旋流燃烧器出口湍流流场的数值模拟

对旋流燃烧器出口的湍流流场进行了深入的数值模拟研究，经过对不同旋流强度的旋转射流的计算，比较了对目前应用较多的k-ε模型、重正化群(RNG)的k-ε模型及雷诺应力模型在实际求解中的优劣。在弱旋气相流动时，RNG k-ε模型可以满足工程上的精度需求。在强旋流动中，基于“有效粘性”的各个模型的计算结果和实验相差很远，只有采用雷诺应力模型才能得到较为满意的结果。图4表3参5     

钝体燃烧器湍流预混燃烧的数值模拟

采用湍流火焰封闭燃烧模型(TFC)模拟了钝体燃烧器的湍流预混燃烧,比较了基于火焰褶皱率和湍流燃烧速度2种源项解法对钝体预混燃烧的预测,对3个不同湍流燃烧速度表达式模拟的性能进行了比较,采用粒子成像测速技术(PIV)测量了燃烧器中心射流出口的速度分布,并将其作为边界条件代入计算.结果表明:不同湍流燃烧速度公式的计算结果在火焰刷厚度、位置及火焰前锋位置方面存在较大差别;Gulder公式的计算结果最接近试验数据,火焰刷厚度与试验结果吻合较好,但火焰刷位置与试验结果差别较大;Dinkelacker的火焰褶皱率模型主要模拟燃烧器在高压条件下的燃烧,在运行压力接近标准大气压的情况下,计算结果与试验值存在较大误差.     

微燃烧器内甲烷催化燃烧的数值模拟

联合使用CFD软件、FLUENT和化学反应动力学软件DETCHEM对甲烷—空气混合物在有逆流换热的微燃烧器内的催化燃烧进行了数值模拟。计算中只考虑了甲烷在催化表面上的反应。燃料一空气混合物的当量比为0．4,燃烧器外壁面分剐采用等温边界条件和与环境的对流换热边界条件,并比较了这两种边界条件对可燃混合气燃烧的影响。计算结果表明,催化燃烧可以实现常规方法无法实现的甲烷低温、高效转变。     

燃烧器燃烧流场与污染物排放的数值模拟

针对一种新型燃烧器,利用FLUENT软件,对其内部三维燃烧流场进行了数值模拟.计算采用RNGk-ε双方程湍流模型、PDF燃烧模型以及离散坐标辐射传热模型,液体燃料采用颗粒群轨道模型,模拟了不同过量空气系数和不同负荷工况下的燃烧流场,并对NOx排放进行了预测.根据所得到的模拟结果分析了影响燃烧的因素,为此新型燃烧器的研制提供了理论指导.     

带钝体的旋流燃烧器出口气相流场数值模拟

应用重整化群k-ε模型和雷诺应力模型,在弱旋和强旋两种状态下,对带钝体的旋流燃烧器进行了冷态气相数值计算,弱旋流动以重整化群k-ε模型计算结果为参考,强旋流动以雷诺应力模型计算结果为参考,对比了燃烧器出口轴向平均速度和切向平均速度变化.模拟结果可以为燃烧器的设计和运行提供依据.     

甲烷在过量焓燃烧器内的燃烧特性

设计了一个通道截面为7 mm x0.6 mm的等速螺线过量焓微燃烧器,并在其中完成了CH4/空气预混气的燃烧实验.通过数据采集系统得到了微燃烧器端面的温度分布,使用气相色谱法分析了烟气成分.实验结果表明,过量焓燃烧器能够通过逆流换热有效地实现热量回收,提高可燃预混气进入燃烧区前的温度,有利于微尺度火焰的稳定,并在较宽的空气过量系数范围内实现甲烷/空气预混气在燃烧器的中心稳定燃烧.当空气过量系数大于1时,甲烷可以实现完全燃烧;当空气过量系数小于1时,烟气中存在H2和CO,但无残留的甲烷.     

Swiss-roll型微燃烧器的燃烧数值模拟

建立了Swiss-roll型微燃烧器的燃烧模型,采用FLUENT软件对微燃烧器中甲烷/空气的燃烧特性进行了数值模拟,研究了甲烷/氧气的当量比为1时流速不同对微燃烧器内燃烧的影响。计算结果表明,Swiss-roll型微燃烧器有利于甲烷在微燃烧室内的充分燃烧。     

钝体缝隙式燃烧器在低热值煤气锅炉中的应用及强化燃烧技术分析

介绍了一种低热值煤气燃烧器－－钝体缝隙式燃烧器的设计与应用，分析了该燃烧器强化燃烧的机理，认为提高初始阶段低热值煤气的可燃物浓度和温度是稳定燃烧的关键。     

带入口旋流器的文丘利油燃烧器出口热态流场的数值模拟

针对带入口旋流器的新型文丘利油燃烧器出口流动燃烧的特点，建立了相应的数学物理模型和数值算法。在数值模拟一、二次风道内部流动及出口等温流场的基础上，对新型油燃烧器出口的热态流场进行了数值模拟，并与未装设入口旋流器的文丘利油燃烧器出口冷热态模拟结果进行了对比分析。模拟结果为该型油燃烧器的进一步改进设计、运行及布置提供了重要依据。图9表1参10     

新型直流燃烧器燃烧性能的数值模拟分析

为了解决超低负荷下煤粉燃烧器的稳燃和NOx排放等问题,研发了一种新型直流煤粉燃烧器,通过数值模拟分析发现该燃烧器具有高浓缩比的特点,出口NOx排放浓度在180mg/m3(O2 =6％)以内,同时喷口处能够形成稳定的回流区,保证了煤粉着火的稳定性,可见该新型燃烧器具有良好的低NOx排放及稳燃特性.     

Numerical simulation of laminar premixed combustion in a porous burner

Premixed combustion in porous media differs substantially from combustion in free space. The interphase heat transfer between a gas mixture and a porous medium becomes dominant in the premixed combustion process. In this paper, the premixed combustion of CH₄/air mixture in a porous medium is numerically simulated with a laminar combustion model. Radiative heat transfer in solids and convective heat transfer between the gas and the solid is especially studied. A smaller detailed reaction mechanism is also used and the results can show good prediction for many combustion phenomena. Translated from Journal of Combustion Science and Technology, 2006, 12(1): 46–50 [译自: 燃烧科学与技术]     

Fuel‐lean VOCs combustion in a porous burner stacked with alumina balls: A case for ethylene combustion

A porous burner stacked in turn with 3‐ and 9‐mm alumina pellets was established to perform C₂H₄ combustion experiments by acquiring the flammable limits, temperature variation characteristics, combustion wave velocity, pollutant emissions, and treatment efficiency. The burner operated well at equivalence ratios within 0.3 to 0.7. Larger alumina pellets widened the burner's lower flammable limit. As the flame propagated downstream, the higher premixed gas flow velocity and larger alumina pellets, the higher combustion wave velocity, whereas the circumstances were opposite as the flame spread upstream. The combustion temperature increased with the equivalence ratio and premixed gas flow velocity. In response to the effect of the alumina pellet dimension, 3‐mm alumina pellets corresponded to higher combustion temperatures, lower CO emissions, and higher treatment efficiency than those less than 9‐mm conditions.     

旋流燃烧器螺旋伸展长度对高温空气燃烧特性的影响

以工业炉的高温空气燃烧技术应用为背景,对一个同心式轴向旋流高温空气燃烧器单烧嘴燃烧室内的高温空气燃烧特性进行了数值研究.燃烧室尺寸为600 mm×600 mm×1000 mm,燃烧器烧嘴由位于中心的圆形直射流燃气喷口和其外围的同心轴向旋流高温预热空气射流喷口构成.湍流输运方程采用RSM模型,气相燃烧模型采用β函数的PD...     

Simulation of thermally‐enhanced combustion in a porous medium burner

Premixed combustion in a porous medium burner is investigated numerically. A two‐dimensional steady, laminar flow model is used. A single‐step reaction of methane is used for the chemical kinetic model. The model also includes thermal radiation transport of the porous media that is placed inside the burner. The radiative transport equation is solved by using the discrete ordinate method. The results show that, for each equivalence ratio, the flame can be stabilized at various axial locations with different flame speeds. The flame temperature increases with the equivalence ratio and flame speed. Furthermore, the energy release rates are much higher than that of a free flame for the same equivalence ratio as a result of higher flame speed. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 35(1): 75–88, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20088     

高温空气燃烧燃气热态试验炉非稳态数值模拟

采用双方程湍流模型、概率密度函数(PDF)燃烧模型和离散坐标(DO)辐射模型，对采用高温空气燃烧技术的燃气热态试验炉炉内工况进行了非稳态数值模拟，预测热态试验炉运行时的炉内温度场、组分场和速度场，由数值模拟结果分析比较了不同喷口间距五喷口燃烧器对炉内工况的影响，为采用高温空气燃烧技术的燃气燃烧器设计提供参考。     

Numerical simulation of bituminous coal combustion in a full-scale tiny-oil ignition burner: influence of excess air ratio

The progression of ignition was numerically simulated with the aim of realizing a full-scale tiny-oil ignition burner that is identical to the burner used in an 800 MWe utility boiler. The numerical simulations were conducted for four excess air ratios, 0.56, 0.75, 0.98 and 1.14 (corresponding to primary air velocities of 17, 23, 30 and 35 m/s, respectively), which were chosen because they had been used previously in practical experiments. The numerical simulations agreed well with the experimental results, which demonstrate the suitability of the model used in the calculations. The gas temperatures were high along the center line of the burner for the four excess air ratios. The flame spread to the burner wall and the high-temperature region was enlarged in the radial direction along the primary air flow direction. The O₂ concentrations for the four excess air ratios were 0.5%, 1.1%, 0.9% and 3.0% at the exit of the second combustion chamber. The CO peak concentration was very high with values of 7.9%, 9.9%, 11.3% and 10.6% for the four excess air ratios at the exit of the second combustion chamber.     

Development and characterization of a low-NOx partially premixed hydrogen burner using numerical simulation and flame diagnostics

The utilization of hydrogen as a fuel in free jet burners faces particular challenges due to its special combustion properties. The high laminar and turbulent flame velocities may lead to issues in flame stability and operational safety in premixed and partially premixed burners. Additionally, a high adiabatic combustion temperature favors the formation of thermal nitric oxides (NO). This study presents the development and optimization of a partially premixed hydrogen burner with low emissions of nitric oxides. The single-nozzle burner features a very short premixing duct and a simple geometric design. In a first development step, the design of the burner is optimized by numerical investigation (Star CCM+) of mixture formation, which is improved by geometric changes of the nozzle. The impact of geometric optimization and of humidification of the combustion air on NO_x emissions is then investigated experimentally. The hydrogen flame is detected with an infrared camera to evaluate the flame stability for different burner configurations. The improved mixture formation by geometric optimization avoids temperature peaks and leads to a noticeable reduction in NO_x emissions for equivalence ratios below 0.85. The experimental investigations also show that NO_x emissions decrease with increasing relative humidity of combustion air. This single-nozzle forms the basis for multi-nozzle burners, where the desired output power can flexibly be adjusted by the number of single nozzles.