Investigating SO3 Formation from the Combustion of Heavy Fuel Oil in a Four-Stroke Medium-Speed Test Engine
2013
Cordtz, Rasmus | Schramm, Jesper | Rabe, Rom
The validation of detailed models, in terms of SO₃ formation in large marine engines operating on sulfur-containing heavy fuel oils (HFOs), relies on experimental work. The requisite is addressed in the present work, where SO₃ is measured in the exhaust gas of an 80 kW medium-speed single-cylinder HFO-fuelled test engine. SO₃ formation is triggered by running the engine at altered operational conditions and speeds within 1050–1500 rpm. The test engine does not represent a large low-speed marine engine; however, the nature of high-temperature SO₃ formation may well be explored with the current engine and serve as reference for further modeling studies. SO₃ is measured using a continuous SO₃ monitor from PENTOL GmbH. The monitor offers online SO₃ readings and short sampling times, in contrast to other extractive methods. The measurement is based on SO₃ capture in isopropanol prior to chemical conversion and indirect detection via light absorption in a photometer. Present results show that SO₃ formation is favored by elevated pressure histories, premixed combustion, and reduced speeds. The fraction of fuel sulfur converted to SO₃ is measured to be on the order of 0.5%–2.4%, corresponding to 4–14 ppmv. SO₃ and NOₓ are not comparable, according to thermodynamic considerations, yet both species involve the radical pool and are studied in parallel. Resulting emissions of SO₃ and NOₓ in the exhaust gas follow a comparable trend throughout the experiments.
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