Experimental studies on injection nozzle flame stability for gas turbines using in-situ combustion applications

This paper presents the experimental results of the test conducted on 3 different geometries for injection nozzles. The objective of these experimental studies was to determine the optimal configuration with respect to flame stability in high velocity flows and aiming for an increase in temperature small enough to be comparable with the decrease in temperature due a subsequent expansion. These conditions are a consequence of the intended application, gas turbines using in-situ combustion. This uses a supplementary combustion in the turbine, intended to best approximate an isothermal expansion that would ensure a better efficiency for the gas turbine. Taking into account the drop in temperature is of approximately 100 degrees after a turbine stage, and the flow velocity is about 100 m/s at the exit of the turbine stage, a suitable solution was sought. The experimental results shown that none of the tested configurations matched the desired conditions, but one of the three geometries had a significantly better behaviour. At the same time, it was concluded that the number and dimension of the injection holes do not play a major role in flame stability in high velocity flows, but rather their shape. The injection nozzles with divergent holes proved to be the most stable and to provide the smallest increase in temperature for high velocity flows.