Burning hydrogen-rich syngas fuels derived from various sources in combustion equipment is an effective pathway to enhance energy security and of significant practical implications. Emissions from the combustion of hydrogen-rich fuels have been a main concern in both academia and industry. In this study, the NO and CO emission characteristics of both laminar and turbulent counterflow premixed hydrogen-rich syngas/air flames were experimentally and numerically studied. The results showed that for both laminar and turbulent counterflow premixed flames, the peak NO mole fraction increased as the equivalence ratio increased from 0.6 to 1.0 and decreased as the strain rate increased. Compared with the laminar flames at the same bulk flow velocity, turbulent flames demonstrated a lower peak NO mole fraction but broader NO formation region. Using the analogy theorem, a one-dimensional turbulent counterflow flame model was established, and the numerical results indicated that the small-scale turbulence-induced heat and mass transport enhancements significantly affected NO emission. Considering NO formation at the same level of fuel consumption, the NO formation of the turbulent flame was significantly lower than that of the laminar flame at the same level of fuel consumption, implying that the turbulence-induced heat and mass transfer enhancement favored NOx suppression.

基于"比拟理论(analogy theory)",本文研究了小尺度湍流引发的传热传质增强作用对湍流非预混火焰熄灭极限的影响.结果表明:小尺度涡的传热传质增强作用使湍流非预混火焰层厚度增厚,火焰温度降低,火焰层内活性自由基H和OH的摩尔分数降低.化学反应时间和停留时间都随湍流强度增加而增加;但在同一湍流强度下,不同燃料浓度的非预混火焰熄灭临界达姆克勒数(Damk?hler number)近似为定值,该临界达姆克勒数随着湍流脉动速度的增加而增加.

π型锅炉"煤改气"后的低氮燃烧器易发生火炬"刷墙"和积碳问题,而旋流预混燃烧方法因火炬短、燃尽快等优势备受关注.将贫预混旋流燃烧与钝体相结合,设计带有位移钝体的贫预混旋流燃烧器,通过移动钝体位置,可改变燃烧器出口流速.使用此燃烧器研究了不同旋流数、热功率、钝体位置工况下,旋流预混火焰污染物生成特性,并利用激光颗粒成像测速技术测量燃烧器喷嘴出口处流场.研究发现,NOx生成量随旋流数增加呈先减小后增加的趋势,旋流数为0.25时,NOx生成量最低;钝体位置固定时,由于此时流速随热功率的增加而增大,导致NOx生成量随热功率的增加而降低,CO生成量随热功率的增加而增加;改变钝体位置保证出口流速不变时,NOx和CO生成量均保持较低水平,NOx生成量<12 mg/m3,CO生成量<7 mg/m3,且仅在最低热功率下有少量CO生成.通过分析流场和火焰可知,旋流数由0增至0.25时,火焰宽度增加,对周围烟气卷吸作用增强,NOx生成量降低;旋流数由0.25增至0.83时,火焰宽度基本维持不变,但轴向回流增强,热烟气停留时间增加,NOx生成量升高.因此,优化位移钝体位置和旋流数,可以使燃烧器出口流场和火焰结构更加合理,使污染物维持在较低水平.

A set of experiments were conducted at microgravity (μg) on volatile evolution and combustion for isolated bituminous coal particles using the drop tower at the National Microgravity Laboratory of China (NMLC) and the Chinese SJ-10 satellite. Counterpart experiments were conducted at normal gravity (1 g). In the same time, a one-dimensional transient ignition model considering intraparticle thermal conduction was adopted to assess the formation condition of the volatile jet flames. Experiments showed that volatile could eject in multiple jets from the coal particle and the phenomenon was remarkably more obvious at μg. The jet flames behaved as laminar diffusion flames and their length was about 0.25–1.0 mm and could be well predicted by the traditional Roper relation. The jet flame occurred when the characteristic convection time of the jet was longer than the ignition delay time of ejected volatiles. As oxygen concentration increased, volatile combustion became stronger, leading to a shorter ignition delay time. High furnace temperature was in favor to the devolatilization process, resulting in a long characteristic convection time. A diagram of volatile flame pattern was given to distinguish the formation of flames in different shapes at different furnace temperatures, oxygen concentrations, and gravity conditions. The volatile jet flame could enhance the mixing of volatile and surrounding oxygen, resulting in a shorter volatile combustion duration. However, at 1 g, the volatile jet flame, combined with buoyancy effect, extended the devolatilization process and prolonged the volatile combustion.

氢氧化铝焙烧炉常用SCR或SNCR技术降低NOx排放,但存在催化剂被污染以及氨逃逸等问题,亟待发展一条新的减排方案.烟气再循环和空气分级技术是降低氢氧化铝气态悬浮焙烧炉NOx排放的潜在手段,但烟气再循环和空气分级燃烧技术对气态悬浮焙烧炉运行参数的影响规律仍不明确.以3 000 t/d规模的氢氧化铝气态悬浮焙烧炉系统为研究对象,研究了烟气再循环和空气分级对氢氧化铝气态悬浮焙烧炉运行参数的影响规律.通过计算发现,当烟气再循环率为20％时,系统总过量空气系数降低至1.1左右,可维持较大的一次风量,保证悬浮焙烧状态的同时,使主焙烧炉(P04)下部达到欠氧还原性气氛,进而抑制NOx的生成.烟气再循环率在20％且空气分级的燃尽风率在25％以内时,GSC炉系统中各分离器效率变化可忽略.GSC炉系统增加烟气再循环和空气分级后,若不调整燃料分配,焙烧温度会降低,可能对氧化铝产品质量产生不利影响.通过优化GSC炉的燃料分配,可显著降低烟气再循环和空气分级对系统运行参数的影响程度.烟气再循环达20％且空气分级的燃尽风率在25％时,优化后的GSC炉系统仍可在保证氢氧化铝焙烧工艺温度和整体热效率的情况下,实现主焙烧炉膛下部的欠氧还原性燃烧气氛,为GSC焙烧炉的低氮燃烧设计提供了必要条件.

Based on national standard GB20071-2006 and regulation ECE R95,the complete vehicle finite element model,movable and deformable barrier finite element model,assembly space model for main on-board equipment were established in the paper.Three dangerous side-impact situations for fuel cell city bus(FCCB)were simulated by using software LS-DYNA,the acceleration impact of main on-board equipment of FCCB in side-impact were also gotten The results of simulations showed that the side-impact safety of the FCCB could be well guaranteed by adding collision prevention devices and increasing transverse strength of the underframe.