煤掺烧生物质旋流燃烧器流场的数值模拟

为探索适用于煤掺烧生物质的旋流燃烧器结构形式,采用Fluent软件对旋流燃烧器进行了冷态数值模拟,计算结果表明旋流叶片安装角度合适,旋流燃烧器中流出的气体质点既有旋转向前的趋势,又有从切向飞出的趋势,气流初期扰动非常强烈。研究发现改变燃烧室形状对燃烧室内气相速度场、颗粒轨迹以及湍流强度等特性参数都有较大影响,长方体型燃烧室对燃料和氧化剂的混合和燃烧更有利。     

旋流煤粉燃烧器的气流组织与数值模拟

旋流煤粉燃烧器的气流组织情况对锅炉的稳定燃烧与安全运行都具有重要的影响,以CFD数值软件作为计算平台,通过建立物理和数学模型,针对某电厂采用的中心给粉型旋流煤粉燃烧器进行了数值模拟研究,通过调整一次、二次风速大小,得到不同运行工况下的速度流场和速度矢量分布,经分析各计算结果,得出各参量对流场的影响规律.     

旋流燃烧器数值模拟和优化改造

某电站煤粉锅炉采用旋流燃烧器,在运行中燃烧器出现调节能力差的问题.针对此情况,我们分别按照分析缺陷、虚拟改造以及优化改造3个步骤进行研究,以及对应的3个不同工况进行了数值模拟计算.运用k-ε数学模型,并借助Fluent 6.0对单个旋流燃烧器的一、二次风的流场进行三维数值模拟计算.通过数值模拟我们对旋流燃烧器进行了优化改造,并通过有限的但是精确的现场测试数据对比,很好地验证了本次数值模拟的准确性.     

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     

低热值燃气双旋流燃烧器空气动力场数值模拟

介绍了一款燃用低热值燃气的双旋流燃烧器,重点分析了旋流装置和喧口的设计,并采用Fluent软件研究燃烧器的空气动力学特性,获得了燃烧器在不同负荷下的流场形式。模拟结果表明:该燃烧器能够营造良好的流场结构,适用于低热值燃气的燃烧,具有良好的负荷适应性。     

低NO_x旋流燃烧器的数值模拟

HT-NR3型低氮旋流燃烧器在我国大型电站锅炉中应用较多,但很多采用HT-NR3型燃烧器的锅炉侧墙水冷壁经常发生严重的高温腐蚀问题。文中通过数值模拟的方法研究了该旋流燃烧器的火焰和污染物排放特点,分析了燃烧器外二次风叶片角度对NOx的排放和水冷壁腐蚀之间的关系。模拟结果表明:燃烧器炉膛出口处焦炭颗粒的浓度、回流区的尺寸在叶片角度为45°时分别达到最小和最大。在叶片角度为45°时煤粉颗粒燃尽情况较好,因而在不考虑灰分的情况下,能够减少颗粒物对水冷壁的冲刷。炉膛出口处的NO浓度的统计显示,45°叶片时较其他两个工况的NO浓度稍高。     

带中心钝体旋流燃烧器的数值模拟

借助FLUENT软件平台,对旋流燃烧器出口的流场进行了三维数值模拟,得出了燃烧器出口的流线、回流区、湍流动能分布.此外,分析了中心钝体形状及旋流二次风速对回流区大小的影响.模拟结果为工业运行、设计和改造提供了参考.     

燃气燃烧器燃烧特性的数值模拟

运用Fluent软件对40 t/h锅炉用燃气燃烧器进行三维数值模拟,研究进风量对燃烧器性能及污染物NOx排放特性的影响。结果表明:合适的进风量是保证燃烧器稳定燃烧的重要条件,也是减少NOx排放的关键因素。数值模拟的计算结果为燃烧器优化设计、改造提供了参考依据。     

煤粉浓淡旋流燃烧器空气动力学特性的数值模拟

将湍流重整化群ε方程与ＺｈａｎｇＪｉａｎ提出的新代数应力模型结合,用于模拟煤粉浓淡燃烧器喷口强旋转流场。通过对７个工况流场的计算,并与实验结果比较,得出燃烧器喷口流场随参数变化的规律,同时对流场特性作了分析。     

低NO_x旋流燃烧器改造数值模拟

对DBC-OPCC-Ⅰ型旋流燃烧器进行了结构上的优化改造,并利用Fluent软件对改造前后的单个旋流燃烧器进行了数值模拟计算,分析了改造前后燃烧器区域的速度场、温度场以及NOx体积分数分布.结果表明:改造后的速度场出现中心回流区,且回流区在长度和宽度上均有所增加,速度明显减小;改造后的整体温度分布有所降低,最高温度降幅达200K,尤其是旋流燃烧器出口扩锥处的温度明显降低;改造后的NOx体积分数也显著降低,NOx最高体积分数可降1×106,改造后旋流燃烧器的性能比改造前优越.     

Performance simulation of a low‐swirl burner for a Stirling engine

A new type of gas burner for Stirling engine that can recover adequate heat from exhaust gas was designed based on the plate heat exchanger and low‐swirl combustion technology, which consists of three components: a cyclone, a burner, and a circular plate heat exchanger. The circular plate heat exchanger tightly wound around the combustion chamber plays a high efficiency of heat recovery role. In consideration of the radial symmetry of the burner, a three‐dimensional numerical simulation was carried out by Ansys15. The velocity distribution, temperature distribution, and pressure distribution of the combustion gas were presented respectively. Strong backflow that came from the exhaust gas around the root of the flame in the combustion chamber and a vortex below the inlet of the exhaust gas channel were found, which were beneficial for the combustion and improving the uniformity of temperature distribution. Combustion behaviors of the burner under standard operating conditions were obtained, the highest temperature was about 2200 K in burner and the exhaust gas entered the plate heat exchanger at the temperature of 1375 K and exited at 464 K, with the waste heat recovery efficiency over 65.8%. And, the air‐fuel ratio and combustion power had negligible effect on the waste heat recovery efficiency.     

煤粉锅炉旋流燃烧器冷态流场数值模拟

旋流煤粉燃烧器因具备形成中心回流区,卷吸高温烟气,促进煤粉着火等显著优势和特点,在电站锅炉中的应用日益广泛.而旋流煤粉燃烧器的流动情况对锅炉的稳定燃烧和安全运行都具有重要影响.通过建立物理模型和数学模型,对旋流燃烧器进行了三维数值计算得到燃烧器中钝体形状、二次风速及外二次风叶片角度等因素对回流区产生的具体影响.计算结果...     

低NO_x旋流燃烧器的研究进展

随着分级燃烧和高浓度煤粉燃烧技术的不断进步,低NOx旋流燃烧器得到了不断发展和完善。本文对国内外典型的低NOx旋流燃烧器的研究进展做了总体回顾,总结了低NOx旋流燃烧器的发展趋势。     

The influence of swirl burner structure on the gas/particle flow characteristics

Improvements were made to a low-NO_x axial swirl burner (LNASB), aimed at mitigating slagging in a 600-MWe boiler burning bituminous coal. The new design is referred to as improved low-NO_x axial swirl burner (ILNASB). This paper describes investigations of the influence of swirl burner structure on the gas/particle flow characteristics using a three-dimensional particle-dynamics anemometer. In comparing results from both ILNASB and LNASB, a central recirculation zone is seen to form in the region x/d = 0.1–0.3 within the ILNASB. This zone had shifted from the region between primary and secondary air in LNASB to a region between inner and outer secondary air. In the vicinity of the burner outlet, particle volume flux is reduced significantly in the central recirculation zone. In contrast, this flux is high near the central axis in ILNASB, thus concentrating a great fraction of pulverized coal near the central axis. Form the study, the gas/particle flow characteristics of the ILNASB show that the improved burner has the ability to ease slagging and reduce NO_x emissions.     

Decarbonized combustion performance of a radiant mesh burner operating on pipeline natural gas mixed with hydrogen

With the pressing need to reduce greenhouse gas emissions, blending lower or zero carbon fuels like renewable hydrogen into natural gas is a promising and practical way to achieve clean energy transition. From the perspective of end users and combustion device manufactures, one of the major concerns is the influence of the renewable contents on the combustion devices performance. The possible renewable gas content percentage in pipeline also interests policy makers and gas utility companies. The present study investigates on the influence of hydrogen contents on the operating performance of a surface burner, which is widely adopted in industrial, commercial and residential applications. The interactions among heating load, excess air level and fuel contents are studied by a 3-factor13-level experiment design. Evaluated combustion performance characteristics include flame characteristics, burner/exhaust temperature and emissions (NO, NO₂, N₂O, CO, UHC, NH₃). The results showed that hydrogen addition to natural gas slightly increased the burner surface temperature but did not have significant impact on other burner performance parameters. Up to 20% (by volume) natural gas was replaced by hydrogen, and no abnormal effect was observed. Furthermore, tests carried out in a prototype water heater showed similar performance. This study gives a positive sign relative to replacing pipeline natural gas with renewable hydrogen at a low percentage without modifying the burner geometry.     

Experimental assessment of the combustion performance of an oven burner operated on pipeline natural gas mixed with hydrogen

With the increasing need to reduce greenhouse gas emission and adopt sustainability in combustion systems, injection of renewable gases into the pipeline natural gas is of great interest. Due to high specific energy density and various potential sources, hydrogen is a competitive energy carrier and a promising gaseous fuel to replace natural gas in the future. To test the end use impact of hydrogen injection into the natural gas pipeline infrastructure, the present study has been carried out to evaluate the fuel interchangeability between hydrogen and natural gas in a residential commercial oven burner. Various combustion performance characteristics were evaluated, including flashback limits, ignition performance, flame characteristics, combustion noise, burner temperature and emissions (NO, NO₂, N₂O, CO, UHC, NH₃). Primary air entrainment process was also investigated. Several correlations for predicting air entrainment were compared and evaluated for accuracy based on the measured fuel/air concentration results in the burner. The results indicate that 25% (by volume) hydrogen can be added to natural gas without significant impacts. Above this amount, flashback in the burner tube is the limiting factor. Hydrogen addition has minimal impact on NO_X emission while expectedly decreasing CO emissions. As the amount of hydrogen increases in the fuel, the ability of the fuel to entrain primary air decreases.     

轴向涡流燃烧器内部流动数值分析

以STAR-CD等计算分析软件为基础建立了一个基于完整真实的三维几何结构的燃烧器内部流动数值分析平台;利用数值模拟的方法,分别对两种不同二次风风口尺寸情况轴向涡流燃烧器的流场进行了数值模拟,以此来分析轴向涡流燃烧器内部流动情况。利用计算分析系统,可以分析燃烧器内部流动的一些主要特征,为电厂实际生产提供参考依据。     

Optimization of producer gas fired premixed burner

Much work is reported in the literature pertaining to premixed burners using hydrocarbon fuels. However, very little work is available on similar burners using producer gas as a fuel. The present work aims at testing and optimization of a premixed burner with producer gas as a fuel.A burner of 150 kW capacity is used in the experimental investigations. The burner is of concentric tube type fully premixed in which air is supplied through central pipe and gas is supplied through annular passage. Swirl vane is provided to air and gas for thorough mixing. The bluff body is provided for flame stabilization. The premixed burner was tested on open core throat-less down draft gasifier for flame quality. A stable and uniform flame was observed with this premixed burner. Thereafter, an instrumented test set up to evaluate burner performance was installed on an open core gasifier. The burner was experimentally optimized for size and location of bluff body and flammability limits. The burner was optimized by using bluff bodies of 46, 61, 73, 80, 85, 98, 110 and 122 mm diameters. The burner was operated in batch operation of 6–8 h for optimization of various parameters. The experiment reveled that the uniform and high-temperature premixed flame was observed at conventional bluff body having blockage ratio of 0.65. The flammability limits for producer gas fired burner was established in the range of 40–55.     

Experimental investigation of producer gas burner for thermal application

This paper deals with the performance evaluation of a premixed-type burner with producer gas, in terms of emission, axial and radial flame temperature. In this study, a burner of 150 kWth capacity was tested on an open core downdraft-type gasifier. The developed burner is a concentric tube-type where the air is supplied through a central tube, which is surrounded by another one. The burner consists of a swirl vane for mixing the air and producer gas, mixing tube and bluff body for flame stabilization. Swirl angle and bluff body diameter were kept constant throughout the study. The burner was evaluated with an open core downdraft-type gasifier. The temperature evaluation and emission testing was done for three flow rates and air–fuel ratio. The study shows low NO _x and CO emission at 125 Nm³ h^?1 when compared with that of 75 and 100 Nm³ h^?1. Maximum flame temperature (753 °C) was recorded at 10 cm axial and 10 mm radial distance.     

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.