The governing equations of the steady e ow of gel propellants and fuels in a tapered tube injector have been formulated assuming a power-law rheological model. A parametric investigation was conducted to evaluate the effect of the injector geometry and pressure gradient on the e ow rate and the mean apparent viscosity of the gel for various fuels and metal loadings. The theoretical results indicate that the e ow rate increases signie cantly with decreasing thepower-law index and with increasing the pressuredrop in the injector. Theapparent viscosity is not uniformineachcrosssection;itismaximalattheaxisandreachesminimumatthewall.Themeanapparentviscosity of the gel exhibits a signie cant decrease with increasing the convergence angle of the injector. This implies that to obtain betteratomizationofthegel,high convergenceanglesarerequired.AcomparisonbetweenRP-1/Algelswith various aluminum mass fractions was conducted. The results indicate the existence of an optimal metal loading.