Ph.D Thesis | |

Ph.D Student | Chernov Victor |
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Subject | Rheological Properties of Metalized Gel Fuels |

Department | Department of Aerospace Engineering |

Supervisor | PROF. Benveniste Natan |

Full Thesis text |

Suspensions are widely used in many industrial processes and applications. Food, beauty, chemical and other industries all use suspensions of solid particles in fluids. Recently, they are considered also as advanced fuel for aerospace propulsion. A suspension of metal powders in a gelled, shear-thinning fuel may increase both the safety and the performance of liquid fuel motors.

When particles are added to a non-Newtonian fluid, a complex, two phase flow is obtained. Its properties are different than the properties of Newtonian suspension or of a simple, one-phase fluid. This may influence the required pressures, particle concentration profiles, particle deposition in pipes and other parameters. Therefore, it is important to evaluate the properties of suspension fluid after particles are added and to analyze the effect of this addition on the system.

The present research analyzes the change in the rheological parameters of a non-Newtonian, Power-Law fluid when particles are added. First, a model for the change of the rheological properties of a near-Newtonian dilute suspension of infinite cylinders (2-D flow) is proposed. Secondly, a way to solve non-Newtonian flow is suggested. Finally, a model for the change of the rheological properties of a non-Newtonian, non-dilute suspension of spheres is developed. The non-Newtonian flow solution method was tested for a simple case of uniform flow around a sphere.

The results show that when particles are added to the fluid, the resulting suspension is more shear-thinning then the pure fluid. This is true for every concentration and for every pure fluid; moreover, a dilute suspension of round particles in a Newtonian fluid produces a slightly shear-thinning suspension. Although experimental data in the literature are scarce, the existing information verifies the trends shown in the present research. It appears that the present theory over-estimates the shear-thinning behavior of suspensions quantitatively, but is correct qualitatively. It was shown that the solution method is valid for many different power indexes and provides a robust method of solving many kinds of non-Newtonian flow. Drag coefficients and flow profiles were found for a wide range of power indexes of the fluid.