A rapid prediction method for the aerodynamic performance of small propellers

Abstract

This invention belongs to the field of performance calculation technology for small model aircraft propulsion systems, specifically relating to a rapid prediction method for the aerodynamic performance of small propellers. The method includes the following steps: Step 1, determining the propeller's external dimensions and calculation conditions; Step 2, calculating the aerodynamic performance of the airfoil; Step 3, calculating the aerodynamic performance of the blades; Step 4, making corrections to the hub and the fuselage leading up to the propeller to finally obtain the aerodynamic performance of the small propeller. This invention calculates the aerodynamic performance of the propeller blades based on eddy current theory, and incorporates empirical calculations of the hub's aerodynamic performance and corrections for interference in the fuselage leading up to the propeller. This allows for rapid and accurate acquisition of the propeller's actual aerodynamic performance, providing data support for the overall design iteration of small UAVs and model aircraft.

Description

Technical Field

[0001] This invention belongs to the field of performance calculation technology for small model aircraft power systems, specifically relating to a method for rapid prediction of aerodynamic performance applicable to small propellers. Background Technology

[0002] Currently, propellers, as a simple and technologically mature power unit, are widely used in the propulsion power of small model aircraft. The aerodynamic performance of the propeller determines the efficiency of the propulsion system and even affects the overall performance of the model aircraft. Therefore, for propeller-driven propulsion systems of small model aircraft, the ability to quickly and accurately calculate aerodynamic performance is of great significance for propeller shape optimization, propeller-engine matching design, and the improvement of the overall performance of the model aircraft.

[0003] There are currently two main methods for calculating propeller performance: engineering algorithms and numerical simulation. Engineering algorithms can quickly evaluate blade performance, but they cannot simulate hub performance or interference from the propeller's forward fuselage. The propeller hub generates drag and torque upon rotation, resulting in decreased overall thrust and increased torque, both of which reduce propeller efficiency. The forward fuselage reduces the propeller's frontal area, further impacting thrust. Therefore, ignoring the interference from the propeller hub and forward fuselage leads to overly optimistic performance assessments during optimization, resulting in a final model aircraft propulsion system that does not achieve the optimized efficiency.

[0004] Numerical simulation can be used to perform high-precision calculations of propeller aerodynamic performance, hub performance, and the interference effects of the propeller's forward fuselage. However, numerical simulation requires mesh generation and RANS or large eddy simulation iterative calculations for different optimized blade shapes, hub shapes, and forward fuselage shapes, which consumes significant computational resources and time. Therefore, a faster and more convenient calculation method is needed to quickly evaluate propeller performance during the propeller optimization design phase. Summary of the Invention

[0005] (a) Technical problems to be solved

[0006] The technical problem to be solved by this invention is: in order to improve the accuracy and speed of propeller power system performance evaluation in the early stage of overall design of small electric propulsion UAVs and model aircraft, how to provide a rapid prediction method for the aerodynamic performance of small propellers.

[0007] (II) Technical Solution

[0008] To address the aforementioned technical problems, this invention provides a method for rapidly predicting the aerodynamic performance of small propellers, the method comprising the following steps:

[0009] Step 1: Determine the external dimensions of the propeller and the calculation conditions;

[0010] Step 2: Calculate the aerodynamic performance of the airfoil;

[0011] Step 3: Calculate the aerodynamic performance of the blades;

[0012] Step 4: Make corrections to the hub and the fuselage before the propeller to finally obtain the aerodynamic performance of the small propeller.

[0013] In step one, determining the external dimensions of the propeller and the calculation conditions involves the following steps:

[0014] Step 1.1: Based on the three-dimensional digital model of the propeller and the blade design documents, determine the spanwise position, airfoil type, chord length, and installation angle of multiple sections along the spanwise direction.

[0015] Step 1.2: Determine the calculation parameters based on the calculation task, including flight altitude, flight speed, and propeller rotation speed.

[0016] In step 1.1, according to the blade design documents, the blade is divided into N sections along the spanwise direction, and the relative positions of each station are given. absolute position r i Airfoil type, chord length b i and installation angle ψ i The data matrix, and the number of propeller blades N B Propeller diameter D lxj The axial windward area S1 of the propeller hub, the circumferential windward area S2 of the propeller hub, and the diameter D of the propeller inlet fuselage. ds , where i represents the i-th cross section, i = 1, 2, 3...N.

[0017] In step 1.2, the flight altitude H, flight speed V, and propeller rotation speed ω are determined according to the calculation task to prepare parameters for subsequent calculations.

[0018] In step two, calculating the aerodynamic performance of the airfoil involves the following steps:

[0019] Step 2.1: Estimate the Reynolds number range during use based on the propeller's flight speed, rotational speed, and chord length of each section;

[0020] Step 2.2: Using numerical calculation software, accurately calculate the aerodynamic performance of each airfoil within the Reynolds number range in Step 2.1.

[0021] In step 2.1, the Reynolds number Re is calculated for each cross-section of the blade. i The expression is (1):

[0022]

[0023] Where ρ and μ are the atmospheric density and viscosity coefficients at flight altitude H; U i Let U be the vector sum of the airfoil rotational velocity and the propeller flight velocity at the i-th cross-section; since the rapid aerodynamic performance prediction method is aimed at the preliminary design stage, it does not consider the case where there is an angle between the propeller thrust axis and the flight direction. Therefore, the propeller rotational speed direction and the flight velocity direction are orthogonal. i The expression is (2):

[0024]

[0025] In step 2.2, aerodynamic data for different Reynolds numbers is obtained by generating meshes and performing RANS numerical simulations on each airfoil. This includes lift coefficients and drag coefficients for different Reynolds numbers and angles of attack, forming an airfoil aerodynamic performance table. The Reynolds number does not need to correspond one-to-one with the one calculated in step 2.1; it only needs to include the entire range. When finally used, the actual Reynolds number and angle of attack can be interpolated.

[0026] In step three, calculating the aerodynamic performance of the blades, the steps are as follows:

[0027] Step 3.1: Calculate the circumferential velocity, geometric angle of attack, and solidity of each cross-section;

[0028] Step 3.2: Determine the angle of attack correction for each cross-section based on eddy current theory;

[0029] Step 3.3: Determine the aerodynamic performance parameters for each cross section, including thrust coefficient and torque coefficient;

[0030] Step 3.4: Based on the aerodynamic data from Step 3.3, integrate to obtain the aerodynamic performance of the blade.

[0031] In step 3.1, the circumferential velocity at each cross-section... Geometric angle of attack Reality σ i The expressions are equations (3), (4), and (5):

[0032]

[0033]

[0034]

[0035] In step 3.2, the angle of attack correction α′ for each cross-section is determined based on eddy current theory. i The steps are as follows:

[0036] Assume the angle of attack correction at the i-th section is Then the angle of attack θ at that section i The calculation expression is given by equation (6):

[0037]

[0038] Based on the airfoil aerodynamic performance table obtained in step 2.2, interpolation calculations are performed to obtain the airfoil aerodynamic performance at an angle of attack of θ. i The Reynolds number is Re i Lift coefficient Cl at time i and drag coefficient Cd i ;

[0039] Finally, based on α in eddy current theory... i The angle-of-attack correction α′ for each cross section is obtained by using the Newton-Raphson equation and the iteration calculation. i The calculation expression is shown in equation (7):

[0040]

[0041] In step 3.3, the corrected velocity U′ at each cross section is calculated. i The calculation expression is given by equation (8):

[0042]

[0043] Thrust T at each section i and torque Q i The expressions are given by equations (9) and (10):

[0044]

[0045]

[0046] In step 3.4, the thrust and torque of the blade are obtained by integration, and the calculated expressions are equations (11) and (12):

[0047]

[0048]

[0049] In step four, the hub and the fuselage in front of the propeller are modified to obtain the aerodynamic performance of the small propeller.

[0050] The thrust and torque of the propeller blades are corrected for the hub, which is simplified here. After the hub rotates, it will generate a certain amount of resistance and torque. The resistance will reduce the thrust of the propeller, and the torque will increase the torque of the propeller, thus reducing the efficiency of the propeller to a certain extent. Therefore, the influence of the hub cannot be ignored. Based on the experience of numerical simulation, the resistance generated by the hub is estimated using formula (13), and the torque is estimated using formula (14).

[0051]

[0052]

[0053] In the formula: S1 is the axial windward area of ​​the propeller hub, in dm². 2 S2 is the circumferential windward area of ​​the propeller hub, in dm². 2 This completes the correction of the propeller hub;

[0054] The steps of the correction method for the propeller-forward fuselage are as follows: The cross-sectional area of ​​the propeller-forward fuselage blocks the radial range of the propeller. It is assumed that the thrust generated at the blocked location is zero, while the torque remains unchanged; therefore, the thrust value T generated within this range is calculated. 遮挡 Subtracting this from the aerodynamic performance of the entire propeller completes the correction of the fuselage in front of the propeller; finally, the thrust T and torque Q of the small propeller are obtained, and the calculation expressions are Equations (15) and (16).

[0055] T = T p -T 桨毂 -T 遮挡 (15)

[0056] Q = Q p +Q 桨毂 (16).

[0057] (III) Beneficial Effects

[0058] To improve the accuracy and speed of propeller power system performance evaluation in the early stages of overall design for small electric propulsion UAVs and model aircraft, this invention proposes a rapid aerodynamic performance prediction method suitable for small propellers. Compared with existing technologies, this invention calculates the aerodynamic performance of propeller blades based on eddy current theory and incorporates empirical calculations of hub aerodynamic performance and corrections for propeller-forward fuselage interference. This allows for rapid and accurate acquisition of the actual aerodynamic performance of the propeller, providing data support for the iterative overall design of small UAVs and model aircraft. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the propeller's shape.

[0060] Figure 2 This is a diagram showing the distribution of propeller chord length and installation angle.

[0061] Figure 3 This is a schematic diagram of the blade element velocity triangle of a propeller cross section.

[0062] Figure 4 This is a comparison chart of the propeller thrust calculation results.

[0063] Figure 5 This is a comparison chart of the propeller torque calculation results. Detailed Implementation

[0064] To make the objectives, contents, and advantages of the present invention clearer, the specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0065] To address the aforementioned technical problems, this invention provides a method for rapidly predicting the aerodynamic performance of small propellers, the method comprising the following steps:

[0066] Step 1: Determine the external dimensions of the propeller and the calculation conditions;

[0067] Step 2: Calculate the aerodynamic performance of the airfoil;

[0068] Step 3: Calculate the aerodynamic performance of the blades;

[0069] Step 4: Make corrections to the hub and the fuselage before the propeller to finally obtain the aerodynamic performance of the small propeller.

[0070] In step one, determining the external dimensions of the propeller and the calculation conditions involves the following steps:

[0071] Step 1.1: Based on the three-dimensional digital model of the propeller and the blade design documents, determine the spanwise position, airfoil type, chord length, and installation angle of multiple sections along the spanwise direction.

[0072] Step 1.2: Determine the calculation parameters based on the calculation task, including flight altitude, flight speed, and propeller rotation speed.

[0073] In step 1.1, according to the blade design documents, the blade is divided into N sections along the spanwise direction, and the relative positions of each station are given. absolute position r i Airfoil type, chord length b i and installation angle ψ i The data matrix, and the number of propeller blades N B Propeller diameter D lxj The axial windward area S1 of the propeller hub, the circumferential windward area S2 of the propeller hub, and the diameter D of the propeller inlet fuselage. ds, where i represents the i-th cross section, i = 1, 2, 3...N.

[0074] In step 1.2, the flight altitude H, flight speed V, and propeller rotation speed ω are determined according to the calculation task to prepare parameters for subsequent calculations.

[0075] In step two, calculating the aerodynamic performance of the airfoil involves the following steps:

[0076] Step 2.1: Estimate the Reynolds number range during use based on the propeller's flight speed, rotational speed, and chord length of each section;

[0077] Step 2.2: Using numerical calculation software, accurately calculate the aerodynamic performance of each airfoil within the Reynolds number range in Step 2.1.

[0078] In step 2.1, the Reynolds number Re is calculated for each cross-section of the blade. i The expression is (1):

[0079]

[0080] Where ρ and μ are the atmospheric density and viscosity coefficients at flight altitude H; U i Let U be the vector sum of the airfoil rotational velocity and the propeller flight velocity at the i-th cross-section; since the rapid aerodynamic performance prediction method is aimed at the preliminary design stage, it does not consider the case where there is an angle between the propeller thrust axis and the flight direction. Therefore, the propeller rotational speed direction and the flight velocity direction are orthogonal. i The expression is (2):

[0081]

[0082] In step 2.2, aerodynamic data for different Reynolds numbers is obtained by generating meshes and performing RANS numerical simulations on each airfoil. This includes lift coefficients and drag coefficients for different Reynolds numbers and angles of attack, forming an airfoil aerodynamic performance table. The Reynolds number does not need to correspond one-to-one with the one calculated in step 2.1; it only needs to include the entire range. When finally used, the actual Reynolds number and angle of attack can be interpolated.

[0083] In step three, calculating the aerodynamic performance of the blades, the steps are as follows:

[0084] Step 3.1: Calculate the circumferential velocity, geometric angle of attack, and solidity of each cross-section;

[0085] Step 3.2: Determine the angle of attack correction for each cross-section based on eddy current theory;

[0086] Step 3.3: Determine the aerodynamic performance parameters for each cross section, including thrust coefficient and torque coefficient;

[0087] Step 3.4: Based on the aerodynamic data from Step 3.3, integrate to obtain the aerodynamic performance of the blade.

[0088] In step 3.1, the circumferential velocity V at each cross-section ti Geometric angle of attack Reality σ i The expressions are equations (3), (4), and (5):

[0089]

[0090]

[0091]

[0092] In step 3.2, the angle of attack correction α′ for each cross-section is determined based on eddy current theory. i The steps are as follows:

[0093] Assume the angle of attack correction at the i-th section is Then the angle of attack θ at that section i The calculation expression is given by equation (6):

[0094]

[0095] Based on the airfoil aerodynamic performance table obtained in step 2.2, interpolation calculations are performed to obtain the airfoil aerodynamic performance at an angle of attack of θ. i The Reynolds number is Re i Lift coefficient Cl at time i and drag coefficient Cd i ;

[0096] Finally, based on α in eddy current theory... i The angle-of-attack correction α′ for each cross section is obtained by using the Newton-Raphson equation and the iteration calculation. i The calculation expression is shown in equation (7):

[0097]

[0098] In step 3.3, the corrected velocity U′ at each cross section is calculated. i The calculation expression is given by equation (8):

[0099]

[0100] Thrust T at each section i and torque Q i The expressions are given by equations (9) and (10):

[0101]

[0102]

[0103] In step 3.4, the thrust and torque of the blade are obtained by integration, and the calculated expressions are equations (11) and (12):

[0104]

[0105]

[0106] In step four, the hub and the fuselage in front of the propeller are modified to obtain the aerodynamic performance of the small propeller.

[0107] The thrust and torque of the propeller blades are corrected for the hub, which is simplified here. After the hub rotates, it will generate a certain amount of resistance and torque. The resistance will reduce the thrust of the propeller, and the torque will increase the torque of the propeller, thus reducing the efficiency of the propeller to a certain extent. Therefore, the influence of the hub cannot be ignored. Based on the experience of numerical simulation, the resistance generated by the hub is estimated using formula (13), and the torque is estimated using formula (14).

[0108]

[0109]

[0110] In the formula: S1 is the axial windward area of ​​the propeller hub, in dm². 2 S2 is the circumferential windward area of ​​the propeller hub, in dm². 2 This completes the correction of the propeller hub;

[0111] The steps of the correction method for the propeller-forward fuselage are as follows: The cross-sectional area of ​​the propeller-forward fuselage blocks the radial range of the propeller. It is assumed that the thrust generated at the blocked location is zero, while the torque remains unchanged; therefore, the thrust value T generated within this range is calculated. 遮挡 Subtracting this from the aerodynamic performance of the entire propeller completes the correction of the fuselage in front of the propeller; finally, the thrust T and torque Q of the small propeller are obtained, and the calculation expressions are Equations (15) and (16).

[0112] T = T p -T 桨毂 -T 遮挡 (15)

[0113] Q = Q p +Q 桨毂 (16).

[0114] Example 1

[0115] This invention calculates the aerodynamic performance of propeller blades based on eddy current theory, and incorporates hub correction and in-fuse interference correction based on experience, thereby quickly and accurately obtaining the actual aerodynamic performance of the propeller, providing data support for the overall design iteration of small UAVs and model aircraft. Specifically, this invention discloses a method for rapid prediction of the aerodynamic performance of small propulsion propellers, including the following steps:

[0116] Step 1: Determine the external dimensions of the propeller and the calculation conditions.

[0117] Based on the 3D digital model of propeller J1 and the blade design documents, the blade is divided into 8 sections along the spanwise direction, and the relative positions of each section are given. absolute position r i Airfoil type, chord length b i and installation angle ψ i The data matrix is ​​given by: where i represents the i-th cross-section, i = (1, 2, 3... 8). The blade design range is a cross-section of 0.3-1.0 spanwise, with a Clark-Y airfoil shape. The blade's installation angle and chord length distribution are as follows: Figure 2 As shown. The number of blades N of this propeller. B =2. Propeller diameter D lxj =0.5m, the windward area of ​​the propeller hub along the axial direction S1 = 0.225dm 2 The circumferential windward area of ​​the propeller hub is S2 = 0.09 dm. 2 Three options are available for selecting the diameter of the propeller-forward fuselage: D ds1 =0m, D ds2 =0.1m and D ds3 =0.2m.

[0118] Calculate the required parameters for the task, such as flight altitude H = 0 km, flight speed V = 30 m / s, and propeller rotation speed 8000 rpm.

[0119] Step 2: Calculate the aerodynamic performance of the airfoil quickly and accurately using numerical simulation methods.

[0120] Calculate the Reynolds number Re of the blade under various cross-sectional conditions according to expression (1). i :

[0121]

[0122] Where ρ and μ are the atmospheric density and viscosity coefficients at a flight altitude of 0 km; U iLet U be the vector sum of the airfoil rotational velocity and the propeller flight velocity at the i-th cross-section. In the early stages of optimization design, the angle between the propeller thrust axis and the flight direction is not considered when calculating the Reynolds number; therefore, the propeller rotational speed direction and the flight velocity direction are orthogonal. i The expression is (2):

[0123]

[0124] Based on the calculated Reynolds number, mesh generation and RANS numerical simulation were performed on the Clark-Y airfoil to obtain the lift coefficient and drag coefficient under different Reynolds numbers and angles of attack. In this calculation process, the Reynolds number does not need to correspond one-to-one with the one calculated in expression (1), but only needs to include the entire range. When finally used, the actual Reynolds number and angle of attack can be interpolated.

[0125] Step 3: Calculate the aerodynamic performance of the blades using eddy current theory.

[0126] First, according to the blade distribution, the circumferential velocity V at each cross section is calculated using formulas (3), (4), and (5). ti Geometric angle of attack Reality σ i .

[0127]

[0128]

[0129]

[0130] To accurately calculate the actual angle of attack of the blade at each cross section, the angle of attack correction α′ at each cross section is determined using eddy current theory. i .

[0131] Assume the angle of attack correction at the i-th section is Then the angle of attack θ at that section i The calculation expression is given by equation (6):

[0132]

[0133] Based on the airfoil aerodynamic performance table obtained in step two, interpolation is used to calculate the Clark-Y airfoil at an angle of attack of θ. i The Reynolds number is Re i Lift coefficient Cl at time i and drag coefficient Cd i .

[0134] According to eddy current theory, α i The angle-of-attack correction α′ for each cross section is obtained by using the Newton-Raphson equation and the iteration calculation.i The calculation expression is shown in equation (7) below:

[0135]

[0136] Subsequently, based on the geometric relationship of the blade cross-section velocity triangle, the actual incoming flow velocity U′ at each cross-section was further corrected. i The calculation expression is given by equation (8):

[0137]

[0138] Thrust T at each section i and torque Q i The expressions are shown in equations (9) and (10):

[0139]

[0140]

[0141] The thrust and torque distribution of the blade cross section are obtained by integration, and the calculated expressions are shown in equations (11) and (12):

[0142]

[0143]

[0144] Step 4: Based on practical experience, make corrections to the hub and the fuselage before the propeller to finally obtain the aerodynamic performance of the small propeller.

[0145] After the propeller hub rotates, it generates a certain amount of resistance and torque. The resistance reduces the propeller's thrust, while the torque increases it, resulting in a certain degree of reduction in the propeller's efficiency. Therefore, the influence of the hub cannot be ignored. Based on numerical simulation experience, the magnitude of the resistance generated by the hub can be estimated using formula (13), and the torque value can be estimated using formula (14):

[0146]

[0147]

[0148] In the formula: S1 is the axial windward area of ​​the propeller hub, in dm². 2 S2 is the circumferential windward area of ​​the propeller hub, in dm². 2 This completes the correction of the propeller hub.

[0149] The main steps of the correction method for the propeller-forward fuselage are as follows: The cross-sectional area of ​​the propeller-forward fuselage blocks the radial range of the propeller, assuming that the thrust generated at the blocked location is zero, while the torque remains unchanged. Therefore, the thrust value T generated within this range is calculated. 遮挡 Subtracting this from the overall aerodynamic performance of the propeller completes the correction of the fuselage in front of the propeller. Finally, the thrust T and torque Q of the small propeller are obtained, and the calculation expressions are Equations (15) and (16).

[0150] T = T p -T 桨毂 -T 遮挡 (15)

[0151] Q = Q p +Q 桨毂 (16)

[0152] To verify the generality of this invention, three different propeller-forward fuselage diameters were selected: D ds1 =0m, D ds2 =0.1m and D ds3 =0.2m.

[0153] Data calculations were performed for three different working conditions, and the calculation results were compared with the numerical simulation results, such as... Figure 4 and Figure 5 As shown in the figure, the data reveals that under three different propeller-forward propeller actions, the aerodynamic performance of the propeller calculated using this invention is quite close to the numerical simulation results. The maximum thrust error is approximately 6%, and the maximum torque error is within 3%. This demonstrates that this invention provides good accuracy for the rapid prediction of the aerodynamic performance of small propellers and can be used for preliminary calculations in propeller optimization.

[0154] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for rapid prediction of the aerodynamic performance of small propellers, characterized in that, The method includes the following steps: Step 1: Determine the external dimensions of the propeller and the calculation conditions; Step 2: Calculate the aerodynamic performance of the airfoil; Step 3: Calculate the aerodynamic performance of the blades; Step 4: Make corrections to the hub and the fuselage before the propeller to finally obtain the aerodynamic performance of the small propeller. In step four, the hub and the fuselage in front of the propeller are modified to obtain the aerodynamic performance of the small propeller. The thrust and torque of the propeller blades are corrected for the hub, and the correction is simplified. After the hub rotates, it will generate a certain amount of resistance and torque. The resistance will reduce the thrust of the propeller, and the torque will increase the torque of the propeller, which will lead to a certain degree of reduction in the efficiency of the propeller. Therefore, the influence of the hub cannot be ignored. According to the experience of numerical simulation, the resistance generated by the hub is estimated using formula (13), and the torque is estimated using formula (14). （13） （14） In the formula: The frontal area of ​​the propeller hub along the axial direction, in units of ; The frontal area of ​​the propeller hub in the circumferential direction, in units of , The rotational speed of the propeller. To achieve flight speed, the propeller hub correction is now complete; The steps of the correction method for the propeller-forward fuselage are as follows: The cross-sectional area of ​​the propeller-forward fuselage blocks the radial range of the propeller; it is assumed that the thrust generated at the blocked location is zero, while the torque remains unchanged; therefore, the thrust value generated within this range is calculated. Subtracting this from the overall aerodynamic performance of the propeller completes the correction of the fuselage in front of the propeller; ultimately, the thrust of the small propeller is obtained. and torque The calculation expressions are equations (15) and (16). （15） （16） in, T p and Q p The thrust and torque of the propeller blades.

2. The method for rapid prediction of aerodynamic performance of small propellers as described in claim 1, characterized in that, In step one, the external dimensions of the propeller and the calculation conditions are determined as follows: Step 1.1: Based on the three-dimensional digital model of the propeller and the blade design documents, determine the spanwise position, airfoil type, chord length, and installation angle of multiple sections along the spanwise direction. Step 1.2: Determine the calculation parameters based on the calculation task, including flight altitude, flight speed, and propeller rotation speed.

3. The method for rapid prediction of aerodynamic performance of small propellers as described in claim 2, characterized in that, In step 1.1, the blades are divided along the spanwise direction according to the blade design documents. Each section provides the relative position of each spanwise location. Absolute position Airfoil type, chord length and installation angle The data matrix, and the number of propeller blades propeller diameter , the axial frontal area of ​​the propeller hub The circumferential frontal area of ​​the propeller hub Diameter of the propeller-forward fuselage ,in: i Represents the first A cross section, i =1, 2, 3... N .

4. The method for rapid prediction of aerodynamic performance of small propellers as described in claim 3, characterized in that, In step 1.2, the flight altitude is determined according to the calculation task. Flight speed The rotational speed of the propeller This prepares parameters for subsequent calculations.

5. The method for rapid prediction of aerodynamic performance of small propellers as described in claim 4, characterized in that, In step two, the aerodynamic performance of the airfoil is calculated, and the steps are as follows: Step 2.1: Estimate the Reynolds number range during use based on the propeller's flight speed, rotation speed, and chord length of each section; Step 2.2: Using numerical calculation software, accurately calculate the aerodynamic performance of each airfoil within the Reynolds number range in Step 2.

1.

6. The method for rapid prediction of aerodynamic performance of small propellers as described in claim 5, characterized in that, In step 2.1, the Reynolds number of each section of the blade is calculated. The expression is (1): （1） in, and At flight altitude Atmospheric density and viscosity coefficient; For the first The vector sum of the airfoil rotational speed and propeller flight speed at each cross-section; since the aforementioned rapid aerodynamic performance prediction method is aimed at the preliminary design stage, it does not consider the case where there is an angle between the propeller thrust axis and the flight direction. Therefore, the propeller rotational speed direction and the flight speed direction are orthogonal. The expression is (2): （2）。 7. The method for rapid prediction of aerodynamic performance of small propellers as described in claim 6, characterized in that, In step 2.2, aerodynamic data under different Reynolds numbers are obtained by generating meshes and performing RANS numerical simulations on each airfoil. This includes lift coefficients and drag coefficients under different Reynolds numbers and angles of attack, forming an airfoil aerodynamic performance table. The Reynolds number does not need to correspond one-to-one with the one calculated in step 2.1; it only needs to include the entire range. When finally used, the actual Reynolds number and angle of attack can be interpolated.

8. The method for rapid prediction of aerodynamic performance of small propellers as described in claim 7, characterized in that, In step three, the aerodynamic performance of the blades is calculated, and the steps are as follows: Step 3.1: Calculate the circumferential velocity, geometric angle of attack, and solidity of each cross-section; Step 3.2: Determine the angle of attack correction for each cross-section based on eddy current theory; Step 3.3: Determine the aerodynamic performance parameters for each cross section, including thrust coefficient and torque coefficient; Step 3.4: Based on the aerodynamic data from Step 3.3, integrate to obtain the aerodynamic performance of the blade.

9. The method for rapid prediction of aerodynamic performance of small propellers as described in claim 8, characterized in that, In step 3.1, the circumferential velocity at each cross-section Geometric angle of attack Reality The expressions are equations (3), (4), and (5): （3） （4） （5） In step 3.2, the angle of attack correction for each cross-section is determined based on eddy current theory. The steps are as follows: Assume the angle of attack correction at the i-th section is Then the angle of attack at that section The calculation expression is given by equation (6): （6） Based on the airfoil aerodynamic performance table obtained in step 2.2, interpolation calculations are performed to obtain the airfoil aerodynamic performance at an angle of attack of... The Reynolds number is Lift coefficient at time and drag coefficient ; Finally, based on eddy current theory... The equations, using Newton's iteration calculations, yielded the angle-of-attack corrections for each cross-section. The calculation expression is shown in equation (7): （7） In step 3.3, the corrected velocities at each cross section are calculated. The calculation expression is given by equation (8): （8） Thrust at each section and torque The expressions are equations (9) and (10): （9） （10） In step 3.4, the thrust and torque of the blade are obtained by integration, and the calculated expressions are equations (11) and (12): （11） （12）。

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