esss numerical analysis

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Numerical anal sis offluid flow inside airintake system

Numerical analysis of fluidflow inside air intake system

Regis AtaidesMartin Kessler Marcelo Kruger Geraldo Severi Jr.Cesareo de La Rosa Siqueira

Walter ZottinWagner Trindade

EASC 20094th European Automotive Simulation Conference

Munich, Germany6-7 July 2009


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Agenda

Introduction

Goals

Description of the numerical model

Geometry and mesh

Boundary conditions

Numerical model

Results

Comments

Introduction Air intake system is responsible for capturing and cleaning

air from vehicles surroundings, before allowing it to beinjected into the engine

In addition, information about the mass flow is extractedfrom the flow and sent to the fuel injection system, which

can calibrate the proper mixture to any specific condition. Inorder to allow for a reliable reading, the flow must be wellbehaved around the Mass Air Flow Sensor (MAFS)




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Goals Develop a computational model to study the flow inside Air

Intake Systems (AIS) Two geometries have been evaluated and the second one with two

Evaluate the pressure drop for the entire system andidentify local pressure losses. In addition, identify the flowpattern around the MAFS

Numerical model - Geometry

Model 1 Model 2

MAFS




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Numerical model Model 2 with Honeycomb

Model 2 HC1

Model 2 - HC2

The honeycomb is placedright before the MAFS toreduce the turbulence level

Boundary conditions (Same for all models)

Outlet:Pressure

Inlet: Mass flow

Filtrating element:Inertial resistanceViscous resistance




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Computational Mesh

Extension toavoid

Mesh with around2,6 million cells forboth Model 1 and 2

the outlet

Computational MeshExtension

Mesh withHoneycomb 1

with 3.1 millionsof elements Mesh with Honeycomb 2

with 4.6 millions ofelements




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Numerical model

Assumptions: Steady-state flow; Incompressible; Turbulent.

Fluid properties: Air

ens y: , g m ; Viscosity: 1,7894e-05 kg/m/s;

Results Pressure on the walls

Model 1 Model 2

Model 2 HC1 Model 2 - HC2




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Results Pressure drop along the model Average pressure taken at the following surfaces:

In

Elem-Top

DirtyAirDuct

POut

Elem-BotCleanAirDuct

Results Pressure drop

P r e s s u r e

Mod 1

Mod 2

Mod 2 HC1

Mod 2 HC2

I n

D i r t y A

i r D u c

t

E l e m_

t o p

E l e m_

b o t

C l e a n

A i r D u

c t

A f t e r

H o n e

y C o m

b P o

u t




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Results - Uniformity

In order to identify how well behaved is theflow at the outlet, the following uniformityn exes w e app e ere:

- Eccentricity;- Gamma;- Velocity ratio;

Results Uniformity Coefficients - Definitions

Eccentr ic ity ( ): Evaluate how distant from the center themaximum velocity point is:

1: In the border (worst)22

y x +=

For an ellipsis:

( )major

mid v x L

x x = max

2

( )or

mid v y L

y y

min

max2

=




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Gamma ( ): Evaluate how uniform is the velocity distribution ona given surface.

amma = : n orm es

Gamma = 0: Non-uniform (worst)

totalavg

iavgi

Av

Avv2

1 =


Velocity ratio (v ratio ): Is the ratio between the maximumand the average velocity on a surface. Around 1 is

e er.

ratio vvv max=




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Results Uniformity CoefficientsLDV LJ1

Uniformity coefficients

LKF

Ecc Gamma Velocity ratio

Model 1 0.74 0.96 1.10

Model 2 0.75 0.97 1.13

Model 2 HC1 0.31 0.93 1.19

Model 2 HC2 0.53 0.93 1.20

Results Velocity vector at the MAFS regionModel 1 Model 2

Model 2 HC1 Model 2 HC2




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Results Turbulence intensity around the Honey Comb

Cut plane before theHoney Comb

Model 2 HC1

Model 2 HC2

Cut plane after the Honey Comb

Results Turbulence intensity around MAFS region

Model 2Model 2 HC1

Model 2 HC2

The Honey comb reducesthe turbulence intensity

around MAFS region




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Results Pathlines

Model 1Model 2

Model 2 HC1 Model 2 HC2

Comments

Both honeycomb designs reduced the turbulence intensity at the MAFSregion when compared to the model without it;

The pressure drop, on the other hand, increased slightly with thehoneycomb;

The pressure drop curve was affected only at the honeycomb region,keeping the same behavior in the rest of the domain;

The eccentricit at a cut lane u stream the MAFS chan ed from 0.31in the first configuration with honeycomb (Model 2 HC1) to 0.53 in thesecond (Model 2 HC2).



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