Experimental and numerical study on laminar burning velocity and premixed combustion characteristics of NH3/C3H8/air mixtures

Propane (C3H8) is the major component of liquefied petroleum gas, the combustion of C3H8 and ammonia (NH3) should be concerned. However, there is a scarcity of experimental data on NH3/C3H8/air mixtures to validate the kinetic models, especially at elevated pressures. This work aims to provide some new laminar burning velocity data and investigate the premixed combustion characteristics of NH3/C3H8/air mixtures in detail. The mea-surement was performed at various equivalence ratios (phi = 0.6-1.4), ammonia ratios (alpha = 20 %, 50 %, 80 %), and initial pressures (P0 = 0.1-0.5 MPa). Besides, five kinetic models were compared against the experimental data, the optimal performing model was used for numerical simulation. The results show that when the mole fraction of C3H8 in fuels is 50 %, the peak laminar burning velocity is about 28.5 cm/s. And the peak value decreases to 19.0 cm/s when the initial pressure rises to 0.5 MPa. The burned gas Markstein length decreases with the increase of equivalence ratio mainly due to the remarkable effect of the effective Lewis number, and it also decreases with the increase of initial pressure because of the decreasing flame thickness. C3H8 promotes the combustion intensity of NH3, which is reflected in the enhancement of flame temperature and radical pool, but C3H8 has no obvious effect on the mixture heating value of the NH3/C3H8/air mixtures. NH3 substituting can effectively reduce CO and CO2 emissions, and the reduction effect is more significant under high NH3 mole fraction conditions.

Automated summary

This study provides new laminar burning velocity data for NH3/C3H8/air mixtures and investigates the premixed combustion characteristics in detail. The results show that propane promotes the combustion intensity of ammonia, but has no significant effect on the mixture heating value. NH3 substitution effectively reduces CO and CO2 emissions.