NUMERICAL INVESTIGATION OF ENHANCED DILUTION ZONE MIXING IN A REVERSEFLOW GAS-TURBINE COMBUSTOR

An advanced method for dilution zone mixing in reverse flow gas turbin e combustor was numerically investigated. For long mixing lengths asso ciated with reverse flow combustors (X/H > 2.0), pattern factor was fo und to be mainly driven by nozzle-to-nozzle fuel flow and/or circumfer ential airflow variations; conventional radially injected dilution jet s could not effectively mix out circumferential nonuniformities. To en hance circumferential mixing, dilution jets were angled to produce a h igh circumferential (swirl) velocity component. The jets on the outer liner were angled in one direction while the jets on the inner liner w ere angled in the opposite direction, thus enhancing turbulent shear a t the expense of jet penetration Three-dimensional CFD calculations we re performed on a three-nozzle (90 deg) sector, with different fuel fl ow from each nozzle (90, 100, and 110 percent of design fuel flow). Th e computations showed that the optimum configuration of angled jets re duced the pattern factor by 60 percent compared to an existing convent ional dilution hole configuration. The radial average temperature prof ile was adequately controlled by the inner-to-outer liner dilution flo w split.