MODIFICATION OF HIGH-PRESSURE COMBUSTOR TO ACHIEVE LIMIT CYCLE OSCILLATIONS

One of the major problems with the development of gas turbine engines is combustion instability and thermoacoustics. This issue arises due to lean premixed combustion, in which the flame temperature is decreased by mixing more air with fuel than is necessary for stoichiometric oxidation. The link between the combustion chamber's acoustic environment and the flame's unsteady heat release rate is the cause of these instabilities. This coupling is examined in detail in this work. A swirl-stabilized pressured preheated air/natural gas combustor's two acoustic design parameters are changed, and the possibility of thermoacoustic limit cycle oscillations is investigated. An analytical technique is used to study the sensitivity of the acoustic field as a function of combustion chamber length and reflection coefficient at the combustion chamber exit. The 1-D acoustic network model is used for the analytical analysis. This is used to investigate the effect of the change in design on acoustics. The findings showed that the instability of the combustor is more affected by changes in the reflection coefficient than by changes in length. The impact of the modification on the reflection coefficient is then verified using a pressurized combustor test apparatus. The combustor transitioned to limit cycle oscillation as expected with the change in reflection coefficient.