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Numerical Investigations of PMC-based Micro/mini-Chemical Propulsion System

Author: ZhangGen
Tutor: ChenYiLiang
School: University of Science and Technology of China
Course: Engineering Thermophysics
Keywords: Micro/mini-chemical propulsion system propulsion performance micro-flow Knudsen number rarefaction effects micro-combustion perfectly stirred reactor porous medium super-adiabatic combustion two-temperature model modified one-temperature model Green’s function combustion wave velocity
CLC: TK16
Type: PhD thesis
Year: 2006
Downloads: 370
Quote: 9
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Abstract


To develop a micro/mini- chemical propulsion system with a low thrust and a high specific impulse, this work seeks to elucidate the underlying characteristics unique to the flow and combustion process in each micro- component of the propulsion system and investigate its whole operation cycle of combustion and propulsion analytically and numerically. Four major aspects are contained, the numerical investigation of low-velocity gaseous flow in micro-channels and supersonic cold flow in micro-nozzles, the numerical investigation of premixed gas combustion in micro-chambers, the analytical and numerical investigation of low-velocity gas filtration combustion in porous inert media, and the modeling of the operation cycle of a micro/mini- chemical propulsion system and its performance predictions. Two-dimensional and three-dimensional modeling are performed to investigate the low Mach number gaseous flows in micro-channels with variations of aspect ratios, inlet to outlet pressure ratios and out pressures by using different continuum-based slip models. Theoretical solutions based on perturbation expansions of the Navier-Stokes equations are developed under different order slip conditions. The influences of the compressibility effects, rarefaction effects, thermal creep effects, low Reynolds number effects, three-dimensional effects and different slip conditions on the computational results are discussed in detail. The validity of slip models are examined by the corresponding experiments and the DSMC method under different Knudsen numbers. Moreover, both of the Knudsen number and the Reynolds number have been identified as key parameters of micro-channel flow.Two-dimensional and three-dimensional modeling are performed to investigate the cold flows in micro Laval nozzle by using continuum-based no-slip and slip models, respectively. The validity of the continuum models has been examined by the DSMC method. The low Reynolds number effects and three-dimensional effects of the micro-nozzle flow are emphasized in this work. Moreover, the influences of nozzle geometries and operating conditions on the flow field and thrust performance are discussed. Simulations have shown that the Reynolds number is the key parameter governing the thrust performance. Extremely low thrusts can be achieved in a micro-nozzle, and the strong viscous losses can be mitigated by running at higher chamber pressures.A perfectly stirred reactor model and a comprehensive detailed chemical reaction mechanism (GRI-Mech 3.0 releases) are adopted in the zero-dimensional modeling of the premixed gas combustion in micro-chambers. The ignition and extinction characteristics of micro-combustion are analyzed with variations of fuel/oxidant mixtures and external heat loss coefficients. The critical chamber radius, critical ignition pressure and ranges of mass flow rates for stable combustion are obtained, too.The low-velocity filtration combustion of lean methane-air mixtures occurring in inert

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CLC: > Industrial Technology > Energy and Power Engineering > Thermal engineering, heat > Fuel and combustion
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