Grid structure for improving outlet airflow of C-shaped air inlet channel and grid arrangement method
The non-uniform grille structure in C-shaped air inlet ducts addresses the issue of total pressure loss and swirl distortion by varying grid density and diameter, enhancing airflow stability and reducing pressure loss for aircraft engines.
Patent Information
- Application Number
- CN202411375019.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-30
- Publication Date
- 2024-12-10
AI Technical Summary
Conventional grille structures in C-shaped air inlet ducts of aircraft engines cause significant total pressure loss due to their uniform design, which does not account for the specific flow characteristics and result in large swirl angles, affecting the stability of downstream equipment like axial flow compressors.
A non-uniform grille structure with varying diameters and distributions is designed for the C-shaped air inlet duct, featuring sparse, core, and dense areas, with specific grid shapes and orientations to minimize total pressure loss while meeting swirl angle requirements.
The non-uniform grille structure effectively reduces total pressure loss and swirl angle, ensuring stable airflow for downstream equipment by optimizing grid density and diameter based on numerical simulations.
Smart Images
Figure CN119102887A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of aircraft engine air inlet ducts, and in particular relates to a grille structure and a grille arrangement method for improving airflow at a C-shaped air inlet duct outlet. Background Art
[0002] In the C-shaped inlet of an aircraft engine, due to the large deflection of the airflow direction, the deflection process will generate a pressure gradient pointing to the center of the deflection direction to balance the centrifugal force generated by the deflection of the airflow direction. When the airflow velocity in the boundary layer is too small, the effect of the pressure gradient is much greater than its centrifugal force. Therefore, under the action of this pressure gradient, a non-zero velocity component will be generated at the outlet section of the inlet, that is, the airflow is no longer perpendicular to the outlet section. The angle between the airflow velocity direction and the outlet section is the swirl angle. When the swirl angle is large, it is swirl distortion. And swirl distortion will also have an important impact on the stability of the engine (especially the axial flow compressor).
[0003] Grille structures are usually used to guide turbulent airflow and make the airflow velocity direction parallel to the grille grid flow direction, while reducing turbulence and swirl angle. They are usually used in engine intakes, wind tunnel entrances, hydroelectric generators and other equipment or spaces that need to guide fluid flow characteristics and make the fluid uniform and in the same direction. However, since the grille structure guides the flow direction by passing the fluid through small grids, the grille structure will cause flow losses, which is reflected in the airflow characteristics, that is, the total pressure of the airflow before and after the grille will be reduced. Conventional grille structures are usually composed of identical regular polygonal grids such as regular triangles, squares, regular hexagons, etc., which are tightly and evenly distributed. They are not specifically designed for the specific flow characteristics in front of the grille, resulting in a large total pressure loss through the grille. Summary of the invention
[0004] The present invention aims to design the flow characteristics peculiar to a C-shaped air inlet structure in a targeted manner, and to reduce the total pressure loss as much as possible on the basis of meeting the swirl angle requirements of the equipment downstream of the air inlet.
[0005] The present invention is achieved by the following technical solutions:
[0006] A grille structure for improving the airflow at the outlet of a C-shaped air inlet duct. The grille 01 has different diameters and is in a non-uniform distribution state. It is divided into a sparse area 11, a core area 12 and a dense area 13. The diameters of the sparse area 11, the core area 12 and the dense area 13 decrease successively. The sparse area 11 corresponds to the outer side 31 of the C-shaped air inlet duct, the dense area 13 corresponds to the inner side 32 of the C-shaped air inlet duct, and the core area 12 is in the central area of the C-shaped air inlet duct.
[0007] Furthermore, after the airflow passes through the grille, the swirl angle is reduced to the maximum grille diameter required at the outlet of the air inlet, that is, the grille diameter of the grille dense area 13 .
[0008] Furthermore, the height of the dense area 13 occupies 1 / 6 to 1 / 4 of the entire intake duct diameter, the height of the sparse area 11 occupies 1 / 5 to 1 / 3 of the entire intake duct diameter, and the other area is the core area 12.
[0009] Furthermore, the grid diameter of the core region 12 is 1.2-1.5 times that of the grid diameter of the non-uniform grid dense region 13 , and the grid diameter of the sparse region 11 is 1.5-2 times that of the grid diameter of the dense region 13 .
[0010] Furthermore, the grid shape is a triangle, a quadrilateral, a pentagon or a hexagon.
[0011] A grille arrangement method for improving the airflow at the outlet of a C-shaped air inlet duct, wherein the distance from the grille 01 to the outlet 22 of the C-shaped air inlet duct is 1.5 to 2.5 times the diameter of the straight-through section 04 of the C-shaped air inlet duct.
[0012] Furthermore, the grille 01 is installed between the upstream and downstream of the C-shaped air inlet straight section 04 through a flange.
[0013] Furthermore, the metal sheet is welded to the corresponding position in the middle of the C-shaped air inlet straight section 04 according to the grid structure.
[0014] Furthermore, a slot is reserved on the wall of the C-shaped air inlet straight-through section 04, and the grid-like structure is installed in the slot.
[0015] Furthermore, all grid channels are in the same direction and parallel to the normal direction of the C-shaped inlet duct straight-through section 04 inlet duct cross section.
[0016] The non-uniform grid structure of the present invention is simple and easy to process. Through appropriate density arrangement and diameter selection, the total pressure loss can be reduced as much as possible while meeting the swirl angle requirements of the downstream equipment of the air inlet. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 Schematic diagram of the C-shaped air inlet and the non-uniform grille structure of the present invention;
[0018] Figure 2 It is a half-section diagram of the C-shaped air intake duct and a schematic diagram of the non-uniform grille structure of the present invention;
[0019] Figure 3 , Figure 4 It is a schematic diagram of the grid structure of the present invention. DETAILED DESCRIPTION
[0020] like Figure 1 , 2For a C-shaped air inlet, the airflow enters the air inlet from the C-shaped air inlet inlet entrance 21, passes through the C-shaped air inlet expansion section 02 and the C-shaped air inlet bending section 03 in sequence, and then enters the C-shaped air inlet straight section 04, and finally flows out from the C-shaped air inlet outlet 22. Therefore, the airflow direction 23 in the C-shaped air inlet forms a C shape as a whole. Due to the pressure gradient pointing to the inner side 32 of the C-shaped air inlet that maintains the curved motion of the airflow and the low velocity of the boundary layer near the wall surface of the inner side 32 of the C-shaped air inlet, the airflow direction passing through the C-shaped air inlet bending section 03 is also bent toward the inner side 32 of the C-shaped air inlet, that is, the swirl angle is not zero.
[0021] like Figure 1 , 2 In the figure, the distance from the non-uniform grille 01 to the C-shaped air inlet duct outlet 22 is 1.5 to 2.5 times the diameter of the C-shaped air inlet duct straight section 04, and the grille structure is divided into a non-uniform grille sparse area 11 with a larger grid size, a non-uniform grille core area 12 and a non-uniform grille dense area 13, wherein the non-uniform grille sparse area 11 corresponds to the outer side 31 of the C-shaped air inlet duct, the non-uniform grille dense area 13 corresponds to the inner side 32 of the C-shaped air inlet duct, and the non-uniform grille core area 12 is in the center area of the C-shaped air inlet duct.
[0022] like Figure 3 , 4 In the figure, the height of the non-uniform grille dense area 13 accounts for 1 / 6 to 1 / 4 of the entire inlet diameter, the height of the non-uniform grille sparse area 11 accounts for 1 / 5 to 1 / 3 of the entire inlet diameter, and the other area is the non-uniform grille core area 12. The shape of the grid can be a triangle, a quadrilateral, a pentagon or a hexagon. According to the numerical simulation results, the maximum grid diameter that allows the airflow to reach the swirl angle required at the inlet outlet after passing through the grille is obtained. This diameter is the grid diameter of the non-uniform grille dense area 13. The grid diameter of the non-uniform grille core area 12 is 1.2-1.5 times that of the non-uniform grille dense area 13, and the diameter of the non-uniform grille sparse area 11 is 1.5-2 times that of the non-uniform grille dense area 13.
[0023] The present invention provides a method for improving the airflow at the outlet of a C-shaped air inlet duct by arranging the position of the grille in the air inlet duct, a grille structure for reducing the swirl angle while ensuring total pressure recovery, and a method for arranging the grille in the air inlet duct.
[0024] The non-uniform grid 01 is installed in the C-shaped air inlet straight section 04 by means of a separate flange, or by directly welding a metal sheet to the wall of the C-shaped air inlet straight section 04, or by installing the grid-like structure in a slot reserved in the wall of the cylinder. All grid channels are in the same direction and parallel to the normal direction of the air inlet cross section of the C-shaped air inlet straight section 04.
[0025] The specific working method is as follows: after passing through the C-shaped air inlet bending section 03, the airflow with a swirl angle at the entrance of the C-shaped air inlet straight section 04 is guided by the non-uniform grille 01, and the speed direction will be more biased towards the normal direction of the cross section of the C-shaped air inlet outlet 22, that is, the swirl angle is reduced. After being guided by the non-uniform grille 01, the airflow flows freely through a sufficiently long straight section, and then forms a uniform airflow that satisfies the swirl angle and total pressure loss at the C-shaped air inlet outlet.
[0026] Generally, the denser the grids of the non-uniform grid 01, the smaller the swirl angle, but at the same time the flow loss will be greater. This embodiment calculates the swirl angle distribution of the C-shaped inlet straight section 04 inlet cross section based on numerical simulation, and arranges the grid distribution in such a way that the non-uniform grid 01 grids are denser in the area with larger swirl angle and sparser in the area with smaller swirl angle, and finally obtains the following Figure 2 The non-uniform grille sparse area 11 is arranged on the outer side 31 of the C-shaped air inlet, the non-uniform grille dense area 13 is arranged on the inner side 31 of the C-shaped air inlet, and the non-uniform grille core area 12 is arranged in the central area of the air inlet. This scheme can ensure that the swirl angle is reduced while taking into account smaller flow losses.
[0027] The grid size is obtained through numerical simulation results. The maximum grid diameter required to make the airflow swirl angle after passing through the grid reach the inlet outlet is the diameter of the grid of the non-uniform grid dense area 13. The grid diameter of the non-uniform grid core area 12 is 1.2-1.5 times that of the non-uniform grid dense area 13, and the diameter of the non-uniform grid core area 12 is 1.5-2 times that of the non-uniform grid dense area 13. The distance from the non-uniform grid 01 to the C-shaped inlet outlet 22 is 1.5 to 2.5 times the diameter of the C-shaped inlet straight section 04.
[0028] Advantages and positive effects of the invention:
[0029] The non-uniform grid 01 of the present invention has a simple structure and is easy to process. The non-uniform grid 01 can be installed between the upstream and downstream of the C-shaped air inlet straight section 04 through a separate flange, or the metal sheet can be directly welded to the corresponding position in the middle of the C-shaped air inlet straight section 04 according to the grid structure, or the grid-like structure can be installed in the slot reserved in the wall of the C-shaped air inlet straight section 04. The grid structure can be triangular, quadrilateral, pentagonal or hexagonal. The height of the non-uniform grid sparse area 11, the non-uniform grid core area 12 and the non-uniform grid dense area 13, as well as the grid diameter of these three areas can be changed in accordance with the swirl angle distribution at the entrance of the C-shaped air inlet straight section 04, and the grid diameter of these three areas has the function of being suitable for different C-shaped air inlet structures. Through appropriate sparse and dense arrangement and diameter selection, the total pressure loss can be minimized on the basis of meeting the swirl angle requirements of the downstream equipment of the air inlet.
[0030] The present invention has the following characteristics:
[0031] 1. Non-uniform grid structure: denser grids in areas with larger swirl angles and sparse grids in areas with smaller swirl angles are used to minimize the total pressure loss through the grid while reducing the swirl angle. The density of the grid is determined by the flow field cross-section and is not limited to a sparse outside and dense inside arrangement.
[0032] 2. Grid size: The grid size is obtained through numerical simulation results, so that the swirl angle of the airflow after passing through the grid is reduced to the maximum grid diameter required at the inlet outlet. This diameter is the grid diameter of the non-uniform grid dense area 13. The grid diameter of the non-uniform grid core area 12 is 1.2-1.5 times that of the non-uniform grid dense area 13, and the diameter of the non-uniform grid sparse area 12 is 1.5-2 times that of the non-uniform grid dense area 13. Therefore, it is not limited to a specific grid size, and here is more of a scheme for arranging the grid distribution.
[0033] 3. Length of the straight section downstream of the grille: Because the airflow out of the grille is actually cut into small areas by the grid, the uniformity of the airflow at this time is not good enough. The straight section is used to make the small airflow flow stably and comb itself evenly. Therefore, the straight section has a great influence on the uniformity of the final outlet airflow. It has been calculated here that when the distance of the outlet of the non-uniform grille-shaped air inlet is 1.5 to 2.5 times the diameter of the straight section of the C-shaped air inlet, the airflow self-drainage effect is better. However, the actual structure may be limited by the spatial structure, and the length of the straight section behind the grille may be less than or greater than the range of 1.5 to 2.5, which ultimately fails to achieve the optimal effect of this patent, but it still has a considerable improvement on the outlet airflow, so it should also be within the scope of protection of this patent.
[0034] 4. The structure of the grid is not limited to a quadrilateral, but can be a polygon such as a triangle, a quadrilateral, a hexagon, etc., because the most important influence on the diversion of airflow is the grid diameter, not the grid shape.
[0035] 5. The present invention is not limited to gases, but also has effects on fluids, but the effect is most obvious in high-speed airflow. However, the present invention can still be applied to other fluid systems, such as the inlet of a hydroelectric generator set.
Claims
1. A grille structure for improving the airflow at the outlet of a C-shaped air inlet, Its characteristics are: The grille (01) has different diameters and is in a non-uniform distribution state, and is divided into a sparse area (11), a core area (12) and a dense area (13). The diameters of the sparse area (11), the core area (12) and the dense area (13) decrease in sequence. The sparse area (11) corresponds to the outer side (31) of the C-shaped air inlet, the dense area (13) corresponds to the inner side (32) of the C-shaped air inlet, and the core area (12) is located in the center area of the C-shaped air inlet.
2. A grille structure for improving airflow at the outlet of a C-shaped air inlet according to claim 1, Its characteristics are: The maximum grid diameter required to reduce the swirl angle of the airflow after passing through the grid to the outlet of the air inlet is the grid diameter of the grid dense area (13).
3. A grille structure for improving airflow at a C-shaped air inlet outlet according to claim 1, Its characteristics are: The height of the dense area (13) accounts for 1 / 6 to 1 / 4 of the entire air inlet diameter, the height of the sparse area (11) accounts for 1 / 5 to 1 / 3 of the entire air inlet diameter, and the other area is the core area (12).
4. A grille structure for improving airflow at the outlet of a C-shaped air inlet according to claim 1, Its characteristics are: The grid diameter of the core region (12) is 1.2-1.5 times that of the grid diameter of the non-uniform grid dense region (13), and the grid diameter of the sparse region (11) is 1.5-2 times that of the grid diameter of the dense region (13).
5. A grille structure for improving airflow at the outlet of a C-shaped air inlet according to claim 1, Its characteristics are: The grid shape is triangle, quadrilateral, pentagon or hexagon.
6. A grille arrangement method for improving the airflow at the outlet of a C-shaped air inlet, Its characteristics are: The distance from the grille (01) to the C-shaped air inlet duct outlet (22) is 1.5 to 2.5 times the diameter of the C-shaped air inlet duct straight-through section (04).
7. A grille arrangement method for improving the airflow at the outlet of a C-shaped air inlet, Its characteristics are: The grille (01) is installed between the upstream and downstream of the C-shaped air inlet straight section (04) through a flange.
8. A grille arrangement method for improving the airflow at the outlet of a C-shaped air inlet. Its characteristics are: The metal sheet is welded to the corresponding position in the middle of the C-shaped air intake duct straight-through section (04) according to the grid structure.
9. A grille arrangement method for improving the airflow at the outlet of a C-shaped air inlet. Its characteristics are: A slot is reserved on the wall of the C-shaped air inlet straight-through section (04) and the grid-like structure is installed in the slot.
10. A grille arrangement method for improving the airflow at the outlet of a C-shaped air inlet. Its characteristics are: All grid channels have the same direction and are parallel to the normal direction of the inlet cross section of the C-shaped inlet straight section (04).