Development and Design of Alstom’s Staged Fuel Gas Injection EV Burner for NOx Reduction

Abstract

Alstom’s combustion development on the EV burner concept has taken another step forward with the introduction of a staged premix system, which allows even lower NOx values also at lower part load values compared to the pilot/premix EV burner. The development target was achieved by introducing one fuel stage over the conventional EV fuel lance, while other fuel stage is realized with a gas hole injection pattern over the EV air slots, similar to the conventional EV burner system. Due to this no major design modifications for the EV burner system were required, and the new system is fully retrofittable to the existing GT26 gas turbine engines including the existing fuel distribution system. The final design is a result of a step-by-step development. In a first step, variants defined in a feasibility study by CFD calculations indicated that a staged fuel gas injection over the fuel lance could substitute a part of the conventional premix gas injection. The water tunnel tests results performed with the LIF measurement technique demonstrated the improved mixing properties of the staged EV burner in the burner flow field. With a single burner test facility under atmospheric pressure conditions the broad operating range of the staged EV burner system could be confirmed. The single burner tests allowed investigation of the low NOx operating range for the burner system also with respect to flame generated instabilities. Finally the burner system was validated with gas turbine engine tests at the Alstom GT Test Power Plant in Birr, Switzerland, which demonstrated the excellent combustion performance of the staged EV burner system derived by the development procedure.