Effect of diluent N2 addition on NH3/H2/air combustion characteristics

Abstract

As a clean energy source with high-energy hydrogen carriers, ammonia has a promising application prospect in gas turbine power production. The existence of N2 as an ammonia combustion product and as an ammonia decomposition product at high temperatures influences ammonia combustion characteristics. Accordingly, this paper measured the combustion characteristics of the NH3/H2/air flame by the method of a constant-pressure spherical flame under different N2 dilution ratios and different equivalent ratios (0.7–1.5), with initiating temperatures of 303 K and 500 K and an initiating pressure of 1 atm, respectively. The experimental results show that the influence of diluent N2 leads to a downward trend in the laminar burning velocities (LBVs) of the NH3/H2/N2/air mixture, and the dilution effect inhibits the propagation of the NH3/H2/N2/air flame. The laminar flame propagation of the mixture is aided by the initiating temperature increase. The existence of diluent N2 reduces the major branching reactions’ net reaction and net heat production rates while enhancing inhibition of the H/OH radical pool and the rate-limiting effect of the primitive reactions. The initiating temperature reduces the impact of the radical reactions on the flame rate and enhances the chemotaxis of NHi (i = 1, 2). The diluent N2 changed the NH3 consumption and effectively suppressed the NOx production, showing the NO emission potential of NH3/H2/N2/air mixtures combustion under fuel-rich conditions.