Combustion Performance and Deposit Characteristics of Boron–Aluminum Composite Fuel in a Powder-Fueled Ramjet: A Ground Test Study

Powder-fueled ramjets show great potential due to their unique advantages. How to further improve ramjet performance through methods such as fuel improvement is also an important focus. In this paper, a 14 km, Ma 3.0, ground test of a powder-fueled ramjet using boron-aluminum composite powder fuel (B-Al composite powder fuel) was conducted. The feasibility and combustion performance of B-Al composite powder fuel were verified. Under the condition of an air-fuel ratio of 19.39, the ramjet achieved independent self-sustaining combustion for 10 s, and the characteristic exhaust velocity efficiency (ηc*) reached 81.84%. Through SEM-EDS, XRD, and XPS, this study systematically analyzed the surface morphology, composition, and chemical state of the wall deposits in the combustion chamber after the test. The combustion behavior of the B-Al composite powder fuel in the ramjet was clarified. The composite powder fuel could be converted into smaller and more combustion-favorable reaction basic units during the combustion process. However, the imbalance and unevenness of Al and B in the combustion reaction and the non-reaction or reaction termination of B particles remain significant issues. This study shows that B-Al composite powder fuel has a good application basis and potential, and provides experimental data support for the subsequent improvement and optimization of the B-Al composite powder fuel system.