Shock tube and modeling study on the ignition delay times of ammonia/ethylene mixtures at high temperatures

Abstract

Ammonia is a promising alternative clean fuel due to its carbon-free, high energy density and well-established infrastructure of storage and distribution. The co-combustion with reactive fuels improves the NH combustion stability. Moreover, CH is an important intermediate product in the oxidation of many hydrocarbon fuels. Therefore, some researchers focused the fundamental study and soot formation of NH/CH combustion. A reliable combustion model of NH/CH advances the understanding of the interaction between NH and CH. The key to develop the model of NH /CH is the cross reactions between N-containing species and C-containing species. In this work, the ignition delay times of NH/CH mixtures were measured at three blending ratios (95 %, 90 %, 70 % NH) at 1.75atm and 10atm in a shock tube at the temperature range of 1247 K to 1786 K. A detailed chemical kinetic model was developed on the base of our previous optimizing NH model and the CC sub-model of NUIGMECH1.1, and some new cross reactions between N-containing species and hydrocarbon species were considered in the model. The NH-CH model is validated by the current experimental data, the laminar flame speeds of NH/CH mixtures and the species profiles of NH/CH mixtures oxidation. The cross reactions considered in this work significantly improve the prediction. The disproportionation reactions, CH + NH <=> CH + NH (R1466) and HCO + NH <=> CO + NH (R1465), significantly inhibit the ignition and the flame propagation, and cause the increase in the formation of HCO and HCCO with the increase of NH content, which facilitates the reduction of the soot formation.