High shear capillary rheometry of gelled hypergolic propellants
Abstract
Gelled propellants are expected to exhibit the stability and insensitivity of a solid propellant while maintaining control of mixture ratio and ability to throttle a rocket like a liquid propellant. As such, gelled hypergolic propellants are being investigated for use in standard impinging jet configurations. By understanding the effect of shear rate on gel viscosity, at the same shear rate it will experience in the injector orifice, one can estimate how readily a gel will break up into a spray under shear stress. The purpose of this study was to build a propellant grade high-shear capillary rheometer for use with gelled hypergolic propellants and obtain viscosity measurements for gels at shear rates of 105 to 106 1/s. The high shear capillary rheometer was constructed and validated with a NIST standard calibration oil and a COMSOL Multiphysics model. After validation, the viscosity of two hydroxypropylcellulose (HPC) based gels and six nano silica based particulate gels were measured with a commercial rotational rheometer and high shear capillary rheometer. High shear rate viscosity measurements simulate injector orifices and low shear rotational rheometer measurements simulate propellant storage and loading conditions. The viscosity of monomethylhydrazine (MMH)/silica gel at high shear was found to be 0.0124 ± 0.0006 Pa·s. Liquid MMH has a viscosity of 0.00086 Pa·s, indicating the gel has not reached the liquid viscosity by experiencing high shear stress. By testing gels made with different types of silica it was determined the silica's hydrophobic or hydrophilic nature dominates the gel behavior at low shear rates, and specific surface area is the more important property at high shear rates.
Degree
M.S.
Advisors
Lucht, Purdue University.
Subject Area
Materials science
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