Unmanned aerial vehicle propelling system and design method thereof

Abstract

The invention provides an unmanned aerial vehicle propelling system and a design method thereof. The unmanned aerial vehicle propelling system comprises a duct, a mounting base, a rotation driving part, a propeller disc and a plurality of guide vanes. The mounting seat is arranged in the center of the duct, the guide vanes are uniformly radiated from the mounting seat to the inner wall of the duct, the rotary driving part is arranged on the mounting seat, and the propeller disc is connected to the output end of the rotary driving part and located on the side, close to a duct lip, of the mounting seat; the lip of the duct inclines towards the direction of the mounting base, and the guide vanes are arranged in a twisting mode. The flow guide blades are arranged in a twisting manner, so that a paddle disc can be efficiently rectified to rotate and slip flow, rotational flow kinetic energy is recycled, and kinetic energy waste is reduced; the duct lip is inclined towards the mounting seat and is cooperatively matched with the torsion guide vane, so that duct inlet airflow is smoothly linked with the rectification effect, airflow interference and resistance are reduced, the thrust efficiency of a propulsion system is effectively improved, and the requirements of high endurance and high force efficiency of the unmanned aerial vehicle are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of unmanned aerial vehicle power systems, and more particularly to an unmanned aerial vehicle propulsion system and a design method thereof. BACKGROUND

[0002] With the rapid development of unmanned aerial vehicle technology, its application in the fields of logistics distribution, geographic mapping, agricultural plant protection, security inspection, etc. is becoming increasingly widespread, and the market has put forward more stringent requirements for the endurance, flight efficiency and stability of unmanned aerial vehicles. The duct-based propulsion system has become one of the core power solutions for small and medium-sized rotor unmanned aerial vehicles due to its high thrust density, compact structure and good running safety, and has been widely used in the industry.

[0003] A typical ducted propulsion system mainly comprises a duct, a mounting seat located at the center of the duct, a rotating drive member assembled on the mounting seat, a paddle connected to the output end of the rotating drive member, and guide vanes connecting the mounting seat and the inner wall of the duct. The working principle is as follows: the rotating drive member drives the paddle to rotate at high speed to directly generate the main flight thrust; the duct wall can constrain the tip vortex of the paddle to reduce the tip energy loss; and the core function of the guide vanes is to aerodynamically straighten the rotational slipstream generated after the paddle rotates, eliminate the airflow vortex, convert the rotational flow energy into axial thrust, and simultaneously bear the structural function of connecting and supporting the central mounting seat.

[0004] However, in the design of the existing ducted propulsion system, the aerodynamic function of the guide vanes is seriously ignored, and they lack targeted optimization with the duct. In the traditional design concept, the guide vanes are only regarded as structural supports, and their geometric parameters are often determined based on engineering experience or simple linear rules, for example, straight blade structures are commonly used, which cannot efficiently eliminate airflow rotation and cause a large amount of rotational flow energy waste; at the same time, the duct lip design is also in a conventional form, such as a simple long cylindrical shape, which is not adapted to the straightening requirements of the guide vanes, resulting in isolated design of the two, and further making the straightening effect of the duct inlet airflow and the guide vanes unable to connect, further intensifying airflow interference and resistance, and ultimately significantly restricting the overall thrust efficiency of the ducted propulsion system, which is difficult to meet the use requirements of unmanned aerial vehicles for high endurance and high efficiency. SUMMARY

[0005] The present application aims to overcome the defects of the prior art and provide an unmanned aerial vehicle propulsion system and a design method thereof to solve the technical problems of the lack of aerodynamic function of the guide vanes and the insufficient cooperation with the duct.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions: In a first aspect, the present application provides a UAV propulsion system, comprising: a duct, a mounting seat, a rotating drive, a paddle disc and a plurality of guide vanes; the mounting seat is arranged at the center of the duct, the plurality of guide vanes are uniformly radiated from the mounting seat to the inner wall of the duct, the rotating drive is arranged on the mounting seat, the paddle disc is connected to the output end of the rotating drive and located on the side of the mounting seat close to the lip of the duct; the lip of the duct is inclined to the mounting seat, and the guide vanes are arranged in a twisted manner.

[0007] Further, the inclination angle of the lip of the duct is 8°.

[0008] Further, the airfoil of the duct is geo570, and the length of the duct is 15 mm.

[0009] Further, the chord length of the guide vane decreases linearly from the end close to the mounting seat to the end close to the duct.

[0010] Further, the chord length of the end of the guide vane close to the mounting seat is 12 mm, and the chord length of the end of the guide vane close to the duct is 8 mm.

[0011] Further, the airfoil of the guide vane is NACA 2424, the twist angle of the end of the guide vane close to the mounting seat is 15°, and the twist angle of the end of the guide vane close to the duct is 0°.

[0012] Further, the airfoil of the guide vane is EPP 864, the twist angle of the end of the guide vane close to the mounting seat is 20°, and the twist angle of the end of the guide vane close to the duct is 5°.

[0013] Further, the ratio of the length of the duct to the diameter of the paddle disc is 0.1-0.2, the axial distance between the upper edge of the paddle disc and the edge of the lip of the duct is 5 mm, and the gap between the guide vanes and the paddle disc is 2 mm.

[0014] Further, a plurality of blades are arranged on the paddle disc, the gap between the end of the blade away from the paddle disc and the inner side wall of the duct is 0.5-1 mm, and the number of the guide vanes and the number of the blades are prime to each other.

[0015] In a second aspect, the present application provides a design method of a UAV propulsion system, which is used to design the UAV propulsion system as described above, and the design method of the UAV propulsion system comprises: The parameterized model is imported into fluid simulation software, a target flight working condition is set, flow field analysis is carried out, and total thrust T and total absorbed power P of the propelling system are calculated; The parameterized model is imported into fluid simulation software, a target flight working condition is set, flow field analysis is carried out, and total thrust T and total absorbed power P of the propelling system are calculated; The parameterized model is imported into fluid simulation software, a target flight working condition is set, flow field analysis is carried out, and total thrust T and total absorbed power P of the propelling system are calculated; The parameterized model is imported into fluid simulation software, a target flight working condition is set, flow field analysis is carried out, and total thrust T and total absorbed power P of the propelling system are calculated;

[0016] The beneficial effects of the present application compared with the prior art are: the present application can efficiently straighten the rotating slip stream behind the paddle by twisting the guide vane, recover the rotational kinetic energy and reduce the kinetic energy waste; by tilting the lip of the duct towards the mounting seat and cooperatively adapting with the twisted guide vane, the airflow at the inlet of the duct and the straightening effect are smoothly connected, the airflow interference and resistance are reduced, the propelling system thrust efficiency is effectively improved, and the high endurance and high force efficiency requirements of the unmanned aerial vehicle are met.

[0017] The above description is only a summary of the technical solutions of the present application, in order to more clearly understand the technical means of the present application, the content of the specification can be implemented, and in order to make the above and other purposes, characteristics and advantages of the present application more obvious and easy to understand, the following preferred embodiments are described in detail as follows. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 A schematic diagram of the overall structure of the unmanned aerial vehicle propelling system provided by the present application is shown in the figure; Figure 2 A schematic diagram of the overall structure of the unmanned aerial vehicle propelling system provided by the present application is shown in the figure; Figure 3 A schematic diagram of the overall structure of the unmanned aerial vehicle propelling system provided by the present application is shown in the figure; Figure 2 A schematic diagram of the overall structure of the unmanned aerial vehicle propelling system provided by the present application is shown in the figure; Figure 4 A CFD wake flow field cloud diagram of the unmanned aerial vehicle propelling system of embodiment one is shown in the figure; Figure 5 A CFD wake flow field cloud diagram of the unmanned aerial vehicle propelling system of embodiment one is shown in the figure; Figure 6 A CFD wake flow field cloud diagram of the unmanned aerial vehicle propelling system of embodiment one is shown in the figure; Figure 7 CFD tip flow field cloud chart of the prior art; Figure 8 A flowchart of a design method of an unmanned aerial vehicle propulsion system provided by the present application.

[0019] Reference signs: 1, duct; 11, guide surface; 12, protrusion; 13, converging surface; 2, mounting seat; 3, paddle disc; 31, paddle blade; 4, guide vane. DETAILED DESCRIPTION

[0020] In order to make the objectives, technical solutions and advantages of the present application clearer, further detailed description will be given to the present application in combination with the accompanying drawings and specific embodiments. The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0021] It should be understood that, when used in the specification and the appended claims, the terms “comprise” and “include” indicate the presence of described features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0022] It should also be understood that the terms used in the present application specification are only for the purpose of describing specific embodiments and are not intended to limit the present application. As used in the present application specification and the appended claims, unless otherwise clearly indicated by the context, the singular forms “a”, “an” and “the” are intended to include the plural forms as well.

[0023] It should be further understood that the term “and / or” used in the present application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0024] Embodiment one Reference Figures 1 to 3As shown, the embodiment discloses a UAV propulsion system, which comprises: a duct 1, a mounting seat 2, a rotating drive (not shown), a paddle disc 3 and a plurality of guide vanes 4; the mounting seat 2 is arranged at the center of the duct 1, the plurality of guide vanes 4 are uniformly radiated from the mounting seat 2 to the inner wall of the duct 1, the rotating drive is arranged on the mounting seat 2, the paddle disc 3 is connected to the output end of the rotating drive and located on the side of the mounting seat 2 close to the lip of the duct 1; the lip of the duct 1 is inclined to the mounting seat 2, and the guide vanes 4 are arranged in a twisted manner.

[0025] The UAV propulsion system of the embodiment can efficiently straighten the rotating slip stream behind the paddle disc 3, recover the rotational kinetic energy and reduce the waste of kinetic energy by arranging the guide vanes 4 in a twisted manner; by inclining the lip of the duct 1 to the mounting seat 2 and cooperatively adapting the twisted guide vanes 4, the airflow at the inlet of the duct 1 and the straightening effect are smoothly connected, the airflow interference and resistance are reduced, the thrust efficiency of the propulsion system is effectively improved, and the high endurance and high force efficiency requirements of the UAV are met.

[0026] It can be understood that the lip of the duct 1 refers to the edge of the inlet of the duct 1; the guide vanes 4 are uniformly radiated from the mounting seat 2 to the inner wall of the duct 1, that is, the guide vanes 4 are uniformly distributed in a radial manner with the mounting seat 2 as the center and connected to the inner wall of the duct 1. More specifically, the plurality of guide vanes 4 are circumferentially distributed on the mounting seat 2, and the guide vanes 4 extend along the radial direction of the duct 1, and the two ends thereof are respectively fixed to the mounting seat 2 and the side of the duct 1 away from the lip. In specific implementation, the rotating drive drives the paddle disc 3 to rotate to generate thrust, the airflow enters the duct 1 from the inclined lip of the duct 1, the paddle disc 3 forms a rotating slip stream after rotation, the twisted guide vanes 4 straighten the slip stream, and guide the airflow to flow in the axial direction.

[0027] Preferably, the rotating drive is a brushless motor. The brushless motor has no mechanical commutation friction, high energy conversion efficiency and light weight, can improve the force efficiency and thrust-to-weight ratio of the propulsion system, and meets the design goal of high force efficiency and light weight of the system; and it has small running vibration, long service life and controllable rotating speed, can ensure the smoothness of the flow field, adapt to the multi-working-condition operation of the UAV, and can improve the reliability and flight stability of the system.

[0028] Further, the inner side wall of the duct 1 is sequentially provided with a guide surface 11, a protrusion 12 and a contraction surface 13 from the lip side to the other side. The guide surface 11 is inclined from the lip edge of the duct 1 to the mounting base 2, and the contraction surface 13 is inclined from the protrusion 12 away from the mounting base 2 and the lip side. The thickness of the protrusion 12 is greater than the distance between the guide surface 11 and the outer side wall of the duct 1, and greater than the distance between the contraction surface 13 and the outer side wall of the duct 1. After the airflow enters from the lip of the duct 1, it is guided by the guide surface 11 to flow towards the mounting base 2, adjusts the flow direction after encountering the protrusion 12, and then flows out of the duct 1 through the contraction surface 13. The protrusion 12 restricts the airflow from diffusing too early. The arrangement of the guide surface 11, the protrusion 12 and the contraction surface 13 optimizes the airflow path in the duct 1, reduces airflow separation and turbulence, and improves airflow smoothness, creating favorable conditions for the coordinated flow guiding of the duct 1 and the guide vane 4.

[0029] Further, the lip of the duct 1 has an inclination angle of 8°. The inclination angle α of the lip of the duct 1 refers to the angle between the plane where the lip edge of the duct 1 is located and the guide surface 11. An inclination angle of 8° reduces the airflow resistance at the inlet of the duct 1 and gently guides the external airflow into the duct 1, avoiding impact or separation of the airflow due to an excessively large angle.

[0030] Further, the airfoil of the duct 1 is geo570. The airfoil of the duct 1 refers to the shape of the cross section of the duct 1. The cross section with the geo570 airfoil adapts to the flow characteristics of the airflow in the duct 1, reducing friction resistance and separation phenomena of the airflow on the inner wall of the duct 1.

[0031] Further, the length of the duct 1 is 15 mm. It can be understood that the length L of the duct 1 refers to the axial distance from the lip edge to the other edge (outlet side) of the duct 1. A length of 15 mm ensures a compact structure while providing sufficient space for airflow flow and component installation; and the length of 15 mm of the duct 1 cooperates with the geo570 airfoil, making the duct 1 consider both lightweight and aerodynamic performance, avoiding excessive length of the duct 1 leading to increased weight, solving the technical problem of traditional long duct 1 design for pursuing aerodynamic efficiency, and making the duct 1 too heavy to reduce the power system thrust-to-weight ratio and efficiency.

[0032] Further, the ratio of the length of the duct 1 to the diameter of the rotor disc 3 is 0.1-0.2. The ratio L / D of the length L of the duct 1 to the diameter D of the rotor disc 3 refers to the proportion of the axial length of the duct 1 to the maximum rotating diameter of the rotor disc 3, wherein the maximum rotating diameter of the rotor disc 3 is the tip track diameter of the rotor blade 31. L / D is 0.1-0.2, which makes the length of the duct 1 adapt to the size of the rotor disc 3, and the airflow generated by the rotor disc 3 can flow fully in the duct 1, ensuring the restraining and guiding effect of the duct 1 on the airflow of the rotor disc 3, considering both lightweight and aerodynamic efficiency, and avoiding improper ratio leading to thrust loss or weight increase.

[0033] Preferably, the ratio of the length of the duct 1 to the diameter of the paddle disc 3 is 0.15. The L / D of 0.15 makes the length of the duct 1 more matched with the size of the paddle disc 3, the flow path of the airflow in the paddle disc 3 in the duct 1 is more optimal, the constraint guidance of the airflow by the duct 1 is more accurate, further improves the coordination performance of the duct 1 and the paddle disc 3, reduces airflow turbulence and energy loss, and is more conducive to improving the thrust efficiency.

[0034] Further, the axial distance between the upper edge of the paddle disc 3 and the lip edge of the duct 1 is 5mm, and the gap between the guide vane 4 and the paddle disc 3 is 2mm. It can be understood that the axial distance δ between the upper edge of the paddle disc 3 and the lip edge of the duct 1 refers to the distance between the edge of the paddle disc 3 close to the lip side edge and the lip edge of the duct 1 in the axial direction of the duct 1; the gap ε between the guide vane 4 and the paddle disc 3 refers to the axial distance between the edge of the guide vane 4 close to the paddle disc 3 and the paddle disc 3. The axial distance δ of 5mm makes the paddle disc 3 in the reasonable action area of the inlet airflow of the duct 1; the gap ε of 2mm makes the paddle disc 3 rear rotating slipstream quickly reach the guide vane 4, which is convenient for timely rectification. Together, it avoids the airflow impact or thrust loss caused by improper distance between the paddle disc 3 and the lip, ensures the timeliness of the rectification of the guide vane 4, and further reduces the waste of kinetic energy.

[0035] Further, the paddle disc 3 is provided with a plurality of blades 31, and the gap between the end of the blade 31 away from the paddle disc 3 and the inner side wall of the duct 1 is 0.5-1mm. The plurality of blades 31 are arranged in the axial direction of the paddle disc 3 and extend in the radial direction of the duct 1. The gap between the end of the blade 31 away from the paddle disc 3 and the inner side wall of the duct 1 refers to the radial distance between the tip of the blade 31 and the inner side wall of the duct 1, and the gap of 0.5-1mm reduces the airflow leakage when the blade 31 rotates, avoids excessive diffusion of tip vortex, and improves the thrust efficiency of the paddle disc 3.

[0036] Further, the number of guide vanes 4 and the number of blades 31 are prime numbers. The prime number design of the number of guide vanes 4 and the number of blades 31 avoids resonance caused by frequency superposition when they operate, ensures the structural stability and airflow smoothness of the unmanned aerial vehicle propulsion system, and prolongs the service life of the components.

[0037] Preferably, the number of blades 31 is three, and the number of guide vanes 4 is five. The three blades 31 generate thrust, the five guide vanes 4 uniformly support the mounting seat 2 and rectify the slipstream, the number of the two is a prime number, which avoids the risk of resonance, ensures the stability of the thrust output of the paddle disc 3, the guide vanes 4 support uniformly and have good rectification effect, and improves the stability of the system operation.

[0038] Preferably, the diameter of the paddle disc 3 is 4 inches. It can be understood that the diameter of the paddle disc 3 is the diameter of the circular track formed by the tip of the blade 31 when rotating, and the 4-inch diameter is suitable for small and medium-sized unmanned aerial vehicles, and the ratio of the length of the duct 1 to the diameter of the paddle disc 3 is 0.1-0.2, which can effectively cut the airflow when the blade 31 rotates to generate sufficient thrust, avoid the size being too large to cause the weight or energy consumption to rise, and balance the thrust demand and lightweight design.

[0039] Further, the chord length of the guide vane 4 linearly decreases from the end close to the mounting base 2 to the end close to the duct 1. The chord length of the guide vane 4 refers to the straight-line distance between the leading edge and the trailing edge of the cross section of the blade. It can be understood that the chord length of the guide vane 4 uniformly decreases with the increase of the radial distance from the center of the duct 1 from the root (the end close to the mounting base 2) to the tip (the end close to the duct 1). The speed and intensity of the slipstream behind the paddle disc 3 gradually change from the center to the outside, and the linearly decreasing chord length makes the cross-sectional size of the blade at each position adapt to the corresponding airflow characteristics, improving the flow regulation adaptability of the guide vane 4 to different radial slipstreams, avoiding local over-regulation or under-regulation caused by uniform chord length, and reducing airflow resistance.

[0040] Further, the chord length of the guide vane 4 close to the mounting base 2 is 12 mm, and the chord length of the guide vane 4 close to the duct 1 is 8 mm. It can be understood that the ratio of the tip chord length (the chord length close to the duct 1) to the root chord length (the chord length close to the mounting base 2) of the guide vane 4, i.e. the chord length ratio, is 0.67. The 12 mm root chord length ensures the structural strength of the guide vane 4 and the flow regulation ability of the central strong slipstream, the 8 mm tip chord length adapts to the weak slipstream outside, and the 0.67 chord length ratio meets the airflow characteristic gradient. The chord length setting of the guide vane 4 ensures the structural stability of the guide vane 4 while accurately adapting to the radial distribution of the slipstream behind the paddle, improving the flow regulation efficiency and reducing energy loss.

[0041] Further, the twist angle of the guide vane 4 linearly decreases from the end close to the mounting base 2 to the end close to the duct 1. The twist angle of the guide vane 4 refers to the angle between the airfoil chord line of the guide vane 4 at different radial positions and the reference plane (such as the vertical plane of the duct 1 axis); linearly decreasing means that the twist angle uniformly decreases with the increase of the radial distance from the center of the duct 1 from the root of the guide vane 4 to the tip. It can be understood that the rotation angle of the slipstream behind the paddle disc 3 gradually changes from the center to the outside, and the linearly decreasing twist angle makes the wing angle at each position of the blade match the corresponding slipstream rotation angle, which can accurately adjust the slipstream to axial airflow, realize point-by-point accurate flow regulation of the slipstream behind the paddle, and maximize the elimination of airflow rotation, converting the rotational kinetic energy of the slipstream into axial thrust and reducing kinetic energy waste.

[0042] Further, the airfoil of the guide vane 4 is NACA 2424, the twist angle of the end of the guide vane 4 close to the mounting base 2 is 15°, and the twist angle of the end of the guide vane 4 close to the duct 1 is 0°. The symmetrical airfoil of NACA 2424 has similar aerodynamic characteristics under positive and negative attack angles, and is more versatile, and is suitable for conventional scenarios that need to consider multiple flight states. Under the NACA 2424 airfoil, the root twist angle of the guide vane 4 can be set to 15°, and the tip twist angle is 0°. Among them, the 15° root twist angle adapts to the central strong rotating slipstream, and the 0° tip twist angle adapts to the weak rotating slipstream on the outside, realizes smooth transition, efficiently converts the rotational flow kinetic energy into axial thrust, and further improves the efficiency of the propulsion system.

[0043] As can be seen from the above, the present embodiment improves the thrust-to-weight ratio through the multi-parameter collaborative optimization of the positions of the duct 1, the guide vane 4 and the paddle disc 3, eliminates the design isolation problem of each component, and realizes the performance optimization at the system level. Through actual measurement verification, the weight of the propulsion system of the present embodiment is 1 / 3 of the traditional design, and the force efficiency (thrust / power) under the typical hovering working condition is improved by 15% to 30% compared with the traditional experience design of the propulsion system. Among them, the traditional design is that the duct 1 is a simple long cylindrical shape, and the guide vane 4 is a straight blade with equal chord length and no twist. The lightweight of the duct 1 and the large improvement of the force efficiency mean that more thrust can be generated under the consumption of the same battery power, or less power is consumed under the generation of the same thrust, so that the endurance time of the unmanned aerial vehicle carrying the propulsion system is significantly prolonged, and the task ability and practicality of the unmanned aerial vehicle are improved. In addition, the optimized collaborative design can effectively suppress the flow separation inside the duct 1, weaken the strength of the blade tip vortex and hub vortex, and make the flow field after the guide vane 4 more uniform and smooth, not only reducing energy dissipation, but also helping to reduce aerodynamic noise and vibration, and improving the flight quality and reliability of the unmanned aerial vehicle.

[0044] Embodiment Two Referring to Figures 1 to 3 As shown in the drawings, the present embodiment discloses an unmanned aerial vehicle propulsion system, which is different from the unmanned aerial vehicle propulsion system of embodiment one in that the airfoil of the guide vane 4 is EPP 864, the twist angle of the end of the guide vane 4 close to the mounting base 2 is 20°, and the twist angle of the end of the guide vane 4 close to the duct 1 is 5°. In order to ensure efficient rectification of the rotating slipstream after the paddle.

[0045] It can be understood that the asymmetric airfoil of EPP 864 is optimized for the fixed attack angle of the propulsion system under the cruising state, and can achieve higher aerodynamic efficiency under this specific working condition, such as medium speed forward flight working condition. The 20° root twist angle of the guide vane 4 of the present embodiment deals with the central area rotating slipstream, and the 5° tip twist angle adapts to the outside slipstream, both of which cooperate to convert the slipstream into axial flow, maintaining the high thrust efficiency of the propulsion system.

[0046] Embodiment three The existing design method of unmanned aerial vehicle propulsion system often regards the duct, the paddle disc and the guide vane as independent components for isolated or sequential optimization. For example, the paddle blade is designed first, then a duct is matched for it, and finally the guide vane is simply added as a structural support. This design method ignores the strong aerodynamic coupling effect between the components. The combination of components without collaborative optimization not only cannot achieve the effect of “1+1>2”, but also may cause performance degradation due to flow interference, resulting in additional resistance, vortex and thrust loss. Moreover, for the key parameters such as the profile of the duct, the inlet angle, the length, the relative position of the paddle disc and the lip, and the axial distance between the guide vane and the paddle disc, the existing technology often uses empirical values or imitates existing designs, and lacks systematic optimization research for specific flight conditions (such as hovering and forward flight). The non-ideal duct design will cause inlet flow separation and increase resistance; the inappropriate relative position of the paddle-duct will change the pressure distribution inside the duct and affect the thrust contribution efficiency of the duct. Therefore, the embodiment discloses a design method of an unmanned aerial vehicle propulsion system.

[0047] Specifically, referring to Figure 8 The design method of the unmanned aerial vehicle propulsion system of the embodiment is used for designing the unmanned aerial vehicle propulsion system of the embodiment one or the embodiment two, and includes the following steps S1-S4.

[0048] S1: a three-dimensional drawing software is used to construct a parameterized model; wherein the parameters of the parameterized model include: the airfoil, the inlet angle and the length of the duct, the airfoil, the chord length and the twist angle of the guide vane, the diameter of the paddle disc, and the axial distance between the upper edge of the paddle disc and the edge of the duct lip and the gap between the guide vane and the paddle disc; and the objective function of the parameterized model is η=F / (M*ω), wherein η is the paddle force efficiency, F is the thrust of the propulsion system, M is the torque, and ω is the rotating speed of the rotating driving member.

[0049] For the step S1, the objective function is the paddle force efficiency, that is, η=F / (M*ω), which represents the thrust that can be generated per unit power g / W. It can be understood that, according to the engineering practice and the ideal propeller theory, the factors affecting the efficiency under the condition of the determined rotating speed are the thrust and the torque. The paddle disc thrust is related to the flow velocity, the paddle disc solidity, the paddle disc area, the paddle blade airfoil, the twist, the chord length distribution and the sweep, etc. The embodiment is aimed at the collaborative optimization of the duct guide vane, so the parameters of the paddle disc are determined. As for the duct, due to the design of the lip angle, the paddle disc will generate additional thrust when hovering. Under the assumption of ideal fluid, incompressibility and no viscosity, the additional thrust of the duct can be derived by pressure integration on the inner and outer surfaces of the duct. The mathematical expression is usually as follows: Tduct=ρ*Vi²*Ad*CT,duct / 2; Or more specifically, the integral form is: Tduct=∮duct surface(p-p∞)*dAx; Where CT, duct is the duct thrust coefficient, a dimensionless parameter, which comprehensively reflects the influence of duct profile, angle of attack, lip shape, etc. on the additional thrust efficiency. This parameter is determined by the duct inner surface pressure distribution, the angle of attack of the incoming flow, and the distance between the duct and the propeller. Vi is the induced velocity at the propeller disc, with a unit of m / s; Ad is the maximum cross-sectional area or characteristic area of the duct, with a unit of m²; ρ is the air density, with a unit of kg / m³; surface is the duct surface, which includes the inner surface of the duct and the outer surface of the duct, and surface (p-p∞) quantifies the pressure contribution of each point on the duct surface relative to the environment; p is the static pressure at a certain point on the duct surface, with a unit of Pa; p∞ is the static pressure of the incoming flow far ahead, with a unit of Pa, serving as a reference benchmark. The pressure difference p-p∞ is used in the integration of surface to reflect the aerodynamic effect. If p>p∞ at a certain point on surface, the region produces positive pressure, contributing to the thrust; if p<p∞, it produces resistance or loss; dAx is the component of the duct surface infinitesimal area in the thrust direction, i.e. the axial direction, with a unit of m².

[0050] The guide vane design is based on the stator angular momentum conservation theorem and the blade element momentum theorem. The torque Q0 exerted by the propeller on the airflow is related to the change in angular momentum of the airflow, i.e. ; Where, is the mass flow rate, with a unit of kg / s; r is the radial position, with a unit of m; Vθ is the tangential velocity of the airflow, with a unit of m / s; Δ is the change in angular momentum of the airflow before and after passing through the propeller.

[0051] Downstream of the propeller disc and propeller blades, the airflow has a strong tangential velocity Vθ,inlet. The role of the guide vane is to produce a counter-torque to straighten this part of rotational kinetic energy.

[0052] The counter-torque Q produced by the guide vane is: ; Under ideal conditions, after passing through the guide vane, the outlet airflow has almost no rotation, i.e. Vθ,outlet≈0.

[0053] Therefore, the formula can be simplified as: Qstator≈m˙rVθ,inlet; Wherein, Qstator is the resistance moment of the propeller, the resistance moment of the propeller is also the torque of the propeller, both are the torque generated by the propeller when rotating due to the action of air resistance, which is the driving source torque for the rotating motion of the air flow, and this torque is the torque that the motor needs to provide, which is the main component of the system power consumption, and the counter-torque Q generated by the guide vane is to offset the propeller torque Qstator.

[0054] The counter-torque Q generated by the guide vane offsets part of the resistance moment Qstator of the propeller, which means that the torque that the motor needs to provide is reduced, thereby reducing the total power P of the system.

[0055] The guide vane is essentially a static airfoil, and its aerodynamic performance can be modeled using airfoil theory.

[0056] The lift dL and drag dD acting on each element can be estimated by the following model: dL = pV2cCldr / 2; Wherein, c is the chord length of the guide vane, that is, the straight line distance between the leading edge and the trailing edge of the cross section of the guide vane; Cl is the lift coefficient, which is an aerodynamic parameter of the guide vane airfoil, reflecting the ability of the airfoil to generate lift at a certain angle of attack, and in specific implementation, the value of Cl can be optimized through simulation to ensure high lift-drag ratio in hover or forward flight conditions; dr is the radial micro-element length, which is the small segment length of the guide vane in the radial direction, used for integral calculation of the lift dL of the entire guide vane.

[0057] According to the above derivation, the research on the propulsion system can be carried out by setting local parameters to solve local optimal solution through theoretical derivation and simulation numerical simulation, and then analyzing the optimal solution.

[0058] S2: Import the parameterized model into the fluid simulation software, set the target flight condition, carry out flow field analysis, and calculate the total thrust T and total power P absorbed by the propulsion system.

[0059] For step S2, ANSYS Fluent can be used as a fluid simulation software for CFD numerical simulation in specific implementation, and the parameterized model constructed by SOLIDWORKS three-dimensional drawing software in step S1 is imported; then, the target flight condition is set, such as hover condition, medium speed forward flight condition, etc.; the flow field analysis needs to focus on simulating the airflow flow trajectory in the duct, the vortex distribution at the blade tip, and the straightening process of the guide vane to the rotating slipstream behind the propeller, and at the same time, combining the duct additional thrust formula Tduct=∮duct surface(p-p∞)*dAx in S1 with the guide vane counter-torque formula Qstator≈m˙rVθ,inlet, the total thrust T and the total power P absorbed by the propulsion system are accurately calculated to ensure that the data match the subsequent optimization target.

[0060] S3: With the optimization goal of maximizing the propeller efficiency η = T / P, determine the parameters of the parameterized model with the greatest impact on aerodynamic effects through fluid simulation software simulation, measure the corresponding thrust, torque and power data of the parameters of the remaining parameterized models through the test bench, and adjust and optimize the parameterized model according to the measured data feedback.

[0061] For step S3, the fluid simulation software still uses ANSYS Fluent, and the parameters with the greatest impact on aerodynamic effects are simulated first. By comparing the flow field smoothness and force efficiency data under different parameters, the optimal range of such parameters is locked. The remaining parameters are measured by a physical test bench, that is, the propeller system prototype is fixed on the test bench, the rotating drive speed is controlled to be stable, the thrust sensor and torque sensor are used to collect the thrust F and torque M under different parameter combinations, the total power P is calculated according to the power calculation formula, and the parameterized model is adjusted according to the measured η = T / P data feedback. For example, if the force efficiency under a certain ratio of duct length to propeller diameter does not meet the expectation, the ratio is fine-tuned to 0.15 to ensure that the model parameters meet the actual performance requirements.

[0062] S4: Screen the parameter combination that makes the propeller efficiency η reach the local optimum, and output the unmanned aerial vehicle propeller system model.

[0063] For step S4, combined with the simulation and measured data of S3, the optimal parameter combination is screened according to the target working condition. After screening is completed, the three-dimensional entity model corresponding to the parameter combination can be exported using SOLIDWORKS, with a parameter list and a CFD flow field verification report, forming a propeller system design file that can be directly used for machining or prototype manufacturing, ensuring that the output model can reproduce the optimal force efficiency and flow field performance.

[0064] The following is a reference example of the design method for the UAV propulsion system in this embodiment: In the parametric modeling stage, the following parameters are input: maximizing propeller efficiency η=F / (M*ω), duct (geo570 airfoil, length L=15mm, lip tilt angle α=8°, ratio to rotor disk diameter D=0.1-0.2), rotor disk (4-inch diameter, 3 blades, blade tip-to-duct clearance 0.5-1mm), guide vanes (5 blades, NACA 2424 airfoil, root chord length 12mm, tip chord length 8mm, root twist angle 15°, tip twist angle 0°), and relative positions (rotor disk-to-lip axial distance δ=5mm, guide vane-to-rotor disk clearance ε=2mm). SOLIDWORKS is specified for modeling. In the CFD numerical simulation stage, hovering conditions and air density (e.g., atmospheric pressure) are input, and ANSYS is specified. Fluent simulation was used to calculate the total thrust T and total power P. In the collaborative optimization stage, the priority of maximizing force efficiency and aerodynamic sensitive parameters (such as wingtip clearance and guide vane airfoil) were input. CFD verification and other parameter measurement feedback were used to limit collaborative constraints such as the number of coprime blades. In the optimal solution determination stage, the optimal parameters matching the UAV propulsion system of Example 1 were screened.

[0065] To verify the effectiveness of the designed UAV propulsion system, under the same CFD settings and hovering conditions, the UAV propulsion system of Example 1 was compared with a conventional design. The conventional design uses a simple elongated cylindrical duct and straight, non-twisted blades of equal chord length. Simulation results show that the UAV propulsion system of Example 1 achieves a force efficiency of 9.9 g / W, while the conventional control design achieves 7.9 g / W. The force efficiency improvement reaches 25.3%. See also... Figure 4 and Figure 5 ,as well as Figure 6 and Figure 7 The flow field analysis cloud maps show that the optimized system has a smoother internal flow field and a significantly reduced vortex intensity behind the propeller disk, confirming the effectiveness of the synergistic optimization. Furthermore, the UAV propulsion system in Example 2 exhibits optimal performance under medium-speed forward flight conditions.

[0066] The above examples are merely illustrative of the technical content of the present invention to facilitate easier understanding by the reader, but do not imply that the implementation of the present invention is limited to these examples. Any technical extensions or re-creations made based on the present invention are protected by the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A drone propulsion system, characterized in that, include: The duct comprises a mounting base, a rotating drive unit, a propeller disk, and several guide vanes. The mounting base is located at the center of the duct, and the several guide vanes radiate evenly from the mounting base to the inner wall of the duct. The rotating drive unit is mounted on the mounting base, and the propeller disk is connected to the output end of the rotating drive unit and located on the side of the mounting base near the duct lip. The duct lip is inclined towards the mounting base, and the guide vanes are twisted.

2. The unmanned aerial vehicle propulsion system according to claim 1, characterized in that, The lip angle of the culvert is 8°.

3. The unmanned aerial vehicle propulsion system according to claim 1, characterized in that, The duct has a geo570 airfoil and a length of 15 mm.

4. The unmanned aerial vehicle propulsion system according to claim 1, characterized in that, The chord length of the guide vane decreases linearly from the end near the mounting base to the end near the duct.

5. The unmanned aerial vehicle propulsion system according to claim 4, characterized in that, The chord length of the guide vane near the mounting base is 12mm, and the chord length of the guide vane near the duct is 8mm.

6. The unmanned aerial vehicle propulsion system according to claim 1, characterized in that, The airfoil of the guide vane is NACA2424, the twist angle of the guide vane near the mounting base is 15°, and the twist angle of the guide vane near the duct is 0°.

7. The unmanned aerial vehicle propulsion system according to claim 1, characterized in that, The airfoil of the guide vane is EPP864, the twist angle of the guide vane near the mounting base is 20°, and the twist angle of the guide vane near the duct is 5°.

8. The unmanned aerial vehicle propulsion system according to claim 1, characterized in that, The ratio of the length of the duct to the diameter of the propeller disk is 0.1-0.2, the axial distance between the upper edge of the propeller disk and the edge of the duct lip is 5mm, and the gap between the guide vane and the propeller disk is 2mm.

9. The unmanned aerial vehicle propulsion system according to claim 1, characterized in that, The propeller disk is provided with a number of blades, and the gap between the end of the blade away from the propeller disk and the inner wall of the duct is 0.5-1mm; the number of guide vanes and the number of propeller blades are coprime numbers.

10. A design method for an unmanned aerial vehicle (UAV) propulsion system, used to design an UAV propulsion system as described in any one of claims 1-9, characterized in that, include: A parametric model is constructed using 3D modeling software. The parameters of the parametric model include: the airfoil, inlet inclination angle, and length of the duct; the airfoil, chord length, and twist angle of the guide vanes; the diameter of the propeller disk; the axial distance between the upper edge of the propeller disk and the edge of the duct lip; and the clearance between the guide vanes and the propeller disk. The objective function of the parametric model is η=F / (M*ω), where η is the propeller force efficiency, F is the thrust of the propulsion system, M is the torque, and ω is the rotational speed of the rotating drive component. The parameterized model is imported into fluid simulation software, the target flight conditions are set, flow field analysis is carried out, and the total thrust T and total power P absorbed by the propulsion system are calculated. With the optimization objective of maximizing propeller force efficiency η=T / P, the parameters of the parametric model with the greatest impact on aerodynamic effects are determined by fluid simulation software. The thrust, torque and power data corresponding to the parameters of the other parametric models are measured by test bench. The parametric models are adjusted and optimized based on the feedback from the measured data. The parameter combination that makes the propeller efficiency η locally optimal is selected, and the UAV propulsion system model is output.

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