KTH_Scania1

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KTH Vehicle Aerodynamics, 2004-05-07Per Elofsson Fluid Mechanics

Experimental Methods in VehicleAerodynamics

Per ElofssonScania CV AB, [email protected]


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Outline Introduction

Vehicle aerodynamics for trucks

Wind tunnels for automotive testing

Ground simulation Testing & analysis


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Historical evolution

Cd 0.25

Cd 0.6

Cd 1.2 (driver dependant)?


4/24KTH Vehicle Aerodynamics, 2004-05-07Per Elofsson Fluid Mechanics

Scania products

Long-haulage, Construction &Distribution

Ind. & marine engines City buses

Bus chassis, intercity andtourist



40 tons

Aerodynamic drag

Aerodynamic lift is not of great weight CL=0.05 at 80 kph L=150 N

Crosswind stability is of low importance

for trucks (in general) Vehicle soiling is an important field

Vehicle aerodynamics for trucks



Wind-averaged drag

Necessary to take account of crosswind influence on drag Yaw dependance relates to gap between truck & trailer



Truck aerodynamics - characteristics

C d=0.50-0.70

Cd=0.55-0.80

C d=0.65-0.90

Frontal area: 8 -11.5 m 2

f d d



Motivation for improved aerodynamics

Costs for a truck in long-haulage operation

The fuel cost is approx. 1/3 of the operational cost

Driver Fuel

Other

M i i f i d d i



0

20

40

6080

100

120

140

160180

0 10 20 30 40 50 60 70 80 90 100 110 120 130

Hastighet km/h

E f f e k t k W

LuftmotstndRullmotstndVglutning 1 %

Motivation for improved aerodynamics

Driving resistance:

Truck and semitrailer (40t, 80kph) on a flat road: Cd= -0,020 1 % Fuel Economy improvement

P luft ~ v3

P lutn ~ v

P rull ~ v

Fl id M h i


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Fluid Mechanics

New group (founded January 2003)

Staff (2004): Manager Aerodynamicist (mainly EFD)

2 CFD Engineers dedicated to aerodynamics 2 CFD Engineers (climate comfort, underhood

simulations & general flow analysis) 2 Industrial PhD students (1 CFD and 1 EFD)

Plan to expand further (aero-acousticsimulations, vehicle soiling)

E i l d i S i


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FROM:

Full scale development and verification tests atstationary ground conditions

Development tests with 1:2 scale

Experimental aerodynamics at Scania

TO: Full scale development and verification tests at

stationary ground conditions Development testing of 1:6 scale models with moving

ground and rotating wheels 1:2 models for limited test purposes

F ll l t ti


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Full scale testing

Balance measurements(drag, side force & yawingmoment)

Pressure measurements

Flow visualizations Aero-acoustic measurements

Truck or tractor & semitrailer(non-articulated)

DNW Wi d t l


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DNW Wind tunnel

Test vehicle installed in the9.5 x 9.5 m 2 test section

1 6 l d l t ti g


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1:6 scale model testing

Moving belt and rotating wheels Testing at Lola Cars, UK

Tractor & semitrailer model withhigh level of detailing

Cooling air-flow and underhoodsimulation

Almost complete representation ofchassis parts

Model made from aluminium/steelspine, foam blocks, STL andcarbon fibre parts

Lol C rs Wind t nnel


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Lola Cars Wind tunnel



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Both stationary ground & moving belt Testing at different facilities

Main development areas


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Main development areas

Cab shape Cab details

Air deflectors Sun visor, Rear view mirrors

Chassi details Side skirts Wheel deflectors, floorpanels

Scanias unique modular product system makesthe design work a true challenge!

The whole vehicle must be considered


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The whole vehicle must be considered

Trailer modifications havelarge potential ( Cd 0.25) Side skirts, chassis covers Boat-tail, rear end diffusor

Example Concept truck


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Wind tunnel testing during development

Recent CFD simulations- Gain knowledge of external CFD- Boat-tail studies

CFDTesting at DNW



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Cd


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Outline Introduction

Vehicle aerodynamics for trucks Wind tunnels for automotive testing

Ground simulation

Testing & analysis

Performance of automotive wind tunnels


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Performance of automotive wind tunnels

Maximum wind speed: 140 270 km/h Test section (area): 10 - 40 m 2

Fan power: 0.6 - 4 MW

Test section types


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Test section types

Closed TS Open TS

Effect of lateral boundaries

Multi-purpose wind tunnels


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Multi purpose wind tunnels

Provides additional test functionality: Soiling (dirt deposition) tests Climate comfort Thermodynamics & cooling performance tests at

accurate flow conditions

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