Control of Thermoacoustic Instabilities in a Rijke-type Combustor by Outer Wall Temperature

Self-sustained thermoacoustic instability can occur in premixed combustors when fluctuations in pressure and heat release couple positively, causing high-amplitude acoustic oscillations. This study investigates the effect of outer combustor wall temperature on the growth of thermoacoustic instability using a two-dimensional unsteady Reynolds-averaged Navier–Stokes (RANS) model of a Rijke-type combustor. The numerical approach is explored as a means for effective instability control by examining how boundary condition modifications influence instability characteristics. Seven cases with isothermal wall conditions at 100K intervals between 300K and 900K are compared against an adiabatic reference. The results show that increasing wall temperature reduces limit cycle oscillation amplitudes and that at an outer wall temperature of 900 K results in sustained stability, yielding a negative growth rate. This Study suggests that increasing wall temperatures mitigates instability primarily by altering the acoustics-flow-flame interaction near the flame base, thus decreasing the Rayleigh index. Overall, controlling wall temperature offers a promising strategy for stabilizing thermoacoustic combustors and provides an alternative approach for damping such instabilities.