Small size burner combustion stabilization by means of strong cyclonic recirculation

The exhausted gas recirculation inside the combustion chamber represents a challenging strategy to stabilize the oxidation process for novel combustion processes that aim at reducing pollutants emission, controlling the system working temperature by diluting the fresh incoming charge, and keep high process efficiency. The mass and sensible enthalpy ratio of recycled exhausted gas represents a key parameter to promote and stabilize the oxidation process. The chemical/thermodynamic features of the oxidation process were investigated by means of a numerical analysis. The process was schematized as a non-adiabatic constant-volume Continuous-flow Stirred-Tank Reactor (CSTR) where part of the exhausted gas was recirculated back to the reactor. The stability of the process was investigated as a function of the pre-heating temperature and of the dilution level of propane/oxygen/nitrogen mixtures for a fixed recirculation ratio. Following, experimental tests were realized in a small size burner characterized by a strong internal recirculation ratio, induced by a cyclonic fluid-dynamic pattern obtained by the geometrical configuration of the reactor and of the feeding system. The facility was designed to independently vary the mixture pre-heating temperatures and the mixture dilution levels. The experimental results suggest that the cyclonic configuration represents a challenging choice to stabilize the oxidation process in small-size applications. It contains the pollutants emission for a large range of preheating temperature – mixture dilution levels extending the burner operability conditions.