Experiments and Simulations of the Cascaded Multi-Stage Impinging Jet Fuel Combustion in Solid Fuel Ramjets

This study presents a combined experimental and numerical investigation of the Cascaded Multi-Stage Impinging Jet (CAMUI) solid fuel configuration, a non-conventional architecture designed to overcome the limitations of traditional Solid-Fuel Ramjets (SFRJs). CAMUI enhances combustion efficiency and regression rate through sequential impingement of oxidizer jets onto orthogonally arranged fuel blocks, promoting super-mixing and extended residence time. Four firing tests using HDPE and oxygen were conducted, varying oxidizer flow rate and inter-block spacing. Results demonstrate high combustion efficiency (η > 0.9), with peak regression rates observed at the second block due to locally stoichiometric conditions. A validated CFD model reproduces internal ballistics and heat flux distributions, confirming experimental trends. A parametric design analysis reveals critical trade-offs between block length, count, chamber pressure, and motor dimensions, highlighting the need for optimization to balance impulse and structural constraints.