Ansaldo Ae94.3a Combustion Improvement Towards Flexibility Through Extensive Field Testing

Being the European energy market in a sort of stagnation, flexibility is nowadays particularly profitable, with increasing care of environmental minimum load, maximum load and loading/unloading rate. For its F class model AE94.3A4, Ansaldo Energia has identified two technical keys for success:- Combustion stability- Combustion efficiencyThanks to a cooperation agreement with ENEL PRODUCTION, the largest Italian electricity utility, Ansaldo Energia had the possibility to design, introduce on one GT and test several combustion system modifications addressed to improve the performance of the whole GT by a synergy between proven design burners and cooling / sealing air optimization.During 3 months, 5 combustion system configurations have been installed and tested on the GT made available from ENEL. Taking into account that each burner is equipped with different kinds of pilot injections, the number of effective tested configurations amounts to 11.The configurations have been chosen in a large range of premixing ability, from high premixing to high diffusion rate. Due to the optimization of secondary air system, it has been necessary to install additional instrumentation in order to monitor the impact on the hot gas path components, with the aim of maintaining temperature conditions consistent with long life requirements.In the end, 3 combustion configurations were identified as able to cover 3 ranges of environmental requirements as:1 High populated residential areas (NOx emission < 30 mg/Nm(3))2 Medium populated or light industrial (NOx emission <40 mg/Nm(3))3 Very low populated areas or heavy industrial (NOx emission <50 mg/Nm(3))Premixing is generally the more effective element to defeat N-2 oxidation, with the side effect of making the combustion process particularly sensitive to pressure pulsations. So the efforts of the combustion designer have been spent to carefully modulate the injection of fuel in order to allow a good compromise between stability and emission.