Alkali Metal Spectroscopy for High-speed Imaging of Burned Gas Temperature, Equivalence Ratio and Mass Fraction Burned in Internal Combustion Engines.

Spectroscopy;Combustion;Internal Combustion Engine;Sodium and Alkali Fluorescence;Temperature;Equivalence Ratio;Mechanical Engineering;Engineering;Mechanical Engineering

Mosburger, Michael J.Borgnakke, Claus ;

University of Michigan

关键词: Spectroscopy;    Combustion;    Internal Combustion Engine;    Sodium and Alkali Fluorescence;    Temperature;    Equivalence Ratio;    Mechanical Engineering;    Engineering;    Mechanical Engineering;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/97841/mosb_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Alkali metal atoms show an intense natural fluorescence in the burned gas region of internal combustion engines. This fluorescence offers great opportunity for spectroscopic combustion analysis in internal combustion engines without the requirement of laser excitation or image intensifiers. To quantify this fluorescence intensity, spectroscopic and thermodynamic properties of the alkali metals lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs) and their oxidation products and ions were analyzed. Collisional energy transfer and reabsorption effects (including temperature- and pressure dependent lineshapes) were calculated over the range of engine environments. Three compounds containing Li, Na and K, respectively, were selected as fuel additives for engine experiments. The experiments were conducted on an optical, single cylinder, spark-ignition, direct-injection research engine, and the fluorescence of the three alkali components was recorded simultaneously using three CMOS high-speed cameras. The two-component fluorescence intensity ratios (Na/K, Li/K and Na/Li) are shown to depend on temperature, pressure and equivalence ratio. However, the three-component ratio Na•Li/K2 is nearly independent of pressure and equivalence ratio in the tested range of operating conditions and can serve as a direct marker for burned gas temperature. Subsequently, equivalence ratio can be determined from any of the bi-component fluorescence ratios. The spatially integrated fluorescence intensity of the single components is a function of burned gas temperature, cylinder pressure, equivalence ratio and mass fraction of burned fuel. When temperature and equivalence ratio are determined from the fluorescence intensity ratios, the spatially integrated fluorescence signal of sodium can serve as a marker for the mass fraction of burned fuel.The tool was applied to various cases of direct injected, stratified engine combustion to illustrate the potential of this technique for optimization of the combustion strategy and engine hardware configuration.