Modeling the Distribution of Sulfur Compounds in a Large Two Stroke Diesel Engine

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• 作者：Rasmus Cordtz ; Jesper Schramm ; Anders Andreasen ; Svend S. Eskildsen ; Stefan Mayer
• 刊名：Energy & Fuels
• 出版年：2013
• 出版时间：March 21, 2013
• 年：2013
• 卷：27
• 期：3
• 页码：1652-1660
• 全文大小：504K
• 年卷期：v.27,no.3(March 21, 2013)
• ISSN：1520-5029

文摘

In many years large low speed marine diesel engines have consumed heavy fuel oils with sulfur contents in the order of 2.5鈥?.5 wt %. Present legislation requires that the fuel sulfur is reduced, and in the near future the limit will be 0.5 wt % globally. During combustion most of the sulfur is oxidized to SO₂ from which a fraction is further oxidized to SO₃. SO₃ may combine with H₂O and condense as liquid sulfuric acid that promotes corrosive wear on e.g. cylinder liners. To extend engine lifetime and reduce costs for lubrication it is pivotal to identify formation of SO₃ with respect to operational conditions and sulfur feed. This work presents a computational model of a large low speed two-stroke diesel engine where a 0D multizone approach including a detailed reaction mechanism is employed in order to investigate in cylinder formation of gaseous SO₃ where fuel burn rates are based on experimental pressure traces. In contrast to NO the SO₃ does not really form at the highest combustion temperatures, but like NO the formation of SO₃ is very sensitive to the rate that fresh air mixes with hot combustion products. Consequently a simple mixing rate is proposed and calibrated in order to meet experimental results of NO. For a large low speed diesel engine the model shows that 3鈥?% of the injected sulfur is oxidized to SO₃ that is formed primarily in the temperature range from 2000 to 1300 K during cylinder expansion. In addition the model is used to reduce the full reaction mechanism from 96 to 7 elementary sulfur reactions without compromising the SO₃ to SO₂ ratio.