Chemical and physical effects on lean blowout in a swirl-stabilized single-cup combustor

Abstract

Understanding the lower stability limit of gas turbine combustors is imperative for safe operation as well as for the approval of novel sustainable aviation fuels. Previous results have indicated that at relatively low temperatures and pressures (Tair = Tfuel = 238 and 258 K, P = 101 kPa, ΔP/P = 2%), the lean blowout (LBO) limits correlated to fuel physical properties, while at relatively high temperatures and pressures (Tair = 394 K, Tfuel = 322 K, P = 207 kPa, ΔP/P = 3%) chemical properties were highly correlated. This suggests that a transition occurs between physical and chemical property dependency. In the present effort, a single nozzle swirl-stabilized combustor was used to study the LBO for fuels with varying chemical and physical properties as well as operating conditions to study a transition from physical property dependence at low pressures and temperatures to chemical property dependence at higher temperatures and pressures. Four fuels with a wide range of physical and chemical properties were tested at combustor inlet conditions of Tair = Tfuel = 305–355 K, P = 107 kPa, and ΔP/P = 2–6%. It was found that the transition of LBO dependence from fuel physical to chemical properties does not happen at a single point. Rather, a transition range of conditions was observed for changes made to the pressure drop across the combustor dome (ΔP) as well as changes made to air and fuel temperature. Changes in ΔP/P were found to change the relative LBO performance across fuels and demonstrated a change in physical to chemical property dependence as ΔP/P increased. Analysis via random forest regression using dimensionless parameters such as an approximate Weber number and Ohnesorge number further highlighted the transition from physical to chemical property dependency with increasing ΔP/P.