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。     

Ignition of a nonresonant microwave discharge

The ignition of a 2.45 GHz microwave plasma source by a temporary local magnetic field quenching to ECR value has been studied. The source operates at high magnetic fields (ω_ce > ω) and at overcritical electron densities (ω_pe > ω). This ignition method appears to be attractive also for microwave plasma sources in toroidal devices.     

Ignition and combustion of isopropyl nitrate

The ignition delay times for mixtures of isopropyl nitrate (IPN) with air and argon are measured in a rapid-injection reactor at a pressure of 1 atm and in a shock tube at 2–3 atm. It is shown that the ignition delay time τ of mixtures in which heat is largely released due to oxidation by the oxygen contained in the IPN molecule is determined by the unimolecular decomposition of IPN over the entire temperature range covered (500–730 K). For mixtures in which heat is mainly produced by oxidation reactions involving air oxygen, the ignition delay time at high temperatures is controlled by secondary reactions of oxidation of the hydrocarbon moiety of the IPN molecule, leading to an increase in τ by more than an order of magnitude. Liquid IPN burns in a nitrogen atmosphere only at pressures above 40 atm, at a linear rate of ~4 mm/s. The measured flame temperatures are in close agreement with the respective values calculated using a thermodynamic code.     

Ignition Processes in ac Plasma Displays

The ignition behaviour of discharge cells in ac plasma displays, their ignition statistics and interaction processes occurring between several ignited cells are described and interpreted with a view to basic problems of gas discharge and solid state physics. Ac plasma displays of three different sizes were investigated: PAF 58, 90 and PAF 128.     

国家点火装置(NIF)点火靶制备技术研究进展

文章介绍了国家点火装置(NIF)点火靶制备技术在近年来取得的一些最新进展,主要内容包括芯轴与靶丸的制备,氘氚(DT)冰层的均匀化等方面.     

Ignition of single nickel-coated aluminum particles

A thin coating of nickel on the surface of aluminum particles can prevent their agglomeration and at the same time facilitate their ignition, thus increasing the efficiency of aluminized propellants. In this work, ignition of single nickel-coated aluminum particles is investigated using an electrodynamic levitation setup (heating by laser) and a tube reactor (heating by high-temperature gas). The levitation experiments are used for measurements of the ignition delay time at different Ni contents in the particles. The high-temperature gas experiments are used to measure the critical ignition temperature. It is reported that the Ni coating dramatically decreases both the ignition delay time of laser-heated Al particles and the critical ignition temperature of gas-heated Al particles. A heat balance analysis of the levitated particles shows that the lower ignition temperature of Ni-coated Al particles is the most probable reason for the observed reduction in the ignition delay time. Exothermic intermetallic reactions between liquid Al and solid Ni are considered as the main reason for the lowered ignition temperature of Ni-coated Al particles.     

Ignition of cyclopropane in shock waves

The values of the ignition delay time of cyclopropane–oxygen–argon (cyclo-C₃H₆–O₂–Ar) mixtures of different compositions (φ = 0.333, 1, and 3) behind reflected shock waves at temperatures of 1200–1640 K and a pressure of (0.55 ± 0.05) MPa are measured. A kinetic mechanism of cyclopropane ignition using the known rate constants for the most important elementary reactions is developed. The mechanism closely describes both our own and published experimental data on the delay time of ignition of cyclopropane in shock waves over wide ranges of temperature (1200–2100 K), pressure (0.1–0.55 MPa), cyclopropane concentrations (0.05–11 vol %), and oxygen concentrations (0.25–21 vol %). It is shown that, with increasing fraction of diluent gas in the mixture, the dependence of the ignition delay time on the fuel-to-oxidizer equivalence ratio changes.     

Ignition of stoichiometric hydrogen-oxygen by water hammer

The potential of water hammer events for igniting hydrogen-oxygen mixtures was examined in an experimental study. Compression waves simulating water-hammer events were created by projectile impact on a piston in a water-filled pipe terminated by a test section filled with gas. Triangular wave forms with peak pressures up to 50 MPa propagated through the piping system and compressed the gas in the test section. Experiments were carried out with both air and hydrogen-oxygen gas mixtures using high-speed video of the transparent test section, dynamic pressure and spectroscopic measurements to examine the motion of the water-gas interface and determine ignition thresholds. The impulsive acceleration of the water-gas interface and deceleration created by the compression of the gas resulted in Richtmyer-Meshkov and Rayleigh-Taylor instabilities that grew to create large distortions of the initially planar and horizontal water-gas interface. The gas layer was compressed in volume by up to a factor of 50 and the gas pressures increased to as high as 20 MPa within 2 to 4 ms. The distortion of the water surface during compression resulted in a significant increase in interfacial area and ultimately, creation of a two-phase mixture of water and compressed gas. Some ignition events were observed, but the dispersion and mixing of water with the gas almost completely suppressed the pressure rise during the ignition transient. Only by eliminating the instability of the water interface with a solid disk between the water and gas were we able to observe consistent ignition with significant pressure rises associated with the combustion.     

Ignition of hydrogen in unsteady nonpremixed flows

The effects of unsteady strain on hydrogen (H₂) ignition in nonpremixed flows are investigated with both experimental measurements and numerical computations. A mixing layer is established in a counterflow configuration with a fuel stream containing N₂–diluted H₂ (X_H2=0.08) flowing against heated air. A reproducible ignition process is initiated by introducing atomic oxygen into the mixing layer with a pulsed ArF excimer laser, which photodissociates heated O₂ from the oxidizer stream. The temporal evolution of OH during ignition is measured by planar laser-induced fluorescence. Following the induction phase, the measured OH mole fraction increases rapidly to a super-equilibrium value that is 60% greater than the OH mole fraction in a steady diffusion flame. The peak OH mole fraction occurs at approximately 6 ms after the excimer laser pulse. To study the OH time history under transient strain, the fuel stream is pulsed at a fixed time after the initiation of ignition. The response of the ignition kernel is extremely sensitive to the time delay of the flow transient. The unsteady strain can delay the ignition time or extinguish the kernel. Comparisons between computations and experiments are made for the evolution of OH during autoignition both for steady and unsteady strain. For both steady and unsteady strain, the transient one-dimensional counterflow computations show excellent agreement with the experiment in terms of predicting ignition delays and the rate of OH accumulation during the induction period. The computations also capture the super-equilibrium OH during the transition to the formation of a steady flame, although not to the degree observed experimentally. The computations are further used to understand the influence of unsteady strain on the kernel evolution. It is found that the degree of super-equilibrium OH is sensitive to strain transients applied close to the time of thermal runaway.     

Ignition of hydrogen-air mixtures under volumetric expansion

A better understanding of chemical kinetics under volumetric expansion is important for a number of situations relevant to industrial safety including detonation diffraction and direct initiation, reflected shock-ignition at obstacles, ignition behind a decaying shock, among others. The ignition of stoichiometric hydrogen-air mixtures was studied using 0D numerical simulations with time-dependent specific volume variations. The competition between chemical energy release and expansion-induced cooling was characterized for different cooling rates and mathematical forms describing the shock decay rate. The critical conditions for reaction quenching were systematically determined, and the thermo-chemistry dynamics were analyzed near the critical conditions.     

点火黑腔二维模拟设计

基于二维激光靶耦合流体力学程序,研究设计惯性约束聚变间接驱动点火黑腔的方法.提出先调控X射线驱动温度再调控辐照均匀性的设计顺序.给出总激光功率(特别是主脉冲激光功率)的设计方法.模拟表明,填充气体密度的上限受到槽脉冲P²辐照不均匀性的限制.另外,增加腔长可以抑制靶丸烧蚀层物质的膨胀.最后给出点火黑腔二维设计结果.     

Ignition of acetylene-oxygen mixtures behind shock waves

The delay time of ignition of C₂H₂-O₂-Ar mixtures of various compositions behind reflected shock waves were measured at 980–1300 K and 0.65 ± 0.05 MPa. A kinetic scheme of the ignition of acetylene based on the available rate constants of the key elementary reactions was developed. The scheme satisfactorily describes the experimental data from various works over wide temperature, pressure, and concentration ranges: 980–2400 K, 0.01–1.0 MPa, and 0.5–20.3 vol % acetylene and 1.25–20.4 vol% O₂.     

IRIS-ICP光谱仪点火故障分析

从ICP光谱仪点火系统的组成部分、工作原理、参数分析入手,分析不能正常点火故障及排除方法.     

瞬时纳秒脉冲等离子体点火模式

应用高压纳秒脉冲放电技术分别产生了瞬时冷等离子体和瞬时热等离子体。在圆柱型燃烧室内进行了乙烯/空气预混气的瞬时冷等离子体和瞬时热等离子体点火实验。实验结果表明,瞬时冷等离子体放电所需的电能小于瞬时热等离子体放电。与瞬时热等离子体点火技术相比,瞬时冷等离子体点火缩短了碳氢燃料的点火延迟时间。     

Ignition source static electricity: Incident investigation

Static electricity still represents a frequent ignition source when flammable liquids or combustible powders are handled and processed in industry. The present report deals with the investigation of an incident which occurred during splash filling 200 liter metal drums with isopropyl acetate. Although from the point of view of static electricity isopropyl acetate belongs to the group of liquids with high conductivity, the experimentally in situ determined charge to mass ratios and charging currents are extremely high compared to low conductivity liquids such as hydrocarbon fuels. The ignition of the isopropyl acetate vapors can also be explained if the metal drum was properly earthed. Since the drum had a highly insulating coating with a breakdown voltage of 1.1–1.9 kV the explosive atmosphere could also have been ignited by a discharge from the highly charge isolated liquid.     

Ignition of non-premixed cyclohexane and mono-alkylated cyclohexane flames

Ignition temperatures of non-premixed cyclohexane, methylcyclohexane, ethylcyclohexane, n-propylcyclohexane, and n-butylcyclohexane flames were measured in the counterflow configuration at atmospheric pressure, a free-stream fuel/N₂ mixture temperature of 373 K, a local strain rate of 120 s^?1, and fuel mole fractions ranging from 1% to 10%. Using the recently developed JetSurf 2.0 kinetic model, satisfactory predictions were found for cyclohexane, methyl-, ethyl-, and n-propyl-cyclohexane flames, but the n-butylcyclohexane data were overpredicted by 20 K. The results showed that cyclohexane flames exhibit the highest ignition propensity among all mono-alkylated cyclohexanes and n-hexane due to its higher reactivity and larger diffusivity. The size of mono-alkyl group chain was determined to have no measurable effect on ignition, which is a result of competition between fuel reactivity and diffusivity. Detailed sensitivity analyses showed that flame ignition is sensitive primarily to fuel diffusion and also to H₂/CO and C₁–C₃ hydrocarbon kinetics.     

Theoretical Calculation on the Piloted Ignition of PMMA

This study presents the comparison of the experimental results and theoretical predictions of the piloted ignition of black PMMA. The model for theoretical calculations included heat, momentum, mass transfer equations and reaction kinetics both in the gas phase and the solid phase, to comprehensively describe the piloted ignition. The experimental samples were thick black PMMA pieces, with the ignition time and the critical surface temperatures at ignition measured using a cone heater under different external radiation heat fluxes. The predictions from the calculations showed good agreement with the experiment at high heat flux, but the deviation was distinct at low heat fluxes, especially for the critical surface temperatures. The fail of the prediction at low heat fluxes was regarded, by analysis, as the result of the neglecting of the decomposition energy term of PMMA in the energy balance equation.     

Statistics of Ignition Processes in ac Plasma Displays

The statistics of the ignition behaviour of discharge cells in ac plasma displays and interaction processes occurring between several ignited cells are described and interpreted with a view to basic problems of gas discharge and solid state physics. For the statistical evaluation of ignition lag values recorded by means of a computer controlled equipment the Laue distribution is used.     

Ignition regime for fusion in a degenerate plasma

We identify relevant parameter regimes in which aneutronic fuels can undergo fusion ignition in hot-ion degenerate plasma. Because of relativistic effects and partial degeneracy, the self-sustained burning regime is considerably larger than previously calculated. Inverse bremsstrahlung plays a major role in containing the reactor energy. We solve the radiation transfer equation and obtain the contribution to the heat conductivity from inverse bremsstrahlung.     

基于openECU的点火正时控制策略设计

点火系统是发动机的重要主成部分,对发动机的性能有绝对性的影响。在开放式ECU的基础上进行了点火正时策略的设计以及预标定的工作,大大缩短了开发的难度和周期;对某LNG气体机的点火正时策略进行了设计和优化,并结合发动机计算模型（进气,压缩,做功,排气）进行了反馈和验证。使用开放式ECU进行实验开发,可以为实验节省大量的时间和资源,监测不同的输入条件对点火提前角的影响,实现了脉谱的预标定,大大缩短了开发工作,具有一定的实际运用价值。