Research Progress on the Modification of B and Al High-Energy Fuels for Powder Fuel Ramjet Applications

Metal powder fuels are widely used in various fields such as aerospace, pyrotechnics, damage, and renewable energy. Recently, ramjets have gained significant attention due to their beneficial characteristics, including simple design, light weight, and high thrust-to-weight ratio. These features make them well-suited for aircraft, missiles, and unmanned aerial vehicles. However, there is a conspicuous lack of comprehensive research on modification methods and applicability into the metal powder fuels for ramjets, which creates an obstacle to further and widespread application. Therefore, this paper focuses on modifying metal fuels suitable for powder fuel ramjets. First, the effects of metal features, such as crystallinity, microscopic morphology, and particle size, on the ignition and combustion performance of fuel, flowability, and density are summarized. Second, the research discusses the modified materials and techniques of metal fuels, especially those that can be adapted to powder fuel ramjets, and systematically exhibits the properties of these modified metal fuels in terms of oxidation, ignition, and combustion. Third, the present challenges and prospects of powder fuels ramjets are discussed in detail. The paper serves as a comprehensive reference and guidance for the research on powder fuel ramjets.