Experimental Investigation of Airflow and Spray Stability in an Air-Blast Injector of an Industrial Gas Turbine

The airflow field and spray characteristics from an air blast type of injector in an industrial gas turbine (GT) combustor geometry have been investigated experimentally and numerically. The flame in the current combustor is stabilized by a highly swirling flow. The stabilization of the flame is strongly dependent on the stability of the flow field out from the injector and into the combustor. Liquid fuel spray formation in the current type of injector is highly dependent on the airflow from the internal swirler, which supplies the shear to break the liquid film, and form the spray. Experiments were performed in a Perspex model of a 12° sector of the combustor with airflow scaled to atmospheric conditions. The geometry was comprised of the air section including the full primary zone, injector, combustor swirler, front panel and primary air jets. The flow field was visualized using particles that were illuminated by a laser sheet. Quantitative characterization was done using LDA. The airflow field was characterized by the mean flow pattern covering the full cross-section of the flow field and additional long time measurements at a number of locations in order to capture frequency content of the flow. Isothermal spray measurements were performed in an unconfined geometry including the injector, swirl generator and front panel. The spray uniformity was qualitatively investigated using video camera and quantitatively characterized by PDA. The studies of the flow field and fuel atomization (droplet size and density) under different conditions are summarized below.