Rheological properties of boron-loaded gel fuel

Boron-loaded gel fuel is an ideal propellant for limited-volume propulsion devices such as ramjets. However, its high viscosity and complex rheological properties pose significant challenges to its practical application. In this study, a novel gel fuel with 50wt% boron content was used as the research object. Based on the complex service environments in engineering applications, a series of experiments were designed to investigate the effects of shear rate change rate, constant shear duration, pre-shearing, and temperature on the viscosity of boron-loaded gel fuel. The experimental phenomena were analyzed in depth based on shear stress. The results show that under constant shear rate, the time-dependent viscosity of boron-loaded gel fuel can be accurately described by a power function with a constant term. Pre-shearing can effectively destroy the structure of the boron-loaded gel system and make it difficult to recover within a finite time. High-low temperature cycling can hardly destroy the gel structure but can reduce its structural strength. At a constant shear rate, there exists a critical temperature: below this temperature, the viscosity of the gel fuel is negatively correlated with temperature; above this temperature, the viscosity does not change significantly. Based on shear stress analysis, it is inferred that the boron-loaded gel system has a multi-level structure. Under high-low temperature cycling, the recovery ability of the secondary structure is stronger than that of the main structure.