Botchu Vara Siva Jyoti

Rheological Characterization of Hydrogen Peroxide Gel Propellant

An experimental investigation on the rheological behavior of gelled hydrogen peroxide at different ambient temperature (283.15, 293.15 and 303.15 K) was carried out in this study. The gel propellant was rheologically characterized using a rheometer, in the shear rate ranges of 1 to 20 s -1 , and 1 to 1000 s -1 . Hydrogen peroxide gel was found to be thixotropic in nature. The apparent viscosity value with some yield stress (in-case of shear rate 1 to 20 s -1 ) drastically fell with the shear rate. In the case of the shear rate range of 1 to 20 s -1 , the apparent viscosity and yield stress of gel were significantly reduced at higher ambient temperatures. In the case of the shear rate range of 1 to 1000 s -1 , no significant effect of varying the ambient temperature on the gel apparent viscosity was observed. The up and down shear rate curves for hydrogen peroxide gel formed a hysteresis loop that showed no significant change with variation in temperature for both the 1 to 20 s -1 and the 1 to 1000 s -1 shear rate ranges. No significant change in the thixotropic index of gel was observed for different ambient temperatures, for both low and high shear rates. The gel in the 1 to 20 s -1 shear rate range did not lead to a complete breakdown of gel structure, in comparison to that in the 1 to 1000 s -1 shear rate range.

Formulation and Comparative Study of Rheological Properties of Loaded and Unloaded Ethanol-Based Gel Propellants

The current trend in the area of highly energetic storable liquid rocket propellant research is to develop environmentally friendly gelled/metallized systems and to explore the feasibility of their application in rocket engines. The idea stems from the fact that the conversion of a conventional liquid propellant to a gelled state and its subsequent metallization has the potential to significantly enhance the performance and density-specific impulse. The gelation of liquid fuels could be induced at a critical gellant concentration of as low as 8 wt% for the pure ethanol case and as low as 4 and 6 wt% for metallized ethanol depending on the metal type. Furthermore, the gel formed should be thixotropic. Metallized gels using 20 wt% Al and B metal powders could also be formulated. These metallized (Al and B) ethanol gel systems showed a reduction in the critical gellant concentration depending on the degree of metallization. The rheological properties of metallized and nonmetallized ethanol gels using methyl cellulose (MC) as a gelling agent at different ambient temperatures (283.15, 293.15, 303.15, 313.15, and 323.15 K) were experimentally investigated in this study. The gel fuels were rheologically characterized using a rheometer at shear rates ranging from 1 to 12 s−1 and 1 to 1,000 s−1. Metallized and nonmetallized ethanol gels were found to be thixotropic in nature. The apparent viscosity and yield stress (for shear rate range 1 to 12 s−1) of gels were observed to significantly decrease at higher ambient temperatures and as the gellant and metal particle concentrations decreased. The thixotropic behavior was found to be a strong function of the Al and B metal particle concentration for all test temperatures at shear rate ranges from 1 to 12 s−1 and 1 to 1,000 s−1. It was also a function of the MC concentration at a shear rate range of 1 to 1,000 s−1.

Rheological Characterization of Ethanolamine Gel Propellants

Ethanolamine is considered to be an environmentally friendly propellant system because it has low toxicity and is noncarcinogenic in nature. In this article, efforts are made to formulate and prepare ethanolamine gel systems, using pure agarose and hybrids of paired gelling agents (agarose + polyvinylpyrrolidine (PVP), agarose + SiO2, and PVP + SiO2), that exhibit a measurable yield stress, thixotropic behavior under shear rate ranges of 1–1,000 s−1 and a viscoelastic nature. To achieve these goals, multiple rheological experiments (including flow and dynamic studies) are performed. In this article, results are presented from experiments measuring the apparent viscosity, yield stress, thixotropy, dynamic strain, frequency sweep, and tan δ behaviors, as well as the effects of the test temperature, in the gel systems. The results show that the formulated ethanolamine gels are thixotropic in nature with yield stress between 30 and 60 Pa. The apparent viscosity of the gel decreases as the test temperature increases, and the apparent activation energy is the lowest for the ethanolamine-(PVP + SiO2) gel system. The dynamic rheology study shows that the type of gellant, choice of hybrid gelling materials and their concentration, applied frequencies, and strain all vitally affect the viscoelastic properties of the ethanolamine gel systems. In the frequency sweep experiment, the ethanolamine gels to which agarose, agarose + PVP, and agarose + SiO2 were added behave like linear frequency-dependent viscoelastic liquids, whereas the ethanolamine gel to which PVP + SiO2 was added behaves like a nearly frequency-independent viscoelastic solid. The variation in the tan δ of these gelled propellants as a function of frequency is also discussed.