Public defence in Mechanical Engineering, M.Sc. Ali Shahanaghi

Numerical modeling of thermal stratification driven combustion regimes

Improving efficiency and reducing emissions in combustion devices, such as internal combustion
engines (ICEs), is crucial for achieving emission goals. However, the reliability and performance of
these devices are significantly challenged by the occurrence of abnormal combustion, such as knocking
in ICEs. Understanding the complex relationship between various factors, such as fuel chemistry,
pressure oscillations, and auto-ignition front propagation, is still in its early stages. To address these
aspects, this dissertation focuses on the thermophysical processes responsible for abnormal combustion
under conditions relevant to SI engines. The primary objective in this dissertation is to gain a deeper
understanding of the combustion dynamics and characteristics of gasoline surrogates under varying
temperature and pressure conditions within SI engines' end-gas.
By examining the underlying thermophysical mechanisms, the purpose of the research is to elucidate
the complexity of combustion and pressure wave generation processes in modern engine combustion
context with particular interest in ignition phenomena created by hotspots. The reported studies include
the development of theory and numerical methodology along with the analysis of the simulation
results. The theoretical and computational fluid dynamics frameworks are used to address the
thermophysical phenomena in chemically reactive flows.
In the present study, the investigated ignition regimes are observed to exhibit a rich topological
structure. For instance, the findings shed light on the influence of the negative temperature coefficient
(NTC) chemistry on the appearance of different ignition regimes, the emerging combustion patterns,
and associated variations in the flow field.

Doctoral Student: Ali Shahanaghi

Opponent: Prof. Michael Lieberman, Stockholm University, Sweden

Custos: Prof. Ville Vuorinen, Aalto University School of Engineering, Department of Mechanical Engineering

The public defense will be organized online.

The thesis is publicly displayed 10 days prior to the defense in the publication archive Aaltodoc of Aalto University. 

Contact information of doctoral student:

Doctoral theses in the School of Engineering: https://aaltodoc.aalto.fi/handle/123456789/49