Overview Experimental Data Analysis and Modeling

Ignition Quality Tester (IQT™)

ObjectiveDevelop a pathway to use easily measured ignition properties as metrics for characterizing fuels in advanced combustion engine research - Correlate IQT™ measured

parameters with engine data

The information contained in this poster is subject to a government license; NREL/PO-540-40427; 2006 Diesel Engine-Efficiency and Emissions Research (DEER) Conference, Detroit, MI, August 20-24, 2006.

In HCCI engines, ignition timing depends on the reaction rates throughout compression stroke- Need to understand

sensitivity to T, P, and [O2]- Need to rank fuels based on

more than one set of conditions- Need to understand how fuel

composition (molecular species) affect ignition properties

3.5

3.0

2.5

2.0

1.5

1.0

0.51.1 1.2 1.3 1.4 1.5

In(I

gnit

ion

Del

ay [m

s])

1000/T

T = 550ºC

T = 405ºC

DCN = 42DCN = 46DCN = 53DCN = 58DCN = 81DCN = 100

CARB DieselHeptaneDiesel w/EHNCetaneDPGME (oxy)TPGME (oxy)

1200

1000

800

600

400

200

00 5 10 15 20

16

12

8

4

0

Pres

sure

(psi

)

Time (ms)

Nee

dle

Lift

(mm

)

Injector NeedlePressure Trace

Ignition Delay

Constant volume spray combustion chamber - Requires ~50 mL fuel

Ignition delay can be measured over a range of conditions: - T ~ 300 – 580°C - P ~ 5 – 30 bar - [O2]: Up to 21% or beyond

• Can measure derived cetane number (DCN) at specified conditions

3.5

3.0

2.5

2.0

1.5

1.0

0.51.1 1.2 1.3 1.4 1.5

In(I

gnit

ion

Del

ay [m

s])

1000/T(K)

T = 575ºC

T = 405ºCPRF 30

PRF 50

PRF 100Cetane - HMNCetane - MN

3.5

3.0

2.5

2.0

1.5

1.0

0.51.1 1.2 1.3 1.4 1.5

In(I

gnit

ion

Del

ay [m

s])

1000/T

T = 575ºC

Soy BiodieselMethyl LinoleateMethyl DecanoateCARB Diesel

PRF 30

PRF 50PRF 100

3

2.5

2

1.5

11.2 1.25 1.3 1.35 1.4

25

20

15

10

5

00 5 10 15 20 25

In(D

elay

[ms]

)

1000/T (K)

Mod

el D

elay

(ms)

Experimental Delay (ms)

18% Oxygen (14% EGR)

y = 0.9918xR2 = 0.9888

10 bar20 bar30 bar

5

4

3

2

1

01.2 1.25 1.3 1.35 1.4

In(D

elay

[ms]

)1000/T

0.50.60.70.80.9

1Data

P = 21 bar

Some oxygenates have a lower activation energy than normal hydrocarbons - Higher effective cetane

number at reduced temperature • Cold-start implications • Impact on HCCI ignition

Molecules with weakest C-H bonds have the lowest activation energy - Tertiary < Secondary < Primary - Adjacent to ether or carbonyl

weaken C-H bonds

Branching in hydrocarbons decreases activation energy - Tertiary C-H bonds

Aromatic compounds increase activation energy - Resonance stabilization

Biodiesel fuels have a higher activation energy for ignition - Unsaturated bonds result in

resonance-stabilized radicals

Mixing Factor Calculations Assumes fuel “perfectly” mixes with fraction of air in IQT - Ignores spray and mixing time - Accounts for temperature drop due to evaporation

Data shows how mixing increases with ignition delay - Lower mixing factor as pressure increases for fixed delay

Integrated CFD Model of IQT™ Spray: simplified cone model

Evaporation and mixing

Detailed chemistry w/ CHEMKIN - three mechanisms tested

Ignition delays are too fast!

Rate = A exp ( -Ea

RT ) [O2]b

Heptane: Ea = 50.2 kJ/mol, b = 0.74

Developed set of 27 points - T = 450, 500, 550 °C - P = 10, 20, 30 bar - [O2] = 15, 18, 21%

Fit empirical rate model - To deconvolute [O2]

and T effects

R• + O2 ⇔ RO2•

1000

800

600

400

200-180 -130 -80 -30

60

50

40

30

20

10

0

Tem

pera

ture

(K)

Crank Angle Degree

Pres

sure

(bar

)

PressureTemperature

CIDIHCCI

Fuel Sensitivity Parameters

DPGME

Tertiary C-Hadj. to -O-

Secondary C-Hadj. to -O-

TPGME

TEGME

2-Heptanone Methyl Caproate

1-HeptanolHME

OH

OH

HO

O

O

O

O O

O

O

O

O

OO

O

OH

Incr

easi

ng A

ctiv

atio

n En

ergy

Fuel Effects on Ignition and Their Impact on Advanced Combustion EnginesJoshua Taylor • National Renewable Energy Laboratory

Hailin Li and W. Stuart Neill • National Research Council Canada