GT-AE presents
a lecture by

Dr. R.I. Sujith
Prognosis of an Impending Combustion Instability

Thursday, July 23
11 a.m. – noon
Guggenheim 442

The transition in dynamics from low-amplitude, aperiodic, combustion noise to high-amplitude, periodic, combustion instability in confined combustion environments was studied experimentally using two laboratory scale turbulent combustors. We show how combustion noise that appears to have a Gaussian distribution and a broad-band spectrum in frequencies is in fact borne out a deterministic process and is not just the result of a stochastic process. We further show that ‘combustion noise’ is composed of low amplitude chaotic fluctuations that display scale invariance and multifractality that disappears at the onset of combustion instability. Traditional analysis or phenomenological models usually neglect or average out these fluctuations or treat them as a stochastic background. We show how techniques such as the FFT are incapable of describing the complexity of the underlying dynamics and hence are unable to predict the onset of an impending instability. Most importantly, we demonstrate that the irregular fluctuations contain useful information of prognostic value by defining representative measures that can act as early warning signals to impending instability in practical gas turbine combustors.

About the speaker:
Dr. R. I. Sujith graduated with his B. Tech in Aerospace Engineering from the Indian Institute of Technology Madras in 1988 with first rank. He received his M. S. (1990) and Ph. D. (1994) from the Georgia Institute of Technology, working with Prof. Ben Zinn, and he received the “top graduate student in the college of engineering” award. He worked as a post-doctoral fellow at the Georgia Institute of Technology in 1995.

He joined the Department of Aerospace Engineering at the Indian Institute of Technology Madras in 1995 and is a full professor since 2006. He is also a Hans Fischer Senior Fellow of the Institute for Advanced Study (IAS) of the Technical University of Munich. 

Sujith is the Editor-in-Chief of the International Journal of Spray and Combustion Dynamics. He is a recipient of the Alexander Von Humboldt Fellowship. As a Humboldt Fellow, Sujith worked at DLR Göttingen and at the Technical University of Munich. He has won the Young Engineer Award of the Indian National Academy of Engineering. He has been awarded the Swarnajayanti Fellowship by the Department of Science & Technology, and the Institute Research & Development Award (Mid-career) of IIT Madras. He is a fellow of the Indian National Academy of Engineering and an associate fellow of the AIAA, and has been conferred the title of “TUM ambassador” or the Technical University of Munich. 

Sujith is credited with the discovery of non-normality in thermoacoustic interactions and its role in subcritical transition to instability. Further, he is credited with the establishment of the route to chaos in thermoacoustic systems. He also discovered intermittency in thermoacoustic instability. His recent work includes precursor detection for an impending instability, before it occurs, and application of complex networks to thermoacoustics.