This paper reviews research advances in pollutant emissions control via various NTP-assisted ap-proaches during combustion,with a particular focus on their impacts on NOx and dioxin mitigation.Firstly,the mechanism by which radicals(e.g.,O,H,OH)generated by NTP influence the combustion process is intro-duced.Secondly,the application of NTP technology in gaseous,solid,and liquid fuel combustion is analyzed,along with the effects of parameters such as voltage and power on NOx emissions and the associated reaction kinet-ics mechanisms.Thirdly,the degradation mechanisms of dioxins and their precursors during solid waste combus-tion,mediated by radicals such as OH,H,and O generated by NTP,are summarized.Finally,the effects of NTP on ignition delay time and combustion efficiency during ignition and combustion are discussed.In general,NTP-assisted combustion is a highly promising technology,and it will play a significant role in enhancing the solid wastes'combustion efficiency and reducing emissions of pollutants such as NOx and dioxins.
A study was conducted on the combustion and emission characteristics of a gas turbine fueled by natural gas at a high hydrogen-blending ratio.Based on the Reynolds stress model(RSM)and non-premixed combustion model,the impact of different hydrogen-blending ratios(volume fraction αH2=0-0.8,five groups in total)on the performance of a can-type combustor was analyzed under constant fuel mass flow.The results show that when the hydrogen-blending ratio increases to 0.8,the internal flow velocity of the combustor rises,but the area of the central recirculation zone is compressed.The maximum internal temperature,wall temperature,and outlet tem-perature of the combustor all increase,with the flame width in the central region expanding and the outlet tempera-ture uniformity improving(outlet temperature distribution factor decreases by approximately 24%).CO2 emissions are reduced by 36.95%,while H2O and NOx emissions increased significantly.This study can serve as a reference for the design and operation of hydrogen-blended gas turbines.
Aiming at a mmonia's high ignition energy and low combustion rate,an active pre-chamber-type am-monia-hydrogen engine combustion system was designed and developed.The influence of injection/ignition match-ing strategies on engine combustion characteristics under jet ignition mode was numerically investigated.The re-sults indicate that the"inject-before-ignite"strategy with a shorter injection-ignition interval delivers optimal com-bustion performance(combustion duration of 26.5 ℃A,indicated thermal efficiency of 43.7%).This is attributed to the pronounced concentration stratification formed in the pre-chamber,which facilitates the formation and de-velopment of flame kernels,enhances the combustion-promoting efficacy of jet ignition,and thereby improves the indicated thermal efficiency.However,higher combustion temperatures in the cylinder lead to the increased NOx emissions in high-temperature oxygen-rich zones,while N2O formation due to low-temperature accumulation remains relatively low.
Experiments on laminar jet diffusion flames were conducted aboard China's Space Station under varying fuel flow rates and ambient oxygen concentrations(21%—30%).Measurements of flame morphology and the dis-tributions of OH* and CH* was obtained.By combining these data with numerical simulations,the flame charac-teristics under different operating conditions were analyzed,along with and the influencing mechanisms of ambi-ent oxygen concentration and fuel flow rate on flame morphology.The results show that as the fuel flow rate gradu-ally increases,the flame morphology undergoes a transition from hemispherical to conical and finally cylindrical.An excessively large flame radiation fraction is the primary reason for flame opening at the tip,while an increase in ambient oxygen concentration promotes the closure of the flame tip.Compared to normal gravity,flames in microgravity exhibit lower flow velocities,which leads to higher flame radiation and lower flame temperature.
This study investigates the scientific and practical feasibility of coal slime co-combustion through ther-mogravimetric analysis(TGA)and numerical simulation.First,combustion characteristic parameters were deter-mined for 15 types of bituminous and lignite coals,as well as two types of coal slime samples,each prepared with ten different moisture contents,under varying heating rates and particle sizes.The analysis quantitatively revealed that the moisture content of 30%serves as a critical threshold for slime combustion characteristics,beyond which combustion performance drops significantly by 30.50%—45.65%.Under this threshold,co-combustion experiments with slime and nine bituminous coals identified an optimal slime blending ratio of 10%.To address the limited research on slime application in opposed-fired boilers,a 600 MW π-type single-furnace,one-time intermediate reheat boiler was selected for validation.The test results within an error range of 6%were consis-tent with the simulation results.The study found that the introduction of coal slime can reduce the generation of NOx,but if the co-combustion ratio is too high,it will cause local excessive SO2.Overall,the recommended co-combustion ratio of coal slime under the 100%BMCR condition is 10%.Relevant data can provide a good reference for the co-combustion of coal slime.
An optical rapid compression and expansion machine(RCEM)platform was used to establish a flame natural luminosity visualization system.The effects of pilot diesel injection timing,injection quantity,and injec-tion pressure on the ignition and combustion characteristics of ammonia-methane premixed mixtures were investi-gated.Flame propagation images,ignition delay,flame projection area,in-cylinder pressure,and heat release rate were analyzed to reveal the combustion evolution under different injection conditions.The results show that the combustion process can be divided into two stages:a diesel-dominated first stage and a premixed-gas-dominated second stage.Advancing the injection timing increases the peak in-cylinder pressure and heat release efficiency.The optimal injection timing is from 12 to 9 crank angle degrees before top dead center.Increasing the injection quantity shortens the ignition delay and increases the flame area and peak cylinder pressure.The optimal injection quantity is 10 to 12 milligrams.Increasing the injection pressure strengthens the heat release in the first stage at low equiva-lence ratios.The optimal injection pressure is 100 to 120 megapascals.Adding 40%methane significantly increases the chemical reactivity of the mixture which shifts the combustion mode from diesel-dominated ignition to synergis-tically promoted combustion.
To investigate the fire behavior under coupled leakage-combustion conditions in kerosene storage and transportation vessels,small-scale leakage-fire experiments were conducted using anhydrous kerosene tanks.The results show that once the temperature of the leaking kerosene exceeded 193.96℃,the outflow underwent flash boiling and coupled combustion,leading to abrupt step increases in tank pressure,thermal radiation,burning noise,burning rate,and flame dimensions—i.e.,a sudden escalation of fire hazard.Moreover,the hazard se-verity increased as the leak diameter decreased or the filling level increased.The thermal response of the leaking tank was simulated in ANSYS Fluent,where the wall heat-flux boundary condition was inferred from a probabilis-tic distribution of flame impingement over the tank wall.This approach enabled the accurate prediction of kerosene temperature trajectory and the critical onset time of hazard escalation.Further simulations across a wider range of filling levels revealed that the onset time of hazard escalation increased exponentially with the filling level.These findings provide a theoretical basis for emergency response and hazard mitigation of leakage fires involving kero-sene tanks,fuel reservoirs,and related storage and transportation vessels.
To enhance the combustion heat recovery efficiency of coal gasification fine slag(CGFS),this study investigated the effects of coals with different degrees of coalification on the combustion characteristics of CGFS using thermogravimetric analysis(TGA),tube furnace,and bubbling fluidized bed testing equipment.TGA re-sults showed significant differences in the combustion behavior of lignite and CGFS,with distinct"phased com-bustion"characteristics during co-combustion.With the increasing proportion of raw coal,both ignition tempera-ture(Ti)and burnout temperature(Tb)decreased significantly.Simultaneously,comprehensive combustion charac-teristic index(S),burnout index(Db),and flammability index(C)exhibited an overall upward trend,which sug-gests that the incorporation of raw coal substantially enhances the combustion performance of CGFS.With the in-crease in raw coal rank,the co-combustion interaction transitions from an antagonistic to a cooperative one.The fitting results of Flynne-Walle-Ozawa(FWO)and Kissinger-Akahira-Sunose(KAS)indicate that the addition of raw coal significantly reduces the average activation energy of the mixed system.The evaluation of tube furnace burnout results indicates that the combustion rate of the mixed coal system is lower than that of any single compo-nent when lignite and bituminous coal are added.However,anthracite enhances the combustion rate via a syner-gistic effect.In addition,the elevated heating rate not only intensifies combustion by mitigating the thermal lag effect but also markedly enhances burnout performance through the promotion of sustained volatile and fixed car-bon release.The results of the fluidized bed combustion test indicate that high volatile matter content contributes to more efficient combustion.However,due to the high fixed carbon content,anthracite presents a pronounced en-ergy barrier during the carbon-oxygen reaction in the ignition phase,thereby limiting its combustion efficiency.
In this study,rice husk was selected as the feedstock,and pyrolysis experiments were conducted in a fixed-bed tubular furnace to systematically evaluate the influence of temperature on product distribution and the evolution of oxygenated compounds.With increasing temperature,the liquid yield decreased from 45.8%to 33.1%,whereas the gas yield rose from 13.6%to 34.6%.Temperature was identified as the dominant factor govern-ing the generation and transformation of oxygenated species.At temperatures below 600℃,phenolic and furanic derivatives,such as phenol,cresol,furfural,and furfuryl alcohol,were the predominant liquid products,accounting for 14.14%—62.92%.At higher temperatures(＞600℃),these compounds were progressively con-verted into aromatic hydrocarbons through decarboxylation and aromatization.This study elucidates the tempera-ture-dependent evolution of key oxygenated compounds and provides technical guidance for the regulation and valorization of tar during the thermal conversion of agricultural and forestry residues.
Experimental research was conducted on the fuel spray characteristics of conical atomizing nozzles in an integrated afterburner,analyzing the effects of transverse flow velocity and fuel supply pressure difference on the macroscopic and microscopic characteristics of the spray.Through LIF/Mie technology,it was found that the spray morphology of the conical atomizing nozzle was dominated by Rayleigh-Taylor and Kelvin-Helmholtz insta-bility phenomena.The atomization effect at the top of the spray was good,but it was significantly affected by the transverse flow.Increasing the fuel supply pressure difference could increase the spray projection area and droplet velocity,but it would lead to an increase in droplet size.Increasing the transverse flow velocity to 30 m/s could reduce the droplet size to below 60 μm.In addition,although the baffle structure increased the droplet size,it broadened the spray distribution range.
The present study is an extension of our prior study on the external group combustion (EGC) of droplet clouds under two-stage autoignition conditions [Zhou and Liu, Combust. Flame 234 (2021) 111689]. Effects of droplet heating and different n-alkane fuel candidates have been further considered. By comparing numerical results from n-heptane and n-dodecane, it was found that the fuel volatility has little effect on the combustion modes of droplet clouds. Among all the computed cases, internal group combustion (IGC) occurs for relatively low value of group ignition number Gig (= 4πn2/3d2, n and d are the droplet number density and diameter, respectively). When Gig further increases, the combustion mode can switch to EGC. IGC modes can be sustained by cool or hot flame. IGC of cool flame exhibits a partial burning structure, while IGC of hot flame is firstly premixed, followed by non-premixed structure. These flame structures were analyzed in details. A regime diagram based on Gig and ambient temperature Ta was developed for all the IGC modes. It was found that for high Ta (1500 K), Gig can be used to predict ICG modes, but for low Ta (900 K) and intermediate Ta (1200 K), additional parameters might be needed for the prediction, especially for the cases when Gig is around 0.03. The inapplicability is due to the strong interaction between droplet behavior (droplet heating and vaporization) and chemical kinetics (low and high temperature reaction) that were not inherent to description of Gig. To clarify the interaction, time scale analysis of these processes was performed for better complementation of the regime diagram characterized by Gig and Ta for various IGC modes.
对颗粒半径为 100～500 μm、体积分数为 0.075～0.35 的固定随机分布的颗粒群在 303 K与 1173K环境温度下的受力及相应的流场进行模拟.模拟工具为虚拟区域法.它采用统一形式的结构化网格描述颗粒与气体,并实现两相的相互作用,兼有较高的准确度与效率.相关结果显示,颗粒群在燃烧环境中形成的流场更稳定,这主要是由于气体在燃烧环境中的黏性更大,导致雷诺数更小.同时,颗粒群在燃烧环境中所受黏性力更大.在较低与较高的雷诺数下,颗粒群在燃烧环境中的曳力分别更大与更小.随着颗粒尺寸增大,颗粒群的燃烧强度与曳力均增大;随着颗粒体积分数增大,颗粒群的燃烧强度减小但是曳力增大.最后,本研究对于颗粒群的终端速度、曳力系数以及气-固动量交换系数提出了在燃烧环境中的修正.
我国早在远古时代就发现了燃烧现象,就是取火和用火.从 20 世纪 50 年代开始,由于能源、动力、航空航天、化工冶金等工程的迅速发展,我国开始了燃烧理论的研究.我国学者研究了着火理论,层流火焰传播、液滴燃烧和液雾燃烧.20 世纪 70 到 80 年代之间,我国开始了燃烧数值模拟的研究,包括湍流流动模拟、湍流燃烧模拟、两相湍流模拟和两相燃烧模拟.到目前为止,涵盖了雷诺平均模拟、大涡模拟和直接数值模拟.本文选取我国燃烧理论和数值模拟中一些有代表性的研究进行了历史性的回顾,目的是使年青学者对此有更好的了解.
在 Hencken 燃烧器平面扩散火焰的煤粉燃烧实验系统上测量了煤粉火焰不同高度处的烟气组分浓度分布,研究了 O2/CO2 气氛下不同热协流温度和氧气体积分数对 NO 生成与还原的影响.结果表明,当热协流温度从 1873K 降低至 1473K 时,NO 产率降低了 5%,而当氧气体积分数从 20%降低至 5%时,NO 产率降低了20%.通过 NO 生成动力学分析得到了挥发分氮氧化反应生成 NO 的活化能为 82.5 kJ/mol,得到的NO 生成速率有助于 MILD 富氧燃烧条件下煤燃烧氮化学模型改进的应用.同时,采用计算流体动力学(CFD)软件对高温低氧O2/CO2气氛下煤粉燃烧及NO生成进行了数值分析.通过与实验数据的对比,验证了数值模型的准确性.通过分离挥发分NO与焦炭NO对不同的NO生成与还原阶段进行分区,有助于了解挥发分氮和焦炭氮生成与还原的相互作用机制和定量分离挥发分NO与焦炭NO生成与还原.
燃烧在固体燃料内稳定传播的机理目前尚不明确.在预实验发现炭棒稳定燃烧存在锥形反应面的基础上,以柏木和榆树皮粉制得的细炭棒(2～7 mm)为研究对象,对反应锥形状和燃烧传播速度间关系进行了理论和实验分析.结果表明:反应锥长度正比于燃烧传播速度和扩散及动力阻力总和的乘积(l∝u·(Rtran+Rkin)).与圆管非预混气体贫燃燃烧的火焰长度与燃料体积流量间关系类似,细炭棒稳定燃烧的反应锥长度正比于燃料的质量流量.研究为进一步明确燃烧在固体燃料内的稳定传播提供了基础.
利用平准化电力成本的模型方法对掺氨燃烧技术的经济可行性进行了评估.对在大型燃煤电厂1000 MW 机组上应用掺氨燃烧技术和碳捕集与封存技术(CCS)两种减碳方案的经济竞争力进行了比较;并针对未来氨成本降低和碳价、煤价升高的趋势,比较了氨煤混燃和纯煤燃烧两种情况的经济成本来进一步论证零碳氨替代燃料减碳方案的可行性.针对结果提出相关建议,弥补了当前关于氨燃料经济性评估方面研究的不足,论证了零碳氨燃料的市场推广价值.
采用浸渍法分别将 CeO2、ZrO2 负载于 Cu-ZSM-5 催化剂中,通过催化剂活性评价系统研究了 CeO2、ZrO2 负载量对整体式 Cu-ZSM-5 催化剂 NOx转化率的影响规律,并采用 NO-TPD 方法分析了催化剂表面的 NOx吸附能力.此外,利用 FT-IR 和 SEM 技术探究了催化剂样品的抗老化能力.结果表明,添加 CeO2 或 ZrO2 有利于提升整体式Cu-ZSM-5 催化剂NOx转化率,其中 8%CeO2/Cu-ZSM-5 在 150～550℃温度范围内NOx转化率最高,但此催化剂表面晶粒在高温下易发生团簇,导致催化剂老化,催化活性下降.ZrO2 的添加可以有效稳固表面晶粒,进而改善催化剂的抗老化性能.
针对计算层析成像火焰三维重建,本文发展了一种新的迭代算法,乘型代数重建非局部平均滤波算法(MART-NLM),通过与现有迭代算法进行对比,发现MART-NLM具有更好的重建精度,可以有效抑制噪声和伪影,改善火焰锋面的重建质量;在存在5°角度误差及5%高斯噪声下仍能重建出火焰轮廓,具有较好鲁棒性.
以凹槽和凸台为研究对象,对具有局部构型的平板开展可燃特性研究,特别开展了火焰向下传播和熄灭实验.火焰传播分为两个阶段,初始阶段棱角处火焰传播速度比平面快,一段时间后,整个火焰锋面达到与棱角处火焰相同的传播速度.考虑棱角结构与圆柱表面火焰传播相似,将棱角等效成圆柱建立了火焰传播模型,可准确预测具有局部构型材料的火焰传播速度.棱角结构对可燃极限影响并不显著,局部最薄或最窄的尺度决定其极限氧气浓度.
在流动管平台上进行了接近发动机运行压力的氨气氧化实验,关注 N2O 的生成和消耗.压力为5.0 MPa,温度从 600～1250 K,当量比从 0.13～1.0.用近年来发表的氨气氧化的动力学模型开展模拟计算和动力学分析,对各模型在高压工况下对 N2O 的预测能力进行评估和分析.根据最新的计算结果调整 NH2 和 NO2 反应的分支比,并在 Stagni 模型上更新了相关反应的反应速率,添加了 N2O 缺失的反应路径.模型优化后在不同当量比下对N2O的预测能力均得到了提升.
