Hydrogen Combustion at High Combustor Airflow Using an Impinging Jet Flame Stabiliser With No Flashback and Low NOx

Abstract

The feasibility of hydrogen as a fuel for industrial gas turbines with low NOx emissions was investigated. Conventional well mixed flame stabilisers are difficult to use with 100% hydrogen owing to the flash back problem, which is potentially seven times worse for hydrogen due to its higher reactivity. This work was carried out using a rapidly mixed Jet Mix design, which had previously been investigated with NG and propane. This consisted of eight radial air jets into which the fuel was injected on their centrelines. These radial jets impinged into eight axial air jets which carried the bulk of the combustion air. Radial jet air flow proportions of 6.5% and 20% were investigated at an overall pressure loss at M1 = 0.047 of 4.3% in a 76mm diameter combustor. The reference Mach number, M1 of 0.047 represents all the compressor exit air entering the combustor with no dilution air. Very lean mixtures are required for low NOx emissions and there is no flame stability issue with hydrogen combustion, so all power turndown can be achieved with one main fuel injector. An inlet temperature of 600K was used at atmospheric pressure and the flames were lean enough to have temperatures where there was no pressure dependence of thermal NOx. For 6.5% radial air NOx emissions of 25ppm at 15% oxygen were demonstrated at 1800K and lower NOx at lower turbine entry temperatures.