ignition and combustion of diesel sprays · influence of multicomponent fuel composition on...

Influence of multicomponent fuel composition on

ignition and combustion of diesel sprays4th Two-day Meeting on Internal Combustion Engine Simulations Using OpenFOAM® Technology

Martin BlumePhilip SchwarzRomuald Skoda

Sandro Gierth Magnus KircherFederica Ferraro Martin PollackChristian Hasse

Lukas Weiß Michael Wensing

Alessandro StagniTiziano Faravelli

Techn. University Darmstadt

Ruhr University Bochum

FAU Erlangen-Nürnberg

Politecnico di Milano

2

Motivation

3D mixture formationand combustion

3D spray simulation3D gas

exchange

Fuel sideGas side

1D gas exchange

3D nozzle flowsimulation

1D hydraulicssimulation

System simulation(MBS, electr., magnet.)Image source: Bosch

The entire diesel process Zoom into diesel spray cause effect chain

Multicomponent fuel is the standard in diesel engine operation

Source: [1]

[1] https://images.app.goo.gl/NSaXBLGtgLtTLs828

3

Motivation and Outline

Diesel fuel:

Mixture of hundreds of

hydrocarbons

Exact composition neither known

nor standardized

Single species’ interactions

rather complex to investigate in

such multicomponent mixtures

Aim:Investigation of multicomponent

mixture influence along diesel

engine cause and effect chain

Based on simplified surrogate fuel:

10 mass-% n-dodecane/

90 mass-% n-heptane

Based on application relevant

configuration (spray chamber,

near to application heavy-duty

injector)

Source: [1]


4


Motivation

Experimental setup

Modeling Approach

Results and Discussion

Summary andOutlook

Source: [1]


5


Motivation

Experimental setup

Modeling Approach


Summary andOutlook

Source: [1]


6

Experimental setup and techniques

Experimental setup:

High pressure combustion chamber

Heavy-duty 9-hole injector, 4 holes closed

Fuels

n-dodecane

n-dodecane / n-heptane mixture (10 / 90 mass-%)

Chamber temperature: 600 °C

Chamber pressure: 50 bar

Rail pressure: 1000 bar

Fuel temperature: 90°C

Experimental techniques:

Inert environment (N2):

!LIF (primary break-up)

Mie (liquid penetration)

Schlieren (vapor penetration)

Reactive environment (air):

OH* luminosity

(Visual flame signal)

Spray

closed

closed

closed

closed

7


Motivation

Experimental setup

Modeling Approach


Summary andOutlook

Source: [1]


8

Numerical approach for spray modeling

Particle in cell method (PIC) / Euler – Lagrange Approach

Statistical descriptionFollows evolution of parcels

Each parcel represents collection of identical droplets

CFD-Cellà gas phase

Parcelà liquid phase

model

~up~ug

Source of Schlieren image: [1]

[1] L. Weiss, A. Peter, M. Wensing, „Diesel Spray characterization with Schlieren-Mie Technique“, Lisbon Symposia, Lisbon 2016

Suitable approach for parcel (spray) initialization needed.

stoichiometric mixture fraction

f (d, u, r, ✓)

Exemplary simulation result

9

Inner nozzle flow and primary break-up

3-Phase solver has been developed [1] and implemented in FoamExtend branchLiquid and vapor fuel, non-condensable gas360° model of injector with directly coupled spray domainfor one selected nozzle hole

Agreement between simulation and experimental data in range of the

cyclic fluctuations

12 % 15 % 19 % 100 %.

Exp. SI

!LIF data from highpressure injection chamber

" = 600 °C,# = 50 bar$-Dodecane

Exp. EA

Simulation

Q-Stat.

[1]: Blume et al., submitted to Atomization&Sprays[2]: L. Weiß, M. Wensing, FAU Erlangen-Nürnberg, 2018

Opening phaseExperimental !LIF data [2]Single shot (SI)Ensemble average (EA)Sim.: Iso-Surf. of liquid volume fraction

10

In-nozzle flow / Spray interface

f(d, u, r, ✓) ⇡ f(d) · f(u|d) · f(r|d) · f(✓|d, r)<latexit sha1_base64="TSNiega9o0pTI1rQIsMIzbvqmIw=">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</latexit><latexit sha1_base64="TSNiega9o0pTI1rQIsMIzbvqmIw=">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</latexit><latexit sha1_base64="TSNiega9o0pTI1rQIsMIzbvqmIw=">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</latexit><latexit sha1_base64="TSNiega9o0pTI1rQIsMIzbvqmIw=">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</latexit>

6 mm

Joint PDF

Lagrange spray initialization by PDF of ligament location, velocity and diameter

Euler VoFSimulation

Coupled Euler-Lagrange Simulation

Spray asymmetry due to injector characteristics captured by simulation interface (joint PDF)

11

Evaporation model

) dTd

dt=Qs � mFL

mdcp,l

) Ql = Qs � mFL

Evaporation rate with

convective fluxes:

Droplet temperature

d

dr

✓r2⇢guY v

i � ⇢gDgi r

2 dYvi

dr

◆= 0

Nu = 2 + 0,6Re1/2Pr1/3

Particle in cell method (PIC) / Euler – Lagrange Approach

Liquid phase: Governing equation for each parcel

in Lagrangian manner

Gas film transport equation (!... fuel and environment species):

mf,i = 2⇡rd�g

cp,gNuln (1 +Bm,i)

Bm,i =Y sf,i � Y 1

f,i

1� Y sf,i

Raoult's law for vapor-liquid

equilibrium at interface:

Xsf,i = X l

f,ipvap,ip

n-heptane evaporating

faster than n-dodecane

12

Combustion model – Flamelet concept

[1] Popp, STFS, 2015[2] N. Peters. Symp. (Int.) Combust. 21 (1988)

[1]

Theoretical basis of the flamelet concept:§ combustion chemistry is fast§ thin flame sheet assumption§ gradient alignment at flame sheet§ important physics along flame-normal direction

fuel

oxidizer

non-premixed flamelet: Definition:

fuel

oxidizer

non-premixed flamelet:

flameletfuel

oxidizer

non-premixed flamelet:<latexit sha1_base64="6KiGWX1lNMmnvN9D5nhwZFj7Cw8=">AAAH6HicpVXNbtNAEJ62QNrw18KRi0WEhABVThs1vSAVUSouQFFpWtG0ke1sUlP/yXZKg5V34IbgyJNwhTfgXTjwzXgTGtomQdiyd3Z25vvGM7tjO/LcJDXNn1PTM5cuXynMzhWvXrt+4+b8wq1aEnZiR207oRfGu7aVKM8N1Hbqpp7ajWJl+banduyjp7y+c6zixA2DN2k3Uvu+1Q7clutYKVSN+cpb47FRb8WWk/mNuh/7WaujvF5vaGY8NPQ0PHGbvV5jvmQumlWzslwxIKwum6YJYaVqVssrRnnRlKtE+toMF2ZeUp2aFJJDHfJJUUApZI8sSnDvUZlMiqDbpwy6GJIr64p6VIRvB1YKFha0R3i3MdvT2gBzxkzE2wGLhyeGp0H38GwIog1rZlWQE4y/8HwQXftChkyQOcIuRhuIc4L4AvqUDmHBngHG98Lr47Ywb0J7qGcnQDH1V5xvaZ9jOSoaX7M/Es/+V27Bgr+I82EMbJSWXPg5Mo8lI5wfzpkH61H5TalFq5JXF5aRaJjBGfCuYyWG7khWDHomlm1g2DI/BhdHtA0+rncfwZDcNzHmeVCCEmhEC3gxRo6c4ylKlOuwyHcN227pqnC9N4Qllfr7g3rxSoJIM3qFmm2J1F9n2Zd3oHOeZ/BfUHO5OYLBHmIYH/8TyBHqlGePmeuDWjoYvSGG09EUL9xhDwRDyYxP2r6ghqgM59yTevHuKmGtN2Kn5jg2dsQflH5srJ0UgXfeWQTWjkfIpI9wxvdoSSM0ZXdHkteunO2udI46YoplR7NVNOgrnEVDM52/sjRRDClWwv+O5ADeo6LJdDwHY6Li3NZ0RvNq1Cawd894NKAb7ZVqHo7Rk5M7CVc6YPvbbzwjZzKWDp/o7pFIB8t098xRubf0Bn3ptI8x5GUMnR2cG/zP+j8t42KhtrRYhvy6Uloz9Z9tlu7QXbqP2lVpjZ7TJrqcQ1/oG32nH4V3hY+FT4XPuen0lPa5TUNX4etvIteYwQ==</latexit>

Turbulent flames ≈ Ensembles of 1D flamelets

<latexit sha1_base64="cKWMFAAeXB1XleR7UaZd+9Rsw+s=">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</latexit>

[2]

13

!(#) obtained from canonical setups, e.g. counterflow diffusion flame

As diffusion coefficient, ! acts as inverse residence time for fluid packages in mixture fraction space à determines ignition delay time

Combustion model – Flamelet concept spray


[1]

�(Z) = �stexp(2[erfc�1

(2Zst)]2 � 2[erfc

�1(2Z)]

2)

Zst

constant for each flamelet simulation

�st

Zst

!T

@T

@t

⇠ �decreasing residence tim

e

increasing ignition delay time

⌧hom

no ignition

⇢@Yi

@t� 1

2⇢�

@2Yi

@Z2= !i

⇢@T

@t� 1

2⇢�

@2T

@Z2= !T

�st > �st,q

fuel

stagnationplane

x

r

flame

oxidizer

[1 N. Peters. Symp. (Int.) Combust. 21 (1988)

14

In diesel sprays, !"# is varying after start of injection and not known a-priori (function of nozzle and injection parameters)

Tabulation of flame structures based on constant !"# simulations chosen here to capture main effects of the combined ignition and mixing processes with manageable effort

Combustion model – Flamelet concept spray

Source: [1]

Progress of ignition à Progress variable $%

t = 2ms

t

Impact of scalar dissipation rate !"#

�st,1

�st,2

�st,1 > �st,2

�st = 20 1/s

[1]: Pickett, L. M., Genzale, C. L., Manin, J., Malbec, L. M. & Hermant, L. 2011 Measurement uncertainty of liquid penetration in evaporating Diesel sprays. In Proceedings of the23rd Annual Conference on Liquid Atomization and Spray Systems


[1]

15

Combustion model – Flamelet concept bi-component spray

Parametrization of fuel composition for 2 components:

In more appropriate formulation:

fuel

stagnationplane

x

r

flame

oxidizer

ZC12H26 =mg,ox,Cl2H26

mg +mg,Cl2H26 +mg,C7H16= Z1

ZC7H16 =mg,C7H16

mg +mg,Cl2H26 +mg,C7H16= Z2

y =Z2

Z1 + Z2

Z = Z1 + Z2 Location in Z-space

Composition of fuel

Ignition delay time increasing with n-heptane content

y =Z2

Z1 + Z2

0.0 0.2 0.4 0.6 0.8 1.0

t ignin

ms

0.4

0.5

0.6

0.7

Ignition delay obtained by flamelet simulation

16

Combustion model – Resulting tabulation approach

1D Flamelet Database CFDtabulation

+ 2D !-pdf integration coupling

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Full Thermochemical State Reduced-order Model Solve control variables instead of


[1] N. Peters. Symp. (Int.) Combust. 21 (1988)

[1]

fuel

stagnationplane

x

r

flame

oxidizer

e

Z = Z1 + Z2

y =Z2

Z1 + Z2Fuel composition

Thermo-chemical state

eZ1, eZ2, eYC

�st = 01/sgZ 002i = 0

eZ

e!YCey

e = e ⇣ey, eZ, gZ 002

sum,n, e�st, eY norm

C

⌘

17

Combustion model – Chemical mechanism

Tabulated chemistry enables incorporation of complex chemical mechanism in 3D-CFDBut: Amount of flamelet simulations makes utilization of reduced mechanism advantageousReduction approach:

Optimization target: Homogeneous ignition delay timeA-posteriori evaluation based on laminar flame speed and diffusion flames relevant for current spray flame tabulation

POLIMI C0-C16 mechanism (Low/High Temperature)

~ 500 species ~ 17000 reactions

POLIMI TPRF mechanism (Low/High Temperature)

~ 335 species ~ 9315 reactions

C12-C7 reduced mechanism (Low/High Temperature)

~ 127 species~ 2205 reactions

Source: [4]

Preselection based on heaviest fuel components

Reduction procedure utilizingDRGEP + SA [1,2,3]

[1]: Pepiot-Desjardins, P., & Pitsch, H. (2008). An efficient error-propagation-based reduction method for large chemical kinetic mechanisms. Combustion and Flame, 154(1-2), 67-81., [2]: Niemeyer, K. E., Sung, C. J., & Raju, M. P. (2010). Skeletal mechanism generation for surrogate fuels using directed relation graph with error propagation and sensitivity analysis. Combustion and flame, 157(9), 1760-1770.[3]: Stagni, A., Frassoldati, A., Cuoci, A., Faravelli, T., & Ranzi, E. (2016). Skeletal mechanism reduction through species-targeted sensitivity analysis. Combustion and Flame, 163, 382-393.[4]: http://creckmodeling.chem.polimi.it/menu-kinetics

Reduction(DRGEP + SA)

18


Motivation

Experimental setup

Modeling Approach


Summary andOutlook

Source: [1]


19

Investigation mixing field in non-reactive environment

Comparison of evaporation behavior and mixture formation based on 1% fuel mass fraction:

Differences in start of fuel vapor formation with similar vapor penetration length

n-Dodecane Mixture

Initial fuel vapor earlier for mixture than for pure n-dodecaneVapor penetrations similar for both fuels

20

Validation of vapor and liquid penetration lengths

Comparison vapor and liquid penetration in non-reacting environment

Exp. Mie probability, Mixture, tASOI = 1.0 ms

Vapor penetration slightly overpredicted,no fuel influence in simulation

Steady liquid penetration in agreement with exp. data, fuel influence captured

Sim. Z=0.001, Mixture, tASOI = 0.7 ms Exp. Schlieren probability,

Mixture, tASOI = 0.7 ms

Sim. liquid mass < 99 %, Mixture, tASOI = 1.0 ms

21

Investigation gaseous fuel composition in non-reactive environment

Comparison of liquid and gas phase composition:

High fraction of n-heptane in liquid and vaporized fuel, decreasing with distance to injector

Downstream reduction of n-heptane fraction in

Liquid phaseGas phase

22

Comparison ignition and combustion process

Simulation results for ignition and combustion behavior

Qualitative experimental findings concerning ignition process reproduced,

n-heptane content in gas phase increases ignition delay time

n-Dodecane Mixture

Combustion starts at spray flank

and proceeds towards spray tip

Ignition delay time smaller for

pure n-dodecane than for mixture

Exp. line of side integrated OH*

n-Dodecane, tASOI = 0.70 ms

Exp. line of side integrated OH*

Mixture, tASOI = 1.05 ms

23

Comparison of ignition delay times based on cumulated OH* signal (exp.) / OH mass fraction (sim.)

Comparison integrated OH* and OH signal

Differences in ignition delay time captured by tabulation strategy

Ignition delay time slightly underpredicted by simulation for both, pure n-dodecane and mixtureBut: Difference in ignition delay time of n-dodecane and mixture well reproduced

Δ"#$%&'(

Δ"#$%)#*

24


Motivation

Experimental setup

Modeling Approach


Summary andOutlook

Source: [1]


25

Summary and Outlook

Aim:Investigation of multicomponent mixture influence along diesel engine cause and effect chainBased on simplified surrogate mixture: 10 mass-% n-dodecane/ 90 mass-% n-heptaneBased on application relevant configuration (spray chamber, near to application heavy-duty injector)

Findings:Liquid penetration for mixture shorter than for pure n-dodecaneInitial fuel vapor first formed by mixture Simulated vapor penetration unaffected by fuel composition due to same injection pressure / similar momentum fluxIgnition delay time for surrogate larger than for n-dodecane due to n-heptane content in gas phase

Outlook:LES of setup to investigate influence of gas phase mixing model

y =Z2

Z1 + Z2

0.0 0.2 0.4 0.6 0.8 1.0

t ignin

ms

0.4

0.5

0.6

0.7

26

The joint research project LowEmissionDesign is

funded by the German Ministry of Energy and

Economics (BMWi) in the framework of the

Verkehrsforschungsprogramm (“Gefördert vom

Bundesministerium für Wirtschaft und Energie

aufgrund eines Beschlusses des Deutschen

Bundestages.”). We would like to express our

gratitude to the project partners AVL Deutschland

GmbH, Robert Bosch GmbH and MAN Truck & Bus

SE

Calculations for this research were conducted on the

Lichtenberg high performance computer of the TU

Darmstadt within the computing project 973

and

with computing resources granted by RWTH Aachen

University within the computing project bund0002.

Acknowledge

ignition and combustion of diesel sprays · influence of multicomponent fuel composition on...

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