STRUCTURE AND NO EMISSION OF TURBULENT HIGH PRESSURE LEAN PREMIXED METHANE/AIR FLAMES

摘要

Lean premixed combustion of gaseous feels is widely used in stationary gas turbines because of high efficient energy conversion and low NO_x emissions. The main characteristics of these flames are: High turbulent Reynolds numbers, Damkohler numbers around unity, Karlovitz numbers greater than 10, lean equivalence ratios and high pressures. In the present study the influence of turbulence on mean flame front position, flame structure, and NO emission has been experimentally investigated at gas turbine relevant conditions in a generic combustor with aerodynamic flame stabilization. A systematic variation of the turbulent Reynolds -, Damkohler - and Karlovitz number has been performed, by changing the pressure, the equivalence ratio and the Met velocity. Planar Laser-induced Fluorescence of the OH radical (OH-PLIF) was used to detect the flame front. NO_x/NO concentrations have been measured with conventional exhaust gas analysis in comparison with planar NO-LIF. Increasing the pressure and thereby increasing primarily the turbulent Reynolds number causes the mean flame front position to shift slightly towards the combustor Met and, in parallel, the flame front Is Increasingly corrugated. For a constant turbulent Reynolds number decreasing the equivalence ratio and thereby changing the Damkohler - and Karlovitz number has the strongest effect on the mean flame front position. The flame is shifted downstream and the flame front is increasingly corrugated. This is accompanied by a strong decrease of the NO concentration.