Jerin John, Concordia University

Title: Rheological Matching between an HPMC Hydrogel Simulant and an Ethanol-Based Gelled Fuel

Abstract

Gelled propellants offer a promising alternative to traditional liquid and solid propellants. They provide increased safety, a high-performance potential, and are more environmentally friendly. However, their rheology makes atomization difficult. Most atomizers have been designed for Newtonian fluids, and not for non-Newtonian gels. Thus, the atomization of fuel gels still needs to be studied in greater depth. In this regard, since combustion is not initially necessary to study the atomization stage of gels, it is relevant to use simulants such as hydrogels instead of fuels directly. This approach helps to limit costs while avoiding the risks associated with handling and storing fuels. To simulate the most realistically the atomization of gelled fuels, it is necessary for the rheological properties of the simulants to match as closely as possible the targeted gelled fuels and this study falls within this framework. In this study, an hydroxypropyl methylcellulose (HPMC)-based hydrogels is synthesized to closely match the rheological behavior of the ethanol-HPMC gel fuels. Hydrogels of different gellant concentrations are prepared. Particular attention is made to match the viscosity curves as close as possible. Furthermore, other rheological properties, such as viscoelasticity, of the simulant and the fuel are compared in order to identify and analyze the remaining differences. Oscillation amplitude sweep and frequency sweep are done for this purpose. Thixotropy of the simulant and the impact of temperature on the rheological properties are investigated. Fourier-transform infrared spectroscopy (FTIR) is conducted to identify the chemical bond in the hydrogel. A good viscosity matching is achieved, with a similar shear-thinning behavior. However, some other rheological properties of the simulant remain different from the fuel.