Novel heavy-load aircraft with stub-wing lift fuselage

Abstract

The invention discloses a novel heavy-load aircraft with a stub-wing lift fuselage. Comprising an airfoil-shaped lift fuselage, front stub wings connected to the two sides of the nose of the lift fuselage in a smooth transition mode, rear stub wings connected to the two sides of the tail of the lift fuselage in a smooth transition mode, a propeller power mechanism arranged on the nose of the lift fuselage, a V-shaped empennage arranged on the tail of the lift fuselage and a ventral fin arranged on the belly of the lift fuselage. The wingspan of the novel heavy-load stub wing lift fuselage aircraft is less than or equal to 2m, the wingspan of the front stub wing is smaller than that of the rear stub wing, and the mounting angle of the front stub wing is larger than that of the rear stub wing; after the scheme is adopted, the lift fuselage can provide large lift force, the short wings can provide a part of lift force, meanwhile, longitudinal balancing of the aircraft can be completed by adjusting the mounting angle, the static stability requirement of the aircraft is met, the performance of high-speed cruise is reserved, the wingspan of the wings is reduced, and the stability of the aircraft is improved. Therefore, the unmanned aerial vehicle has flexible performance and can be applied to narrow and complex environments.

Description

Technical Field

[0001] The invention relates to the technical field of aircraft, and in particular to a novel large-load short-wing lifting fuselage aircraft. Background Art

[0002] With the rapid development of logistics services, the use of drones for point-to-point "last mile" transportation has become a trend, which can reduce labor costs and achieve timely delivery services. The ability to quickly and flexibly transport express delivery in urban environments has become a demand, which requires a drone that has both high-speed cruising and maneuverability to achieve fast, efficient and safe delivery.

[0003] Fixed-wing drones have a large wingspan and it is difficult to achieve point-to-point flight in an environment with tall buildings in the city. Therefore, the current mainstream logistics industry is trying to use rotorcraft drones. For example, a certain autorotating rotor logistics drone is mainly used for medium and short-distance logistics transportation. It can effectively undertake the tasks of downlinking orders, uplinking high-value-added products and emergency material supply in border areas, mountainous areas, islands and other areas with inconvenient transportation at the level of hundreds of kilometers, significantly improving logistics timeliness. In addition, some companies have planned a three-stage air transport network of "large manned transport aircraft + large feeder drones + terminal small drones". At present, they have mainly developed vertical take-off and landing cargo drones that can be used in logistics transportation, emergency rescue, government applications and other aspects. The better part of the small multi-rotor drone uses a six-axis aircraft with a maximum load of 2.5 kilograms and a maximum delivery distance of 10 kilometers when fully loaded.

[0004] With the development of drone technology, drone applications are becoming more and more extensive, and mission payload requirements are becoming more complex. Currently, common drones used for express logistics transportation mainly include two categories: rotary-wing drones and compound vertical take-off and landing fixed-wing drones. Although rotary-wing drones are small in size and have the advantages of low-speed and flexibility in the air, their hovering power and forward flight power are greater than those of fixed-wing drones. The more weight they carry, the higher the power consumption. Therefore, rotary-wing drones have a short range and a short endurance, and do not support medium-distance logistics transportation. At the same time, the cruising speed of rotary-wing drones is relatively slow, and timely delivery services cannot be perfectly achieved. Compound vertical take-off and landing drones have the advantages of completing vertical take-off and landing in rotary-wing mode and cruising at high speed in fixed-wing mode, but their fixed-wing wingspan is large. Facing the complex urban environment with tall buildings, it is difficult to achieve flexible and maneuverable transportation of goods. At the same time, their large wingspan is not suitable for special narrow space environments.

[0005] In view of the above-mentioned drawbacks, there is an urgent need for a new type of aircraft that can achieve high-speed and flexible flight while having a large load-bearing capacity. Summary of the invention

[0006] The purpose of the present invention is to provide a novel large-load short-wing lift fuselage aircraft, so that the aircraft can have a large load capacity and can fly flexibly at high speed.

[0007] In order to solve the above technical problems, the present invention provides a novel large-load short-wing lift fuselage aircraft, comprising an airfoil lift fuselage, a front short wing smoothly connected to both sides of the lift fuselage nose, a rear short wing smoothly connected to both sides of the lift fuselage tail, a propeller power mechanism arranged at the lift fuselage nose, a V-shaped tail wing arranged at the lift fuselage tail, and a ventral fin arranged at the lift fuselage belly; and the novel large-load short-wing lift fuselage aircraft has a wingspan of ≤2m, a wingspan of the front short wing is smaller than a wingspan of the rear short wing, and a mounting angle of the front short wing is larger than a mounting angle of the rear short wing.

[0008] In one embodiment, the difference between the wingspan of the front short wing and the wingspan of the rear short wing is 0 to 15 cm.

[0009] In one embodiment, the difference between the installation angle of the front short wing and the installation angle of the rear short wing is 3° to 15°.

[0010] In one embodiment, the length of the lifting fuselage is 0.8 to 1.4 m, the width of the lifting fuselage is 0.3 to 0.6 m; the wingspan of the front short wing and the lifting fuselage is 0.8 to 1.2 m; the wingspan of the rear short wing and the lifting fuselage is 1.1 to 1.5 m.

[0011] In one of the embodiments, the fuselage airfoil of the lift fuselage is a NACA2418 airfoil, a NACA 633-018 airfoil, a NACA0018 airfoil or a S1046 airfoil.

[0012] In one embodiment, the wing airfoils of the front short wing and the rear short wing are MH114 airfoil, MH115 airfoil, NACA2412 airfoil, NACA23102, or E195 airfoil.

[0013] In one embodiment, the installation angle of the front short wing at the wing root is 6° to 12°, the aerodynamic torsion angle of the front short wing is -2° to -8°, the wing root chord length of the front short wing is 0.235 to 0.295m, and the wing tip chord length of the front short wing is 0.224 to 0.284m; the installation angle of the rear short wing at the wing root is -1° to -3°, the aerodynamic torsion angle of the rear short wing is 2° to 4°, the wing root chord length of the rear short wing is 0.235 to 0.295m, and the wing tip chord length of the rear short wing is 0.224 to 0.284m.

[0014] In one embodiment, the smooth transition between the lift fuselage and the front short wing and the rear short wing is a transition structure designed with a B-spline curve.

[0015] In one of the embodiments, the lifting fuselage is provided with a plurality of empty compartments in sequence along the length direction of the lifting fuselage; the empty compartment closest to the nose of the lifting fuselage is used for placing batteries; and the empty compartment adjacent to the tail of the lifting fuselage is used for loading cargo.

[0016] In one of the embodiments, the lifting fuselage is flat as a whole, and is provided with integrally formed fuselage side wings on both sides of the lifting fuselage. The fuselage side wings extend from the nose of the lifting fuselage to the tail of the lifting fuselage, and the thickness of the fuselage side wings decreases from thick to thin in the direction from the middle of the lifting fuselage to both sides thereof, and the fuselage side wings are connected to the front short wings and the rear short wings in a smooth transition manner.

[0017] The beneficial effects of the present invention are as follows:

[0018] The present invention adopts a wing-body fusion overall design of a lifting fuselage + short wings. Among them, the lifting fuselage adopts an airfoil design, which can provide greater lift. The role of the short wing is to provide a part of the lift, and at the same time, the longitudinal balance of the aircraft can be completed by adjusting the installation angle to meet the static stability requirements of the aircraft. Compared with traditional fixed-wing UAVs, short-wing fixed-wing UAVs retain the performance of high-speed cruising, and at the same time use the ability of the lifting fuselage to generate lift to greatly reduce the wingspan, have maneuverable and flexible performance, and can be used in small and complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the implementation mode will be briefly introduced below. Obviously, the drawings described below are only some implementation modes of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a schematic diagram of the structure provided by an embodiment of the present invention;

[0021] Figure 2 yes Figure 1 Schematic diagram of the structure viewed from above;

[0022] Figure 3 yes Figure 1 A schematic diagram of a top view structure;

[0023] Figure 4 It is a quadratic Bezier curve graph;

[0024] Figure 5 It is a cubic Bezier curve graph;

[0025] Figure 6 It is a quadratic B-spline graph controlled by three points;

[0026] Figure 7 It is a quadratic B-spline graph controlled by five points;

[0027] Figure 8 It is a curve of lift-drag coefficient of aircraft in the unpowered condition;

[0028] Fig. 9 It is the pressure coefficient cloud diagram of the aircraft when it is unpowered;

[0029] Fig.10 It is a schematic diagram of the velocity field at the fuselage cross section when there is no power;

[0030] Fig.11 It is a curve diagram of lift-drag coefficient of aircraft under powered condition;

[0031] Fig.12 It is the pressure coefficient cloud diagram of the aircraft under power;

[0032] Fig.13 This is a schematic diagram of the velocity field at the fuselage cross section when there is power;

[0033] Fig.14 It is the curve diagram of the moment coefficient in the three directions of pitch, yaw and roll of the aircraft;

[0034] Fig.15 This is the acceleration change data diagram during actual flight;

[0035] Fig.16 This is the data diagram of angular velocity change during actual flight;

[0036] Fig.17 This is a data chart of energy changes during actual flight.

[0037] The reference numerals are as follows:

[0038] 10. Lifting fuselage; 11. Fuselage wings; 12. Empty cabin;

[0039] 20. Short front wing;

[0040] 30. Rear short wing;

[0041] 40. Propeller power mechanism;

[0042] 50. V-shaped tail;

[0043] 60. Pelvic fin. DETAILED DESCRIPTION

[0044] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0045] In response to the current needs of aerial transportation between buildings in cities, stair-climbing delivery of takeout, etc., the present invention designs a new type of large-load short-wing lift fuselage aircraft to solve the problem of aerial transportation between buildings. In order to realize aerial transportation between buildings, it is necessary to take into account that the intervals between buildings in some communities are small. In order to ensure that the aircraft can fly safely, it is necessary to limit the size of the aircraft. However, at the same time, it is still necessary to meet the functions of aerial transportation or high-rise delivery of takeout, and there are also requirements for the mission load of the aircraft. Therefore, for such special transportation tasks, some constraints and restrictions are proposed for the design of the aircraft:

[0046] a) The wingspan of the aircraft is less than 2m; b) The payload is greater than 1.5kg; c) The take-off weight is between 5-10kg.

[0047] At this time, the present invention is implemented as follows Figures 1 to 3 As shown, it includes an airfoil-shaped lifting fuselage 10, a front short wing 20 smoothly connected to both sides of the front of the lifting fuselage 10, a rear short wing 30 smoothly connected to both sides of the rear of the lifting fuselage 10, a propeller power mechanism 40 arranged at the front of the lifting fuselage 10, a V-shaped tail 50 arranged at the tail of the lifting fuselage 10, and a ventral fin 60 arranged on the belly of the lifting fuselage 10; and after adopting this setting method, in addition to ensuring that the wingspan of the new large-load short-wing lifting fuselage aircraft is ≤2m, it is also recommended to set the wingspan of the front short wing 20 to be smaller than the wingspan of the rear short wing 30, and make the installation angle of the front short wing 20 larger than the installation angle of the rear short wing 30.

[0048] It should be pointed out that the function of the fuselage of a traditional fixed-wing UAV is to connect other components such as wings and load cargo, etc. The fuselage does not generate lift, but still generates drag. In view of this feature, the present invention proposes the above-mentioned new type of large-load short-wing lifting fuselage aircraft, which belongs to the overall design of the wing-body fusion of the lifting fuselage 10 and the short wing.

[0049] Among them, the lifting fuselage 10 refers to a layout form in which the fuselage profile is similar to the airfoil lift characteristics in the direction of the airflow, and has a thicker aerodynamic shape. The lifting fuselage 10 can be used to generate lift for the fuselage. In the overall design of the wing-body fusion of the lifting fuselage 10 and the short wing, the fuselage can be loaded with cargo and provide most of the lift; the short wing can provide partial lift, and the installation angle can be flexibly adjusted to achieve the longitudinal balance of the UAV and meet the static stability requirements. The lifting fuselage 10 and the short wing are naturally transitioned by wing-body fusion technology. The advantage of this overall wing-body fusion design is that while retaining the characteristics of high-speed cruising of fixed-wing UAVs, the wingspan of the UAV is reduced, achieving maneuverable and flexible flight and adapting to small and complex environments.

[0050] In order to provide a more detailed description of the new type of large load-bearing short-wing lift fuselage aircraft, the following will explain in detail each major component, as follows:

[0051] Regarding the lifting fuselage 10, Figure 1 As shown, the lifting fuselage 10 is flat as a whole, and one-piece fuselage side wings 11 are provided on both sides of the lifting fuselage 10. The fuselage side wings 11 extend from the nose of the lifting fuselage 10 to the tail, and the thickness of the fuselage side wings 11 decreases from thick to thin in the direction from the middle of the lifting fuselage 10 to both sides thereof, and the fuselage side wings 11 are connected to the front short wings 20 and the rear short wings 30 in a smooth transition manner.

[0052] Among them, for the size design of the lift fuselage 10, it is recommended to set the length of the lift fuselage 10 to 0.8-1.4m, and the width of the lift fuselage 10 to 0.3-0.6m. For example, in this embodiment, the length of the lift fuselage 10 is 1.1m, and the width of the lift fuselage 10 is 0.45m.

[0053] In addition, there are also multiple options for the airfoil of the lift fuselage 10. For example, the airfoil of the lift fuselage 10 can be set to a NACA2418 airfoil, a NACA 633-018 airfoil, a NACA0018 airfoil, an S1046 airfoil, etc. In this embodiment, the NACA2418 airfoil is selected as the airfoil of the fuselage side wing 11 to achieve the large volume function of the lift fuselage 10.

[0054] And if Figure 1 As shown, in this embodiment, a plurality of empty compartments 12 are sequentially provided on the lifting fuselage 10 along the length direction of the lifting fuselage 10. The empty compartment 12 closest to the nose of the lifting fuselage 10 is used for placing batteries, while the empty compartment 12 closest to the tail of the lifting fuselage 10 is used for loading cargo.

[0055] Specifically, the first empty compartment 12 at the head can be used for the carbon tube to pass through and connect to the front short wing 20, and can be used as a battery compartment to store lithium batteries. Moreover, because this is a serial layout, the focus of the aircraft is close to the nose, so in order to better balance the center of gravity, this embodiment places two 4s lithium batteries on the left and right sides in the first empty compartment 12; the second empty compartment 12 is designed to place the flight control board and install GPS and other equipment; the third empty compartment 12 is arranged adjacent to the tail of the fuselage, so the third empty compartment 12 can be used to load cargo.

[0056] In view of the fact that the direct combination between the lifting fuselage 10 and the short wing will result in a large aerodynamic drag at the connection, in order to improve the aerodynamic performance of the aircraft and reduce its aerodynamic drag during flight, the present invention adopts a wing-body fusion design method and designs a transition section between the lifting fuselage 10 and the short wing. In the design process, the present invention selects a B-spline curve design method, specifically setting the smooth transition between the lifting fuselage 10 and the front short wing 20 and the rear short wing 30 as a transition structure designed with a B-spline curve.

[0057] It should be pointed out that the B-spline curve is based on the Bezier curve, retaining the advantages of the Bezier curve such as intuitiveness and convex hull, while also overcoming the shortcomings of the Bezier curve, and has the characteristics of automatic smooth splicing and flexible local modification.

[0058] The B-spline curve is composed of P0, P1, ..., P n (n>3) A k-order spline curve defined by n+1 control points and a set of non-decreasing continuously changing vector nodes ui has the following curve expression:

[0059]

[0060] Where P i represents the control point, u is the vector node, n is the number of control points, k is the order of the B-spline curve, i represents the i-th node vector, B i，k (u) represents the i-th k-order B-spline basis function.

[0061] Basis function B i，k (u) is composed of the DeBoer-Cox recursion formula, expressed as:

[0062] B i，k (u)=U1B i，k-1 (u)+U2B i+1，k-1 (u)

[0063]

[0064]

[0065] Among them, U1 and U2 are the coefficients of the basis function, and k represents the smoothness of the curve.

[0066] To facilitate the understanding of Bezier curves and B-spline curves, Figure 4 and Figure 5 The quadratic and cubic Bezier curves are given respectively, Figure 6 and Figure 7 The quadratic B-spline curves with different control points are given. Figure 4It is a quadratic Bezier curve, which is controlled by three control points P0, P1, and P2. The first and last points of the quadratic curve are P0 and P2 respectively. The first-order derivative of the curve at points P0 and P2 are 2(P1-P0) and 2(P2-P1), that is, the straight line P0P1 and the straight line P1P2 are the tangent slopes at points P0 and P2 respectively. The cubic Bezier curve also passes through the first and last control points respectively, and is tangent to the first and last edges of the control polygon at the starting point and the end point respectively, and the curve tries to approach the remaining control points. The same is true for other higher-order Bezier curves. Obviously, the Bezier curve cannot be modified locally, and changing the position of a control point will affect the shape of the entire curve. The B-spline curve can be defined in segments. By giving m+n+1 vertices, m+1 segments of n-order B-spline curves can be defined. These m+1 segments of n-order B-spline curves are connected end to end to form a curve, and each segment of n-order B-spline curve has n+1 control vertices. Figure 6 is a quadratic B-spline curve with three control points, where m = 0, n = 2, i.e., a quadratic curve. Figure 7 It is a quadratic curve with 5 control points. At this time, m=2, n=2, that is, 3 segments of quadratic curves are connected end to end. Unlike the Bezier curve, the starting point and end point of the quadratic B-spline curve are both located at the midpoint of the control edge. The tangents at the starting point and end point are similar to the Bezier curve. The first and last edges connected by the control points are tangent to the starting point and end point, but at the same time, the points where the multiple segments of the curve are connected are tangent to the remaining control edges.

[0067] B-spline curve design is used when designing the transition section between the fuselage and the wing of an aircraft. First, the contour of the fuselage and the contour at the root of the wing are interrupted to obtain corresponding spline curves, and then two B-spline curves connecting the local contour of the fuselage and the contour of the root of the wing are obtained through B-spline curve design. Multiple spline curves form a closed surface, and the surface designed by B-spline curve can be obtained. The surface effect can be seen Figure 1 Obviously, the transition section curved surface after the wing-body fusion design can make the curvature transition between the fuselage and the wing more natural and smooth. For example, in this embodiment, the nose of the lift fuselage 10 is connected and transitioned with the front short wing 20 through the B-spline curve curved surface B1, and the tail of the lift fuselage 10 is connected and transitioned with the rear short wing 30 through the B-spline curve curved surface B2.

[0068] It should be pointed out that the main factors that affect the lift of the wing include the incoming flow velocity, the reference area of ​​the wing, and the lift coefficient of the wing, which can be specifically expressed as:

[0069]

[0070] L represents lift, represents air density, represents incoming flow velocity, S is the reference area of ​​the wing, and is expressed as the lift coefficient.

[0071] Among them, under the condition of small angle of attack, the lift coefficient is linearly positively correlated with the incoming flow angle of attack (the same applies to the wing installation angle), that is, the lift coefficient will increase as the incoming flow angle of attack increases.

[0072] Since the airfoil used in the lift fuselage 10 is a positive lift airfoil, while the fuselage can provide a large lift, it will also bring about an additional nose-down moment, resulting in insufficient longitudinal stability of the aircraft and difficulty in aerodynamic balancing. To this end, the present invention solves the problem of aircraft balancing by changing the installation angle and aerodynamic torsion angle of the front and rear short wings. The front wing installation angle is greater than the rear wing installation angle, so that the front wing can generate a greater lift, and the distance from the center of gravity of the entire aircraft will generate a larger nose-up moment. The rear wing installation angle is smaller, so that the lift generated by the rear wing can be relatively small, and the distance from the center of gravity of the entire aircraft will generate a smaller nose-down moment. In this way, it can be ensured that the combined moment of the front and rear wings on the aircraft as a whole is a nose-up moment, and the nose-down moment caused by the fuselage can be overcome.

[0073] In addition, since the center of gravity of the aircraft is relatively close to the nose, the lift of the front wing has a smaller torque on the center of gravity, while the torque of the rear wing is larger, and the center of gravity needs to be located in front of the aerodynamic focus for static stability considerations. Therefore, on the one hand, it is necessary to strive to move the overall aerodynamic focus of the aircraft backward to ensure that the center of gravity can be moved backward. From this perspective, it is necessary to appropriately increase the wingspan of the rear wing to achieve the backward shift of the aerodynamic focus. On the other hand, in order to make the combined torque of the front and rear wings as a whole to the distance of the aircraft a nose-up torque, it is necessary to increase the installation angle of the front wing and reduce the installation angle of the rear wing, that is, to increase the installation angle difference between the front and rear wings.

[0074] Based on the above considerations, after many design attempts, the preferred wingspan setting parameters of the front short wing 20 and the rear short wing 30 were finally determined. At the same time, considering that the aircraft's anti-stall performance may be poor due to the excessive installation angle, negative aerodynamic torsion angles were designed for the front and rear short wings 30 to ensure that the aircraft has better anti-stall performance.

[0075] Specifically, regarding the front short wing 20, as Figure 1 and Figure 3 As shown, there are many options for the airfoil, for example, the airfoil of the front short wing 20 can be set to MH114 airfoil, NACA2412 airfoil, NACA23102 airfoil, E195 airfoil, etc. In this embodiment, the airfoil of the front short wing 20 is set to MH114 airfoil, so as to improve the aerodynamic performance of the aircraft.

[0076] In addition, there are corresponding preferred setting ranges for various setting parameters of the front short wing 20. For example, the wingspan of the front short wing 20 and the lift fuselage 10 can be set to 0.8 to 1.2 m, the installation angle a1 at the wing root of the front short wing 20 can be set to 6° to 12°, the aerodynamic torsion angle a2 of the front short wing 20 can be set to -2° to -8°, the wing root chord length of the front short wing 20 can be set to 0.235 to 0.295 m, and the wing tip chord length of the front short wing 20 can be set to 0.224 to 0.284 m.

[0077] In this embodiment, the wingspan of the front short wing 20 and the lift fuselage 10 is set to be 1m, the installation angle a1 at the wing root of the front short wing 20 is 9°, the aerodynamic torsion angle a2 of the front short wing 20 is -5°, the chord length of the wing root of the front short wing 20 is 0.265m, and the chord length of the wing tip of the front short wing 20 is 0.254m.

[0078] Specifically, the installation angle a1 at the wing root of the front short wing 20 refers to the angle between the chord line of the wing section at the wing root and the axis of the lift fuselage 10 when the front short wing 20 is installed on the lift fuselage 10, and the aerodynamic torsion angle a2 of the front short wing 20 refers to the angle at which the wing angle of attack gradually changes from the wing root to the wing tip of the front short wing 20.

[0079] Regarding the rear short wing 30, Figure 1 and Figure 3 As shown, there are many options for the airfoil, for example, the airfoil of the rear short wing 30 can be set to MH114 airfoil, NACA2412 airfoil, NACA23102 airfoil, E195 airfoil, etc. In this embodiment, the airfoil of the rear short wing 30 is set to MH114 airfoil, so as to improve the aerodynamic performance of the aircraft.

[0080] In addition, there are corresponding preferred setting ranges for various setting parameters of the rear short wing 30. For example, the wingspan of the rear short wing 30 and the lift fuselage 10 can be set to 1.1 to 1.5 m, the installation angle b1 at the wing root of the rear short wing 30 can be set to -1° to -3°, the aerodynamic twist angle b2 of the rear short wing 30 can be set to 2° to 4°, the chord length of the wing root of the rear short wing 30 can be set to 0.235 to 0.295 m, and the chord length of the wing tip of the rear short wing 30 can be set to 0.224 to 0.284 m.

[0081] In this embodiment, the wingspan of the rear short wing 30 and the lift fuselage 10 is set to be 1.3m, the installation angle b1 at the wing root of the rear short wing 30 is -2°, the aerodynamic twist angle b2 of the rear short wing 30 is 3°, the chord length of the wing root of the rear short wing 30 is 0.265m, and the chord length of the wing tip of the rear short wing 30 is 0.254m.

[0082] Specifically, the installation angle b1 at the wing root of the rear short wing 30 refers to the angle between the chord line of the wing section at the wing root and the axis of the lift fuselage 10 when the rear short wing 30 is installed on the lift fuselage 10, and the aerodynamic torsion angle b2 of the rear short wing 30 refers to the angle at which the wing angle of attack gradually changes from the wing root to the wing tip of the front short wing 20.

[0083] It should be pointed out that since the mutual matching between the front short wing 20 and the rear short wing 30 will bring about better performance, when setting the relevant parameters of the front short wing 20 and the rear short wing 30, it is recommended to preferably set the difference between the wingspan of the front short wing 20 and the wingspan of the rear short wing 30 to 0 to 15 cm, and set the difference between the installation angle a1 of the front short wing 20 and the installation angle b1 of the rear short wing 30 to 3° to 15°.

[0084] Regarding the propeller power mechanism 40, Figure 1 As shown, it adopts dual motors and propellers arranged on the left and right sides of the leading edge of the lift fuselage 10. The advantage of using a front-pull propeller is that the slipstream effect of the propeller can be fully utilized to increase the airflow velocity on the surface of the lift fuselage 10 and the front short wing 20, thereby increasing the dynamic pressure and improving the lift of the drone.

[0085] It should be pointed out that the specific design parameters of the aircraft in this embodiment include the following configuration: the total take-off weight is about 6.1kg, of which the fuselage structure weighs about 1.9kg, the power system device weighs about 0.39kg, the lithium battery weighs about 0.94kg, the flight control and other equipment weighs about 1kg, the payload weight is about 1.87kg, and the payload accounts for about 30.6% of the total take-off weight.

[0086] The total takeoff weight of an aircraft can be divided into the following parts:

[0087] W t =W ε +W m +W b +W p

[0088] Where W t is the takeoff weight, which does not change during the flight; W ε is the structural weight, W m is the weight of power and control device, W b is the battery weight, W p is the mission payload weight.

[0089] Based on this, the design considerations are made. In this embodiment, the maximum thrust of a single motor is designed to be 26.33N, and the total thrust is about 52.66N, so the thrust-to-weight ratio can reach 0.863; specifically, the brushless motor selected for the propeller power mechanism 40 is the Shuangtian ECO2826720kV motor, which has a maximum thrust of 26.33N under static measurement. Considering that the total takeoff weight is about 6.1kg, the design uses dual-engine power, and the total thrust can reach 52.66N. The thrust-to-weight ratio of the aircraft is:

[0090]

[0091] The propeller is a 13-inch propeller that matches the motor. Taking into account the propeller diameter and the requirement that the fuselage components do not come into contact with the ground during taxiing, the landing gear height is designed to be 17 cm.

[0092] It should be pointed out that since this embodiment adopts a combination design of a lift fuselage 10 and short wings, the wingspan is greatly reduced, which will result in a smaller lateral damping coefficient of the UAV, difficulty in converging lateral stability during flight, and poor dynamic stability. Therefore, in order to solve this problem, this embodiment adds a V-shaped tail 50 and a ventral fin 60.

[0093] Specifically, regarding the V-shaped tail 50, Figure 1 As shown, the V-shaped tail 50 is arranged on the upper surface of the tail of the lifting fuselage 10, and extends obliquely upward on both sides of the lifting fuselage 10. After the V-shaped tail 50 is set, the V-shaped tail 50 can take into account the functions of both the horizontal tail and the vertical tail, and play a longitudinal and lateral stabilizing role at the same time.

[0094] Regarding the pelvic fin 60, Figure 2 As shown, the ventral fin 60 is provided on the lower surface of the tail of the lift fuselage 10, and extends obliquely downward on both sides of the lift fuselage 10. After the ventral fin 60 is provided, the ventral fin 60 is equivalent to the vertical tail, which can increase the heading stability of the UAV when the UAV side slips.

[0095] In order to better verify the rationality of the above design scheme, the present invention performs CFD aerodynamic simulation calculations on the design prototype model to better analyze its flight performance.

[0096] (1) Unpowered aerodynamic performance

[0097] Without considering the front propeller (no power), the lift-drag coefficient curve of the aircraft can be seen Figure 8 At an angle of attack of 0°, the lift coefficient is greater than 0.1. At an angle of attack of 10°, the lift coefficient is between 0.8 and 0.9. In the small angle of attack range, the lift coefficient changes linearly with the angle of attack. It can be seen from the extreme curve that at an angle of attack of 6°, the lift-to-drag ratio reaches its maximum, which is about 7.

[0098] Fig. 9 The pressure coefficient cloud diagram of the aircraft without power is given. The pressure coefficient is small at the leading edge of the lift fuselage 10 and the front short wing 20, and the pressure difference between the upper and lower surfaces is large, so there is a large lift. When the incoming flow velocity is 18m / s, the velocity distribution at the cross section of the lift fuselage 10 can be seen. Fig.10 When the airflow flows through the surface of the lift fuselage 10, it is like flowing through a wing, and the flow speed on the upper and lower surfaces undergoes a process of first increasing and then decreasing. Among them, the flow speed on the upper surface is faster and the pressure is smaller. There is a pressure difference between the upper and lower surfaces, so the fuselage can also generate lift.

[0099] (2) Powerful aerodynamic performance

[0100] The advantage of placing the propeller power mechanism 40 in front is that the slipstream effect of the propeller can be fully utilized. The influence of the front propeller on the aerodynamic performance of the aircraft can be seen. Fig.11 . Figure 8 and Fig.11 It can be found that the front propeller can improve the lift coefficient of the aircraft. Although it will also bring drag, the overall maximum lift-to-drag ratio remains basically unchanged, still about 7. The slipstream behind the front propeller disc can accelerate the flow through the wing and the lift fuselage 10 surface, increase the dynamic pressure on the wing and the lift fuselage 10 surface, and thus improve the lift of the aircraft. This means that during the take-off phase, the aircraft can obtain a larger lift coefficient, the minimum take-off speed is reduced, and the runway distance is also reduced, so that short-distance takeoff and landing can be achieved.

[0101] Fig.12 The pressure cloud diagram on the surface of the lift fuselage 10 when the propeller is powered is shown. Fig. 9 and Fig.12 It can be found that when there is propeller power, the pressure coefficient on the upper surface of the front short wing 20 behind the propeller disc is smaller, and the pressure coefficient on the upper surface of the rear short wing 30 is also relatively small, indicating that the wake behind the propeller disc has a higher flow rate when flowing through the surface of the aircraft. The propeller slipstream increases the dynamic pressure on the surface of the aircraft, which can improve the overall lift coefficient of the aircraft. When there is propeller power, the velocity field at the propeller disc section can be seen Fig.13 When the incoming flow velocity is 18m / s, the airflow velocity behind the impeller becomes significantly larger, and the airflow velocity in most areas is greater than 20m / s. Fig.10 and Fig.13 , indicating that the propeller can accelerate the airflow behind the propeller disk, and there is a slipstream effect on the surface of the aircraft. This effect can increase the lift coefficient of the aircraft.

[0102] (3) Stability analysis

[0103] Fig.14The rolling moment coefficient-sideslip angle curve, pitch moment coefficient-angle of attack curve, and yaw moment coefficient-sideslip angle curve of the aircraft are given respectively. As can be seen from the figure, when the aircraft rolls to the right, that is, it causes a right-side slide, the aircraft will generate a negative rolling moment-left roll, so that the aircraft has the ability to restore the initial state, which shows that the aircraft has stability in the rolling direction. When the aircraft raises its head, the aircraft will generate a negative pitch moment-head-down moment, which makes the aircraft tend to lower its head, that is, it has the ability to restore the initial state, which shows that the aircraft has stability in the pitch direction. When the aircraft slides to the right, the aircraft will generate a positive yaw moment-right yaw, which makes the aircraft tend to yaw to the right. It has stability in the yaw direction.

[0104] On the basis that the aircraft meets the static stability in pitch, yaw and roll, the focus position of the aircraft can be calculated, which is 0.4m from the nose. Considering the static stability margin, the center of gravity position is designed to be 0.38m, and the static stability margin is about 8%.

[0105] Furthermore, the present invention has also been subjected to actual flight tests. Fig.15 It is the acceleration change data of the aircraft during actual flight. Fig.16 It is the angular velocity change data of the aircraft during actual flight. Fig.17 The actual flight test results show that the short-wing lift fuselage aircraft designed by the present invention has short-distance takeoff and landing capabilities and good flight stability. By utilizing the lift fuselage 10 and the propeller slipstream effect, the high-lift and high-load flight goal can be achieved.

[0106] In summary, the present invention generates the main lift through the lift fuselage 10 to achieve the high lift and large load-bearing capacity of the aircraft. The function of the short wing, in addition to helping the aircraft solve the stability problem, can also achieve high-speed cruising function. Compared with traditional fixed-wing aircraft, the present invention has a smaller wingspan, a smaller turning radius in the air, and is more flexible in a small space. At the same level, the present invention has the advantages of larger volume and stronger load-bearing capacity.

[0107] The above is a preferred embodiment of the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A new type of large load-bearing short-wing lift fuselage aircraft, characterized in that: The invention comprises a lifting fuselage with an airfoil shape, a front short wing smoothly connected to both sides of the lifting fuselage nose, a rear short wing smoothly connected to both sides of the lifting fuselage tail, a propeller power mechanism arranged at the lifting fuselage nose, a V-shaped tail wing arranged at the lifting fuselage tail, and a ventral fin arranged at the lifting fuselage belly; The wingspan of the novel large-load short-wing lift fuselage aircraft is ≤2m, the wingspan of the front short wing is smaller than the wingspan of the rear short wing, and the installation angle of the front short wing is larger than the installation angle of the rear short wing.

2. The novel large-load short-wing lift fuselage aircraft according to claim 1 is characterized in that: The difference between the wingspan of the front short wing and the wingspan of the rear short wing is 0 to 15 cm.

3. The novel large-load short-wing lift fuselage aircraft according to claim 1 is characterized in that: The difference between the installation angle of the front short wing and the installation angle of the rear short wing is 3° to 15°.

4. The novel large-load short-wing lift fuselage aircraft according to claim 1 is characterized in that: The length of the lifting fuselage is 0.8-1.4 m, and the width of the lifting fuselage is 0.3-0.6 m; The wingspan of the front short wing and the lifting fuselage is 0.8 to 1.2 m; The wingspan formed by the rear short wing and the lifting fuselage is 1.1 to 1.5 m.

5. The novel large-load short-wing lift fuselage aircraft according to claim 1 is characterized in that: The fuselage airfoil of the lifting fuselage is a NACA2418 airfoil, a NACA 633-018 airfoil, a NACA0018 airfoil or a S1046 airfoil.

6. The novel large-load short-wing lift fuselage aircraft according to claim 1 is characterized in that: The wing airfoils of the front short wing and the rear short wing are MH114 airfoil, MH115 airfoil, NACA2412 airfoil, NACA23102, or E195 airfoil.

7. The novel large-load short-wing lift fuselage aircraft according to claim 1 is characterized in that: The installation angle at the wing root of the front short wing is 6° to 12°, the aerodynamic twist angle of the front short wing is -2° to -8°, the wing root chord length of the front short wing is 0.235 to 0.295m, and the wing tip chord length of the front short wing is 0.224 to 0.284m; The installation angle at the wing root of the rear short wing is -1° to -3°, the aerodynamic twist angle of the rear short wing is 2° to 4°, the wing root chord length of the rear short wing is 0.235 to 0.295m, and the wing tip chord length of the rear short wing is 0.224 to 0.284m.

8. The novel large-load short-wing lift fuselage aircraft according to claim 1 is characterized in that: The smooth transition between the lift fuselage and the front short wing and the rear short wing is a transition structure designed with a B-spline curve.

9. The novel large-load short-wing lift fuselage aircraft according to claim 1, characterized in that: Along the length direction of the lifting fuselage, the lifting fuselage is provided with a plurality of empty cabins in sequence; The empty compartment closest to the nose of the lifting fuselage is used to place batteries; The empty compartment adjacent to the tail of the lifting fuselage is used for loading cargo.

10. The novel large-load short-wing lift fuselage aircraft according to claim 1, characterized in that: The lifting fuselage is flat as a whole, and is provided with integrally formed fuselage side wings on both sides of the lifting fuselage. The fuselage side wings extend from the nose of the lifting fuselage to the tail of the lifting fuselage, and the thickness of the fuselage side wings decreases from thick to thin in the direction from the middle of the lifting fuselage to both sides thereof, and the fuselage side wings are connected to the front short wings and the rear short wings in a smooth transition manner.

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