Multidisciplinary Conceptual Design for Aircraft with Circulation Control High-Lift Systems

Transkript

1 Circulation Control Workshop Multidisciplinary Conceptual Design for Aircraft with Circulation Control High-Lift Systems

2 Overview Contents Introduction Circulation Control Modelling Aircraft Design Process Adaptation Application Examples and Results Summary 2

3 Introduction Motivation Air traffic growth leads to congestion and capacity constraints, especially at large airports Possible solution scenario: transport aircraft (approx PAX) with short take-off and landing field lengths (approx m) could use smaller airports for point-to-point connections use smaller, now unused runways at large airports A more efficient high-lift system is the best means to reduce required field lengths while minimizing the impact on cruise efficiency and thus on economics Conventional ( passive ) high lift systems are not able to meet these increased requirements. Alternative: active high-lift systems 3

4 Introduction Types and Development of High Lift Systems Use of high-lift systems since 1920s Basics of passive systems developed since 1910s, basics of active systems known since before 1904 High performance potential of active systems proven in analysis, lab and flight tests Passive Geometry Nevertheless, so far almost no practical application of active systems. Main problem: Integration in overall aircraft design Active Additional Energy 4

5 Circulation Control Modelling Principle and Modes of Operation Lift coefficient increases with momentum coefficients (AOA and flap angle constant) At the same time, profile drag decreases BLC regime: Prevention of trailing edge flow separation Super-circulation: Creation of a jet flap Behavior of a thin jet on a curved contour: Coanda Effect Jet follows the curved contour and entrains the surrounding flow m& j V j Momentum Coefficient: Cµ = 1 ρ 2 V0 FF 2 Corner point: Attached flow exactly up to trailing edge Optimum BLC: Boundary Layer Control 5

6 Circulation Control Modelling Estimation of BLC With Potential Flow Theory Principle of the multiple lifting line method (Lifting_Line by K.-H. Horstmann et al.): Representation of flaps: a) b) b) Solution of the potential theory analysis a) Linear method, suitable for inviscid flow around thin wings with low camber 6

7 Circulation Control Modelling Comparison of Results With Higher Fidelity Methods Comparison of results from the lifting line method with results from a Navier-Stokes solver* for the optimum blowing point at different flap angles * = used method: DLR Tau code Conclusion: Potential theory method is suitable for BLC modelling! 7

8 Aircraft Design Process Adaptation PrADO Overview PrADO: Preliminary Aircraft Design and Optimization PrADO Input: -Transport Mission -Idea of A/C Shape -Constraints Iteration Control: -Design Analysis -Parameter Variation -Optimization PrADO Output: -Aircraft Geometry -Flight Characteristics -Engine Map -Masses, DOC, yes no Convergence of dependent variables? Design Modules Geometry Modules Engine Map Aerodynamics Aircraft Systems Engine Sizing Cruise Perfo. Take-Off / Landing Sizing and Masses Stability & Control Program Libraries Data Management System DMS Database (ASCII) All available Aircraft Data 8

9 Aircraft Design Process Adaptation Modelling of High Lift Aerodynamics (Conventional) Procedure for designs with conventional high-lift systems: (repeated for cruise, take-off, approach and landing configurations) Database Generation Estimation of Max. Lift Coefficient User input of flap angles User input of max. lift coeff. for airfoil Hörner-Fiecke: C D0 (Ma, H) Lifting_Line: C L (α, Ma) C Di (α, Ma) C M (α, Ma) Determination of lowest AOA with c l = c l,max for one airfoil section Database f(α,ma,h) corresponding C L = C L,max 9

10 Aircraft Design Process Adaptation Modelling of High Lift Aerodynamics (BLC) Procedure for designs with circulation control (repeated for take-off, approach and landing configurations; cruise configuration treated like passive system) Database Generation Determination of Flap Angles User input of C Lmax, Ma Ref For each flap: Calculation of Required Blowing User input of relation between η K, c l,opt, c µ and c p for airfoil section Hörner-Fiecke: C D0 (Ma, H) Lifting_Line: C L (α, Ma) C Di (α, Ma) C M (α, Ma) Database f(α,ma,h) Iteration with Lifting_Line: Calculation of flap angles for C Di,min (i.e. elliptic circulation distribution) New coupling between disciplines! Caclulation of plenum chamber conditions (total pressure, total temperature) through isentropic state change Design of internal ducting system 10

11 Aircraft Design Process Adaptation Design of the Internal Ducting System Generic system architecture, automatically adapted to design: (1 consumer per flap, 1 source per engine) Modular architecture Optional: APU as additional source of pressurized air One-dimensional incompressible streamline theory Estimation of viscous losses and mixing losses Direction of calculation: backwards through system (forward in APU duct) Duct sizing (diameter, wall thickness) system weight 11

12 Aircraft Design Process Adaptation Propulsion System Sizing Starting point: Thermodynamic cycle model (Mattingly) with air offtakes in primary flow path (cooling, air conditioning, etc.; high pressure, low mass flow) Iterative method: Design mode for determination of engine parameters for desired thrust; Off-Design mode for calculation of thrust and fuel consumption at desired operating point Extension: Additional air offtake in secondary flow path for BLC (low pressure, high mass flow possible) Selection of offtake(s) used for BLC according to required total pressure (result of ducting system design); estimation of mixing losses if necessary Previously available offtakes New offtake for BLC 12

13 Application Examples and Results Transport Mission and Reference Design Selection of fixed design parameters: Transport Mission Nr. of Passengers 185 Mass per Passenger 100 kg Add. Cargo Mass 4533 kg Total Payload kg Range 7408 km Cruise Mach Number 0.8 Design Parameters Number of Engines 2 PrADO Geometry Model (Reference Design) Initial Cruise Altitude Wing Reference Area Leading Edge Sweep Wing Taper Ratio km m² Reference design (REF) with conventional flap and slat system input of standard values for flap angles; max. lift coefficient results: Fuselage Geometry Empennage Geometry Landing Gear Geo. constant constant constant Configuration Take-Off Approach C Lmax Landing

14 Application Examples and Results Comparison Active vs. Passive High Lift System Analysis of designs with circulation control high-lift system Goal: increased max. lift coefficients Repalcement of ailerons necessary! PrADO Geometry Model of BLC System 14

15 Application Examples and Results Comparison Active vs. Passive High Lift System Analysis of designs with circulation control high-lift system Goal: increased max. lift coefficients Repalcement of ailerons necessary! PrADO Geometry Model of BLC System 15

16 Application Examples and Results Comparison Active vs. Passive High Lift System Analysis of designs with circulation control high-lift system Goal: increased max. lift coefficients Repalcement of ailerons necessary! Result comparison (BLC w/o ailerons): PrADO Geometry Model of BLC System Description REF BLC Delta max. Lift Coefficient Take-Off % max. Lift Coefficient Landing Static Thrust per Engine Req. Take-Off Field Length Req. Landing Field Length Maximum Take-Off Mass Fuel Mass for Mission Operating Empty Mass Direct Operating Cost N m m kg kg kg /Skm % +14.4% -10.4% -18.9% +2.5% +1.7% +4.1% +1.4% BLC System data: Description Duct System Mass kg max. Mass Flow kg/s max. Pressure Ratio Flap Angle (Ldg.) Deg. Wert(e) /73/78/77 /78/80/80 16

17 Application Examples and Results Design Optimization Through 2D Parameter Variation Series of 35 design analyses with BLC Definition of optimum design considering: Lift-to-drag ration ( t/o field length) Overall mass Direct operating cost Design with optimized wing shape, but conventional high-lift system produced as comparison baseline Initial Design Chosen Optimum 17

18 Application Examples and Results Optimized Design: Variation of Maximum Lift Series of 5 design analyses Change in wing planform causes field length reduction and simultaneous reduction of max. take-off mass BLC has potential to further reduce field length without increasing max. takeoff mass Best compromise if 1500m field length are acceptable: C Lmax,TO = 3.5; C Lmax,LD = 4.0 BLC_opt 18

19 Application Examples and Results Designs With Optimized Wing Planform Result comparison: BLC data and overall aircraft design parameters Description BLC_Basis BLC_opt Delta Duct System Mass kg % max. Mass Flow kg/s % max. Pressure Ratio % Flap Angle (Ldg.) Deg. 74/73/78/77 /78/80/80 54/54/59/63 /64/59/41 PrADO Geometry Model (BLC_opt) Description REF_Basis REF_opt BLC_opt vs. Basis vs. opt max. Lift Coefficient Take-Off % +25.3% max. Lift Coefficient Landing % +17.7% Static Thrust per Engine N % +3.4% Req. Take-Off Field Length m % -10.4% Req. Landing Field Length m % -17.6% Maximum Take-Off Mass kg % -0.3% Fuel Mass for Mission kg % -1.2% Operating Empty Mass kg % +0.1% Direct Operating Cost /Skm % -0.3% 19

20 Summary Among active high-lift systems, Circulation Control seems especially promising for reduction of aircraft field length (good ratio of lift increase to required energy) The complexity of integration into the aircraft makes it necessary to consider the active high-lift technology in the early design stages Potential theory methods are suitable to model the aerodynamic effects of Circulation Control in the Boundary Layer Control regime Adaptation of a conceptual aircraft design process requires changes in the modules for aerodynamics, propulsion system and aircraft systems (design of an internal ducting system) Results of the design process are plausible applied models seem to work well Design of an economically competitive aircraft with significantly decreased field length seems possible, but requires compromises to be made in overall aircraft design 20

21 Thank You Very Much for Your Attention! 21