Mei-Shuai Zou

Three metal powders of Mg, an Al-Mg alloy (AM) and Al are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) techniques. This study focuses on the reactions of the metal powders with flowing steam heated at 600°C, 700°C, 800°C, and 900°C in a transparent pipe furnace. The phases of the solid reaction products are analyzed using XRD, and the residual metal content and ignition delay times are measured. The experimental results revealed that the Mg and AM powders ignite and burn in the 600°C heated steam; however, the Al powders do not ignite even at 900°C. The ignition delay time of AM powders was shorter than that of the Mg powders. The Al in the AM and Al powders does not react completely even when the temperature reached 900°C; however, the content of unreacted Al in the AM powders (13.9%) was much less than that in the Al powders (82.2%) at 900°C. The combustion process of the AM powders at 600°C is divided into three stages: the Mg in the alloy (Al₁₂Mg₁₇) first reacts with water to form magnesium hydroxide, and the remainder of the Al and Mg in the alloy formed the new alloy phase; then, the magnesium in the new alloy phase continues to react, forming magnesium oxide, and remaining elemental Al exists; finally, ignition occurs, and the aluminium in the AM powders reacts with the heated steam, forming Al₂MgO₄.

Experiments were conducted to study the effect of magnesium–aluminum alloy on the combustion performance of hydroreactive fuel propellants. The raw metal powders added to the propellants were ball-milled magnesium–50% aluminum alloy (m-AM), magnesium–50% aluminum alloy (AM), and Al and magnesium (Mg) powders, which were characterized using scanning electron microscopy, X-ray diffraction (XRD), and simultaneous thermogravimetric analysis (TGA). A high-pressure combustor and a metal/steam reactor were used to simulate the two-stage combustion of hydroreactive propellants used for a water ramjet. The combustion performance of the metal powders in propellant was studied experimentally, and the efficiency of the Al reaction in the propellants during the two-stage combustion was calculated. TGA traces in air indicated that the oxidation onset temperature of AM powders is much lower than for both Mg and Al powders. The XRD patterns for the AM and m-AM alloys exhibited Al₁₂Mg₁₇ diffraction peaks. The hydroreactive fuel propellant systems with added m-AM powder exhibited good performance in terms of burning rate, combustion heat, and the Al reaction efficiency, which was better than that for the propellants containing AM, Mg, and Al powders. At the pressure studied (3.0 MPa), the burning rate of the m-AM-containing propellant was found to be 15 mm s⁻¹, and the heat of primary combustion was 6,878.1 kJ kg⁻¹.

A high-pressure combustor and a metal/steam reactor are used to simulate the two-stage combustion of hydro-reactive propellants used for a water ramjet. Raw metal powders added to the propellants are the aluminum power, magnesium powder, 50/50 aluminum-magnesium alloy (AM), and ball-milled 50/50 aluminum-magnesium alloy (b-AM), which are characterized by using scanning electron microscopy (SEM), x-ray diffraction (XRD), and simultaneous thermogravimetric analysis (TGA). The efficiencies of the Al reaction in the raw metal in heated steam and in the propellants during the two-stage combustion are calculated. The results indicate that both Mg and Al in the alloys, whether b-AM or AM, can react completely in air when heated up to 950°C. The XRD patterns for the combustion products of the AM and b-AM alloys in heated steam contain magnesium oxide MgO, spinel Al₂MgO₄, and Al diffraction peaks. The Al reaction efficiencies of the AM and b-AM alloy powders in heated steam are much higher than that of the Al powders. The hydroxyl-terminated polybutadiene (HTPB)-ammonium perchlorate (AP)-(b-AM)-Mg and HTPB-AP-AM-Mg propellant systems exhibit good performance in terms of the Al reaction efficiency, which are better than that of the HTPB-AP-Al-Mg and HTPB-AP-Al systems.

A high‐pressure combustor and a metal/steam reactor were used to simulate the two‐stage combustion of a fuel‐rich propellant used for water ramjet engines. The solid combustion products from the two stages were collected and characterized by scanning electron microscopy (SEM) and X‐ray diffraction (XRD). In addition, the thermal properties of the solid products of the primary combustion were characterized by differential thermal analysis (DTA) and simultaneous thermogravimetry (TG). The burning rates at different pressures were measured and the secondary combustion process in hot steam was monitored by high‐speed cinematography. The results showed that the propellant has a good combustion performance and a high burning rate. After primary combustion, the solid product mainly contained magnesium, magnesia, magnesium chloride, and carbon. During the secondary combustion, the ignition temperature was approximately 720 °C, and two burning stages were observed. The rest of magnesium hasn’t completely reacted with hot steam until the temperature reached a value higher than 800 °C for 30 min.