Experimental investigation of CH4/H2 co-firing flame structure with comparison to 1D simulation in dual-swirl injector

This study investigated CH 4 /H 2 flames in a dual-swirl gas-turbine injector, focusing on attached and lifted flame behaviors. High-speed OH-PLIF and PIV were used to analyze flame structures and flow fields as functions of hydrogen content and global equivalence ratio. The experiments were conducted at main bulk velocities of 10 and 15 m/s, global equivalence ratios of 0.5–0.7, and hydrogen contents of 20–80% depending on the bulk velocity. Increasing the hydrogen content promotes flame attachment, whereas increasing the main bulk velocity expands the lifted flame regime. The flame width and pilot flame liftoff height were extracted from the OH-PLIF images using the OTSU method and increased with hydrogen content. Both parameters exhibited strong correlations with the pilot-to-main momentum flux ratio. One-dimensional counterflow flame simulations using OPPDIF were also conducted, and comparable shape parameters were defined from the OH mole fraction profiles. Despite its simplicity, the one-dimensional model reproduced the experimental trends well, indicating that the momentum flux ratio is a key governing parameter and that one-dimensional analysis is a useful tool for interpreting the turbulent dual-swirl flame behavior.