Premixed jet flame characteristics of syngas using OH planar laser induced fluorescence

Abstract

Lean premixed flame characteristics of several typical low calorific value (LCV) syngases (basis CO/H 2 /CH 4 /CO 2 /N 2 ), including bituminous coal, wood residue, corn core, and wheat straw gasification syngas, were investigated using OH planar laser induced fluorescence (PLIF) technology. OH radical distributions within the turbulent flame were measured for different turbulence intensities. Flame structures of syngases were analyzed and characterized with respect to burnt and unburnt regions, flame curvature (sharp cusp), local extinction (holes and penetration), OH reaction layer thickness, wrinkling, and other features, with OH-PLIF instantaneous images and statistical analysis. Results show that H 2 content, LCV, and turbulence intensity are the most effective factors influencing the OH radical intensity and thickness of OH radical layers. The bituminous coal gasification syngas with relatively higher LCV and H 2 content tends to burn out easily. Through changes in thickness of the OH radical layers and signal intensities, the reaction layer can be compressed by intensifying turbulence and thereby the combustion processes of syngas. The integrated gasification combined cycle is one of the more-promising clean and efficient electricity generation technologies at present for coal utilization. Coal is partially oxidized to provide the needed heat for the endothermic gasification at a relatively high temperature and pressure, and the residue is translated into syngas fuel in the gasifier. The syngas, consisting mainly of CO, H 2 , CH 4 , is burned in a gas turbine to generate electricity after purification. The downstream waste-heat-recovery steam-turbine system further improves the overall energy conversion efficiency, which is much higher than a direct coal-combustion steam-turbine system [1]. As a kind of renewable and carbon-neutral fuel, biomass has attracted much more attention world-wide recently. Combustion, gasification, and liquefaction are the most popular utilization methods for biomass [2].Syngas, derived from coal and biomass gasification, is considered to be a more attractive fuel for further energy conversion and utilization. However, the LCV of syngas is usually much lower than for natural gas because of the dilution of N 2 and CO 2 . Efficient utilization of LCV syngas not only can enhance energy utilization efficiency but also can reduce toxic emissions, such as CO 2 , compared with just coal combustion. Coal and biomass can be used more cleanly and efficiently through gasification, which is of great significance both for environment, economic and energy security [3]. The combustion and flame stability of syngas, though, will be a big problem because of the variation of gas composition derived from the operation parameters of gasifier. The characteristics of syngas are always determined by different kinds of gasification fuels, such as the type of coal and biomass, gasification oxidizer such as steam, air, and pure oxygen. Therefore, it is necessary to investigate the

Investigation of Dilution Effect on CH4/Air Premixed Turbulent Flame Using OH and CH2O Planar Laser-Induced Fluorescence

“…CH 2 O was generated in the middle of the flame during the preheating stage which was earlier than OH. In the flame front zone, OH was generated and the distribution of OH shows the conjunction between burnt and unburned regions, thought as an indicator of flame region [36]. In all cases, OH signal shows relatively stronger as close to the flame front, especially in wrinkle pockets and flame tip zone.…”

Effects of the Equivalence Ratio and Reynolds Number on Turbulence and Flame Front Interactions by Direct Numerical Simulation

“…Reasonable characterization of syngas premixed combustion was obtained by combining the information garnered in simulation, planar laser-induced fluorescence (PLIF) measurements, and associated statistical analysis. The flame length 25 and the OH mass fraction 26 were frequently used to characterize the behavior of the flame front in the experiment, and correlation analysis of the simulation statistics was studied.…”