Method for calculating large-angle gliding performance of fixed-wing turboprop aircraft

Abstract

The invention belongs to the field of aviation medium-sized aircraft design, and relates to a large-angle glide performance calculation method for a fixed-wing turboprop aircraft. The method comprises the steps that according to the characteristics of a turbine engine and a propeller, the combined characteristics of a power device of the propeller-driven aircraft are determined, large-angle gliding is achieved by using the double-open state of a spoiler, increasing resistance and reducing lift force, and the needed large-angle gliding performance of the aircraft is obtained through modeling and adjustment calculation.

Description

Technical Field

[0001] The invention belongs to the field of aviation medium-sized aircraft design and relates to a method for calculating the large-angle glide performance of a fixed-wing turboprop aircraft. Background Art

[0002] Turboprop aircraft are generally used for the transportation and delivery of cargo, equipment and personnel. Their use takes into account the landing terrain and the ability to defend against attacks during wartime. Therefore, a large-angle descent can greatly reduce the descent time and distance, which in turn largely determines the safety of the flight crew and the aircraft.

[0003] It is impossible to obtain clear methods and relevant technical information on the calculation of turboprop aircraft's high-angle descent performance from foreign countries through public channels. No similar or related patents were found through searching patent websites, and no related research results were found in China. Summary of the invention

[0004] Purpose of the invention: To provide a method for calculating the high-angle descent performance of a turboprop aircraft, so as to solve the problem that the current high-angle descent performance calculation of a turboprop aircraft has a large deviation from the actual high-angle descent capability of the aircraft, and to greatly improve the accuracy of the high-angle descent performance calculation.

[0005] Technical solution:

[0006] A method for calculating the high-angle glide performance of a fixed-wing turboprop aircraft is provided, comprising:

[0007] Based on the characteristics of turbine engines and propellers, the combined characteristics of propeller aircraft power units are determined. By using the double-open state of spoilers, the drag is increased and the lift is reduced to achieve a large-angle descent. The required large-angle descent performance of the aircraft is obtained through modeling and adjustment calculations.

[0008] Furthermore, according to the characteristics of turbine engines and propellers, the combined characteristics of propeller aircraft power units are determined. By using the dual-open state of spoilers, the drag is increased and the lift is reduced to achieve a large-angle descent. The required large-angle descent performance of the aircraft is obtained through modeling and adjustment calculations, including:

[0009] Step 1: Determine the relevant parameters of the turboprop aircraft's large-angle descent through wind tunnel tests and simulations, and clarify the requirements for the dual opening angles of the spoilers and the aircraft's descent speed;

[0010] Step 2: Compensate the lift coefficient and drag coefficient after the spoiler is lowered according to the effect of the spoiler on the aerodynamic characteristics of the aircraft after it is opened;

[0011] Step three, according to the aircraft descent speed requirements, convert the descent true speed at each altitude, thereby calculating the descent angle θ and angle of attack α at the corresponding altitude, and further obtain the descent horizontal distance, descent time and descent fuel consumption of the entire descent process.

[0012] Furthermore, the glide-related parameters include: lift coefficient and drag coefficient after the spoiler is lowered; the lift coefficient and drag coefficient after the spoiler is lowered have corresponding relationships with the angle of attack α, and the calculation formulas for the compensation change value of the lift coefficient and the compensation change value of the drag coefficient after the spoiler is lowered are:

[0013] ΔC L =-0.01308*δ sp ;

[0014] ΔC D =(0.000001*α+0.000031)*δ sp *δ sp -(0.000130*α-0.000554)*δ sp ;

[0015] ΔC L is the compensation change value of the lift coefficient after the spoiler is lowered;

[0016] ΔC D The compensation value of the drag coefficient after the spoiler is lowered;

[0017] δsp is the deflection after the spoiler is lowered.

[0018] Furthermore, the descent angle θ and the angle of attack α at different altitudes are calculated based on the force balance formula; the glide-related parameters include: drag and lift;

[0019] The lateral force balance formula is:

[0020]

[0021] The longitudinal force balance formula is:

[0022]

[0023] P—given thrust; Q—drag; G—known aircraft weight; Y—lift; α—angle of attack at the same altitude; θ—angle of descent at the same altitude.

[0024] Furthermore, according to the aircraft descent speed requirement, the true descent speed at each altitude is converted to obtain the descent angle θ and the angle of attack α at the corresponding altitude, including:

[0025] a) Divide the height difference between the given descent start height and the descent end height into n equal segments, so that there are several calculated heights H0, H1…Hn+1 on the descent height;

[0026] b) for the mth calculated altitude Hm, determine the true descent speed; m ranges from 0 to n+1;

[0027] c) Find out the pulling force value and fuel consumption rate according to the corresponding calculated altitude and true descent speed, and calculate the fuel consumption per hour and per kilometer;

[0028] d) Set an initial angle of attack α0;

[0029] e) Calculate the descent angle θ0 according to the longitudinal force balance formula;

[0030] f) Substitute the descent angle θ0 into the lateral force balance formula and calculate α1;

[0031] g) Repeat d, e, and f above until |α i -α i+1 When θ is less than or equal to the preset threshold ζ, i and α i As this calculates the descent angle θ at altitude and speed m and angle of attack α m .

[0032] Furthermore, the descent horizontal distance, descent time and descent fuel consumption of the entire descent process can be obtained, including:

[0033] Calculate the average velocity V at each adjacent height mpj =(V m +V m+1 ) / 2;

[0034] Calculate the average descent angle θ of each adjacent height mpj =(θ m +θ m+1 ) / 2;

[0035] Calculate the average descent rate V at each adjacent height ypj =V mpj sinθ mpj ;

[0036] Calculate the time and horizontal distance of this descent;

[0037] The sum of the descending time of each section is taken as the descending time, and the sum of the descending horizontal distance of each section is taken as the descending horizontal distance;

[0038] Use the average descent speed of each section to find out the pulling force and fuel consumption rate; calculate the hourly fuel consumption rate, and then calculate the fuel consumption of this section; the sum of the fuel consumption of each section is the fuel consumption of descent at a constant indicated speed.

[0039] Furthermore, the method is applicable to medium and large turboprop passenger aircraft, transport aircraft and related platform aircraft.

[0040] Beneficial effects:

[0041] The invention determines the lift coefficient C of the turboprop aircraft at a large glide angle by first determining the physical parameters and aerodynamic characteristic parameters of the turboprop aircraft and combining the influence of the spoiler on the aerodynamic characteristics of the aircraft after it is lowered. L and the drag coefficient C D , and then determine the descent angle θ and angle of attack α of the aircraft when it descends at a large angle through force analysis, and finally calculate the horizontal descent distance, descent time and descent fuel consumption of the entire descent process of the aircraft when it descends at a large angle. This calculation method is intuitive, simple, and has clear theoretical logic, which is easy for aircraft designers to master. This method is comprehensive, versatile, and has wide application value. It is suitable for medium and large turboprop passenger aircraft, transport aircraft and related platform aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a force analysis diagram for a turboprop aircraft during a large descent. DETAILED DESCRIPTION

[0043] The high-angle glide performance calculation method of the fixed-wing turboprop aircraft comprises the following steps:

[0044] Step 1: Determine the parameters related to the large-angle descent of the turboprop aircraft, and clarify the requirements for the double opening angles of the spoilers and the aircraft descent speed;

[0045] Step 2: Determine the effect of the spoiler on the aerodynamic characteristics of the aircraft after it is opened. The compensation formula for the lift coefficient and drag coefficient after the spoiler is lowered is as follows:

[0046] ΔC L =-0.01308*δ sp ;

[0047] ΔC D =(0.000001*α+0.000031)*δ sp *δ sp -(0.000130*α-0.000554)*δ sp .

[0048] Step 3: After the indicated speed is determined, the true descent speed at each altitude can be converted. Corresponding to the true speed at each altitude, the descent angle θ and the angle of attack α at the corresponding altitude can be obtained by the following formula, and the horizontal descent distance, descent time and descent fuel consumption of the entire descent process can be further obtained.

[0049]

[0050] The present invention provides a method for calculating the high-angle glide performance of a turboprop aircraft, which mainly focuses on the characteristics of the turbine engine and the propeller, determines the combined characteristics of the propeller aircraft power plant, increases the drag and reduces the lift by using the double-open state of the spoiler, and obtains the required high-angle glide performance of the aircraft through modeling, adjustment and calculation. The steps of this method are as follows:

[0051] In order to achieve a large-angle descent of the aircraft, it is necessary to increase the drag and reduce the lift by using the spoilers in double-open state, and rely on numerical simulation and wind tunnel tests to find out the formula for the change of lift coefficient and drag coefficient after the spoilers are lowered:

[0052] ΔC L =-0.01308*δ sp ;

[0053] ΔC D =(0.000001*α+0.000031)*δ sp *δ sp -(0.000130*α-0.000554)*δ sp .

[0054] Where:

[0055] ΔCL——compensation change of lift coefficient;

[0056] ΔCD——compensation change of drag coefficient;

[0057] α——fuselage angle of attack;

[0058] δsp——spoiler deflection.

[0059] When the aircraft is flying without sideslip or rolling, Figure 1 As shown, the flight dynamics equation is:

[0060] m dV / dt=Pcos(α+φ_p)-Q+Gsinθ………………(1)

[0061] mV dθ / dt=Psin(α+φ_p)+Y-Gcosθ………………(2)

[0062] At a certain altitude, when descending at a constant true speed, it is assumed that the descent angle θ remains constant in a very short period of time. Formulas (1) and (2) can be simplified to the following formulas:

[0063] Pcos(α+φ_p)-Q+Gsinθ=0……………………(3)

[0064] Psin(α+φ_p)+Y-Gcosθ=0……………………(4)

[0065] Where:

[0066] P——thrust;

[0067] Q – resistance;

[0068] G——aircraft gravity;

[0069] Y——lift;

[0070] α——fuselage angle of attack;

[0071] θ——Descent angle.

[0072] After the indicated speed is determined, the true descent speed at each altitude can be converted. Corresponding to the true speed at each altitude, the descent angle θ and the angle of attack α at the corresponding altitude can be obtained by formulas (3) and (4), and the descent horizontal distance, descent time and descent fuel consumption of the entire descent process can be further obtained. The specific process is as follows:

[0073] a) Divide the height difference between the given descent start height and the descent end height into n equal parts, so that there are several calculated heights H0, H1...Hn+1 on the descent height;

[0074] b) descend at the determined descent speed (true speed) at the mth calculated altitude; m ranges from 0 to n+1;

[0075] c) Find out the pulling force and fuel consumption rate at the corresponding speed and altitude, and calculate the fuel consumption per hour and per kilometer;

[0076] d) Set an initial value of the angle of attack α0;

[0077] e) Calculate the descent angle θ0 according to equation (4);

[0078] f) Substitute the descent angle θ0 into equation (3) and find α1;

[0079] g) Repeat d, e, and f above until |α i -α i+1 When ζ is less than or equal to ζ (ζ is a small quantity), the descent angle θ at this calculated height and speed is m and angle of attack α m is equal to θ i and α i ;

[0080] h) Calculate the average speed V at each adjacent height mpj =(V m +V m+1 ) / 2;

[0081] m) Calculate the average descent angle θ of each adjacent height mpj =(θ m +θ m+1 ) / 2;

[0082] j) Calculate the average descent rate V at each adjacent height ypj =V mpj sinθ mpj ;

[0083] k) Calculate the time and horizontal distance of this descent;

[0084] l) The sum of the descent time of each section is the descent time, and the sum of the horizontal descent distance of each section is the horizontal descent distance;

[0085] m) Find the pulling force and fuel consumption rate based on the average descent speed of each section. Calculate the hourly fuel consumption rate and then calculate the fuel consumption of this section. The sum of the fuel consumption of each section is the fuel consumption of descent at the same speed.

[0086] The invention discloses a method for determining the large-angle glide performance calculation of a medium-sized transport aircraft, by first determining the physical parameters and aerodynamic characteristic parameters of the turboprop aircraft, and combining the influence of the spoiler on the aerodynamic characteristics of the aircraft after being lowered, to determine the large-angle glide lift coefficient C of the turboprop aircraft. L and the drag coefficient C D , and then determine the descent angle θ and angle of attack α when the aircraft descends at a large angle through force analysis, and finally calculate the descent horizontal distance, descent time and descent fuel consumption of the entire descent process when the aircraft descends at a large angle.

[0087] The calculation method is intuitive, simple, and has clear theoretical logic, making it easy for aircraft designers to master. The method is comprehensive, versatile, and has wide application value, and is suitable for medium and large turboprop passenger aircraft, transport aircraft, and related platform aircraft.

Claims

1. A method for calculating the high-angle glide performance of a fixed-wing turboprop aircraft, characterized in that: include: Based on the characteristics of turbine engines and propellers, the combined characteristics of propeller aircraft power units are determined. By using the double-open state of spoilers, the drag is increased and the lift is reduced to achieve a large-angle descent. The required large-angle descent performance of the aircraft is obtained through modeling and adjustment calculations.

2. The method according to claim 1, characterized in that According to the characteristics of turbine engines and propellers, the combined characteristics of propeller aircraft power units are determined. By using the double-open state of spoilers, the drag is increased and the lift is reduced to achieve a large-angle descent. The required large-angle descent performance of the aircraft is obtained through modeling and adjustment calculations, including: Step 1: Determine the relevant parameters of the turboprop aircraft's large-angle descent through wind tunnel tests and simulations, and clarify the requirements for the dual opening angles of the spoilers and the aircraft's descent speed; Step 2: Compensate the lift coefficient and drag coefficient after the spoiler is lowered according to the effect of the spoiler on the aerodynamic characteristics of the aircraft after it is opened; Step three, according to the aircraft descent speed requirements, convert the descent true speed at each altitude, thereby calculating the descent angle θ and angle of attack α at the corresponding altitude, and further obtain the descent horizontal distance, descent time and descent fuel consumption of the entire descent process.

3. The method according to claim 2, characterized in that The glide-related parameters include: lift coefficient and drag coefficient after the spoiler is lowered; the lift coefficient and drag coefficient after the spoiler is lowered have a corresponding relationship with the angle of attack α, and the calculation formula for the compensation change value of the lift coefficient and the compensation change value of the drag coefficient after the spoiler is lowered is: ΔC L =-0.01308*δ sp ; ΔC D =(0.000001*α+0.000031)*δ sp *d sp -(0.000130*a-0.000554)*d sp ; ΔC L is the compensation change value of the lift coefficient after the spoiler is lowered; ΔC D The compensation value of the drag coefficient after the spoiler is lowered; δsp is the deflection after the spoiler is lowered.

4. The method according to claim 3, characterized in that The descent angle θ and the angle of attack α at different altitudes are calculated based on the force balance formula; the glide-related parameters include: drag and lift; The lateral force balance formula is: The longitudinal force balance formula is: P—given thrust; Q—drag; G—known aircraft weight; Y—lift; α—angle of attack at the same altitude; θ—angle of descent at the same altitude.

5. The method according to claim 4, characterized in that According to the aircraft descent speed requirements, the true descent speed at each altitude is converted to calculate the descent angle θ and angle of attack α at the corresponding altitude, including: a) Divide the height difference between the given descent start height and the descent end height into n equal segments, so that there are several calculation heights H0, H1…Hn+1 on the descent height; b) for the mth calculated altitude Hm, determine the true descent speed; m ranges from 0 to n+1; c) Find out the pulling force value and fuel consumption rate according to the corresponding calculated altitude and true descent speed, and calculate the fuel consumption per hour and per kilometer; d) Set an initial value of the angle of attack α0; e) Calculate the descent angle θ0 according to the longitudinal force balance formula; f) Substitute the descent angle θ0 into the lateral force balance formula and calculate α1; g) Repeat d, e, and f above until |α i -α i+1 When θ is less than or equal to the preset threshold ζ, i and α i As this calculates the descent angle θ at altitude and speed m and angle of attack α m .

6. The method according to claim 5, characterized in that The descent horizontal distance, descent time and descent fuel consumption of the entire descent process can be further obtained, including: Calculate the average velocity V at each adjacent height mpj =(V m +V m+1 ) / 2; Calculate the average descent angle θ of each adjacent height mpj =(θ m +θ m+1 ) / 2; Calculate the average descent rate V at each adjacent height ypj =V mpj sinθ mpj ; Calculate the time and horizontal distance of this descent; The sum of the descending time of each section is taken as the descending time, and the sum of the descending horizontal distance of each section is taken as the descending horizontal distance; Use the average descent speed of each section to find out the pulling force and fuel consumption rate; calculate the hourly fuel consumption rate, and then calculate the fuel consumption of this section; the sum of the fuel consumption of each section is the fuel consumption of descent at a constant indicated speed.

7. The method according to claim 6, characterized in that The method is applicable to medium and large turboprop passenger aircraft, transport aircraft and related platform aircraft.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method according to any one of claims 1 to 7 is implemented.

Images