在中国科学院力学研究所Φ800 mm高温低密度激波管上进行电磁波在等离子体中传输机理研究时,低密度和强激波条件下,由于气体解离和电离等非平衡过程,使得激波后2区宽度显著减小;同时由于边界层效应造成激波衰减和接触面加速,使得激波后2区长度进一步减小.这两个效应导致激波管2区实验观测时间减小,2区气体处于非平衡状态,增加了观察数据的不稳定性和数据分析的难度.本文提出在Φ800 mm高温低密度激波管中采用氩气(Ar)和空气(Air)混合气替代纯空气作为激波管实验介质气体.利用Ar不解离和难电离的特性,减小激波前后压缩比,从而增加激波后2区实验时间和气体长度.采用Langmuir静电探针和微波透射诊断技术测量激波后电子密度,同时利用探针测量激波后2区实验时间.结果显示,在Ar+Air混合气实验中,激波波后电子密度可达与纯Air同样的1013cm-3量级.在与纯Air相同的电子密度和碰撞频率条件下,采用95％Ar+5％Air和90％Ar+10％Air两种混合气,激波后2区实验时间和气体长度约为纯Air条件下的5～10倍,其中2区实验时间为300～800μs,2区气体长度1～1.5 m.在Φ800 mm激波管中采用Ar+Air介质气体进行电磁波传输实验,获得了比在纯Air介质中与理论预测更一致的结果.

In ground tests of hypersonic scramjet,the high-enthalpy airstream produced by burning hydro?carbon fuels often contains contaminants H2O and CO2. The contaminants may cause the ignition characteristics of fuels to become discrepant between ground tests and real flights. In order to properly assess the influence of the contaminants on ignition characteristics of hydrocarbon fuels,the effects of H2O and CO2 on ignition characteris?tics of RP-3 aviation kerosene were investigated in a preheated shock tube. To meet the needs of scramjet ground tests based on the ignition delay times of RP-3 aviation kerosene in clean gas, comparative experiments were conducted with clean and vitiated gases. At pressure of 0.05,0.1 and 0.2MPa,and equivalence ratios of 0.5 and 1,respectively,ignition delay times of kerosene were measured for four cases:(1) clean gas,(2) gas vitiat?ed with 4%and 25%H2O by mole,(3) gas vitiated with 3%and 10%CO2 by mole,and (4) gas vitiated with 15%H2O and 10%CO2 by mole fraction. The experimental results show that water vapor or/and carbon dioxide have almost no effect at pressure of 0.1 MPa. However,at pressure of 0.05MPa and 0.2MPa,respectively,wa? ter vapor appears to accelerate the ignition process, whereas carbon dioxide produces an inhibiting effect. At pressure of 0.05MPa and 0.2MPa, an obvious promoting effect appears over a wide temperature range when wa?ter vapor and carbon dioxide exist together. The results were also discussed preliminarily by considering both the combustion reaction mechanism and the thermophysic properties of the test mixtures.

In ground tests of hypersonic scramjet, the high-enthalpy airstream produced by burning hydrocarbon fuels often contains contaminants of water vapor and carbon dioxide. The contaminants may change the ignition characteristics of fuels between ground tests and real flights. In order to properly assess the influence of the contaminants on ignition characteristics of hydrocarbon fuels, the effect of water vapor and carbon dioxide on the ignition delay times of China RP-3 kerosene was studied behind reflected shock waves in a preheated shock tube. Experiments were conducted over a wider temperature range of 800–1 500K, at a pressure of 0.3 MPa, equivalence ratios of 0.5 and 1, and oxygen concentration of 20%. Ignition delay times were determined from the onset of the excited radical OH emission together with the pressure profile. Ignition delay times were measured for four cases: (1) clean gas, (2) gas vitiated with 10% and 20% water vapor in mole, (3) gas vitiated with 10% carbon dioxide in mole, and (4) gas vitiated with 10% water vapor and 10% carbon dioxide, 20% water vapor and 10% carbon dioxide in mole. The results show that carbon dioxide produces an inhibiting effect at temperatures below 1 300 K when ϕ = 0.5, whereas water vapor appears to accelerate the ignition process below a critical temperature of about 1 000 K when ϕ = 0.5. When both water vapor and carbon dioxide exist together, a minor inhibiting effect is observed at ϕ = 0.5, while no effect is found at ϕ = 1.0. The results are also discussed preliminary by considering both the combustion reaction mechanism and the thermophysics properties of the fuel mixtures. The current measurements demonstrate vitiation effects of water vapor and carbon dioxide on the autoignition characteristics of China RP-3 kerosene at air-like O2 concentration. It is important to account for such effects when data are extrapolated from ground testing to real flight conditions.

In the ground tests of hypersonic scramjet,the high-enthalpy airstream produced by burning hydrocarbon fuels often contains contaminants H 2 O and CO 2. The contaminants may cause the ignition characteristics of the fuel to become discrepant between ground tests and real flights. In order to properly assess the effects of the contaminants on ignition characteristics of hydrocarbon fuels,the effects of H 2 O and CO 2 on ignition charateristics of ethylene were investigated in a preheated shock tube. Based on the ignition delay time of ethylene in clean gas,comparative experiments with clean and vitiated gases were conducted. At pressure of 0. 2 MPa,equivalence ratios of 1 and 0. 5,ignition delay time of ethylene were measured for four cases:( 1) clean gas,( 2) gas vitiated with 7. 5%,15% and 25% H 2 O by mole,( 3) gas vitiated with 10% CO 2 by mole,and( 4) gas vitiated with 25% H 2 O and 10% CO 2 by mole. The experimental results show that water vapor and carbon dioxide have almost no effects at equivalence ratio of 0. 5,but an inhibiting effect appears at equivalence ratio of 1. An obviously inhibiting effect appears over a wide temperature range when water vapor and carbon dioxide exist together. The results were also discussed preliminarilyby considering both the combustion reaction mechanism and the thermophysics properties of the test mixtures.

在激波管中利用反射激波后高温环境加热燃料,以燃料点火过程中氢氧自由基特征发射光谱强度的急剧变化作为点火发生的标志,在温度范围800～1 650K,压力0.2 MPa,0.7 MPa,1.2 MPa,化学当量比为0.5,1,2,O2浓度为空气含量20％的条件下,进行了C2H4/O2/Ar混合气在低稀释度条件下点火特性的实验研究.获得了乙烯点火延时随温度、压力、化学当量比、燃料以及氧化剂浓度等参数变化的拟合关系式.对乙烯点火转爆轰现象进行了初步观察,考察了初始温度对乙烯点火特性以及点火转爆轰的影响.

在预加热到135℃的激波管反射激波后5区,以点火过程中OH自由基在306.5 nm处特征发射光谱强度的急剧变化作为点火发生的标志,进行了RP-3航空煤油点火特性的实验研究.实验温度范围为800～1450K,当量比为0.5,1,1.5,压力为0.05,0.1,0.2 MPa,O2的摩尔浓度为空气含量20％.实验获得了低压条件下(0.05,0.1,0.2 MPa) RP-3航空煤油点火延时与点火温度、压力、当量比以及煤油和氧气浓度的依赖关系.将低压实验结果与高压(0.55,1.1,2.2 MPa)条件下煤油点火特性进行了对比.结果显示,当量比对煤油点火特性的影响存在一个临界温度.在临界温度以上的高温区,煤油点火延时随当量比增加而增长;在临界温度以下的低温区,煤油点火延时随当量比增加而缩短;这一临界温度随点火压力的降低而升高.采用3种煤油燃烧反应动力学机理对煤油点火过程进行了动力学数值模拟,并与实验结果进行了对比.结果显示,Honnet等提出的煤油反应机理在高压(2.2 MPa)下与实验结果吻合得很好,而在低压下有一些差异.对不同压力条件下的点火过程进行敏感度分析表明,三体反应H+O2+M=HO2+M在高压时对煤油点火起轻微抑制作用,而在低压时对煤油点火起促进作用.

在单脉冲激波管中反射激波后5区研究碳氢燃料JP-10在1150-1350K条件下的热裂解，用气相色谱法分析裂解产物。主要裂解产物有乙烯、丙烯、丁烯、丁二烯、环戊二烯、环戊烯、苯、甲苯，以及少量的甲烷、乙烷、二甲苯和甲基环戊烯。为了消除激波运行中非理想性和边界层影响导致确定反应温度的误差，采用对比速率法，根据内标物三氟乙烷的裂解产物量确定反射激波后的裂解反应温度，并与测量激波速度依据理想激波关系式计算的温度进行了对比。

Ignition delay times of China No. 3 aviation kerosene were measured behind reflected shock waves using a heated high-pressure shock tube. Experimental conditions covered a wider temperature range of 820–1500 K, at pressures of 5.5, 11 and 22 atm, equivalence ratios of 0.5, 1.0 and 1.5, and oxygen concentration of 20%. Adsorption of kerosene on the shock tube wall was taken into account. Ignition delay times were determined from the onset of the excited radical OH emission in conjunction with the pressure profiles. The experimental results of ignition delay time were correlated with the equations: τ = 3.2 × 10−11[Kerosene]0.22[O2]−1.09 exp(69941/RT) and τ = 4.72×10−7 P −0.88 ϕ 0.23 exp(62092/RT). The current measurements provide the ignition delay behavior of China No. 3 aviation kerosene at high pressures and air-like O2 concentration.

The ignition delay times of kerosene were measured in a preheated shock tube. The test sample composition was determined by directly measuring the kerosene vapor pressure in conjunction with gas chromatography, to account for the adsorption of heavy hydrocarbon fuels on the wall in shock tube experiments. Under conditions for a tailored interface, an experimental observation time of about 6 ms was obtained, consequently the lower temperature bound of experiments was extended to 1000K. The emission of the OH radical at 309nm was observed to identify the time to ignition. Experiments were performed over the pressure range of 1.8-5.0atm, temperature range of 1030-1860K, fuel concentrations of 0.1-0.33% mole fraction, and stoichiometric ratios of π=0.25, 0.5, 1.0, and 2.0. The correlation of the kerosene ignition times with temperature and concentrations of kerosene and oxygen has been obtained experimentally.

The pyrolysis of phenolic resin was studied in a single-pulse shock tube at high temperatures between 1100 K and 1800 K. Considering the very high temperature and short duration time in a shock tube, the heat transfer process of sample particles in high temperature gas was analyzed and the heat equilibrium conditions between the phenolic resin powder and the ambient high temperature gas was also discussed. The pyrolysis product distribution and the pyrolysis rate constants of phenolic resin were determined using gas chromatograph and mass spectrometry. The major pyrolysis products were identified as water, carbon monoxide, hydrogen, acetylene and benzene. The pyrolysis process was divided into the lower and higher temperature regions at the temperature of 1400 K. The different dependency relationships of the pyrolysis rate constant with temperature for the lower and higher temperature regions were obtained.

A method used for the study of thermal decomposition kinetics by peak analysis was developed. This method needs only a few eigenvalues of the thermogravimetric mass loss curves for the determination of kinetic parameters. A peak separation was performed to separate the thermal decomposition of phenolic resin into three stages according to the characteristic of the experimental differential mass loss curve. Kinetic parameters for each stage were determined using peak analysis method. A decomposition kinetic model, which was shown to accurately describe the decomposition process of phenolic resin, was obtained by the combination of these three stages.

The pyrolysis behavior of phenolic formaldehyde resin was studied in a shock tube at high temperatures between 1200K and 1800K.The major hydrocarbon products were identified as methane,ethene,acetylene,benzene and toluene.The variation of the major products distribution with pyrolysis temperature was obtained.It was found that the thermal decomposition of phenolic formaldehyde resin mainly took place at the methylene bridges at the temperatures below 1400K,while the cracking of aromatic framework became the major pyrolysis pathway at the temperatures above 1400K,which gave birth to large amount of acetylene.

The pyrolysis kinetics of phenolic-formaldehyde resin was studied at the temperature range from 1400 to 1700 K using a shock tube. Shock tube experiment can provide a rapid heating rate, which breaks through the limit of traditional heating rate. The major hydrocarbon products were identified as methane, ethene, acetylene and benzne. The effect of diffusion on the pyrolysis process was investigated through analyzing the reaction-diffusion process. It was found that in this experiment the reaction-diffusion process got constant rapidly, and the effect of diffusion was neglectable. The pyrolysis rate constant of phenolic resin under the pyrolysis mechanism of aromatic framework cracking was obtained for the first time.

JP-10 (exo-tetrahydrodicyclopentadiene, C10H16) ignition delay times were measured in a preheated shock tube. The vapor pressures of the JP-10 were measured directly by using a high-precision vacuum gauge, to remedy the difficulty in determining the gaseous concentrations of heavy hydrocarbon fuel arising from the adsorption on the wall in shock tube experiments. The whole variation of pressure and emission of the OH or CH radicals were observed in the ignition process by a pressure transducer and a photomultiplier with a monochromator. The emission of the OH or CH radicals was used to identify the time to ignition. Experiments were performed over the pressure range of 151-556 kPa, temperature range of 1000-2100 K, fuel concentrations of 0.1%-0.55% mole fraction, and stoichiometric ratios of 0.25, 0.5, 1.0 and 2.0. The experimental results show that for the lower and higher temperature ranges, there are different dependency relationships of the ignition time on the temperature and the concentrations of JP-10 and oxygen.

On the basis of the ignition experiments of JP10 and kerosene, experimentswere carried out to study the effect of silane addition on ignitioncharacteristics of these two typical heavy hydrocarbon fuels behindreflected shock waves over the temperature range of 880$\sim$1800K and pressurerange of 0.16~0.53MPa.A longer observation time is required as the ignition time increases at thelower temperature region. The shock tube worked under conditions for atailored interface, resulting in an observation time of about 7ms, and thelower temperature bound of experiments was extended in the current study.The uncertainty in the concentration of the fuel vapor due to the adsorptionof the fuel vapor on the shock tube wall is one of the largest sources oferrors in ignition time measurements of heavy hydrocarbon fuels, thus thegaseous concentrations of JP10 and kerosene were determined in the shocktube by measuring the gas pressure with a high-precision vacuum gaugecombined with gas chromatography. Since kerosene is a complex mixture ofmany hydrocarbon components, the adsorption content of differentcomponents differs, so the gas composition different from the liquidcomposition. In the present study, a simulant modified fuel for kerosene wasprepared by adding some heavy hydrocarbon components into the originalkerosene in proportion to the adsorption content to compensate the loss inthe gas phase through the adsorption. To minimize the degree of adsorptionand increase the test fuel vapor pressure, the shock tube was preheated andmaintained at 70 C throughout the experiments. The conditions behindthe reflected shock were calculated from the incident shock speed using theone-dimensional shock relations. A quartz window was installed on thesidewall very close to the endplate of the driven section to monitor theemission from the ignition process in the reflected shock region. Theemission focused through a lens was detected by using a photomultiplierafter passing through a monochromator centered at the emission line of OHradical at 306.5nm as a marker to identify the instant of ignition.When the molar ratio of the added silane with the fuel was in the range of10%$\sim$15{%}, the corresponding mass ratio was 2%~3{%}, a significantreduction in the ignition delay time was observed experimentally. Anincrease of the additionof silane shortened the ignition delay for JP10 at the lower endof temperature range studied. Specifically, the ignition time for JP10decreased from 3.7 to 0.87ms at 1100K and from 0.17 to 0.10ms at1500K. By contrast, the addition of silane shortened the ignition delay for kerosenethroughout the temperature range considered. Specifically, the ignition timefor kerosene decreased from 3.6 to 0.91ms at 1000K and from 0.75to 0.16ms at 1220K. The results presented herein are useful for the engine design andfuel selection in supersonic combustion researches, and also can be used tovalidate chemical kinetics models of heavy hydrocarbon fuel combustion withsilane addition.

On the basis of the ignition experiments of JP-10 and kerosene in shock tube,the experiments of effect of enhancers,nitromethane and dichlormethane, on ignition characteristics of JP-10 and kerosene were performed.Under conditions for a tailored interface in a preheated shock tube,the experimental time of about 7 ms was obtained.The whole variation of the OH radical emission at 306.5nm was observed in the ignition process by a monochromator with a photomultiplier,to identify the time to ignition.When the molar ratio of the added enhancer with the fuel accounted for 10%～20%,correspondingly the mass ratio was 5%～12%,a significant reduction in ignition time was observed experimentally.Specifically,at 1100K the addition of 10% mole ratio of CH3NO2 produced a 70% reduction in the ignition time for JP-10.The ignition time of kerosene were shortened effectively,when 10%～15% mole ratio of CH3NO2 was added,correspondingly the mass ratio was 5%～6%.Specifically,at 1000K the ignition time for kerosene decreased by 50%.

在JP-10点火延时的激波管实验中,JP-10在激波管壁的吸附导致气相浓度的不确定是测量结果分散的主要原因之一.利用精确测定的吸附曲线确定了实验时JP-10真实的气相浓度,解决了高碳数碳氢燃料点火延时激波管实验时管壁吸附影响燃料气相浓度确定的困难.实验显示JP-10的吸附符合Langmuir吸附等温关系.

In shock tube measurements of the JP-10 ignition delay time, the uncertainty of the gas concentration due to the adsorption of JP-10 in shock tube is one of the main reasons resulting in large scatter of measurement data. By measuring the adsorption curve accurately, the gas concentrations were determined, which overcomes the difficulty in determining the gas concentrations of heavier hydrocarbon fuels due to the adsorption on the wall in shock tube experiments. The present results of experiments show that the adsorption of JP-10 is in accord with Langmuir's adsorption isotherm.

To study electron affinity kinetics, a shock tube method was applied, in which the test gas was ionized by a reflected shock wave and subsequently quenched by a strong rarefaction wave. As the quenching speed of 106 K/s was reached, a nonequilibrium ionization-recombination process occurred, which was dominated by ion recombination with electrons. A Langmuir electrostatic probe was used to monitor variation in the ion number density at the reflection shock region. The working state of the probe was analyzed, and a correction was introduced for reduction of the probe current due to elastic scattering in the probe sheath. The three-body electron affinity rate coefficient of the fluorine atom over the temperature range 1200 to 2200 K in an ambiance of argon gas was directly determined. The temperature dependence of electron affinity rate coefficient was discussed.

A shock tube method is introduced to study the ionization-recombination kinetics of high temperature gas, in which a test gas is heated and ionized by a reflected shock wave and subsequently quenched by a strong rarefaction wave reflected on the end wall of the driver section as the main cooling wave associated with a rarefaction wave incident back into region 5 when the reflected shock wave interacts with the contact surface. As the quenching rate of the strong rarefaction wave reaches 10(6) K/s, a nonequilibrium ionization-recombination process occurs, during which the ion recombination with electrons dominates.