Numerical performance analysis of an annular miniature gas turbine power system using fuels with low heating values

Purpose - Utilizing renewable energy and developing new energy sources are practical responses to the shortage of fossil fuels and environmental regulations for carbon dioxide emissions. The purpose of this paper is to assess the practicability of using low heating value (LHV) fuel on an annular miniature gas turbine (MGT) via numerical simulations. Design/methodology/ approach - The MGT used in this study is MW-44 Mark I, whose original fuel is liquid (Jet A1). Its fuel supply system is re-designed to use biogas fuel with LHV. The simulations, aided by the commercial code CFD-ACE+, were carried out to investigate the cooling effect in a perforated combustion chamber and combustion behavior in an annular MGT when using LHV gas. In this study, four parameters of rotational speeds are considered. At each specific speed, various mixture ratios of methane (CH₄) to carbon dioxide (CO₂) including 90, 80, 70, and 60 percent were taken into consideration as simulated LHV fuels. Findings - The simulation results show the chamber design can create a proper recirculation zone to concentrate the flame at the center of the chamber, and prevent the flame from expanding to cause hot spot. Furthermore, the hot gas exhausted from combustor outlet is cooled down effectively by jet flow discharged from dilution holes, which prevent turbine blade from heat damage. Originality/value - Simulation results demonstrate that CFD-ACE+ can simulate flow field performance and combustion behavior in an annular MGT precisely. The results of these CFD analyses confirm that the methane fuel can be used in such small volume of MGT and still have high performance. With the aid of the constructed combustor model, the performance of a methane-used MGT can be realized before the experiment procedure starts.