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

A turbulent n-heptane jet flame in a jet-in-hot-coflow burner is numerically and experimentally investigated, revealing distinct features of this fuel in a jet-in-hot-coflow burner. The RANS k-epsilon turbulence model is adopted in combination with a dynamic partially-stirred reactor (PaSR) combustion model. The simulation results are used to support newly-obtained experimental measurements of mean temperature, OH number density and normalised CH2O-PLIF signal values at several axial locations. The simulations capture the transitional phenomenon observed experimentally for the low coflow oxygen concentration case, which is determined to be due to the two chemical pathways which exist for the n-heptane fuel. The predicted flame weak-to-strong transition heights based on the streamwise (axial) gradient of OH number density show non-monotonic behaviour. Furthermore, an investigation on negative heat release rate region shows that the absolute value of negative heat release rate increases with reduced coflow oxygen content, in contrast to the suppression phenomenon seen in laminar opposed-flow flames.

Automated summary

The study investigated a turbulent n-heptane jet flame in a jet-in-hot-coflow burner through numerical and experimental methods, revealing unique features of this fuel in the burner. The simulations captured a transitional phenomenon observed experimentally for low coflow oxygen concentration case, with predicted flame weak-to-strong transition heights showing non-monotonic behavior. Investigation on negative heat release rate region showed an increase in absolute value with reduced coflow oxygen content, contrary to the suppression phenomenon seen in laminar opposed-flow flames.