Impact of alternative fuels on atomisation, noise, vibration and combustion instabilities of gas turbines

With increasing requirements for alternative fuels, a significant proportion of researchers around the world concentrate on emissions and fuel systems compatibility of novel alternative fuels. Whilst the impact of alternative fuels on combustion instability, noise, vibrations and the mechanisms behind it are relatively unexplored. In this study an investigation has been conducted to determine the impact of fuel properties on atomisation characteristics with a wide variety of novel alternative fuels and several low aromatic surrogate fuels. One investigation has been a study observing the noise and vibrations emanating from a gas turbine combustor running on alternative fuels. which has found how fuel properties have impacted the noise, vibrations and pressure oscillations of the combustor. It was found that fuels with lower density, viscosity and cetane number produce lower vibrations from a gas turbine and that increased H/C ratio has a beneficial impact on noise and vibrations. In addition, this investigation observed the noise and vibrations characteristics of a full in-service gas turbine in the form of a Honeywell APU running on 20 alternative fuels of varying properties. A key finding of this investigation is that fuel properties play a crucial role in the noise and vibrations of gas-turbines and therefore has an impact upon the wear life of engine hot-section components, which would be amplified at elevated operating pressure ratios. This finding is unique to this study.

Moreover, this investigation has determined that atomisation plays a key role in the noise, vibrations and instability a fuel generates in a gas turbine combustor and a full gas turbine. The impact of atomised fuel droplet size on engine vibration was studied, which showed that as fuel droplet size increases so does the vibrations produced by the engine.
The final knowledge contribution of this work has been the study of several aromatic species and their properties with respect to their atomisation, noise and vibrations characteristics. To this end several aromatic compounds were tested for their droplet sizes as well as noise and vibrations to determine the best aromatic for blending with kerosene. The results showed that Ethylbenzene and Cumene produced the lowest droplet sizes and vibrations.