Aircraft high lift device load calculation method considering propeller slip flow influence

Abstract

The invention discloses an aircraft high lift device load calculation method considering propeller slip flow influence. The method comprises the following steps: S1, calculating a correction coefficient Ks of the influence of the slip flow of the propeller on the load of the high lift device based on the geometric parameters of the high lift device of the aircraft, the engine parameters of the turbine propeller and the flight state; s2, acquiring initial pressure distribution of the surface of the high lift device of the aircraft without being influenced by the slip flow; and S3, combining the correction coefficient with the initial pressure distribution, performing correction according to the slip flow influence area to obtain the pressure distribution of the surface of the airplane high lift device after slip flow influence, and calculating the aerodynamic load of the airplane high lift device according to the pressure distribution. According to the method, the slipstream influence of the turboprop engine is accurately calculated, the effect of the propeller effect on the high lift device is quantified, and the accuracy and design safety of load evaluation of the high lift device of the airplane are improved.

Description

Technical Field

[0001] This invention belongs to the field of load design and verification technology, and specifically relates to a method for calculating the load of an aircraft lift enhancement device that takes into account the influence of propeller slipstream. Background Technology

[0002] In modern aircraft design, accurate calculation of lift enhancement device loads is of great significance. However, traditional calculation methods do not fully consider the impact of turboprop engine slipstream on the performance and load distribution of lift enhancement devices, resulting in discrepancies between the calculated results and actual flight conditions. This not only threatens the structural safety of the aircraft but also affects the rationality of the overall aircraft design. Summary of the Invention

[0003] The purpose of this invention is to provide a method for calculating the load of aircraft lift enhancement devices that considers the influence of propeller slipstream. This invention achieves accurate calculation of the slipstream effect of turboprop engines, quantifies the role of propeller effects on lift enhancement devices, and improves the accuracy and design safety of aircraft lift enhancement device load assessment.

[0004] The technical solution of this invention is: a method for calculating the load of an aircraft lift enhancement device considering the influence of propeller slipstream, the steps of which are as follows:

[0005] S1. Based on the geometric parameters of the aircraft lift enhancement device, the engine parameters of the turboprop, and the flight status, calculate the correction factor K for the influence of propeller slipstream on the load of the lift enhancement device. s ;

[0006] S2. Obtain the initial pressure distribution on the surface of the aircraft lift enhancement device when it is not affected by the slipstream;

[0007] S3. Combine the correction factor with the initial pressure distribution, and correct according to the slipstream influence area to obtain the pressure distribution on the surface of the aircraft lift enhancement device after the slipstream influence, and calculate the aerodynamic load of the aircraft lift enhancement device accordingly.

[0008] In S1 of the aforementioned method for calculating the load of an aircraft lift enhancement device, the geometric parameters of the aircraft lift enhancement device include: flap span and the relative position of the aircraft lift enhancement device and the engine.

[0009] In S1 of the aforementioned method for calculating the load of aircraft lift enhancement devices, the engine parameters include: the diameter of the turboprop disk, and the propeller thrust under various altitudes, speeds, and atmospheric conditions.

[0010] In S1 of the aforementioned method for calculating the load of aircraft lift enhancement devices, the correction factor K s Calculate using the following formula:

[0011] In the formula, D' is the length of the upper base of the trapezoidal slipflow coverage area of ​​the flap, and L fTo extend the flaps, T c D is the propeller thrust coefficient, D” is the length of the lower base of the trapezoidal region affected by slipflow, and T is the propeller thrust coefficient. c ' is the influence coefficient of the slip flow in the directly affected area.

[0012] In S2 of the aforementioned method for calculating the load of aircraft lift enhancement devices, the initial pressure distribution is obtained based on wind tunnel tests or CFD numerical simulations.

[0013] In S3 of the aforementioned aircraft lift enhancement device load calculation method, the slipstream influence area is divided as follows: based on the relative position of the aircraft lift enhancement device and the turboprop, the slipstream influence behind the propeller disk is distributed with a gradient attenuation along the spanwise direction, and the overall influence area is trapezoidal in shape, with the area behind the propeller disk being the direct action area and the two sides being the indirect action areas.

[0014] In S3 of the aforementioned method for calculating the load of aircraft lift enhancement devices, the pressure distribution on the surface of the aircraft lift enhancement device after the slipstream effect is calculated as follows: The correction factor... Multiplying the total unpowered aerodynamic load of the flap yields the total aerodynamic load of the flap considering the slipstream effect; for the slipstream-covered flap region, the pressure distribution of the flap when there is no slipstream effect is superimposed with the product of the velocity-pressure influence coefficient and the pressure distribution when there is no slipstream effect.

[0015] In S3 of the aforementioned method for calculating the load of an aircraft lift enhancement device, the aerodynamic load of the aircraft lift enhancement device is calculated as follows: the pressure distribution on the surface of the aircraft lift enhancement device after considering the effect of slipstream is integrated to obtain the aerodynamic load of the aircraft lift enhancement device.

[0016] Beneficial effects: This invention defines the influence range of propeller slipstream as a trapezoidal distribution model. By establishing a slipstream influence coefficient model and combining pressure distribution data under no-power conditions, slipstream influence is superimposed on trapezoidal regions, achieving accurate quantification of the load of the lift enhancement device under propeller slipstream interference conditions. This solves the technical problem of difficulty in accurately calculating slipstream influence in traditional methods and provides effective support for the design optimization of aircraft lift enhancement device load.

[0017] Traditional methods do not fully consider the impact of turboprop engine slipstream on the performance and load distribution of lift enhancement devices, leading to discrepancies between calculated results and actual flight conditions. This invention proposes defining the influence range of the propeller slipstream as a trapezoidal distribution model. By establishing a dynamic correction coefficient model for the slipstream and a regionalized pressure distribution correction method, the interference effect of the propeller slipstream on the aerodynamic load of the lift enhancement device is quantified. The specific process includes parameter input, correction coefficient modeling, obtaining the initial load baseline, delineating the slipstream influence area, and calculating the load correction. This method solves the technical problem of accurately calculating the slipstream influence in traditional methods, significantly improving the accuracy of aircraft lift enhancement device load assessment and design safety, and can effectively guide the load design optimization of aircraft lift enhancement devices. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the flap being affected by slipstream, provided by the present invention.

[0019] Figure 2 This is a schematic diagram illustrating the slipstream effect of two turboprop engines on one side of an aircraft, provided by the present invention. Detailed Implementation

[0020] Example 1. Taking a certain type of single-sided twin-engine turboprop aircraft as an example, this paper illustrates the calculation process of the aircraft lift enhancement device load considering the propeller slipstream effect. See [link to example]. Figure 1 and Figure 2 :

[0021] Step 1: Determine aircraft parameters: Determine the span of flap 1 on wing 3. Propeller disk diameter 2 propeller thrust And the center positions of flap 1 and propeller 2, thereby determining the relative positions of flap 1 and propeller 2;

[0022] Step 2: Derivation and calculation of relevant parameters:

[0023] like Figure 1 The diagram shown illustrates the effect of slipstream on the flap 1 provided by this invention. The parameters in the diagram are as follows:

[0024] : Incoming flow velocity (taken as the aircraft's flight speed), m / s;

[0025] Pressure, Pa;

[0026] Pressure in front of the propeller disk, Pa;

[0027] The pressure increase through the propeller disk 2 is measured in Pa.

[0028] : Axial velocity increment of propeller disk 2, m / s;

[0029] : The axial velocity increment of the slickflow tube after contraction, in m / s.

[0030] The direction of travel is to the left. The dynamic pressure at a distance in front of the propeller disk is: (1)

[0031] According to Bernoulli's equation, the total atmospheric pressures before and after the propeller disk are as follows: (2) (3)

[0032] The pressure increment through the propeller disk is: (4)

[0033] The propeller thrust can be expressed as: (5) In the formula: : Paddle disk area;

[0034] According to the momentum theorem, the propeller thrust can also be expressed as: (6)

[0035] In the formula: : The mass of air flowing across the paddle disk per second, in kg.

[0036] (7)

[0037] Equation (6) can then be transformed into: (8)

[0038] Combining equations (5) and (8), we get: (9)

[0039] Let the propeller thrust coefficient be: (10)

[0040] Combining (8), (9), and (10), we can obtain the velocity increment coefficient at the paddle disk plane relative to the incoming flow further ahead: (11)

[0041] The dynamic pressure of the flap portion behind the propeller disk, covered by the slipstream, can be written as: (12)

[0042] The ratio of the dynamic pressure of the flap portion covered by the slipstream to the incoming dynamic pressure at a distance in front of the rotor disk is: (13)

[0043] According to the law of conservation of mass, we have: (14)

[0044] The ratio of the upper side length of the trapezoidal flap slipstream coverage area to the rotor disk diameter is: (15)

[0045] The aerodynamic interference of the slipstream on the flaps manifests as a gradient-decreasing velocity field along the spanwise direction. Its area of ​​influence can be considered a trapezoidal shape, with a greater impact behind the propeller disk (the direct impact area) and less impact on the areas to the sides behind the propeller disk (the indirect impact area). The impact coefficient decreases linearly. A schematic diagram of the impact is shown below. Figure 1 The area shown by the dashed line on the right is given. According to formula (13), the velocity-pressure increment is Tc, and the velocity-pressure influence coefficient of the directly affected area can be obtained as follows: (16) (17)

[0046] In the formula: The slipstream affects the length of the lower base of the trapezoidal region, which is 1.3 times the diameter of the propeller disk. : Directly affecting slip flow influence coefficient.

[0047] This example uses a four-engine turboprop aircraft. The effect of slipflow on flap loading can be assumed to increase the velocity pressure of the flap portion covered by its contraction section from the original Q to Q'. Then, the slipflow correction factor for the single-sided (two-engine) flap loading can be obtained as follows: (18)

[0048] Substituting equations (10) and (17), equation (18) can be transformed into: (19)

[0049] Step 3: Obtain pressure distribution and loads without slippage: Based on wind tunnel tests or CFD numerical simulation results, determine the pressure distribution of the flaps under slippage conditions, and obtain the total unpowered aerodynamic loads of the flaps through integration.

[0050] Step 4: Division of the slipstream influence area: Based on the relative position of the lift enhancement device and the propeller, the slipstream influence behind the propeller disk is distributed with a gradient attenuation along the span, and the overall influence area is trapezoidal in shape, with the area behind the propeller disk being the direct influence area and the two sides being the indirect influence areas.

[0051] Step 5: Calculate the load and pressure distribution considering the effects of slipflow: Apply the slipflow correction factor Multiplying the total unpowered aerodynamic load of the flap yields the total aerodynamic load of the flap considering the slipstream effect. For the slipstream-covered flap portion (the area within the trapezoid), the pressure distribution of the flap without slipstream action is superimposed with the product of the velocity-pressure influence coefficient and the pressure distribution without slipstream in that area to obtain the flap pressure distribution considering the slipstream effect.

[0052] Step 6: Calculate the final results: Integrate the flap pressure distribution considering the slipstream effect to obtain the total aerodynamic force, aerodynamic moment, pressure center, and other results of the flap.

[0053] Example 2. A method for calculating the load of an aircraft lift enhancement device considering the influence of propeller slipstream. This method proposes defining the influence range of the propeller slipstream as a trapezoidal distribution model. By constructing a slipstream correction coefficient model and a regionalized pressure distribution correction method, the interference effect of the propeller slipstream on the aerodynamic load of the lift enhancement device is quantified. The specific process is as follows:

[0054] Step 1, Parameter Input: Obtain the lift enhancement device's geometric parameters (span, deflection angle) and the turboprop engine's parameters (thrust, diameter), and determine the relative position of the lift enhancement device and the propeller;

[0055] Step 2, Correction coefficient modeling: Based on the slip flow theory and the law of conservation of mass, a correction coefficient model for the influence of slip flow is constructed;

[0056] Step 3, Initial Load Reference: Obtain the initial pressure distribution of the lift enhancement device under no slipflow interference through wind tunnel testing or CFD numerical simulation;

[0057] Step 4, Division of the slipstream-affected area: Based on the slipstream velocity field diffusion law, the area of ​​the lift enhancement device affected by the slipstream is divided into a trapezoidal shape, including the core area directly affected and the edge area indirectly affected;

[0058] Step 5, Load Correction Calculation: Apply the corresponding correction coefficients to the core and edge regions to perform gradient correction on the initial pressure distribution, obtain the pressure distribution under the influence of slipstream, integrate the corrected pressure distribution, and calculate the aerodynamic load of the lift enhancement device (total aerodynamic force of flaps, aerodynamic torque, pressure center).

[0059] Example 3. A method for calculating the load of an aircraft lift enhancement device considering the influence of propeller slipstream, see [link to example]. Figure 1 and Figure 2 For turboprop engines, the impact of the slipstream effect caused by the propeller on the load of the lift enhancement device is calculated, and the load of the lift enhancement device after the impact is calculated using a correction factor. The specific steps are as follows:

[0060] (1) Obtain the geometric parameters of the aircraft lift enhancement device;

[0061] (2) Obtain turboprop engine parameters;

[0062] (3) Based on the geometric parameters, engine parameters and flight status of the aircraft lift enhancement device, calculate the correction coefficient for the influence of propeller slipstream on the load of the lift enhancement device;

[0063] (4) Obtain the initial pressure distribution on the surface of the lift enhancement device without the influence of slip flow through wind tunnel tests or computational fluid dynamics (CFD) numerical simulations;

[0064] (5) Determine the influence area of ​​the slipstream on the lift enhancement device based on the velocity field distribution characteristics of the propeller slipstream;

[0065] (6) Combine the correction coefficient with the initial pressure distribution and correct it according to the affected area to obtain the surface pressure distribution of the lift device after the slip flow influence, and calculate the aerodynamic load of the lift device accordingly.

[0066] In step (1) above, the geometric parameters of the lift enhancement device include the flap span and the relative position of the lift enhancement device and the turboprop engine.

[0067] In step (2) above, the engine parameters include propeller disk diameter, different altitudes, speeds, and thrust under atmospheric conditions.

[0068] In step (3) above, the correction coefficient is calculated using propeller thrust, disk diameter, flap span, incoming flow velocity, and air density.

[0069] In step (4) above, the initial pressure distribution on the surface of the lifting device does not include the slip flow effect generated by the propeller.

[0070] In step (5) above, the method for determining the affected area includes:

[0071] (5.1) Based on the velocity field distribution of the propeller slipstream and the geometric position of the lift enhancement device, delineate the direct and indirect action areas of the slipstream;

[0072] (5.2) The shape of the slipstream direct action area is a trapezoidal outward expansion distribution, with the base of the trapezoid parallel to the propeller rotation plane, and the two sides determined based on the distance between the upper and lower bases;

[0073] (5.3) The indirect action area is the transition area outside the trapezoidal expansion area, and its correction coefficient weight decreases with the distance from the core area of ​​the slip flow.

[0074] In step (6) above, the calculation of the aerodynamic load includes:

[0075] (6.1) Integrate the corrected pressure distribution to obtain the lift, drag and torque of the lifting device;

[0076] (6.2) Analyze the influence of glide flow on the load of lift enhancement device under different flight conditions.

[0077] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for calculating the load of an aircraft lift enhancement device considering the influence of propeller slipstream, characterized in that, The steps are as follows: S1. Based on the geometric parameters of the aircraft lift enhancement device, the engine parameters of the turboprop, and the flight status, calculate the correction factor K for the influence of propeller slipstream on the load of the lift enhancement device. s ; S2. Obtain the initial pressure distribution on the surface of the aircraft lift enhancement device when it is not affected by the slipstream; S3. Combine the correction factor with the initial pressure distribution, and correct according to the slipstream influence area to obtain the pressure distribution on the surface of the aircraft lift enhancement device after the slipstream influence, and calculate the aerodynamic load of the aircraft lift enhancement device accordingly.

2. The method for calculating the load of an aircraft lift enhancement device according to claim 1, characterized in that, In S1, the geometric parameters of the aircraft lift enhancement device include: flap span and the relative position of the aircraft lift enhancement device and the engine.

3. The method for calculating the load of an aircraft lift enhancement device according to claim 1, characterized in that, In S1, engine parameters include: turboprop disk diameter, propeller thrust at various altitudes, speeds, and atmospheric conditions.

4. The method for calculating the load of an aircraft lift enhancement device according to claim 1, characterized in that, In S1, the correction coefficient K s Calculate using the following formula: ， In the formula, D' is the length of the upper base of the trapezoidal slipflow coverage area of ​​the flap, and L f To extend the flaps, T c D is the propeller thrust coefficient, D” is the length of the lower base of the trapezoidal region affected by slipflow, and T is the propeller thrust coefficient. c ' is the influence coefficient of the slip flow in the directly affected area.

5. The method for calculating the load of an aircraft lift enhancement device according to claim 1, characterized in that, In S2, the initial pressure distribution is obtained based on wind tunnel tests or CFD numerical simulations.

6. The method for calculating the load of an aircraft lift enhancement device according to claim 1, characterized in that, In S3, the slipstream influence area is divided as follows: Based on the relative position of the aircraft lift enhancement device and the turboprop, the slipstream influence behind the propeller disk is distributed with a gradient attenuation along the span, and the overall influence area is trapezoidal in shape, with the area behind the propeller disk being the direct influence area and the two sides being the indirect influence areas.

7. The method for calculating the load of an aircraft lift enhancement device according to claim 1, characterized in that, In S3, the pressure distribution on the surface of the aircraft lift enhancement device after the slipstream effect is calculated as follows: (The correction factor is then applied.) Multiplying the total unpowered aerodynamic load of the flap yields the total aerodynamic load of the flap considering the slipstream effect; for the slipstream-covered flap region, the pressure distribution of the flap when there is no slipstream effect is superimposed with the product of the velocity-pressure influence coefficient and the pressure distribution when there is no slipstream effect.

8. The method for calculating the load of an aircraft lift enhancement device according to claim 1, characterized in that, In S3, the aerodynamic load of the aircraft lift enhancement device is calculated as follows: the pressure distribution on the surface of the aircraft lift enhancement device after considering the slipstream effect is integrated to obtain the aerodynamic load of the aircraft lift enhancement device.

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