Numerical and experimental investigation of turbulent n-heptane jet-in-hot-coflow flames

•A combined numerical and experimental investigation of jet-in-hot-coflow flames with long chain alkanes (n-heptane) is presented.•The negative heat release area and absolute value of heat release are increased with decreased coflow oxygen levels.•The transitional flame structure, which is observed experimentally, is captured numerically for the low oxygen coflow cases.•Flames stabilized in coflows with very low oxygen level demonstrate very gradual increases in OH number density along the axial direction, and lift-off depends on the chosen threshold value of OH number density, whereas cases with higher coflow oxygen level feature clear lift-off heights.