Disclosure of Invention
Aiming at the defects of the existing horizontal exhaust tail edge split seam cooling technology, the broken line type exhaust split seam structure of the tail edge of the turbine blade is provided, and the broken line type exhaust split seam structure of the tail edge of the turbine blade is designed to be the broken line type exhaust structure, so that the turning angle of cooling gas can be effectively reduced, the flow resistance and loss are reduced, the covering area of a gas film is increased, the temperature level of the blade is reduced, the load resistance of the structure is improved, and the casting technology performance of the blade is improved.
The technical scheme of the invention is as follows:
a broken-line exhaust split structure of the tail edge of a turbine blade comprises a hollow turbine blade, an inner cavity cold air channel, a tail edge exhaust split channel and a tail edge split partition rib;
the hollow turbine blade is internally provided with an inner cavity cold air channel for low-temperature cooling gas to flow inside the blade to cool the blade. The tail edges of the hollow turbine blades are provided with tail edge slit partition ribs which are arranged side by side, and tail edge exhaust slit channels are formed among the tail edge slit partition ribs which are arranged side by side so as to exhaust cooling air out of the blades and simultaneously carry out air film covering cooling on the tail edges of the blades. The structure of the tail edge slot partition rib can increase the heat exchange area in the blade, and guide the cooling air in the inner cavity of the blade to make the flowing direction of the cooling air turn.
The structure of the tail edge slit partition rib forms a broken line shape, the shape of the broken line shape is controlled by a partition rib central line, the partition rib central line is formed by connecting at least two line segments with different angles, at least one segment of the partition rib is inclined relative to the horizontal plane, and the width of the tail edge slit partition rib is symmetrically distributed along the partition rib central line. The included angles of the connected inclined line segments and the horizontal plane at the cold air inlet end and the cold air outlet end of the hollow turbine blade are an incident angle A1 and an emergent angle A2 respectively, the relationship of the two angles is angle A1 and angle A2, and the included angle between the flow direction of cold air after entering the tail edge splitting seam and the flow direction before entering the tail edge splitting seam, namely the cold air turning angle A, is less than 90 degrees.
Further, the incident angle a1 can be 15-45 °, the emergent angle a2 can be 0-30 °, and the cold air turning angle a is 90 ° — a1 at this time.
In the original structure, as shown in fig. 1, the center line of the partition rib is a horizontal straight line, the inlet/outlet angles & lt a1 and & lt a2 of the cold air in the tail edge splitting seam are both 0 °, at the moment, the turning angle & lt a of the cold air is about 90 °, the turning angle is too large, the flow loss is large, the air film coverage area is small, and the strength damage is large. In the scheme of the invention, after the center line of the partition rib is an inclined broken line, the air inlet angle A1 of the cold air in the tail edge splitting seam is an acute angle, the turning angle of the cold air is correspondingly changed into the acute angle, and for the broken line type channel, the cold air is changed into twice or multiple times of turning from the original one time of turning, the turning angle of each time is smaller, the flow resistance and loss are greatly reduced, and simultaneously, the better air film covering effect and the load resistance of the tail edge hollow structure are achieved.
The principle of the invention is as follows:
the inclined broken line type structure of the invention reduces the flow resistance and loss of the cold air in the inner cavity of the blade:
compared with the original horizontal exhaust tail edge slot structure, the invention has the beneficial effects that the cold air flow resistance and loss are reduced. For the horizontal exhaust tail edge slot structure, the cooling gas needs to complete 90-degree direction turning at high speed in a narrow space, and such flow can form approximate step flow on the leeward side of the end part of the partition rib to generate low-speed vortex, as shown in fig. 3, the vortex flow not only generates energy dissipation due to the strong friction thereof, but also extrudes the main flow to force the main flow to generate additional direction turning and energy loss. The driving of the cold air flow needs to extract energy from the whole engine, so the high resistance flow can increase the power consumption of the whole engine, thereby reducing the efficiency. When the partition ribs of the split seam are changed into an inclined broken line type structure from the horizontal state, the turning angle of the cooling gas in the split seam is changed into an acute angle from an approximate right angle, and the numerical value is reduced by more than 35%. And the cooling gas needs to be bent twice or more in the broken line type channel, and compared with the method of completing the bending once, the angle of each bending is smaller. Under the same flow, because the turning flow becomes more moderate, especially the leeward side of the partition rib does not form obvious steps any more, the vortex can not be formed, the flow becomes smooth, the flow resistance and loss are reduced, and the whole efficiency of the engine is improved.
2, the inclined broken line type structure improves the gas film covering effect of the tail edge area of the blade:
after the cooling gas is discharged through the tail edge cleft seam, a gas film covering can be formed on the tail edge structure of the blade, and the heating of the gas on the basin side of the blade is isolated. For a horizontal exhaust tail edge split seam, the cold air outflow direction is approximately parallel to the fuel gas, and the cold air cannot deflect in the radial direction under the entrainment of the fuel gas, so that the width covered by the air film of a single split seam is approximately the same as the actual width of the split seam. And the rib area between two adjacent clefts can hardly be covered by the air film, and the area which can not be covered by the air film is called as an air film covering dead area, wherein the cooling effect is poor, and high-temperature ablation is easily caused. For the inclined broken line type exhaust tail edge crack, the gas film outflow direction and the gas flowing direction form a certain included angle, and the angle can be approximately considered as & lt A2. Because of the entrainment effect of the gas on the gas film outflow, the cold air has the tendency of deflecting in the flowing direction and gradually becoming parallel to the flowing direction of the gas, thereby realizing the covering of partial partition rib areas, and greatly increasing the covering width of the actual gas film outflow relative to the width of the slit, as shown in fig. 4. Even can make the original air film between two adjacent cleft seams cover "dead zone" and be eliminated completely through optimal design, form the air film and to the whole covers of blade trailing edge, reduce the temperature level of blade under the condition of not increasing the air conditioning quantity to realize the improvement of engine security under the prerequisite of guaranteeing economic nature.
3, the inclined broken line type structure improves the load resistance of the hollow structure at the tail edge of the blade:
the turbine blades are subjected in operation mainly to the following loads: centrifugal loads caused by high-speed rotation, aerodynamic loads exerted by the gas flow, vibratory loads due to vibrations, which exert a tendency to deform in tension, torsion and bending on the blade base body and to generate corresponding stresses, and thermal stresses due to thermal expansion non-uniformities. These stresses couple together and act on the component alternately over time, and after exceeding the limits that the material can withstand, failure can occur. The blade design requires the use of a minimum of materials optimized to withstand these loads, avoiding the presence of high stress areas and damage to the blade. The tail edge crack structure is a vulnerable area with higher stress level in the turbine blade, the vulnerable area is firstly positioned at the thinnest part in the blade profile, and the hollow structure of the crack greatly weakens the strength, so that stress concentration can be generated at the opening of the crack. As shown in fig. 5(b), the stress level of the tail edge split structure shows a periodic law along the leaf height direction under the action of the radial tensile load, and shows a peak of the stress at the split opening and a trough at the partition rib. For a horizontal exhaust tail edge split, the periodicity is more pronounced and the peak value is higher because of the high degree of hollowing of the material at the tail edge, lack of effective support and reinforcement at the cross-sectional location shown in fig. 5 (a). When the inclined broken line type exhaust tail edge slit structure is adopted, as shown in fig. 5(c), the partition rib structure can be connected with the two sides of the basin back of the blade at any section position, so that the tail edge structure is strengthened, the stress level is improved, the load resistance of the structure is improved, and the safety and the reliability of the whole machine are improved. As can be seen from a comparison of the stress distribution along the blade height of the trailing edge shown in FIG. 5(b), the peak stress of the oblique broken line exhaust trailing edge cleft structure is significantly less than that of the horizontal exhaust pattern.
4, the inclined broken line type structure improves the blade casting manufacturability:
the turbine blade is a part with higher manufacturing cost, usually adopts zero-allowance precision casting, has lower qualification rate, and particularly needs to adopt a directional solidification process for a monocrystalline turbine blade (the molten metal is crystallized into a crystal grain during solidification, and has better mechanical property at high temperature and gas corrosion resistance compared with a polycrystalline blade), namely the molten metal is gradually cooled to a solidification state from bottom to top. Since the volume of the metal is reduced from liquid to solid, the liquid metal must be ensured to have better fluidity in the casting shell during the structural design and the corresponding manufacturing process design of the blade, and the liquid metal can be timely supplemented to the space generated after solidification shrinkage, which is called feeding. If the feeding path of the molten metal is blocked and the feeding is insufficient, dense fine holes are generated when the molten metal in the corresponding region is solidified, which is called a loosening phenomenon. The looseness can cause the mechanical property of the material and the load resistance of the blade to be greatly reduced, belongs to a serious quality problem and must be scrapped. For the horizontal exhaust tail edge slot structure, as shown in the left side of fig. 6, because the liquid-solid interface of metal can take a slightly downward concave shape because the temperature of the outer side of the blade is lower than that of the inner side, a part of feeding paths of the rib structure can be blocked, so that the horizontal rib structure is easy to cause a loosening problem, and the blade has poor casting manufacturability. For the oblique broken line type exhaust tail edge slot splitting structure, as shown in the right side of fig. 6, the rib separating structure forms a certain included angle with the liquid-solid boundary, and the oblique rib separating structure just forms a molten metal feeding channel, so that the generation of looseness is avoided, and the casting manufacturability of the blade is improved.
The invention has the beneficial effects that:
the invention provides a turbine blade broken line type exhaust tail edge split seam cooling structure, which reduces the turning angle of cooling air in a split seam by designing the tail edge exhaust split seam into inclined broken line type exhaust, and changes the cold air from one turning to two or more turning, thereby reducing the cold air flow resistance and loss of the blade inner cavity and reducing the flow resistance by about 19%. Utilize the carminative gas film of slope broken line formula to flow out direction and gas air current direction and become certain contained angle, make the gas go out to the gas film and have the parcel and hold the effect and improve blade tail edge district gas film covering effect, can make the heat transfer reinforcing about 10%. The load-resisting capacity of the hollow structure of the blade tail edge is improved by designing the partition ribs into an inclined broken line type structure, and compared with a horizontal exhaust tail edge split seam cooling structure, the load-resisting capacity of the blade tail edge structure can be improved by about 20%. In addition, the inclined rib structures can form molten metal feeding channels, so that the blade casting manufacturability is improved, and the casting yield can be improved by about 14%.
Detailed Description
In order that the present invention may be more readily and clearly understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments that are illustrated in the appended drawings.
Example 1
Referring to fig. 2, a turbine blade trailing edge broken line type exhaust cleft joint structure includes a hollow turbine blade 1, an inner cavity cold air channel 2, a trailing edge exhaust cleft joint channel 3 and a trailing edge cleft joint partition rib 4;
an inner cavity cold air channel 2 is arranged in the hollow turbine blade 1, tail edge split joint partition ribs 4 which are arranged side by side are arranged at the tail edge of the hollow turbine blade 1, a tail edge exhaust split joint channel 3 is formed between the tail edge split joint partition ribs 4 which are arranged side by side, the structure of each tail edge split joint partition rib 4 is in a broken line shape, the shape of each broken line is controlled by a partition rib central line 5, the partition rib central line 5 is formed by connecting at least two line segments with different angles, at least one section of each partition rib is inclined relative to the horizontal plane, and the width of each tail edge split joint partition rib 4 is symmetrically distributed along the partition rib central line 5; the included angles between the cold air inlet end and the cold air outlet end of the hollow turbine blade 1 and the horizontal plane of the connected inclined line segments are an incident angle A1 and an emergent angle A2 respectively. The relation between the incident angle & lt A1 and the emergent angle & lt A2 is & lt A1 & gt 2. Typical values may be ≦ a1 ≦ 40 ° and ≦ a2 ≦ 30 °, in which case the cold gas turning angle ≦ a is about 50 °.
Example 2
Referring to fig. 2, a turbine blade trailing edge broken line type exhaust cleft joint structure includes a hollow turbine blade 1, an inner cavity cold air channel 2, a trailing edge exhaust cleft joint channel 3 and a trailing edge cleft joint partition rib 4;
an inner cavity cold air channel 2 is arranged in the hollow turbine blade 1, tail edge split joint partition ribs 4 which are arranged side by side are arranged at the tail edge of the hollow turbine blade 1, a tail edge exhaust split joint channel 3 is formed between the tail edge split joint partition ribs 4 which are arranged side by side, the structure of each tail edge split joint partition rib 4 is in a broken line shape, the shape of each broken line is controlled by a partition rib central line 5, the partition rib central line 5 is formed by connecting at least two line segments with different angles, at least one section of each partition rib is inclined relative to the horizontal plane, and the width of each tail edge split joint partition rib 4 is symmetrically distributed along the partition rib central line 5; the included angles between the cold air inlet end and the cold air outlet end of the hollow turbine blade 1 and the horizontal plane of the connected inclined line segments are an incident angle A1 and an emergent angle A2 respectively. The relation between the incident angle & lt A1 and the emergent angle & lt A2 is & lt A1 & gt 2. Typical values may be ═ a1 ═ 45 ° and ═ a2 ═ 0 °, at which time the cold gas turning angle ═ a is 45 °.
Example 3
Referring to fig. 2, a turbine blade trailing edge broken line type exhaust cleft joint structure includes a hollow turbine blade 1, an inner cavity cold air channel 2, a trailing edge exhaust cleft joint channel 3 and a trailing edge cleft joint partition rib 4;
an inner cavity cold air channel 2 is arranged in the hollow turbine blade 1, tail edge split joint partition ribs 4 which are arranged side by side are arranged at the tail edge of the hollow turbine blade 1, a tail edge exhaust split joint channel 3 is formed between the tail edge split joint partition ribs 4 which are arranged side by side, the structure of each tail edge split joint partition rib 4 is in a broken line shape, the shape of each broken line is controlled by a partition rib central line 5, the partition rib central line 5 is formed by connecting at least two line segments with different angles, at least one section of each partition rib is inclined relative to the horizontal plane, and the width of each tail edge split joint partition rib 4 is symmetrically distributed along the partition rib central line 5; the included angles between the cold air inlet end and the cold air outlet end of the hollow turbine blade 1 and the horizontal plane of the connected inclined line segments are an incident angle A1 and an emergent angle A2 respectively. The relation between the incident angle & lt A1 and the emergent angle & lt A2 is & lt A1 & gt 2. Typical values may be ═ a1 ═ 15 ° and ═ a2 ═ 10 °, at which time the cold gas turning angle ═ a is 75 °.