Abstract
Gelled fuels combine the main advantages of liquid fuels (throttle ability) and solid fuels (easy handling, etc.) due to their non-Newtonian characteristics. In this paper, we study the flow characteristics of water-hydroxypropylcellulose (HPC) gel in converging tubes and tapered injectors which mimic the flow and injection of kerosene gel in typical geometries of propulsion systems. The water-HPC gel is modeled as a non-linear fluid, where the shear viscosity is assumed to depend on the local shear rate and modeled by the Carreau–Yasuda model; the model parameters are fitted with our experimental measurements done by a rotational rheometer. The numerical simulations indicate that for the converging tubes, increasing the convergence angle, causes the mean apparent viscosity at tube exit to decrease while the mass flow rate reduces at a constant pressure drop. Therefore, there is a balance between the lowering of the pressure loss and reducing mean apparent viscosity. In the tapered injectors, the straight pipe after the converging part has a detrimental effect on the viscosity reduction.
Highlights
Gels are complex materials showing both solid-like and liquid-like behavior [1,2]
Chernov and Natan [27] analyzed the effect of particles on the viscosity of a power-law gel; they found that with the addition of particles the fluid becomes more shear-thinning, which is advantageous for propulsion applications
We studied the flow characteristics of gel in converging tubes and tapered injectors which are typical geometries in propulsion systems for propellant transport and spray
Summary
Gels are complex materials showing both solid-like and liquid-like behavior [1,2]. From the perspective of fluid mechanics, gels are non-Newtonian fluids, which usually show yield stress, a shear-thinning viscosity and thixotropy [2]. The shear-thinning (the decreasing of the shear viscosity with an increase in shear rate) is a rheological property occurring in various fluids, such as gels, mud, butter, blood and so on [15,16,17]. Chernov and Natan [27] analyzed the effect of particles on the viscosity of a power-law gel; they found that with the addition of particles the fluid becomes more shear-thinning, which is advantageous for propulsion applications. Yoon et al [28] developed a new thixotropic model to consider the hysteresis effect for flow of gelled fluid. The viscosity of the water-HPC gel is measured by a rotational rheometer to determine the values of the rheological parameters to be used in our mathematical modal.
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