Experimental study on NH3/H2/air, NH3/CO/air, NH3/H2/CO/air premix combustion in a closed pipe and dynamic simulation at high temperature and pressure

Abstract

Ammonia is a kind of carbonless alternative fuel with great research foresight. Improving the burning velocity of NH3 and studying the reduce of nitrogen oxides have far-reaching significance for the effective utilization of ammonia. This paper mainly studies the characteristics of three different mixtures (NH3:H2 = 1:1, NH3:H2:CO = 2:1:1, NH3:CO = 1:1) in closed tubes under different equivalent ratios of Ф (0.7–1.4), and use chemkin software to simulate the laminar burning velocity under different experimental conditions and at high temperature (298–650 K) and high pressure (1–10 at m), which carry out kinetic analysis and the related exploration of its nitrogen oxide emissions. The results show as follows: (1) In the closed pipe, the flame propagation speed of NH3/H2/air is the largest, when the equivalent ratio is 1.1, the flame propagation speed of three different mixtures is the highest, the overpressure phenomenon is the most obvious. and the overpressure and temperature are the highest in the pipe. (2) The symmetrical shape of the pipe changes the direction of the flame flow, creating an interesting turbulent flow that resembles a halberd. (3) Replacing half NH3 fuel of NH3/air mixture with H2 is mainly due to the chemical effect of H2 leading to the increase of LBV, while replacing half NH3 fuel of NH3/air mixture with CO is mainly due to the thermal effect leading to the increase of LBV. The promotion effect of elevated temperature is mainly due to the contribution thermal effect and chemical effect. For NH3/H2/air, chemical effect is the main component of promotion effect of elevated temperature. For NH3/CO/air mixture, the promotion effect of elevated temperature, which is more the influence of thermal effect. The inhibitory effect of initial pressure is the contribution of chemical effect. (4) High temperature promoted the formation of NO, while high pressure inhibited it.