Simulation of the Tail-Pipe Emissions for a Heavy Duty Diesel ...

Simulation of the Tail-Pipe Emissions fora Heavy Duty Diesel Engine in GT -Power

GT-Suite Users MeetingOct. 20, 2012, Frankfurt/Main

Dr. Joachim WeißDipl.-Ing. Markus Raup

Dr. Thorolf Schatzberger

Dipl.-Ing. Friedrich ForsthuberDipl.-Ing. Thorsten Krenek

Assistant Prof. Dr. Thomas Lauer

GT-Suite Users MeetingSimulation of the Tail-Pipe Emissions for a Heavy Duty Diesel Engine in GT-Power

Oct. 22, 2012 | Frankfurt/Main | F. Forsthuber | Slide 2

Content

� Introduction

� Simulation model

� Validation Results

� Variation of exhaust system

� Optimization – mean value model

� Summary & outlook



IntroductionMotivation

� State-of-the-art engines are complex systems with numerous degrees of freedom

� Fuel efficiency is strong demand from the customer

� Emission regulations getting continuously more severe

� Comprehensive model required to study system behavior

� Simulation model as basis for numerical optimization



IntroductionEngine & Simulation Software

Heavy duty engine for truck and bus application:

� In-line 6-cylinder Diesel engine

� High-pressure common rail injection system with multiple injection pulses

� Two-stage turbo charging with intercooler

� Cooled external EGR

� Selective catalytic reduction (SCR)

� Diesel particulate filter (DPF)

� Diesel oxidation catalyst (DOC)

Simulation Software

� GT-Suite™ for simulation of engine and aftertreatment


Oct. 22, 2012| Frankfurt/Main | F. Forsthuber | Slide 5

Simulation ModelCombustion Modeling – Spray Model

Source: Hiroyasu et al., SAE-Paper 930612

Spray model• Input: injection rate vs. time

• Spray divided in parcels

• Evaporation and heat release for individual parcel is computed

• Global heat release is summed up

• NOx model based on extended Zeldovich mechanism



Simulation ModelCombustion Modeling – Resulting Cylinder Pressure



Simulation ModelAftertreatment Modeling

Flow components (catalyst bricks)

Coupled with reaction kinetics objects



Simulation ModelAftertreatment Modeling – Reaction Kinetics

Reaction kinetics objects account for:

� Bulk diffusion

� Surface storage

� Gas and surface reactions

Adsorption of ammonia

Desorption of ammonia

Oxidation of ammonia

Standard SCR reaction

Slow SCR reaction

Fast SCR reaction



Simulation ModelOverall System Modeling

Predictive engine model for fuel consumption and NOx formation

Aftertreatment model with detailed reaction kinetics

Combination of the two parts

required

� One single model with two separated flow circuits

� Boundary conditions of circuits passed through by a control object

� Appropriate timestep for each circuit to provide fast runtimes



Validation ResultsSteady-State Engine Operating Points – 50% Load

� Comparison between measurements and simulation results of different operating points



Validation ResultsSteady-State Engine Operating Points – Parameter Variation

Variation of air ratio (Lambda) in one specific operating point

Engine control strategy: Increasing Lambda � decreasing EGR



Validation ResultsAftertreatment

� Steady-state operating point� Constant exhaust mass flow, composition and temperature� Injection of urea solution (hyperstoichiometric)� NOx conversion and NH3 storage starts� Cut-off of urea injection



Validation ResultsAftertreatment

� WHTC based transient cycle

� Last section of cycle – urea dosing and NOx conversion start

� Measured raw emissions as input for afterteratment model



Validation ResultsTransient Cycle

� Combined model with detailed engine and aftertreatment model

� Transient cycle based on the Worldwide Harmonized Transient Cycle (WHTC)

� Fully transient controls for engine and atftertreatment operation analogous to the hardware engine control



Validation ResultsTransient Cycle – Parameter Variation

� Variation of air ratio (lambda factor) over the entire transient cycle



Validation ResultsTransient Cycle – Parameter Variation



Variations of Exhaust System

Base Reduced lengthAir-gap

insulation 1Air-gap

insulation 2

be 100% +0,2% -0,1% +0,1%

NOx 100% -0,3% -0,3% -0,7%

NOx,EOP 100% -14% -13% -19%

tAdBlue 100% -5,1% -4,9% -6,2%



Optimization – Mean Value Model• One neural network for

each output parameter:• IMEP• FMEP• Volumetric Efficiency• Exhaust temperature• NO emissions• NO2 emissions

• 15,000 steady-statesimulations for neuralnetwork training

Runtime reduction:15 hrs → 45 min for a 1800 s transient cycle



Optimization – Mean Value Model

� Design of Experiments

� Full factorial

� 720 simulated transient cycles

� Neural network as objective function

� Minimization of BSFC

� Boundary condition:

NOx,EOP ≤ base variant

� Optimized Parameters:− Lambda Multiplier

− Charge pressure multiplier

− Site density

− SCR catalyst length



Optimization – Mean Value Model

Final OptimizationResults

BSFC -2.1%

NOx -4,9%

NOx,EOP -4.0%

Optimized parameter set combined with insulated exhaust pipes

Optimization result verified with detailed model



Summary & Outlook

� Summary− Predictive simulation model containing engine and aftertreatment

− Phenomenological Diesel combustion model for fuel consumption and NOx formation

− Aftertreatment with reaction kinetics (NH3 storage and NOx conversion)

− Sensitive to the relevant parameters of engine and aftertreatment operation

− Steady state operating points and transient cycles

− Neural network model for faster runtimes

− Numerical optimization methods

� Outlook− Extended reaction kinetics

− Advanced numerical optimization methods (heuristic algorithms…)

Thank you for your attention !

Dipl.-Ing. Friedrich [email protected]

Simulation of the Tail-Pipe Emissions for a Heavy Duty Diesel ...

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