Lift augmentation assembly for fixed-wing aircraft - Patents.com

Abstract

The present invention relates to a lift assembly (300) for an aircraft. The lift assembly (300) includes a wing (102) and at least one vertical rotor (118) disposed below the wing (102). The vertical axis (121) of the vertical rotor (118) is disposed within the span of the wing (102). The vertical rotor (118) is operable during forward flight of the aircraft. The distance (122) between the leading edge (108) and the vertical axis (121) of the vertical rotor (118) is a function of the rotations per minute (rpm) of the rotor (118), the angle of attack (116) of the wing, and the coefficient of chord (117). The lift assembly (300) generates enhanced lift greater than the sum of the lift generated by the wing (102) and the rotor (118) individually, thereby enabling the provision of a smaller wing area and therefore reducing drag.

Description

Detailed Description of the Invention

[0001] [Technical field] The present invention relates to aircraft, and more particularly to lift assemblies for aircraft. 〔background〕 An aircraft's dynamics depend on opposing drag and gravity forces acting on the aircraft. Lift serves to overcome the effect of gravity on the aircraft's dynamics. Lift is provided by fixed wings designed to create a pressure differential to generate lift during forward flight. Alternatively, rotors can generate lift, such as in the case of rotorcraft. A set of rotors can be used to generate lift during vertical takeoff, landing, or while stationary in the air. However, during forward flight, these rotors are idle as they provide no lift and are a dead load.

[0002] CN103043212A discloses a composite aircraft composed of fixed wing and electric multi-rotor, which includes a set of electric multi-rotor power systems and an overall controller. The fixed wing power system and the electric multi-rotor power system are structurally independent of each other. The utility model includes a fixed wing control system and an electric multi-rotor control system for controlling the operation of the electric multi-rotor power system. The overall controller is further configured to control the fixed wing control system and the electric multi-rotor control system to operate independently or in cooperation. The rotor rotation plane of the electric multi-rotor power system is parallel to the central axis of the fuselage. Ability to freely switch between two flight modes for both takeoff and flight of helicopters, takeoff and landing of fixed wing aircraft, etc., or use of two powertrains during takeoff and landing.

[0003] Lift coefficient (C L) is a dimensionless coefficient that relates the lift force generated by a lifting body to the fluid density, fluid velocity, and associated reference area around the body. A lifting body is a foil or a complete foil-bearing body, such as a fixed-wing aircraft. C L is a function of the shape of the body, the angle of the lifting body to the airflow, the Reynolds number, and the Mach number. The shape of the body is C L It is the main factor that determines the value of C L is a number used by aerodynamicists to model all of the complex dependencies of shape, pitch, and multiple airflow conditions on lift.

[0004] The payload an aircraft will carry and the desired speed of travel influence the required lift as well as the size and configuration of the wings. The wing configuration in turn influences the size of the aircraft, which defines the range of use of the aircraft. A compact, energy-efficient system for generating the lift required by an aircraft would enable increased range and improved energy efficiency.

[0005] Efficient design of aircraft requires striving to increase the lift coefficient available from the components or mechanisms used to generate lift.

[0006] Given the significance of increasing the lift coefficient in improving the range and energy efficiency of aircraft, it is necessary to strive to design systems that achieve this objective. The payload carrying capacity, endurance and range of the aircraft can be improved.

[0007] OBJECTS OF THEINVENTION SUMMARY OF THE PRESENT EMBODIMENT It is a primary object of the present invention to provide an increased lift coefficient for fixed wing aircraft.

[0008] The second purpose is to reuse the rotors that are parked during forward flight.

[0009] Summary of the Invention The present invention relates to a lift assembly for an aircraft, the lift assembly comprising a wing and at least one vertical rotor, the vertical rotor being disposed beneath the wing such that the vertical rotor is disposed within the span of the wing, the vertical rotor being operable during forward flight, and the vertical rotor being disposed at a placement distance from a leading edge, the placement distance being the distance between the leading edge and the vertical axis of the vertical rotor, the placement distance being a function of the revolutions per minute of the vertical rotor, the diameter of the vertical rotor, the angle of attack of the wing, and the chord coefficient of the wing. The lift assembly is designed to maximize lift.

[0010] The lift assemblies generate enhanced lift, which allows for the provision of smaller wing areas, thus reducing drag. This allows the aircraft to travel at slower speeds, further reducing drag, or to carry a larger payload at the same speed. The endurance and range of the aircraft are increased.

[0011] These objects and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings.

[0012] BRIEF DESCRIPTION OF THE DRAWINGS The object of the invention will now be explained in more detail with reference to the accompanying drawings, in which: FIG. 1 illustrates the airflow in the presence of fixed wings and an operational vertical rotor in one embodiment of the present subject matter.

[0013] FIG. 2 illustrates the pressure distribution within the flow field of a lift assembly, as estimated by computational fluid dynamics (CFD) simulation, in one embodiment of the present subject matter.

[0014] FIG. 3 shows a contour plot of the variation of the combined lift of a lift assembly with varying rotor position and angle of attack for a 48 cm chord and rotor speed of 6500 RPM in one embodiment of the present subject matter.

[0015] FIG. 4 illustrates the increase in lift at various rotor placement distances as throttle is increased from 0 to 100% in one embodiment of the present subject matter.

[0016] FIG. 5 illustrates a bottom view of a lift assembly in one embodiment of the present subject matter.

[0017] FIG. 6 illustrates a front view of a lift assembly in one embodiment of the present subject matter.

[0018] [Reference number] fixed wing 102 Direction of forward flight 104 Airflow 106 Leading edge 108 trailing edge 110 Pressure side 112 Suction side 114 angle of attack 116 String 117 Vertical Rotor 118 Motor 119 Blade 120 Vertical axis 121 Placement distance 122 Connecting element 124 Lift Assembly 300 Detailed Description of the Invention In an aircraft with fixed wings, the wings generate lift during forward flight. As air flows over the wings during forward flight, a pressure field is created depending on the shape and orientation of the wing, which has low pressure at the top of the wing, known as the suction side, and high pressure at the bottom of the wing, known as the pressure side. Lift is created as a result of the pressure field.

[0019] Additionally, a vertical rotor is provided for use during takeoff, landing and stationary. However, during forward flight, the vertical rotor is a dead weight. A lift assembly has been developed in the present invention that utilizes the lift provided by actuating the vertical rotor during forward flight. The presence of the rotors and their actuation changes the flow field and therefore the pressure field around the wing.

[0020] FIG. 1 illustrates the airflow with a fixed wing and an operational vertical rotor in one embodiment of the present subject matter. A cross section of a fixed wing 102 is shown. Arrow 104 indicates the direction of forward flight. Airflow toward and around the fixed wing 102 is shown by airflow line 106. The fixed wing 102 has a first end, also referred to as leading edge 108, and a second end, also referred to as trailing edge 110. Below the fixed wing 102, an area of ​​high pressure is created, referred to as pressure side 112, and above the fixed wing 102, an area of ​​low pressure is created, referred to as suction side 114. A dotted line along the center of the fixed wing 102 forms an angle with the horizontal axis, referred to as angle of attack 116. The distance between the leading edge 108 and the trailing edge 110 is referred to as chord 117. Chord 117 is given by the symbol c. The vertical rotor 118 is disposed below the fixed wing 102 and is actuated during forward flight. The vertical axis 121 of the vertical rotor 118 is disposed around the periphery of the span of the fixed wing 102 on the pressure side 112.

[0021] When the vertical rotor 118 is properly positioned around the fixed wing 102, the airflow is modified such that the pressure fields at the pressure side 112 and the suction side 114 are modified to increase lift. The vertical distance between the leading edge 108 and the vertical axis 121 is referred to as the positioning distance 122. The positioning distance 122 is given by the variable y. The ratio of the positioning distance 122 to the chord 117, y / c, is a dimensionless variable given by the symbol p. When the vertical axis 121 is located at the leading edge 108, p is 0, and when the vertical axis 121 is located at the trailing edge 110, p is 1. FIG. 2 shows the pressure distribution estimated by a computational fluid dynamics (CFD) simulation of the flow field of the lift assembly in one embodiment of the present subject matter. The interaction in the flow field between the wing and the rotor is clearly observed in the performed CFD simulation. A low pressure area exists in the entire suction side extending all the way up to the rotor. This causes the entire system to generate a synergistic vertical upward force.

[0022] Synergistic lift is produced by appropriately positioning one or more rotors around the periphery of the wing along its span such that operation of the rotor(s) increases the overall upward pressure on the wing surface, thereby increasing the lift produced by the wing beyond the sum of the lift produced by the wing and rotor(s) individually.

[0023] The lift is given by the lift coefficient C L It is quantified by C L is used as a means of estimating the effectiveness of the lift assembly.

[0024]

number

[0025] The lift force produced by the lift assembly is given by L, the density of air is given by ρ, the speed of air is given by v, and the planar area of ​​the wing is given by S. The lift force L also serves as a measure to evaluate the effectiveness of the lift assembly.

[0026] To analyze this phenomenon, experiments were conducted to determine the lift forces of a lift assembly with a stationary rotor located at various distances from the leading edge. The same experiments were then conducted to determine the lift forces of a lift assembly with a rotor operating at different revolutions per minute, from 500 to 6500 in increments of 500. The details of the experiments are as follows: Experiments were performed by placing the fixed blades on a flat mounting surface with supports at the blade tips so that the angle of attack could be varied. The mounting surface was then placed on an electric weighing scale and the lift generated was determined. The vertical rotor was mounted on a stand with its axis perpendicular to the mounting surface. An industrial fan was placed at a fixed distance from the leading edge of the blade and was used to create a free stream flowing over the device by blowing air at a constant speed. The rotor position was varied across the chord of the blades to vary the rotor RPM and blade angle of attack. It was observed that increasing the blade angle of attack for a given rotor RPM and rotor position increased the lift coefficient. For a given rotor RPM and blade angle of attack, placing the rotor further downstream increased the lift coefficient. A higher rotor RPM with a given rotor position and blade angle of attack increased the lift coefficient. Also, increasing the rotor RPM increased the difference in lift coefficient for different rotor positions and blade angles of attack. The airflow and the stop angle of the blades were significantly altered by the presence of the rotor. The experiment for the same set of parameters was repeated with the industrial fan turned off and only the rotor activated. The results obtained with the rotor stationary and the industrial fan turned on were compared with those obtained with the rotor activated and the industrial fan turned off. The former gives the lift generated by the blades separately, whereas the latter gives the lift generated by the rotor separately. The lift generated in both these scenarios was summed up to give the sum of the lift coefficient of the two components activated separately. The lift coefficient estimated when both the rotor and the industrial fan are activated gives the combined effect of the blades and rotor activated during forward flight. The comparison of the experimental results successfully demonstrated the synergy between the fixed blades and the activated rotor by providing a higher lift coefficient for the device compared to the sum of the lift coefficients of the two components activated separately.

[0027] For this experiment, the rotor height above the wing was fixed, and the angle of attack (the angle at which the airfoil is positioned) was also varied.

[0028] The lift generated by the combination of the fixed wing 102 and the vertical rotor 118 with the vertical rotor positioned at different p values ​​was determined and compared to the sum of the lift generated by the fixed wing 102 and the vertical rotor 118 individually.

[0029] Lift coefficient C determined by the combination of fixed wing 102 and vertical rotor 118 Lnew and the lift coefficient C, which is determined by the sum of the lift forces generated by the fixed wing 102 and the vertical rotor 118 separately. L The ratio of to measures the synergistic lift.

[0030] FIG. 3 shows a contour plot of the variation of the synergistic lift of the lift assembly with varying rotor position and angle of attack under conditions of 48 cm chord and 6500 RPM in an embodiment of the subject matter. From FIG. 3, it can be observed that the total lift generated by the combined system of the fixed wing 102 and the operating vertical rotor 118 is greater than the sum of the lift generated by the fixed wing 102 and the vertical rotor 118 individually, leading to a synergistic lift. Furthermore, under conditions of 48 cm chord and 6500 RPM of the rotor, the ratio varies with the value of p and the angle of attack, with a maximum value of about 20. The 20-fold increase shows the effectiveness of using a properly designed lift assembly with an operating rotor in forward flight.

[0031] Thus, to improve the lift of the aircraft, the lift assembly 300 comprises fixed wings 102 and at least one vertical rotor 118 arranged to increase lift when intended for operation.

[0032] The lift assembly 300 is designed to optimize the parameters of the lift assembly 300. The value of p at which the lift assembly 300 produces maximum lift depends on the operating RPM of the vertical rotor 118, the chord 117, and the angle of attack 116. Thus, the chord 117, the placement distance 122, the working RPM of the vertical rotor 118, and the angle of attack 116 are optimized to obtain a lift assembly with increased lift. For this purpose, CFD simulations were performed for the given conditions of 1 m chord, working RPM of the vertical rotor at 70% throttle, and an angle of attack of 0 degrees, with the rotor fixed at 0 m in the z-axis direction and placed at various positions around the wing along the x- and y-directions. The generated lift is shown in Table 1 in units of N.

[0033] [Table 1]

[0034] Table 1: The generated lift (in N) estimated by CFD simulation for the given conditions of 1m chord, vertical rotor operating RPM at 70% throttle, and 0 degree angle of attack, with the rotor positioned at various positions around the wing.

[0035] The results show that the optimum location for rotor positioning to obtain maximum lift is on the rear side of the wing: maximum lift occurs when the rotor is just behind the wing at y=0, and as the absolute value of the y position increases, lift decreases.

[0036] Another important coefficient estimated in the CFD study is the drag increase shown in Table 2. These values ​​represent the drag reduction caused by the rotor interacting with the airfoil flow field, and ultimately the reverse drag, or thrust.

[0037] [Table 2]

[0038] Table 2: Drag increase estimated by CFD simulation for the rotor positioned at various positions around the wing for the given conditions of 1m chord, vertical rotor operating RPM at 70% throttle, and 0 degree angle of attack.

[0039] By locating the vertical rotor (118) upstream of the airfoil (102), i.e., near the leading edge (108), drag is minimized and generated to act in the thrust direction.

[0040] However, since the drag at the location of maximum lift is negative, the optimum position for the vertical rotor for a given set of parameters is at the rear of the wing. To select the optimum position for the vertical rotor, the ratio of lift to drag was estimated and is summarized in Table 3.

[0041] [Table 3]

[0042] Table 3: The ratio of lift increase to drag increase (L / D) estimated by CFD simulation for the given conditions of a vertical rotor operating speed of 1m chord, 70% throttle, and 0 degrees angle of attack, with the rotor positioned at various positions around the wing.

[0043] The ratio of lift to drag is greatest at the rear of the wing, so the optimum location for the vertical rotor is at the rear of the wing.

[0044] Figure 4 illustrates the increase in lift as the rotor vertical distance changes as the throttle increases from 0 to 100% in one embodiment of the present subject matter. Figure 4 illustrates that as the throttle increases from 0 to 100%, the lift increases linearly.

[0045] 5 illustrates a bottom view of a lift assembly (300) in one embodiment of the present subject matter. The fixed wing 102 is viewed with the vertical rotor 118 positioned within the wingspan of the fixed wing 102. The vertical rotor 118 is positioned a placement distance 122 away from the leading edge 108.

[0046] 6 shows a front view of the lift assembly (300) in one embodiment of the present subject matter. The lift assembly (300) further comprises a body (not shown) that supports the fixed wing 102. The motor 119 is attached to the body using a linking element 124. The vertical rotor 118 is thereby attached to the body by the linking element 124. The linking element 124 may be a pod or a strut.

[0047] In one embodiment of the present invention, the increased C L To provide this, multiple vertical rotors 118 may be arranged in a lift assembly 300 .

[0048] In another embodiment of the present invention, the vertical rotor 118 may be installed on an existing fixed-wing aircraft. In this case, the angle of attack 116 is fixed and the value of p must be appropriately selected to increase the lift coefficient. After determining p, the vertical rotor 118 is installed.

[0049] An important aspect of the invention is the positioning of one or more rotors in close proximity to the fixed wing. This positioning changes the flow field and, as a result, the pressure field around the fixed wing, resulting in an increase in the lift generated by the fixed wing. The net effect is that the total lift generated by the combined system of the wing and the moving rotor is greater than the sum of the individual lift forces that would be generated by the fixed wing and the stationary rotor. Thus, the fixed wing does not need to generate the total lift to balance the weight of the aircraft in forward flight, and the fixed wing can be smaller than usual. The smaller the wing, the less drag the aircraft experiences, making the aircraft more compact.

[0050] While the foregoing description will enable one of ordinary skill in the art to make and use what is presently believed to be the best mode, one of ordinary skill in the art will understand and recognize the existence of variations, permutations, and equivalents of the specific embodiments, methods, and examples herein. Thus, the present invention should not be limited by the embodiments, methods, and examples described above, but rather by all embodiments and methods that fall within the scope and spirit of the invention as claimed. [Brief description of the drawings]

[0051] [Figure 1] 1 illustrates airflow in the presence of fixed wings and an operable vertical rotor in one embodiment of the present subject matter. [Diagram 2] 1 illustrates pressure distribution within the flow field of a lift assembly as estimated by computational fluid dynamics (CFD) simulation in one embodiment of the present subject matter. [Diagram 3] 1 shows a contour plot of the variation of the combined lift of a lift assembly with varying rotor position and angle of attack for a 48 cm chord and rotor speed of 6500 RPM in one embodiment of the present subject matter. [Figure 4] 1 illustrates the increase in lift at various rotor placement distances as throttle is increased from 0 to 100% in one embodiment of the present subject matter. [Diagram 5] FIG. 2 illustrates a bottom view of a lift assembly in one embodiment of the present subject matter. [Figure 6] FIG. 2 illustrates a front view of a lift assembly in one embodiment of the present subject matter.

Claims

1. A lift assembly (300) for an aircraft, comprising: a wing (102) having a leading edge (108); at least one vertical rotor (118) disposed below said wings (102); a vertical axis (121) of the vertical rotor (118) is disposed within the span of the blades (102); the vertical rotor (118) is operable during forward flight of the aircraft; a placement distance (122) between the leading edge (108) and the vertical axis (121) of the vertical rotor (118) being a factor of the revolutions per minute of the vertical rotor (118), the angle of attack (116) of the blades, and the chord (117); A lift assembly (300) in which the position of the vertical rotor (118) or the angle of attack (116) of the wing (102) is set such that the combined effect of the wing (102) and the operating vertical rotor (118) provides a higher lift coefficient compared to the sum of the lift coefficients of the wing (102) and the vertical rotor (118) operating individually.

2. the optimum position for positioning the vertical rotor (118) is at the aft side of the wing (102) along the central axis in the chord direction (117) for maximum lift; The lift assembly (300) of any preceding claim, wherein the lift force decreases as the positioning of the vertical rotor (118) is moved away from the central axis in the chordwise direction (117).

3. Locating the vertical rotor (118) upstream of the airfoil (102), i.e., near the leading edge (108), maximizes drag reduction; The drag force is generated so as to act in the propulsion direction, The lift assembly (300) of claim 1, wherein the lift to drag ratio is greatest at the aft wing portion (102).

4. The lift assembly (300) of claim 1, wherein the lift force increases linearly as the throttle of the vertical rotor (118) increases from 0% to 100%.

5. 2. The lift assembly (300) of claim 1, wherein the increased lift allows the wings (102) to be smaller, thus reducing drag experienced for a given payload.

6. 2. The lift assembly of claim 1, wherein a lift coefficient of the lift assembly at an optimal position of the vertical rotor is higher when the vertical rotor is in motion during forward flight of the aircraft.

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