A2=15°. At this time, the cooling air turning angle ∠A is about 65°.

Claims

A trailing edge curved exhaust slit structure of a turbine blade, which is characterized by comprising a hollow turbine blade (1), an inner cavity cold air channel (2), a trailing edge exhaust slit channel (3) and a trailing edge slit partition. Rib (4);

The hollow turbine blade (1) is provided with an inner cavity cold air channel (2), the trailing edge of the hollow turbine blade (1) is provided with trailing edge split ribs (4) arranged side by side, and the trailing edge splitting ribs (4) arranged side by side are arranged side by side. A trailing edge exhaust split channel (3) is formed between the ribs (4). The structural shape of the trailing edge split ribs (4) is controlled by the rib center line (5), and the rib center line (5) is a circular arc Or a spline curve, corresponding to the trailing edge split ribs (4) forming an arc or spline curve; the width of the trailing edge split ribs (4) is symmetrically distributed along the centerline (5) of the ribs.
The trailing edge of a turbine blade tapered inclined exhaust slit structure according to claim 1, characterized in that the centerline (6) of the trailing edge exhaust slit is at the cold air inlet end of the hollow turbine blade (1) and The angle between the tangent direction of the exit end and the horizontal plane is the incident angle ∠A1 and the exit angle ∠A2, and ∠A1>∠A2.
The trailing edge of a turbine blade of claim 2, wherein the angle of incidence ∠A1 is 15~45°, and the angle of exit ∠A2 is 0~30°. , At this time, the air-conditioning turning angle ∠A is 90°-∠A1.