共查询到19条相似文献,搜索用时 125 毫秒
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本文联合使用计算流体软件FLUENT和采用详细化学反应机理计算空间和表面催化反应的化学动力学软件DETCHEM对甲烷空气预混气体在微通道内催化燃烧的情况进行了数值模拟.计算结果表明,在微通道内,通过导热壁的轴向间的传热,预热了入口气体,使甲烷燃烧得更加充分;空间反应同样可以发生,不再是可以被忽略的部分;而且燃料混合物的入口流速对表面催化反应有很重要的影响. 相似文献
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冉景煜^祁文杰王蕊蕊 《工程热物理学报》2014,(6):1244-1247
采用详细化学反应机理对甲烷空气预混气体在不同粗糙度下微通道内催化燃烧进行了数值模拟。结果表明:粗糙度的存在使得微通道内甲烷转化率减小,出口温度降低,粗糙表面将阻碍催化反应的进行,而且粗糙度越大这种阻碍作用越大;在同一粗糙度下,随着当量比、混合气入口速度的增加,粗糙度对催化反应的阻碍作用越明显,粗糙度越大,燃烧效率越低。 相似文献
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本文针对清洁燃料替代传统燃料,在光学发动机上,利用高速成像技术结合双色法采集了柴油掺混聚甲氧基二甲醚(PODE)-汽油反应活性控制压燃模式下的缸内燃烧特性及碳烟生成过程。试验结果表明:相同预混比下随着PODE的掺混增加,缸内压力峰值、放热率峰值、压力升高率都随之降低,着火延迟期延长,燃烧持续期增加,燃烧相位后移,燃烧趋于平缓。在预混比为50%时,直喷P20D80及P50D50的单循环燃烧总放热量分别为直喷P0D100总放热量的97.89%和95.39%,单循环碳烟生成总量分别为直喷P0D100的55.22%和36.55%,碳烟高温区域分别减少了52.9%和73.32%,碳烟平均温度的稳定值分别降低了6.65 K和20.25 K,碳烟平均KL因子的稳定值分别降低了10.35%和16.12%。相较而言P50D50作为直喷燃料既能保证较高燃烧热效率,又能有效抑制碳烟的生成。 相似文献
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柴油燃料HCCI燃烧影响因素的试验研究 总被引:4,自引:0,他引:4
本文采用在进气上止点附近进行柴油喷射,利用缸内高温残余废气促进燃油蒸发形成均质混合气,实现了柴油燃料的均质压燃(HCCI)。试验结果表明柴油燃料HCCI燃烧的放热规律呈现低温和高温放热两个阶段,并且NOx排放可以降低95%-98%。本文主要研究了影响HCCI燃烧的因素,指出负荷增大、进气温度增加和负气门重叠期的增加使HCCI着火提前,而外部EGR率的增大可以推迟着火。因此对于低温自燃性好的燃料,冷EGR是控制其HCCI着火燃烧过程的有效措施。 相似文献
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煤粒均相着火规律的研究 总被引:1,自引:0,他引:1
煤粒均相着火规律的研究张军,傅维标(清华大学工程力学系北京100084)关键词均相着火,简化模型,预报1前言煤粉颗粒既能发生均相着火,又能发生非均相着火山。对非均相着火,许多学者进行了研究,取得了很多有价值的成果。均相着火由于比较复杂,一直发展缓慢。... 相似文献
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The model that takes chemical reactions, heat and mass transfers in the boundary layer of the particle into account simultaneously, is developed for simulating the combustion of a pulverized coal particle. The FTIR in situ temperature-measurements and the comparison between numerical simulations for the pulverized coal and the devolatilized char show that the volatile flame induces the combustion of the primary product of surface oxidation CO. Due to the influence of volatile flame, the char particle can be ignited at temperature lower than its heterogeneous ignition temperature, which elucidates the physical essence of joint hetero-homogeneous ignition mode discovered by Jüntgen. 相似文献
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The hetero-/homogeneous combustion of fuel-lean ethane/air mixtures over platinum was investigated experimentally and numerically at pressures of 1–14 bar, equivalence ratios of 0.1–0.5, and surface temperatures ranging from 700 to 1300 K. Experiments were carried out in an optically accessible channel-flow reactor and included in situ 1-D Raman measurements of major gas phase species concentrations across the channel boundary layer for determining the catalytic reactivity, and planar laser induced fluorescence (LIF) of the OH radical for assessing homogeneous ignition. Numerical simulations were performed with a 2-D CFD code with detailed hetero-/homogeneous C2 kinetic mechanisms and transport. An appropriately amended heterogeneous reaction scheme has been proposed, which captured the increase of ethane catalytic reactivity with rising pressure. This scheme, when coupled to a gas-phase reaction mechanism, reproduced the combustion processes over the reactor extent whereby both heterogeneous and homogeneous reactions were significant and moreover, provided good agreement to the measured homogeneous ignition locations. The validated hetero-/homogeneous kinetic schemes were suitable for modeling the catalytic combustion of ethane at elevated pressures and temperatures relevant to either microreactors or large-scale gas turbine reactors in power generation systems. It was further shown that the pressure dependence of the ethane catalytic reactivity was substantially stronger compared to that of methane, at temperatures up to 1000 K. Implications for high-pressure catalytic combustion of natural gas were finally drawn. 相似文献
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Yohannes Ghermay John Mantzaras Rolf Bombach 《Proceedings of the Combustion Institute》2011,33(2):1827-1835
The hetero-/homogeneous combustion of fuel-lean CO/H2/O2/N2 mixtures over platinum is investigated at pressures up to 5 bar, inlet temperatures (TIN) up to 874 K, and a constant CO:H2 molar ratio of 2:1. Experiments are performed in an optically accessible channel-flow catalytic reactor and involve planar laser induced fluorescence (LIF) of the OH radical for the assessment of homogeneous (gas-phase) ignition and 1-D Raman measurements of major gas-phase species concentrations over the catalyst boundary layer for the evaluation of the heterogeneous (catalytic) processes. Simulations are carried out with an elliptic 2-D model that includes detailed heterogeneous and homogeneous chemical reaction schemes. The predictions reproduce the Raman-measured catalytic CO and H2 consumption, and it is further shown that for wall temperatures in the range 975 ? Tw ? 1165 K the heterogeneous pathways of CO and H2 are largely decoupled. However, for wall temperatures below a limiting value of 710–720 K and for the range of pressures and mixture preheats investigated, CO(s) blockage of the surface inhibits the catalytic conversion of both fuel components. The homogeneous ignition distance is well-reproduced by the model for TIN > 426 K, but it is modestly overpredicted at lower TIN. Possible reasons for these modest differences can be the values of third body efficiencies in the gas-phase reaction mechanism. The sensitivity of homogeneous ignition distance on the catalytic reactions is weak, while the H2/O2 subset of the CO/H2/O2 gaseous reaction mechanism controls the onset of homogeneous ignition. Pure hydrogen hetero-/homogeneous combustion results in flames established very close to the catalytic walls. However, in the presence of CO the gaseous combustion of hydrogen extends well-inside the channel core, thus allowing homogeneous consumption of H2 at considerably shorter reactor lengths. Finally, implications of the above findings for the design of syngas-based catalytic reactors for power generation systems are discussed. 相似文献
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单滴燃料热壁蒸发、微爆与着火的实验研究 总被引:1,自引:0,他引:1
多组分燃料在热板的蒸发与着火规律与空间相比,具有一些新的特点,特别是乳化油的贴壁燃烧现象更有重要意义。本文通过实验将多组分与单组分的燃烧情况进行了对比研究。结果表明:(1)易挥发组分的着火延迟在较低的温度条件下长于不易挥发份,在较高温度时情况相反。混合物则居于其中;(2)对于含水的乳化油,燃烧与微爆发生先后同的外界条件有关,其着火过程极为迅速。(3)乳化油中易挥发燃料含量较高,环境温度也较高时,微爆滞后很明显。 相似文献
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Marco Schultze John Mantzaras Rolf Bombach Konstantinos Boulouchos 《Proceedings of the Combustion Institute》2013,34(2):2269-2277
The hetero-/homogeneous combustion of hydrogen/air mixtures over platinum was investigated experimentally and numerically in a channel-flow configuration at fuel-rich equivalence ratios ranging from 2 to 7, pressures up to 5 bar and wall temperatures 760–1200 K. Experiments involved in situ one-dimensional Raman measurements of major gas-phase species concentrations over the catalyst boundary layer and planar laser induced fluorescence (LIF) of the OH radical, while simulations included an elliptic 2-D model with detailed heterogeneous and homogeneous reaction mechanisms. The employed reaction schemes reproduced the measured catalytic reactant consumption, the onset of homogeneous ignition, and the post-ignition flame shapes at all examined conditions. Although below a critical pressure, which depended on temperature, the intrinsic gas-phase kinetics of hydrogen dictated lower reactivity for the fuel-rich stoichiometries when compared to fuel-lean ones, homogeneous ignition was still more favorable for the rich stoichiometries due to the lower molecular transport of the deficient oxygen reactant that resulted in modest catalytic reactant consumption over the gaseous induction zone. Above the critical pressure, the intrinsic gaseous hydrogen kinetics yielded higher reactivity for the rich stoichiometries, which resulted in vigorous gaseous combustion at pressures up to 5 bar, in contrast to lean stoichiometry studies whereby homogeneous combustion was altogether suppressed above 3 bar. Computations at fuel-rich stoichiometries in practical channel geometries indicated that homogeneous combustion was not of concern for reactor thermal management, since the larger than unity Lewis number of the deficient oxygen reactant confined the flames to the core of the channel, away from the solid walls. 相似文献
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催化着火的实验研究 总被引:2,自引:0,他引:2
本文就CH4-水蒸气以及正庚烷或正十二烷-水蒸气的催化重整反应对燃料与空气预混气的着大影响进行了几种不同工况的实验研究,并与纯燃料气(CH4气、正庚烷或正十二烷蒸气)和空气的预混气的着火进行对比.实验结果表明,在催化剂的作用下,烃类燃料气和水蒸气能在200~500℃的较低温度下进行重整反应,产生部分H2和CO。少量H2的存在大大降低了预混气的着火温度。若将这种催化剂用于柴油机汽缸壁,则可望使柴油机中的乳化油在汽缸壁上生成部分H2,因此可能在掺水量加大的条件下,仍然能实现汽缸中的正常燃烧,这不仅使乳化油在柴油机中的应用成为可能,而且将显著地改善柴油机的排放性能和节能效果. 相似文献