Chemical Kinetic Modelling of the Evolution of Gaseous Aerosol Precursors Within a Gas Turbine Engine

Abstract

A sequence of kinetic models has been developed to simulate the chemical processes occurring throughout the hot section of a modern gas turbine engine. The work was performed as part of the EU funded PARTEMIS programme, which was designed to investigate the effect of both engine condition and fuel sulphur content on the production of gaseous aerosol precursor such as SO3, H2SO4 and HONO. For the PARTEMIS programme, a Hot End Simulator (HES) was designed to recreate the thermodynamic profile through which the hot gases pass after leaving the combustor. Combustion rig tests were performed in which the concentrations of gaseous product species were measured at the exits of both the combustor and the HES. These measurements were used to validate the kinetic models. The combustor was modelled by a sequence of five perfectly stirred reactors, using the Combustor Model Interface (CMI) developed at the University of Leeds. The CMI allows for the addition of dilution air at each stage of the combustor as well as re-circulation between each stage. The results at the combustor exit were then used as initial boundary conditions for the HES model, which followed the evolution of reacting gases through each of the pressure stages of the HES. This combination of the two models allowed the chemistry occurring throughout an engine, from combustor inlet to turbine exit, to be simulated. The principal aim of this modelling programme was to determine the extent of conversion of the sulphur (IV) species, SO2, to the sulphur (VI) species, SO3 and H2SO4. The predicted level of this conversion at the exit of the HES was found to be in very good agreement with the experimentally measured values. These values were lower than had been previously determined by modelling studies and this was found to result from changes made to the thermodynamic properties of the key intermediate, HOSO2, following recent experimental measurements. The results also showed that for these tests, the predominant sulphur conversion process occurred within the combustor itself rather than the turbine or beyond.