Aerodynamic Design Method for a Small Hub Ratio Fan Used in a Vertical Direct Blow Wind Tunnel

Abstract

The present invention discloses a pneumatic design method for a small hub ratio fan used in a vertical direct blowing wind tunnel, which relates to the field of low-speed fan design for wind tunnels, and includes: determining the pressure rise, volume flow rate, impeller radius, angular velocity corresponding to the highest rotational speed, hub ratio, and radius of the rotor cowl for the fan design; establishing a three-dimensional model of the fan inlet and the flow passage of the fan rotor cowl, and obtaining the axial velocity at the blade inlet of the fan rotor through simulation calculation; given the induced circumferential velocity C CO ; calculating to obtain the axial velocity C BO at each spanwise position at the blade outlet of the fan rotor and the axial velocity C SO at each spanwise position at the stator vane outlet of the fan rotor; judging whether C BO meets the conditions, and if not, adjusting the value of C CO ; judging whether C SO meets the conditions, and if not, adjusting the value of C CO ; based on the obtained C BO and C SO to complete the specific pneumatic parameter design of the fan blades and stator vanes; the present invention improves the pneumatic efficiency of the small hub ratio fan of the vertical direct blowing wind tunnel and reduces the operating power through design improvement.

Description

Technical Field

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

[0002] A skydiving wind tunnel can be used as a free-fall simulator to provide support for ground training of skydiving personnel, and has the characteristics of low cost and high efficiency. The most cost-effective skydiving wind tunnel is a vertical direct-blow wind tunnel. The fan of this type of wind tunnel adopts a vertical layout, and the hub ratio of the fan generally does not exceed 0.3 to save floor area and wind tunnel height. For the existing design of small hub ratio fans, traditional design methods are generally used, such as the transformation quantity design method recorded in the Practical Technology Manual of Ventilators. This method has limited effect on adjusting the pressure and velocity distribution at the fan outlet, and 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 skydiving wind tunnel, the wind tunnel has a small volume, a small flow rate, and a low operating power. Usually, manufacturers sacrifice the fan efficiency in exchange for a low investment cost and convenient transportation of the mobile debugging wind tunnel, and do not strictly limit the operating power of the fan, resulting in problems such as low aerodynamic efficiency, high operating power, and high aerodynamic noise of this type of small hub ratio fan, which has an adverse impact on energy saving of the vertical direct-blow wind tunnel and the training experience of training personnel. 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-blow wind tunnel and reduce the operating power through design improvement.

[0004] To achieve the above purpose, the present invention provides an aerodynamic design method for a small hub ratio fan used in a vertical direct-blow wind tunnel, and the method includes:

[0005] Step 1: Determine the pressure rise and volume flow rate for fan design according to the operating requirements of the fan;

[0006] Step 2: Determine the radius R of the fan impeller according to the operating space requirements of the fan;

[0007] Step 3: Determine the angular velocity ω corresponding to the highest rotational speed of the fan;

[0008] Step 4: Determine the hub ratio Xb of the fan, where Xb ≤ 0.3;

[0009] Step 5: Determine that the shape of the fan rotor cowling is a hemisphere, and determine the radius R of the fan rotor cowling according to the fan impeller radius R and the hub ratio Xb N ;

[0010] Step 6: Based on the conditions upstream of the fan inlet, establish a three-dimensional model of the fan inlet and the flow passage of the fan rotor shroud, and use simulation calculations based on the three-dimensional model to obtain the axial velocity C at the blade inlet of the fan rotor BI ;

[0011] Step 7: Initially specify the induced circumferential velocity C CO ;

[0012] Step 8: Based on the angular velocity ω corresponding to the maximum rotational speed of the fan, the axial velocity C at the blade inlet of the fan rotor BI and the induced circumferential velocity C CO , calculate the axial velocity C at each spanwise position at the blade outlet of the fan rotor BO ;

[0013] Step 9: Based on the induced circumferential velocity C CO and the axial velocity C at each spanwise position at the blade outlet of the fan rotor BO , calculate the axial velocity C at each spanwise position at the stator vane outlet of the fan rotor SO ;

[0014] Step 10: Determine whether the axial velocity C at each spanwise position 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 ; if it meets the condition, perform the subsequent steps;

[0015] Step 11: Determine whether the axial velocity C at each spanwise position at the stator 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 ; if it meets the condition, perform the subsequent steps;

[0016] Step 12: Based on the obtained axial velocity C at each spanwise position at the blade outlet of the fan rotor BO and the axial velocity C at each spanwise position at the stator vane outlet of the fan rotor SO complete the specific aerodynamic parameter design of the fan blades and stator vanes.

[0017] Among them, the purpose of adjusting the axial velocity C at each spanwise position at the blade outlet in this method BO is to adjust the work distribution of the blade in the radial direction on the air flow, form different radial pressure increasing capabilities of the blade, and adjust the axial velocity C at each spanwise position at 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. The traditional design method of small hub ratio transformation amount can, to a certain extent, adjust the radial pressurization ability of the blade and the anti-rotation vane, but 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 air flow velocity, high Reynolds number, and large blade lift-drag ratio at the blade tip, 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 blade Reynolds number is small, so the blade lift-drag ratio is small). After adjustment, the work done at the tip is large and the efficiency is high, and the work done at the root is reduced. Thus, a greater pressure rise is exerted at the high-efficiency blade tip, and the pressure rise at the low-efficiency blade root is appropriately reduced. While maintaining the same fan pressure rise, the fan efficiency is improved. At the same time, the difference in the installation angle from the blade root to the tip designed by this method is smaller than that of the traditional method, and the spanwise twist of the blade is small, which is beneficial 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.

[0018] Further, the radius R of the fan rotor shroud N is calculated as follows:

[0019] R N =R*Xb.

[0020] Further, the axial velocity C at the inlet of the blade of the fan rotor BI is calculated as follows:

[0021] C BI =f(r);

[0022] 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.

[0023] Further, the induced circumferential velocity C CO is calculated as follows:

[0024] 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;

[0025] And C CO needs to meet the following conditions:

[0026] When is, ;

[0027] where r Mis 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 for the fan, and Q is the volume flow rate designed for the fan.

[0028] Further, the axial velocity C at each spanwise position at the blade outlet of the fan rotor BO is calculated as:

[0029] ;

[0030] 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.

[0031] 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:

[0032] ;

[0033] 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.

[0034] Further, the first preset condition is:

[0035] The value of C BO has a positive correlation with the value of r;

[0036] 1 ≤ C BO1 / C BO2 ≤ 1.2;

[0037] 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 spanwise increase difference 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 anti-rotation vane inlet.

[0038] Among them, C BO1 is the value of C BO corresponding to r = R, C BO2 is the value of C N corresponding to r = R BO at that time, and r is the distance from the radial position of the blade to the center of the rotor.

[0039] Further, the second preset condition is:

[0040] The value of C SO has a positive correlation with the value of r;

[0041] 1.1 ≤ CSO1 / C SO2 ≤1.5;

[0042] Among them, the axial velocity at the blade tip is higher than that at the blade 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 is necessary to ensure the pressure increase effect at the blade tip. The outlet of the anti-rotation vane is a diffuser section, and the flight section follows the diffuser section. After the air flow is diffused, the velocity decreases. Therefore, by appropriately increasing the tip velocity, a relatively uniform inlet flow field of the flight section can be obtained.

[0043] Among them, 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, SO r is the distance from the radial position of the blade to the rotor center.

[0044] Furthermore, the first adjustment method is adopted to adjust the induced circumferential velocity C CO The specific value of is to adjust the induced circumferential velocity C CO using the following formula:

[0045] C CO = g1(r);

[0046] Among them, g1(r) is the second distribution method of C CO along the blade radius, and r is the distance from the radial position of the blade to the rotor center.

[0047] Furthermore, the second adjustment method is adopted to adjust the induced circumferential velocity C CO The specific value of is to adjust the induced circumferential velocity C CO using the following formula:

[0048] C CO = g2(r);

[0049] Among them, g2(r) is the third distribution method of C CO along the blade radius, and r is the distance from the radial position of the blade to the rotor center.

[0050] One or more technical solutions provided by the present invention have at least the following technical effects or advantages:

[0051] In a conventional small hub ratio fan design, in order to achieve the pressure rise and flow rate targets, the improvement of the fan's aerodynamic efficiency is often not concerned. Due to the small hub ratio, the flow velocity at the root of the blade is low, and the airflow is more likely to cause flow field distortion at the 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, the velocity distribution at the blade outlet and the stator vane outlet is adjusted, the axial velocity at the root of the blade is controlled, and a higher axial velocity is promoted at the tip of the blade to control the flow field distortion at the root of this type of fan and further improve the aerodynamic efficiency of the fan and save the fan operating power. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] 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 constitute a limitation to the embodiments of the present invention;

[0053] Figure 1 It is a schematic flow chart of the aerodynamic design method of the small hub ratio fan for the vertical direct blowing wind tunnel in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] In order to be able 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 embodiments. 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.

[0055] Many specific details are set forth in the following description 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 hereof. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0056] 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, and do not indicate or imply 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.

[0057] 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, and in other embodiments, the number of this element can be multiple. The term "one" should not be construed as a limitation on the number.

[0058] Please refer to Figure 1 , the present invention provides a pneumatic design method for a small hub ratio fan of a vertical direct injection wind tunnel, and the method includes:

[0059] Step 1: Determine the pressure rise and volume flow rate for the fan design according to the operating requirements of the fan;

[0060] Step 2: Determine the radius R of the fan impeller according to the operating space requirements of the fan;

[0061] 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;

[0062] Step 4: Determine the hub ratio Xb of the fan, Xb ≤ 0.3;

[0063] Step 5: Determine that the outer 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 ;

[0064] Step 6: Such as the distance between the fan inlet and the ground, the form of the inlet collector, use structural 3D simulation software, such as NX, SOLIDWORKS, etc., to establish a 3D model of the fan inlet and the flow channel of the fan rotor shroud, and based on the 3D model, adopt CFD technology, adopt the boundary conditions of pressure inlet and flow outlet, and simulate and calculate to obtain the axial velocity C at the blade inlet of the fan rotor BI ;

[0065] Step 7: Initially specify the induced circumferential velocity C CO ;

[0066] Step 8: Based on the angular velocity ω corresponding to the highest rotational speed of the fan, the axial velocity C at the blade inlet of the fan rotor BI and the induced circumferential velocity C CO , calculate and obtain the axial velocity C at each position in the spanwise direction of the blade outlet of the fan rotor BO ;

[0067] Step 9: 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 and obtain the axial velocity C at each position in the spanwise direction of the stator vane outlet of the fan rotor SO ;

[0068] Step 10: 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 7 and adjust the induced circumferential velocity C using the first adjustment method COValue; if satisfied, perform subsequent steps;

[0069] Step Eleven: Determine whether the axial velocity C at each position in the spanwise direction of the anti-rotation vane outlet of the fan rotor SO satisfies the second preset condition. If not, return to Step Seven and adjust the induced circumferential velocity C using the second adjustment method CO Value; if satisfied, perform subsequent steps;

[0070] 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 anti-rotation vane outlet of the fan rotor SO complete the specific aerodynamic parameter design of the fan blades and anti-rotation vanes.

[0071] Among them, the purpose of Design Steps Ten and Eleven is the distribution mode of the induced circumferential velocity C CO , which needs to satisfy the conditions of C BO and C SO at the same time. 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.

[0072] Among them, in the embodiments of the present invention, the radius R of the fan rotor shroud N is calculated as:

[0073] R N = R * Xb.

[0074] Among them, in the embodiments of the present invention, the axial velocity C at the blade inlet of the fan rotor BI is calculated as:

[0075] C BI = f(r);

[0076] 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 blade radius. f(r) is based on Step Six: 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 shroud, and use simulation calculation based on the three-dimensional model to obtain the axial velocity C at the blade inlet of the fan rotor BI , which is the axial velocity distribution mode at 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 embodiments of the present invention do not limit the specific function expression and type, and can be obtained according to the actual fitting results.

[0077] Among them, in the embodiments of the present invention, the induced circumferential velocity C CO is calculated as follows:

[0078] C CO = g(r); where r is the distance from the radial position of the blade to the rotor center, and g(r) is the first distribution mode of C CO along the blade radius; g(r) is a function set according to requirements (1 ≤ C BO1 / C BO2 ≤ 1.2, 1.1 ≤ CSO1 / CSO2 ≤ 1.5), and 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, or it can 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 specific expression and type of the g(r) function are not limited in the embodiments of the present invention and can be adjusted according to actual situations;

[0079] And C CO needs to meet the following conditions:

[0080] When time, ;

[0081] Among them, r M is the average radial position of the blade, ρ is the air density, η is the fan aerodynamic efficiency, ΔP is the pressure rise designed for the fan, and Q is the volume flow designed for the fan.

[0082] Among them, in the embodiments of the present invention, the axial velocity C BO at each position in the spanwise direction at the blade outlet of the fan rotor is calculated as follows:

[0083] ;

[0084] Among them, r is the distance from the radial position of the blade to the rotor center, r M is the average radial position of the blade, and dr is the radial differential distance.

[0085] Among them, in the embodiments of the present invention, the axial velocity C SO at each position in the spanwise direction at the outlet of the anti-rotation vane of the fan rotor is calculated as follows:

[0086] ;

[0087] Among them, r is the distance from the radial position of the blade to the rotor center, r M is the average radial position of the blade, and dr is the radial differential distance.

[0088] Among them, in the embodiments of the present invention, the first preset condition is:

[0089] C BO The value of C is positively correlated with the value of r;

[0090] 1 ≤ C BO1 / C BO2 ≤ 1.2;

[0091] Wherein, C BO1 is the value of C corresponding to r = R, BO C BO2 is the value of C corresponding to r = R N at this time, r is the distance of the radial position of the blade from the center of the rotor. BO BO

[0092] Wherein, in the embodiment of the present invention, the second preset condition is:

[0093] C SO The value of C is positively correlated with the value of r;

[0094] 1.1 ≤ C SO1 / C SO2 ≤ 1.5;

[0095] Wherein, C SO1 is the value of C corresponding to r = R, SO C SO2 is the value of C corresponding to r = R N at this time, r is the distance of the radial position of the blade from the center of the rotor. SO SO

[0096] Wherein, in the embodiment of the present invention, the first adjustment method is adopted to adjust the induced circumferential velocity C CO The value of C is specifically adjusted by using the following formula to adjust the induced circumferential velocity C CO value:

[0097] C CO = g1(r);

[0098] Wherein, g1(r) is the second distribution mode of C CO along the blade radius, such as g1(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, and can be obtained according to the actual fitting result. r is the distance of the radial position of the blade from the center of the rotor.

[0099] Wherein, in the embodiment of the present invention, the second adjustment method is adopted to adjust the induced circumferential velocity C CO The value of C is specifically adjusted by using the following formula to adjust the induced circumferential velocity C CO value:

[0100] C CO = g2(r);

[0101] Among them, g2(r) is the third distribution mode along the radial direction of the blade, such as g2(r)=cr CO +hr+j, where c, h, and j are constants. The embodiments of the present invention do not limit the specific function expressions and types, which can be obtained according to the actual fitting results, and r is the distance from the radial position of the blade to the center of the rotor. 2

[0102] The following is an introduction and description of this method in combination with specific data:

[0103] Step 1: According to the operating requirements of the fan, determine the pressure rise ΔP = 2300 Pa and the volume flow rate Q = 330 m 3 s -1 ;

[0104] Step 2: According to the operating space requirements of the fan, determine the impeller radius R = 1.25 m of the fan;

[0105] Step 3: Determine the angular velocity ω = 125.66 rad / s corresponding to the highest rotational speed of the fan;

[0106] Step 4: Determine the hub ratio Xb of the fan, Xb = 0.25;

[0107] Step 5: Determine that the shape of the fan rotor cowling is a hemisphere, and determine the radius R of the fan rotor cowling according to the determined fan impeller radius R = 1.25 and hub ratio Xb = 0.25 N R N = 1.25 * 0.25 = 0.3125 m;

[0108] 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 cowling, and use CFD technology to calculate and obtain the axial velocity C at the blade inlet of the fan rotor BI C BI = f(r) = -3.2r + 71.71, where r is the distance from the radial position of the blade to the center of the rotor;

[0109] Step 7: Initially specify the induced circumferential velocity C CO C CO = g(r), when C CO should satisfy, ; Among them, the air density ρ = 1.15 kg / m 3 , and η is the aerodynamic efficiency of the fan, η = 75%;

[0110] Step 8: Determine the axial velocity C at the blade outlet of the fan rotor BO : ​

[0111] ;

[0112] According to the given C CO = g(r), the calculated value of C BO is: 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.

[0113] Step Nine: Determine the axial velocity C SO at the exit of the anti-rotation vane of the fan rotor:

[0114] ;

[0115] The calculated value of C SO is: 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.

[0116] Step Ten: According to Step Eight, calculate the axial velocity C BO at each position in the spanwise direction at the exit of the blade, and judge 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 of C is required CO .

[0117] 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 outlet of the anti-rotation vane according to Step Nine SO , and judge whether C SO increases with the increase of r, and 1.1 ≤ C SO1 / C SO2 ≤ 1.5, C SO1 / C SO2 = 1.4 ≤ 1.5, and no adjustment of C is required either CO .

[0118] Step Twelve: After determining the C at the outlet of the fan blade BO and the axial velocity C at the outlet of the anti-rotation vane SO , the specific aerodynamic parameter design of the blade and the anti-rotation vane of the fan can be completed according to the axial flow fan design theory.

[0119] The characteristic 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 by 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 fan aerodynamic efficiency and save the fan operating power.

[0120] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they know the basic creative concept. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0121] Obviously, those skilled in the art can make various changes and modifications 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 also intends to include these modifications and variations.

Claims

1. An aerodynamic design method for a small hub-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 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 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 propeller-hub 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 propeller-hub 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 propeller-hub 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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