Session: 04-20: Combustion Noise
Paper Number: 80431
80431 - Sound Generation in Multicomponent Nozzle Flows With Dissipation
Low emission aircraft engines burn in a lean regime, which makes the combustor susceptible to unsteady combustion. Along with improper mixing and air cooling, the unsteady combustion process gives rise to flow inhomogeneities. The acceleration of these inhomogeneities with the nozzle geometry downstream of the combustor generates indirect combustion noise. If the acoustic waves that are reflected off are sufficiently in phase with the heat released by the flame, thermoacoustic instabilities can occur, leading to structural damage and reducing the combustor lifetime. The generation and transmission of sound through the nozzle guide vane are typically modeled with a compact and isentropic nozzle model. In reality, the flow is non-isentropic because of losses due to wall friction and recirculation zones. Hence, a mismatch is observed in experimental and theoretical predictions for nozzles in subsonic-choked regimes. In this work, we propose a low-order physical model to predict indirect noise in a multi-component nozzle flow with dissipation using conservation laws while modeling non-isentropicity using friction. The model is generalized for finite-length (non-compact) arbitrary geometry nozzles. We show that the friction factor can account for wall friction and two (or three) dimensional effects, such as flow recirculation. We analyze the model numerically for both subsonic and supersonic nozzles, emphasizing the importance of non-isentropic and non-compact assumptions. Further, we show the results for various nozzle geometries of academic and industrial importance and compare the results with theoretical and experimental results in the literature. Furthermore, the effect of friction on thermoacoustics is studied, highlighting thermoacoustic oscillations' sensitivity to the nozzle's non-isentropicity.
Presenting Author: Animesh Jain University of Cambridge
Presenting Author Biography: Animesh is a Ph.D. student in the Department of Engineering at the University of Cambridge, UK. He is supported by the Harding Distinguished Postgraduate Scholars Programme.
Authors:
Animesh Jain University of CambridgeLuca Magri Imperial College London
Sound Generation in Multicomponent Nozzle Flows With Dissipation
Paper Type
Technical Paper Publication