Spontaneous-Raman-scattering measurements in diesel-like n-heptane jets: Spectroscopy and flame structure

It was demonstrated recently that quantitative temperature and CO measurements can be conducted by spontaneous Raman scattering (SRS) in non-sooting diesel-like biofuel jets in a vessel. In contrast, n-heptane is used as the fuel in the present study. This leads to slightly increased sooting tendency. One-dimensional temperature and CO measurements are generally performed successfully. Fuel-injection pressure is varied and the flame structure is characterized, including the jet core. Effects of pre-combustion mixture inhomogeneity are particularly observed at lower injection pressure (700 bar). Strong deviations from adiabatic-equilibrium conditions in terms of temperature and CO mole fraction are observed in particularly fuel-rich fluid parcels. CO formation is apparently affected by turbulent mixing there. Relatively low temperatures are measured around the flame lift-off region, in particular for the highest injection pressure (1500bar), indicating turbulence-chemistry interaction.