CN108583847B - Low-Reynolds-number high-power-factor wing section suitable for long-endurance unmanned aerial vehicle - Google Patents
Low-Reynolds-number high-power-factor wing section suitable for long-endurance unmanned aerial vehicle Download PDFInfo
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Abstract
The invention provides a low Reynolds number high power factor wing profile suitable for an unmanned aerial vehicle during long endurance, and discloses an equation respectively satisfied by the maximum camber and the position thereof, the maximum thickness and the position thereof, and the upper and lower surfaces of the wing profile, and a wing profile coordinate, wherein f is the maximum camber, Xf is an abscissa value of the maximum camber position of the wing profile, t is the maximum thickness, Xt is an abscissa value of the maximum thickness position of the wing profile, and C is a chord length. The origin of a coordinate system in which the airfoil is located is defined as the leading edge point of the camber line of the airfoil, the X axis is coincident with a chord line, the direction is from the leading edge of the airfoil to the trailing edge of the airfoil, and the Y axis is perpendicular to the X axis and points to the direction in which the camber line of the airfoil is bent. Through carrying out reasonable improvement to the upper and lower surface gradient distribution of wing section, postpone the forward movement bubble separation of transition point, can realize under the work reynolds number of settlement, this wing section has better performance, and bigger scope lift-drag ratio promptly, higher power factor cooperates aircraft global design, improves unmanned aerial vehicle's duration.
Description
Technical Field
The invention belongs to the technical field of wing profile design of unmanned aerial vehicles, and particularly relates to a wing profile with a low Reynolds number and a high power factor.
Background
The long-endurance unmanned aerial vehicle, such as a small-sized solar unmanned aerial vehicle and an high-altitude long-endurance unmanned aerial vehicle, has a small flying speed and a low flying reynolds number, the cruising reynolds number of the long-endurance unmanned aerial vehicle is about 20-40 ten thousand, which is mostly called as a low reynolds number (in the industry, the reynolds number of 10-100 ten thousand is called as a low reynolds number), and in the reynolds number range, the long-endurance unmanned aerial vehicle mainly relates to physical phenomena such as low reynolds number, low-speed laminar flow, laminar bubble, laminar flow separation, and transition from laminar flow to turbulent flow, and is greatly different from the flow under the flight conditions of medium and high re. Therefore, the aerodynamic design method and the concept of the long-endurance unmanned aerial vehicle are obviously different from those of the medium and high Reynolds number aircrafts. The solar unmanned aerial vehicle also needs to consider the compounding of the photovoltaic module, so the airfoil profile is also restrained.
Although some of the existing airfoil libraries can be used for low reynolds number airfoils in a low reynolds number flight state, for example, SD7032 as a comparison airfoil in the present design, under a reynolds number condition of 20 ten thousand orders, an upper airfoil transition point moves rapidly toward a leading edge along with an increase of an attack angle, so that airflow separation is caused, and performance loss is caused.
Disclosure of Invention
Aiming at the defects of the prior art and the situation that the performance of the existing low Reynolds number wing profile is poor when the existing low Reynolds number wing profile is matched with the actual work, the invention provides the low Reynolds number high-power factor wing profile which can well match the actual working condition of the low flying Reynolds number of the unmanned aerial vehicle during long voyage, and meanwhile, the upper surface bending degree is small, so that the low flying Reynolds number wing profile is suitable for matching the photovoltaic module of the solar unmanned aerial vehicle.
In order to achieve the technical purpose, the invention adopts the following technical scheme:
specific flight conditions were analyzed, such as assuming a Reynolds number of 20 tens of thousands of flights. Under the condition, firstly, the common airfoil profile with the low Reynolds number is preliminarily selected, and the performance of different airfoil profiles under the set working condition is analyzed by using the aerodynamic analysis technology of the aviation industry under the specified working condition.
Because the main performance of the wing profile depends on the shapes of the upper surface and the lower surface of the wing profile to a great extent, the wing profile with the best performance is found out by further researching a plurality of groups of wing profiles with better performance in the previous step, pertinently modifying the parameters of the radius of the front edge, the gradient distribution of the upper surface and the lower surface, the maximum camber position and the like, and is used as a design wing profile and verified by experimental verification and actual unmanned aerial vehicle test flight verification.
The pneumatic analysis mainly refers to calculating common performance parameters such as lift-drag ratio, power factor and the like of the whole aircraft adopting a specific wing profile under a set working condition.
According to the design principle, the invention specifically provides a low Reynolds number high power factor airfoil and is named as DMXfoil-1, and the specific description of the airfoil is as follows:
the ratio f/C of the maximum camber f to the chord length C of the airfoil is 3.88 percent,
the maximum camber position Xf/C of the airfoil is 48.09,
the ratio t/C of the maximum thickness t to the chord length C of the airfoil is 10.50 percent,
the maximum thickness position of the airfoil is Xt/C which is 28.99%;
defining the chord length as 1, the equation for the upper surface of the airfoil is:
y＝-2.687263401080x6+9.080382811085x5-12.119920168585x4+8.215218339892x3-3.252320013999x2+0.754048283792x+0.008814393076
when the chord length is defined as 1, the equation of the lower surface of the airfoil is as follows:
y＝3.108344757931x6-10.324958446486x5+13.345995816048x4-8.586501844602x3+2.878571621603x2-0.414971953131x-0.005291297688
wherein Xf is the abscissa value of the maximum camber position of the airfoil, and Xt is the abscissa value of the maximum thickness position of the airfoil. The origin of a coordinate system in which the airfoil is located is defined as the leading edge point of the camber line of the airfoil, the X axis is coincident with a chord line, the direction is from the leading edge of the airfoil to the trailing edge of the airfoil, and the Y axis is perpendicular to the X axis and points to the direction in which the camber line of the airfoil is bent.
When the chord length of the airfoil is 1, the coordinates corresponding to the upper surface and the lower surface of the airfoil are as follows:
upper surface coordinates:
coordinates of the lower surface:
drawings
Fig. 1 is a structural diagram of a designed airfoil, in which 1 is an airfoil leading edge, 2 is an airfoil upper surface, 3 is an airfoil lower surface, 4 is an airfoil chord line, 5 is an airfoil trailing edge, f is an airfoil maximum camber, Xf is an abscissa value of an airfoil maximum camber position, C is a chord length, t is an airfoil maximum thickness, and Xt is an abscissa value of the airfoil maximum thickness position.
FIG. 2 is a comparison of the geometric profiles of the design airfoil DMXfoil-1 and the comparison airfoil SD 7032.
Fig. 3 is a pressure distribution diagram of the design airfoil DMXfoil-1 in the design state (Re 20 ten thousand, angle of attack α 5.6 °, low speed).
Fig. 4 is a pressure distribution graph of the comparative airfoil SD7032 in the design state (Re 20 ten thousand, angle of attack α 5.6 °, low speed).
Fig. 5 is a comparison graph of lift-drag ratio characteristic curves (Re 20 ten thousand, low speed) of the design airfoil DMXfoil-1 and the comparison airfoil SD7032, where 6 is an aerodynamic characteristic curve of the design airfoil DMXfoil-1 in the design state and 7 is an aerodynamic characteristic curve of the comparison airfoil SD7032 in the design state.
Fig. 6 is a comparison graph of power factor characteristics of the design airfoil DMXfoil-1 and the comparison airfoil SD7032 in the design state, wherein 6 is an aerodynamic characteristic curve of the design airfoil DMXfoil-1 in the design state, and 7 is an aerodynamic characteristic curve of the comparison airfoil SD7032 in the design state. (Re 20 ten thousand, low speed)
Detailed Description
The invention is described in detail below with reference to the accompanying drawings:
the invention relates to a low Reynolds number high power factor wing profile suitable for an unmanned aerial vehicle during long endurance, which has the design principle that: specific flight conditions were analyzed, as in the present example, at the beginning of the analysis, i.e., assuming a Reynolds number of flight of 20W. Under the condition, the common airfoil profile with the low Reynolds number is selected preliminarily, and the performance of different airfoil profiles under the set working condition is analyzed by using the pneumatic analysis technology of the aviation industry under the specified working condition.
Because the main performance of the airfoil depends on the shapes of the upper surface and the lower surface of the airfoil to a great extent, the airfoil with the best performance is found out as a design airfoil by further researching several groups of airfoils with better performance in the previous step and pertinently modifying parameters such as the radius of the front edge, the gradient distribution of the upper surface and the lower surface, the position of the maximum camber and the like.
The pneumatic analysis mainly refers to calculating common performance parameters such as lift-drag ratio, power factor and the like of the whole aircraft adopting a specific wing profile under a set working condition.
The regular characteristic of the low reynolds number high power factor airfoil obtained by the optimization method and the distribution rules of the upper surface and the lower surface of the designed airfoil are given below, and the equation and the shape which are satisfied are given, and fig. 1 can be referred to.
According to the design principle, the invention specifically provides a low Reynolds number high power factor airfoil and is named as DMXfoil-1, and the specific description of the airfoil is as follows:
ratio of maximum camber f to chord length C of airfoil
f/C＝3.88％，
Maximum camber position of airfoil
Xf/C＝48.09，
Ratio of maximum thickness t to chord length C of airfoil
t/C＝10.50％
The maximum thickness position of the airfoil is
Xt/C＝28.99％；
Defining the chord length as 1, the equation for the upper surface of the airfoil is:
y＝-2.687263401080x6+9.080382811085x5-12.119920168585x4+8.215218339892x3-3.252320013999x2+0.754048283792x+0.008814393076
when the chord length is defined as 1, the equation of the lower surface of the airfoil is as follows:
y＝3.108344757931x6-10.324958446486x5+13.345995816048x4-8.586501844602x3+2.878571621603x2-0.414971953131x-0.005291297688
wherein Xf is the abscissa value of the maximum camber position of the airfoil, and Xt is the abscissa value of the maximum thickness position of the airfoil. The origin of a coordinate system in which the airfoil is located is defined as the leading edge point of the camber line of the airfoil, the X axis is coincident with a chord line, the direction is from the leading edge of the airfoil to the trailing edge of the airfoil, and the Y axis is perpendicular to the X axis and points to the direction in which the camber line of the airfoil is bent.
When the chord length of the airfoil is 1, the coordinates corresponding to the upper surface and the lower surface of the airfoil are as follows:
upper surface coordinates:
coordinates of the lower surface:
in order to illustrate the advancement of the airfoil of the design, a series of pneumatic calculations and experimental verification were carried out on the special and comparative airfoil SD7032, and the following results were obtained:
the reynolds number is set to 20 ten thousand, when the airfoil attack angle is 5.6 degrees, the lift-drag ratio of the airfoil DMXfoil-1 is designed to be maximum, the calculation result is 83.8, the transition point of the upper airfoil surface is about 52% chord length, and under the condition of the same reynolds number, the lift-drag ratio of the SD7032 is only 62.3, because the transition point is very close to the front edge position at the SD7032 airfoil attack angle, the energy is reduced and is not enough to be attached to the upper surface, airflow shunting is generated, the resistance is increased sharply, and the lift-drag ratio is reduced sharply.
The pressure profiles of DMXfoil-1 and SD7032 under the above conditions are shown in FIGS. 3 and 4, respectively.
In a larger angle of attack range (fig. 5), it can be readily seen that the lift-to-drag ratio characteristics of the design airfoil DMXfoil-1 are close to those of the comparison airfoil SD7032 for an angle of attack in the range of-5 ° to 3 °, and the lift-to-drag ratio of the design airfoil DMXfoil-1 is superior to that of the comparison airfoil SD7032 for an angle of attack in the range of 3 ° to 20 °.
Furthermore, for the design of the same solar unmanned aerial vehicle (the main parameters are that the wing chord is 400mm long, the wing span is 5.4m, and the rectangular wing is provided with a wing tip), the design wing DMXfoil-1 and the comparison wing SD7032 are respectively adopted to compare the power factors under the condition of set flight quality, and as shown in fig. 6, it can also be seen that the power factors of the design wing DMXfoil-1 are higher than those of the comparison wing SD7032 under the other attack angles except that the power factors are the same when the attack angle of the wing is 1 °. The cruise state is particularly concerned, namely the attack angle range is between 4 and 6 degrees, the power factor difference is obvious, and the value is closely related to the cruise power of the aircraft and directly influences the endurance time of the aircraft. Under the condition of certain flight quality, the high power factor is beneficial to reducing the cruising power, and further improving the cruising time. The unmanned aerial vehicle has obvious significance for long-endurance unmanned aerial vehicles.
Claims (2)
1. A low reynolds number high power factor airfoil, designated DMXfoil-1, wherein: the ratio f/C of the maximum camber f to the chord length C of the airfoil is 3.88 percent, the maximum camber position Xf/C is 48.09 percent, the ratio t/C of the maximum thickness t to the chord length C of the airfoil is 10.50 percent, and the maximum thickness position Xt/C is 28.99 percent;
defining the chord length as 1, the equation for the upper surface of the airfoil is:
y＝-2.687263401080x6+9.080382811085x5-12.119920168585x4+8.215218339892x3-3.252320013999x2+0.754048283792x+0.008814393076
when the chord length is defined as 1, the equation of the lower surface of the airfoil is as follows:
y＝3.108344757931x6-10.324958446486x5+13.345995816048x4-8.586501844602x3+2.878571621603x2-0.414971953131x-0.005291297688
wherein Xf is the abscissa value of the maximum camber position of the airfoil profile, Xt is the abscissa value of the maximum thickness position of the airfoil profile,
the origin of a coordinate system in which the airfoil is located is defined as the leading edge point of the camber line of the airfoil, the X axis is coincident with the chord line, the direction is from the leading edge of the airfoil to the trailing edge of the airfoil, and the Y axis is perpendicular to the X axis and points to the direction in which the camber line of the airfoil is bent.
2. A low reynolds number high power factor airfoil according to claim 1, wherein: when the chord length of the airfoil is 1, the coordinates corresponding to the upper surface and the lower surface of the airfoil are as follows:
upper surface coordinates:
coordinates of the lower surface:
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| CN110386243B (en) * | 2019-07-22 | 2024-04-16 | 北京耐威科技股份有限公司 | High lift-drag ratio low-speed unmanned wing type |
| CN110435873B (en) * | 2019-08-15 | 2021-04-23 | 西北工业大学 | A family of cruising self-trimming half-wing body fusion tailless unmanned aerial vehicle airfoils |
| CN111498084A (en) * | 2020-04-15 | 2020-08-07 | 成都飞机工业（集团）有限责任公司 | Low-resistance laminar flow airfoil applied to high-altitude high-speed long-endurance unmanned aerial vehicle |
| CN112977815B (en) * | 2021-05-10 | 2021-08-27 | 北京三快在线科技有限公司 | Rotor craft, blade of rotor craft and wing section of blade |
| CN114194373B (en) * | 2021-12-03 | 2024-02-23 | 中电科芜湖通用航空产业技术研究院有限公司 | Aircraft wing and aircraft |
| CN114718903A (en) * | 2022-04-19 | 2022-07-08 | 成都航空职业技术学院 | High-performance wing section for heat dissipation axial flow fan |
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| CN103482054B (en) * | 2013-08-14 | 2015-07-01 | 西北工业大学 | Low-Reynolds-number wing section matched with full-wing solar unmanned aerial vehicle |
| CN104354850B (en) * | 2014-10-30 | 2016-03-09 | 中国人民解放军空军航空大学 | A kind of HAE fixed wing aircraft Airfoil |
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