A comprehensive analysis of hydrogen/oxygen and hydrocarbon/oxygen counterflow diffusion flames has been conducted using corresponding detailed reaction mechanisms. The hydrocarbon fuels contain n-alkanes from CH4 to ...A comprehensive analysis of hydrogen/oxygen and hydrocarbon/oxygen counterflow diffusion flames has been conducted using corresponding detailed reaction mechanisms. The hydrocarbon fuels contain n-alkanes from CH4 to C16H34. The basic diffusion flame structures are demonstrated, analyzed, and compared. The effects of pressure, and strain rate on the flame behavior and energy-release rate for each fuel are examined systematically. The detailed chemical kinetic reaction mechanisms from Lawrence Livermore National Laboratory （LLNL） are employed, and the largest one of them contains 2115 species and 8157 reversible reactions. The results indicate for all of the fuels the flame thickness and heat release rate correlate well with the square root of the pressure multiplied by the strain rate. Under the condition of any strain rate and pressure, H2 has thicker flame than hydrocarbons, while the hydrocarbons have the similar temperature and main products distributions and almost have the same flame thickness and heat release rate. The result indicates that the fuels composed with these hydrocarbons will still have the same flame properties as any pure n-alkane fuel.展开更多
This paper evaluates the utilization of the radical chemiluminesecnce imaging and tomographic reconstruction techniques to assess advanced information on reacting flows. Two different laboratory flow configurations we...This paper evaluates the utilization of the radical chemiluminesecnce imaging and tomographic reconstruction techniques to assess advanced information on reacting flows. Two different laboratory flow configurations were analyzed, including unconfined non-premixed jet flame measurements to evaluate name fuel/air mixing patterns at the burner-port of a typical glass-furnace burner. The second case characterized the reaction zone of premixed flames within gas turbine combustion chambers, based on a laboratory scale model of a lean prevaporized premixed (LPP) combustion chamber. The analysis shows that advanced imaging diagnosis can provide new information on the characterization of flame mixing and reacting phenomena. The utilization of local C2 and CH chemiluminescence can assess useful information on the quality of the combustion process, which can be used to improve the design of practical combustors.展开更多
Based on premixed flame, the theoretical model of transport properties with temperature variation was established inside a preheated zone. Lewis number of the deficient-to- stoichiometric hydrocarbon/air mixture has b...Based on premixed flame, the theoretical model of transport properties with temperature variation was established inside a preheated zone. Lewis number of the deficient-to- stoichiometric hydrocarbon/air mixture has been theoretically predicted over a wide range of preheated temperature. These predictions are compared with the experimental data on disport properties that exist in the literature. The response of the burning velocity to flame stretch can be parameterized by the laminar flame speed and Markstein length. Therefore, if the laminar flame speed and Markstein number could be accurately simulated by using an analytic expression of characterized temperature, equivalence ratio, and Lewis number, the results are applicable to the prediction of methane, acetylene, ethylene, ethane, and propane flames. Expanding previous studies on the extinction of premixed flames under the influence of stretch and incomplete reaction, the results were further classified and rescaled. Finally, it could be inferred that parameter Pq, the rescaled extinction Karlovitz number could be used to explain the degree or flame quench.展开更多
文摘A comprehensive analysis of hydrogen/oxygen and hydrocarbon/oxygen counterflow diffusion flames has been conducted using corresponding detailed reaction mechanisms. The hydrocarbon fuels contain n-alkanes from CH4 to C16H34. The basic diffusion flame structures are demonstrated, analyzed, and compared. The effects of pressure, and strain rate on the flame behavior and energy-release rate for each fuel are examined systematically. The detailed chemical kinetic reaction mechanisms from Lawrence Livermore National Laboratory （LLNL） are employed, and the largest one of them contains 2115 species and 8157 reversible reactions. The results indicate for all of the fuels the flame thickness and heat release rate correlate well with the square root of the pressure multiplied by the strain rate. Under the condition of any strain rate and pressure, H2 has thicker flame than hydrocarbons, while the hydrocarbons have the similar temperature and main products distributions and almost have the same flame thickness and heat release rate. The result indicates that the fuels composed with these hydrocarbons will still have the same flame properties as any pure n-alkane fuel.
文摘This paper evaluates the utilization of the radical chemiluminesecnce imaging and tomographic reconstruction techniques to assess advanced information on reacting flows. Two different laboratory flow configurations were analyzed, including unconfined non-premixed jet flame measurements to evaluate name fuel/air mixing patterns at the burner-port of a typical glass-furnace burner. The second case characterized the reaction zone of premixed flames within gas turbine combustion chambers, based on a laboratory scale model of a lean prevaporized premixed (LPP) combustion chamber. The analysis shows that advanced imaging diagnosis can provide new information on the characterization of flame mixing and reacting phenomena. The utilization of local C2 and CH chemiluminescence can assess useful information on the quality of the combustion process, which can be used to improve the design of practical combustors.
文摘Based on premixed flame, the theoretical model of transport properties with temperature variation was established inside a preheated zone. Lewis number of the deficient-to- stoichiometric hydrocarbon/air mixture has been theoretically predicted over a wide range of preheated temperature. These predictions are compared with the experimental data on disport properties that exist in the literature. The response of the burning velocity to flame stretch can be parameterized by the laminar flame speed and Markstein length. Therefore, if the laminar flame speed and Markstein number could be accurately simulated by using an analytic expression of characterized temperature, equivalence ratio, and Lewis number, the results are applicable to the prediction of methane, acetylene, ethylene, ethane, and propane flames. Expanding previous studies on the extinction of premixed flames under the influence of stretch and incomplete reaction, the results were further classified and rescaled. Finally, it could be inferred that parameter Pq, the rescaled extinction Karlovitz number could be used to explain the degree or flame quench.
