A numerical approach to reduction of NO_x emission from swirl premix burner in a gas turbine combustor

摘要

NO_x reduction in EV burners with double cone is investigated numerically by evaluation of the mixing characteristics with the parameter of modified unmixedness and NO_x emission. Modified unmixedness of fuel and air evaluated at the burner exit shows strong correlation with NO_x emission from a model combustor. Several design changes from a baseline burner have been made to enhance uniform mixing of fuel and air for the purpose of NO_x reduction. Flow and combustion fields in the combustors with the eight modified burners resulting from design changes are simulated and NO_x emissions are calculated. With a burner re-designed for lance injection, where some part of fuel is injected through the top holes of the burner, unmixedness inside the burner has been reduced, i.e., mixing uniformity improved significantly. The numerical data have been compared with available experimental data and the experimental and the numerical results showed appreciable NO_x reduction with several design changes. Another method suggested to reduce NO_x emission is to increase time for mixing of fuel and air through the increase in an interval between fuel holes. The decrease in modified unmixedness is followed by the reduction in NO_x emission. This strong correlation between unmixedness and NO_x emission verifies that NO_x reduction can be attained by mixing enhancement of fuel and air inside the burner.