Design and Assessment of a Fuel-Flexible Low Emission Combustor for Dry and Steam-Diluted Conditions

In the present study a new combustor design for swirl-stabilized premixed combustion is presented and analyzed. By means of axial air injection into the mixing tube, the flow field inside the mixing tube and combustion chamber is altered for the purpose of increasing flame stability, resulting in low lean blow-out limits and flashback safety. For this reason, the combustor design is suited for fuel-flexible combustion over a wide range of reactivities including those of pure hydrogen and natural gas. Furthermore, the combustor design is suitable for high amounts of steam injection, significantly decreasing NO_x emissions. The assessment of the flow field properties is conducted under isothermal and reacting conditions and the results are in good agreement. The fuel-air-mixing quality is examined by water tunnel experiments using laser induced fluorescence and show low levels of unmixedness. Flame properties are assessed by means of OH planar laser induced fluorescence and OH*-chemiluminescence. Emission probing of major combustion species was also conducted.