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ABSTRACT
The solid fuel ramjet is one of the simplest air-breathing engines, characterized by increased specific impulse. This study focuses on a parametric investigation of the internal ballistics of a boron-containing solid fuel ramjet. A 2-D axisymmetric model of a ramjet combustor flying at Mach 2.5 was developed and solved numerically utilizing a commercial computational fluid dynamics code modified to address the specific issues of the problem. The simulation results were compared to the theoretical performance calculated by the chemical equilibrium code. The solid fuel regression rate was found to depend on the port diameter and thus decreases with time. Thrust regulation of ramjet engine was demonstrated using bypass air. The specific impulse was found to decrease with boron content, probably because of low combustion efficiency caused by either insufficient oxygen supply or short residence time of the boron particles.
KEYWORDS:
Nomenclature
| A | = | reaction constant or constant |
| B | = | Spalding number or constant |
| BR | = | bypass ratio |
| CD | = | drag coefficient |
| Cp | = | specific heat |
| d, dp | = | diameter, port diameter |
| D | = | diffusion coefficient |
| E | = | energy |
| Ea | = | activation energy |
| fM | = | molten boron mass fraction |
| F | = | force |
| h, h0 | = | enthalpy or cell size, enthalpy of formation |
| Isp | = | specific impulse |
| J | = | mass flux |
| k | = | thermal conductivity |
| LV | = | latent heat of vaporization |
| M | = | molar mass |
| Nu | = | Nusselt number |
| p | = | pressure |
| r | = | radial coordinate |
| RB | = | molar rate of boron consumption |
| RE | = | molar evaporation rate of boric oxide |
| RH | = | molar rate of oxide removal by water |
| R, Ru | = | specific gas constant, universal gas constant |
| Re | = | Reynolds number |
| Sh | = | enthalpy source |
| Sh,chem | = | enthalpy source due chemical reaction |
| Sm | = | mass source |
| Su | = | axial momentum source |
| Sv | = | radial momentum source |
| Sc | = | Schmidt number |
| T | = | temperature |
| u | = | axial velocity |
| v | = | radial velocity |
| x | = | axial coordinate |
| Xi | = | molar fraction of species i |
| Yi | = | mass fraction of species i |
| δ | = | boron oxide layer thickness |
| η | = | boron combustion efficiency |
| μ | = | viscosity |
| ν | = | stoichiometric coefficient |
| ρ | = | density |
Subscripts
| i | = | species index |
| l | = | laminar or liquid |
| p | = | particle |
| s | = | surface |
| t | = | turbulent |