苯快速反应点火特性的光谱研究

利用由单色谱仪、压力传感器以及示波器组成的测试系统, 测定了高温激波管中苯快速反应的几个重要产物：H,C₂和CH的点火延迟时间和出现的顺序。提出了一种在入射激波条件下确定含能材料冲击点火延迟时间的新方法,并介绍了苯在快速反应中碳生成的微观反应机理。 研究表明: 无论马赫数如何改变,H原子总是最先出现,说明苯在快速反应过程中,首先断裂的C—H键,而不是C—C键。利用较早出现的反应中间产物H原子来测定苯的点火延迟时间更为准确。利用单色谱仪技术能较好地研究苯的快速反应点火特性,新方法与国内外常用的全色光技术相比可明显减少实验量。     

用多种谱仪技术研究环氧丙烷点火的微观特性

利用OMA(光多通道分析系统)谱仪和单色谱仪技术研究了环氧丙烷冲击点火的微观特性.OMA谱仪观察到O,CH2O,C2,CH,CH3O,CO2,H2O等许多中间产物和最终产物.利用三台单色谱仪和压力传感器确定环氧丙烷冲击点火后这些产物出现的顺序并确定了它们的点火延迟时间和临界条件.     

环氧丙烷点火的光谱研究

 利用多种光谱技术，提出了一种确定燃料冲击点火延迟时间的新方法。用这种方法所获得的实验值比国内外常用光电二极管（峰值波长约在800 nm）方法的所测值更接近实际值。环氧丙烷受冲击后，反应中间产物出现的时间是不同的，辐射强度也不同。在冲击波作用下，基团出现的顺序便可确定，它们依次为O、CH₂O、C₂、CH、CH₃O、CO₂、H₂O等，而O原子总是首先出现。     

铝粉点火微观机理的光谱研究

 铝粉是一种含能高的材料,它被广泛地添加到含能材料中。利用3台单色谱仪和OMA谱仪等多种谱仪技术,研究了铝粉在几种不同环境下的快速反应微观特性。研究表明：铝粉冲击波点火的临界条件和铝粉的物理状态相关。微米铝粉点火的临界温度为2 100 K,它接近Al₂O₃的熔化温度。它表明,在空气中容易氧化的微米铝粉点火,必须使铝粉表面的氧化层熔化。在气相反应中,微米铝粉和氧的反应是主要的;和水的反应是次要的。减小微米铝粉的颗粒尺寸,可以明显提高快速反应温度。 含铝复合燃料中的液体燃料反应后的铝粉才能参与反应;铝粉添加至气相反应介质后将明显提高反应温度。     

纳米铝粉点火机理的快速光谱研究

用光触发同步采集技术在多光谱系统上测定纳米铝粉与环氧丙烷快速反应的点火延迟时间和基团光谱强度,得出诱导激波作用下纳米铝粉的点火机理。X射线衍射(XRD)数据表明,等离子体方法生产的纳米铝粉由于活性较高表面有部分氧化,电子能谱(XPS)给出结果表明氧化层厚度～3nm,且其反应生成物的电子能谱显示氧化层厚度随诱导激波强度增加而相应增大。单色仪测定AlO(464.8nm)点火时间表明随诱导激波强度增大,纳米铝粉在环氧丙烷反应系统中的抛撒状态分布更均匀,颗粒受热面增大,受热率明显增大,且激波作用下铝粉表面3nm厚氧化层也极易被熔破,使内核活性铝气化与反应系统中的氧原子及含氧分子反应放热而达到点火状态。     

太赫兹光谱技术在四氢双环戊二烯检测中的应用

研究了太赫兹光谱技术在鉴别含能材料同分异构体中的应用。首先研制了适于特定工程应用的太赫兹时域光谱仪样机,并经过振动冲击、高低温试验验证了样机的环境适应性,表明该款样机完全可以在非实验室环境下稳定可靠地工作。利用一氧化碳标准气体验证了样机测量光谱的正确性,并同时实现了对样机测量频率的校准;利用校准后的光谱仪测量了四氢双环戊二烯的两种同分异构体endo-THDCPD和exo-THDCPD的太赫兹光谱,测量结果显示两种不同构型材料的太赫兹光谱存在显著差异,endo-THDCPD的太赫兹光谱在0.23 THz和1.70 THz处呈现出明显的特征吸收,exo-THDCPD的2个最明显的特征吸收峰则位于1.41 THz和1.74 THz。该结果表明:运用太赫兹光谱技术可有效区分这两种分子结构仅存在微弱差异的材料,对太赫兹光谱在含能材料研究领域的应用具有参考意义。     

RDX激光点火的一维气相模型

为了研究含能材料RDX在激光作用下的点火特性,在Liau等人的工作基础上,考虑了物理参数随温度和组分浓度的变化,建立了RDX激光点火的气相模型.利用有限差分方法,计算了激光功率密度为400 W/cm2、环境压力为0.1 MPa时RDX的点火过程.结果表明:约90%的RDX以蒸发的形式进入气相,另外的10%在液相中发生分...     

甲基环己烷燃烧反应特性的光谱研究

利用激波管实验装置由反射激波点火,在点火温度1 164～1 566 K,点火压力1.03～1.99 atm,燃料浓度为1.0%,当量比为1.0的条件下,用光谱单色仪、光电倍增管、压力传感器和示波器等组成测试系统,测量了甲基环己烷燃烧过程中主要中间产物OH,CH和C2自由基特征光辐射随时间的连续变化,并测得了甲基环己烷/氧气/氩气的点火延迟时间。通过对测量结果的分析,初步认识了甲基环己烷燃烧反应中几个主要中间产物的光辐射特性及其反映出的甲基环己烷燃烧反应特性。实验所测点火延迟时间与已报道的实验结果和燃烧反应机理预测结果符合较好。本文实验结果为构建和验证甲基环己烷燃烧反应机理提供了实验依据。     

炸药粉点火与快速反应临界条件的确定

 在爆炸激波管中利用我们研制的测温技术、回收技术及光谱技术研究了三氨基三硝基苯（TATB）、黑索金（RDX）、梯恩梯（TNT）粉在不同激励条件下的反应程度。研究表明：TATB炸药的临界点火温度和压力最高,其次是TNT,RDX最小。测量结果与国外的结果进行了比较。     

等离子体中活性粒子分析及化学动力学机理

利用发射光谱测量技术分析了介质阻挡放电等离子体激励空气产生的主要活性粒子,利用零维等离子体动力学模型模拟了甲烷/空气中放电阶段主要活性粒子的演化规律,并通过敏感性与化学路径分析研究了O原子影响甲烷点火过程的化学动力学机理。研究表明：空气中介质阻挡放电等离子体主要产生N2和O2的激发态粒子,激发态粒子的数密度随着电压的增加而增大;激发态粒子经过一系列物理化学反应最终转化成若干自由基,其中O原子的摩尔分数最大;O原子缩短甲烷点火延迟时间一个量级,原因在于添加O原子后甲基（CH3）的氧化途径由自点火过程中的经O2直接氧化为CH3O和CH2O转变为经HO2和O原子氧化为CH3O和CH2O,由于后者的基元反应速率快,因而明显缩短了点火延迟时间。     

利用OH自由基特征发射谱测量正庚烷的点火延迟时间

在化学激波管中利用反射激波进行点火,采用OH自由基在306.4nm处特征发射谱线强度的急剧变化标志燃料的着火,由光谱单色仪、光电倍增管、压力传感器和示波器组成测量系统,测量了正庚烷/氧气的点火延迟时间,点火压力(1.0±0.1)和(0.75±0.05)atm,点火温度1 170～1 730K,当量比1.0,得到了在此实验条件下正庚烷/氧气点火延迟时间随温度变化的关系式。研究结果表明正庚烷/氧气点火延迟时间随温度的增加呈指数减小,点火压力为0.75atm时,随着点火温度的增加,点火延迟时间的变化率要小于1.0atm条件时。实验结果为建立正庚烷燃烧反应动力学模型,验证正庚烷燃烧反应机理提供了实验依据。     

High-speed imaging of the ignition of ethanol at engine relevant conditions in a rapid compression machine

The rapid compression machine (RCM) is a great tool for investigating fuel properties under engine relevant conditions (high-pressures, low temperatures). The most common diagnostics is measuring the pressure over time and determining the ignition delay time (IDT). In this study, for the first time, the OH* luminescence of ethanol/air mixture is measured within an RCM experiment at 15 and 20?bar for Φ?=?0.5. Combining the common pressure measurements with the simultaneously recorded high-speed images (up to 74.5?kHz framerate) gives a first insight into understanding the ignition modes and the corresponding pressure traces. At 74.5?kHz, in contrast to findings in literature, the ethanol ignition did not show to be purely homogeneous. Four different propagating fronts of OH* luminescence have been recorded. Besides a flame kernel and a detonation-like ignition front two further fronts prior to main ignition have been observed. The propagating speeds of the fronts have been determined and depend on the overall IDT.     

Numerical simulations of the ignition of n-heptane droplets in the transition diameter range from heterogeneous to homogeneous ignition

Spontaneous ignition of single n-heptane droplets in a constant volume filled with air is numerically simulated with the spherical symmetry. The volume is closed against mass, species, and energy transfer. The numerical model is fully transient. It continues calculation even after the droplet has completely vaporized, and therefore can predict pre-vaporized ignition. Initial pressure and initial air temperature are fixed at 3 MPa and 773 K, respectively. The droplet is initially at room temperature, and its diameter is between 1 and 100 μm. When the overall equivalence ratio is fixed to be sufficiently large, there exists no ignition limit in terms of initial droplet diameter d₀, and the ignition delay takes a minimum value at certain d₀. In such a case, transition from the heterogeneous ignition to the homogeneous ignition with decreasing d₀ is observed. When d₀ is fixed to be so small that the ignition would not occur in an infinite volume of air, the ignition delay takes a minimum value at certain , which is less than unity. Two-stage ignition behavior is investigated with this model. Ignition delay of a cool flame has the dependence on d₀ that is similar to that of ignition delay of a hot flame when is unity. When is almost zero, the ignition limit for cool flame in terms of d₀ is not identified unlike that for hot flame.     

Effects of blending 2,5-dimethylfuran on the laminar burning velocity and ignition delay time of isooctane/air mixture

The prospects of 2,5-dimethylfuran (DMF) as a bio-derived fuel that can be blended with gasoline are believed to be impressive. However, the effects of blending DMF on the key combustion parameters like the laminar burning velocity and ignition delay time of gasoline/air mixture need to be studied extensively for the successful implementation of the fuel mixture in spark ignition engines. Therefore, a skeletal chemical kinetic mechanism, comprising of 999 reactions among 218 species, has been developed in the present work for this purpose. The proposed chemical kinetic model has been validated against a wide range of experimental data for the laminar burning velocity and ignition delay time of isooctane (representing gasoline), DMF and their blends. It has been found from the present study that the thermal diffusivity of the unburnt gas mixture changes by a very small amount from the corresponding value for the pure isooctane/air mixture when DMF is added. Unlike isooctane, the DMF molecule does not consume H radicals during its primary breakup. Therefore, the maximum laminar burning velocity increases marginally when 50% DMF is blended with isooctane due to the increased presence of H radicals in the flame. The negative temperature coefficient behaviour in the ignition delay time of the isooctane fuel vanishes when 30% DMF (v/v) is blended to it.     

The impact of residence time on ignitability and time to ignition in a toroidal jet-stirred reactor

Understanding of ignition processes is central to design for reliable and safe aerospace combustor systems. Ignition is influenced by many factors including combustor geometry, flow conditions, fuel composition, turbulence intensity, ignition source, and energy deposition method. A toroidal jet-stirred reactor (TJSR) utilizes bulk fluid motion, presence of recirculation zones, a bulk residence time, and turbulence intensities which emulate characteristics relevant to cavity stabilized and swirl stabilized combustors. In this work, a TJSR was used to quantify ignitability and time-to-ignition of premixed ethylene and air. The effects of inlet temperature, residence time, and reactivity were studied on forced ignition processes. Experimental conditions ranged from residence times of 15–35?ms, mixture temperatures of 340–450?K, and equivalence ratios of 0.5–1 using capacitive spark-discharge ignition. The minimum equivalence ratio for ignition (MER), or the equivalence ratio at 50% probability, shows an inverse relationship with mixture temperature and residence time. Prior theory of real engine combustor performance for lean light off, proposed by Ballal and Lefebvre, was compared to the MER and displayed similar trends to the model. Spatially integrated OH* chemiluminescence was used to measure time to ignition within the reactor. Reduction in ignitibility was experienced as the time-to-ignition approached the residence time stressing the importance of device flow time scales in relation to kernel growth dynamics and ignition probability.     

镁颗粒群非稳态着火过程数值模拟

建立了镁颗粒群着火的一维非稳态有限影响体模型, 数值模拟颗粒群中镁颗粒的着火过程. 研究表明, 当镁颗粒表面反应加剧之后,颗粒相温度急剧上升, 迅速达到着火, 而其周围气相的温升速率却远小于颗粒的温升速率; 在着火过程中气相温度只在颗粒表面附近升高比较明显, 整体温度升高不大. 分析了颗粒群内部参数和环境参数对镁颗粒群着火的影响. 随颗粒浓度的增加, 颗 粒群变得易于着火, 其着火时间变短, 但颗粒浓度增大到一定程度后, 继续增大该值将对颗粒群的着火起消极作用. 环境压力对颗粒群着火的影响比较小,在1-5 atm范围内颗粒群的着火性能基本不变. 气相中氧气浓度对颗粒群的着火性能影响也不显著, 但当氧气浓度过小时, 对着火过程的影响将大大增强.颗粒粒径、气相/颗粒相初温、辐射源温度对颗粒 群着火的影响巨大,小粒径、高温度促使颗粒群快速着火.数值模拟与文献中试验 结果的变化趋势相一致.