Pneumatic design method of small-hub-ratio fan for vertical direct-blowing wind tunnel

Abstract

The invention discloses a pneumatic design method of a small-hub-ratio fan for a vertical direct blowing type wind tunnel, and relates to the field of design of low-speed fans for wind tunnels, and the pneumatic design method comprises the following steps: determining the pressure rise and volume flow rate of fan design, the impeller radius, the angular velocity corresponding to the highest rotating speed, the hub ratio and the radius of a rotor head cover; establishing a three-dimensional model of a fan inlet and a fan rotor head cover flow channel, and performing analog calculation to obtain the axial speed of a blade inlet of a fan rotor; giving an induction circumferential velocity CCO; the axial speed CBO of each position in the spanwise direction of a blade outlet of the fan rotor and the axial speed CSO of each position in the spanwise direction of a rotation stopping piece outlet of the fan rotor are obtained through calculation; judging whether the CBO meets conditions or not, and if not, adjusting the value of the CCO; judging whether the CSO meets conditions or not, and if not, adjusting the value of the CCO; based on the obtained CBO and CSO, specific aerodynamic parameter design of blades and rotation stopping pieces of the fan is completed; the aerodynamic efficiency of the vertical direct-blowing wind tunnel small-propeller-hub-ratio fan is improved through design improvement, and the operation power is reduced.

Description

Technical Field

[0001] The invention relates to the field of low-speed fan design for wind tunnels, and in particular to an aerodynamic design method for a fan with a small hub-propeller ratio for a vertical direct-blowing wind tunnel. Background Art

[0002] The parachuting wind tunnel can be used as a free-fall simulator to provide support for ground training for skydivers. It has the characteristics of low cost and high efficiency. The most cost-effective parachuting wind tunnel is the vertical direct-blowing wind tunnel. The fan of this wind tunnel adopts a vertical layout, and the fan's hub ratio is generally not more than 0.3, so as to save floor space and wind tunnel height. The existing small hub ratio fan design generally adopts traditional design methods, such as the variable quantity design method recorded in the practical technical manual of ventilators. This method has limited adjustment of the pressure and velocity distribution of the fan outlet. The main purpose is to meet the pressure rise and flow rate that the fan can provide. When this type of fan is used in a parachuting wind tunnel, the wind tunnel volume is small, the flow rate is small, and the operating power is not large. Manufacturers often sacrifice fan efficiency in exchange for the low investment cost and convenient transportation of mobile debugging wind tunnels, and do not strictly limit the operating power of the fan. As a result, this type of small hub ratio fan also has problems such as low aerodynamic efficiency, high operating power, and high aerodynamic noise, which has an adverse effect on the energy saving of the vertical direct-blowing wind tunnel and the training experience of trainees. Summary of the invention

[0003] The purpose of the present invention is to improve the aerodynamic efficiency of a small-hub-ratio fan of a vertical direct-blowing wind tunnel and reduce the operating power through design improvement.

[0004] To achieve the above object, the present invention provides an aerodynamic design method for a fan with a small hub-propeller ratio for a vertical direct-blowing wind tunnel, the method comprising: Step 1: Determine the fan design pressure rise and volume flow rate based on the fan's operating requirements; Step 2: Determine the fan impeller radius R based on the fan's operating space requirements; Step 3: Determine the angular velocity ω corresponding to the maximum speed of the fan; Step 4: Determine the fan hub ratio Xb, Xb≤0.3; Step 5: Determine the fan rotor cover shape as a hemisphere, and determine the fan rotor cover radius R according to the fan impeller radius R and the hub ratio Xb N ; Step 6: According to the conditions upstream of the fan inlet, a three-dimensional model of the fan inlet and the fan rotor head cover flow passage is established, and the fan rotor blade inlet axial velocity C is obtained by simulation calculation based on the three-dimensional model. BI ; Step 7: Initially set the induced circumferential velocity C CO ; Step Eight: Based on the angular velocity ω corresponding to the maximum rotational speed of the fan and the axial velocity C of the blade inlet of the fan rotor BI and the induced circumferential velocity C CO , calculate the axial velocity C at each position in the spanwise direction of the blade outlet of the fan rotor BO ; Step Nine: Based on the induced circumferential velocity C CO and the axial velocity C at each position in the spanwise direction of the blade outlet of the fan rotor BO , calculate the axial velocity C at each position in the spanwise direction of the stator vane outlet of the fan rotor SO ; Step Ten: Determine whether the axial velocity C at each position in the spanwise direction of the blade outlet of the fan rotor BO meets the first preset condition. If not, return to Step Seven and adjust the value of the induced circumferential velocity C CO using the first adjustment method; if it meets the condition, perform the subsequent steps; Step Eleven: Determine whether the axial velocity C at each position in the spanwise direction of the stator vane outlet of the fan rotor SO meets the second preset condition. If not, return to Step Seven and adjust the value of the induced circumferential velocity C CO using the second adjustment method; if it meets the condition, perform the subsequent steps; Step Twelve: Based on the obtained axial velocity C at each position in the spanwise direction of the blade outlet of the fan rotor BO and the axial velocity C at each position in the spanwise direction of the stator vane outlet of the fan rotor SO complete the specific aerodynamic parameter design of the fan blades and stator vanes.

[0005] Among them, the purpose of adjusting the axial velocity C at each position in the spanwise direction of the blade outlet by this method BO is to adjust the work distribution of the blade in the radial direction on the airflow, form different radial pressure-increasing capabilities of the blade, and adjust the axial velocity C at each position in the spanwise direction of the stator vane outlet SO, the radial swirl coefficient of the anti-rotation vane can be adjusted to further adjust the static pressure increase distribution form of the anti-rotation vane on the air flow. Although the traditional design method of small hub ratio transformation amount can adjust the radial pressurization ability of the blade and the anti-rotation vane to a certain extent, it cannot be adjusted according to requirements, and the adjustment result cannot meet the design requirements and cannot meet the quantitative axial velocity distribution form. This method can effectively reduce the axial velocity of the small hub ratio fan near the hub position, effectively increase the axial velocity of the blade tip, so as to give play to the advantages of high relative velocity of the tip air flow, high Reynolds number, and large lift-drag ratio of the blade, and then improve the efficiency of the blade tip (the rotation speed of the blade root is low, the relative velocity with the air flow is small, the Reynolds number of the blade is small, so the lift-drag ratio of the blade is small). After adjustment, the tip does more work and has high efficiency, while the root does less work, so that a greater pressure rise is exerted at the tip with high efficiency, and the pressure rise at the root with low efficiency is appropriately reduced. Under the condition of maintaining the same fan pressure rise, the fan efficiency is improved. At the same time, the difference in the installation angle from the root to the tip of the blade designed by this method is smaller than that of the traditional method, and the spanwise twist of the blade is small, which is conducive to controlling and reducing the flow separation at the root, and further improving the aerodynamic efficiency. With the improvement of the aerodynamic efficiency, the operating power will be reduced.

[0006] Further, the radius R of the fan rotor shroud N is calculated as: R N =R*Xb.

[0007] Further, the axial velocity C at the inlet of the blade of the fan rotor BI is calculated as: C BI =f(r); where r is the distance from the radial position of the blade to the center of the rotor, and f(r) is the distribution pattern of C BI along the blade radius.

[0008] Further, the induced circumferential velocity C CO is calculated as: C CO =g(r); where r is the distance from the radial position of the blade to the center of the rotor, and g(r) is the first distribution pattern of C CO along the blade radius; And C CO needs to meet the following conditions: When is ; where r M is the radial average position of the blade, ρ is the air density, η is the aerodynamic efficiency of the fan, ΔP is the designed pressure rise of the fan, and Q is the designed volume flow rate of the fan.

[0009] Further, the axial velocity C at each spanwise position at the blade outlet of the fan rotor BO is calculated as follows: ; where r is the distance from the radial position of the blade to the center of the rotor, r M is the radial average position of the blade, and dr is the radial differential distance.

[0010] Further, the axial velocity C at each spanwise position at the outlet of the anti-rotation vane of the fan rotor SO is calculated as follows: ; where r is the distance from the radial position of the blade to the center of the rotor, r M is the radial average position of the blade, and dr is the radial differential distance.

[0011] Further, the first preset condition is: The value of C BO has a positive correlation with the value of r; 1 ≤ C BO1 / C BO2 ≤ 1.2; Among them, the axial velocity at the tip is higher than that at the root, which can effectively improve the efficiency. The first preset condition needs to ensure that the axial velocity deviation at the blade outlet is not too large, and the increase difference in the spanwise direction is not too large, thereby ensuring that the static pressure gradient in the spanwise direction of the blade is not too large and avoiding excessive radial flow. Excessive radial flow will also cause uneven flow conditions at the inlet of the anti-rotation vane.

[0012] Among them, C BO1 is the value of C corresponding to r = R BO , C BO2 is the value of C corresponding to r = R N when, and r is the distance from the radial position of the blade to the center of the rotor. BO

[0013] Further, the second preset condition is: The value of C SO has a positive correlation with the value of r; 1.1 ≤ C SO1 / C SO2 ≤ 1.5; Among them, the axial velocity at the tip is higher than that at the root, which can effectively improve the efficiency. The second preset condition needs to ensure that the axial velocity deviation at the outlet of the anti-rotation vane is not too large, but at the same time, it needs to ensure the pressure boosting effect at the tip. The outlet of the anti-rotation vane is a diffuser section, and the flight section follows after the diffuser section. After the airflow is diffused, the velocity decreases. Therefore, appropriately increasing the tip velocity will obtain a relatively uniform inlet flow field for the flight section.

[0014] Among them, CSO1 The value of C corresponding to r = R SO value, C SO2 is for r = R N when the corresponding C SO value, where r is the distance of the blade radial position from the rotor center.

[0015] Furthermore, the induced circumferential velocity C is adjusted by the first adjustment method CO The specific value of adjusting the induced circumferential velocity C is to adjust the induced circumferential velocity C using the following formula CO value: C CO = g 1 (r); where g 1 (r) is the second distribution mode of C CO along the blade radius, and r is the distance of the blade radial position from the rotor center.

[0016] Furthermore, the induced circumferential velocity C is adjusted by the second adjustment method CO The specific value of adjusting the induced circumferential velocity C is to adjust the induced circumferential velocity C using the following formula CO value: C CO = g 2 (r); where g 2 (r) is the third distribution mode of C CO along the blade radius, and r is the distance of the blade radial position from the rotor center.

[0017] One or more technical solutions provided by the present invention have at least the following technical effects or advantages: In the conventional small hub ratio fan design, in order to achieve the pressure rise and flow rate indicators, the improvement of the fan aerodynamic efficiency is often not concerned. Due to the small hub ratio, the flow velocity at the blade root is low, and the airflow is more likely to cause flow field distortion at the blade root position of the small hub ratio fan, resulting in it being difficult to further improve the aerodynamic efficiency of this type of fan. Based on the structural characteristics of the small hub ratio fan and the flow characteristics of the fan flow passage, this invention obtains the actual oncoming flow characteristics by numerical simulation. Through this design method, the velocity distributions at the blade outlet and the stator vane outlet are adjusted, the axial velocity at the blade root is controlled, and a higher axial velocity is promoted at the blade tip to control the flow field distortion at the blade root of this type of fan, so as to further improve the fan aerodynamic efficiency and save the fan operating power. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of the present invention, and do not limit the embodiments of the present invention; Figure 1It is a schematic flow chart of the aerodynamic design method for a small hub ratio fan used in the vertical direct blowing wind tunnel of the present invention. Detailed implementation manners

[0019] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention will be further described in detail below in conjunction with the drawings and specific implementation manners. It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0020] In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described within the scope here. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0021] Those skilled in the art should understand that in the disclosure of the present invention, the orientation or positional relationships indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting the present invention.

[0022] It can be understood that the term "one" should be understood as "at least one" or "one or more". That is, in one embodiment, the number of one element can be one, while in other embodiments, the number of this element can be multiple. The term "one" should not be construed as a limitation on the quantity.

[0023] Please refer to Figure 1 , the present invention provides an aerodynamic design method for a small hub ratio fan used in a vertical direct blowing wind tunnel, and the method includes: Step 1: Determine the pressure rise and volume flow rate for the fan design according to the operating requirements of the fan; Step 2: Determine the radius R of the fan impeller according to the operating space requirements of the fan; Step 3: Determine the angular velocity ω corresponding to the highest rotational speed of the fan; wherein, the tip rotational speed of the fan corresponding to this angular velocity is not greater than 130 m / s, and the lower rotational speed can be reduced as much as possible; Step 4: Determine the hub ratio Xb of the fan, Xb ≤ 0.3; Step 5: Determine that the shape of the fan rotor shroud is a hemisphere, and determine the radius R of the fan rotor shroud according to the fan impeller radius R and the hub ratio Xb N ; Step 6: Based on parameters such as the distance between the fan inlet and the ground and the form of the inlet collector, use 3D structural simulation software such as NX and SOLIDWORKS to establish a 3D model of the fan inlet and the flow channel of the fan rotor head cover. Based on the 3D model, use CFD technology and the boundary conditions of pressure inlet and flow outlet to simulate and calculate to obtain the axial velocity C of the blade inlet of the fan rotor BI ; Step 7: Initially specify the induced circumferential velocity C CO ; Step 8: Based on the angular velocity ω corresponding to the maximum rotational speed of the fan, the axial velocity C of the blade inlet of the fan rotor BI and the induced circumferential velocity C CO , calculate the axial velocity C of each position in the spanwise direction at the blade outlet of the fan rotor BO ; Step 9: Based on the induced circumferential velocity C CO and the axial velocity C of each position in the spanwise direction at the blade outlet of the fan rotor BO , calculate the axial velocity C of each position in the spanwise direction at the anti-rotation vane outlet of the fan rotor SO ; Step 10: Determine whether the axial velocity C of each position in the spanwise direction at the blade outlet of the fan rotor BO meets the first preset condition. If not, return to Step 7 and adjust the value of the induced circumferential velocity C CO using the first adjustment method; if it meets the condition, proceed to the subsequent steps; Step 11: Determine whether the axial velocity C of each position in the spanwise direction at the anti-rotation vane outlet of the fan rotor SO meets the second preset condition. If not, return to Step 7 and adjust the value of the induced circumferential velocity C CO using the second adjustment method; if it meets the condition, proceed to the subsequent steps; Step 12: Based on the obtained axial velocity C of each position in the spanwise direction at the blade outlet of the fan rotor BO and the axial velocity C of each position in the spanwise direction at the anti-rotation vane outlet of the fan rotor SO , complete the specific aerodynamic parameter design of the fan blades and anti-rotation vanes.

[0024] Among them, the purpose of Design Steps 10 and 11 is that the distribution method of the induced circumferential velocity C CO needs to simultaneously meet the conditions of C BO and C SO . Among them, the specific aerodynamic parameter design of the fan blades and anti-rotation vanes may also include other conventional parameters, and other parameters can be designed and obtained by existing methods. The embodiments of the present invention do not make specific limitations and elaborations.

[0025] Among them, in the embodiments of the present invention, the radius R of the fan rotor head coverN The calculation method is as follows: R N =R*Xb.

[0026] Among them, in the embodiment of the present invention, the axial velocity C of the blade inlet of the fan rotor BI The calculation method is as follows: C BI =f(r); Among them, r is the distance from the radial position of the blade to the center of the rotor, and f(r) is the distribution mode of C BI along the radial direction of the blade. f(r) is based on Step 6: According to the conditions upstream of the fan inlet, establish a three-dimensional model of the fan inlet and the flow channel of the fan rotor head cover, and use simulation calculation based on the three-dimensional model to obtain the axial velocity C of the blade inlet of the fan rotor BI , which is the axial velocity distribution mode of the blade outlet fitted according to the simulation results. For example, the f(r) function can be ar 2 +br, where a and b are constants, which can be a linear function, a quadratic function, or a piecewise function. The embodiment of the present invention does not limit the specific function expression and type, and can be obtained according to the actual fitting results.

[0027] Among them, in the embodiment of the present invention, the induced circumferential velocity C CO The calculation method is as follows: C CO =g(r); where r is the distance from the radial position of the blade to the center of the rotor, and g(r) is the first distribution mode of C CO along the radial direction of the blade; g(r) is a function set according to the requirements (1≤C BO1 / C BO2 ≤1.2, 1.1≤CSO1 / CSO2≤1.5). The g(r) function can be: cr 2 +dr+e, where c, d, and e are constants, the form of the function can be adjusted, and it can also be a piecewise function, and its operation can be variable (linear function, quadratic function, etc.). The expression of this function is inconsistent with that of f(r). The embodiment of the present invention does not limit the specific expression and type of the g(r) function, and can be adjusted according to the actual situation; And C CO needs to meet the following conditions: When , ; Among them, r M is the radial average position of the blade, ρ is the air density, η is the aerodynamic efficiency of the fan, ΔP is the pressure rise designed by the fan, and Q is the volume flow designed by the fan.

[0028] Among them, in the embodiments of the present invention, the axial velocity C at each position in the spanwise direction of the blade outlet of the fan rotor BO is calculated as follows: ; where r is the distance from the radial position of the blade to the center of the rotor, r M is the average radial position of the blade, and dr is the radial differential distance.

[0029] Among them, in the embodiments of the present invention, the axial velocity C at each position in the spanwise direction of the anti-rotation vane outlet of the fan rotor SO is calculated as follows: ; where r is the distance from the radial position of the blade to the center of the rotor, r M is the average radial position of the blade, and dr is the radial differential distance.

[0030] Among them, in the embodiments of the present invention, the first preset condition is: The value of C BO has a positive correlation with the value of r; 1 ≤ C BO1 / C BO2 ≤ 1.2; where C BO1 is the value of C corresponding to r = R BO , C BO2 is the value of C corresponding to r = R N when, and r is the distance from the radial position of the blade to the center of the rotor. BO

[0031] Among them, in the embodiments of the present invention, the second preset condition is: The value of C SO has a positive correlation with the value of r; 1.1 ≤ C SO1 / C SO2 ≤ 1.5; where C SO1 is the value of C corresponding to r = R SO , C SO2 is the value of C corresponding to r = R N when, and r is the distance from the radial position of the blade to the center of the rotor. SO

[0032] Among them, in the embodiments of the present invention, adjusting the induced circumferential velocity C CO specifically means adjusting the induced circumferential velocity C CO using the following formula: C CO = g 1 (r); Among them, g 1 (r) is C CO The second distribution along the blade radial direction, such as g 1 (r) = cr 2 +dr+e, c, d and e are constants. The embodiment of the present invention does not limit the specific function expression and type, which can be obtained according to the actual fitting result, and r is the distance between the radial position of the blade and the center of the rotor.

[0033] Among them, in the embodiment of the present invention, the second adjustment method is used to adjust the induced circumferential velocity C CO The value of the induced circumferential velocity C is specifically adjusted using the following formula CO Values: C CO =g 2 (r); Among them, g 2 (r) is C CO The third distribution mode along the blade radial direction, such as g 2 (r) = cr 2 +hr+j, c, h and j are constants. The embodiment of the present invention does not limit the specific function expression and type, which can be obtained according to the actual fitting result, and r is the distance between the radial position of the blade and the center of the rotor.

[0034] The following is an introduction to this method with specific data: Step 1: According to the fan's operating requirements, determine the fan's designed pressure rise ΔP=2300Pa and volume flow rate Q=330m 3 s -1 ; Step 2: Determine the fan's impeller radius R=1.25m based on the fan's operating space requirements; Step 3: Determine the angular velocity ω corresponding to the maximum speed of the fan = 125.66 rad / s; Step 4: Determine the fan hub ratio Xb, Xb=0.25; Step 5: Determine the fan rotor hood shape as a hemispherical shape. Determine the fan rotor hood radius R based on the fan impeller radius R=1.25 and the hub ratio Xb=0.25. N , R N =1.25*0.25=0.3125m; Step 6: According to the conditions upstream of the fan inlet, a three-dimensional model of the fan inlet and the fan rotor head cover flow passage is established, and the fan rotor blade inlet axial velocity C is calculated using CFD technology. BI , C BI =f(r)=-3.2r+71.71, r is the distance between the radial position of the blade and the center of the rotor; Step 7: Initially specify the induced circumferential velocity C CO , C CO = g(r), when C CO should satisfy ; where the air density ρ = 1.15 kg / m 3 , η is the fan aerodynamic efficiency, η = 75%; Step 8: Determine the axial velocity C BO at the blade outlet of the fan rotor: ; Based on the specified C CO = g(r), the calculated data for C BO are: C BO (r = 0.3125) = 63.02 m / s, C BO (r = 0.375) = 63.55 m / s, C BO (r = 0.5) = 65.54 m / s, C BO (r = 0.625) = 67.82 m / s, C BO (r = 0.75) = 69.82 m / s, C BO (r = 0.875) = 71.31 m / s, C BO (r = 1) = 71.57 m / s, C BO (r = 1.125) = 72.15 m / s, C BO (r = 1.25) = 72.25 m / s.

[0035] Step 9: Determine the axial velocity C SO at the outlet of the anti-rotation vane of the fan rotor: ; The calculated data for C SO are: C SO (r = 0.3125) = 51.74 m / s, C SO (r = 0.375) = 55.49 m / s, C SO (r = 0.5) = 61.51 m / s, C SO (r = 0.625) = 65.97 m / s, C SO (r = 0.75) = 69.18 m / s, C SO (r = 0.875) = 71.28 m / s, C SO (r = 1) = 71.93 m / s, C SO (r = 1.125) = 72.46 m / s, C SO (r = 1.25) = 72.66 m / s.

[0036] Step Ten: According to Step Eight, calculate the axial velocity C at each position in the spanwise direction at the blade outlet. BO , and determine whether C BO increases with r and satisfies 1 ≤ C BO1 / C BO2 ≤ 1.2; C BO1 / C BO2 = 1.15 ≤ 1.2; no adjustment to C is required. CO .

[0037] Step Eleven: After determining the axial velocity at the blade outlet through Step Ten, calculate the axial velocity C at each position in the spanwise direction at the anti-rotation vane outlet according to Step Nine. SO , and determine whether C SO increases with r and 1.1 ≤ C SO1 / C SO2 ≤ 1.5, C SO1 / C SO2 = 1.4 ≤ 1.5, and no adjustment to C is required either. CO .

[0038] Step Twelve: After determining C BO at the blade outlet of the fan and the axial velocity C SO at the anti-rotation vane outlet, the specific aerodynamic parameter design of the blades and anti-rotation vanes of the fan can be completed according to the axial flow fan design theory.

[0039] The feature of this method is that on the basis of meeting the basic aerodynamic performance of the fan, by adjusting the axial velocity distribution at the blade outlet and the anti-rotation vane, the aerodynamic efficiency of the fan is further improved. When designing a conventional small hub ratio fan, in order to achieve the pressure rise and flow rate indicators, the improvement of the fan aerodynamic efficiency is often not emphasized. Due to the small hub ratio, the flow velocity at the blade root is low, and the airflow is more likely to cause flow field distortion at the blade root position of the small hub ratio fan, resulting in it being difficult to further improve the aerodynamic efficiency of this type of fan. Based on the structural characteristics of the small hub ratio fan and the flow characteristics of the fan flow channel, this invention obtains the actual oncoming flow characteristics through numerical simulation. Through this design method, after adjusting the velocity distribution at the blade outlet and the anti-rotation vane outlet, the axial velocity at the blade root is effectively controlled, enabling the blade tip to obtain a higher axial velocity, so as to control the flow field distortion at the blade root of this type of fan and further improve the aerodynamic efficiency of the fan and save the fan operating power.

[0040] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concept. Therefore, the appended claims are intended to be interpreted to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0041] Obviously, those skilled in the art can make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. An aerodynamic design method for a small hub-to-propeller ratio fan for a vertical direct-blowing wind tunnel, characterized in that: The method comprises: Step 1: Determine the fan design pressure rise and volume flow rate based on the fan's operating requirements; Step 2: Determine the fan impeller radius R based on the fan's operating space requirements; Step 3: Determine the angular velocity ω corresponding to the maximum speed of the fan; Step 4: Determine the fan hub ratio Xb, Xb≤0.3; Step 5: Determine the fan rotor cover shape as a hemisphere, and determine the fan rotor cover radius R according to the fan impeller radius R and the hub ratio Xb N ; Step 6: According to the conditions upstream of the fan inlet, a three-dimensional model of the fan inlet and the fan rotor head cover flow passage is established, and the blade inlet axial velocity C of the fan rotor is obtained by simulation calculation based on the three-dimensional model. BI ; Step 7: Initially set the induced circumferential velocity C CO ; Step 8: Based on the angular velocity ω corresponding to the maximum speed of the fan and the axial velocity C of the blade inlet of the fan rotor BI and the induced circumferential velocity C CO , calculate the axial velocity C of the fan rotor blade outlet at each position BO ; Step 9: Based on the induced circumferential velocity C CO and the axial velocity C of the fan rotor at each position of the blade outlet span BO , calculate the axial velocity C of the fan rotor at each position of the anti-rotation plate outlet SO ; Step 10: Determine the axial velocity C of the fan rotor blade outlet at each position BO Whether the first preset condition is met, if not, return to step 7 and use the first adjustment method to adjust the induced circumferential velocity C CO If the value is satisfied, the subsequent steps are executed; Step 11: Determine the axial velocity C of the fan rotor at each position of the anti-rotation plate outlet SO Whether the second preset condition is met, if not, return to step 7 and use the second adjustment method to adjust the induced circumferential velocity C CO If the value is satisfied, the subsequent steps are executed; Step 12: Based on the obtained axial velocity C of the fan rotor blade outlet at each position BO and the axial velocity C of the fan rotor at each position of the anti-rotation plate outlet SO Complete the specific aerodynamic parameter design of the fan blades and anti-rotation plates.

2. The aerodynamic design method of a fan with a small propeller-hub ratio for a vertical direct-blowing wind tunnel according to claim 1, characterized in that: The radius R of the fan rotor shroud N The calculation method is: R N =R*Xb。 3. The aerodynamic design method of a fan with a small propeller-hub ratio for a vertical direct-blowing wind tunnel according to claim 1, characterized in that: The fan rotor blade inlet axial speed C BI The calculation method is: C BI =f(r); Where r is the distance between the blade radial position and the rotor center, and f(r) is C BI The distribution pattern along the radial direction of the blade.

4. The aerodynamic design method of a fan with a small propeller-hub ratio for a vertical direct-blowing wind tunnel according to claim 1, characterized in that: Induced circumferential velocity C CO The calculation method is: C CO =g(r); where r is the distance between the blade radial position and the rotor center, and g(r) is C CO A first distribution mode along the radial direction of the blade; And C CO The following conditions must be met: when hour, ; Among them, r M is the average radial position of the blade, ρ is the air density, η is the aerodynamic efficiency of the fan, ΔP is the designed pressure rise of the fan, and Q is the designed volume flow rate of the fan.

5. The aerodynamic design method of a fan with a small hub-propeller ratio for a vertical direct-blowing wind tunnel according to claim 1, characterized in that: The axial velocity C of the fan rotor at each position of the blade outlet span BO The calculation method is: ； Where r is the distance between the blade radial position and the rotor center, r M is the radial average position of the blade, and dr is the radial infinitesimal distance.

6. The aerodynamic design method of a fan with a small hub-propeller ratio for a vertical direct-blowing wind tunnel according to claim 1, characterized in that: The axial velocity C of the fan rotor at each position of the anti-rotation plate outlet SO The calculation method is: ； Where r is the distance between the blade radial position and the rotor center, r M is the radial average position of the blade, and dr is the radial infinitesimal distance.

7. The aerodynamic design method of a fan with a small hub-propeller ratio for a vertical direct-blowing wind tunnel according to claim 1, characterized in that: The first precondition is: C BO The value of is positively correlated with the value of r; 1≤C BO1 / C BO2 ≤1.2; Among them, C BO1 The corresponding C when r=R BO The value of C BO2 For r=R N The corresponding C BO The value of r is the distance between the radial position of the blade and the center of the rotor.

8. The aerodynamic design method of a fan with a small propeller-hub ratio for a vertical direct-blowing wind tunnel according to claim 1, characterized in that: The second precondition is: C SO The value of is positively correlated with the value of r; 1.1≤C SO1 / C SO2 ≤1.5; Among them, C SO1 The corresponding C when r=R SO The value of C SO2 For r=R N The corresponding C SO The value of r is the distance between the radial position of the blade and the center of the rotor.

9. The aerodynamic design method of a fan with a small hub-propeller ratio for a vertical direct-blowing wind tunnel according to claim 1, characterized in that: Use the first adjustment method to adjust the induced circumferential velocity C CO The value of the induced circumferential velocity C is specifically adjusted using the following formula CO Values: C CO =g1(r); Where g1(r) is C CO In the second distribution mode along the radial direction of the blade, r is the distance between the radial position of the blade and the center of the rotor.

10. The aerodynamic design method of a fan with a small propeller-hub ratio for a vertical direct-blowing wind tunnel according to claim 1, characterized in that: Use the second adjustment method to adjust the induced circumferential velocity C CO The value of the induced circumferential velocity C is specifically adjusted using the following formula CO Values: C CO =g2(r); Where g2(r) is C CO The third distribution mode along the radial direction of the blade, r is the distance between the radial position of the blade and the center of the rotor.

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