Aerospace Science and Technology 76 (2018) 394–401 Contents lists available at ScienceDirect Aerospace Science and Technology www.elsevier.com/locate/aescte The effect of pressure and oxygen concentration on the ignition and combustion of aluminum–magnesium fuel-rich propellant Lian-bo Li a,b , Xiong Chen a,∗ , Omer Musa a , Chang-sheng Zhou a , Min Zhu a a School of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094, PR China b Taizhou Institute of Sci. & Tech, Nanjing University of Science and Technology, Taizhou 225300, PR China a r t i c l e i n f o a b s t r a c t Article history: Received 28 August 2017 Received in revised form 24 October 2017 Accepted 29 December 2017 Available online 21 February 2018 Keywords: Fuel-rich propellant Ignition delay time Solid fuel ramjet Burning rate In order to better understand how future candidate solid propellants may affect combustion characteris- tics in ramjet motor, the aluminum–magnesium fuel-rich propellant was tested on a sealed high-pressure laser ignition platform. The laser ignition experimental device was designed and built, then the ignition and combustion characteristics of aluminum–magnesium fuel-rich propellant under different pressures and oxygen concentrations in environment gas were studied. The comprehensive impacts of pressure and oxygen concentration on ignition delay time and burning rate were appraised. The results displayed that the ignition delay time was decreased with the increase of pressure and oxygen concentration. The effect of pressure on ignition delay time was weaker than oxygen concentration. The impact of oxygen concentration on ignition was very complex. When the oxygen concentration of environment gas was less than that of the oxidizing gas from the propellant pyrolysis products, the ignition gas phase reaction occurred in the dispersion region of the solid propellant pyrolysis product, the initial flame was close to the propellant surface. In contrast, when the oxygen concentration was larger than the pyrolysis oxidizing gas, the ignition gas phase reaction occurred in the diffusion zone of the propellant pyrolysis products and the environment gas, the initial flame appeared far from the propellant surface. The burning rate of aluminum–magnesium fuel-rich propellant increased with the increase of pressure and oxygen concentration, where their effect on burning rate is accord with B-number theory. Comparing the experimental measurements with an analytical model, the results showed good consistency. The function of oxygen concentration and pressure could explain the effect on burning rate and ignition delay time, because pressure and oxygen concentration were favorable for the heat transfer, radiation and convection from the flame. The function of the combined influences of pressure and oxygen concentration on burning rate was established by a power law fitting. The good fitting is consistent with the experimental measurements, and shows that the scaling is valid for a full range of pressure and oxygen concentration tests to predict burning rate.  2018 Elsevier Masson SAS. All rights reserved. 1. Introduction The ignition process of the solid propellant has a significant effect on the interior ballistic characteristics of the ramjet mo- tor. The research on the ignition characteristics of solid propellant has great significance to reveal its ignition and combustion mech- anism, employ and develop new propellant. As early as the 1960s, many researchers began to carry out a large number of research working on the ignition performance of solid propellants, includ- ing ignition theory, ignition test method and ignition performance [1–6]. However, the ignition of solid propellant involves an array * Corresponding author. E-mail address: chenxiong@njust.edu.cn (X. Chen). of complicated physiochemical processes which is affected by the ignition energy, the propellant component, the ignition pressure and the ambient gas [7]. During the past decades, a large num- ber of researchers have devoted to the study of ignition processes and proposed a lot of theoretical models [8]. But the ignition and combustion of solid propellant have not been fully understood. Ignition delay time which is related to the heat flux, the ini- tial temperature, the ambient gas, the ambient pressure and the composition of the solid propellant, is one of the most impor- tant parameters of the ignition process. Ohlemiller [9,10] studied the effects of ambient pressure, oxygen concentration, laser flux density and the laser radiation absorption coefficient on ignition delay time. The experimental results showed that as the laser flux density, oxygen concentration and pressure decreased, the ignition delay time gradually increased until the energetic material could https://doi.org/10.1016/j.ast.2017.12.032 1270-9638/ 2018 Elsevier Masson SAS. All rights reserved.