Fig. 1. Schematic diagram of the constant volume combustion chamber system

Fig. 2. Schematic diagram of Abel inversion

Fig. 3. Schematic diagram of Onion-Peeling method

Fig. 4. Abel inversion with noise

Fig. 5. Accumulated OH self-luminescence spectral images of PODE quasi-steady state spray flame along optical path and time under different oxygen concentration conditions

Fig. 6. The variation of the lift-off length of PODE and diesel spray flame with oxygen concentration

Fig. 7. PODE spray flame images under different oxygen concentrations
(a): The averaged nature luminosity false-color images of OH spectrum; (b): The averaged nature luminosity false-color images of flame;(c): The single-shot, nature luminosity true-color images of flame

Fig. 8. Abel inversion results of PODE spray flame OH self-luminescence spectrum under oxygen-rich concentration conditions