FLOX^® Combustion at High Pressure With Different Fuel Compositions

In Flameless Oxidation (FLOX^®) the combustion is distributed over a large volume by a high internal flue gas recirculation. This technology has been successfully used for many years in technical furnaces under atmospheric conditions with very low NO_x emissions. In the work presented here, FLOX^® combustion was for the first time investigated at high pressure in order to assess its applicability for gas turbine combustors. A FLOX^® burner was equipped with a combustion chamber with quartz windows and installed into a high pressure test rig with optical access. The burner was operated under typical gas turbine conditions at pressure of 20 bar with thermal powers up to 475 kW. Natural gas as well as mixtures of natural gas and H₂ were used as fuel. The NO_x and CO emissions were recorded for the different operating conditions. OH^* chemiluminescence imaging and planar laser-induced fluorescence of OH were applied in order to characterize the flame zone and the relative temperature distributions. The combustion behaviour was investigated as a function of equivalence ratio and fuel composition, and the influence of the gas inlet velocity on mixing and emissions was studied. For various operating conditions the lean extinction limits were determined.