The effects of water addition on pollutant formation from lpp gas turbine combustors

Lean premixed prevapourised (LPP) combustion of liquid fuels with steam dilution and under high pressure conditions is numerically assessed. A detailed chemical kinetic mechanism for n-heptane and iso-octane combustion is assembled on the basis of existing detailed mechanisms and validated against experimental data from laminar premixed flames. A computational singular perturbation (CSP) method is then used to analyse and reduce the mechanism to one global step. This reduced mechanism forms the basis for the reaction progress variable (RPV) approach from the CFI combustion model. The obtained one-step combustion mechanism is validated by comparing the CFI model results, stored in a thermochemical database as a function of the RPV, with detailed laminar flame solutions in reaction progress variable space. The single step global mechanism is then used to assess, under LPP gas turbine operating conditions, the influence of dilution and fuel equivalence ratio on iso-octane and n-heptane combustion. The above formulation is shown to accurately capture NO and CO emission trends.