共查询到18条相似文献,搜索用时 125 毫秒
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高温空气燃烧炉内湍流混合特性的数值研究 总被引:2,自引:0,他引:2
应用自行研发的三维流动、燃烧、传热和污染物NOx湍流生成的数值模拟程序,对高温空气燃烧实验模型炉进行了湍流扩散燃烧混合特性的数值模拟.数值预报了燃烧室内气体燃料和空气的混合物分数及其湍流脉动的三维分布.数值研究结果表明:在一定的几何条件和气体动力学条件下,高温空气燃烧的湍流混合在更广泛的区域内以较小梯度的进行;混合物分数的脉动主要分布在燃烧区,这表明高温空气燃烧的火焰厚度更大,具有燃烧释热更趋均匀的特性.数值模拟结果与相关的实验结果有相同的规律. 相似文献
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煤粉炉内弥散介质辐射传热的综合模拟 总被引:3,自引:0,他引:3
本文基于辐射传热计算的DT法和颗粒运动计算的随机轨道法,并结合单颗粒的辐射特性模型,构造了能够详细考虑颗粒燃尽、湍流弥散诸因素对炉内空间局部辐射特性及总体辐射传热影响的弥散介质辐射传热计算模型,并将其耦合到炉内过程的总体数值模型中。采用该程序,比较计算了几种颗粒辐射特性模型对某300MW锅炉炉内温度场的预报结果,结果表明:通常采用的均匀颗粒辐射特性模型会导致温度场的极大误差;由于炉内颗粒浓度的不均匀分布,炉内的温度分布呈现高度非均匀状态,在炉膛轴线上有大面积的高温烟气区存在;考虑残炭存在时,温度分布的不均匀性更显著. 相似文献
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以国内首台3 MW_(th)富氧燃烧煤粉锅炉为研究对象,借助CFD软件对煤粉空气燃烧和富氧燃烧工况进行数值模拟研究。通过与实验结果对比发现,模拟得到的炉膛温度分布、换热量以及出口组分与实验测量结果吻合,这表明本文使用改进的辐射特性模型以及4步化学反应机理能够很好地预测炉内温度、传热以及烟气组分分布。通过模拟研究,对比分析了空气燃烧与富氧燃烧的炉内特性。研究结果表明:富氧燃烧时,CO_2的显著增加使得燃烧器区域出现高浓度CO;富氧燃烧的整体温度分布与空气燃烧相似,但峰值温度有较大的降低;炉内辐射传热较空气燃烧略有下降。 相似文献
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燃烧室出口辐射对气膜冷却传热影响研究 总被引:2,自引:0,他引:2
燃气轮机高温透平中包含对流/导热/辐射等复杂传热现象。本文依托高温流热固耦合实验台,提出燃烧室与透平联合计算的方法,采用数值模拟和实验对比的方式分析了平板气膜冷却的对流/导热/辐射传热特性。同时研究了不同燃气吸收系数以及不同进口辐射条件对于平板气膜冷却的表面温度分布的影响。结果表明:辐射传热是燃气轮机首级高温叶片传热特性的重要影响因素,辐射传热使得实验平板温度抬升50~70 K,燃烧室/透平联合计算方法有效地分析了燃烧室出口辐射强度对高温平板气膜冷却辐射传热的影响;高温燃气辐射特性对于平板温度分布具有明显影响。 相似文献
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碳遮光石英气凝胶传热机制与热性能数值模拟 总被引:1,自引:0,他引:1
建立了碳遮光石英气凝胶传热机制及热性能数值模拟方法,在交叉立方阵列导热模型、热辐射传输谱带模型、辐射导热耦合传热模型基础上,采用蒙特卡罗方法与有限体积法数值模拟了气凝胶内的热辐射传输及辐射导热耦合传热,并以表观导热系数描述气凝胶传热性能.以某石英气凝胶为例,定量模拟了热性能、各种传热方式的作用及温度依赖性,分析了应用Rosseland扩散近似引起的误差. 相似文献
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采用数值计算对水对流换热边界下天然气燃烧及外部对流传热特性进行了研究。研究了相同燃烧功率不同水入口流速下燃烧及传热特性,得到各个区域交界面温度分布及燃烧室内辐射换热与对流换热占总换热量比例。对天然气高温空气燃烧技术在工业锅炉等设备上的应用具有很好的指导意义。 相似文献
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为了考察湍流燃烧过程中的辐射热影响,数值模拟了Sanida火焰D,其中湍流流动采用多时间尺度(MTS)k-ε湍流模型模拟,燃烧过程采用概率密度函数(PDF)方法和拉格朗日火焰面模型(LFM)以及详细化学反应机理GRI3.0联合的方法模拟,辐射换热采用有限体积(FVM)联合关联k分布模型模拟。计算结果和实验数据的比较发现虽然相对于燃烧热,辐射热是一个小量,但是考虑了辐射热影响以后,模拟结果大有改进。针对该现象,我们给出的解释是由于在湍流燃烧过程中,湍流过程,燃烧过程以及辐射换热过程三者是强耦合的,湍流作用很可能会将辐射换热作用放大,因此,对于燃烧过程的详细数值模拟,建议考虑辐射换热的影响。 相似文献
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高温空气低燃气浓度燃烧过程的数值模拟研究 总被引:2,自引:1,他引:1
从工程实际出发,本文提出了高温空气低燃气浓度燃烧新技术,即充分利用烟气余热提高助燃空气温度,提高热能利用率;同时通过优化喷口结构,提高燃气射流速度,使燃气射流在同空气射流混合燃烧前卷吸大量炉内烟气,从而降低燃气射流中的可燃物浓度,进而降低氮氧化物的排放。通过数值模拟研究表明,通过燃气射流速度从24.56m/s提高到55.26m/s,可以降低NOx的排放;当围绕燃气喷口的六个圆形空气喷口改为两个矩形喷口时,燃气射流可从两侧卷吸更多的炉内烟气,形成低燃气浓度燃烧,从而大大降低了NOx的排放。 相似文献
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Kenji Yamamoto Tomoya Murota Teruyuki Okazaki Masayuki Taniguchi 《Proceedings of the Combustion Institute》2011,33(2):1771-1778
Large eddy simulation (LES) is applied to a pulverized coal jet flame ignited by a preheated gas flow. The simulation results are compared to experimental data obtained for the inlet stoichiometric ratios of 0.14, 0.22, and 0.36. An accurate and computationally inexpensive devolatilization model suitable for combustion simulation in LES is proposed and incorporated into the LES. The numerical results of gas temperature and coal burnout on the centerline show good agreement with the experimental data. Two kinds of lift-off heights are introduced to verify the combustion simulation. One is the height from the primary nozzle exit to the starting point of the growing flame region. The other is the height from the primary nozzle exit to the starting point of the continuous flame region. The calculated results of the two lift-off heights show good agreement with the experimental data. In contrast to LES, the standard k–ε model overestimates the lift-off heights because it calculates time-averaged temperature which does not contain information about local flame structure. The stoichiometric ratio in the gas phase at the starting point of the growing flame region is found to be independent of the inlet stoichiometric ratio in the range from 0.14 to 0.36. 相似文献
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A novel simulation theory and model system for multi-field coupling pipe-flow system 总被引:1,自引:0,他引:1
Due to the lack of a theoretical basis for multi-field coupling in many system-level models, a novel set of system-level basic equations for flow/heat transfer/combustion coupling is put forward. Then a finite volume model of quasi-1D transient flow field for multi-species compressible variable-cross-section pipe flow is established by discretising the basic equations on spatially staggered grids. Combining with the 2D axisymmetric model for pipe-wall temperature field and specific chemical reaction mechanisms, a finite volume model system is established; a set of specific calculation methods suitable for multi-field coupling system-level research is structured for various parameters in this model; specific modularisation simulation models can be further derived in accordance with specific structures of various typical components in a liquid propulsion system. This novel system can also be used to derive two sub-systems: a flow/heat transfer two-field coupling pipe-flow model system without chemical reaction and species diffusion; and a chemical equilibrium thermodynamic calculation-based multi-field coupling system. The applicability and accuracy of two sub-systems have been verified through a series of dynamic modelling and simulations in earlier studies. The validity of this system is verified in an air–hydrogen combustion sample system. The basic equations and the model system provide a unified universal theory and numerical system for modelling and simulation and even virtual testing of various pipeline systems. 相似文献
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《Revue Generale de Thermique》1998,37(9):818-826
The thermal behaviour of a solid sorption generator of active carbon/alcohol machine, is studied during heating and cooling phases with a preheated air flow. A bicylindrical walls generator that contains 0.9 kg of a granular adsorbent in the presence of residual gas is tested during a cycle of an average duration of 3 hours; the grains of active carbon are rod-shaped of 0.003 m diameter and 0.008 m average length. The thermal contact conductance of adsorbent to the wall has an important influence on the rate of heat transfer between the generator and the external source of heat. In the absence of alcohol, heat transfer occuring without mass transfer in active carbon is essentially due to the conduction. A numerical bidimensional model allows one to justify experimentally the observed evolution and proposes thermal contact conductance between active carbon pellets and the generator wall. A parametric study of the thermal contact conductance gives 6.5 W·m−2·K−1 as the best value. A simulation of heating and cooling phases with average conductance values between 5 and 30 W·m−2·K−1 gives model estimated heating and cooling phases duration. 相似文献