Simulations of jet fuel thermal-oxidative degradation and flow characteristics of injected jet fuel under supercritical conditions.

摘要

The purpose of this dissertation is to study thermal degradation of jet fuel and the injection of jet fuel under supercritical condition. This dissertation is organized into three main parts described below.; In the first part, computational fluid dynamics incorporating pseudo-detailed chemical kinetics with surface mechanisms are used to simulate the effects of the surface type on liquid phase thermal-oxidation. Two hydroperoxide decomposition mechanisms are used for oxidation simulations. The first hydroperoxide decomposition mechanism employs a simple catalyzed hydroperoxide decomposition reaction at surface. The second mechansim uses adsorption and decomposition/desorption of hydroperoxide to/from the surface. The results of thermal oxidation simulations were compared to the measurement of jet fuel flowing within untreated and treated surface. The effects of the surface material on thermal oxidation were simulated by adjusting the activation energy of the surface reaction. For both hydroperoxide mechanisms, simulations of dissolved O2 consumption agree reasonably well with dissolved O2 measurements.; In the second part, surface deposition mechanisms are added to the pseudodetailed chemical kinetic mechanism to simulate surface deposition from jet fuel. Three deposition mechanisms are used to simulate surface deposition under isothermal flowing condition while two surface deposition mechanisms are used under non-isothermal flowing conditions. It is shown that a deposition mechanism with simple adsorption of products resulting from autoxidation provides the most reasonable simulation of surface deposition under both isothermal and non-isothermal flows. In addition, it is concluded that pseudo-detailed chemical kinetics with a simple surface mechanism may be used to reasonably simulate surface deposition of jet fuels.; In the last part, computational fluid dynamics simulations of jet fuel injection under supercritical conditions were performed using n-decane as a surrogate fuel. The simulations and measurements (performed elsewhere) obtained from the recorded images show that n-decane is a reasonable surrogate fuel for predictions of the spreading angle and jet penetration length. Measurements and computations show that jet penetration and spreading angle are dependent on the fuel exit temperature and mass flow rate. It was also found that the numerical predictions of the jet centerline fuel mass fraction agreed well with established correlations. It was concluded that n-decane or a similar hydrocarbon surrogate fuel can be used for calculations of the heat transfer and fluid dynamics of non-reacting supercritical jet fuel which has a similar critical temperature and pressure. (Abstract shortened by UMI.)