Femtosecond laser-induced plasma spectroscopy for combustion diagnostics in premixed ammonia/air flames.

Ammonia (NH) is a sustainable fuel with excellent emission characteristics. Hence, it is important to develop diagnostic techniques for NH combustion. In this paper, femtosecond laser-induced plasma spectroscopy (FLIPS) was performed in premixed NH/air flames. The plasma emission spectra induced by the femtosecond laser in the flame and the chemiluminescence spectra of the flame itself were both measured. Through calibration, we found that the spectral intensity ratio of NH (336  nm)/N (337 nm) could be used for equivalence ratio measurements in NH combustion flow fields. This work is the first attempt at using a femtosecond laser-based technique for NH combustion diagnostics.