Casing treatment structure for weakening blade top leakage flow of small-size turbomachinery

Abstract

The invention relates to a casing treatment structure for weakening blade top leakage flow of small-size turbomachinery, and belongs to the field of turbomachinery. A groove surrounding a rotor blade by a circle is formed in the wall surface of a turbine casing corresponding to the top of the rotor blade of a turbojet engine; 90 parallel transverse protruding obstacles and a plurality of parallel circumferential longitudinal protruding obstacles are arranged in the grooves at intervals of 4 degrees and staggered to form a #-shaped grid structure, leakage flow enters the protruding obstacle areas and flows into a large space from a small space in the process that the leakage flow flows to the suction surface from the pressure surface of the blade, and due to pressure difference and inertia, the pressure is reduced, and the speed is increased, the leakage flow is reduced. Pressure energy is converted into kinetic energy; then the kinetic energy is injected into the groove at a certain angle to drive airflow in the groove to form a vortex, and in the expansion and compression process, kinetic energy is converted into heat energy to be dissipated; meanwhile, the leakage flow rubs with parts such as moving blades and casing grooves due to the viscosity of the leakage flow, so that the leakage is reduced; and more gas working media can participate in the energy conversion process, so that the efficiency of the turbine is effectively improved.

Description

Technical Field

[0001] The invention belongs to the field of impeller machinery, and in particular, relates to a casing processing structure for weakening the tip leakage flow of a small-sized impeller machinery. Background Art

[0002] Small turbojet engines are being widely used. They are widely produced due to their diverse structures and application scenarios, providing power and electricity for industrial production and people's lives. To output mechanical energy as much as possible under the same volume and thermal parameters, you only need to try your best to improve the efficiency of the turbine. The turbine converts part of the thermal energy pressure of high-temperature, high-pressure combustion gas into rotational mechanical energy through the relative rotation of the turbine rotor and the casing. The turbine rotor consists of blades, turbine shafts, turbine discs and other parts. As a high-speed rotating power component, the turbine rotor itself must be able to bear a large gas load and mass load. As an important part that converts the energy of high-temperature combustion gas into rotor mechanical energy, the blade is not only surrounded by high-temperature combustion gas when working, but also bears huge centrifugal force, aerodynamic force and vibration load, so the design of the blade shape helps to improve the efficiency of the turbojet engine.

[0003] For a turbojet engine with a larger size, due to the large size of the turbojet engine moving blades, the gap between the turbojet engine moving blades and the casing can be ignored, and there is no need to consider reducing the leakage flow to improve the efficiency of the turbojet engine. However, for a small low-pressure turbojet engine, since the gap between the moving blades and the casing is larger than that of the small turbojet engine moving blades, the leakage flow cannot be ignored. In order to improve the efficiency of the turbojet engine, there are many improvement methods, such as designing and modifying the blade shape, increasing the difficulty of leakage flow by grooving or setting convexity on the blades, or crowning the blade tops, reducing the distance between the casing and the blade tops of the turbojet engine moving blades to reduce leakage. Considering the specific background, the invention is directed to a small low-pressure turbojet engine. Due to the small size of the engine, the distance between the blades and the blade tops is too small, and the difficulty of fine machining the blades is too high. It is difficult to take operations such as crowning the blade tops. And because the relative size of the small low-pressure turbojet engine is small, that is, relative to the large turbojet engine, the leakage flow is larger than the mainstream, the relative leakage amount is larger, and the leakage flow has a greater impact on the small low-pressure turbojet engine. Therefore, a casing treatment method is proposed. By processing the outer casing of the rotor, the leading edge overflow caused by the tip leakage flow is suppressed, the interface between the mainstream and the leakage flow is moved backward, and finally the unsteady leading edge of the blade and the tip leakage flow are improved. Currently, common casing treatment structures include circumferential groove casing treatment, axial slot casing treatment and adaptive flow casing treatment. A large number of experiments have shown that there are complex flow structures such as leakage vortex, shock wave and boundary layer at the tip of the blade and their interactions. Changing the casing structure can suppress the leakage vortex and boundary layer separation at the tip of the blade. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a casing treatment structure for weakening the leakage flow at the blade tip of a small-sized impeller machine. Through the circumferential groove casing structure surrounding the moving blades, the leakage fluid in the blade tip area is blocked, and the resistance to the flow from the pressure surface to the suction surface is increased, so as to reduce the leakage flow from the pressure surface to the suction surface of the moving blades of the turbojet engine.

[0005] The present invention is implemented by the following technical solution: a casing processing structure for weakening the tip leakage flow of a small-sized impeller machine:

[0006] A groove is provided on the wall surface of the turbine casing corresponding to the top of the turbojet engine moving blade, the groove surrounds the turbojet engine moving blade, and the depth of the groove is slightly smaller than the thickness of the casing;

[0007] A plurality of parallel transverse protrusion obstructions are arranged in the groove of the casing, and the length of the transverse protrusion obstructions is consistent with the length of the groove;

[0008] A plurality of parallel longitudinal protrusion obstacles are arranged in the groove, and the transverse protrusion obstacles and the longitudinal protrusion obstacles are interlaced with each other to form a plurality of grid structures, which are distributed in a tic-tac-toe pattern to reduce leakage flow.

[0009] Furthermore, the number of the transverse protrusion obstacles is 90, and the interval between them is 4°.

[0010] A flow control method for a casing treatment structure for reducing tip leakage flow of a small-sized impeller machine:

[0011] S1, a groove surrounding the moving blade is provided on the wall of the turbine casing corresponding to the top of the moving blade of the turbojet engine, and 90 parallel transverse protrusion obstacles and a plurality of parallel circumferential longitudinal protrusion obstacles are arranged in the groove at intervals of 4°, and the two are staggered to form a tic-tac-toe grid structure;

[0012] S2, when the leakage flow flows from the pressure surface of the blade to the suction surface, it enters the raised obstacle area and flows from a smaller space into a larger space. Due to the pressure difference and inertia, the pressure decreases, the speed increases, and the pressure energy is converted into kinetic energy; then it is injected into the groove at a certain angle, driving the airflow in the groove to form a vortex. During the expansion and compression process, the kinetic energy is converted into heat energy dissipation; at the same time, due to its viscosity, the leakage flow rubs against the moving blades, casing grooves and other parts to reduce leakage.

[0013] Furthermore, in S2, the high-temperature and high-pressure gas enters the turbine, and the leakage flow flows along the axial direction of the turbojet engine blades. When the high-temperature and high-pressure gas passes through the turbojet engine blades, the blades rotate, converting part of the heat energy and pressure energy of the high-temperature and high-pressure gas into rotational mechanical work, thereby driving the compressor and other accessories to work.

[0014] Furthermore, due to the rotation of the turbojet engine blades, there are suction surfaces and pressure surfaces with different pressures on both sides of the blades. Due to the pressure difference, part of the fluid in the mainstream leaks from the pressure surface to the suction surface in the circumferential direction of the turbojet engine.

[0015] When the leakage fluid flows from the pressure surface of the blade to the suction surface, the leakage flow will enter the raised obstacle and shoot into the groove at a certain angle. The velocity direction changes, driving the airflow in the groove to form a vortex, which continuously expands and compresses, so that the kinetic energy of the leakage flow is converted into heat energy and dissipated;

[0016] Since the leakage flow itself is viscous, the leakage flow generates friction with the turbojet engine blades, casing grooves and other parts along the way when flowing from the pressure surface to the suction surface, which also reduces leakage.

[0017] Furthermore, in S2, driven by the pressure difference between the blade tip pressure surface and the suction surface of the turbine blade, the high-pressure fluid near the blade tip pressure surface will enter the circumferential groove. After the leakage flow passes through several obstacles, the remaining leakage flow enters the blade tip suction surface and is re-injected into the mainstream from the low-pressure area near the blade tip suction surface.

[0018] An electronic device comprises a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the above method when executing the computer program.

[0019] A computer-readable storage medium is used to store computer instructions, and when the computer instructions are executed by a processor, the steps of the above method are implemented.

[0020] Beneficial effects of the present invention

[0021] Because the direction of the leakage flow of the blades mainly flows from the pressure surface to the suction surface, in order to reduce the leakage from the mainstream flow, the present invention designs a structure on the casing. This structure is different from the combination of the circumferential groove casing treatment and the axial slot casing treatment. Instead, a groove is opened in a circle around the rotor blades, and then two raised obstacles in the same plane and in the vertical direction are constructed to form a tic-tac-toe structure. By adopting this tic-tac-toe structure design of the circumferential groove casing around the moving blades, when the leakage fluid flows through the casing treatment structure, the complex structure formed by the grooves and raised obstacles provides a large flow resistance, and the flow of the leakage flow is significantly reduced. This effect directly leads to an increase in the working fluid of the mainstream flow, allowing more fuel gas working fluid to participate in the energy conversion process, thereby effectively improving the efficiency of the turbine and providing reliable technical support for the performance improvement of small turbojet engines.

[0022] The special flow channel formed by the complex raised obstacle structure in the groove of the present invention increases the flow resistance of the leakage flow and further strengthens the control of the leakage flow. The fluid flowing into and out of the circumferential groove and the interface of the mainstream interacts with the leakage flow, which inhibits the leakage vortex, alleviates the blockage caused by the leakage vortex, and moves the interface between the leakage flow and the mainstream downstream of the blade channel, delaying the occurrence of leakage flow overflow near the leading edge of the blade tip. As the engine operating conditions change, the casing structure of the present invention enhances the control ability of the leakage flow, which can effectively improve the working efficiency and stability of the turbojet engine. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The figure is a structural diagram of the tic-tac-toe grooves of the casing of a small and medium-sized low-pressure turbojet engine of the present invention.

[0024] Figure 2 It is a three-dimensional diagram of the casing of a small and medium-sized low-pressure turbojet engine of the present invention.

[0025] Figure 3 The figure shows the airflow organization of the leakage flow in the tic-tac-toe groove of the casing of a small low-pressure turbojet engine.

[0026] Among them, 1-lateral raised obstacle, 2-longitudinal raised obstacle, 3-tic-tac-toe groove, 4-casing, 5-blade, 6-flow direction of leakage flow. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0029] The flow state of fluid includes convergence and divergence, and the physical properties of the two are completely different. When the fluid flow state is divergent flow, as the contact area decreases, the pressure increases along the flow direction, the flow velocity of the fluid micro-group decreases, and backflow will occur in the area of ​​expanded area, further leading to eddy current and energy loss. That is, divergent flow is difficult to maintain and more energy is required to overcome resistance. Therefore, combined with Figures 1 to 3 The present invention proposes a casing treatment structure for weakening the tip leakage flow of a small-sized impeller machine:

[0030] A groove is provided on the wall surface of the turbine casing 4 corresponding to the top of the turbojet engine moving blade, and the groove surrounds the turbojet engine moving blade. Figure 2 It can be obtained that the groove is in the yoz plane, and its groove depth is slightly less than the thickness of the receiver 4;

[0031] A plurality of parallel transverse protrusion obstacles 1 are arranged in the groove of the casing 4, and the length of the transverse protrusion obstacles 1 is consistent with the length of the groove; the number of the transverse protrusion obstacles 1 is 90, and the interval between them is 4°.

[0032] A plurality of parallel longitudinal protruding obstacles 2 are arranged in the groove, and the transverse protruding obstacles 1 and the longitudinal protruding obstacles 2 are interlaced with each other to form a plurality of grid structures, which are distributed in a tic-tac-toe pattern to reduce leakage flow.

[0033] A flow control method for a casing treatment structure for reducing tip leakage flow of a small-sized impeller machine:

[0034] S1, a groove surrounding the moving blade is provided on the wall surface of the turbine casing 4 corresponding to the top of the moving blade of the turbojet engine, and 90 parallel transverse protrusion obstacles 1 and a plurality of parallel circumferential longitudinal protrusion obstacles 2 are arranged at intervals of 4° in the groove, and the two are staggered to form a tic-tac-toe grid structure;

[0035] S2, when the leakage flow flows from the pressure surface of the blade to the suction surface, it enters the raised obstacle area and flows from a smaller space into a larger space. Due to the pressure difference and inertia, the pressure decreases, the speed increases, and the pressure energy is converted into kinetic energy; then it is injected into the groove at a certain angle, driving the airflow in the groove to form a vortex. During the expansion and compression process, the kinetic energy is converted into heat energy dissipation; at the same time, due to its viscosity, the leakage flow rubs against the moving blades, casing grooves and other parts to reduce leakage.

[0036] In S2, high-temperature and high-pressure gas enters the turbine, and the leakage flow flows in the axial direction of the turbojet engine blades 6. When the high-temperature and high-pressure gas passes through the turbojet engine blades, the blades rotate, converting part of the heat energy and pressure energy of the high-temperature and high-pressure gas into rotational mechanical work, thereby driving the compressor and other accessories to work.

[0037] As the turbojet engine blades rotate, there are suction surfaces and pressure surfaces with different pressures on both sides of the blade 5. Due to the pressure difference, part of the fluid in the mainstream leaks from the pressure surface to the suction surface in the circumferential direction of the turbojet engine.

[0038] When the leakage fluid flows from the pressure surface of the blade 5 to the suction surface, the leakage flow will enter the raised obstacle 3, and the leakage flow will flow from a smaller space to a larger space. After a process from contraction to expansion, due to the pressure difference and inertia, the leakage flow pressure decreases and the speed increases, and the pressure energy is converted into kinetic energy; it is injected into the groove at a certain angle, and the speed direction changes, driving the airflow in the groove to form a vortex, which is continuously expanded and compressed, so that the kinetic energy of the leakage flow is converted into heat energy and dissipated;

[0039] Since the leakage flow itself is viscous, the leakage flow generates friction with the turbojet engine blades, casing 4 grooves and other parts along the way when flowing from the pressure surface to the suction surface, which also reduces leakage.

[0040] In S2, driven by the pressure difference between the blade tip pressure surface and the suction surface of the turbine blade 5, the high-pressure fluid near the blade tip pressure surface will enter the circumferential groove, and after the leakage flow passes through several obstacles, the remaining leakage flow enters the blade tip suction surface and re-injects into the mainstream from the low-pressure area near the blade tip suction surface;

[0041] The outer periphery of the turbojet engine rotor blades is surrounded by a casing 4 containing circumferential grooves. The leakage fluid flows through the casing 4 processing structure due to the large resistance, which reduces the leakage flow and increases the working fluid of the mainstream flow to improve efficiency.

[0042] The above is a detailed introduction to the casing processing structure proposed by the present invention for weakening the tip leakage flow of small-sized impeller machinery, and the principles and implementation methods of the present invention are explained. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for general technicians in this field, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A casing treatment structure for reducing the tip leakage flow of a small-sized impeller machine, characterized in that: A groove is provided on the wall surface of the turbine casing (4) corresponding to the top of the turbojet engine moving blade, the groove surrounds the turbojet engine moving blade, and the depth of the groove is slightly smaller than the thickness of the casing (4); A plurality of parallel transverse protrusion obstacles (1) are arranged in the groove of the casing (4), and the length of the transverse protrusion obstacles (1) is consistent with the length of the groove; A plurality of parallel longitudinal protruding obstacles (2) are arranged in the groove, and the transverse protruding obstacles (1) and the longitudinal protruding obstacles (2) are interlaced with each other to form a plurality of grid structures, which are distributed in a tic-tac-toe pattern to reduce leakage flow.

2. The casing processing structure according to claim 1, characterized in that: The number of the transverse protrusion obstacles (1) is 90, and the interval between them is 4°.

3. A flow control method for the casing processing structure according to claim 1 or 2, characterized in that: S1, a groove surrounding the moving blade is provided on the wall surface of the turbine casing (4) corresponding to the top of the moving blade of the turbojet engine, and 90 parallel transverse protrusion obstacles (1) and a plurality of parallel circumferential longitudinal protrusion obstacles (2) are arranged in the groove at intervals of 4°, and the two are staggered to form a tic-tac-toe grid structure; S2, when the leakage flow flows from the pressure surface of the blade to the suction surface, it enters the raised obstacle area and flows from a smaller space into a larger space. Due to the pressure difference and inertia, the pressure decreases, the speed increases, and the pressure energy is converted into kinetic energy; then it is injected into the groove at a certain angle, driving the airflow in the groove to form a vortex. During the expansion and compression process, the kinetic energy is converted into heat energy dissipation; at the same time, due to its viscosity, the leakage flow rubs against the moving blades, casing grooves and other parts to reduce leakage.

4. The flow control method of the casing processing structure according to claim 3, characterized in that: In S2, the high-temperature and high-pressure gas enters the turbine, and the leakage flow flows along the axial direction of the turbojet engine blades (6). When the high-temperature and high-pressure gas passes through the turbojet engine blades, the blades rotate, converting part of the heat energy and pressure energy of the high-temperature and high-pressure gas into rotational mechanical work, thereby driving the compressor and other accessories to work.

5. The flow control method of the casing processing structure according to claim 4, characterized in that: As the turbojet engine blades rotate, there are suction surfaces and pressure surfaces with different pressures on both sides of the blades (5). Due to the pressure difference, part of the fluid in the mainstream leaks from the pressure surface to the suction surface in the circumferential direction of the turbojet engine. When the leakage fluid flows from the pressure surface of the blade (5) to the suction surface, the leakage flow enters the raised obstacle (3) and is injected into the groove at a certain angle. The velocity direction changes, driving the airflow in the groove to form a vortex, which is continuously expanded and compressed, so that the kinetic energy of the leakage flow is converted into heat energy and dissipated; Since the leakage flow itself has viscosity, the leakage flow generates friction with the turbojet engine moving blades, casing (4) grooves and other parts along the way when flowing from the pressure surface to the suction surface, which also reduces leakage.

6. The flow control method of the casing processing structure according to claim 5, characterized in that: In S2, driven by the pressure difference between the blade tip pressure surface and the suction surface of the turbine blade (5), the high-pressure fluid near the blade tip pressure surface will enter the circumferential groove, and after the leakage flow passes through several obstacles, the remaining leakage flow enters the blade tip suction surface and is re-injected into the mainstream from the low-pressure area near the blade tip suction surface.

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