Experimental Study on Combustion Characteristics of Pulverized Coal under Enriched-oxygen Condition by Entrained Flow Reactor

Four different pulverized coals have been used to study the effects of oxygen concentration on combustion characteristics under different enriched-oxygen conditions by entrained flow reactor experiments. The results show that: with the increase of oxygen concentration, the ignition temperature of four coals greatly decreases and the low volatile coals decrease faster; with the increase of oxygen concentration, the ignition mode of pulverized coal has an obviously transformation from homogeneous ignition to heterogeneous ignition, and the corresponding oxygen concentrations are about 40% and 50%-60% respectively for bituminous coal and lignite, and both about 30% for lean coal and anthracite; with the increase of oxygen concentration, the optimal pulverized coal concentrations of bituminous coal and lignite increase firstly and then decrease, but for lean coal and anthracite, the optimal pulverized coal concentrations decrease slowly with the increase of oxygen concentration.

Effects of I-EGR and Pre-Injection on Performance of Gasoline Compression Ignition(GCI)at Low-Load Condition

Gasoline compression ignition(GCI)has been considered as a promising combustion concept to yield ultralow NOX and soot emissions while maintaining high thermal efficiency.However,how to improve the low-load performance becomes an urgent issue to be solved.In this paper,a GCI engine model was built to investigate the effects of internal EGR(i-EGR)and pre-injection on in-cylinder temperature,spatial concentration of mixture and OH radical,combustion and emission characteristics,and the control strategy for improving the combustion performance was further explored.The results showed an obvious expansion of the zone with an equivalence ratio between 0.8∼1.2 is realized by higher pre-injection ratios,and the s decreases with the increase of pre-injection ratio,but increases with the increase of i-EGR ratio.The high overlap among the equivalentmixture zone,the hightemperature zone,and the OH radical-rich zone can be achieved by higher i-EGR ratio coupled with higher preinjection ratio.By increasing the pre-injection ratio,the combustion efficiency increases first and then decreases,also achieves the peak value with a pre-injection ratio of 60%and is unaffected by i-EGR.The emissions of CO,HC,NOX,and soot can also be reduced to low levels by the combination of higher i-EGR ratios and a pre-injection ratio of 60%.

An Experimental Investigation on Low Load Combustion Stability and Cold-Firing Capacity of a Gasoline Compression Ignition Engine

Gasoline compression ignition (GCI) is one of the most promising combustion concepts to maintain low pollutant emissions and high efficiency. However, low load combustion stability and firing in cold-start operations are two major challenges for GCI combustion. Strategies including negative valve overlap (NVO), advanced injection strategies, fuel reforming, and intake preheating have been proposed in order to solve these difficulties;however, the cold start is still an obstacle. The objective of this work is to study effective methods to achieve GCI engine cold start-up. This work combines NVO, in-cylinder fuel reforming, and intake preheating to achieve quick firing under cold-start conditions and the subsequent warmup conditions. The results show that start of injection (SOI) during the intake stroke yields the best fuel economy, and injection during the compression stroke has the potential to extend the low load limit. Furthermore, SOI during the NVO period grants the ability to operate under engine conditions with cold intake air and coolant. With highly reactive products made by in-cylinder fuel reforming and fast heat accumulation in the combustion chamber, the NVO injection strategy is highly appropriate for GCI firing. An additional assisted technical method, such as intake preheating, is required to ignite the first firing cycle for a cold-start process. With the combination of NVO, in-cylinder fuel reforming, and intake preheating, the GCI engine successfully started within five combustion cycles in the experiment. After the firing process, the engine could stably operate without further intake preheating;thus, this method is appropriate for engine cold-start and warm-up.

Effect of Curing Conditions on the Hydration and Performance of CFBC Ash Cementitious System

Circulating fluidized bed combustion （CFBC） ash can be used as supplementary cementitious material for concrete production for its high pozzolanic activity. We investigated the effect of curing conditions on the hydration and performance of CFBC ash-Portland cement system （30： 70, by mass） including hydration products, paste microstructure, linear expansion ratio, chemically combined water content and compressive strength. The results show that tobermorite rather than ettringite is generated under the condition of autoclaved curing. The expansion and mortar strength of the system cured in water is higher than those cured in air at a given age, and the strength and bulk volume may retract under the condition of air curing. In addition, autoclaved curing facilitates the increase of strength gain at early curing ages （the increase rate lowers down in the following ages） and the improvement of system volume stability. It is suggested that sufficient water is necessary for the curing of CFBC ash cementitious system, and autoclaved curing may be considered where volume stability is a primary concern.

Experimental and mechanistic study on chemical looping combustion of caking coal

Under high-temperature batch fluidized bed conditions and by employing juye coal as the raw material,the present study determined the effects of the bed material,temperature,OC/C ratio,steam flow and oxygen carrier cycle on the chemical looping combustion of coal.In addition,the variations taking place in the surface functional groups of coal under different reaction times were investigated,and the variations achieved by the gas released under the pyrolysis and combustion of Juye coal were analyzed.As revealed from the results,the carbon conversion ratio and rate were elevated significantly,and the volume fraction of the outlet CO_(2)remained more than 92%under the oxygen carriers.The optimized reaction conditions to achieve the chemical looping combustion of Juye coal consisted of a temperature of 900℃,an OC/C ratio of 2,as well as a steam flow rate of 0.5 g·min^(-1).When the coal was undergoing the chemical looping combustion,volatiles primarily originated from the pyrolysis of aliphatic-CH_(3)and-CH_(2),and CO and H_(2)were largely generated from the gasification of aromatic carbon.In the CLC process,H_(2)O and CO_(2)began to separate out at 270℃,CH4 and tar began to precipitate at 370℃,and the amount of CO_(2)was continuously elevated with the rise of the temperature.

Role of Heating Condition in Polyethylene Behaviors under Nitrogen and Air Atmosphere

Recycle of plastic waste is an indisputable means to alleviate both environment and energy crisis.In this work,effects of heating condition on polyethylene behaviors in nitrogen and air were studied.It was observed that polyethylene behavior was a single step in nitrogen,while the multiple steps occurred in air.According to the weight loss and heat flow curves,polyethylene behaviors in air were divided into three regions:low-temperature(<340 ℃),middle-temperature(340 – 380 ℃) and high-temperature(> 380 ℃) regions.Kinetic analysis revealed that the partial oxidization took the dominance in the low-temperature region,which seldom formed CO and CO_(2);the combustion took the dominance in the middle-temperature region,which was positive to the formation of CO and CO_(2);the pyrolysis was initiated and enhanced in the high-temperature region,which inhibited the formation of CO and CO;.According to the kinetic simulation,a synergistic effect between the pyrolysis and combustion was proposed to account for the acceleration of polyethylene conversion.This work may provide useful information about polyethylene behaviors under heating condition,and help to design and optimize plastic waste incineration process.

傅里叶变换离子回旋共振质谱技术在稠油高低温氧化评价中的应用

为了认识稠油开发过程中低温氧化与高温氧化阶段原油变化规律,利用静态氧化釜开展稠油的高低温氧化实验,借助傅里叶变换离子回旋共振质谱分析技术对高低温氧化前后的原油分子量及O、N、S杂原子化合物特征开展研究,结果表明:原油低温氧化阶段分子量分布特征与原样相似,相对分子量分布范围在200~750,整体呈平缓状单峰型分布,高温氧化阶段分子量分布范围前移,呈明显的前峰单峰型分布;杂原子化合物中的O元素在低温氧化阶段主要以无环的饱和二元酸形式存在,在高温氧化阶段受环化、芳构化及脱甲基作用的影响,伴随着侧链烷基及杂原子基团的断裂和芳构化过程,造成原油中杂原子化合物向着碳数更小、双键当量(double bond equivalents,DBE)值更低的方向演化。该研究探索了温度与原油结构及化学组成之间的关系,对于指导稠油开发现场具有重要意义。

燃煤循环流化床锅炉掺烧污泥应用研究进展

利用循环流化床锅炉合理处置产量大且含有有害物质的污泥,可使其烟气中污染物排放浓度达标,因而燃煤循环流化床锅炉掺烧污泥具有广阔的应用前景。从污泥的掺烧现状、掺烧机理、燃烧工况、存在问题以及优化方案等方面对燃煤循环流化床锅炉掺烧污泥进行综述研究。煤炭与污泥混燃可实现燃料特性互补,消除单一燃料的负面特性。结合国内外燃煤循环流化床锅炉掺烧污泥相关工艺,指出现阶段我国污泥掺烧对燃烧效率、锅炉运行以及烟气污染物排放的影响,并提出优化工况的具体措施。综合认为,燃煤循环流化床锅炉掺烧污泥可实现污泥的减量化、无害化、资源化处置,需从污泥预处理、锅炉系统优化、数值模拟等多角度出发,进行系统优化设计和改造,以确保混合燃料在炉内高效燃烧、达标排放。

基于卷积神经网络CNN的示功图智能分析方法

针对目前对船舶柴油机示功图的分析评估大多通过人工进行,其结果依赖于轮机管理人员的业务能力与经验,存在不确定性的问题,构建了一种基于卷积神经网络的示功图智能分析监测模型.该模型包括5层卷积神经网络和2层全连接神经网络,采用多种优化算法并使用GPU进行硬件加速.训练与实验结果表明,示功图训练精度为99.5%,识别精度为95.9%,平均识别时间为0.032 s,验证了该模型的可靠性和准确性,可以对示功图进行智能分析,满足柴油机燃烧工况智能监测的精度要求,为实现船舶动力系统智能化管理提供支持.

基于KPCA-FCM工况精简的机组燃烧优化

针对深度调峰下运行工况频繁变动使锅炉燃烧优化参数调整难度增大的问题,提出了一种基于KPCA-FCM工况精简的燃烧优化方法。首先对锅炉实际历史运行数据提取稳态工况后,通过核主成分分析法(KPCA)进行降维,选取贡献率较大的运行参数利用模糊聚类算法(FCM)进行分析完成工况划分,实现对工况的精简。然后对不同的燃烧工况匹配对应的工况簇,调整燃烧参数到该类的最佳运行参数。为了验证该方法的合理性,采用最小二乘支持向量机辨识锅炉燃烧热效率模型。以高低两个工况区间为例进行仿真验证,结果表明提取到的最优运行参数目标值可以使锅炉热效率最高提升0.2%。因此,提出的工况精简方法可有效选取最优运行目标值,为现场运行人员调整运行参数提高锅炉效率提供了合理的数据参考。

分区参数对超声速湍流燃烧动态分区火焰面模拟的影响

文章基于动态分区火焰面模型(DZFM)和改进延迟分离涡(IDDES)湍流模型对DLR中心支板稳焰的超声速燃烧室进行数值模拟.对无反应状态燃烧室的模拟准备复现了燃烧室内复杂的波系结构以及中心射流失稳发展过程,燃烧状态下的模拟结果较好地捕捉了火焰推举、OH基团以及平均温度等火焰结构特征,由此验证了所采用数值模拟方法的适用性.此外,由反应状态标量(OH基)在混合分数空间中的分布可知,反应标量与混合分数在全场内不满足强相关性.通过增加流向坐标、马赫数以及燃烧热释放速率作分区参数可显著抑制反应状态标量在混合分数空间内的条件脉动,其中热释放速率的作用最显著.进一步对比采用不同多参数分区的DZFM模型所得火焰结构,发现对于处于预混燃烧状态的支板尾迹区以及高雷诺数剪切层区域火焰,采用包含燃烧热释放速率、流向坐标以及混合分数作为分区指标的三参数分区DZFM模型可显著提高模型的准确性.

超低负荷下660MW塔式锅炉低氧工况下燃烧过程数值模拟研究

针对锅炉在超低负荷下运行时通常过量空气系数较高,导致NO_(x)浓度较高的问题,采用数值模拟的方法研究锅炉在低氧工况下不同给煤位置的燃烧特性和NO_(x)排放特性.结果表明:50%与30%汽轮机热耗率验收(THA)工况下采用相同磨煤机组合运行时,速度、烟气组分、温度分布规律类似,进粉位置上移导致主燃区上部温度升高且分布更均匀,切圆半径逐渐减小,燃尽风消旋作用使混合增强,因此有利于燃烧的稳定.2台磨煤机运行相比3台局部煤粉浓度更大,主燃区的燃烧温度更高,导致更多NO_(x)生成;30%THA工况下,当下层磨煤机运行时冷灰斗附近温度较高;低氧工况下,NO_(x)质量浓度最高值低于360mg/m^(3),当负荷从50%THA降低至30%THA,炉膛出口NO_(x)浓度降低20.8%.

Effect of using borax decahydrate as nanoparticles additive in blends of spirulina biodiesel/diesel on combustion characteristics and knock intensity

In this extensive investigation,the impact of borax decahydrate as a fuel additive in a diesel single-cylinder engine was rigorously examined.Borax decahydrate was introduced at concentrations of 5,15,25 and 35 g in 500 ml of biodiesel,forming five unique fuel mixtures with conventional diesel:90%diesel+10%spirulina biodiesel(SB10),SB10+1 g borax decahydrate(SB10B1),SB10+3 g borax decahydrate(SB10B3),SB10+5 g borax decahydrate(SB10B5)and SB10+7 g borax decahydrate(SB10B7).The investigation encompassed four diverse loading conditions and yielded insightful findings.Notably,at full load,SB10B3 exhibited a higher cylinder peak pressure than diesel,reaching 69.25 bar.Heat release rate profiles demonstrated superior efficiency for SB10 at 50%load,with a cumulative heat release rate of 950 J/°CA,which is lower than the 1050 J/°CA of diesel.Knock intensity(KI)evaluations revealed that,although SB10 and SB10B1 exhibited higher KI than diesel at full load due to elevated peak pressure,SB10B7 showed no knocking across all loads,indicative of reduced in-cylinder combustion.This meticulous numerical analysis emphasizes the potential of borax decahydrate as a catalyst and enhancer,providing valuable insights into the combustion dynamics of these alternative fuel blends and their viability for sustainable and efficient engine performance.In summary,out of all the blends,SB10B3 could be a potential diesel fuel replacement fuel for compression-ignition engines.

基于仿真机理和改进回归决策树的二噁英排放建模

城市固废焚烧(Municipal solid waste incineration,MSWI)过程是“世纪之毒”二噁英(Dioxin,DXN)的重要排放源之一.截止目前为止,DXN的演化机理和实时检测仍是尚未解决的难题.现有研究主要基于离线化验数据构建数据驱动模型,DXN的检测未有效结合燃烧过程机理.针对该问题,本文提出基于仿真机理和改进线性回归决策树(Linear regression decision tree,LRDT)的DXN排放建模.首先,采用基于床层固废燃烧模拟软件FLIC(Fluid dynamic incinerator code)和过程工程先进系统软件(Advanced system for process engineering Plus,Aspen Plus)耦合的数值仿真模型,获取蕴含多运行工况的虚拟机理数据;接着,利用虚拟机理数据构建基于改进LRDT的CO_(2)、CO和O_(2)燃烧状态表征变量模型;然后,以真实CO_(2)、CO、O_(2)作为输入和以DXN真值作为输出,构建多入单出LRDT的过程映射模型(Process mapping model,PMM),再利用该模型进行半监督学习和结构迁移得到机理映射模型1(Mechanism mapping models1,MMM1);最后,通过结构增量学习获得基于半监督迁移学习的MMM2模型.在实验室的半实物平台和北京某MSWI厂的边侧验证平台对所提方法进行了工业应用验证.实验结果证明了所提方法与研发的软测量系统可有效实现二噁英排放浓度在线检测.

燃烧条件对准颗粒CO排放影响的数值模拟

在烧结过程中料层不同位置温度、氧气浓度、空气流速等条件存在差异巨大,为探究烧结过程中燃烧条件对烧结准颗粒CO生成行为的影响,利用数值模拟的方法研究了不同准颗粒烧结过程。通过FLUENT软件,以多孔介质模型为基础,结合能量方程模型、组分输运方程模型、燃料燃烧以及污染物排放的反应动力学模型,以自定义功能(UDF)对各方程模型的源项进行定义与修正,建立了4种不同结构铁矿石烧结准颗粒,即S′型(裸露型)、S型(被覆型)、C型(外包型)和P型(球团型)的燃料燃烧过程模型,阐述了各种因素对烧结准颗粒中燃料燃烧行为及污染物排放特性的影响规律。模拟结果显示,准颗粒烧结过程CO排放规律随着燃烧条件的变化而发生改变,不同的反应条件对准颗粒内焦炭的燃烧速率有不同影响。当环境温度从1200 K升至1400 K时,准颗粒的CO排放总量下降了2%左右。较高的环境风速与氧气浓度都使准颗粒的CO排放浓度峰值增加,同时增加了焦炭的未完全燃烧程度。

优化城市污泥与棉秆掺混燃烧条件的正交实验研究

以发热量为评价指标,通过正交实验优化城市污泥、棉秆掺混燃烧条件。结果表明,影响污泥混合物发热量的主次因素为棉秆掺混比>搅拌时间>掺混粒径,最佳掺混条件为棉秆掺混40%,搅拌时间5 min,掺混粒径0.075 mm。最佳掺混条件下,城市污泥着火、燃尽温度显著降低,发热量提高了34%,综合燃烧特性指数增大了3.97倍,活化能降低了12.74 kJ/mol,燃烧过程中污泥、棉秆几乎全程处于正向促进作用阶段。

加热炉工况诊断技术研究

加热炉是油田油气集输的主要耗能设备,为全面、及时、准确掌握加热炉的工况,在绘制加热炉工况诊断图版的基础上,设计安装炉况优化装置掌握运行工况,安装内窥式火焰监视系统掌握燃烧工况,形成加热炉经济运行标准及操作规范,为管理人员提供评价指标,指导操作人员合理调控加热炉运行参数,实现加热炉高效、经济运行。

煤在贫氧条件下升温过程中的自由基反应研究

针对煤体低温氧化引发煤自燃灾害的问题,通过电子自旋共振波谱仪测定了煤样在不同氧气浓度下升温过程中自由基浓度、g因子和线宽的变化,研究了煤样在贫氧条件下的自由基反应特征。实验结果表明,氧化初始阶段3种煤样原生自由基浓度的相对大小为无烟煤>烟煤>褐煤,而通过计算得出在0%、10%和21%氧气浓度下自由基浓度增长率相对大小为褐煤>烟煤>无烟煤,这表明褐煤在贫氧条件下的自由基反应更剧烈。3种煤样的g因子随温度的升高而增大,且相同温度下g因子与氧气浓度呈正比,与煤样的变质程度呈反比。在氧化过程中,褐煤的线宽高于烟煤和无烟煤,但褐煤线宽的降低幅度小于烟煤和无烟煤,3种煤样的线宽受氧气浓度的影响均较小。实验得到不同变质程度煤在贫氧条件下的自由基反应特征,对研究煤自燃的自由基反应机理具有重要意义。

直流无刷风机在燃气热水器上的风量自适应控制研究

文章提出一种采用直流无刷风机自学习适应控制的方式,以实时判断热水器的工况随状态改变并自动适应改变燃烧工况所需的风量,避免烟气超标排放。

基于变频压缩机绕组测温技术的R32空调系统爆炸实验研究

近年来,国内外已发生多起R32可燃制冷剂空调由于安装维修操作不当造成高压侧堵塞导致压缩机爆炸的安全事故。研究以变频压缩机绕组测温技术为依托,通过实验模拟还原R32空调系统在极端条件下的爆炸场景,获取压缩机发生爆炸瞬间的电机绕组和排气温度。基于绕组测温技术拟合出绕组温度推算值与排气温度实测值的温差ΔT参数,证明ΔT参数可表征在极端危险条件下运行的压缩机发生爆炸的危险程度,为可燃制冷剂空调系统的安全保护控制提供关键的判定指标。