Flat seam-shaped air film hole cooling structure applied to hot end component of gas turbine

Abstract

The invention provides a flat seam-shaped air film hole cooling structure applied to a hot end component of a gas turbine, and relates to the technical field of heat transfer and cooling of the hot end component of the gas turbine, the flat seam-shaped air film hole cooling structure comprises an air film hole, the air film hole is composed of a special-shaped section which expands in the spanwise direction and contracts in the flow direction or slightly expands, and the special-shaped section is a ruled surface composed of an inlet molded line and an outlet molded line. The inlet molded line is in an oval shape, the oval shape comprises a long axis a and a short axis b, the outlet molded line is in a rectangular shape, and a rounding structure is arranged on the outlet molded line; improvement is carried out based on a traditional flat seam-shaped hole, the development of kidney-shaped vortexes in the hole is inhibited by increasing the spanwise width of the inlet, kidney-shaped vortex pairs near the center line of the traditional flat seam-shaped hole can be effectively eliminated, the wall attachment effect of an air film near the downstream center line of a wake is improved, and therefore the cooling efficiency of the air film near the center line is improved; and meanwhile, the temperature uniformity in the spanwise direction is improved, and the wall surface temperature gradient is reduced, so that thermal stress is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of heat transfer and cooling of hot end components of a gas turbine, and in particular to a flat slit-shaped air film hole cooling structure applied to the hot end components of a gas turbine. Background Art

[0002] The gas turbine engine is a thermal power device based on the Brayton cycle. It has been widely used in modern military and industry due to its powerful output power and high thermal efficiency. The gas turbine engine has an extremely harsh working environment, with three characteristics: high temperature, high pressure and high speed. Among them, the high temperature working environment is particularly reflected in the turbine, one of the three core components. Experience shows that under the premise that the engine size remains unchanged, the thrust of the gas turbine can be increased by 8% to 13% and the cycle efficiency can be increased by 2% to 4% for every 56K increase in the turbine inlet temperature. At present, the turbine inlet temperature of advanced aircraft engines has exceeded 2000K, while the temperature resistance limit of the turbine blade material is much lower than the turbine inlet temperature. Therefore, efficient cooling technology must be used to ensure its normal operation.

[0003] Film cooling technology is one of the most widely used high-efficiency cooling technologies. Its most ideal form is a continuous slit structure, so that the cold air outflow evenly covers the hot side wall surface. However, due to factors such as structural stress, it is difficult to open a continuous slit structure in the hot end components in actual applications. Therefore, film cooling is often used in gas turbine engines in the form of discrete holes.

[0004] One of the discrete cooling hole structures with the best cooling effect at present is the convergent slit hole. However, the convergent slit hole often has the defect of uneven air film coverage. Although the counter-rotating vortices formed by the convergent slit hole are mainly anti-kidney vortices, kidney-shaped vortices may be formed near the center line, so that the air film near the center line is separated from the wall surface, and the hot side wall near the center line loses the protection of the air film, forming a local high temperature area and generating large thermal stress. Therefore, the present invention proposes a flat slit air film hole cooling structure applied to the hot end component of a gas turbine to solve the problems existing in the prior art. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to propose a flat slit-shaped air film hole cooling structure applied to the hot end components of a gas turbine. This flat slit-shaped air film hole cooling structure applied to the hot end components of a gas turbine has the advantages of effectively eliminating the kidney-shaped vortex pairs near the center line of the traditional flat slit-shaped hole and improving the air film wall attachment effect near the downstream center line of the wake, and can solve the problems in the prior art.

[0006] To achieve the purpose of the present invention, the present invention is implemented through the following technical scheme: a flat slit-shaped air film hole cooling structure applied to the hot end component of a gas turbine, including an air film hole, wherein the air film hole is composed of a special-shaped segment that expands in the span direction and contracts or slightly expands in the flow direction, and the special-shaped segment is a straight surface composed of an inlet profile and an outlet profile, wherein the inlet profile is an ellipse, and the ellipse has a major axis a and a minor axis b, and the outlet profile is a rectangle, and a chamfered structure is provided on the outlet profile.

[0007] A further improvement is that the calculation formula for the equivalent diameter D of the inlet profile is:

[0008]

[0009] A further improvement is that the flow direction inclination angle α of the air film hole is 30-90°, and the span direction inclination angle β of the air film hole is 30-150°.

[0010] A further improvement is that the transverse hole spacing between a group of the air film holes and its adjacent air film holes is P, and the transverse hole spacing is a ratio of P to the equivalent diameter D ≥3.

[0011] A further improvement is that: the minor axis b is located in the mainstream direction, the major axis a>equivalent diameter D, and the minor axis b<D / sinα.

[0012] A further improvement is that the rounded structures are respectively the first rounded and the second rounded, and the construction method thereof is:

[0013] S1: The axis of the film hole intersects with the side wall of the mainstream gas to obtain the intersection point O;

[0014] S2: Draw a rectangle with a length of W and a width of H with the intersection point O as the center;

[0015] S3: fillet the upper left and lower left vertices of the rectangle corresponding to the upstream of the incoming flow direction, with a fillet radius of R1, to obtain a fillet;

[0016] S4: rounding the upper right and lower right vertices of the rectangle corresponding to the downstream of the incoming flow direction, with a rounding radius of R2, to obtain a rounding.

[0017] A further improvement is that the width H is 0.2D to 1.8D, the radius R1 is 0.5 to 0.8H, and R1+R2=H.

[0018] A further improvement is that when the width H<minor axis b, the special-shaped section shrinks along the flow direction and becomes a flat convergent slit-shaped hole; when the width H=minor axis b, the special-shaped section neither expands nor shrinks along the flow direction; when the width H>minor axis b, the special-shaped section expands along the flow direction and becomes a flat expansion slit-shaped hole.

[0019] The beneficial effects of the present invention are as follows: the flat slit-shaped film hole cooling structure applied to the hot end components of a gas turbine is improved based on the traditional flat slit-shaped hole. By increasing the spanwise width of the inlet, the development of the kidney-shaped vortex in the hole is suppressed, and the kidney-shaped vortex pair near the center line of the traditional flat slit-shaped hole can be effectively eliminated, and the film wall attachment effect near the center line downstream of the wake is enhanced, thereby improving the film cooling efficiency near the center line, while improving the temperature uniformity along the spanwise direction, reducing the wall temperature gradient and thus reducing thermal stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0021] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention.

[0022] Figure 2 It is a top view schematic diagram of the present invention.

[0023] Figure 3 It is a front view schematic diagram of the present invention.

[0024] Figure 4 It is an axial schematic diagram of the present invention.

[0025] Figure 5 It is a schematic diagram of the present invention applied to flat plate air film cooling.

[0026] Figure 6 It is a schematic diagram of a comparison curve of the spanwise average film cooling efficiency of the present invention and the classic convergent slit-shaped hole with the same outlet profile and the same equivalent diameter within a flow direction distance of 40D downstream of the film hole.

[0027] Figure 7 It is a schematic diagram of a comparison curve of the film cooling efficiency of the present invention and the classic convergent slit-shaped hole with the same outlet profile and the same equivalent diameter on the downstream center line of the film hole.

[0028] Figure 8 It is a schematic diagram of the spanwise film cooling efficiency distribution curve of the present invention and the classic convergent slit-shaped hole with the same outlet profile 1 and the same equivalent diameter D at a flow distance 10D downstream of the film hole.

[0029] Fig. 9 It is a schematic diagram of the spanwise film cooling efficiency distribution curve of the classic convergent slit-shaped hole with the same outlet profile 1 and the same equivalent diameter D at a flow direction distance 20D downstream of the film hole of the present invention.

[0030] Fig.10 It is a schematic diagram of the flow vorticity cloud diagram and velocity vector of the cross section 5D downstream of the air film hole of the present invention.

[0031] Fig.11 It is a flow vortex cloud diagram and velocity vector schematic diagram of a classic convergent slot hole with the same outlet profile 1 and the same equivalent diameter D as the flat slot hole of the present invention in the cross section 5D downstream of the air film hole.

[0032] Fig.12 It is a schematic diagram of the cooling effect cloud diagram within the downstream 40D range of the present invention.

[0033] Fig.13 It is a schematic diagram of the cooling effect cloud diagram of a classic convergent slot-shaped hole with the same outlet profile 1 and the same equivalent diameter D as the flat slot-shaped hole of the present invention within the downstream 40D range.

[0034] Among them: 1. Special-shaped section; 2. Inlet profile; 3. Outlet profile; 4. First fillet; 5. Rectangle; 6. Second fillet; 7. Cooling gas; 8. Flat plate; 9. High-temperature mainstream. DETAILED DESCRIPTION

[0035] In order to deepen the understanding of the present invention, the present invention will be further described in detail below in conjunction with examples. The examples are only used to explain the present invention and do not constitute a limitation on the protection scope of the present invention.

[0036] As one of the most widely used efficient cooling technologies, film cooling technology has the most ideal form of a continuous slit structure, which allows the cold air outflow to evenly cover the hot side wall. However, due to factors such as structural stress, it is difficult to open a continuous slit structure in the hot end components in actual applications. Therefore, film cooling is often used in gas turbine engines in the form of discrete holes. One of the discrete cooling hole structures with the best cooling effect is the convergent slit hole, which gradually transitions the film hole from a cylindrical cross section to a flat slit cross section by means of spanwise expansion and flowwise contraction. On the one hand, spanwise expansion enables the convergent slit hole to have a larger outlet width, increases the spanwise coverage of the wake, and increases the spacing between the kidney vortex pairs to suppress their induced lift; on the other hand, flowwise contraction can have a rectifying effect on the cold air, and the reduction of the flow area in the film hole can increase the cold air outlet velocity, reduce aerodynamic mixing losses, and suppress flow separation in the hole, promoting the formation of anti-kidney vortices.

[0037] However, convergent slit holes often have the defect of uneven air film coverage. Although the counter-rotating vortices formed by the convergent slit holes are mainly anti-kidney vortices, kidney-shaped vortices may form near the center line, causing the air film near the center line to detach from the wall, causing the hot side wall near the center line to lose the protection of the air film, forming a local high temperature area and generating greater thermal stress.

[0038] Therefore, according to Figure 1-Figure 13 As shown, this embodiment provides a flat slit-shaped film hole cooling structure applied to the hot end component of a gas turbine, including a film hole, a flow direction inclination angle α of the film hole is 30 to 90°, a span direction inclination angle β of the film hole is 30 to 150°, the film hole is composed of a profiled section 2 that expands in the span direction and contracts or slightly expands in the flow direction, the profiled section 2 is a straight surface composed of an inlet profile 3 and an outlet profile 1, the inlet profile 3 is an ellipse, located on the section of the inner wall surface on the cold air side, the ellipse is a major axis a and a minor axis b, the minor axis b is located in the mainstream direction, the major axis a>equivalent diameter D, the minor axis b<D / sinα, the outlet profile 1 is a rectangle 5, and a chamfered structure is provided on the outlet profile 1, which is located on the section of the outer wall surface on the mainstream gas side, and for a flat plate model, the inlet and outlet profiles are respectively located on the outer and inner wall surfaces of the flat plate.

[0039] In this embodiment, the rounded structures are respectively the first rounded structure 4 and the second rounded structure 6, and the construction method thereof is as follows:

[0040] S1: The axis of the film hole intersects with the side wall of the mainstream gas to obtain the intersection point O;

[0041] S2: Draw a rectangle 5 with a length of W and a width of H with the intersection O as the center;

[0042] S3: rounding the upper left and lower left vertices of rectangle 5 corresponding to the upstream of the incoming flow direction, with a rounding radius of R1, to obtain rounding 5;

[0043] S4: rounding the upper right and lower right vertices of rectangle 5 corresponding to the downstream of the incoming flow direction, with a rounding radius of R2, to obtain rounding 6.

[0044] The calculation formula for the equivalent diameter D of the inlet profile 3 is:

[0045]

[0046] In this embodiment, the flat slit-shaped air film holes are arranged on the flat plate model 8, the equivalent diameter D is 10 mm, the hole axis length L is 3D, the lateral spacing P of adjacent holes is 4D, the flow direction inclination angle α of the flat slit-shaped air film holes is 30 degrees, and the spanwise inclination angle β is not set. The cooling gas 7 flows through the flat slit-shaped air film holes of the present invention and is ejected, forming an air film covering the surface of the flat plate 8, and is mixed with the high-temperature mainstream 9 and finally dissipated.

[0047] The transverse hole spacing between a group of air film holes and adjacent air film holes is P, and the transverse hole spacing is a ratio of P to an equivalent diameter D ≥3.

[0048] The width H is 0.2D to 1.8D, the radius R1 is 0.5 to 0.8H, and R1+R2=H. When the width H<minor axis b, the special-shaped section 2 contracts along the flow direction and is a flat convergent slit-shaped hole; when the width H=minor axis b, the special-shaped section 2 neither expands nor contracts along the flow direction; when the width H>minor axis b, the special-shaped section 2 expands along the flow direction and is a flat expansion slit-shaped hole.

[0049] In order to verify the effectiveness of the present invention, under the same outlet width and equivalent diameter, two types of flat film cooling, the flat slit film hole in this embodiment and the classic convergent slit hole, were used to perform numerical simulations on the wall cooling efficiency within the range of 40D downstream. The operating conditions used in the numerical simulation are: mainstream aperture Reynolds number ReD = 10000, mainstream turbulence Tu = 1%, cold air to mainstream density ratio DR = 1.5, blowing ratio M = 1.0. The calculation process uses UG modeling, FluentMeshing generates unstructured grids, and the CFX solver is used for solving. The calculated film cooling efficiencies are as follows: Figure 6 to Figure 13 as shown.

[0050] Figure 6 The distribution of spanwise average film cooling efficiency of the flat slit hole in this embodiment is compared with that of the classic convergent slit hole with the same outlet profile 1 and the same equivalent diameter D within the range of 40D downstream of the film hole. The horizontal axis represents the distance in the flow direction, and the vertical axis represents the spanwise average film cooling efficiency. It can be seen that the flat slit hole in this embodiment has a higher spanwise average film cooling efficiency in the downstream area where X / D>3, and the film cooling efficiency is improved by about 20% compared with the classic convergent slit hole. This fully demonstrates the effectiveness and superiority of this patent.

[0051] Figure 7 The centerline film cooling efficiency distribution of the flat slit hole in this embodiment is compared with the classic convergent slit hole with the same outlet profile 1 and the same equivalent diameter D within the range of 40D in the downstream flow direction of the film hole. The horizontal axis represents the distance in the flow direction, and the vertical axis represents the centerline film cooling efficiency. It can be seen that due to the elimination of the kidney vortex pair near the centerline, the cold air jet of the flat slit hole in this embodiment has a better wall adhesion effect near the centerline, and thus has a higher centerline film cooling efficiency in the downstream area of ​​X / D<15. It fully illustrates the effectiveness and superiority of this patent.

[0052] Figure 8 , Fig. 9respectively show the distributions of the film cooling efficiency in the spanwise direction at the downstream flow distances of 10D and 20D from the film holes for the flat slot-shaped holes in this embodiment and the classical convergent slot-shaped holes with the same exit profile 1 and the same equivalent diameter D. The abscissa represents the distance in the spanwise direction, and the ordinate represents the film cooling efficiency. It can be seen that, compared with the traditional convergent slot-shaped holes, the flat slot-shaped holes in this embodiment have higher film cooling efficiency in the central region of -1.5 < Y / D < 1.5. In addition, the cooling efficiency distribution of the traditional convergent slot-shaped holes along the spanwise direction has three peak values, while the flat slot-shaped holes in this embodiment eliminate the kidney vortex pair at the centerline, thus eliminating the peak value of the cooling efficiency at the centerline and making the distribution of the cooling efficiency along the spanwise direction more uniform. This fully demonstrates the effectiveness and superiority of this patent.

[0053] Fig.10 show the streamwise vorticity contour and velocity vector diagram of the flat slot-shaped holes in this embodiment at the downstream flow distance of 5D plane, Fig.11 show the streamwise vorticity contour and velocity vector diagram of the classical convergent slot-shaped holes with the same exit profile 1 and the same equivalent diameter D at the downstream flow distance of 5D plane. It can be clearly observed that, in addition to the anti-kidney vortices on both sides, a pair of kidney vortices are formed near the centerline for the traditional convergent slot-shaped holes, while there are no kidney vortices near the centerline for the flat slot-shaped holes in this embodiment. This fully demonstrates the effectiveness and superiority of this patent.

[0054] Fig.12 show the cold efficiency contour of the flat slot-shaped holes in this embodiment within the downstream 40D range, Fig.13 show the cold efficiency contour of the classical convergent slot-shaped holes with the same exit profile 1 and the same equivalent diameter D within the downstream 40D range. It can be clearly observed that, due to the elimination of the kidney vortex pair near the centerline, the cold air attachment effect near the centerline is good for the flat slot-shaped holes in this embodiment, and the cooling efficiency is significantly improved. This fully demonstrates the effectiveness and superiority of this patent.

[0055] Thus, the flat slot-shaped film cooling holes provided by the present invention are based on the traditional convergent slot-shaped hole structure. By changing the inlet profile to a flat ellipse, the spacing of the kidney vortices in the hole caused by inlet separation is increased, thereby suppressing the development of the kidney vortices in the hole and eliminating the kidney vortex pair existing near the centerline of the traditional convergent slot-shaped holes from the source. The advantage of the construction method of the flat slot-shaped special-shaped section is that the size relationship between the short axis b of the inlet profile 3 and the width H of the rectangle 5 of the exit profile 1 can be adjusted to control the degree of expansion or contraction of the special-shaped section along the flow direction: when b > H, the flat slot-shaped hole contracts along the flow direction. At this time, the hole profile can inherit the advantages of the traditional convergent slot-shaped hole, improve the cold air jet velocity, reduce the aerodynamic mixing loss, and suppress the separation in the hole; when b < H, the flat slot-shaped hole expands along the flow direction. At this time, the hole profile is biased towards the traditional dustpan-shaped film hole and is easy to process and manufacture.

[0056] The flat slit-shaped air film cooling hole provided by the present invention can effectively eliminate the kidney-shaped vortex pair near the center line of the traditional flat slit-shaped hole, enhance the air film wall attachment effect near the center line downstream of the wake, thereby improving the air film cooling efficiency near the center line, while improving the temperature uniformity along the span direction, reducing the wall temperature gradient and thus reducing thermal stress.

[0057] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A flat slit-shaped film hole cooling structure applied to a hot end component of a gas turbine, comprising a film hole, characterized in that: The air film hole is composed of a special-shaped segment (2) that expands in the span direction and contracts or slightly expands in the flow direction. The special-shaped segment (2) is a ruled surface composed of an inlet profile (3) and an outlet profile (1). The inlet profile (3) is an ellipse, and the ellipse has a major axis a and a minor axis b. The outlet profile (1) is a rectangle (5), and a rounded structure is provided on the outlet profile (1).

2. The flat slit-shaped film hole cooling structure applied to the hot end component of a gas turbine according to claim 1, characterized in that: The calculation formula of the equivalent diameter D of the inlet profile (3) is:

3. The flat slit-shaped film hole cooling structure applied to the hot end component of a gas turbine according to claim 2, characterized in that: The flow direction inclination angle α of the air film hole is 30 to 90°, and the span direction inclination angle β of the air film hole is 30 to 150°.

4. The flat slit-shaped film hole cooling structure applied to the hot end component of a gas turbine according to claim 2, characterized in that: The transverse hole spacing between a group of the air film holes and its adjacent air film holes is P, and the transverse hole spacing is a ratio of P to an equivalent diameter D ≥3.

5. The flat slit-shaped film hole cooling structure applied to the hot end component of a gas turbine according to claim 2, characterized in that: The short axis b is located in the mainstream direction, the long axis a>equivalent diameter D, and the short axis b<D / sinα.

6. The flat slit-shaped film hole cooling structure applied to the hot end component of a gas turbine according to claim 1, characterized in that: The rounded structures are respectively a first rounded structure (4) and a second rounded structure (6), and the construction method thereof is as follows: S1: The axis of the film hole intersects with the side wall of the mainstream gas to obtain the intersection point O; S2: Draw a rectangle with a length of W and a width of H with the intersection point O as the center (5); S3: rounding the upper left and lower left vertices of rectangle (5) corresponding to the upstream of the incoming flow direction, with a rounding radius of R1, to obtain rounding (5); S4: rounding the upper right and lower right vertices of rectangle (5) corresponding to the downstream of the incoming flow direction, with a rounding radius of R2, to obtain rounding (6).

7. The flat slit-shaped film hole cooling structure applied to the hot end component of a gas turbine according to claim 6, characterized in that: The width H is 0.2D to 1.8D, the radius R1 is 0.5 to 0.8H, and R1+R2=H.

8. The flat slit-shaped film hole cooling structure applied to the hot end component of a gas turbine according to claim 6, characterized in that: When the width H is less than the minor axis b, the special-shaped section (2) contracts along the flow direction and becomes a flat convergent slit-shaped hole; when the width H is equal to the minor axis b, the special-shaped section (2) neither expands nor contracts along the flow direction; when the width H is greater than the minor axis b, the special-shaped section (2) expands along the flow direction and becomes a flat expansion slit-shaped hole.

Images