항공우주공학개론dasan.sejong.ac.kr/~haedong/Intro_AAE/aerointro2007S.… · · 2007-04-16Sejong University Propulsion Aerodynamics Lab. 1-1. 대기권(Atmosphere) 압력:

Sejong University Propulsion Aerodynamics Lab.

항공우주공학 개론

세종대학교 항공우주공학과

2007. 봄학기

김 해동

Introduction to Aerospace Eng.


1-1. 대기권 (Atmosphere)

음속 a : 340.43 m/sec 압력 : 760mmHg, 101.3 kPa

For Air,

밀도 : 1.225 kg/m^3

우주공간

저지구궤도위성

온도상승, 전리층

온도하강

Jet stream, 오존층

대류, 기후 현상

11-50 km성층권 (Stratosphere)

50-80 km중간권 (Mesosphere)

80-300 km열권 (Thermosphere)

300-2000 km극외권 (Exosphere)

2000 km +외공간 (Outer Space)

온도 : 15 C , 288.16 K

ICAO 표준대기 (SLS : Sea Level Static)

대류권계면 (Tropopause)

0-11 km 대류권 (Troposphere)


1-2-1. 항공기의 분류-민간항공기

제약 없음특수 항공기 X (Experimental)

동력 50 kW 이하인 활공기5.0동력활공기

Wto < 600 kg, Catapult, Winch4.0Class III

Wto <600 kg,일부곡예,견인비행5.0Class II

Wto < 600 kg, 곡예/견인 비행6.5Class I활공기

Glider

Wto > 9,000 kg+2.0 T Class B

수송 항공기, 엔진 2 개 이상+2.0 T Class A

Wto < 2,700 kg3.5N (Normal)회전익

항공기

수송 항공기2.5 +T (Transport)

Wto < 5,700 kg, 경사 60도 이내2.5-3.8N (Normal)

Wto < 5,700 kg, 경사 60도 이상4.4U (Utility)

Wto < 5,700 kg, 모든 비행6.0A (Acrobatic)

비행기

Airplane

DescriptionLoad FactorCategory


1-2-2. 항공기의 분류-군용항공기

Y (Prototype)M (Mission)

X (Experimental)L (Liaison)

V (Vertical Take-Off)K (Tanker)

U (Utility)H (Helicopter)

T (Trainer)F (Fighter)

S (Strategic Mission)E (Electronic Warfare)

R (Reconnaissance)C (Cargo)

P (Patrol)B (Bomber)

O (Observation)A (Attack)


1-3-1 What is Aerospace Science ?Aerospace Science :

A Science Field Related with Aircrafts, Rockets, and Space Vehicles

Who has done the first powered human flight ? :

Who : Wilbur & Orville Wright

When : December 17, 1903

Where : Kitty Hawk, North Carolina

How Long : 12 Seconds


1-3-2 Wright Flyer

Wingspan : 12.3 m (40 ft 4 in)

Length : 6.4 m (21 ft)

Height : 2.8 m (9 ft 3 in)

Weight, empty : 274 kg (605 lb)

Engine : Gasoline, 12 hp

Manufacturer :

Wilbur and Orville Wright,

Dayton, Ohio, 1903


1-3-3 Before 1903Pioneers in Aerospace Sciences• Leonardo Davinci

: Conceived Helicopters • Sir George Cayley

: Experimented Gliders• Otto Lilienthal

: Flew Gliders 2000+ Times• Octave Chanute

: Flew Gliders• Samuel Langley

: Tried Powered Flight


1-3-4 Wright Gliders• Inspired by Lilienthal and

Chanute• Flied Many Gliders• Helped Flyer Design• Control Mechanisms • Flight Experiences • Wind Tunnel Experiments• Estimated Engine Power


1-3-5 Aerospace Milestones

• Trans-Atlantic Flight: Charles Lindbergh (1927)

• Helicopter (1936)• Jet Aircraft (1939) • Rocket (1942)• Supersonic Flight (1949)• Passenger Jet (1954)• Orbit Spacecraft (1957)• Lunar Landing (1969)• Space Exploration• Super Transport :

(B747 A380)


1-3-6 Korean Aerospace Industry• 조선시대 : 화차• Started in 1953 : 부활호• 2 Stage Rocket : 1959• License Production

• 1977 : 500 MD Helicopter• 1981 : F-5E/F Fighter• 1990 : UH-60 Helicopter• 1991 : KF-16 Fighter

• KT-1 : 1997• UAV : 1998• T-50 / A-50 : 1992 – 2002• Satellite : 우리별 1992 / 무궁화

1995 / 아리랑 1999• Rockets : KSR-1 (1993),2 (1998),3

(2002)


1-4-1. 항공기 설계과정

1. 성능요구조건 : ROC (Requirements of Capabilities) RFP (Request For Proposal) 에 명시

• Specified Requirements• Derived Requirements

2. 운용개념 : CONOPS ( Concepts of Operations )3. 개념설계 ( Conceptual Design ) : 소수인원, 형상설계, 성능/비용 분석

4. 예비설계 (Preliminary Design) : 풍동시험, CFD 해석, Subsystem 설계

• PDR (Preliminary Design Review)5. 상세설계 (Detail Design) : 상세구조설계, 구조시험, 공정설계

• CDR (Critical Design Review)6. 시제기 생산 (Prototype Production) : 3-5 대 생산, 생산성 향상

7. 비행시험 (Flight Test) : 안정성, 설계수정, 비행제어 프로그램 수정

8. 양산 (Production)9. 후속지원 및 교육 (ILS : Integrated Logistics Support)• PDR, CDR 에서 요구성능을 만족 못할 경우, 이전단계 반복수행


1-4-2. 성능요구조건

1. 중량 : 항공기 자중 / 유상하중 / 성장가능성

2. 항속거리, 체공시간, 3. 속도 : 순항 / 실속 / 최고 / 상승 / 가속

4. 이착륙거리

5. 탑승인원 : 승무원 / 여객

6. 운용호환성 / 정비성 / 지상장비 / 후속지원

7. 탑재장비 성능 : 통신 / 항법 / 레이다 / 무장

8. 탑재엔진 성능 : 연료 소모율 / 정비성

9. 비용 : 개발 / 생산 / 운용 / 정비 / 후속지원

10. 생산착수시점 및 생산속도

11. 금융지원


1-4-3. 운용개념

Mission Profile (출처 : J. Mattingly, Aircraft Engine Design, 2nd Ed. Page 14. )


1-5-1 Definitions & Functions of a Aircraft

Reference : http://www.grc.nasa.gov/WWW/K-12/


1-5-2. Forces amd Moments on Aircraft1. Translational Motion (병진 운동) : 3 axes

Equilibrium Condition (평형조건) : Lift(양력)=Weight(중량), Thrust(추력)= Drag (항력)

2. Rotational Motion (회전 운동) : 3 axes

Equilibrium Condition (평형조건) : Pitching / Rolling / Yawing Moment = 0

Reference : http://www.grc.nasa.gov/WWW/K-12/


1-5-3 Aircraft Cockpits

Bf 109 GControl Stick

Boeing 777Glass CockpitControl Yoke

F-16MFD, HUD

Side Joystick


1-5-4 Pitch Motion

• Stabilator : Stabilizer + Elevator• Pull/Push Control Stick : Elevator Up/Down• Elevator Up / Down : Pitch Up / Down• Max 60 / 75 lbs Stick / Wheel• Max 10 lbs Prolonged Application


1-5-5 Roll Motion

• Elevon : ( Aileron + Elevator ) for Tailless Airplanes• Moving Control Stick Right/Left : Right Aileron Up/Down, Left Down/Up• Max 30 / 60 lbs Stick / Wheel• Max 5 lbs Prolonged Application


1-5-6 Yaw Motion

• Kicking Right / Left Pedal : Right Aileron Up / Down, Left Down / Up• Temporary : Max 150 lbs• Min of 5 lbs / degree


1-5-6 Yaw Motion

• Kicking Right / Left Pedal : Right Aileron Up / Down, Left Down / Up• Temporary : Max 150 lbs• Min of 5 lbs / degree


2. Aerodynamics- IntroductionMost forces and moments are generated on wings (or

lifting surfaces).Fighters have significant contributions from fuselage. Forces and moments are calculated using wing area S.


2-1. Prediction and Measurements• Aerodynamic Center (AC) : A point at which all aerodynamics

forces and moments are assumed to be applied.• Center of Pressure (CP) : A point at which moment vanishes.• Prediction & Measurements of Forces and Moments

– Theoretical Analysis – Computational fluid dynamics (CFD) - Simulation– Wind tunnel experiments : Still the primary tool– Flight tests


2-1-2 Forces and Moment on AirfoilCourtesy of http://www.aviation-history.com/theory/airfoil.htm

Lower pressure is generated on upper wing surfaces.

Higher pressure on lower surfaces pushes the wing upward, generating the lifting force.

Downwash is generated behind the wing, due to Newton’s principle.

Section of the wing is called ‘ Airfoil’.On wing tips, trailing vortices are

generated.


2-1-3 Airfoil Geometry1. Airfoil : 2 dimensional cross section of a lifting surface (날개의 2차원 단면)

First patented by H.F. Philips in 18842. Terminology and Design Parameters

Max. Thickness & Max. Camber / Locations of Both / Leading Edge Radius

NACA 4-Digit Series: NACA 4 4 1 2 4 : max camber in % 4 : max camber position in 1/10 of c 12 : max thickness in % chord


2-1-4 Forces and Moment on Airfoil1. Lift : Force component normal to air flow direction

(per unit span) [N/m]

2. Drag : Force component parallel to air flow direction(per unit span) [N/m]

3. Moment : Moment on aerodynamic center(per unit span) [Nm/m] C : chord, U:air speed, : air density, : lift coefficient,

: drag coefficient, : moment coefficient


2-1-5 Airfoil History

– Laminar airfoil (1940’s) : Suppress transition to turbulent flow and reduces viscous drag.

– Super-critical airfoil ( 1950’s 초임계익형) : Retards shock wave formation and reduces shock strength, reducing wave drag and increasing drag divergence Mach number.


2-1-6 Airfoil Characteristics – Cp & PolarCourtesy of Prof. Mark Drela, MIT Ph.D. thesis, 1985


2-1-7 Airfoil Characteristics – Cl , Cd & CmLift Coefficient :

Almost linearly proportional to angle of attack untill it reaches stall angle.

For cambered airfoils, For symmetric airfoils,

Drag Coefficient : Slowly increase as angle of attack increases

Pitching Moment Coefficient : Slightly decrease as angle of attack increases.Most cambered airfoils have negative moment.


2-2-1 Wing Geometry


2-2-2 Lift and Drag of Aircraft or WingMost lift, drag and moment are generated on wings.

Lift Coefficient : Lift slope is lower than airfoil due to downwash.Stall occurs at a higher AOA than airfoil.

Drag Coefficient : Parasite Drag (or Profile Drag ) - Viscous / Form DragInduced Drag – Downwash

(e : Oswald’s coefficient , 0.7- 0.85 )Wave Drag – Shock Waves

Lift to Drag Ratio Gliders : 20-50Passenger Jets : 15-20Fighters : 6-13

At maximum , we can have the most fuel efficient flight.


2-2-3 High Lift Devices• For shorter take-off run and safer landing, we need more lift.

Increase wing area. & Increase maximum lift coefficient. (But drag increases)– Increase camber of the wing.– Increase angle of attack.– Suppress separation.

• Slat• Flap• Lift augmentation


2-3-1 Flow Properties – Viscous Flow• Fluid has viscosity, generating viscous drag.• Reynold’s number Re

Density of fluidCharacteristic LengthFlow speed.Viscosity coefficient

Lower Re means more prone to separations, and more pressure drag.• Turbulent & Laminar flow

Laminar flow has less viscous drag,but, more prone to separation.

Turbulent flow occurs at high Re flow.(more kinetic energy)

Turbulent flow has more viscous drag,but, less separation & pressure drag.

Courtesy of http://www.aviation-history.com


2-3-2 Flow Properties – Transition• Reynold’s number of aircrafts

- Turbulent Flow- Turbulent Flow- Laminar Flow

Transition occurs at Re in 100,000 range. Laminar airfoils suppress transition and reduces viscous drag.Sometimes, forced transition devices are used on wings to prevent

separations. • Cylinder & Golf Ball

Separation region behind 2D cylinder or sphere decreases as Re increses.(reduces pressure drag.)

Transition to turbulent flow also suppresses separation and reduces pressure drag. But, this increases friction drag.

Golf balls have dimples to generate turbulent flow.


2-3-2 Flow Properties – Cylinder Flow

• For low Re, viscous force dominates.

• Laminar flow has bigger separation region.

• As Re increases, separation region decreases.

• Turbulent flow has smaller separation region.


2-3-3 Flow Properties – Compressibility• Compressibility : Density changes as flow speed U changes.• Mach Number

• Flow speed regime– Subsonic (아음속) : M < 0.8– Transonic (천음속) : 0.8 < M < 1.2 - Supersonic Pocket– Supersonic (초음속) : 1.2 < M < 5.0 - Shock waves– Hypersonic (극초음속) : 5.0 < M - Nonequilibrium flow

Courtesy of NASA

F-18 at M = 1.41 X-15 at M = 3.7 X-15 at M = 6.0


2-3-4 Flow Properties – Transonic Airfoils• As M increases, supersonic pocket

area and shock strength increases. • Supercritical airfoil retards shock

formation and reduces shock strength.• Shocks on control surfaces, induce

oscillatory ‘Buffet’, leading to failure.• Stabilator (or all moving tail) with

transonic airfoil reduces ‘Buffet’.

Courtesy of NASA

Courtesy of KAIST


2-3-5 Flow Properties – Supersonic Pocket

Courtesy of 유용원의 군사세계


2-3-5 Flow Properties – Drag Divergence

• As M closes to 1, drag sharply diverges. • Thin airfoil, supercritical airfoil increases

drag divergence Mach number.• Sweepback reduces effective Mach

number, increasing drag divergence Mach number.


2-3-6 Flow Properties – Area Rule• R. Whitcomb’s found that elliptic distribution of cross-sectional area

minimizes wave drag.


3. Flight Mechanics & Stability, Control 3-1. Level Flight ( U = constant , 등속수평비행)


3-2. Required & Available Power


3-2. Constant Climb• Force Balance

• Rate of Climb

• Ceiling (상승한도)Absolute Ceiling (절대상승한도) : RC = 0Service Ceiling (실용상승한도) : RC < 100 [ft/min]Operation/Combat Ceiling (운용상승한도) : RC < 500 [ft/min]


3-3. Constant Descent• Force Balance

• Rate of Descent

• Glide Slope (활공각)

We can find by measuring theglide slope = distance / altitude loss.


3-4. Coordinated Turn (수평선회비행)• Force Balance

• Load Factor (하중계수)

• Turn Speed Turn Radius


3-4-1. Coordinated Turn (수평선회비행)


3-5. Take-Off and Landing Run• Force Balance

– Take-Off

– Landing

• Deceleration Method– Spoiler / Speed Brake– Wheel Brake– Thrust Reverser– Drag Chute– Arresting Wire / Net

Courtesy of Bemil


3-5-1. Take-Off and Landing Run• Deceleration Method

Courtesy of Wikipedia


3-6 Take-Off and Landing

• Runway Designation

• Takeoff Speed Definition

• Landing under Sidewind


3-2 Constant Climb

• CG Measurement : Balances & Ropes

• Calculation : CAD software (CATIA, UG, Pro-E)


3-5 Wing Positions

• High Wing

• Mid Wing

• Low Wing

• Good lateral stability• Large engine / easy loading• Short landing gear• Structural weight increases• Large transport : C5, C141, An124

• Good lift to drag ratio• Complicated fuselage structure / landing

gear• Limited space utilization• Fighter : Lafale, F104, MIG 21

• Simple fuselage structure• Short landing gear / Weight saving• Maximum space utilization• Passenger Jets, Fighter, Attack


4-1. Aircraft Structure Types


4-2. Material - Military Jet Aircarft


4-3. Material - Civil Jet Aircarft


4-4. Material Properties

Documents

항공우주공학개론dasan.sejong.ac.kr/~haedong/Intro_AAE/aerointro2007S.… · · 2007-04-16Sejong University Propulsion Aerodynamics Lab. 1-1. 대기권(Atmosphere) 압력: