Prediction of limit cycle oscillations in gas turbine combustion systems using the Flame Describing Function

On Prediction of Combustion Generated Noise with the Turbulent Heat Release Rate

“…In the OpenFOAM implementation, the BC behaveslikealow pass filter with the cut-off frequencyd epending on the relaxation time τ,w hich is proportional to the ratio of ag iven length and the sonic speed. Hence, the reflection coefficient attained depends on the frequencyand τ;itapproaches the value zero in the high frequencyrange and one in the lowfrequencyrange, as noted in [4,44]. At oo large value of τ may cause the mean flowv ariables to drift away from the desired values, whereas small τ values may lead to instability of the simulation due to high frequencies reflections [44].…”

“…Hence, the reflection coefficient attained depends on the frequencyand τ;itapproaches the value zero in the high frequencyrange and one in the lowfrequencyrange, as noted in [4,44]. At oo large value of τ may cause the mean flowv ariables to drift away from the desired values, whereas small τ values may lead to instability of the simulation due to high frequencies reflections [44]. In the current work, the domain length is chosen to evaluate the relaxation time for optimum results.…”

“…Although being only partially reflecting, in practice fully non-reflective boundary conditions may be ill-posed as well as with such conditions information about the farfi eld properties (e.g. the mean inlet velocity and mean outlet pressure)could not propagate into the system; therefore as mall percentage of reflection is generally required [43,44]. In the OpenFOAM implementation, the BC behaveslikealow pass filter with the cut-off frequencyd epending on the relaxation time τ,w hich is proportional to the ratio of ag iven length and the sonic speed.…”

A Computational Study of Transverse Combustion Instability Mechanisms

“…17 There is also ongoing work to extend subscale results to full-scale engines by using data from experiments and validated CFD simulations to develop combustion response functions for engineering-level design analysis models. 18 The approach described here uses a subscale injector with seven elements. The transverse mode of the rectangular chamber is on the order of 2 kHz, which is similar to transverse mode frequencies in full-scale rocket combustors.…”

Non-linear behavior of the thermoacoustic oscillations in the LIMOUSINE combustor

“…The Rayleigh criterion is a tool to examine the stability of a system. If the energy flux from the flame to the acoustic field is greater than the losses, the amplitude of the pressure oscillations will grow every cycle until the two quantities are in balance [50][51][52]. At this point, the amplitude remains constant over time and this unstable regime is called Limit Cycle of pressure Oscillations (LCO).…”