Influence of nozzle design parameters on exhaust gas characteristics in practical-scale flameless hydrogen combustion

Considering the trend toward decarbonization, hydrogen is expected to be used as a fuel in industrial furnace burners. One of the challenges in using hydrogen as a fuel is the increase in thermal-NOx emission compared to hydrocarbon fuel owing to its high flame temperature. This study experimentally evaluated the combustion characteristics of flameless combustion, which is a low-NO_x combustion technology, with hydrogen as a fuel in a practical-scale experimental furnace as well as the effect of nozzle design parameters on the combustion characteristics. Through comparative tests with city gas by considering parameters, such as the fuel gas velocity, combustion air velocity, and air nozzle pitch, the low-NO_x effect of flameless combustion was confirmed in hydrogen combustion with appropriate nozzle design parameters. The optimal nozzle design parameters to achieve this effect differ from those for city gas, and the design guidelines are summarized.     

顶燃式热风炉燃烧过程的数值模拟研究

针对某公司的旋流顶燃式热风炉及其工艺参数,建立了气体流动、传热的数学模型,采用非预混燃烧方法处理煤气的燃烧,对其现有工况进行了数值模拟,分析了炉体内部的流场、温度场和浓度场.结果表明,燃烧室温度分布不均匀,出口温度较低;由（于）空气过剩系数较小,导致煤气燃烧不充分,有大量CO剩余;火焰长度较长,严重影响格子砖的寿命.通过调整空气过剩系数,（）的增加空气过剩系数,燃烧室出口CO体积分数明显降低,火焰长度明显变短,出口温度明显提高.     

甲烷/空气典型混合模式在约束空间内的燃烧特性研究

燃料质量浓度分布在一定程度上影响混合气体的燃烧效率,能使燃气充分混合的同轴射流、旋片同轴、轴切结合、切向旋流等典型混合模式在航空发动机、燃气轮机及火箭发动机等先进燃烧技术应用中较为常见。因此,设计了甲烷/空气部分预混的燃烧实验装置,较为系统地实验研究了旋流数和轴向流速对混合气体在约束空间燃烧室内燃烧特性的影响。结果表明：对于有中心射流的混合结构,燃气轴向流速较低时产生黄色火焰,增大轴向流速,黄色火焰转为蓝色湍流火焰,且温度分布趋于均匀;纯切向旋流燃烧器的掺混效果较好,受燃气轴向流速的影响小,火焰结构稳定,均为蓝色火焰,温度轴/径向分布均匀且趋势一致,同当量比下燃烧产物中的污染物体积分数最小。     

空气分级比对同轴分级燃烧室性能参数的影响

为掌握同轴分级燃烧室性能参数随空气分级比(主燃级空气流量的比值)的变化规律,以某同轴分级燃烧室为研究对象,数值分析了空气分级比对燃烧室的燃烧效率、总压损失、出口温度分布、污染物排放和绝热壁面最高温度的影响。结果表明：空气分级比主要会改变角涡位置的燃烧温度和高温烟气的停留时间;随着空气分级比的升高,燃烧室总压损失、出口温度分布系数、NO_x排放、绝热壁面最高温度逐渐升高,但燃烧效率、CO污染物排放、径向温度分布系数对空气分级比不敏感;在同轴分级燃烧室设计中,在保证燃烧稳定的前提下可采用较小的空气分级比以实现燃烧室高效、低阻、低污染燃烧。     

新型常温空气无焰燃烧实现技术及特性分析

在介绍了无焰燃烧思想及其常规蓄热式高温空气实现技术的基础上,重点介绍了本课题组发展的常温空气无焰燃烧技术,并对其进行了效率、环保、经济性、安全性和应用范围等特性分析,该技术不但完全保留了高温空气无焰燃烧技术相对于传统燃烧的优点,并且不需要复杂的预热系统和换向机构,避免了燃烧过程的脉动,适用于低排烟温度或含灰量较大排烟的燃料的直接燃烧,具有一定的技术优势和更广泛的应用范围。     

过剩空气系数对多种燃气燃烧温度影响的分析

钢铁企业炼钢过程中产生数量众多的焦炉煤气、高炉煤气、转炉煤气和COREX煤气等各类燃气,燃气燃烧温度受燃气燃烧的过剩空气系数、空气和燃气的被加热温度等因素影响很大.空气和燃气温度均被加热到400℃时,各种燃气的燃烧温度显著提高,对于低热值高炉煤气燃烧温度提高约200℃,达到1580℃.同一燃烧设备当燃用燃气种类发生变化...     

旋流对天然气高温空气燃烧特性影响的数值模拟

以工业炉的高温空气燃烧技术应用为背景,对一个新型轴向旋流式单烧嘴燃烧室内天然气的高温空气燃烧特性进行了数值研究。采用数值模拟的方法研究了同心式轴向旋流燃烧器（HCASbumer）中螺旋肋片的旋转角度对燃烧特性的影响,其中湍流采用Reynolds应力模型,气相燃烧模拟采用β函数形式的PDF燃烧模型,采用离散坐标法模拟辐射换热过程,NOx模型为热力型与快速型。计算结果表明,对预热空气采用旋转射流时,能明显降低NOx生成量。对于HCAS型燃烧器,随着空气射流旋转角度的增大,燃烧室内的回流区域增大增强,降低了局部的氧体积分数分布,燃烧室中平均温度和最高温度都有所增加,且燃烬程度大幅度提高,而局部高温区缩小,只在靠近入口处出现。总的NOx排放量随着空气射流旋转角度的增大先减小,后增大。因此,适当调整肋片的旋转角度可以降低NOx生成量。     

高温空气燃烧技术的开发应用、技术优势及其展望

高温空气燃烧技术和高温空气气化技术是当前世界节能与环保领域中的两大新技术,二者均采用高于燃料着火点温度的高温空气作氧化剂或气化剂。介绍了利用蓄热式高温烟气余热回收装置和专门的高温空气发生器产生高温空气的方法,前者主要用于高温空气燃烧技术,后者主要用于高温空气气化技术。概括了高温空气燃烧技术和高温空气气化技术的应用状况,总结了其技术优势,并指出高温空气燃烧技术和高温空气气化技术符合中国国情,具有巨大的开发潜力和广阔的市场前景。     

Experimental and numerical study of the effect of initial temperature on the combustion characteristics of premixed syngas/air flame

The effects of different initial temperatures (T = 300–500 K) and different hydrogen volume fractions (5%–20%) on the combustion characteristics of premixed syngas/air flames in rectangular tubes were investigated experimentally. A high-speed camera and pressure sensor were used to obtain flame propagation images and overpressure dynamics. The CHEMKIN-PRO model and GRI Mech 3.0 mechanism were used for simulation. The results show that the flame propagation speed increases with the initial temperature before the flame touches the wall, while the opposite is true after the flame touches the wall. The increase in initial temperature leads to the increase in overpressure rise rate in the early flame propagation process, but the peak overpressure is reduced. The laminar burning velocity (LBV) and adiabatic flame temperature (AFT) increase with increasing initial temperature. The increase in initial temperature makes the peaks of H, O, and OH radicals increase.     

低NOx高温空气燃烧技术

低NOx高温空气燃烧技术将传统的低NOx燃烧技术与高温热式燃烧系统有地结合起来，具有热效率高、炉内温度分布均匀、NOx排放量低等特点。本文介绍了高温空气燃烧技术，重点分析了高温空气燃烧技术中的低NOx排放的原理，并对两种采用烟气再循环和分级燃烧技术的NOx高温空气燃烧器进行阐述。     

常温高预混度甲烷火焰燃烧特性研究

使用自行研制的微型天然气燃烧装置,利用FTIR发射透射技术,借助傅立叶变换红外光谱仪在线测量了常温高预混度条件下甲烷火焰的温度和辐射力。通过试验得出了较高预混度条件下常温甲烷火焰的碳黑生成、火焰辐射和火焰温度等方面的燃烧特性。     

空气分级对燃烧室燃烧及污染物排放的影响

燃烧气体燃料的工业用直流式燃烧装置为射流进气，采用空气轴向分级的燃烧组织方式，使用多孔板火焰稳定器稳定火焰．实验在一定的燃料流量和一定的空气总量下，改变两级空气的配比，采用testo360烟气分析仪分别测量燃烧室出口截面的温度、NOx和CO的排放量．通过对两级空气不同配比情况下燃烧室出口截面温度、CO和NOx排放量的分析，得到两级空气不同配比对燃烧和污染物排放影响的规律．此外，初步探讨了一级燃烧区长度对燃烧和污染物排放的影响．     

燃低热值煤气工业锅炉技术的开发与应用

本文阐述了国内工业锅炉的现状，从保证高的火焰温度、降低煤气着火下限、加强煤气与空气混合三方面论述了低热值煤气的强化燃烧技术，并将以上强化燃烧措施应用在一台燃煤工业锅炉的改造上，改造后的锅炉取得了令人满意的效果。     

燃烧参数影响高温空气燃烧特性的数值分析

高温空气燃烧技术具有高效节能和低NOx排放等多重优越性，是一种新型燃烧技术。为了深入研究高温空气燃烧机理和低氮氧化物排放特性，将湍流N—S方程与扩散燃烧模型和热力型NO生成模型相结合，研究了低氧浓度条件下，燃烧参数，如燃气供应量，过量空气系数，进口空气预热温度以及进口空气氧含量对燃烧的影响，为发展高温空气燃烧技术提供了理论依据。     

高温空气燃烧技术的特点及其应用前景

高温空气燃烧技术（HTAC）是九十年代初在日本开发的一项新的燃烧技术，该项技术具有节约燃烧、低NOx排放、热利用率高和减设备尺寸等特点。分析了HTAC的火焰温度分布特征及其可降低NOx排放的原理。高炉煤气、焦炉煤气及94．5％高炉煤气与5．5％焦炉煤气的混合煤气应用于HTAC技术的理论计算结果表明，理论燃烧温度随着预热空气和燃气温度的升高而升高，因此HTAC技术可燃用传统燃烧方式不能使用的低热值燃气。此外，空气、燃气双预热可奖排烟温度将得更低，热利用率提高更高。最后，指出了在燃油、燃气锅炉及煤（或可燃固体废弃物）气化系统中采用HTAC技术的可能性。     

高温低氧燃烧条件下氮氧化物的生成特性

高温低氧燃烧原理是高温空气燃烧技术赖以发展的基础，使得高温燃烧条件下的氮氧化物的生成与排放受到大大抑制。为了掌握这种非常规燃烧现象及污染物生成的基本规律，采用扩散燃烧模型、热力NO生成模拟与湍流N－S方程，数值研究了燃烧空间中空气氧浓度对燃烧特性和氮氧化物排放浓度的影响，再现了高温与低氧两种条件相结合，形成的稳定的低氮氧化物排放的燃烧特性。计算结果与实验数据吻合，为发展高温空气燃烧技术提供了理论基础。     

空气预热温度对生物柴油火焰特性影响研究

利用高速摄影法及数字图像处理技术得到生物柴油燃烧火焰图像,并通过Matlab软件求取火焰长度和面积,研究了空气预热温度对火焰形态、长度、面积的影响。实验中共设定了9个空气温度：20℃、80℃、140℃、220℃、290℃、350℃、400℃、450℃和500℃。结果表明：空气预热温度较低时,生物柴油火焰结构分散、主要燃烧区（火焰亮度较高区域）面积较小且连续性差;空气预热温度升高后,火焰结构更紧凑、主要燃烧区面积增大、亮度明显增加、连续性变好。各个工况下火焰长度和面积不是一个定值,而是在一定范围内剧烈地震荡,随着空气预热温度的升高,火焰平均长度和平均面积有相近的变化趋势：先明显减小,再逐渐上升。     

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.     

A review on plasma combustion of fuel in internal combustion engines

In recent years, new ways of improving the combustion efficiency of fuel during gas turbine operations have been developed. The most significant has been the application of plasma technology for the combustion of fuel in gas turbine operations. Plasma is formed when gas is exposed to either high temperature or high‐voltage electricity. This technology is very promising and has proven to enhance the performance of gas turbines and reduce toxic emissions. Recent studies have shown the use of different types of plasma applications in gas turbine operations such as plasma torch, filamentary discharge, and nanosecond pulse discharge, whose results show that plasma technology has great potential in improving flame stabilization, the fuel/air mixing ratio, and flash point values of these fuels. These findings and advances have further provided new opportunities in the development of efficient plasma discharges for practical uses in plasma combustion of fuel for gas turbine operations. This article is a comprehensive overview of the advances and blind spots in the knowledge of plasma combustion of fuel during internal combustion engine operations. This review also focuses on applications, methods, and experimental results in plasma combustion of fuel in gas turbines.     

工业炉燃烧系统应用技术探讨

燃烧及其控制技术是各种火焰炉技术核心，强调高水平燃烧系统应对燃烧全过程进行控制，着重对燃烧系统点火、火焰监测、空燃比比例调节、燃烧过程各参数监控、炉温自动控制等各个方面内容进行了讨论介绍，最后用某天然气加热炉燃烧系统原理图及应用效果进行实例说明。