Defence of dissertation in the field of computational fluid dynamics and chemistry, Heikki Kahila, M.Sc. (Tech.)

Numerical modeling of spray-assisted dual-fuel ignition

The public examination of the doctoral dissertation of Heikki Kahila, M.Sc. (Tech.), will be held on 31 May 2019 at 12.00 at the Aalto University School of Engineering. The title of the dissertation is Numerical modeling of spray-assisted dual-fuel ignition. The field of the dissertation is computational fluid dynamics and chemistry.

In this dissertation work, high-performance computing was utilized for the first time in the world to provide a detailed 3D description of turbulent ignition and combustion process in a modern dual-fuel (DF) internal combustion engine. The DF engine concept is gaining worldwide popularity as liquefied natural gas (LNG) is replacing heavy oil and diesel fuel on sectors where other clean energy sources are limited, such as marine propulsion. The DF term stems from the use of secondary high-reactivity diesel fuel to improve otherwise poor ignition characteristics of natural gas, which helps to avoid incomplete combustion and high levels of harmful greenhouse gas emissions.  However, the fundamental physics and chemistry of such a multiscale DF concept are not clear and require numerical simulations.

In practice, the shortly injected diesel fuel spray autoignites and forms a spark-like ignition source, leading to a rapidly evolving combustion process and consumption of all available natural gas with less emissions. In this thesis, computational fluid dynamics was applied to resolve interactions between microscale flow structures and complex chemical reactions within the DF spray. The results provide new information on diesel fuel mixing process and quantify the chemical steps leading to the successful DF ignition. The engine manufacturers may apply these results to understand the complex ignition process and to improve its control. Similar modeling practices can be applied to investigate the combustion features of other alternative future fuels such as methanol, biogas, hydrogen and their blends.

Opponent: Professor Christer Fureby, Lund University, Sweden

Supervisor: Professor Ville Vuorinen, Aalto University School of Engineering, Department of Mechanical Engineerging

Electronic dissertation:

Doctoral candidate’s contact information: Heikki Kahila, [email protected]



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