Establishing Flashback and Blowout Limits in a Commercial Lean Premixed Combustor Operating on Synthesis Gas

Flashback and lean blowout are operability issues that must be addressed for successful operation of stationary gas turbines. The present work focuses on flashback and lean blowout of premixed jet flames in a combustor from a commercially available gas turbine operating on synthesis gas of various compositions. The issues of flashback and lean blowout are exacerbated when operating on fuels with high hydrogen content due to the increased reactivity of hydrogen, thus increasing the propensity for flashback. Operating margins for mixtures of natural gas (NG) and carbon monoxide (CO) in hydrogen (H₂) are reported. The results demonstrate less stability near lean blowout for mixtures of H₂/NG than for H₂/CO. Increasing H₂ concentration extends the lean operating limit from &PHgr;= 0.63 to &PHgr;= 0.29 for H₂/NG and &PHgr;= 0.42 to &PHgr;= 0.29 for H₂/CO. Modeling of the experimental data using a perfectly stirred reactor indicates that the Damköhler number well characterizes the effects of the addition of H₂ to NG on the lean blowout limits. In addition, key factors dominating flashback behavior are identified and included in a predictive methodology. A response surface, developed from a turbulent flame speed database, is used to create a flashback propensity index as a design tool for quantifying flashback based upon experimental data from the combustor. Furthermore, the Damköhler number is explored as an index for predicting flashback and was determined to be effective at capturing the effect of pressure, making it able to link data taken at atmospheric conditions to expected engine results.