chemical kinetics of combustion - bienvenue · insis, 8 mars 2016 1 . chemical kinetics of...

INSIS, 8 Mars 2016 1 .

Chemical Kinetics of Combustion

Philippe Dagaut

CNRS-INSIS

ICARE – 1c, Avenue de la Recherche Scientifique - Orléans- France

● Introduction ● Experimental facilities for modeling validation ● Kinetic Modeling ● Some results ● Conclusions


INTRODUCTION

Ubiquitous combustion


Introduction (cont'd)

RESSOURCES

2010 Projections

98% transport fuels are oil-derived


Introduction (cont'd) PM10 (<10 microns)



GHG: CO2

http://www.worldclimatereport.com



TO ADDRESS THESE ISSUES/CHALLENGES:

ALTERNATIVE FUELS

NEW ENGINE TECHNOLOGIES

SCIENCE


Introduction (cont'd) Chemical Kinetics (combustion/troposphere)

HC,NOx,COx

HC,NOx,COx

HC,NOx,COx

R+O2 RO2RO2+NO RO+NO2HO2+NO OH+NO2

RH+OH R+H2O

2RO2 2RO+O2, ...

RO2+HO2 RO2H+O2, ...

NO2+h NO+O; O+O2+M O3


Introduction (cont'd) Chemical Kinetics

Experimental data ↔ Model Constrain the model(s) by using Global parameters: Ignition delays (initiation reactions, R+O2) Burning velocities (H fluxes) Detailed information: Species concentrations (~ all processes) Initiations: RH R + H RH R’ + R” RH + O2 R + HO2 Propagations: RH + X R + HX (X= H, O, OH, HO2, CH3, HCO …) Terminations: R + H RH R’ + R” RH Different types of ‘reactors’: ST, PF, PSR, Flames (laminar premixed, opposed flow)


Introduction (cont'd) Alternative fuels

In recent years, research activities on synthetic and bio-derived fuels have increased

significantly in order to reduce dependence of the air transport sector on petroleum.

fossil

renewable

{

{

*XTL: Gas/Coal/Waste/Renewable to Liquid

INSIS, 8 Mars 2016 10 .


2-G Biofuels

Source

(# 3G biofuels) Potential use Current knowledge Interest

Alcohols

OH

lignocellulose Aviation?,

Automotives Kinetic data & model for simple alcohols; can be extended to

larger alcohols High

Methyl esters

O

O

O

Algae#, lignocellulose Automotives

Kinetic data & model for simple esters; extended to larger ones; little information for unsaturated

esters

High

Ethyl esters

O

O

O

Algae#, lignocellulose Automotives Very little information

e.g. ethylpropionate High

Furanics

O

O O

Lignocellulose (Fructose, glucose)

Automotives Essentially test in engines, + W-I-P (?)

Polymers of terpenes & isoprenoids (farnesane)

Trees & plants (α-, β-pinene)

Aviation, Automotives

Essentially test in engines, Su + W-I-P High

2G-CSafe 2011-2016

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EXPERIMENTAL FACILITIES for modeling validation

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Experimental Facilities

Variable pressure

JSR 1-40 atm Sooting flames Pool fire

Smoke point apparatus

DCN apparatus I.C. Engines

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Experimental Facilities What we can learn

Conc. profiles,

Pathways, pollutantsSoot, PAHs, kinetics of atmos. soot rxns

Soot, PAHs

Smoke point Cetane Number

(ignition) Soot, PAHs,

HCCI kinetics, sensitization, control

INSIS, 8 Mars 2016 14 .

Experimental Set-Up

Stables species measurements H2, O2, H2O, CO, CO2, CH2O, CH4, C2-C16,

NOx, SOx

●Low-P samples taken by sonic probe

sampling for GC analyses (Capillary

columns Carboplot, DB-624, CP-Al2O3-KCl;

TCD, FID, MS).

●On-line FTIR, GC analyses (FID/MS)

●C-balance checked for every sample

FID

TCD

O2+N2Fuel (+NOx) +N2

Heating Wire

Probe+TC

GC

Exhaust

GC/MS/FID

Bulb

Piston

LO

PA

P

FT

IR

HPLCUV-Fluo

PA

H-T

rap

Sample

GC/MS

INSIS, 8 Mars 2016 15 .

Experimental Set-Up

Less-stable or unstable species measurements

(H2O2, HO2)

O2+N2Fuel+N2

PhotodiodePiezo Mod

Mirror

Signal:

cwlaser

AOM

Pump

ring downcavity

Mirror

TC &Probe

JSR set-up with sonic sampling and cw-CRDS quantification of H2O, H2O2, HO2, CH2O, C2H4

J. Am. Chem. Soc. 136 (47), 16689–16694 (2014); Fuel 158 (1) 248–252 (2015).

INSIS, 8 Mars 2016 16 .

Experimental Set-Up

BL 9.02

JSR/MBMS TOF

The Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory, CA. JSR team: Combustion Research Facility, Sandia National Laboratories, Livermore, CA; Dept of Chemistry, Bielefeld University, Germany; CNRS-INSIS, Orleans, France; King Abdullah University of Science and Technology, Thuwal, Saudi Arabia; Dept of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ.

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KINETIC MODELING

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Modeling

Need accurate kinetics, thermochemistry, and transport data

Use inputs from theory and measurements and also estimations by analogy

Need accurate data that are used to constrain the model

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Modeling: Hierarchical structure of chemical kinetic schemes

H2-O2 CO2 CH3OH

CH4CO CH2O

C2H6

C2H4

C2H2

C3 >C4

INSIS, 8 Mars 2016 20 .

Modeling: hydrocarbons oxidation Cool flame High-T

INSIS, 8 Mars 2016 21 .

Modeling RH

R

RO2

QOOH

OOQOOH

OQ’OOH + OH

OQ’O + OH

Olefin + HO2

+X

RO + RO + O2

Olefin + Carbonyl

+ OH

O2Cyclic Ether + OH

Compound

RO2

O2

HOOQ’OOH

O2

Decomposition

HO2

RHROOH

RO+OH O2

R’ + OlefinH + Olefin

-XH

INSIS, 8 Mars 2016 22 .

Modeling New reactions evidenced through JSR/ALS experiments: HOMs formation

Extended reaction scheme of OOQOOH radical. The pathways included in 2-Methylhexane kinetic model are annotated with dashed arrows; the extended third O2 addition pathways studied in this work are annotated with blue solid lines. 36th Symp. Int’l on Combustion, submitted (2016)

INSIS, 8 Mars 2016 23 .

Results: HCCI control via Sensitization by Ozone, NO, and NO2 Production of ozone/discharge

-20 -10 0 10 20

20

30

40

50

60

70

80

In-C

ylin

der P

ress

ure

[ba

r]Without O3,NO and NO2

[NO2] = 19.7 ppm

[NO] = 19.9 ppm

[O3] = 19.6 ppm

-30 -20 -10 0 10 20 300

20

40

60

80

Crank Angle Degree [CAD]

Hea

t Rel

ease

Rat

e [

J/CA

D]

Without O3,NO and NO2

[NO] = 19.9 ppm

[NO2] = 19.7 ppm

[O3] = 19.6 ppm

In-cylinder pressure and heat release rate traces without any species and with 20 ppm of each species separately injected. Mazurier et al. Proc. Combust. Inst. 35 (3) 3125–3132 (2015).

INSIS, 8 Mars 2016 24 .

Results: HCCI control via Sensitization by Ozone, NO, and NO2

Simple computations to understand the process ● Ozone mainly decomposes into oxygen molecules (O2) and O-atoms, FAST. Then, the fuel reacts directly with O-atoms to yield OH radicals and rapid oxidation of the fuel ensues: C8H18+O→C8H17+OH (a) followed by

C8H18+OH→C8H17+H2O (b).

● NO is mostly consumed by reaction with HO2, resulting in the initial oxidation of the fuel via C8H18+O2→C8H17+HO2, SLOW, OH radicals are produced via NO+HO2→NO2+OH, FAST. Subsequently, rapid fuel consumption can take place via (b) due to OHproduction. Consequently, as nitric oxide requires an HO2 radical to yield an OH radical, this explains the lower effect of NO on ignition delays compared to ozone.

● NO2 addition: OH production results from a longer sequence of rxns: CH3+NO2→CH3O+NO; NO2+HO2→HONO+O2; HONO+M→NO+OH+M; and NO+HO2→NO2+OH. Because nitrogen dioxide presents intermediate reactions before OH production, its effect on ignition delays is the lowest of the three additives considered.

INSIS, 8 Mars 2016 25 .

Conclusions & Perspectives ● Detailed chemical kinetic models need laboratory experiments (simple to

sophisticated) + kinetics & thermo data for validation prior to use in CFD modeling (HCCI,

GT, …)

● Due to the hierarchical structure of kinetic reaction mechanisms, simple to complex

chemical systems need to be studied and sub-models validated

● For modeling the combustion of complex fuels: appropriate surrogates are also needed

● HCCI (Homogeneous Charge Compression Ignition) is interesting for fuel savings, but the

auto-ignition event is difficult to control: chemical kinetics can help via

Engine experiments combined with modeling including detailed chemistry

chemical kinetics of combustion - bienvenue · insis, 8 mars 2016 1 . chemical kinetics of...

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