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51.
52.
The paper aims at revealing the effect of blockage ratio (BR) on the flame acceleration process and the flame-vortex mechanism in an obstructed chamber based essentially on the experimental and numerical methods. In the experiments, high-speed video photography and pressure transducer are used to study the flame shape changes and pressure dynamics. In the numerical simulations, large eddy simulation (LES) with the flame surface density (FSD) model is applied to investigate the interaction between the moving flame and vortices induced by obstacle. The results demonstrate that the flame propagation process can be divided into four stages, namely spherical flame, finger-shaped flame, jet flame and volute flame for three obstacle BR configurations, and a small recirculation zone is observed above the obstacle only for BR = 0.5. The peak of flame tip speed and pressure growth rate increases with the blockage ratio. The generation and evolution of the vortex behind the obstacle can be attributed to the initial flame acceleration, while the subsequent flame deceleration is due to the flame-vortex interaction. In addition, the transition from a “thin reaction zones” to a “broken reaction zones” is also observed in the simulation. 相似文献
53.
Rangaraj Ganesh Michel Torrijos Philippe Sousbie Aurelien Lugardon Jean Philippe Steyer Jean Philippe Delgenes 《Waste management (New York, N.Y.)》2014,34(5):875-885
Single-phase and two-phase digestion of fruit and vegetable waste were studied to compare reactor start-up, reactor stability and performance (methane yield, volatile solids reduction and energy yield). The single-phase reactor (SPR) was a conventional reactor operated at a low loading rate (maximum of 3.5 kg VS/m3 d), while the two-phase system consisted of an acidification reactor (TPAR) and a methanogenic reactor (TPMR). The TPAR was inoculated with methanogenic sludge similar to the SPR, but was operated with step-wise increase in the loading rate and with total recirculation of reactor solids to convert it into acidification sludge. Before each feeding, part of the sludge from TPAR was centrifuged, the centrifuge liquid (solubilized products) was fed to the TPMR and centrifuged solids were recycled back to the reactor. Single-phase digestion produced a methane yield of 0.45 m3 CH4/kg VS fed and VS removal of 83%. The TPAR shifted to acidification mode at an OLR of 10.0 kg VS/m3 d and then achieved stable performance at 7.0 kg VS/m3 d and pH 5.5–6.2, with very high substrate solubilization rate and a methane yield of 0.30 m3 CH4/kg COD fed. The two-phase process was capable of high VS reduction, but material and energy balance showed that the single-phase process was superior in terms of volumetric methane production and energy yield by 33%. The lower energy yield of the two-phase system was due to the loss of energy during hydrolysis in the TPAR and the deficit in methane production in the TPMR attributed to COD loss due to biomass synthesis and adsorption of hard COD onto the flocs. These results including the complicated operational procedure of the two-phase process and the economic factors suggested that the single-phase process could be the preferred system for FVW. 相似文献
54.
徐海英 《环境污染治理技术与设备》2005,6(10):80-83
针对彩管行业含铬废水处理工艺存在的不足,分别从还原剂和混凝剂两方面进行改进.通过比较和分析,最终提出了采用FeSO4作为还原剂处理含铬废水,氧化还原反应pH调节范围扩大,运行安全系数提高;利用新型高效混凝剂配合泥回流工艺,化学药品用量大幅下降,出水COD和SS含量显著减少. 相似文献
55.
渗滤液回灌频率对生物反应器填埋场的影响研究 总被引:1,自引:0,他引:1
通过模拟实验研究了渗滤液回灌周期为1、2、3和5 d的4个模拟垃圾柱的产甲烷过程和渗滤液水质的变化情况.在用NaOH调节回灌渗滤液pH值的前提下,回灌频率越高,模拟厌氧型生物反应器填埋垃圾柱先开始产甲烷,但当回灌周期低于3 d时,开始产甲烷的时间相差不多.从渗滤液水质看,回灌周期为3 d的垃圾柱渗滤液COD、VFA等有机污染物浓度下降最快.综合考虑启动时间、运行费用和填埋场的稳定进程,在厌氧型生物反应器填埋场中,实施3 d/次的渗滤液回灌频率最为合适. 相似文献
56.
57.
为研究废气再循环(EGR)对煤液化柴油颗粒粒径分布,微观形貌,组成元素以及氧化特性的影响,运用扫描电镜(SEM),透射电镜(TEM)和热重试验的方法,通过改变EGR率(0% EGR,15% EGR)和废气组分(15% N2,15% CO2和30% CO2)采集了柴油机燃用煤液化柴油的颗粒,分析了颗粒微观结构和氧化特性.结果表明,EGR率小于15%时,颗粒粒径呈单峰正态分布.在0% EGR,15% EGR,15% N2,15% CO2氛围下,颗粒粒径分布的峰值粒径分别为60.4,60.4,69.8,52.3nm.引入30% CO2时,颗粒粒径呈双峰正态分布,粒径分别在14.3nm和52.3nm.引入EGR和N2后,颗粒群变得紧凑,不易氧化.引入CO2后,颗粒群变得疏松,易于氧化.不采用EGR,颗粒结构主要呈链状,引入15% EGR和15% N2,颗粒结构主要呈团簇状. 相似文献
58.
Transport and Diffusion of Ozone in the Nocturnal and Morning Planetary Boundary Layer of the Phoenix Valley 总被引:2,自引:0,他引:2
Lee Sang-Mi Fernando Harindra J.S. Princevac Marko Zajic Dragan Sinesi Michela McCulley Jennifer L. Anderson James 《Environmental Fluid Mechanics》2003,3(4):331-362
The evolution of ozone (O
3) in the nocturnal and morning-transitional planetary boundary layer (PBL) of the Phoenix valley was measured as a part of the `Phoenix Sunrise Experiment 2001' of the U.S. Department of Energy conducted in June 2001. The goal of the field program was to study the transport, distribution and storage of ozone and its precursors in the urban boundary layer over a diurnal cycle. The ground level O
3 as well as mean meteorological variables and turbulence were measured over the entire period, and vertical profiling (using a tethered balloon) was made during the morning transition period. Approximately half of the observational days showed the usual diurnal cycle of high O
3 during the day and low O
3 at night, with nitrogen oxides (NO
x = NO
2 + NO) showing an out of phase relationship with O
3. The rest of the days were signified by an anomalous increase of O
3 in the late evening ( 2200 LST), concomitant with a sudden drop of temperature, an enhancement of wind speed and Reynolds stresses, a positive heat flux and a change of wind direction. NO
x measurements indicated the simultaneous arrival of an `aged' air mass, which was corroborated by the wind predictions of a mesoscale numerical model. In all, the results indicate that the recirculation of O
3 rich air masses is responsible for the said high-O
3 events. Such air masses are produced during the transport of O
3 precursors by the upslope flow toward mountainous suburbs during the day, and they return back to the city at night via downslope winds (i.e. mountain breeze). The corresponding flow patterns, and hence the high-O
3 events, are determined by background meteorological conditions. The vertical profiling of O
3 and flow variables during the morning transition points to a myriad of transport, mixing and chemical processes that determine the fate of tropospheric O
3. How well such processes are incorporated and resolved in predictive O
3 models should determine the accuracy of their predictions. 相似文献
59.
60.
在一台缸内直喷(GDI)汽油机上,分别用玻璃纤维滤膜和“聚氨基甲酸乙酯泡沫(PUF)+XAD-2”对尾气中的颗粒相和气相多环芳烃(PAHs)进行了采集,并用色谱-质谱联用仪(GC-MS)对PAHs进行了定性定量分析,研究了点火时刻和废气再循环(EGR)对PAHs排放的影响.结果表明:在缸内直喷汽油机尾气中,气相PAHs浓度远高于颗粒相PAHs浓度,在气相PAHs中主要是2环和3环等小环PAHs,而在颗粒相PAHs中则主要是4环及以上的大环PAHs.随着点火时刻的提前,尾气中PAHs总浓度呈现先减小后增加再减小的变化趋势,气相和颗粒相PAHs浓度也呈现相似的变化趋势.随着EGR率的增大,气相PAHs所占比例先减小后增大,颗粒相PAHs所占比例则先增大后减小,总PAHs的排放在整体上呈现逐渐减小的变化趋势.加入EGR后,GDI汽油机尾气的毒性显著增大. 相似文献