Study of low-pressure premixed laminar n-heptane+propane/oxygen/nitrogen flames

Low-pressure premixed laminar n-heptane+propane/oxygen/nitrogen flames were investigated with tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam sampling mass spectrometry. Three flames with different mass percentage of propane in the fuel blends of 0%, 10%, and 20% were studied. The combustion intermediates were identified by comparing the measured IEs with those values in literatures. Mole fraction profiles of the main species were compared among the three flames. The experimental results provide detailed data in understanding the combustion of n-heptane and n-heptane/propane blends in engine. They are also helpful in establishing and verifying the kinetic models. Supported by the National Natural Science Foundation of China (Grant Nos. 50636040 and 50521604)     

An experimental study of premixed laminar methane/oxygen/argon flames doped with hydrogen at low pressure with synchrotron photoionization

Laminar premixed stoichiometric methane/hydrogen/oxygen/argon flames were investigated with tunable synchrotron vacuum ultraviolet （VUV） photoionizaUon and molecular-beam sampling mass spectrometry techniques. The methane/hydrogen fuel blends with hydrogen volumetric fraction of 0, 20%, 40%, 60% and 80% were studied. All observed flame species, including stable intermediates and radicals in the flames, were detected by measuring photoionization mass spectra and photoionization efficiency （PIE） spectra. Mole fraction profiles of major species and intermediates were derived by scanning burner at some selected photon energies near ionization thresholds. The influence of hydrogen addition on mole fraction of major species and intermediates was analyzed. The results show that the major species mole fraction of CO, CO2 and CH4 decreases with the increase of hydrogen fraction. The mole fraction of intermediates measured in this experiment decreases remarkably with the increase of hydrogen fraction. This would be due to the increase of H and OH radicals by hydrogen addition and the high diffusivity and activity of H radical promoting the chemical reaction. In addition, the increase of H/C ratio with the increase of hydrogen fraction also leads to the decrease of the mole fraction of carbon-related intermediates and contributes to the decrease of unburned and incomplete combustion products.     

CO2/N2稀释对H2/CH4层流火焰传播特性的影响

利用本生灯-纹影系统实验研究含有CO₂，N₂的掺氢天然气层流预混火焰传播速度，并应用GRI-3.0机理模拟计算不同组分预混燃气绝热火焰温度、敏感性系数及重要自由基浓度等，详细讨论CO₂，N₂的稀释效应.研究表明，GRI-3.0机理能较好地预测掺氢天然气层流预混火焰传播速度；CO₂，N₂稀释组分会显著抑制掺氢天然气层流预混火焰速度及其绝热火焰温度；与N₂相比，CO₂不仅具有较强的热力学效应，且随着CO₂稀释比的增加，火焰中重要自由基H浓度显著减少，抑制氧化反应H+O₂O+OH对燃烧的主导促进效应，使预混燃料的层流火焰传播速度显著降低.     

吸收LNG冷能的丙烷冷凝器低温传热性能

利用丙烷作为中间介质回收LNG冷量是解决LNG冷能利用过程中大温差传热问题的有效途径。对超临界LNG丙烷在冷凝器中的传热进行理论研究。根据丙烷所处的状态将LNG与丙烷的传热分为过热区、两相流区及过冷区。通过参数分析研究丙烷入口温度、冷凝器尺寸、丙烷流量等对冷凝器整体传热结果的影响规律。结果表明:适量增大LNG流量、减小丙烷通道的尺寸有利于LNG冷量的回收,而过热丙烷的入口温度对LNG冷量的回收影响不大;提高冷凝器传热效能的途径包括:找出最佳丙烷入口温度、适当减小丙烷流量以及减小丙烷通道尺寸。     

吡咯和吡啶火焰中含氮燃烧中间体的探测

利用同步辐射(SR)和分子束质谱(MBMS)研究了两种含氮燃料(吡咯和吡啶)分别在贫燃和富燃条件下的4个低压预混火焰.通过测量光电离质谱和扫描光电离效率谱(PIE),鉴别了火焰中的燃烧中间体的化学结构.结果表明在富燃火焰中容易产生乙炔(C2H2),而在贫燃火焰中则更容易形成一氧化氮(NO)/甲醛(HCHO).在4个火焰中同时观察到了HCN、C2H4、C3H4、C2H2O、HNCO、C3HN、C3H3N、C3H5N、C4H3N和C6H6等稳定中间体以及CH3、C3H3和C2H2N等自由基.     

Fullerenes C60 and C70 in flames

The fullerenes C60 and C70 were first identified in carbon vapour produced by laser irradiation of graphite, and have recently been produced in macroscopic quantities by vaporization of graphite with resistive heating. It has also been suggested that fullerenes might be formed in sooting flames, and indeed all-carbon ions with mass/charge ratios suggestive of fullerenes have been detected in flames. These species were assumed to have the cage structures of fullerenes, but the mass spectroscopic evidence could not establish this conclusively. We have now collected samples of condensible compounds and soot from hydrocarbon combustion under a range of conditions, and analysed these using conventional techniques in an effort to detect fullerenes. Spectroscopic studies reveal the presence of C60 and C70 in yields and ratios that depend on temperature, pressure, carbon/oxygen ratio and residence time in the flame. Control of these conditions allows optimal yields of 3 g of fullerenes per kilogram of fuel carbon burned, and variation of the C70/C60 ratio over the range 0.26-5.7.     

在Cr／ZrO_2复合氧化物催化剂上丙烷脱氢反应性能的研究

研究了在氧化条件下，以Ｃｒ／ＺｒＯ_２为催化剂，丙烷氧化脱氢制丙烯的反应。主要讨论了Ｃｒ含量、不同载体及活性金属离子Ｋ￣＋对催化剂性能的影响，诸如对催化剂活性、催化剂寿命、丙烷转化率及丙烯选择性等方面的影响。     

MoVTeO/SiO2催化剂上丙烷选择氧化制丙烯醛

用浸渍法制备了一系列不同组成的MoVTeO/SiO2催化剂,并用XRD、TPR和催化剂性能评价等方法考察了催化剂的物相结构、氧化还原性质及其对丙烷选择氧化制丙烯醛反应的催化性能.结果表明,由于组份之间的相互作用,MoO3的分散度提高,还原温度降低,且其某些晶面可能部分重构或被其它组份覆盖,因而有利于催化活性的提高和丙烯醛的生成.在考察的不同催化剂组成中,(Mo V Te)/Si原子比为6%的MoV0.2Te0.1/SiO2催化剂具有最佳的反应性能.反应条件对催化剂性能的影响说明,在丙烷选择氧化制丙烯醛反应中,丙烯为反应的中间物种.     

高温下掺氢天然气层流预混火焰传播特性

利用本生灯-纹影系统及CHEMKIN-PRO对高温下掺氢天然气层流预混火焰传播速度进行实验及数值模拟研究,并从热力学及化学动力学效应方面讨论了初始温度对掺氢天然气层流预混火焰传播特性的影响.结果表明:GRI-3.0机理能较准确地预测293~500K条件下的掺氢天然气层流预混火焰传播速度;在相同初始温度下,混合物层流预混火焰传播速度在高掺氢比时增幅更显著;在相同当量比下,混合物层流预混火焰传播速度及绝热火焰温度随初始温度的升高呈近线性增加;高温下,H自由基浓度的增大进一步增强了H+O₂=O+OH对整体燃烧反应的促进作用,使混合物层流预混火焰传播速度显著加快.     

低热值气体燃料掺氢火焰稳定性的研究

基于直接数值模拟方法和详细化学反应机理研究了流体动力学不稳定性和热-质扩散不稳定性共同作用下的低热值气体燃料掺氢胞状火焰的发展和演变过程.建立了多组分气体燃料燃烧控制方程,获得了不稳定性作用下的低热值气体燃料掺氢胞状火焰的多种演变形式:胞的分裂、局部熄灭、二次熄灭和再燃.研究结果表明随着燃料中H2的增加,胞状火焰出现的时间提前,火焰胞的幅值增加.随着燃料中CO2的增加,火焰的不稳定性受到抑制.低热值气体燃料掺氢火焰在不稳定时会出现火焰胞的分裂、局部熄灭和再燃等3种动力学形态.胞的二次熄灭只发生在热-质扩散不稳定性较强的稀燃H2/空气火焰中.     

流程参数对丙烷预冷混合制冷剂循环损失的影响

在丙烷预冷的混合制冷剂循环液化流程热力分析的基础上,对流程进行分析,并分析了流程中天然气压力、丙烷预冷后天然气的温度、制冷剂进入压缩机时的温度和压力及制冷剂压缩机排气压力对流程各设备损失的影响.分析表明,压缩机的损失占整个流程损失的一半.提高天然气的压力、混合制冷剂压缩机进气温度、混合制冷剂压缩机进排气压力,降低预冷后天然气温度,均可降低整个流程的损失.     

Microstructure of premixed propane/air flame in the transition from laminar to turbulent combustion

In order to explore the flame structure and propagation behavior of premixed propane/air in the transi-tion from laminar to turbulent combustion, the high speed camera and Schlieren images methods were used to record the photograph of flame propagation process in a semi-vented pipe. Meanwhile, the super-thin thermocouple and ionization current probe methods were applied to detect the temperature distribution and reaction intensity of combustion reaction. The characteristics of propane/air flame propagation and microstructure were analyzed in detail by the experimental results coupled with chemical reaction thermodynamics. In the test, the particular tulip flame behavior and the formation process in the laminar-turbulent transition were disclosed clearly. From the Schlieren images and iron current results, one conclusion can be drawn that the small-scale turbulent combustion also appeared in laminar flame, which made little influence on the flame shape, but increased the flame thickness obviously.     

Preparation of Chitosan-g-PAMPS in H2O/scCO2 Inverse Emulsion

Chitosan(CS)was successfully modified in supercritical carbon dioxide(scCO2)by grafting method to enhance its water solubility.In this work,a three-arm star-like fluorinated polymer was synthesized by atom transfer radical polymerization(ATRP)method and applied as a surfactant in supercritical carbon dioxide(scCO2).Then 2-acrylamido-2-methyl propane sulfonic acid(AMPS)was grafted onto CS(CS-g-PAMPS)in H2O/scCO2inverse emulsion.The effects of mass ratio of water and surfactants(R w/s)and pressure of scCO2on the grafting reaction were investigated.The grafting rate,particle size,and dispersity in water of CS-g-PAMPS varied greatly as R w/s and pressure of scCO2changed.It could be found that the value of R w/s at 12 and the pressure of scCO2at 30 MPa were the optimum conditions for the grafting reaction.CS-g-PAMPS prepared in this reaction system has higher grafting rate,smaller particle sizes,and better dispersity in water than those prepared via conventional methods.     

磺酸盐双子表面活性剂的合成及性能

以2-氯乙基磺酸钠、1, 3-丙二胺、环氧氯丙烷等为原料,经取代、开环反应合成了一种磺酸盐型阴离子双子表面活性剂:N, N-二(3-氯-2-羟基丙烷-N-十六烷基仲胺)丙二胺二乙基磺酸钠(GAS-316). 通过控制变量,优化了GAS-316的合成条件;利用傅里叶变换红外光谱(FT-IR)和核磁共振氢谱(1H NMR)对GAS-316进行结构表征,并评价其表面/界面性能. 结果表明:GAS-316的临界胶束浓度(C_CMC)为0.27 mmol/L,其表面张力γ_CMC为19.64 mN/m,具备优秀的表面活性;质量分数为0.5%的GAS-316溶液在45 ℃时,20 min内可将油水界面张力降至5.25×10-2 mN/m(低界面张力级别),拥有较好的界面活性.     

非均匀受热液化石油气储罐压力响应及阀门动作模拟

建立了火灾环境下液化石油气储罐内压力响应及阀门动作过程的数学模型,模拟了装载丙烷的水平圆柱形储罐在装料比为41%时非均匀受热环境下储罐内的压力变化及阀门动作过程,预测了装料比为41%时储罐装料质量、阀门泄放率及壁面温度的变化规律.将计算结果和实验结果进行了对比,吻合良好.结果表明,阀门打开期间,压力的上升及储罐壁经受高温是导致储罐爆炸的主要因素.     

Ni—Cu—ZnO催化剂组分间相互作用的研究

研究了Ｎｉ－Ｃｕ／ＺｎＯ催化丙烷氢解反应并用化学吸附和磁化率测量等技术表征了催化剂。随着催化剂中Ｃｕ含量的增加,Ｈ２化学吸附量与磁化率均显著下降,与以前的研究结果相结合,说明Ｎｉ与Ｃｕ相互作用形成了原子簇而且Ｃｕ富集在表面。同时,Ｎｕ－Ｃｕ间也存在电子效应,即Ｃｕ的ｄ电子向Ｎｉ的ｄ轨道进行了转移。丙烷氢解反应进一步表明,Ｎｉ－Ｃｕ／ＺｕＯ中也存在金属－载体相互作用,Ｎｉ－Ｃｕ金属间相互作用以及Ｎｉ     

Shock tube study on auto-ignition characteristics of kerosene/air mixtures

Ignition delay times are obtained for kerosene/air mixtures behind the reflected shock waves at temperatures between 1445 and 1650 K,at a pressure of 0.11 MPa and an equivalence ratio of 1.0.A nebulization device with Laval nozzle is used to nebulize kerosene and form an aerosol phase,which evaporates and diffuses rapidly behind the incident shock waves.Mixtures auto-ignite behind the reflected shock waves.An ICCD is used to visualize the kerosene/air mixture’s ignition characteristics.The mixture’s ignition intensity increases with increase in initial temperature.Continuous and irregular flames exist below 1515 K while plane and discontinuous flames exist over 1560 K.Ignition delay times decrease with increase in initial temperature.Experimental data shows good agreement with results reported previously in the literature.A new surrogate (consisting of 10% toluene,10% ethylbenzene and 80% n-decane) is proposed for kerosene.Honnet et al.’s mechanism is used to simulate the ignition of kerosene with calculations agreeing well with the experimental data.The sensitivity of reaction H+O2 <=>OH+O,which shows the highest sensitivity to the ignition delay time,increases with an increase in temperature.The chain breaching reaction of CH3 with O2 accelerates the total reaction rate and the H-atom abstraction of n-decane controls the total reaction rate.The rate of production and instantaneous heat production indicate that two reactions,H+O2 <=>OH+O and O+H2 <=>OH+H,are the key reactions to the formation of OH radicals,as well as the main endothermic reaction.However,the reaction of R3 is the main heat release reaction during ignition.Flame structure analysis shows that initial pressure is increased slightly as CO and H2O will appear before main ignition.     

水溶性MA/AA/AMPS聚羧酸高效陶瓷减水剂的制备及其性能

以马来酸酐（MA）、丙烯酸（AA）和2-丙烯酰胺基-2-甲基丙磺酸（AMPS）为单体,采用水溶液聚合法制备了一种MA/AA/AMPS聚羧酸高效陶瓷减水剂.通过单因素实验以考察合成条件对聚合反应的影响,采用FT-IR和POM分别表征其官能团结构及分散情况,并进一步利用SEM图片观察陶瓷坯体料浆形貌.结果表明,水溶性MA/AA/AMPS聚羧酸高效陶瓷减水剂的合成条件对其性能有很大影响.各单体的摩尔数、引发剂的用量、聚合温度等因素都在一定程度上影响陶瓷坯体料浆体系的性能.     

载带姜黄素的卵磷脂/果胶锌凝胶球的性能

采用滴制法制备载带姜黄素的卵磷脂/果胶锌凝胶球,以粒径、粒质量、载药量、包封率以及体外释药性能为评价指标,讨论工艺参数对评价指标的影响.实验制备的载带姜黄素的卵磷脂/果胶锌凝胶球成球均匀,平均粒径1.34~1.59,mm,平均粒质量1.74~3.45,mg.当卵磷脂与果胶的质量比为5∶4、药胶质量比为16∶20、氯化锌质量浓度为70,g/L、果胶质量浓度40,g/L、NaOH质量浓度为30,g/L时,载药量为18.03%,包封率为85.81%,模拟小肠液中8,h累积释药率为1.64%,再进入模拟结肠环境36,h累积释药率为68.72%.结果表明,卵磷脂的加入改善了果胶锌凝胶球对姜黄素的载带效果以及缓释效果.     

Experimental study on inhibition of low pressure premixed flat methane-oxygen flames by trifluoromethane

This paper presents measurements of combustion species of low pressure laminar premixed flat methane-oxygen flames inhibited by triflnoromethane （CF3H） using synchrotron radiation-molecular beam mass spectrometry （SR-MBMS）. Fire suppression chemistry of CF3H is investigated by selective detection of combustion radicals and intermediates. Results show that SR-MBMS offers a powerful tool for studying fire suppression chemistry of halon replacements, which may extensively detect combustion species in the inhibited flames, especially radicals and intermediates. The suppressant CF3H is completely consumed in the preheat zone of premixed flames and produces fluorinated radicals such as CF3 and CF2. CF3 is the main radical participating in flame inhibition cycles in the reactive zone.Unlike HBr, HF produced by CF3H is very stable and will not act as a radical scavenger because the bond energy of H-F is much higher than that of H-Br, which is responsible for less effectiveness than conventional bromine-based suppressants.