Dr. Radhakant Padhi Asst. Professor Dept. of Aerospace Engineering Indian Institute of Science - Bangalore

Transcription

1 Lecture 7 An Introduction to Basic Principles of Atmospheric Flight Mechanics Dr. Radhakant Padhi Asst. Professor Dept. of Aerospace Engineering Indian Institute of Science - Bangalore

2 Aircraft Designs Dr. Radhakant Padhi Asst. Professor Dept. of Aerospace Engineering Indian Institute of Science - Bangalore

3 First to Fly 3

4 Wright Brothers 4

5 5

6 6

7 Commercial Aircrafts High Lift/Drag ratio High fuel efficiency High reliability & safety requirements Good handling quality and passenger comfort All weather operational capability Speed and agility (maneuverability) are not critical 7

8 8

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10 Geometry of Conventional Aircrafts 10

11 Tailless Aircraft On the tailless aircraft the pitch controls and roll controls must both be on the wing. There can be separate elevators and ailerons or they can be combined into one set of controls known as Elevons and still usually has a vertical Fin with a rudder 11

12 Canard Aircraft Horizontal stabilizer and elevators are in front. Advantage: Better control characteristics (including elimination of the non-minimum phase behavior) Drawback: Disturbed flow pattern over the body, good aerodynamic modeling is difficult. 12

13 Force Balance in Flying Vehicles Dr. Radhakant Padhi Asst. Professor Dept. of Aerospace Engineering Indian Institute of Science - Bangalore

14 Basic Force Balance Weight Lift Drag Thrust 14

15 Lift Lift is generated by differential pressure on upper and lower side of the wing Lift Lift 15

16 16

17 Lift 1 = = 2 2 L qscl ρv SCL ρ(h) = atmospheric density (a function of height) V = relative velocity of air S C L q = wetted surface area = coefficient of lift 1 ρv 2 2 = : Dynamic Pressure 17

18 Dynamic pressure Total pressure of any fluid = static pressure + dynamic pressure = ρgh + 1 ρv 2 2 Dynamic pressure of a fluid represents its kinetic energy 18

19 Atmospheric density ρ = ρ e 0 g ( h h ) RT

20 Angle of attack AOA 20

21 Coeff. of Lift vs Angle of attack Stall Region 1 2 ρ 2 L = V S CL Lift coefficient 21

22 Drag 1 = 2 2 D ρv S C D C D = Coefficient of drag = profile drag + induced drag = C + D 0 K C 2 L 22

23 Mach Number M = V / C V = velocity of object relative to medium C = velocity of sound in the medium = velocity of sound in air = 340 m/s at 25 0 C M < 1 Subsonic M = 1 Sonic 0.8 < M < 1.2 Transonic 1.2 < M < 5 Supersonic M > 5 Hypersonic C = γ RT = γ P ρ 23

24 Drag vs Mach number 24

25 Drag Skin friction drag Pressure drag Induced drag 25

26 Skin friction drag It is caused by the interaction of the air particles against the surface of the aircraft. For the airplane, skin fiction drag can be reduced, by keeping an aircraft's surface highly polished and clean. 26

27 Form or Pressure drag Pressure drag is caused by the separation of air that is flowing over the aircraft or airfoil. Note: New generation cars are designed to reduces pressure drag, which leads to better mileage 27

28 Induced drag Induced drag is the drag created by the vortices at the tip of an aircraft's wing. Induced drag is more while maneuvering due to more flow separation over the entire body. 28

29 Thrust Thrust is produced by engines, which counteracts the drag and hence the airplane moves in forward direction. Types of engines Propeller Turboprop Turbofan Turbojet Ramjet Scramjet 29

30 30

31 Propeller engine Spitfire: Used by England in second world war. 31

32 Turboprop engine Used by ATR flights 32

33 Turbofan engine Airbus A380 Largest Passenger Aircraft Engine Used: Either Rolls Royas or GE 33

34 Turbofan engine with afterburner LCA - Light Combat Aircraft Kaveri: An indigenous engine under development at GTRE (Gas Turbine Research Est.) under DRDO 34

35 Ramjet Engines Brahmos: A supersonic cruise missile developed jointly by India and Russia. 35

36 Scramjet X-43 is an experimental vehicle of NASA which used scramjet propulsion to reach up to MACH 9 36

37 Moment Balance in Flying Vehicles Dr. Radhakant Padhi Asst. Professor Dept. of Aerospace Engineering Indian Institute of Science - Bangalore

38 Basic Force Balance Weight Lift Drag Thrust Side force Side force 38

39 Basic Moment Balance Rolling Y Pitching Yawing X Z 39

40 Ailerons Roll 40

41 Aileron Roll 41

42 Elevator Pitch 42

43 Elevator Pitch 43

44 Rudder Yaw 44

45 Rudder Yaw 45

46 Sensors Altimeter: Height above sea level Air Data System: Airspeed, Angle of Attack, Mach No., Air Temperature etc. Magnetometer: Heading Accelerometers: Translational motion of the aircraft in the three axes Gyroscopes: Rotational motion of the aircraft in the three axes GPS: Accurate position, ground speed 46

47 Actuators 47

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