Session: 04-42 Combustion dynamics - flow instabilities

Paper Number: 128504

128504 - Reduced Order Model for Cavity-Based Combustors Describing Various Bifurcations As Cavity Size Is Varied 

In cavity-based combustors, commonly used for flame stabilisation; large-amplitude pressure fluctuations can occur as the flow passes through cavities (aeroacoustic instabilities modulates equivalence ratio) . In present framework experiment were conducted in a laboratory scale trapped vortex combustor by varying cavity sizes (L/D=0.75-2.65)  i.e. varying the cavity length (L). Unsteady pressure measurements reveal a bifurcation route of limit cycle → period-2 →quasiperiodic → Strange non-chaotic attractors → chaos as  cavity size is increased (L/D) increases. This transition leads to 70% reduction in pressure amplitude (from limit cycle case to choas regime) and moreover limit cycle transitions to noisy or chaotic regime as cavity size is increased, which can be essential passive control. In this study we have used a reduced order model which incorporates the acoustic-hydrodynamic coupling. Additionally, our model includes a feedback mechanism accounting for the influence of acoustic modes on vortex shedding patterns. This feedback mechanism induces changes in the timescale of vortex impingement as cavity size varies, leading the system through different nonlinear regimes, including chaos and limit cycle dynamics. We validated our model by comparing its predictions with experimental results, highlighting its ability to capture the intricate dynamics observed in the cavity-based combustors as cavity size is varied.

Presenting Author: Vineeth Nair Indian Institute of Technology Bombay

Presenting Author Biography: Dr. Vineeth Nair is currently Associate Professor at Indian Institute of technology, Bombay, India. He is majorly working on aeroacoustics and thermoacoustic instabilities.

Authors:

Ashutosh Singh Indian Institute of Technology Bombay
Vineeth Nair Indian Institute of Technology Bombay