Multi-working-condition multifunctional propeller inverse design method
By combining eddy current theory with multi-objective optimization in an inverse design method, the problem of performance balance in propeller design under multiple operating conditions was solved, enabling the integrated tail thrust propeller of rotary-wing UAVs to work efficiently in helicopter and fixed-wing modes, thus improving design efficiency and aerodynamic performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-18
- Publication Date
- 2026-04-03
AI Technical Summary
Existing propeller design methods struggle to achieve performance balance under various operating conditions. Traditional methods have long design cycles and rely on the initial shape, failing to meet the aerodynamic requirements of integrated tail thrust propellers for rotary-wing UAVs in both helicopter and fixed-wing modes.
A reverse design framework based on eddy current theory and multi-objective optimization is adopted. By using a partitioned weighted optimization strategy, the chord length distribution and torsion angle distribution of the propeller are designed in a coordinated manner to achieve performance balance under multiple operating conditions.
It improves design efficiency and robustness, reduces dependence on the initial shape, and makes the design process more direct and efficient. The propeller can meet the thrust requirements in both operating conditions, and the aerodynamic efficiency decreases slightly but less than that of a simple compromise solution, achieving a good performance balance.
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Figure CN121786964A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aircraft propeller design, specifically a multi-condition, multi-functional propeller inverse design method. Background Technology
[0002] Vertical takeoff and landing (VTOL) aircraft, possessing multiple flight capabilities including "fast, slow, and stationary," have become a research hotspot in the aviation field. Among them, rotary-wing unmanned aerial vehicles (UAVs) combine the VTOL capabilities of helicopters with the high-speed cruise advantages of fixed-wing aircraft, exhibiting excellent mission adaptability. However, in practical applications, these aircraft still face problems such as insufficient acceleration performance and the large weight of the tail rotor system (i.e., "tail rotor dead weight"). To alleviate these problems, an integrated tail rotor and thrust rotor can be used to replace the traditional tail rotor, allowing the same rotor system to provide high thrust as a tail rotor in helicopter mode and forward thrust as a thrust rotor in fixed-wing mode. This requires the rotor to operate efficiently in two distinctly different conditions: in helicopter mode (low advance ratio), sufficient thrust is needed to maintain flight balance; in fixed-wing mode (high advance ratio), high aerodynamic efficiency is required to improve flight performance.
[0003] Currently, propeller design methods mainly fall into two categories: single-condition optimization design and traditional inverse design. Single-condition optimization methods typically optimize the aerodynamic shape for a specific operating condition. While this can achieve relatively good performance under that condition, the design process is often lengthy and computationally intensive, and the optimization results heavily depend on the initial shape selection, lacking robustness. When a propeller needs to operate under multiple conditions, single-condition optimization methods struggle to simultaneously meet the aerodynamic requirements of different conditions, usually requiring compromises that result in suboptimal performance across all conditions.
[0004] While traditional inverse design methods can deduce blade shape from a given aerodynamic target, they are usually limited to a single design state and lack an effective mechanism for comprehensive consideration of multiple operating conditions. Especially in the design of large-span dual-operating conditions (low advance ratio and high advance ratio) involving integrated tail thruster propellers, traditional inverse design methods struggle to achieve synergistic optimization among multiple objectives such as thrust and efficiency, often resulting in compromises and failing to meet the stringent requirements for multi-operating condition adaptability in practical engineering.
[0005] In summary, existing propeller design methods mainly suffer from the following technical problems: single-condition optimization methods have long design cycles, rely on the initial shape, and cannot effectively take into account the aerodynamic performance requirements under multiple conditions; traditional reverse design methods lack multi-objective collaborative optimization mechanisms, making it difficult to achieve performance balance across different conditions over a large span; and for tail-thrust integrated propellers of vertical take-off and landing aircraft such as rotary-wing UAVs, there is currently a lack of a design method that can systematically and efficiently meet the dual requirements of helicopter and fixed-wing modes simultaneously.
[0006] Therefore, there is an urgent need to propose a propeller design method that can adapt to multiple operating conditions, has a clear reverse design process, and can achieve performance trade-offs and optimization between two operating conditions, so as to improve the overall aerodynamic efficiency and flight performance of this type of aircraft. Summary of the Invention
[0007] To overcome the technical shortcomings of existing propeller design methods, such as long optimization cycles for single-condition operation, reliance on initial shape, and the difficulty of traditional inverse design in meeting the requirements of multiple operating conditions, this invention proposes a multi-condition, multi-functional propeller inverse design method. This method employs an inverse design framework combining eddy current theory (strip theory) and multi-objective optimization. Through a partitioned weighted optimization strategy, it collaboratively designs the chord length distribution and twist angle (installation angle) distribution of the propeller, thereby achieving performance balance under dual operating conditions. This method is particularly suitable for scenarios such as integrated propellers for rotary-wing UAVs that require efficient operation in both helicopter mode (low advance ratio) and fixed-wing mode (high advance ratio), and can simultaneously meet the aerodynamic performance requirements of a wide range of operating conditions.
[0008] The technical solution of this invention is as follows:
[0009] A multi-condition, multi-functional propeller inverse design method includes the following steps:
[0010] Step 1: Input the basic propeller parameters and dual-condition design requirements. The basic parameters include the propeller disk radius R, propeller speed n, and number of blades. The dual-condition design requirement includes the inflow velocity of the first condition. With required tensile force and the incoming flow velocity in the second operating condition With required tensile force ;
[0011] Step 2: Discretize the spanwise region of the propeller blades from the hub to the tip into multiple blade elements, and calculate the Lagrange multiplier of the propeller under the first and second operating conditions respectively. and ;
[0012] Step 3: Based on the single-condition inverse design method, select at least one design station within the load core range of the blade, and calculate the first installation angle of the design station under the first and second conditions respectively. Second installation angle and according to Determine the pitch angle of the propeller ;
[0013] Step 4: For each leaf element i except for the designed station, repeat the following steps to determine the design dimensionless chord length corresponding to leaf element i. and design installation angle :
[0014] Step 4.1: Calculate the installation angle of leaf element i under the first and second operating conditions. , Induced angle of attack , and the local actual Mach number , ;
[0015] Step 4.2: Determine the airfoil shape corresponding to blade element i based on the preset blade thickness distribution;
[0016] Step 4.3: Within the preset range of values for the dimensionless chord length b, for each assumed chord length... Execute the following sub-steps:
[0017] Step 4.3.1: Calculate leaf element i under the assumed chord length Below are the Reynolds numbers corresponding to the first and second operating conditions, respectively. , ;
[0018] Step 4.3.2: Obtain the aerodynamic data of the selected airfoil under the local actual Mach number, Reynolds number, and angle of attack corresponding to the first and second operating conditions, respectively, and utilize the variable pitch angle. Establish the angle of attack correlation between the first and second operating conditions, and characterize the aerodynamic data of both the first and second operating conditions as a function expression of the angle of attack corresponding to a certain operating condition;
[0019] Step 4.3.3: Based on the radial position relative to leaf element i The corresponding weighting coefficients and design objectives are used to weight the aerodynamic data for the first and second operating conditions, and the favorable angle of attack for the first operating condition is obtained based on the weighted evaluation results. Favorable angle of attack for the second operating condition ;
[0020] Step 4.3.4: Based on the strip theory, calculate the angle of attack at the favorable angle of attack. and and the current assumed chord length Below, in order to meet the required tensile force and The theoretical basis for each element i requires dimensionless chord length. and ;
[0021] Step 4.4: Repeat step 4.3 to find a chord length value from the range of dimensionless chord length b. This means that the theoretical calculation based on this chord length value requires a dimensionless chord length. and If the overall error between the chord length value and the chord length value meets the preset conditions, then the chord length value is taken as the dimensionless chord length of the leaf element i. Simultaneously, based on the favorable angle of attack corresponding to this chord length value... or and in combination with the installation angle or The design and installation angle of leaf element i were obtained. ;
[0022] Step 5: Integrate the design results of all blade elements to obtain the chord length distribution curve and installation angle distribution curve of the propeller, thus completing the propeller reverse design.
[0023] Furthermore, in step 2, the Lagrange multiplier... and The equations are obtained by using an integral equation based on eddy current theory and by solving them using numerical integration and iterative methods.
[0024] Furthermore, in step 3, the load core region is the blade spanwise region where the thrust contribution on the blade is not less than 90% of the maximum thrust contribution value; the relative radial position of the design station. It is located within the core region of the load.
[0025] Furthermore, in step 4.3.2, the variable pitch angle is utilized. The angle of attack relationship between the first and second operating conditions is established as follows:
[0026]
[0027] in For the second operating condition, angle of attack. The angle of attack for the first operating condition.
[0028] Furthermore, in step 4.3.3, the weighted processing of the aerodynamic data for the first and second operating conditions is as follows:
[0029] According to the formula
[0030]
[0031] Obtain the weighted lift coefficient Weighted drag coefficient Weighted lift-to-drag ratio ;in , and The aerodynamic data for the selected airfoil under the first operating condition are the local actual Mach number, Reynolds number, and angle of attack. , and The aerodynamic data for the airfoil selected in step 4.2 at the local actual Mach number, Reynolds number, and angle of attack under the second operating condition are: and For weighted values, and and The sum is 1.
[0032] Furthermore, the first operating condition is a high forward ratio operating condition in which the propeller acts as the thrust rotor of a fixed-wing aircraft, and the second operating condition is a low forward ratio operating condition in which the propeller acts as the tail rotor of a helicopter.
[0033] Furthermore, in step 4.3.3, the weighting coefficients are based on the relative radial position of leaf element i. Determine: The closer the blade element is to the blade tip, the higher its weight corresponds to the first operating condition. The higher the value, the greater the weight of the blade element near the blade root, corresponding to the second operating condition. The higher.
[0034] Furthermore, in step 4.4, the preset condition is to make The value is the smallest.
[0035] Furthermore, in step 4.1, the installation angle of leaf element i under the first and second working conditions. , for:
[0036] φ () [ ]
[0037] in This represents the propeller's forward ratio under the first and second operating conditions.
[0038] Furthermore, in step 4.1, the induced angle of attack of leaf element i under the first and second operating conditions. , for:
[0039] .
[0040] Beneficial effects
[0041] The beneficial effects of this invention are as follows:
[0042] This invention realizes multi-condition collaborative design. By introducing a partitioned weighted optimization strategy, it integrates the different aerodynamic requirements of two conditions into a unified design process, overcoming the shortcomings of traditional methods that are difficult to take into account large-span conditions. Furthermore, this invention improves design efficiency and robustness. Based on an explicit reverse design process, it reduces the dependence of traditional optimization methods on the initial shape and the long iteration cycle, making the design process more direct and efficient.
[0043] Implementation examples show that the propeller (prop3) designed using the method of this invention can meet the rated thrust requirements in both thrust propeller mode and tail propeller mode. Although its aerodynamic efficiency is slightly lower than that of a dedicated design for a single operating condition (prop1 or prop2), the decrease is significantly smaller than that of a simple compromise solution, achieving a good performance balance under both operating conditions.
[0044] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description
[0045] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:
[0046] Figure 1 Flowchart of multi-condition propeller inverse design method;
[0047] Figure 2 : Blade element velocity / mechanical polygon at point r under eddy current theory;
[0048] Figure 3 : Propeller blade tension distribution curve;
[0049] Figure 4 Propeller blade thickness distribution;
[0050] Figure 5 : Installation angle distribution curve generated by variable pitch;
[0051] Figure 6 Installation angle distribution curve generated by dual-condition design;
[0052] Figure 7 Chord length distribution curves of single / dual working condition design results;
[0053] Figure 8 : Single / dual operating condition design results; (a) Design result prop1 (single thrust propeller operating condition design), (b) Design result prop2 (single tail propeller operating condition design), (c) Design result prop3 (dual operating condition design). Detailed Implementation
[0054] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.
[0055] like Figure 1 As shown in this embodiment, a multi-condition, multi-functional propeller inverse design method includes the following steps:
[0056] Step 1: Input the basic propeller parameters and dual-condition design requirements. The basic parameters include the propeller disk radius R, propeller speed n, and number of blades. The dual-condition design requirement includes the inflow velocity of the first condition. With required tensile force and the incoming flow velocity in the second operating condition With required tensile force Based on the above input parameters, the installation angle and chord length distribution of the propeller are designed.
[0057] In this embodiment, the first operating condition is a high forward ratio operating condition in which the propeller is used as the thrust rotor of a fixed-wing aircraft, and the second operating condition is a low forward ratio operating condition in which the propeller is used as the tail rotor of a helicopter.
[0058] Step 2: Divide the spanwise section of the blade from the hub to the tip into... Section, then The Lagrange multiplier of the propeller under the first and second operating conditions is obtained by solving an integral equation based on eddy current theory using numerical integration and iterative methods. and .
[0059] Step 3: To address the design challenges posed by long-span applications, a design station is selected within the load core region of the blade, based on a single-condition inverse design method. The load core region is the spanwise region of the blade where the thrust contribution is no less than 90% of the maximum thrust contribution. The relative radial position of the design station... It is located within the core region of the load.
[0060] In this embodiment, the relative radial position of the selected design station ,in The distance between the design station and the propeller hub. Figure 2 As can be seen from this, the core region with a larger tensile force distribution is... This refers to the area where the thrust is not less than 90% of the maximum value. The design station should be located within this range, while the main distribution range of propeller load is... The median value of this interval is Therefore, in order to effectively balance the requirements under different working conditions at the propeller root, the relative radial position of the design station is taken. .
[0061] Then, using the single-condition inverse design method, the first installation angle of the design station under the first condition and the second condition is calculated respectively. Second installation angle and according to Determine the pitch angle of the propeller .
[0062] Step 4: For each leaf element i except for the designed station, repeat the following steps to determine the design dimensionless chord length corresponding to leaf element i. and design installation angle :
[0063] Step 4.1: Calculate the installation angle of leaf element i under the first and second operating conditions. , Induced angle of attack , and the local actual Mach number , ;
[0064] The installation angle of leaf element i under the first and second working conditions. , for:
[0065] φ () [ ]
[0066] in This represents the propeller's forward ratio under the first and second operating conditions. ; The relative radial position of leaf element i.
[0067] Based on the installation angle of leaf element i under the first and second working conditions , The induced angle of attack of leaf element i under the first and second operating conditions , for:
[0068]
[0069] Local actual Mach number , for:
[0070]
[0071] In the formula, , For the local actual synthesis speed , Dimensionless parameters.
[0072] Step 4.2: Determine the airfoil shape corresponding to blade element i based on the preset blade thickness distribution.
[0073] According to the preset blade thickness distribution (e.g.) Figure 4As shown in the figure, the corresponding airfoil is assigned to the i-th blade element. A fixed airfoil family can be scaled according to the thickness distribution, or a preset variable airfoil database can be directly read. That is, the airfoil of each bay is pre-designed and the data is matched one by one. During the design process, the corresponding airfoil data is directly read according to the relative position.
[0074] Step 4.3: At the preset dimensionless chord length ( Within the range of values for the chord length, for each assumed dimensionless chord length... The following sub-steps are then executed. This is the key loop of the invention, designed to find a chord length value for leaf element i that optimally or suboptimally satisfies the tension requirements of both working conditions simultaneously. In this embodiment, the dimensionless chord length b ranges from 0.01 to 0.21, with a variation step of 0.01.
[0075] Step 4.3.1: Calculate leaf element i under the assumed chord length Below are the Reynolds numbers corresponding to the first and second operating conditions, respectively. , :
[0076]
[0077] Step 4.3.2: Using aerodynamic calculation software (such as Xfoil), obtain the aerodynamic data of the selected airfoil under the local actual Mach number, Reynolds number, and angle of attack corresponding to the first and second operating conditions, including lift coefficient, drag coefficient, and lift-to-drag ratio, and use the aforementioned pitch angle... Establish the angle of attack correlation between the first and second operating conditions, so that the aerodynamic data of both the first and second operating conditions can be represented as a function expression of the angle of attack corresponding to a certain operating condition.
[0078] Using aerodynamic calculation software, the aerodynamic data of the selected airfoil in step 4.2 at the local actual Mach number, Reynolds number, and angle of attack under the first and second operating conditions can be calculated, and the aerodynamic data can be normalized to obtain... , and as well as , and Since the actual installation angle is different for each leaf element position, the variable pitch angle is used. The angle of attack relationship between the first and second operating conditions is established as follows:
[0079]
[0080] in For the second operating condition, angle of attack. Let be the angle of attack for the first operating condition. Then, the local actual Mach number, Reynolds number, and normalized aerodynamic data for the airfoil selected in step 4.2 at the second operating condition are: , and Therefore, the aerodynamic parameters under both operating conditions can be transformed into parameters related to... The function.
[0081] Step 4.3.3: During propeller design, the requirements and weights for different operating conditions vary at different locations. The root and tip of the propeller do not bear the main load, so the primary design objective is to reduce drag. In the middle section, the lift-to-drag ratio is calculated using a weighted average. Therefore, based on the radial position relative to blade element i... The corresponding weighting coefficients and design objectives are used to weight the aerodynamic data for the first and second operating conditions, and the favorable angle of attack for the first operating condition is obtained based on the weighted evaluation results. Favorable angle of attack for the second operating condition .
[0082] The weighted processing of the aerodynamic data for the first and second operating conditions is as follows:
[0083] According to the formula
[0084]
[0085] Obtain the weighted lift coefficient Weighted drag coefficient Weighted lift-to-drag ratio ; and For weighted values, and and The sum is 1. Based on the above function, all parameters are transformed into unified indicators and unified variables, so the optimal data corresponding to the design objective can be selected. As the current leaf element has a favorable angle of attack in the first operating condition Then, based on the angle of attack correlation between the first and second operating conditions, the favorable angle of attack for the current blade element in the second operating condition is obtained. .
[0086] Furthermore, the weighting coefficients and design objectives are based on the relative radial position of leaf element i. Determine: The closer the blade element is to the blade tip, the higher its weight corresponds to the first operating condition. The higher the value, the greater the weight of the blade element near the blade root, corresponding to the second operating condition. The higher. As shown in Table 1:
[0087] Table 1 Weighted Design Objectives and Parameters
[0088]
[0089] Step 4.3.4: Based on the strip theory, calculate the angle of attack at the favorable angle of attack. and and the current assumed chord length Below, in order to meet the required tensile force and The theoretical basis for each element i requires dimensionless chord length. and :
[0090]
[0091] in and Favorable angle of attack for the first operating condition The corresponding lift coefficient and drag coefficient, and Favorable angle of attack for the second operating condition The corresponding lift coefficient and drag coefficient.
[0092] Step 4.4: Adjust the dimensionless chord length b according to the set step size, and repeat step 4.3 to find a chord length value from the range of values for the dimensionless chord length b. This means that the theoretical calculation based on this chord length value requires a dimensionless chord length. and The overall error between the chord length value and the chord length value satisfies a preset condition, wherein the preset condition is to make If the value is the smallest, then this chord length value is taken as the dimensionless chord length of the leaf element i. Simultaneously, based on the favorable angle of attack corresponding to this chord length value... or and in combination with the installation angle or The design and installation angle of leaf element i were obtained. Take this as an example. Of course, you can also take it. .
[0093] Step 5: Iteratively calculate the design dimensionless chord length and design installation angle of each blade element, integrate the design results of all blade elements, obtain the chord length distribution curve and installation angle distribution curve of the propeller, and complete the propeller reverse design.
[0094] The following design of the propeller is based on the above method, and the different requirements of the propeller under the dual working conditions of the long span are shown in Table 2.
[0095] Table 2 Propeller Design Requirements
[0096]
[0097] Based on the overall design requirements, the following propeller parameter data has been initially selected:
[0098] Due to structural design limitations, the propeller disk diameter was selected to be 25 inches, based on the layout constraints of the rotary-wing UAV. As the propeller speed increases, the tip Mach number increases linearly. To ensure the tip Mach number does not exceed 0.7 Mach, the propeller speed was set at 6700 rpm. This embodiment designs a tail-thrust integrated propeller with two blades. A comprehensive comparison was made of the RAF6 airfoil, Clark-Y airfoil, and ARA-D airfoil. The ARA-D airfoil exhibits excellent lift-drag characteristics and good stall characteristics, which perfectly matches the design requirements of this tail-thrust integrated propeller. Its propeller thickness distribution is as follows... Figure 4 As shown.
[0099] The installation angle distribution curves are obtained based on traditional single-condition and dual-condition design methods, such as... Figure 5 , Figure 6 As shown; and the relative chord length distribution curve is obtained, as shown. Figure 7 As shown. Based on this, three propeller designs were obtained: single thrust propeller design result prop1, single tail propeller design result prop2, and dual-condition design prop3, as follows. Figure 8 As shown.
[0100] Numerical simulations were performed using computational fluid dynamics to obtain the aerodynamic parameters of the propeller under dual operating conditions, as shown in Tables 3 and 4.
[0101] Table 3. Propeller simulation results (tail rotor mode)
[0102]
[0103] Table 3 shows that, except for the design result prop1 for the thrust propeller mode, the other two propellers can meet the thrust design requirement of 139 N. Regarding efficiency, compared to the efficiency of the design result prop2 for the tail rotor mode, prop1's force efficiency decreased by 0.052 g / N, while the force efficiency of the design result obtained using the dual-condition design method only decreased by 0.016 g / N. The verification results for the tail rotor mode indicate that the dual-condition propeller design method reduces efficiency somewhat while ensuring thrust requirements, but the degree of reduction is small.
[0104] Table 4. Propeller simulation results (thrust propeller mode)
[0105]
[0106] Table 4 shows that all three propeller design results meet the thrust design requirement of 130N. However, there are significant differences in efficiency. Compared to prop1, the single-condition design result for the thrust propeller mode, the efficiency of prop2 for the tail propeller mode is reduced by 3.56%. Furthermore, the efficiency of prop3, obtained using the dual-condition design method, is reduced by 1.87% compared to prop1. The verification results for the thrust propeller mode further demonstrate that the dual-condition propeller design method, while ensuring the thrust requirement, does reduce efficiency, but the reduction is relatively small.
[0107] In summary, the propeller (prop3) designed using the method of this invention can meet the rated thrust requirements in both thrust propeller mode and tail propeller mode. Although its aerodynamic efficiency is slightly lower than that of a dedicated design for a single operating condition (prop1 or prop2), the decrease is significantly smaller than that of a simple compromise solution, achieving a good performance balance under both operating conditions.
[0108] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.
Claims
1. A multi-condition, multi-functional propeller inverse design method, characterized in that: Includes the following steps: Step 1: Input the basic propeller parameters and dual-condition design requirements. The basic parameters include the propeller disk radius R, propeller speed n, and number of blades. The dual-condition design requirement includes the inflow velocity of the first condition. With required tensile force and the incoming flow velocity in the second operating condition With required tensile force ; Step 2: Discretize the spanwise region of the propeller blades from the hub to the tip into multiple blade elements, and calculate the Lagrange multiplier of the propeller under the first and second operating conditions respectively. and ; Step 3: Based on the single-condition inverse design method, select at least one design station within the load core range of the blade, and calculate the first installation angle of the design station under the first and second conditions respectively. Second installation angle and according to Determine the pitch angle of the propeller ; Step 4: For each leaf element i except for the designed station, repeat the following steps to determine the design dimensionless chord length corresponding to leaf element i. and design installation angle : Step 4.1: Calculate the installation angle of leaf element i under the first and second operating conditions. , Induced angle of attack , and the local actual Mach number , ; Step 4.2: Determine the airfoil shape corresponding to blade element i based on the preset blade thickness distribution; Step 4.3: Within the preset range of values for the dimensionless chord length b, for each assumed chord length... Execute the following sub-steps: Step 4.3.1: Calculate leaf element i under the assumed chord length Below are the Reynolds numbers corresponding to the first and second operating conditions, respectively. , ; Step 4.3.2: Obtain the aerodynamic data of the selected airfoil under the local actual Mach number, Reynolds number, and angle of attack corresponding to the first and second operating conditions, respectively, and utilize the variable pitch angle. Establish the angle of attack correlation between the first and second operating conditions, and characterize the aerodynamic data of both the first and second operating conditions as a function expression of the angle of attack corresponding to a certain operating condition; Step 4.3.3: Based on the radial position relative to leaf element i The corresponding weighting coefficients and design objectives are used to weight the aerodynamic data for the first and second operating conditions, and the favorable angle of attack for the first operating condition is obtained based on the weighted evaluation results. Favorable angle of attack for the second operating condition ; Step 4.3.4: Based on the strip theory, calculate the angle of attack at the favorable angle of attack. and and the current assumed chord length Below, in order to meet the required tensile force and The theoretical basis for each element i requires dimensionless chord length. and ; Step 4.4: Repeat step 4.3 to find a chord length value from the range of dimensionless chord length b. This means that the theoretical calculation based on this chord length value requires a dimensionless chord length. and If the overall error between the chord length value and the chord length value meets the preset conditions, then the chord length value is taken as the dimensionless chord length of the leaf element i. Simultaneously, based on the favorable angle of attack corresponding to this chord length value... or and in combination with the installation angle or The design and installation angle of leaf element i were obtained. ; Step 5: Integrate the design results of all blade elements to obtain the chord length distribution curve and installation angle distribution curve of the propeller, thus completing the propeller reverse design.
2. The multi-condition, multi-functional propeller reverse design method according to claim 1, characterized in that: In step 2, the Lagrange multiplier and The equations are obtained by using an integral equation based on eddy current theory and by solving them using numerical integration and iterative methods.
3. The multi-condition, multi-functional propeller reverse design method according to claim 1, characterized in that: In step 3, the load core region is the spanwise region of the blade where the thrust contribution on the blade is not less than 90% of the maximum thrust contribution value; the relative radial position of the design station. It is located within the core region of the load.
4. The multi-condition, multi-functional propeller reverse design method according to claim 1, characterized in that: In step 4.3.2, the variable pitch angle is used. The angle of attack relationship between the first and second operating conditions is established as follows: in For the second operating condition, angle of attack. The angle of attack for the first operating condition.
5. The multi-condition, multi-functional propeller reverse design method according to claim 4, characterized in that: In step 4.3.3, the weighted processing of the aerodynamic data for the first and second operating conditions is as follows: According to the formula Obtain the weighted lift coefficient Weighted drag coefficient Weighted lift-to-drag ratio ;in , and The aerodynamic data for the selected airfoil under the first operating condition are the local actual Mach number, Reynolds number, and angle of attack. , and The aerodynamic data for the airfoil selected in step 4.2 at the local actual Mach number, Reynolds number, and angle of attack under the second operating condition are: and For weighted values, and and The sum is 1.
6. The multi-condition, multi-functional propeller reverse design method according to claim 5, characterized in that: The first operating condition is a high forward ratio condition in which the propeller is used as the thrust rotor of a fixed-wing aircraft, and the second operating condition is a low forward ratio condition in which the propeller is used as the tail rotor of a helicopter.
7. The multi-condition, multi-functional propeller inverse design method according to claim 6, characterized in that: In step 4.3.3, the weighting coefficients are based on the relative radial position of leaf element i. Determine: The closer the blade element is to the blade tip, the higher its weight corresponds to the first operating condition. The higher the value, the greater the weight of the blade element near the blade root, corresponding to the second operating condition. The higher.
8. The multi-condition, multi-functional propeller reverse design method according to claim 1, characterized in that: In step 4.4, the preset condition is to make The value is the smallest.
9. The multi-condition, multi-functional propeller reverse design method according to claim 1, characterized in that: In step 4.1, the installation angle of leaf element i under the first and second working conditions. , for: in This represents the propeller's forward ratio under the first and second operating conditions.
10. The multi-condition, multi-functional propeller inverse design method according to claim 1, characterized in that: In step 4.1, the induced angle of attack of leaf element i under the first and second operating conditions. , for: 。