Sequential turbocharging system evaluation for medium speed diesel engine

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Volume Title
School of Engineering | Master's thesis
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Date
2013
Major/Subject
Koneensuunnitteluoppi
Mcode
Kon-41
Degree programme
Language
en
Pages
(11) + 113 s. + liitt. 10
Series
Abstract
The main goal of this thesis was to evaluate various sequential turbocharging (STC) systems for a Wärtsilä 6120 auxiliary engine, with the main intent to increase the load acceptance of the engine. To reach this goal, a parallel, a series, a two-stage parallel and a two-stage series STC system were specified and simulated on the engine in the simulation software GT-Suite. Also, a layout study was conducted with parallel STC applied to the 6L20 engine in the CAD software I-Deas. The simulations were done by modifying the turbocharging system of simulation models of both a one-and a two-stage turbocharged engine into the sequential versions. The steady state simulations show that all STC versions of the engine have a higher fuel consumption compared with the equivalent one-or two-stage turbocharged reference engines. The high fuel consumption is mostly caused by a higher exhaust back pressure. Transient simulations were done on all but the series STC model. The load acceptance was simulated in load steps, where fun load was reached by instant loading from idle in two or three steps. In the lower load steps the engine speed recovered faster and the speed drop was smaller in all simulated STC versions of the engine, mainly due to a higher charge air pressure. All three simulated STC versions fulfilled the International Association of Classification Societies (IACS) requirements for loading in two steps. The layout study shows that it is possible to apply parallel STC to the Wärtsilä 6L20 engine with only a minor increase in engine size. Of thirteen layouts proposed, two layouts were chosen as candidates for a parallel STC version of the engine. STC is a viable alternative for an improved load acceptance in a medium speed diesel engine running at constant speed. However, the higher charge air pressure at lower loads alone does not increase engine efficiency. To improve the engine efficiency other changes to the engine besides the turbo charging system are needed.
Description
Supervisor
Kuosmanen, Petri
Thesis advisor
Raikio, Tero
Keywords
sequential turbocharging, sekvenssiahtaus, sekventiell turboladdning, parallel, rinnakkaissarja, parallell, series, dieselmoottori, serie, diesel engine, vakiokierroksinen, dieselmotor, constant speed, kuormanottokyky, konstant varvtal, load acceptance, simulointi, lastupptagning, simulation, simulering, layout
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