packaging in a multivariate conceptual design synthesis of the bwb aircraf

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IntroductionPackaging

Conclusion

Packaging in a Multivariate Conceptual Design

Synthesis of a BWB Aircraft

Paul Okonkwo

Co-Author:Prof Howard Smith

Cranfield University

June 3, 2014

Paul Okonkwo ICAAE June 5-6, 2014 New York 1/28
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Conclusion

1 IntroductionOverview of the BWB AircraftAim and Objectives of Presentation

2

PackagingSizingInternal Arrangement of Major Aircraft ComponentsGeometry ParameterisationInterference Detection

3 Conclusion

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Conclusion

Overview of the BWB AircraftAim and Objectives of Presentation

Scope of Presentation


2 PackagingSizingInternal Arrangement of Major Aircraft ComponentsGeometry ParameterisationInterference Detection

3 Conclusion

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Conclusion


Origin of the BWB Aircraft

The BWB aircraft concept originated from the desire to develop aircraftthat is:

Environmentally friendly.

Aerodynamically efficient.

Capable of conveying large payload over long ranges.

At reduced DOC.

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Conclusion


Potentials Opportunities Offered by the BWB Aircraft

The BWB offers....

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Conclusion


Challenges of BWB Aircraft Design

...However, there are several challenges:

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Conclusion


Overview of the BWB Aircraft

This presentation is derived from the development of a design tool for theconceptual design synthesis of the BWB aircraft.

Motivation for this Presentation

Though, packaging is often not considered at the conceptual design

phase of conventional aircraft.However, the BWB uses airfoil with non-uniform varyingcross-section.

Non-uniform cross-section increases the difficulty of positioningobject within the aircraft.

Thus, the need for a packaging algorithm that allows for the efficientuse of internal space.

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Conclusion


Aim and Objectives of this Presentation

Aim of the Presentation

The aim of this presentation is to describe the implementation ofpackaging methodology within a multivariate design synthesisoptimization of a BWB aircraft.

Objectives of the Presentation

Sizing and positioning major aircraft components within the aircraft.

Parameterization of the external geometry of the BWB using ClassShape Transformation technique.

Detect interference between the external surface and internalcomponents.


Sizing
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Conclusion

SizingInternal Arrangement of Major Aircraft ComponentsGeometry ParameterisationInterference Detection




3 Conclusion


I d iSizing
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Conclusion

SizingInternal Arrangement of Major Aircraft ComponentsGeometry ParameterisationInterference Detection

Packaging in Conceptual Design of the BWB

Definition of Packaging:

Packaging is the process of determining the sizes and positions of majorinternal components of an aircraft in order to ensure efficient spaceutilization as well as prevent components interference with the externalgeometry in the conceptual design phase.

Components of Packaging

Sizing.

Positioning of major aircraft components.

Geometry parametrization of the external surface.

Interference detection.


Introd ctionSizing
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Conclusion

gInternal Arrangement of Major Aircraft ComponentsGeometry ParameterisationInterference Detection

Sizing of Selected Aircraft Major Internal Components

Sizing Performed:Sizing the cabin.

Sizing landing gears or undercarriage.

Sizing the engines.

Sizing the baggage compartment.


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Conclusion

Internal Arrangement of Major Aircraft ComponentsGeometry ParameterisationInterference Detection

Sizing the Cabin of a BWB

Bradley Cabin Sizing Method is applied. It involves:Determine the total length required.

Determine the number of bays.

Dimension the length of the centre-line and outer walls of the cabin.

Determining the Total Length Required:


IntroductionSizing

C
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Conclusion


Procedure for Determining the Number of Bays

Assumptions

Width of each bay is set to 12ft.

Maximum number of bays limited to 5.

Minimum length of outerwall of the cabin is 38.5ft.

Maximum length of outerwall is 44.5ft.

Maximum Length for any Number of Bays is Determined By:

Lmax=nlw+ w

2 tanfusn

i=1

(i1)

Where: n=Number of bays.lw=length of the outermost wall.w=Width of each bay.fus=Sweep angle.


IntroductionSizingI t l A t f M j Ai ft C t
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Conclusion


Determining the Length of the Outermost Wall of the

Cabin

Obtained by replacing Lmax in previous equation by lreqand makinglw the subject of the formula.

lw =Lreq

w

ea2 tanfuse

ni=1(i1)

n


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PackagingConclusion


Dimensioning the Cabin

Length of cabin centre-line is obtained from the trigonometricrelation:

xlp=lw+ wea

2 tanfusenbays

Assuming each bay is broken down into 2 columns as shown in the

figure:

Length of outer-walls of each column is derived from:xlea =xlpq

wea

2 tan fuse


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PackagingConclusion


Procedure for Sizing the Baggage Compartment

Assume aircraft of comparable size takes between 32 and 45 ULD3.

Create different combinations of ULD3 abreast as shown on thetable :

Applying multivariate linear regression analysis to obtain length,width and number of ULD3 relationship:

lbgge= nLD3

0.3252wbgge


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PackagingConclusion


Engine Sizing

Rubber-scaling applied.

Thrust Scale Factor is given by:

TSF = Treq

neng TengRef

Length of bare engine is obtained from:

leng= lengRef TSF0.4

Diameter of the bare engine is derived from:

Deng= DengRef TSF0.5

For efficient operation, engine intake inlet and exhaust are also sizedto give:

lebay= leng+linl+lexht


IntroductionP k i

SizingInternal Arrangement of Major Aircraft Components
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PackagingConclusion


Landing Gear Bay Sizing

Sized as a function of the maximum landing weight.

Total length of landing gear is obtained from:

lLG =MLW

KLG

F

Lengths of main and nose gears are functions of statisticallydetermined ratios.

Lengths and widths of bays are functions of wheel diameter and

statistically derived correlation factors respectively.



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PackagingConclusion

g j pGeometry ParameterisationInterference Detection

Implemented Internal Arrangement Used in the BWB

Design Synthesis Packaging Module



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PackagingConclusion

Geometry ParameterisationInterference Detection

Parameterization Using Class Shape Transform Technique

Parameterization refers to a means of describing or representing ageometry by mathematical functions.

The CST parameterization technique is adopted in this study because:

Able to represent all classes of geometry.

Represents a shape with few design variables.

Describes the geometry by a polynomial function which is invaluablein interference detection.

Intuitive and utilise shape variables to characterise the geometry.



SizingInternal Arrangement of Major Aircraft ComponentsG P i i
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PackagingConclusion


Components of CST Technique

As the name implies, CST consists of 2 functions:Class Function

Shape Function

The Class Function:Describes the general class of geometry.

Airfoil shaped geometries with round nose and aft pointed end havethe class function:

C

N1N2 () = ()

N1

(1

)N2

N1 = 0.5 and N2 = 1



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PackagingConclusion


Components of CST Technique

Shape Function:

Defines the specific shape within the class of geometry.

Generates an analytically smooth geometry.

Represented by Bernstein polynomial function of order N.

2-Dimensional Shape Function is given by:

Sui() =

Ni=1

Aui Si()

Si=ki

i

(1

)Ni

ki= N!i!(Ni)!



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g gConclusion


Class Shape Transform for an Arbitrary Wing3-Dimensional Shape Function is given by:

Sui(, ) =

Nxi

Nyj

[Bui,jSyj()Sxi()]

Streamwise shape function, Sxi() =kxii(1)Nxi

spanwise shape function, Syj() =kyjj(1

)Nyj

Complete CST function for an arbitrary wing with twist and dihedralis given by:

u(, ) =C N1N2 ()

Nxi

Nyj

[Bui,jSyj()Sxi()]

+ [T()tan T()] + N()



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ConclusionGeometry ParameterisationInterference Detection

Fundamentals of Interference Detection

Given a point vector P=

pxpypz

A curve represented by a polynomial function z=f(x, y).

Point P is within the curve if:

fu(px, py)>pz

and

fl(px, py)< pz



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ConclusionGeometry ParameterisationInterference Detection

Implementing CST for a 3D Arbitrary Wing

CST function for a 3Darbitrary wing is derived interms of normalised terms.

The normalised terms arederived from the physicalparameters shown in the

figure below:

Calculate non-dimensional :

= xxLE()

c()

Determine :

=2y

bSubstitute and into CSTequations to obtain (, ).

Convert (, ) into physicalz-cordinate:

z(x, y) =(, )CLoc()

Perform interference detection todetermine ifz(x, y) is withinlimits.



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Conclusion




3 Conclusion



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Conclusion

Summary of the Presentation

Packaging is important in BWB design as it ensures efficient spaceutilization and minimizes interference in the conceptual design phase.

Packaging involves sizing and positioning of components, geometryparameterization and interference detection.

Geometry parametrization uses Class Shape Transformation becauseit yields a polynomial and uses only a few design variables.

Interference detection is obtained using the polynomialcharacteristics of the CST functions.



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Conclusion

Thank you for your attention!

Questions?

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packaging in a multivariate conceptual design synthesis of the bwb aircraf

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