cimac congress bergen 2010 s ox

CIMAC Congress Bergen 2010Paper no. 39

16.6.2010© MAN Diesel & Turbo < 1 >

Anders Andreasen & Stefan MayerBasic Research

Process Development R&D / Marine Low Speed

Modelling fuel sulfur oxidation in low speed two-stroke diesel engines

§ Background and motivation

§ Review of current models for S oxidation

§Model description and calculational setup

§ Results

Presentation outline

16.6.2010© MAN Diesel & Turbo

§ Proposed model simplifications

§ Summary & Outlook

< 2 >Modelling fuel sulfur oxidation in low speed two-stroke diesel engines

Objective:Provide a realistic, applicable model capturing the essential physics of SO2oxidation in large two-stroke diesel engines for in-house 0D to 3D computationalcodes. Obtain a better understanding of the main mechanisms involved in corrosionalwear of the cylinder liner

§ HFO average Sulfur content ~ 2.5 wt. % (4.5 % max.)

Background & motivation

Source: MEPC 57/4/24

16.6.2010© MAN Diesel & Turbo < 3 >Modelling fuel sulfur oxidation in low speed two-stroke diesel engines

§ Sulfur oxidised during combustion




Schramm et al. SAE paper, 940818§ Acidic species transported to cylinder liner

§ Acidic species cause (un)desirable corrosion

§ Corrosion controlled trough TBN of lube

§ Challenge: Low sulfur fuel & predicting scuffing



Lube base deposits may result

§ Acidic species transported to cylinder liner

§ Acidic species cause (un)desirable corrosion

§ Corrosion controlled trough TBN of lube

§ Challenge: Low sulfur fuel & predicting scuffing


Lube base deposits may result in bore polish and scuffing

Required knowledge§ Acidic species formed: How, when and how much?§ Transport mechanism of acidic species to lube oil film§ Lifetime and behaviour of acidic species in lube oil (Ostwald ripening?)

§ Lube oxidation behaviour (depleting neutralising agents)



Oxidation


Oil oxidation

Neutralization

Wetting corrosion

SO3/H2SO4 SO2/H2SO3 CO2/H2CO3

Neutralisation (wasteful)Base

Oil film surface

Cylinder liner

Lube

oil

film

After van Helden, CIMAC 1987

§ Frozen equilibrium approach§ A fixed user-defined conversion§ Detailed kinetic mechanism

Review of current models

Conversion, εεεε Ref.

Frozen eq. ~20% Teetz, VDI, No. 626/1984

Mod

el


Frozen eq. ~20% Teetz, VDI, No. 626/1984

Fixed conversion 3-5% (user defined) Schramm, SAE 940818van Helden, CIMAC 1987

2 stroke Diesel ~4-4.5 J. J. Valente, J. F. Pessoa Amorim, CEM, Macau, June 2006

4 stroke Diesel 2-8% Engel et al., J. Eng. Power, vol. 101 (1979) pp. 598

Boilers 0.2-7% Hunter et al. Contract no. ARB 4-421

Mod

elE

xper

imen

t

§ Sulfur oxidation mechanism from Glarborg et al. § H/O subset. 28 elementary reactions§ S subset. 97 elementary reactions§ Species thermodynamic parameters from NASA polynomials§ Cantera (http://code.google.com/p/cantera/) used to handle

calculation of thermodynamics and integration of kinetic rate equations

Model description


species(name = "SO3",atoms = " S:1 O:3 ",thermo = (

NASA( [ 1000.00, 5000.00], [ 7.075737600E+00, 3.176338700E-03, -1.353576000E-06, 2.563091200E-10, -1.793604400E-14,-5.021137600E+04, -1.118751760E+01] )

),note = "BUR0302 J 9/65“)

# Reaction 92reaction( "SO3 + O <=> SO2 + O2", [2.80000E+04, 2.57, 29200])# Reaction 88falloff_reaction( "SO2 + OH (+ M) <=> HOSO2 (+ M)",

kf = [5.70000E+12, -0.27, 0],kf0 = [1.70000E+27, -4.09, 0],falloff = Troe(A=0.1, T3=1e-30, T1=1e+30),efficiencies = " H2O:5 N2:1 SO2:5 ")

§ Detailed kinetic mechanism coupled to multi-zone approach§ Post-processing of measured cylinder pressure§ Differential fuel amount from calc. intgr. heat release (1 CAD)

Model description

ParcelAir@ λ =1 EVO∆Fuel

Hea

t rel

ease


Equilibrate (HP)

Mix air @ Mix air @ airmixm&

Integrate rate eq.Sulfur

NOx (Zeldovich)

For

eac

h C

AD

rep

eat

1 2

1

3

2

1

n

n-1

2

1

∆CAD=1º

SOIH

eat r

elea

se

CAD

§ Tuning the mixing rate parameter (75% load)§ Matching calculated NO with measured§ Finding corresponding mixing rate and ε

Results: Tuning


Measured NOx

Mix rate 3.29ε = 4.43

Results: Details @ 75 % load (MCR)

Main sulfur speciesconcentrations

NO concentration

SO2

SO3


Temperature

SO2 Conversion, ε

SO3

§ Range of ε§ Variation in fuel S content

Results: Summary and quasi-validation

Load (%) Epsilon (%)

100 2.59

75 4.43


50 4.25

25 6.72

Experiments on 4-stroke heavy duty diesel enginesSource: Engel et al., J. Eng. Power, vol. 101 (1979) pp. 598

§ Range ε =1.8-7.7 % (0.2-7% for boilers, Hunter et al. Contract no. ARB 4-421)§ Decreasing ε with increasing S content § Decreasing ε with increasing load (and decreasing exhaust oxygen conc.)

Good agreement with experiments!

§ CycSim: In-house C++ (Object Oriented) Cycle-simulator

§ Zone number reduced from ~50 to 1-2§ Computational effort reduced§ Model concept upgraded from post-processing to

prediction also

Results: applications to two-zone combustion in cyclic simulation


Slightly different, but general trends are preserved!

§ Current detailed model computational demanding§ Decrease calculation time by model reduction

Step 1: SO2 + OH (+M) = HOSO2 (+M)Step 2: HOSO2 + O2 = SO3 + HO2

Step 3: SO2 + O (+M) = SO3 (+M)Step 4: SO + OH = SO + H

Model simplifications


Step 4: SO2 + OH = SO3 + HStep 5: SO3 + H2O = H2SO4

< 15 >Modelling fuel sulfur oxidation in low speed two-stroke diesel enginesReaction flow analysis

97 rate equationsreduced to 5!No loss in predictions!

Conclusions§ Detailed model applied with success§ Qualitative agreement between calculations and experimental findings§ Model simplifications possible (reduction in steps, zone no.’s)

Future work

Summary & Outlook


§ Apply reduced model in CFD code for spatial investigations§ Couple results with mass transport model for lube oil film

Other remaining issues§ Rate of SO3 to H2SO4 from atmospheric chemistry§ Influence of Vanadium in fuel oil (catalytic)§ Influence of N-chemistry on SO2 oxidation§ Measurements of SO3/SO2 in exhaust from large two-stroke engines


Thank you for your attention. Questions?


cimac congress bergen 2010 s ox

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