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Askar Kazbekov
(Advisor: Prof. Adam M. Steinberg) will defend a doctoral thesis entitled,
Inter-Scale Energy Transfer in Turbulent Premixed Combustion
On
Friday, October 28 at 4 p.m.
Food Processing Technology Building, Auditorium 102 https://teams.microsoft.com/l/meetup-
join/19%3ameeting_YzBlNjJjMTgtY2IyMC00Y2FlLWIzNWEtYWZmZjQzZTNiNDA1%40thread.v2/0?cont
ext=%7b%22Tid%22%3a%22482198bb-ae7b-4b25-8b7a-
6d7f32faa083%22%2c%22Oid%22%3a%226672f38c-a0a6-4478-b20b-ebb645568f34%22%7d
Abstract
Turbulent premixed combustion is widely used for energy conversion in power generation and
propulsion devices. However, our understanding of the underlying fluid dynamics, combustion, and
their interaction is still incomplete. The complexity of turbulent combustion arises from the
non-linear, multi- scale, and multi-physics nature of the problem, which involves interactions
between fluid dynamic and chemical processes across a myriad of length and time scales. The
existing literature demonstrates that the dynamics of reacting turbulence does not necessarily
follow the same phenomenology as in non- reacting incompressible turbulence. One of the key
differences in reacting and compressible flows is the reversal of the classical turbulent energy
cascade in a process termed as ‘backscatter’. Moreover, backscatter was shown to potentially depend
on the magnitude of the pressure gradients across the flame; this is reflected in the
sub-filter-scale pressure-work. Previous studies have predominantly focused on flames in
homogeneous isotropic turbulence (HIT), in which the pressure gradients are associated with the
flame and turbulence themselves. In contrast, practical combustors have mean pressure fields
generated by the flow, which can induce significantly different turbulence dynamics as compared to
non-reacting turbulence. The presented research explores the conditions at which energy backscatter
occurs in an aerospace relevant configuration and attempts to identify the underlying physical
mechanisms that have a leading order impact on these processes. This is done through systematic
variation of the global equivalence ratio, the jet flow velocity, and the magnitude of the mean
pressure field. The impact of these controlling parameters on turbulence production and energy
backscatter is assessed through the analysis of filtered kinetic energy transport equations.
Tomographic particle image velocimetry (TPIV) and planar laser induced fluorescence (PLIF) are used
to measure the 3D velocity fields and planar distribution of formaldehyde, respectively; the
relevant thermodynamic properties (e.g., density and progress variable) are estimated from PLIF
data. Ultimately, this work provides both an assessment of the validity of current turbulence
modeling paradigms employed in aerospace relevant combustion, as well as the data necessary to
develop and validate new models if required.
Committee
• Prof. Adam M. Steinberg – School of Aerospace Engineering (advisor)
• Prof. Tim C. Lieuwen – School of Aerospace Engineering
• Prof. Joseph Oefelein – School of Aerospace Engineering
• Prof. Jerry M. Seitzman – School of Aerospace Engineering
• Prof. Ellen Yi Chen Mazumdar – School of Mechanical Engineering
