Turbine blade inner cavity particle deposition prevention bionic shark placoid scale structure applied to micro-channel cooling

Abstract

The invention provides a turbine blade inner cavity particle deposition prevention bionic shark placoid scale structure applied to micro-channel cooling, and belongs to the field of turbulent flow structures. The problems of how to improve the flow heat exchange characteristic of the micro pipeline of the turbine blade to the maximum extent and how to reduce the influence caused by particle deposition are solved. A plurality of bionic shark placoid scale turbulent flow structures are installed on a bottom plate in the middle of the interior of the micro-fine pipeline, the bionic shark placoid scale turbulent flow structures are turbulent flow structures in a channel and are arranged in a staggered mode from the bottom of the micro-fine channel 20 mm away from an inlet, the arrangement length is 20 mm, the cross section of the bottom face of each bionic shark placoid scale turbulent flow structure is a rectangle of 1 mm * 1 mm, the maximum height is 0.6 mm, and the cross section of the bottom face of each bionic shark placoid scale turbulent flow structure is a rectangle of 1 mm * 1 mm. And an included angle of 24.6 degrees is kept between the upper surface and the bottom surface. According to the invention, along with the increase of the air flow at the inlet of the pipeline, larger particles have higher energy, are not easy to deposit due to energy loss caused by collision, and are easier to blow away due to higher flowing speed.

Description

Technical Field

[0001] The invention belongs to the field of spoiler structures, and in particular relates to a bionic shark shield scale structure for preventing particle deposition in the inner cavity of a turbine blade used for micro-channel cooling. Background Art

[0002] For aircraft engines and gas turbines that serve for a long time in all weather and all domains, there are areas in the turbine blades that are difficult to cool, especially the end walls and blade tops with relatively small dimensions and relatively complex flows, which are more likely to form cooling "blind spots" or even "dead spots". The metal temperature at these locations is close to the heat resistance limit of single crystal alloys. In addition, impurities such as sand and dust particles, volcanic ash or salt mist aerosols in the environment are mixed in the air and enter the engine through the air inlet, deposit in the cooling channel inside the blades, and gradually form a certain deposition morphology. The deposition of particles will not only affect the aerodynamic efficiency of the turbine blades, but also change their heat transfer performance, and even directly affect the service life of the turbine blades. Therefore, in order to ensure the safe and reliable operation of the turbine blades under high heat load conditions, it is necessary to design a suitable structure to enhance heat exchange, and at the same time, it should be avoided that a large amount of particles are deposited on the structure to affect the pipeline flow and heat exchange characteristics.

[0003] Relevant researchers have found that the heat transfer performance of the channel under the same Reynolds number increases with the smaller diameter. The arrangement of numerous tiny cooling channels (100μm to 1mm) close to the gas side on the inner wall of the turbine blade improves the heat transfer coefficient on the one hand, and increases the surface area for heat transfer on the other hand, greatly improving the cooling performance of the tiny channels and making the blade cooling more uniform, thereby significantly improving the thermal stress caused by uneven heat transfer in large-scale cooling methods and improving the reliability and service life of the turbine blades.

[0004] Common spoiler structures on the inner cooling channel of traditional turbine blades include ribs (straight ribs, oblique ribs, V-ribs, etc.), pits, etc. However, due to the small size of the micro-channel, the spoiler structure should be arranged to suppress the deposition of particles in the channel, prevent the particles from being deposited in large quantities in the micro-channel or even blocked, and affect the flow and heat transfer characteristics of the pipeline. Therefore, without increasing the flow of cold air, it is of great significance to design a spoiler structure with a certain flow and heat transfer capacity and suppress particle deposition for the safe and stable operation of the blade. Summary of the invention In view of this, in order to maximize the flow and heat transfer characteristics of the microchannels of turbine blades while reducing the influence of particle deposition, the present invention proposes a biomimetic shark dermal denticle structure with anti-particle deposition and arranges it in the microchannels of turbine blades. This structure is simplified and designed by referring to the scale morphology of sharks in nature. Compared with a smooth surface, when the cooling gas flows through the channel with the biomimetic structure, it can effectively increase the contact area between the fluid and it, and at the same time can break the flow and heat transfer boundary layers, promoting the mixing of hot and cold fluids. At the same time, the reduction of the area of the effective flow region increases the local velocity gradient of the flow field, increases the magnitude of the local wall shear stress, and makes it easier for particles to peel off the wall, which helps to inhibit particle deposition.

[0005] To achieve the above object, the present invention adopts the following technical solutions: A biomimetic shark dermal denticle structure for preventing particle deposition in the inner cavity of a turbine blade applied to microchannel cooling. A number of biomimetic shark dermal denticle turbulator structures are installed on the middle bottom plate inside the microchannel. The biomimetic shark dermal denticle turbulator structure is a turbulator structure in the channel, which is arranged in a staggered arrangement from the bottom of the microchannel 20 mm away from the inlet, and the arrangement length is 20 mm. The bottom surface cross-section of the biomimetic shark dermal denticle turbulator structure is a rectangle of 1 mm × 1 mm, and the maximum height is 0.6 mm. The upper surface forms an angle of 24.6° with the bottom surface.

[0006] Furthermore, the biomimetic shark dermal denticle turbulator structures are distributed in parallel along two side lengths, and the distance between each structure is 0.35 mm.

[0007] Furthermore, the biomimetic shark dermal denticle turbulator structure is manufactured by 3D printing.

[0008] A microchannel, on the inner bottom surface of the microchannel, a number of biomimetic shark dermal denticle turbulator structures are installed.

[0009] Furthermore, the microchannel is a rectangular pipe, the width of the pipe inlet and outlet is 9.5 mm, the height is 3.0 mm, the equivalent diameter D h = 4.56 mm, and the length of the channel is 60 mm.

[0010] Furthermore, the inlet of the microchannel is dry air, the temperature is 700 K, and the pressure is 2 MPa.

[0011] Furthermore, the surrounding wall surfaces of the microchannel are all non-slip isothermal wall surfaces, and the wall temperature T W = 900 K.

[0012] A turbine blade with a biomimetic shark dermal denticle structure, including a number of the above microchannels.

[0013] Compared with the prior art, the beneficial effects of the bionic shark placoid scale structure for preventing particle deposition in the inner cavity of a turbine blade applied to microchannel cooling of the present invention are as follows: 1. The present invention provides a bionic placoid scale structure with the ability to prevent particle deposition. The arrangement of this structure can increase the fluid disturbance in the pipeline. When the gas flows through the area where the placoid scale structure is arranged, the air velocity gradient above the bionic structure increases, and a recirculation vortex is generated behind the bionic structure, causing the air flow near the placoid scale structure to be lifted, enabling the particles to obtain a relatively large velocity in the flow field. When the particles are located in the area between the placoid scale structures, they will be carried by the recirculation vortex to the area with a relatively large flow velocity above and then be carried forward continuously.

[0014] 2. As the air flow rate at the pipeline inlet increases in the present invention, the larger particles have higher energy and are not easily deposited due to energy loss caused by collisions. At the same time, the flow velocity is relatively large, making it easier to blow the particles away. This structure can be manufactured by 3D printing and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 Schematic diagram of the microchannel part of a turbine blade with a bionic placoid scale structure for preventing particle deposition according to the present invention; Figure 2 Schematic diagram of the microchannel with the bionic placoid scale structure arranged according to the present invention; Figure 3 Numerical simulation boundary conditions of the microchannel according to the present invention; Figure 4 Local deposition rate contour maps of particles with different particle sizes in two channels at Re = 3000 obtained by numerical simulation according to the present invention; Figure 5 Overall deposition rate results of particles with different particle sizes in two channels at Re = 3000 obtained by numerical simulation according to the present invention; Figure 6 Velocity contour map and streamline map in the channel with the bionic placoid scale structure arranged obtained by numerical simulation according to the present invention; Figure 7 Local deposition rate contour maps of particles in two channels at different inlet Reynolds numbers obtained by numerical simulation according to the present invention; Figure 8 Overall deposition rate results of particles in two channels at different inlet Reynolds numbers obtained by numerical simulation according to the present invention.

[0016] In the figure: 1 - cold air inlet section, 2 - biomimetic shark dermal denticle flow disturbance structure, 3 - cold air outlet section, 4 - air flow outlet, 5 - air flow inlet, 7 - blade body, 8 - shroud. Detailed implementation mode

[0017] The following will clearly and completely elaborate on the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0018] See Figure 1-8 Describing this embodiment, a biomimetic shark dermal denticle structure for preventing particle deposition in the inner cavity of a turbine blade applied to microchannel cooling, and a biomimetic shark dermal denticle flow disturbance structure 2 is installed on the middle bottom plate inside the microchannel. The microchannel is a rectangular pipe, the width of the pipe inlet and outlet is 9.5 mm, the height is 3.0 mm, and the equivalent diameter D at the inlet h = 4.56 mm, and the length of the channel is 60 mm.

[0019] The inlet of the microchannel is dry air, with a temperature of 700 K and a pressure of 2 MPa.

[0020] All the surrounding walls of the microchannel are non-slip isothermal walls, and the wall temperature T W = 900 K.

[0021] A turbine blade with a biomimetic shark dermal denticle structure includes several of the above microchannels.

[0022] The working principle of the present invention is as follows: A large number of biomimetic shark dermal denticle structures 2 are arranged on the channel wall. The cooling gas enters the microchannel with the biomimetic structure from the cold air inlet of the cold air inlet section 1. After flowing through the biomimetic shark dermal denticle structure 2, it separates at the front edge thereof: the central air flow continues to flow backward along the upper surface of the biomimetic structure, and the air flows on both sides flow backward along the side edges of the biomimetic shark dermal denticle structure 2. The disturbance of the biomimetic structure in the rear to the flow field causes a local recirculation zone in this area. The air flow is lifted in the channel, and the local velocity gradient is increased, and the boundary layer is thinned. Therefore, there is a strong horizontal shear motion on the upper surface of the biomimetic structure, enabling the particles to obtain a relatively high relative velocity in the flow field, being easily peeled off from the wall by the air flow, and being carried forward by the air flow along the flow direction.

[0023] The biomimetic shark dermal denticle flow disturbance structure 2 is manufactured by 3D printing.

[0024] The microchannel is a rectangular pipe, the width of the pipe inlet and outlet is 9.5 mm, the height is 3.0 mm, and the equivalent diameter D at the inlet h= 4.56 mm, and the length of the channel is 60 mm.

[0025] The bionic shark dermal denticle structure 2 is a flow disturbance structure in the channel, which is arranged in a staggered pattern at the bottom of the microchannel 20 mm away from the inlet, and the arrangement length is 20 mm.

[0026] The bottom surface cross-section of the bionic shark dermal denticle structure 2 is a rectangle of 1 mm × 1 mm, the maximum height is 0.6 mm, the upper surface forms an angle of 24.6° with the bottom surface, and the shark dermal denticle structures are distributed parallel to the two side lengths, and the spacing between each structure is 0.35 mm.

[0027] In order to study the flow and heat transfer characteristics in the microchannel when the engine works in a special working environment (sand dust particles, volcanic ash or salt mist aerosol), the present invention designs a flow disturbance structure for suppressing particle deposition and conducts research on the dilute-phase gas-solid two-phase flow characteristics in the microchannel based on such a structure. In this case, the CFD-DPM method is used to solve the flow field distribution and particle deposition law in the microchannel. The fluid phase is simulated and solved based on the Reynolds-averaged method for flow characteristics, and the trajectory tracking of the particle phase is solved using the discrete phase model (DPM) based on the Lagrangian method. The DPM model can consider the force on the particles at different positions in the flow field and establish the motion equation according to the law of conservation of momentum, so as to realize the tracking of the particle motion trajectory. The momentum equation of the particles considers the drag force, Saffman lift force, pressure gradient force, thermophoretic force and gravity, and the turbulent diffusion effect of the particles is simulated by the random walk model.

[0028] The momentum equation of the particles can be expressed as follows:

[0029] In the formula: m p —Particle mass; —Particle motion velocity; t —Particle motion time; —Drag force; —Gravity; —Thermophoretic force; —Pressure gradient force; —Saffman lift force.

[0030] Existing research has found that some structures in nature can make the passing objects move along the path of least resistance. Sharks can effectively control the spatio-temporal structure of the external flow field through various ways such as the overall streamline structure, flexible deformation of fins, wave-like oscillation, and body surface scales, so that the fluid generates a recirculation vortex in the surface area, enhancing the shear action of the wall on the particulate matter, having excellent self-cleaning ability, making various impurities more easily carried away by the fluid and not easily deposited and grown on its body surface.

[0031] In this embodiment, the cold air flow direction separates at the front edge when flowing through the biomimetic shark dermal denticle flow disturbance structure 2, as Figure 6 can be seen: The cooling gas enters the microchannel with the biomimetic structure arranged from the inlet. After flowing through the biomimetic shark dermal denticle structure, it separates at its front edge: the central air flow continues to flow backward along the upper surface of the biomimetic structure, and the air flows on both sides flow backward along the side edges of the biomimetic dermal denticle structure. The disturbance of the rear biomimetic structure to the flow field causes a local recirculation zone to be generated in this area. This causes the air flow to rise in the channel, increases the local velocity gradient, and thins the boundary layer. Therefore, there is a strong horizontal shear motion on the upper surface of the biomimetic structure, enabling particles to obtain a relatively high relative velocity in the flow field, being easily stripped from the wall surface by the air flow, and being carried forward by the air flow along the flow direction. Since the particulate matter with a smaller particle size (1 μm) has better fluidity and a lower collision probability with the wall surface, it is not easy to deposit; on the contrary, the particles with a diameter greater than 5 μm have a larger inertia and it is difficult to flow with the air to the recirculation zone behind the biomimetic structure, and it is difficult for them to deposit in the recirculation zone.

[0032] Compare Figure 4 and Figure 5 It is found that for particles with a smaller particle size, their deposition rate in the channel with the dermal denticle structure arranged is significantly decreased compared with the original smooth channel. When the particle sizes are 1 μm and 5 μm, the channel deposition rates are decreased by 6.79% and 14.3% respectively based on the smooth channel. Under each working condition, there is no obvious particle deposition near the biomimetic structure in the channel with the dermal denticle structure arranged, and the particles are deposited in the smooth area.

[0033] In addition, change the flow rate of the cold air inlet to increase the inlet Reynolds number of the gas. According to Figure 7 and Figure 8 it can be seen: For particles with a diameter of 10 μm, as the inlet velocity increases, the particles will obtain a greater initial kinetic energy and it is still difficult to deposit even after multiple collisions, and the particle deposition rates in both channels will decrease. When Re = 5000, the particle deposition rate in the biomimetic channel is decreased by 5.3% compared with the smooth channel.

[0034] The embodiments of the present invention disclosed above are only used to help explain the present invention. The embodiments do not describe all the details in detail, nor limit the invention to the specific embodiments described. According to the content of this specification, many modifications and variations can be made. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention.

Claims

1. A biomimetic shark dermal denticle structure for preventing particle deposition in the inner cavity of a turbine blade applied to microchannel cooling, characterized in that: Several bionic shark dermal denticle turbulators (2) are installed on the inner middle bottom plate of the microchannel. The bionic shark dermal denticle turbulator (2) is a turbulator structure in the channel, which is arranged in a staggered row from the bottom of the microchannel 20 mm away from the inlet, and the arrangement length is 20 mm. The bottom surface section of the bionic shark dermal denticle turbulator (2) is a rectangle with a size of 1 mm×1 mm, the maximum height is 0.6 mm, and the upper surface forms an angle of 24.6° with the bottom surface.

2. The biomimetic shark dermal denticle structure applied to the inner cavity of the turbine blade for microchannel cooling according to claim 1, wherein: The bionic shark dermal denticle turbulators (2) are distributed parallel to two side lengths, and the distance between each structure is 0.35 mm.

3. The bionic shark dermal denticle structure applied to the inner cavity of the turbine blade for microchannel cooling according to claim 1, wherein: The bionic shark dermal denticle turbulator (2) is manufactured by 3D printing.

4. A microchannel, characterized in that: Several bionic shark dermal denticle turbulators (2) as described in claim 1 are installed on the inner bottom surface of the microchannel.

5. The microchannel according to claim 4, characterized in that: The microchannel is a rectangular pipe. The width of the pipe inlet and outlet is 9.5 mm, the height is 3.0 mm, and the equivalent diameter D h at the inlet is 4.56 mm. The length of the channel is 60 mm.

6. The microchannel according to claim 3, wherein: The inlet of the microchannel is dry air with a temperature of 700 K and a pressure of 2 MPa.

7. The microchannel according to claim 3, wherein: The four surrounding walls of the microchannel are all non-slip isothermal walls, and the wall temperature T W = 900 K.

8. A turbine blade with a bionic shark dermal denticle structure, characterized in that: It includes several microchannels as described in any one of claims 4-7.

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