轻烃燃气着火延迟特性研究

轻烃燃气是一种新型燃气,产地不同会造成主要成分戊烷异构体含量不同,着火延迟时间是描述燃烧特性的重要参数也是验证动力学机理的重要依据,本文使用CHEMKIN PRO模拟研究温度1000～1800K、压力1～20atm、当量比0.5～2.0范围内正戊烷异戊烷不同掺混比对着火延迟时间的影响,采用生成速率分析法（ROP）和敏感性分析法探究正戊烷异戊烷掺混比对着火延迟时间的影响机理。结果表明：温度增加会减小着火延迟时间;在本文研究压力范围内,掺混比影响着火延迟时间趋势较为复杂;从贫燃料区至富燃料区,当量比增加会减小着火延迟时间。异构体中随着正戊烷含量减小着火延迟时间增加,掺混比的影响随着温度、压力增加而减小;OH是戊烷反应消耗脱氢的主要自由基,正戊烷易与OH、HO2反应脱氢,异戊烷易与H、O反应脱氢,当正戊烷含量减少时,OH和HO2消耗减少、H和O消耗增加;反应过程中的主要自由基R（C5H11）基和QO（C5H10O）基含量随着正戊烷含量减小而减小;温度为1000K时,正戊烷敏感性系数最大的反应促进着火减小着火延迟时间,掺混异戊烷后敏感性系数最大的反应抑制着火增加着火延迟时间,当温度为1800K时,敏感性系数最大的反应均为R1,其他反应敏感性系数相对较小,掺混比对着火延迟时间的影响较小。     

柴油在O_2/CO_2氛围下燃烧特性模拟和试验

为研究柴油在O_2/CO_2氛围下的着火特性,提出了柴油表征燃料(正庚烷)在65%O_2/35%CO_2氛围下的着火延迟时间模型.该模型考虑到了O_2和CO_2对燃烧反应速率的影响,得到了温度和着火延迟时间的关系,推导出了着火延迟时间的计算公式,运用稳定状态法对正庚烷的基元反应进行缩减,计算了正庚烷在空气和65%O_2/35%CO_2氛围下的着火延迟时间;搭建了定容燃烧弹可视化试验系统,对柴油在空气和65%O_2/35%CO_2氛围下的着火过程进行了可视化研究;对试验所得的着火延迟时间、火焰浮起长度和燃烧压力变化进行了比较分析.结果表明:该着火延迟时间模型可以很好地模拟柴油在65%O_2/35%CO_2氛围下的着火过程,柴油在此氛围下的着火延迟时间变化非常明显,比在空气氛围下缩短了50%;柴油在此氛围下的火焰浮起长度短于在空气氛围中的;喷油压力的改变会对柴油的着火延迟时间及定容燃烧弹内的最大燃烧压力产生影响.     

添加生物质气化气的选择性非催化还原研究

提出利用生物质气化气为选择性非催化还原技术（SNCR）反应的添加剂,并进行相应的反应动力学计算。计算结果表明生物质气化气作为添加剂可以提高低温条件下SNCR反应的脱硝效率。生物质气化气主要成分为H₂、CH₄和CO,其中H₂和CH₄对温度窗的作用明显,CO的效果较小。各种气体成分主要通过促进OH基元生成来促进相对较低温度下脱硝反应过程的进行。     

低氧再燃条件下煤粉均相着火温度的测量

在一维炉试验台上研究了煤粉颗粒群在低氧浓度再燃条件下的均相着火规律.结果表明:在低氧浓度下(＜10% 体积分数),煤粉均相着火呈现出反应不剧烈、不连续的特点;氧浓度对于煤粉均相着火温度的影响近似成指数变化关系,即氧浓度越低,均相着火温度越高;在一定范围内,氧浓度越低,煤粉均相着火延迟时间越长;煤粉均相着火温度随粒径减小而提高,近似成线性关系;不同氧浓度前提下,粒径对着火温度的影响作用不同.     

Oxy-steam气氛下低热值燃气燃烧特性研究

利用Fluent软件对高炉煤气在Oxy-steam气氛下的燃烧进行数值模拟,分析了水蒸气体积分数对高炉煤气燃烧温度、炉内温度分布、烟气组分体积分数、NOx体积分数以及烟黑体积分数的影响.结果 表明:在Oxy-steam气氛下燃烧时,由于水蒸气比热容较N2更高,且存在大量的OH和H基团,高炉煤气的最高燃烧温度从1350 K下降至1290 K;与O2/N2气氛下的燃烧相比,在Oxy-steam气氛下燃烧时炉内温度分布更加均匀,CO燃烧更完全,炉膛出口处NOx和烟黑的体积分数均迅速减小;随着水蒸气体积分数的不断增大,炉膛出口烟气流速从0.55 m/s减小至0.505 m/s;与在O2/N2气氛下的燃烧相比,在Oxy-steam气氛下炉膛出口H2和CH4摩尔分数略增大.     

NH3/DME混合物着火特性试验与数值模拟研究

为了探究NH₃/DME混合物的着火特性，利用激波管测量了初始温度T=1 250～1 800 K、当量比Φ=0.5～2.0、DME掺混比X_DME=0～1.0、压力p=1 MPa条件下NH₃/DME混合物的着火延迟时间。基于测量的试验数据，更新了Issayev等人构建的NH₃/DME燃烧反应动力学模型的部分基元反应，更新后的模型表现出对NH₃/DME着火延迟时间的良好预测。在此基础上，进一步开展了NH₃/DME着火特性值模拟研究。结果表明：NH₃/DME高温着火延迟时间随二甲醚(DME)掺混比的增加呈指数降低；NH₃/DME的着火延迟时间随当量比的增加先降低后升高，且不同温度下达到最低着火延迟时间的当量比不同；中低温下NH₃/DME的着火延迟时间随初始温度的变化规律与高温下不同，呈现出明显的负温度系数(NTC)现象。     

烟气汞液相脱除试验及传质-反应动力学研究

为了探究Hg0与KMnO4的反应机理,利用鼓泡反应器考察了模拟烟气Hg0在不同条件下的脱除率,分析了KMnO4溶液初始浓度、pH值和反应温度对Hg0脱除率的影响,并进行了传质-反应动力学计算.结果表明:提高KMnO4溶液初始浓度和降低pH值,均可提高Hg0的脱除率;反应温度升高不利于Hg0的脱除;Hg0与KMnO4的反应为复杂的气液传质反应过程,提高KMnO4溶液初始浓度,反应增强因子E和Hg0的气液相传质系数比KG/kL增大,表明化学反应对传质吸收的影响增大且液膜阻力减小,从而Hg0脱除率提高;提高反应温度,Hg0的气液相传质系数比KG/kL减小,表明反应温度升高,增大了液膜阻力,不利于反应进行,导致Hg0脱除率降低.     

高温还原性气氛条件氨还原NOx机理研究

在一维管式炉上进行高温下NH₃还原NO_x特性实验研究，并基于化学反应动力学模型对实验工况进行模拟计算，分析在近零氧工况下NH₃/NO_x反应过程中关键基元反应及主要活性基团变化规律，探究高温下氨还原NO_x反应机理。结果表明：在无氧或者氧气体积分数为0.1%工况时，反应温度窗口明显向高温偏移，NH₃/NO_x还原反应进行的拐点温度为1 100℃,反应过程中关键的基元反应为NH₂/NO_x还原反应，温度对这组基元反应的一阶敏感性系数决定了最佳反应温度窗口；OH与NH₂自由基是反应中重要的活性基团，其浓度的积累也影响反应温度窗口，无氧工况下最佳反应温度窗口为1 300～1 400℃;无氧工况下NH₂自由基主要由3条反应路径还原NO_x,NH与NNH自由基是最重要的中间产物，而HNO的存在会造成NO_x质量浓度增加。     

氨气与甲烷混合气自燃过程的化学动力学研究

在当量比φ=0.5、压力为2～7 MPa以及温度从930 K到1 140 K的条件下，用快速压缩机研究氨气(NH₃)和甲烷(CH₄)混合气的着火延迟时间，其中CH₄占总燃料的摩尔分数分别为0、5%、10%及50%．另外，在φ为1.0和2.0的条件下对掺入10%CH₄的混合气进行着火延迟时间测试．CH₄对NH₃的着火过程具有非常明显的促进作用，随着CH₄占总燃料的比例越来越高，混合气的着火延迟时间缩短，同时CH₄对着火的促进作用趋于平缓．含10%CH₄的NH₃的着火延迟时间在φ为0.5和1.0的条件下变化很小，而当φ=2.0时着火延迟时间增加约50%．利用试验数据对6种不同的NH₃氧化机理进行了验证，所开发的机理预测着火延迟时间最为准确，除了在最高温度，CH₄摩尔分数为50%时试验与计算差异达到了50%，其他所有条件下机理的预测...     

微型内燃机工况下C1–C4烷烃着火延迟数值模拟

燃料着火延迟时间对采用蓄热自着火方式的微型内燃机非常重要。利用Chemkin-Pro软件,分别对甲烷、乙烷、丙烷和正丁烷空气混合气在微型内燃机运行工况下进行着火延迟时间模拟计算,探究初始温度（500 K ~ 1 000 K）、压力（1~ 10atm）和当量比（0.6 ~ 1.2）对着火延迟时间的影响。同时分析了微型内燃机扫气不尽的尾气残留组分（N2、CO2和H2O）对正丁烷着火延迟时间的影响。结果表明：在四种燃料中,正丁烷的低温着火延迟特性最佳,是一种适合于采用蓄热自着火方式的微型内燃机燃料;初始温度、压力的提高和当量比的增大有利于燃料着火延迟时间的缩短;尾气残留使得燃料着火延迟时间变长,着火延迟特性变差,尾气各组分的热效应和基元反应对燃料着火延迟有着不同的影响机制。     

An experimental investigation of ethylene/O2/diluent mixtures: Laminar flame speeds with preheat and ignition delays at high pressures

The atmospheric pressure laminar flame speeds of premixed ethylene/O₂/N₂ mixtures were experimentally measured over equivalence ratios ranging from 0.5 to 1.4 and mixture preheat temperatures varying from 298 to 470 K in a counterflow configuration. Ignition delay measurements were also conducted for ethylene/O₂/N₂/Ar mixtures using a rapid compression machine at compressed pressures from 15 to 50 bar and in the compressed temperature range from 850 to 1050 K. The experimental laminar flame speeds and ignition delays were then compared to the computed values using two existing chemical kinetic mechanisms. Results show that while the laminar flame speeds are reasonably predicted at room temperature conditions, the discrepancy becomes larger with increasing preheat temperature. A comparison of experimental and computational ignition delay times was also conducted and discussed. Sensitivity analysis further shows that the ignition delay is highly sensitive to the reactions of the vinyl radical with molecular oxygen. The reaction of ethylene with the HO₂ radical was also found to be important for autoignition under the current experimental conditions.     

合成气自点火延迟特性分析

合成气的自点火延迟时间是预混器设计的关键参数之一,合成气富含大量的H2,因此自点火延迟时间要比常规燃料短很多,预混段过长将会导致自点火的危险。目前燃气轮机条件下的合成气自点火延迟的实验数据仍然很少,且尚未出现一种可以准确预测低温高压下合成气自点火延迟时间的化学反应机理。主要分析了温度、压力、当量比、氧含量、氢含量五大因素对自点火延迟时间的影响,并且修正了GRI3．0、Song等机理来模拟低温反应中的扰动因素影响,得到了较好的结果,同时还在Walton经验公式的基础上做了一定修改,使之与目前存在的数据更为接近。     

1-Butanol ignition delay times at low temperatures: An application of the constrained-reaction-volume strategy

Ignition delay times behind reflected shock waves are strongly sensitive to variations in temperature and pressure, yet most current models of reaction kinetics do not properly account for the variations that are often present in shock tube experiments. Particularly at low reaction temperatures with relatively long ignition delay times, substantial increases in pressure and temperature can occur behind the reflected shock even before the main ignition event, and these changes in thermodynamic conditions of the ignition process have proved difficult to interpret and model. To obviate such pressure increases, we applied a new driven-gas loading method that constrains the volume of reactive gases, thereby producing near-constant-pressure test conditions for reflected shock measurements. Using both conventional operation and this new constrained-reaction-volume (CRV) method, we have collected ignition delay times for 1-butanol/O₂/N₂ mixtures over temperatures between 716 and 1121 K and nominal pressures of 20 and 40 atm for equivalence ratios of 0.5, 1.0, and 2.0. The equivalence ratio dependence of 1-butanol ignition delay time was found to be negative when the oxygen concentration was fixed, but positive when the fuel concentration was held constant. Ignition delay times with strong pre-ignition pressure increases in conventional-filling experiments were found to be significantly shorter than those where these pressure increases were mitigated using the CRV strategy. The near-constant-pressure ignition delay times provide a new database for low-temperature 1-butanol mechanism development independent of non-idealities caused by either shock attenuation or pre-ignition perturbations. Comparisons of these near-constant-pressure measurements with predictions using several reaction mechanisms available in the literature were performed. To our knowledge this work is first of its kind that systematically provides accurate near-constant-enthalpy and -pressure target data for chemical kinetic modeling of undiluted fuel/air mixtures at engine relevant conditions.     

Shock tube studies on ignition delay and combustion characteristics of oxygenated fuels under high temperature

A comparative study on ignition delay time and combustion characteristics of four typical oxygenated fuel/air mixtures of dimethyl ether (DME), diethyl ether (DEE), ethanol and E92 ethanol gasoline was conducted through the chemical shock tube. The fuel/air mixtures were measured under the ignition temperature of 1100 to 1800 K, initial pressure of 0.3 MPa and the equivalence ratios of 0.5, 1.0 and 1.5. The experimental results show that the ignition delay time of these four oxygenated fuels satisfies the Arrhenius relation. The reaction H + O₂ = OH + O has a high sensitivity in four fuel/air mixtures during high-temperature ignition, which makes the ignition delay lengthen with the increase of the equivalence ratios. By comparing the ignition delay of four fuels, ether fuels have excellent ignition performance and ether functional group has better ignition promotion than hydroxyl group. Moreover, the carbon chain length also significantly promotes the ignition. Due to the accumulation of a large number of active intermediates and free radicals during the long ignition delay time before ignition, the four fuels all have intense deflagration and generate the highest combustion peak pressure at the relatively low ignition temperature (1150-1300 K). For DME, DEE and ethanol, due to the high content of oxygen in their molecules, the combustion peak pressure and luminous intensity increased with the equivalence ratio, and the combustion is intense after ignition. E92 ethanol gasoline with low oxygen content has a lower combustion peak pressure and a longer combustion duration than the other three fuels, and its highest combustion peak pressure appears in the stoichiometric ratio. The combustion process of E92 ethanol gasoline is more oxygen-dependent than the other three fuels.     

基于铁矿石载氧体的生物质化学链气化机理研究

在单批次进料小型流化床上,以稻壳为生物质燃料,研究了床料、气化温度、水蒸气体积分数以及载氧体载氧量与生物质含碳量的摩尔比(O/C)对生物质化学链气化反应特性的影响,并考察了铁矿石的长期交替氧化还原过程中的反应特性,分析了在小型流化床,水蒸气气氛气化条件下,铁矿石载氧体在反应过程中主要的反应以及反应后的铁矿石的床料变化。研究表明:在载氧体条件下,生物质的碳转化率显著增大,随着反应温度的升高,合成气中的H_2和CO的体积分数也相应升高。在温度不变情况下,随着水蒸气比例的升高,CO_2和H_2的体积分数显著上升。伴随着O/C摩尔比的升高,CO和H_2均显著下降。因此,在不同的反应条件下,铁矿石在生物质化学链气化过程中对反应速度、合成气比例等均有明显的作用,对研究生物质的综合利用具有一定的意义。     

Municipal Solid Waste Leachates Destruction and Metals Recovery by Supercritical Water Oxidation

Municipal solid waste leachate dissolved with nitrates of Cr, Pb, and Cu was investigated using a supercritical water oxidation process in this study. The destruction efficiency of chemical oxygen demand increased with the higher temperature and longer reaction time. A first-order expression applied for chemical oxygen demand was determined with a pre-exponential factor of 318 s^–1 and activation energy of 58 kJ/mol. Recovery efficiency of Cr, Pb, and Cu from initial solution into solid product increased with the higher temperature and longer reaction time. X-ray diffraction of solid products showed that the metal species were found to be Cu₂O, HCrO₂, and CaCO₃ at temperature 400°C, while the structure were identified as CuO, Cr₂O₃, PbCrO₄, and CaCO₃ at temperature 500°C.     

Fe2O3为载氧体的煤/秸秆化学链燃烧循环特性研究

对煤、秸秆与Fe2O3以不同质量掺混比混合后化学链燃烧过程中载氧体还原/再生的多循环反应特性进行了研究,重点分析了固体燃料带入的灰分对化学链反应速率的影响以及秸秆的掺入对化学链反应的改善.结果表明：载氧体Fe2O3质量掺混比的增大有利于化学链反应的进行,燃烧起始反应温度降低;Fe2O3作为载氧体受灰分积累的影响较大,其可持续循环能力较差;煤中掺入秸秆改善了煤的化学链燃烧特性,提高了燃烧反应速率和载氧体的再生反应速率.     

Experimental study on ignition and combustion of coal-rice husk blends pellets in air and oxy-fuel conditions

The ignition and combustion characteristics of anthracite-rice husk (AC-RH) and bituminous coal-rice husk (BC-RH) pellets were investigated in a vertical heating tube furnace under different experimental condition, for gas temperature (873 K–1073 K) and under air and different oxygen concentration (21–70%) in CO₂/O₂ atmosphere. The investigation of the ignition and combustion characteristics focused on ignition mechanism, ignition delay, ignition temperature and combustion process. AC-RH pellets had two ignition mechanism in CO2/O2 atmosphere: homogeneous ignition of volatile and heterogeneous ignition of char. Heterogeneous ignition region decreased while homogeneous ignition increased as rice husk blending ratio increased in oxygen concentration-gas temperature plane. Only homogeneous ignition was observed when rice husk blending ratio was 30%. As for BC-RH pellets, only homogeneous ignition occurred in all experimental conditions. The effect of the rice husk blending on the anthracite was more pronounced than the bituminous coal for ignition mechanism. As oxygen concentration increased, a significant reduction in ignition delay and ignition temperature was observed at low rice husk blending ratio and low gas temperature. but at 1073 K, high oxidizer temperature weakened the effect of biomass blending and oxygen concentration on ignition delay and ignition temperature. Meanwhile, at 20% and 30% rice husk blending ratio, it also weakened the effect of oxygen concentration and oxidizer temperature on ignition delay and ignition temperature. In contrast, blending ratio had a more significant effect on ignition behavior. The replacement of N₂ by CO₂ at the same oxygen concentration contributed to an increase in ignition delay time and internal ignition temperature, which suppressed the ignition behavior. Different ignition mechanisms corresponded to different combustion processes.     

Using chemical looping gasification with Fe2O3/Al2O3 oxygen carrier to produce syngas (H2+CO) from rice straw

The chemical looping gasification of rice straw using Fe₂O₃/Al₂O₃ as oxygen carrier was studied at reaction time of 5–25 min, steam-to-biomass (S/B) ratio of 2.0–4.8, reaction temperature of 750–950 °C, and oxygen carrier-to-biomass of 1.0. The gasification can be regarded completed in 20-min reaction. There exist an optimal S/B ratio of 2.8 and reaction temperature of 900 °C leading to maximum performances yielded are 1.22 Nm³/kg gas yield at 54.6% H₂+24.2% CO. The studied Fe₂O₃ oxygen carrier/rice straw is a feasible platform for syngas production from an agricultural waste.     

压缩比、CO2对二甲醚均质压燃影响的数值模拟

利用化学反应动力学软件建立二甲醚均质压燃燃烧模型,研究了压缩比和进气掺入CO2对二甲醚均质燃烧的影响。结果表明：增大压缩比加快了二甲醚基元反应速率,使着火提前,燃烧压力、温度上升;进气中加入CO2可以延迟着火时刻,降低缸内压力和温度;CO2对二甲醚均质压燃高温燃烧阶段影响更大。