Post on 09-Apr-2018
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CFD ANALYSIS OF PZEV EXHAUSTCFD ANALYSIS OF PZEV EXHAUSTMANIFOLDSMANIFOLDS
Srikanth Ranganathan
CFD Section
Analytical Powertrain
Ford Motor Company
Dearborn, Michigan
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OBJECTIVEOBJECTIVE
To demonstrate a FLUENT based technique for evaluating a
PZEV exhaust manifold for PETA effectiveness
Cylinders
Exhaust
ValvesPETA Tube
PETA Air
Inlets
Substrate
PZEV Partial Zero Emissions Vehicle
PETA Ported Electric Thermactor Air
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PETA ExhaustPETA Exhaust -- IntroductionIntroduction
During the initial 20-30 seconds after engine start the air-fuel
mixture is run extra rich.
Prior to the catalyst brick, fresh air is injected from the PETA
tube directly into the exhaust gases.
The partially combusted fuel laden exhaust gas that is hot
but depleted of oxygen is spontaneously combusted again in the
manifold volume leading to increase in gas temperature.
Early elevation of substrate temperatures ensures an early
conversion of exhaust gases in the catalytic converter and thus
lowered emissions
PETA Effectiveness is measured by temperature increase of
exhaust gases from port to CAT face
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PETA Exhaust Flow RegimePETA Exhaust Flow Regime
Transient (Engine Cycle)a
Moving boundaries (Exhaust Valves)r
Compressibler
Multi-species mixing (Exhaust gases + Air)a
Combustion (Fuel + O2
Products + Heat)a
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Analysis ProcedureAnalysis Procedure
Physical Model (TGRID)Ports + Manifold + Converter + PETA
Transient Inlet
Mass Flux1-D Tool (GT-Power)
Chemistry Model (PrePDF)Species, Composition, Stoichiometry,
Streams, PDF, Heat Transfer, Rates
CFD Model (FLUENT)
Engine Cycle Simulation
(3-5 Cycles)
Convergence
No
Flow Temperature
Increase
Yes
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Model & DataModel & Data
I4 PZEV Exhaust @ 1500 Engine RPM (Time Period = 0.08s)
Non-Premixed Combustion:
1 Fuel + 1 Oxidizer Stream
4 Fuel Inlet: 923K [0.9N2 + 0.1CH4]
1 Oxidizer Inlet: 300K [0.79N2 + 0.21O2]
Flame Sheet Model (Infinite rates, Mixed-Is-Burned)
Reaction Stoichiometry: CxHy + (x+y/4)O2 xCO2 + (y/2)H2O
CH4 + 2O2 CO2 + 2H2O
Outlet: Atmospheric
Adiabatic Walls
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I4 PZEVI4 PZEV -- ResultsResults
Engine Cycle Averaged:
Exhaust Manifold Inlet Temperature = 923K
CAT Face Temperature = 1050 K
Temperature Growth = 127K
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CHCH44 on Coreon Core
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CHCH44 on C/Son C/S
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OO22 on Coreon Core
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OO22 on C/Son C/S
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Temperature on CoreTemperature on Core
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Temperature on C/STemperature on C/S
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AdvantagesAdvantages
Relatively quicker turn around time than full fledged
combustion model; Crucial as an optimization tool
PDF approach to turbulence and flow induced
mixing/combustion
Energy equation is not solved; Temperature determined
from scalar distribution
DisadvantagesDisadvantages
Reaction rates do not play a role
No intermediate species simulation
Risk of combustion/temperature over prediction
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ConclusionConclusion
Demonstrated a simple and quick FLUENT based CFD method
for evaluation of PETA effectiveness
Suitable for optimization studies of PETA/Exhaust Manifold design
A/F ratio
PETA air flow rate
Air injection location and angles
Manifold core shape