Combustion stage configurations for intercooled regenerative reheat gas turbine systems

Low-power gas turbines have been widely used for decades as combined heat and power. In the recent years, they received increasing interest with respect to applications such as range extenders in the automotive sector and for alternative fuels use. In this framework, the present work analyzes the combustion stages optimization of an intercooled regenerative reheat gas-turbine system, for a low power gas turbine. In particular, a thorough analysis was carried out to identify the optimal combustion system configuration in order to ensure suitable turbine inlet temperature and global efficiency of the thermodynamic cycle higher than 40%. Starting from the typical intercooled regenerative reheat gas turbine system, several configurations were analyzed. In particular, air bypass systems were introduced as suitable strategy able to tune the combustion chamber working temperatures and turbine inlet ones, according to operating requirements and combustion unit specifications. Furthermore, different bypass ratios were considered, analyzing the effectiveness of air bypass systems in terms of efficient combustion and reduced pollutant emissions (CO and NOx). An innovative cyclonic flow burner, assumed to operate under MILD (Moderate or Intense Low oxygen Dilution) combustion conditions, was considered as main combustion unit and in the reheat process. In this respect, the choice was motivated by the well-established high fuel flexibility and very low pollutants emission typical of such a combustion unit and the MILD process. Analyses were performed considering methane as fuel, which is currently the most used fuel in land-based applications. However, results here reported have general validity and may be directly applied with respect to the use of innovative energy vectors.