Improving the Efficiency of Gas Engines using Pre-chamber Ignition
Författare
Summary, in English
Initial experiments using pre-chamber spark plugs without auxiliary fueling showed improvements in combustion stability, but with only a marginal extension in the dilution limit with excess air and EGR; and hence no significant fuel efficiency improvements. Following these observations, a literature survey was conducted and it was soon realized that additional fueling to the pre-chamber will help scavenge the pre-chamber at the beginning of every cycle and also lead to the formation of an easily combustible mixture inside the pre-chamber, even while the main chamber is extremely fuel-lean. Further experiments conducted on a single cylinder engine with a custom made pre-chamber assembly with auxiliary fueling showed considerable extension of the dilution limit of main chamber combustion, from an excess air ratio of about 1.7 (with an un-fueled pre-chamber) to over 2.6. The maximum indicated efficiency observed at an operating load of 10 bar IMEPg was over 47% with engine-out NOx emission levels below the 'EURO 6' limits (for heavy duty natural gas engines).
Following these finding, experiments to study the effect of pre-chamber volume and nozzle diameter on resulting main chamber ignition were conducted, where the pre-chamber volume fraction of 2.4% and the nozzle diameter ratio in the range of 0.025-0.035 (1/cm) were found to be optimum. CFD simulations were then conducted to understand the fluid dynamic aspects of interactions between the pre-chamber jets and the main chamber charge, which revealed the importance of jet momentum and jets-wall interaction on main chamber ignition. Further experiments on a large bore marine engine to understand scaling requirements for pre-chamber design showed that the optimal pre-chamber volume (and with it the nozzle diameter) scales with the displacement volume of the engine. Gross indicated efficiency of 50% was also recorded.
Avdelning/ar
Publiceringsår
2015
Språk
Engelska
Fulltext
Dokumenttyp
Doktorsavhandling
Förlag
Lund University
Ämne
- Vehicle Engineering
- Mechanical Engineering
Nyckelord
- ignition system
- high efficiency
- pre-chamber ignition
- natural gas
- Internal combusiton engines
Status
Published
Projekt
- Competence Centre for Combustion Processes
Forskningsgrupp
- KCFP
Handledare
- Per Tunestål
- Bengt Johansson
ISBN/ISSN/Övrigt
- ISBN: 978-91-7623-562-1
- ISBN: 978-91-7623-561-4
- LUTMDN/TMHP-15/1113-SE
Försvarsdatum
16 december 2015
Försvarstid
10:15
Försvarsplats
Lecure hall M:B, M-building, Ole Römers väg 1, Lund University, Faculty of Engineering, LTH.
Opponent
- Riccardo Scarcelli