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1. Real experimental evidence of the conversion fraction in large two-stroke diesel engines is severely lacking. In order to improve the confidence in the
model the conversion fraction must be measured and compared with model predictions. 2. In this study we have relied on the kinetic parameters for conversion of SO3 to H2SO4 as reported by Reiner and Arnold [31]. Several other studies exists e.g. [42, 43, 44, 45] signalling both the complexity of the reaction as well as its importance in relation to acid rain.Unfortunately the studies are limited to low pressure and close to ambient temperature. Thus reliable kinetic parameters at elevated temperature and pressure are needed.
3. Until now only the time until exhaust valve opening has been considered. It should also be investigated further what happens after the exhaust valve opens (decrease in temperature and pressure), during the scavenging process and in the exhaust receiver. It should be expected that significantly more SO3 is converted to H2SO4 during these processes.
4. It is well known that vanadium oxide catalyse the oxidation of SO2 to SO3 [46, 47]. Since the fuel used for large twostroke engines may contain significant levels of vanadium, the catalysed oxidation may contribute significantly to the overall conversion fraction. Future
analysis should take this possibility into account.
NOMENCLATURE
cp Specific heat capacity at constant
pressure, J/(mol K)
Crad Heat radiation constant, J/(mol K4)
Conversion fraction of S to SO3 and
H2SO4
ΔH298 Standard formation enthalpy at 298 K
λ Air excess ratio
MCR Maximum continous rating
MEP Mean effective pressure, bar
Tad Adiabatic flame temperature, K
Trad Temperature drop due to radiation
w/w Weight fraction
ACKNOWLEDGEMENTS
We would like to thank our colleagues Mrs.Charlotte B. Røjgaard, Mr. Kjeld Aabo, Mr.Michael F. Pedersen, and Mr. Svend Eskildsen for invaluable discussions during the making of this manuscript. Further we would like to express our deepest gratitude to Prof. Peter Glarborg, Department of Chemical and Biochemical Engineering, CHEC Research Centre, Technical University of Denmark, for many enlightening discussions and, in particular, for commenting on the manuscript.
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