Experimental procedures for efficient after-treatment ...• a low temperature direct reaction with...

CLEERS Workshop 2010 April 21st, 2010

Experimental procedures for efficient after-treatment model calibration

Maria E. Kalogirou Exothermia SA Laboratory of Applied Thermodynamics, Aristotle University Thessaloniki Greece

Matyáš Schejbal Laboratory of Applied Thermodynamics, Aristotle University Thessaloniki Greece

Grigorios C. Koltsakis Exothermia SA Laboratory of Applied Thermodynamics, Aristotle University Thessaloniki Greece

21 April 2010 CLEERS Workshop 2010

CLEERS Workshop 2010 April 21st, 2010 2

Background - motivation

simulation software + user interface

balance equations

reaction kinetics

numerical

methods

!   Advanced after-treatment simulations tools are available.

!   Knowledge of accurate reaction kinetics remains the main challenge.

!   Target of this work is to derive realistic reaction rates for soot oxidation with emphasis on CRT (DOC+DPF) operation (only uncat DPF soot oxidation will be shown).

!   Experimental methodology –  real diesel soot –  calibration with synthetic gas tests –  validation on engine bench

in combination with axisuite® model platform.


Uncatalyzed soot oxidation reactions review

Calibration targets of soot oxidation with O2 and NO2: - set of reactions (how many and which reactions?) - kinetic parameters (activation energies, pre-exponential factors)

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Methodology

model based validation valid kinetic parameters

small-scale experiments + controlable & cheaper - soot properties ?

model based calibration

engine experiments - hard to control & expensive + realistic

full-scale simulations

CLEERS Workshop 2010 April 21st, 2010 21 April 2010 CLEERS Workshop 2010 5

Methodology


small-scale experiments - controlable & cheaper + soot properties ?





Small-scale soot loading methodology


Soot oxidation measurements Small-scale DPF apparatus for synthetic gas bench

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test piece (+6 thermocouples)

synthetic gases

gas mixer furnace

H2O HC

by-pass line flow meter

exhaust line (can be connected to engine) AVL AMA i60 analyzer

(CO, CO2, HC, NO/NOx) + pressure & temperature sensors


Similar experiments were done at 380, 460, 470 and 540 °C.

NOx

NOx – O2 mixture

soot burn off in O2

heat up in N2



Reaction with O2 Activation energy

Two discrete regions are observed: there appears to be a necessity to use 2 reactions with O2 (one with higher and one with lower activation energy).



E ~ 100 kJ/mol R2 = 0.9594




Range: 550 – 650 °C E ~ 153 kJ/mol R2 = 0.9956

Range: 400 – 530 °C E ~ 67 kJ/mol R2 = 0.9752


E ~ 100 kJ/mol R2 = 0.9594


Cooperative reactions in mixture of NO2-O2 Are they necessary to explain our results?

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A set of independent reactions was used to describe soot oxidation with NO2 and O2.

Within experimental uncertainty, the sum of the reaction rates of the reactions with O2 and NO2 seems to be equal with the experimental reaction rate measured when both species are present.


Methodology







Modeling and rate expressions axitrap (3d + 1d DPF modeling)


Uncatalyzed soot oxidation reactions

Calibration targets of soot oxidation with O2 and NO2: - set of reactions (how many and which reactions?) - kinetic parameters (activation energies, pre-exponential factors)

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Characteristic simulation results Experiment at 460 °C

ENO2 = 45 kJ/mol, EO2,low = 64 kJ/mol, EO2,high = 155 kJ/mol


Characteristic simulation results Experiment at 380 °C

ENO2 = 45 kJ/mol, EO2,low = 64 kJ/mol, EO2,high = 155 kJ/mol


Methodology







•  Steady-state regeneration experiments at 3 temperatures (400 – 450 – 500 °C). •  The filter was weighed before and after each test. •  Target soot loading 7–9 g/L. •  A cDPF was used upstream in order to increase NO2 concentration and to avoid loading of the tested filter.

Engine test protocol for full-scale tests


Methodology







Model validation in full-scale system Experiment at 400 °C

Δm EXP: 1.5g Δm SIM: 1.6g

CLEERS Workshop 2010 April 21st, 2010 21 April 2010 Cleers 2010 23








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Conclusions

!   A novel experimental procedure was used to evaluate uncatalyzed soot oxidation kinetics with NO2 and O2.

!   The experimental results suggested that: •  soot oxidation with O2 and NO2 take place independently •  a low temperature direct reaction with O2 is necessary to

describe soot oxidation at CRT-relevant temperature range

!   With the help of model-based calibration, it was possible to obtain rate parameters, activation enrgies and reaction selectivities

!   The calibrated model was succesfully applied to full-scale engine operation under passive regeneration conditions.

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CLEERS Workshop 2010 April 21st, 2010 21 April 2010 CLEERS Workshop 2010 27

Future work

!   Further research is needed to optimize the experimental setup and protocols and to understand and validate:

–  effects of water, ammonia, … –  the transient soot oxidation effects: Can they be predicted with the

assumption of a more reactive part of soot? –  etc. (G.B. Shaw: “Science... never solves a problem without creating ten more.”)

Transient areas were commonly observed in the beginning of each step.


Thank you for your attention!

Matyáš Schejbal

[email protected]

http://lat.eng.auth.gr

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