Double-slotting air film hole structure for improving air film cooling efficiency of turbine blade

Abstract

The utility model relates to a double-slotting air film hole structure for improving the air film cooling efficiency of a turbine blade. The double-slotting air film hole structure comprises air film holes, inlet and outlet transverse slots, a double-step structure and a wall surface, the novel groove is characterized in that an inlet groove is additionally arranged on the basis of a traditional outlet groove, the upstream wall face is arranged to be an inclined face, the downstream wall face is arranged to be in a double-layer step shape, the portion close to the groove bottom is a first step and is in a rectangular shape, and the lowest point of the first step is flush with the groove bottoms of the transverse grooves; the second step is close to the incoming flow, is arc-shaped and is connected with the highest point of the first step and the downstream wall surface, and the tangent line of the highest point is tangent to the downstream wall surface. The spanwise width of the steps is the same as the spanwise width of the outlet groove, the spanwise width of the structure ranges from 2D to 3D, the grooving height of the outlet groove ranges from 1D to 2D, the height of the downstream first step ranges from 0.5 D to 1D, the surface of the second step is subjected to rounding treatment, and the radius ranges from 0.3 D to 0.6 D. The inlet groove, the inclined plane and the double-step-shaped structure in the cooling structure can effectively play a role in enhancing air film cooling, and the cooling structure is convenient to machine and low in cost.

Description

Technical Field

[0001] The utility model belongs to the technical field of turbine blade cooling, and in particular relates to a structure for improving the air film cooling efficiency of the downstream wall surface of a slotted air film hole. Background Art

[0002] As an important power device, gas turbines are widely used in many fields such as aviation and navigation, chemical industry, energy and power engineering. Among them, the gas turbine inlet temperature has an important impact on the efficiency of the gas turbine. In order to increase the inlet temperature, it is necessary to continuously develop heat-resistant materials to protect the gas turbine and use cooling technology to reduce the temperature of the turbine blades, thereby ensuring the safe and reliable operation of the gas turbine. However, due to the limitations of the development and economic efficiency of high-temperature resistant materials, effective cooling measures must be taken to protect the turbine blades from damage in the high-temperature environment.

[0003] As a highly efficient cooling method for current aircraft engines, film cooling has been widely used in gas turbine cooling. Cooling holes are opened on the surface of the blades, and the inner cavity cooling medium is sprayed into the mainstream through the film holes. Under the pressure and friction of the mainstream, the cold air flow will cover the wall along the direction of the blade surface, forming a low-temperature cold air film, thereby playing a heat insulation role for high-temperature components.

[0004] Reasonable structures such as changing the geometric conditions of the film holes, the shape of the downstream wall, and adding transverse slots can effectively improve the transverse and longitudinal film cooling effects of the downstream wall of the film holes. Setting a slotted structure for the film holes can reduce the momentum of the cooling airflow at the outlet of the film holes, achieve a better film cooling effect, improve the film cooling efficiency, reduce the wall heat transfer coefficient, and thus reduce the surface heat flux ratio. In addition, arranging a protruding structure on the downstream wall can increase the lateral coverage area of ​​the cooling airflow and improve the film cooling efficiency. The Chinese patent with patent application number 202022258560.0 discloses a structure for improving the cooling efficiency of discrete hole film, that is, a double-step structure is set on the downstream side wall of the slot, thereby expanding the coverage area of ​​the cooling film on the downstream side wall and improving the span-wise film cooling efficiency of the wall. Although the above structure can improve the film cooling efficiency, it ignores the influence of the air intake rate of the film hole and the shape of the upstream wall on the film cooling efficiency. Utility Model Content

[0005] In view of the above-mentioned deficiencies, the utility model provides a new slotted structure to improve the cooling efficiency of the blade. The structure is optimized from two aspects: the entrance of the film hole and the downstream wall. An upper and lower double transverse slotted film hole structure is adopted to promote the transverse cooling efficiency of the film hole, improve the air intake efficiency of the film hole, enhance the uniformity of the air film coverage, expand the air film coverage area, and enhance the cooling efficiency. The structure is suitable for air film cooling technology with a slotted structure, has high economic benefits and is easy to process.

[0006] To achieve the above effects, the utility model proposes a double-slotted film hole structure for improving the film cooling efficiency of turbine blades, including a film hole, inlet and outlet transverse slots, a double-step structure and a wall surface, wherein the film hole is opened upstream of the turbine blade wall surface, and the transverse slots are respectively opened at the inlet and outlet positions of the film hole, characterized in that an inlet slot is added on the basis of the traditional film hole outlet slot, and the downstream slot wall of the outlet slot is set to a double-step structure, the first step is rectangular in shape, and its lowest point is flush with the slot bottom of the transverse slot, the second step is arc-shaped, connecting the highest point of the first step with the downstream wall surface, and the tangent line of the highest point is tangent to the downstream wall surface, the spanwise width of the above-mentioned double-step structure is the same as the spanwise width of the outlet slot, the spanwise width is 2D~3D, the height of the downstream first step is 0.5D~1D, the width of the first step along the mainstream direction is 0.5D~1D, the second step surface is rounded, and the arc radius is 0.3D~0.6D, wherein D is the diameter of the film hole.

[0007] Further, the step-like structure is located in the downstream area of ​​the corresponding slotted air film hole. Further, the step-like structure is a symmetrical structure in the spanwise width, and its spanwise width is the same as the spanwise width of the outlet slot.

[0008] Furthermore, the width of the transverse groove of the stepped structure at the outlet of the air film hole is 2D to 3D, and the depth of the groove is 1D to 2D.

[0009] Furthermore, the width of the transverse groove of the stepped structure at the entrance of the air film hole is 2D to 3D, and the depth of the groove is 0.5D to 2D.

[0010] Furthermore, the angle α between the upstream inclined surface and the upstream wall surface is set to 110° to 130°.

[0011] Furthermore, the air film hole is a circular air film hole, and an angle β between the air film hole and the mainstream flow direction is 20° to 60°.

[0012] As described above, the cooling structure involved in the utility model can achieve the following effects: the cooling airflow can better cover the downstream air film hole by blocking the upstream wall slope, so that the cooling gas coming out of the downstream air film hole is more efficient. The transverse slot at the entrance of the air film hole can make the cooling airflow enter the air film hole more fully, improve the air intake efficiency of the air film hole, and can improve the turbine aerodynamic acceleration performance to a certain extent through the structural coordination with the outlet transverse slot. A stepped slotted structure is provided in the downstream area of ​​the film hole outlet position, which increases the spanwise flow of the film hole jet in the stepped slotted structure, and increases the coverage area of ​​the air film by increasing the spanwise distribution of the air film in the downstream area. At the same time, a Coanda effect (a phenomenon in which a high-speed fluid along the surface of an object can adhere to the surface at a corner) occurs when the jet flows through the step surface of the first step and the arc-shaped second step, which promotes the cooling gas to better adhere to the wall surface and weakens the mixing effect of the cross flow and the film hole jet. This not only enhances the coverage rate of the upstream airflow on the downstream airflow, but also improves the stability of the downstream air film, thereby improving the efficiency of film cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the air film hole structure of the turbine blade in the utility model

[0014] 1. End wall air film hole 3. Turbine end wall 4. Turbine blade 5. Turbine blade internal cooling channel 6. Blade pressure surface air film hole 7. Blade suction surface air film hole

[0015] Figure 2 This is a schematic diagram of the layout of the stepped structure in the utility model

[0016] 1. End wall air film hole 2. Outlet transverse slot 3. Turbine end wall 8. Inclined surface 91. First step 92. Second step 10. Inlet transverse slot

[0017] Figure 3 A side view of the slotted air film hole in the utility model

[0018] 1. End wall air film hole 2. Outlet transverse slot 3. Turbine end wall 8. Inclined surface 91. First step 92. Second step 10. Inlet transverse slot

[0019] Figure 4 A top view of the slotted air film hole in the utility model

[0020] 1. End wall air film hole 2. Inlet transverse slot 3. Turbine end wall 8. Inclined surface DETAILED DESCRIPTION

[0021] The structure of the utility model is further described below in conjunction with specific embodiments and drawings. Figures 1 to 4The air film cooling structure of the utility model comprises an air film hole 1, an outlet transverse slot 2, an inlet transverse slot 10 and a wall surface 3. The air film hole 1 is arranged in the upstream area of ​​the wall surface. The outlet transverse slot 2 is arranged at the outlet position of the air film hole 1, and the inlet transverse slot 10 is arranged at the inlet position of the air film hole 1. The upstream part of the outlet transverse slot 2 close to the slot bottom is connected with the upstream wall surface in an inclined surface. A stepped structure is arranged on the downstream slot wall of the outlet transverse slot 2. The part of the stepped structure close to the slot bottom is a first step 91, and its outer surface is rectangular, and its lowest point is flush with the slot bottom of the transverse slot. The part of the stepped structure close to the wall surface is a second step 92, which is arc-shaped, connecting the highest point of the first step with the downstream wall surface, and the tangent line of the highest point is tangent to the downstream wall surface. The height of the first step is 0.5D to 1D, the width of the first step along the mainstream direction is 0.5D to 1D, and the second step is rounded, and the arc radius is 0.3D to 0.6D. The span width of the stepped structure is the same as the span width of the transverse slot, which is 2D to 3D, where D is the reference circle diameter of the air film hole 1.

[0022] Specifically, see Figure 1 An internal cooling channel 5 is arranged on the turbine blade 4, and the air film holes arranged on the turbine blade 2 include a blade pressure surface air film hole 6 and a blade suction surface air film hole 7, both of which have outlets on the blade surface. The end wall air film hole 1 is arranged on the turbine end wall 3, and its outlet is located on the wall surface of the end wall 3.

[0023] The angle α between the inclined surface structure 8 and the upstream wall surface of the utility model is 110°~130°. In the stepped cooling structure of the utility model, there are multiple air film holes arranged on the turbine blades 4 and the turbine end wall 3, and their sizes are not all the same. The size specifications of the stepped structure are determined by the air film holes at various positions. The utility model adopts cylindrical air film holes. The air film holes 1 are distributed in multiple rows in the horizontal direction, and the angle β between the end wall air film holes 1 and the mainstream flow direction is 20°~60°.

[0024] The utility model performs transverse groove processing on the inlet and outlet of the air film hole 1, and at the same time, an inclined surface structure is provided on the upstream groove wall of the outlet transverse groove 2, and a stepped structure is provided on the downstream groove wall. The basic principle of this method for improving the air film cooling efficiency is that when the cooling airflow generated by the upstream air film hole of the outlet transverse groove 2 covers the downstream, the cooling airflow is better covered on the downstream air film hole through the blocking and drainage effect of the inclined surface. The simultaneous transverse grooves at the inlet and outlet of the air film hole 1 can allow more cooling airflow to enter, improve the air intake efficiency of the air film hole, and at the same time can reduce flow losses to a certain extent and improve aerodynamic acceleration performance. The stepped structure is provided on the downstream groove wall of the outlet transverse groove 2, which reduces the resistance of the downstream groove wall to the cooling jet flowing out of the air film hole. At the same time, the Coanda effect occurs when the jet flows through the step surface of the first step and the arc-shaped second step, which prompts the cooling gas to better adhere to the wall surface and weakens the mixing effect of the cross flow and the air film hole jet.

[0025] The following is an embodiment of the utility model:

[0026] See also Figure 2 , a film hole 1 is provided on the wall surface 3 of the turbine end wall, an inlet transverse slot 10 is provided at the inlet position of the film hole, an outlet transverse slot 2 is provided at the outlet position of the film hole, and a stepped structure is provided on the downstream slot wall of the outlet transverse slot 2. The film hole 1 is a cylindrical film hole inclined along the mainstream flow direction, the inclination angle β is 30°, and the diameter of the film hole D=5mm. The height of the film hole H=3D=15mm, the angle α between the inclined surface and the upstream wall surface is 120°, the height of the first step 91 h=1D=5mm, the width of the first step 91 along the mainstream direction is L=1D=5mm, the height of the second step 92 is 1D=5mm, the arc radius is 0.3D=1.5mm, the highest point of the first and second steps 91 and 92 is smoothly transitioned to the wall surface, and the depth of the inlet and outlet transverse slots has a greater influence on the effect of film cooling, so both are taken as 1.8D=9mm. The wider the outlet transverse slot is, the better the wall adhesion of the cooling jet is, the cooling air film will cover the entire downstream area of ​​the outlet position of the air film hole 1, and the air film cooling efficiency will also be improved. Therefore, in this embodiment, the total distance from the vertical wall upstream of the transverse slot to the air film hole 1 and the first step 91 to the air film hole 1 is 2.2D = 11mm.

[0027] In this embodiment, high-temperature combustion gas flows through the hot side surface, and the cooling jet enters from the entrance of the film hole with a diameter of D=5mm. After the upstream inclined surface covers the upstream cooling gas, it flows into the stepped structure through the film hole 1. The transverse grooves at the entrance of the film hole can enable the cooling airflow to enter the film hole more fully, thereby improving the air intake efficiency of the film hole. The structural coordination with the outlet transverse grooves can improve the turbine aerodynamic acceleration performance to a certain extent. The outlet groove structure increases the spanwise flow of the cooling jet. The rectangular surfaces and arc surfaces of the first and second steps 91 and 92 are conducive to improving the adhesion of the cooling airflow to the wall, enhancing the stability of the downstream air film, thereby improving the film cooling efficiency.

[0028] In summary, the utility model overcomes the shortcomings of the prior art, can effectively improve the air film cooling effect of turbine blades, and has a simple structure and is easy to process.

[0029] The above embodiments are only illustrative of the principles and functions of the present invention, and professionals familiar with the technology can make modifications based on them.

Claims

1. A double-slotted film hole structure for improving the film cooling efficiency of turbine blades, comprising a film hole, an inlet and outlet transverse slot, a double-step structure and a wall surface, wherein the film hole is opened upstream of the turbine blade wall surface, and the transverse slots are respectively opened at the inlet and outlet positions of the film hole, and the characteristics are as follows: On the basis of the traditional air film hole outlet slot, an inlet slot is added, and the downstream slot wall of the outlet slot is set to a double-step structure. The first step is rectangular in shape, and its lowest point is flush with the bottom of the transverse slot. The second step is arc-shaped, connecting the highest point of the first step with the downstream wall, and the tangent of the highest point is tangent to the downstream wall. The spanwise width of the above-mentioned double-step structure is the same as the spanwise width of the outlet slot, and the spanwise width is 2D~3D. The height of the first downstream step is 0.5D~1D, and the width of the first step along the mainstream direction is 0.5D~1D. The surface of the second step is chamfered, and the arc radius is 0.3D~0.6D, where D is the diameter of the air film hole.

2. A double-slotted film hole structure for improving film cooling efficiency of turbine blades according to claim 1, characterized in that The width of the transverse groove at the outlet of the air film hole is 2D to 3D, and the depth of the groove is 1D to 2D.

3. A double-slotted film hole structure for improving film cooling efficiency of turbine blades according to claim 1, characterized in that The width of the transverse groove at the entrance of the air film hole is 2D to 3D, and the depth of the groove is 0.5D to 2D.

4. A double-slotted film hole structure for improving film cooling efficiency of turbine blades according to claim 1, characterized in that The angle α between the upstream inclined surface and the upstream wall surface is 110° to 130°.

5. The double-slotted film hole structure for improving film cooling efficiency of turbine blades according to claim 1, characterized in that The air film hole is a circular air film hole.

6. The double-slotted film hole structure for improving film cooling efficiency of turbine blades according to claim 1, characterized in that The angle β between the air film hole and the mainstream flow direction is 20° to 60°.

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