Dissertation > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Burning, exploding and bursting

A Shock Tube Study of Methane Combustion Chemical Kinetics Mechanism

Author WangGaoFeng
Tutor LinQiZuo
School University of Science and Technology of China
Course Engineering Thermophysics
Keywords Shock tube Electric rupture Planar Laser Induced Fluorescence CFD simulation Shock and unsteady boundary layer interaction Chemical Kinetics Ignition delay time Low concentrations of methane Sensitivity analysis
CLC O643.2
Type PhD thesis
Year 2008
Downloads 505
Quotes 13
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How to be more environmentally friendly, safer use of energy is the main problem facing today's social development, combustion is the predominant mode of access to energy. The shock tube is an important means of combustion-related Mechanism. Established a shock tube experimental apparatus, methane, especially the ultra-low concentrations of methane burning low calorific value basis on this platform, and the flow field within the shock tube numerical simulation. First, the establishment of the shock tube experimental apparatus (including shock tube and gas distribution, pressure testing and spectrum measurement system). The same time, the development of a low-voltage high-current electric power control rupture device, shock wave timing control (control accuracy 1ms) and electromagnetic interference monitoring and control equipment, not a chemical reaction produces pollution. Was developed based the Atmega microcontroller programmable timing controller to complete Preheat the laser shock wave arrives, reaction process detection trigger diagnostic laser emission and ICCD exposure timing the overall synchronization control, and then set up based on Nd: YAG laser the PLIF measurement platform. The stream the PLIF used as shock tube experiments also show that the use of the platform of the shock compressed flow field the acetone tracer PLIF measurement, quantitative analysis of the results with theoretical calculations match, only to verify the reliability of the the electric Amniotomy way The feasibility of the field displayed. This high temporal and spatial resolution of the test means in the shock tube experiments on a successful attempt to provide new ideas and methods for shock mechanism of interaction of gases. Secondly, for a shock induced when the structure of the ratio of methane / air mixture ignition of the reaction zone a visual measurement of the digital imaging of chemiluminescence and OH-the PLIF. Different intensity shock induction, the temperature of the induction zone, a direct result of the different heat release rate of a mixture of methane / air space, thus forming a strong to ignite and weak ignite two typical structural characteristics of the reaction zone, and its chemical self-luminous characteristics, pressure characteristics and distribution of OH-PLIF measurements confirm each other, also consistent with previous experimental and computational analysis conclusions. Ignited in weak conditions, the ignition delay period of the induction zone relative to the shock propagation time is longer, resulting turbulence can not be eliminated, the pressure wave caused the disturbance was more effective reaction characteristics appear uneven sex. Different stages of weak light conditions are present distribution of OH chemiluminescence strong relative to the surrounding many hot spots: Presentation of the shape of the strong chemical reaction of the hot spots in the ignition early, and then woven into porphyritic, promote the formation of flame surface; then located unburned gas and flame surface at the junction of hotspots, accelerate the advance of the flame surface. With the enhancement of induction of shock, this heterogeneity significantly reduced, the reaction zone was in the strong ignited condition rules Detonation structure. Once again, to build a parallel of Fluent computing platform, third-order MUSCL scheme space entry, the time of the Second Order implicit, Roe-Flux difference splitting scheme, RNG k-ε model, based on the time derivative of the density method pretreatment method and double time stepping scheme in solving the two-dimensional NS equations to simulate the shock tube shock formation, promote reflection as well as shock and boundary layer interaction, interaction between shock wave and the contact surface of the entire unsteady flow process, the calculation results with previous The results are qualitatively consistent, pointed out that the key factors affecting the District of experimental conditions. Finally, in the shock tube platform, with OH * and CH * spectroscopy, the measurement of ultra-low concentration methane ignition delay time, and the detailed mechanism, classic empirical formula and a simplified mechanism, GRI-Mech 3.0 mechanism is fully applicable in the ultra-low concentrations of methane oxidation process. Found through data analysis, the apparent activation energy and the concentration of methane into the power-law relationship, the law, and get the temperature 1100 ~ 1900K, the methane ignition delay time empirical formula atmospheric conditions. Amended by the activation energy may be equally applicable to the reaction mechanism of the total package. In addition, through local and general sensitivity analysis to explore the characteristics of low concentrations of methane combustion reaction. When the methane concentration is low, the reaction with oxygen competition (as of HO 2 <=> OH O VS.H CH 4 <=> CH 3 < / sub> H 2 ) competitiveness decreased, causing the chain branching reaction is active, the ignition delay time decreases; same due to the low concentration of methane, CH 3 composite reaction 2CH < sub> 3 (M) <=> C 2 H 6 (M) the impact is weakened in determining low concentrations of methane oxidation process primitive reaction The CH 3 O <=> O CH 3 O overwhelmingly dominant.

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