On the effects of convecting entropy waves on the combustor hydrodynamics

• Published in: Applied thermal engineering 2017-01, Vol.110, p.901-909
• Main Authors: Hosseinalipour, S.M., Fattahi, A., Afshari, H., Karimi, N.
• Format: Article
• Language: English
• Subjects: Combustor hydrodynamics; Convecting entropy waves; Streamline wrapping and coiling; Vorticity and helicity vector
• ISSN: 1359-4311
• DOI: 10.1016/j.applthermaleng.2016.08.220

•Passage of entropy wave results in more streamlines wrapping.•Effect of the annihilation of entropy waves on the helicity field may be considerable.•Convection of the waves changes the alignment of velocity and vorticity vectors. Entropy waves, as hot spots or density inhomogeneities, can be generated by the flame unsteadiness in combustors. These waves are convected downstream while being annihilated by the flow decay and dispersion mechanisms. This results in the diffusion of the enthalpy of the wave within the base flow. Decaying entropy waves may, therefore, affect the density and viscosity of the base flow and consequently modify the combustor hydrodynamics. Study of such hydrodynamic modifications is the objective of the current numerical study. In particular, the extent of induced changes in the flow is investigated. To do so, some hydrodynamic indices are introduced, in which vorticity magnitude and the angles between the velocity and vorticity vectors are the main parameters. In keeping with the previous studies, entropy waves are inserted at the channel inlet by a linear-increment and exponential-decrement temperature function in a cold flow. A more realistic, and rarely investigated thermal boundary condition of convective type are considered on the walls of the channel. The results show that convection of the entropy waves through the channel noticeably changes the hydrodynamic parameters, such as vorticity vector, helicity and streamlines alignment. This is in contrast with the general notion, which regards entropy waves as passive scalars.