Flame radiation & smoke emissions in gas turbine combustors

The objective of this thesis was to investigate flame radiation and smoke emission phenomena in a combustor typical of those in use in aircraft gas turbine engines. One of the primary aspects of the investigation was to compare the performance of airblast atomisers with that of conventional swirl atomisers under as near identical conditions as possible. A brief study of combustion chamber processes and carbon formation and thermal radiation mechanisms was made, with consideration of such experimental data as exists in the literature. An airblast atomiser and combustion chamber was developed to a state whereby testing at rich mixtures at moderate combustion pressures could be performed for short periods. This enabled a preliminary comparison to be made monitoring the following parameters:- (i) Flame total radiation. (ii) Exhaust smoke level. (iii) Weak extinction. Data was collected at three different combustion pressures for various air-fuel ratios and chamber velocities. The results showed that the airblast atomiser offers significant advantages over swirl atomisers with regard to total flame radiation and exhaust smoke emissions whilst suffering from a poor weak extinction. A more detailed analysis was performed for swirl atomisers using the Schmidt Method to establish flame temperatures and emissivities. The object of this work was to assess the effects of droplet size and combustion pressure on flame radiation. Owing to the poor atomisation quality and fuel distribution of the airblast atomiser used for the preliminary work, two new injectors were designed. It was hoped that a detailed analysis for these injectors could be performed via the Schmidt Method in order to provide a comparison with the swirl atomisers. Unfortunately, manufacturing was not completed with sufficient time left for this analysis to be completed.