EAS 4700 Aerospace Design 1

Transcription

1 EAS 4700 Aerospace Design 1 Prof. P.M. Sforza University of Florida Commercial Airplane Design 1

2 1.Mission specification and market survey Number of passengers: classes of service Range: domestic or international routes Cruise speed: turbofans 0.72<M<0.86 Cruise altitude: 30,000 to 40,000 ft Commercial Airplane Design 2

3 Range versus number of passenger seats for jet transports R=25Np R=20Np R (Range in miles) R=15Np Np (Number of Passengers) Commercial Airplane Design 3

4 The market for commercial aircraft average age (years) aircraft (hundreds) American US Air Delta Northwest United Continental Commercial Airplane Design 4

5 Annual sales of commercial aircraft: Billions of $ current $ constant $ Year (200_) (preliminary) (estimate) Commercial Airplane Design 5

6 Forecast of new aircraft deliveries: New airplane deliveries 25,000 20,000 15,000 10,000 5,000 0 Time period: Total new airplane deliveries=29,400 Regional jets Single aisle Twin aisle Ultra-large Commercial Airplane Design 6

7 Forecast of market value of new deliveries by aircraft type: Market value (2007 $B) Time period: Total market value=$3.2 trillion Regional jets Single aisle Twin aisle Ultra-large Commercial Airplane Design 7

8 Forecast for the change the commercial fleet: Aircraft in the fleet Total number of aircraft: 2007=19, =35,800 0 Regional jets Single aisle Twin aisle Ultra-large Commercial Airplane Design 8

9 Forecast of market value share by region: Market Value Share by Region 4% 8% 2% 25% 38% 23% North America Asia-Pacific Europe & CIS Latin America Middle East Africa Total Market value =$3.2 trillion Commercial Airplane Design 9

10 General trend of take-off weight vs number of passengers 1,400,000 A380 Take-off Weight Wto (lbs) 1,200,000 1,000, , , , ,000 B737 B787 B777 B Number of Passengers Np Commercial Airplane Design 10

11 Market Survey Rigorously examine 3 or 4 existing aircraft which closely satisfy the mission Introduce mission specification, the competitor aircraft, and special attributes of your aircraft Present detailed quantitative data for the competitor aircraft in tabular form, along with 3- views, in an Appendix. Photos of the competitor aircraft appear in Chapter 1 along with airplane descriptions Commercial Airplane Design 11

12 Aircraft data resources Jane s All the World s Aircraft Aviation Week & Space Technology Aerospace Source Book Manufacturer s websites Commercial Airplane Design 12

13 Federal Air Regulations the Federal Aviation Agency (FAA), establishes airworthiness requirements to ensure public safety in aviation. It issues Federal Aviation Regulations (FAR) and FAA Advisory Notes laying down rules for aircraft and their operation. The FAR is Title 14 of the Code of Federal Regulations and is available on-line (Ref. 1-4). Subchapter C, Parts 1-59, deal with aircraft. Commercial Airplane Design 13

14 2. Preliminary Weight Estimate Commercial Airplane Design 14

15 2. Preliminary weight estimate W TO W E = W E + W TFO + W PLC + W F,USED + W F,RES =Take-off Weight =Empty Weight W F W PLC = W F,USED + W F,RES = Weight of Fuel Used+ Weight of Fuel Reserve = Total Fuel Weight =W PL +W CREW = Weight of Payload +Weight of Crew M TFO = W TFO / W TO =(Trapped Fuel and Oil Weight)/W TO M FUEL = W F /W TO = Fuel Fraction Commercial Airplane Design 15

16 Empty weight vs take-off weight W E (1-M TFO -M FUEL ) increasing Fuel fraction needed for mission, including reserves 0 W TO Solve for the empty weight knowing W PLC -W PLC W E = (1 M TFO M FUEL )W TO W PLC = aw TO + b Commercial Airplane Design 16

17 Mission profile W F = W TO W FINAL =W TO (Weight at End of Mission) W F /W TO = M FUEL = 1 W FINAL /W TO = 1 M FINAL Normal Fuel Needed for Mission Diversion Commercial Airplane Design 17

18 Mission profile Segment weight fractions W i / W i -1 exp[-rc j /V(L/D)] exp[-c j /(L/D)] exp[-230c j /V(L/D)] Commercial Airplane Design 18

19 M FINAL =(W11/W10)(W10/W9)(W9/W8).(W2/W1)(W1/W0) M FINAL W W W n = FINAL 11 i W = TO W = 0 i= 1 Wi 1 Final Weight Fraction W W M F, USED W TO LAND, NOM W TO F, RES = M = 1 M M F, USED FINAL F, RES = M + M FINAL F, RES W 5 9 F, RES Wi Wi = = 1 W W W TO i= 1 i 1 i= 6 i 1 Fuel Weight Fraction Used Nominal Landing Weight Reserve Fuel Fraction Commercial Airplane Design 19

20 Mission fuel fraction vs range 1-Mfinal M FINAL = (R-800) 1/ Range (mi) This is the nominal value of the ratio W F,USED /W TO Commercial Airplane Design 20

21 Total fuel fraction vs range 1 - Mfinal+Mres M FINAL +M RES =0.0048R 1/ Range (miles) Nominal ratio of total fuel carried to take-off weight, M FUEL Commercial Airplane Design 21

22 Fraction of trapped fuel and oil M TFO =0.227(M FUEL ) 2/3 (W TO ) -1/3 Mtfo , , , ,00 0 1,000,0 00 1,200,0 00 1,400,0 00 Take-Off Weight (lbs) Correlation for the weight fraction of trapped fuel and oil Commercial Airplane Design 22

23 Empty weight vs take-off weight for 45 airliners Empty weight, We (klbs) Actual weights logwe=(logwto - A)/B We=0.5Wto Take-off weight, Wto (klbs) Commercial Airplane Design 23

24 Empty weight vs take-off weight for 45 airliners Empty weight fraction, We/Wto We/Wto = 1.59/(Wto/1000)^ Take-off weight, Wto (klbs) Commercial Airplane Design 24

25 Estimating aircraft empty weight W E Market survey aircraft W E =aw TO -W PLC 0 Historical correlation W E =0.504W TO -W PLC W TO Commercial Airplane Design 25

26 Cruise fuel requirement V L W R = log e C D W j W 5 V L = exp R W4 C j D Breguet Range Equation Ratio of Weight at End of Cruise to Weight at Start of Cruise 0.76<M< <C j <0.6 14<L/D<18 Mach Number Specific Fuel Consumption Lift to Drag Ratio Commercial Airplane Design 26

27 L/D characteristics of a jet airliner Convair CV-880 L/D ML/D 35kft 23kft 23kft 35kft 5 0 L/D, Power approach L/D, Landing Mach Number Commercial Airplane Design 27

28 Jet fuel characteristics Wide-cut gasoline Jet B JP lb/gal -50C to ,720 Btu/lb 119,000 Btu/gal Kerosene Jet A JP lb/gal -40C to 18,610 Btu/lb 125,800 Btu/gal -50C Commercial Airplane Design 28

29 Design plot for estimating empty and take-off weight of airplane W E Design curves for various values of V, C j, and L/D Design region Market survey aircraft 0 Historical Correlation, W E =0.5W TO W TO -W PLC Commercial Airplane Design 29

30 3. Fuselage Design Commercial Airplane Design 30

31 Fuselage design factors Optimal aerodynamics, reducing aerodynamic drag Suppression of aerodynamic instability Comfortable and attractive seat design, placement, and storage space Safety features to deal with emergencies such as fires, cabin depressurization, etc.; proper placement of emergency exits, oxygen systems, etc. Easy handling for cargo loading and unloading, safe and robust cargo hatches and doors Structural support for wing and tail forces acting in flight, as well as for landing and ground Commercial operation Airplane forces Design 31

32 Structurally optimized, saving weight while incorporating protection against corrosion and fatigue Optimized flight deck, reducing pilot workload and protecting against crew fatigue and intrusion by passengers Convenient size and placement of galleys, lavatories, and coat racks Suppressed noise and vibration, providing a comfortable, secure environment Control of cabin climate including air conditioning, heating, and ventilation Providing housing for different sub-systems, including auxiliary power units, hydraulic system, air conditioning, etc. Commercial Airplane Design 32

33 Major components of fuselage L θ TC L NC L C L TC Commercial Airplane Design 33

34 Circular fuselage cross-section A circle has the greatest cross-sectional area per unit perimeter. The drag of a typical fuselage, which has a rather large fineness ratio (l/d), is dominated by skin friction A circle is strongest under internal pressure. At stratospheric cruising altitudes the outside pressure is 0.2 to 0.3 atmospheres, while the internal pressure is maintained at that at 8,000 feet, or about 0.7 atmospheres. Pressure difference across the thin skin of the cabin ranges from 0.4 to 0.5 atmospheres, or 6 to 7 psi (40 to 50 kpa) A circle more easily accommodates growth in Np in terms of manufacturing since cylindrical sections, called plugs, can be reasonably easily added to so-called stretched versions of a given aircraft. Commercial Airplane Design 34

35 Circular cross-section limitations Limited space outside the passenger compartment for auxiliary systems and cargo. The passenger compartment must be located around a diameter of the circle for the greatest width for seats and aisles. Awkward circular sectors above and below the passenger compartment to house other items. Modern designs have expanded the lower portion of the circular cabin into a more rectangular cross-section in the vicinity of the wing root chord to accommodate more internal carriage. Cabin forward and aft of the wing root is maintained as a circular cross-section, and stretching will require plugs to be added in these regions. Commercial Airplane Design 35

36 Layout of the cabin cross-section Overhead storage bins Pressure shell a a d Passenger aisle Passenger seats Passenger compartment floor Cargo containers Commercial Airplane Design 36

37 Cabin cross-section Overhead storage bins Pressure shell Passenger aisle a a d Passenger seats Passenger compartment floor Commercial Airplane Design 37 Cargo containers

38 Cabin floor plan Commercial Airplane Design 38

39 Correlation of fineness ratio and fuselage dimensions 10 L/d=0.9(L c /d+5) L/d = 0.9(L C /d) (L TC +L +L NC )/d NC = )/d=5-0.1(l 5 C / d) C /d) L C /d Commercial Airplane Design 39

40 Nose and tail cone correlations 4 3 Tail cones L NC /d L TC /d Nose cones L C /d Commercial Airplane Design 40

41 Fuselage drag breakdown L p τ w p τ w D d p τ w L NC L C L TC 0 Base drag D = D + D + D + D + D + D p, NC f, NC p, C f, C p, TC f, TC Commercial Airplane Design 41

42 Nose cone pressure drag is approximately zero Overpressure Underpressure S C p S The overpressure is just about balanced by the underpressure so that the pressure drag on the nose cone is approximately zero, D p,nc ~0 Commercial Airplane Design 42

43 General equation for fuselage drag D = D + D + D + D f, NC f, C f, TC p, BASE D S D c = = c ( Re, M ) wetted + D f qs S qs p. BASE c 4kc ( Re, ) M F = + + F D, fuselage F 3 / 2 3 F Commercial Airplane Design 43

44 Variation of fuselage drag with fineness ratio Cd based on frontal area M=0.85 at 35,000ft altitude Re~3x10^ Fineness ratio Commercial Airplane Design 44

45 Optimal fineness ratio The minimum drag coefficient occurs for F~3 but this would not be a practical fuselage design for safely and efficiently packing passengers For compressible flows where M~1 the slimmer fuselages would have reduced wave drag due to compressibility and they have the advantage of efficient use of space Commercial Airplane Design 45