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Numerical Analysis of Gas Exchange system requirements in Heavy Duty DISI process with Alternative fuels
KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
2016 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Commercial vehicles using diesel engines have high fuel efficiency but have a significant cost impact due to expensive aftertreatment system and increased running costs. Spark ignition engines have the advantage of using a simple three-way catalyst making cost of ownership and operation very attractive. Knock is a limiting factor for using gasoline spark ignition engines hence has poor efficiency. In turbocharged direct injection spark ignition (DISI) operation, bio-fuels like alcohols would reduce knock (thereby improving efficiency) and the oxygenated fuel would also help in reducing soot formation. In this study, the system modifications required to make a fuel change from diesel to alcohols in DISI mode is analysed. A numerical analysis is used to select input parameters such as inlet and exhaust cam phasing, EGR rate, spark advance and boost pressure requirements for best efficiency of the engine in full load operating conditions. The input parameters are optimised by a genetic algorithm in loop with a GT Power model of the engine with gasoline, ethanol and methanol. At peak load, it is found that the alcohols give slightly better thermal efficiency than gasoline (33% Gasoline; 34% Ethanol & 35% Methanol at 1000rpm full load) due to lower knock tendency. The boost pressure and EGR rate requirements are derived and turbo matching is performed by scaling diesel VGT maps. It was found that the ethanol and methanol case would require a VGT whereas gasoline would only need a wastegate turbocharger. Using the information from this study, a testing scheme on a single cylinder engine could be derived to validate this model for further study.

Place, publisher, year, edition, pages
2016. , 55 p.
Keyword [en]
1-D Simulation, HD engines, Alcohols, Gas Exchange system
National Category
Mechanical Engineering
URN: urn:nbn:se:kth:diva-191540OAI: diva2:957315
Available from: 2016-10-04 Created: 2016-09-01 Last updated: 2016-10-04Bibliographically approved

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