Abstract
In the present study, three-dimensional (3D) computational fluid
dynamics simulations are performed to examine the process of sulfuric
acid (H2SO4) and water (H2O) condensation in a large two-stroke marine
diesel engine. A skeletal n-heptane chemical mechanism is coupled with a
sulfur (S) subset to simulate the combustion process as well as the
formation of sulfuric oxides (SOx) and H2SO4. The condensation process
is simulated using a fluid film model which is coupled with the
in-cylinder gas phase. Prior to the engine simulations, the fluid film
condensation model is validated using the experimental data of sulfuric
acid condensation rate in a laminar pipe flow. Next, the engine model is
validated against the experimental sulfur dioxide (SO2) to sulfur
trioxide (SO3) conversion obtained from the corresponding test engine.
Both of the validation studies show a good agreement with the
experimental data. The engine model is then utilized to simulate
condensation for different operating conditions. The engine simulation
results reveal that the fluid film has a significant effect on the total
mass of sulfuric acid vapor and a marginal effect on the total mass of
water vapor. A close to linear correlation is found between the fuel
sulfur content and the total condensed mass of sulfuric acid. The level
of humidity of the scavenging air does not affect the condensation of
sulfuric acid considerably, relative to the humidity increase, but it
has a high impact on water condensation. The study of the scavenging
pressure level reveals a counter intuitive behavior where the
condensation rates decrease with higher scavenging pressures due to the
flow regime and flame size. Next, increasing the cylinder liner
temperature decreases significantly the water condensation contrary to
the sulfuric acid condensation which is marginally affected. The
increase in lubricant film thickness results in a decrease for both the
sulfuric acid and water condensation with a more pronounced reduction
for water. Finally, a comparison between the high and low load operating
conditions reveals a small drop in the total condensed mass of sulfuric
acid and water for the low load conditions.
Original language | English |
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Journal | Applied Energy |
Volume | 211 |
Pages (from-to) | 1009-1020 |
ISSN | 0306-2619 |
DOIs | |
Publication status | Published - 2018 |