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1.
用自行设计激波管点火测试技术,实验研究了温度范围760-1380K间入射激波诱导下环氧丙烷的点火机理。利用激波管压力传感器测定了H*(486.1) 和O (470.5nm)随激波诱导强度变化的点火时间特征。实验结果表明:在低马赫数下氢氧自由基出现时间较接近,1.5-2.5马赫间随激波诱导强度增大而线性减小;而马赫大于2.5后,氧自由基的出现时间迅速减小,是由于高活化能的氧自由基的点火时间对强激波较敏感,而诱导强度大于3.5马赫后对两者点火影响区别就下明显了。实验数据将有益于含能材料点火时间的研究。  相似文献   

2.
利用OH自由基特征发射谱测量正庚烷的点火延迟时间   总被引:2,自引:0,他引:2  
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。  相似文献   

3.
文章提出了一种采用圆柱形汇聚激波实现可燃气体点火特性研究的新方法.通过采用激波动力学理论合理地设计壁面型线, 将激波管中产生的平面运动激波近乎连续地转变为扇形区内圆柱形汇聚激波.以氢氧预混气体为考察对象, 开展了相关激波管实验, 实现了可控圆柱面激波汇聚诱导点火.实验发现两种点火现象:强点火和弱点火.在强点火过程中, 点火由入射激波直接诱导产生; 而在弱点火过程中, 点火则是在波后气流经历热压缩过程后发生.   相似文献   

4.
为了研究柴油的最小点火能量,分别在激波管和外场模拟油箱中开展了-10号柴油的点火引燃实验。激波管实验结果表明,柴油-空气云雾的最小点火能量与柴油-空气当量比近似呈"L"型曲线关系,在当量比为1.31时,最小点火能量达到极小值0.16MJ/m2(约5.02kJ);外场实验结果表明,油液区的最小点火能量是油-蒸汽区的6.74倍,并且油-蒸汽区的最小点火能量不随柴油量的变化而改变,油液区的最小点火能量则随柴油量增加而线性增大。在柴油量为21mL时,外场实验测定的油液区最小点火能量为36.42kJ,是激波管实验最小点火能量极值的7.25倍。  相似文献   

5.
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。  相似文献   

6.
JP-10点火延时的激波管研究   总被引:2,自引:0,他引:2  
在预加热激波管上测定了JP-10的点火延时时间.采用高精度真空仪直接测定注入激波管中JP-10蒸气压力,获得了JP-10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.采用压力传感器、单色仪和光电倍增管记录得到了完整的点火过程引起的压力变化和OH或CH自由基发射强度变化.自由基发射信号作为诊断点火发生的手段.当实验压力为151?556 kPa,温度为1000?2120 K,JP-10摩尔百分比为0.1%?0.55%,化学当量比为0.25、0.5、1.0、2.0时,获得了点火延时时间与实验温度、JP-10浓度、O2浓度的依赖关系,结果还表明,高温区和低温区呈现出不同的依赖关系.  相似文献   

7.
气相爆轰波在分叉管中传播现象的数值研究   总被引:1,自引:0,他引:1  
数值研究气相爆轰波在分叉管中的传播现象.用二阶附加半隐龙格-库塔法和5阶WENO格式求解二维欧拉方程,用基元反应描述爆轰化学反应过程,得到了密度、压力、温度、典型组元质量分数场及数值胞格结构和爆轰波平均速度.结果表明:气相爆轰波在分叉管中传播,分叉口左尖点的稀疏波导致诱导激波后压力、温度急剧下降,诱导激波和化学反应区分离,爆轰波衰减为爆燃波(即爆轰熄灭).分离后的诱导激波在垂直支管右壁面反射,并导致二次起爆.畸变的诱导激波在水平和垂直支管中均发生马赫反射.分叉口上游均匀胞格区和分叉口附近大胞格区的边界不是直线,其起点通常位于分叉口左尖点上游或恰在左尖点.水平支管中马赫反射三波点迹线始于右尖点下游.分叉口左尖点附近的流场中出现了复杂的旋涡结构、未反应区及激波与旋涡作用.旋涡加速了未反应区的化学反应速率.反射激波与旋涡作用并使旋涡破碎.反射激波与未反应区作用,加速其反应消耗,并形成一个内嵌的射流.数值计算得到的波系演变和胞格结构与实验定性一致.  相似文献   

8.
炎正馨 《物理学报》2011,60(7):76202-076202
对比研究了入射激波诱导下纳米铝粉和微米铝粉与环氧丙烷混合物快速反应系统中的爆炸特征.利用多台单色谱仪同步采集技术实验测定了二种反应混合物在不同诱导激波中强度作用下的点火延迟时间.为获得爆炸系统内部信息利用扫描电子显微镜(SEM),X射线衍射分析仪(XRD),X射线能谱(XPS)对相应铝粉反应生成物的结构、态貌、表面氧化层厚度进行了表征和分析.结果表明:TEM结果表明纳米铝粉生成物为絮状、针状和纤维状,而微米铝粉生成物为球状且体积增大;XRD结果显示在压缩区、点火区、燃烧区、爆炸区、传播区、碎片压缩致冷区生 关键词: 诱导激波 点火 XPS能谱 铝粉  相似文献   

9.
激波与层流/湍流边界层相互作用实验研究   总被引:1,自引:0,他引:1       下载免费PDF全文
全鹏程  易仕和  武宇  朱杨柱  陈植 《物理学报》2014,63(8):84703-084703
在超声速风洞中,分别对层流和湍流来流条件下的边界层和斜激波(激波强度足以引起流动分离)相互干扰进行了实验研究,利用纳米粒子示踪平面激光散射(NPLS)技术获得了两种条件下流场的精细结构图像;利用粒子图像测速(PIV)技术获得了两种条件下流场的速度场和涡量场;综合运用NPLS结果和PIV结果对比分析了两种流动的瞬时流动结构和时间相关性,实验结果表明:层流边界层内的分离区呈现出狭长的条状,而湍流边界层内分离区呈现出较规则的椭圆;在入射激波上游距入射点较远的位置,层流边界层外围拟序结构会诱导出一系列压缩波系,进而汇聚成空间位置不稳定的诱导激波,而湍流边界层则是在入射激波上游较近的地方直接形成较强且稳定的诱导激波;在入射激波下游,层流边界层内的膨胀区域较小且急促,膨胀后产生的再附激波很弱,而湍流边界层内的膨胀区域较大,膨胀后产生的激波较强。  相似文献   

10.
本文通过搭建流动与换热实验平台,对10 PPI,30 PPI,70 PPI三种不同孔密度的不锈钢金属泡沫填充管的换热性能进行了实验研究,分析了管内入口雷诺数、入口温度以及孔密度对管外壁Nu数的影响。研究结果表明,金属泡沫填充管的换热强度较光管条件下提高,且30 PPI和70 PPI的换热强度都大于10 PPI填充管的换热强度;在本文的研究工况下,金属泡沫填充管的管外壁Ⅳu数随管内雷诺数的增大变化不明显,随管内入口温度的增加而增大;三种金属泡沫填充管的换热综合评价因子都大于1,且基本不随雷诺数的变化而变化。  相似文献   

11.
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.  相似文献   

12.
Ignition delay times for methyl oleate (C19H36O2, CAS: 112-62-9) and methyl linoleate (C19H34O2, CAS: 112-63-0) were measured for the first time behind reflected shock waves, using an aerosol shock tube. The aerosol shock tube enabled study of these very-low-vapor-pressure fuels by introducing a spatially-uniform fuel aerosol/4% oxygen/argon mixture into the shock tube and employing the incident shock wave to produce complete fuel evaporation, diffusion, and mixing. Reflected shock conditions covered temperatures from 1100 to 1400 K, pressures of 3.5 and 7.0 atm, and equivalence ratios from 0.6 to 2.4. Ignition delay times for both fuels were found to be similar over a wide range of conditions. The most notable trend in the observed ignition delay times was that the pressure and equivalence ratio scaling were a strong function of temperature, and exhibited cross-over temperatures at which there was no sensitivity to either parameter. Data were also compared to the biodiesel kinetic mechanism of Westbrook et al. (2011) [10], which underpredicts ignition delay times by about 50%. Differences between experimental and computed ignition delay times were strongly related to existing errors and uncertainties in the thermochemistry of the large methyl ester species, and when these were corrected, the kinetic simulations agreed significantly better with the experimental measurements.  相似文献   

13.
Ignition times and autoignition modes for propane–air mixtures have been studied behind reflected shock waves. Experiments were performed over temperatures between 1000 and 1750 K, pressures between 2 and 20 atm, and equivalence ratios of = 0.5, 1.0, and 2.0. Ignition delay times were determined using pressure measurements, C2 emission profiles, and luminosity measurements in the visible spectrum (380–680 nm). Empirical correlations for ignition time for low temperature (1000–1300 K) and high temperature (1300–1800 K) ranges have been deduced from the experimental data. Different autoignition modes of the mixture (strong, transient, and weak) were identified by comparing velocities of reflected shock wave at different distances from the reflecting wall.  相似文献   

14.
 采用数值模拟的方法研究了激光重复频率、点火位置及来流马赫数等参数对激光能量沉积减小超声速钝头体波阻的影响。数值模拟结果表明,由于激光能量的沉积产生的低密度区与弓形激波相互作用,在钝头体前形成了类似虚拟尖锥的回流区,使原弓形激波逐渐向阻力较小的斜激波转变。阻力随着频率的增加而减小,当频率增加到200 kHz时,阻力减小到约为原来的17%,能量效率的最大值出现在频率为50 kHz处。说明控制参数的选择对减阻性能起着关键的作用。  相似文献   

15.
 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。  相似文献   

16.
The direct simulation Monte Carlo method is used to numerically simulate the problem of the shock wave front in vibrationally excited hydrogen flowing in the low-pressure channel of a shock tube. It is assumed that the vibrational temperature of the hydrogen equals 3000 K. The cases of partially and completely excited hydrogen are considered. Equilibrium hydrogen is applied as a pusher gas, but its concentration is 50 times higher than the hydrogen concentration in the low-pressure channel. In addition, the strength of the shock wave is varied by heating the pusher gas. It has been shown that, if the prestored vibrational energy is weakly converted to translational energy, the shock wave slows down over time. If the energy conversion is sufficiently intense, when the pusher gas is warm and only completely vibrationally excited hydrogen is in the low-pressure channel, the wave gains speed over time (its velocity increases roughly by a factor of 1.5). This causes physical detonation, in which case the parameters of the wave become dependent on the vibrational-to-thermal energy conversion and independent of the way of its initiation.  相似文献   

17.
Shock tube ignition delay times were measured for DF-2 diesel/21% O2/argon mixtures at pressures from 2.3 to 8.0 atm, equivalence ratios from 0.3 to 1.35, and temperatures from 900 to 1300 K using a new experimental flow facility, an aerosol shock tube. The aerosol shock tube combines conventional shock tube methodology with aerosol loading of fuel-oxidizer mixtures. Significant efforts have been made to ensure that the aerosol mixtures were spatially uniform, that the incident shock wave was well-behaved, and that the post-shock conditions and mixture fractions were accurately determined. The nebulizer-generated, narrow, micron-sized aerosol size distribution permitted rapid evaporation of the fuel mixture and enabled separation of the diesel fuel evaporation and diffusion processes that occurred behind the incident shock wave from the chemical ignition processes that occurred behind the higher temperature and pressure reflected shock wave. This rapid evaporation technique enables the study of a wide range of low-vapor-pressure practical fuels and fuel surrogates without the complication of fuel cracking that can occur with heated experimental facilities. These diesel ignition delay measurements extend the temperature and pressure range of earlier flow reactor studies, provide evidence for NTC behavior in diesel fuel ignition delay times at lower temperatures, and provide an accurate data base for the development and comparison of kinetic mechanisms for diesel fuel and surrogate mixtures. Representative comparisons with several single-component diesel surrogate models are also given.  相似文献   

18.
The interaction of a shock wave with a turbulent air flow is investigated experimentally. The turbulence was created with the aid of a grid. On its reflection from a perforated disc the wave propagated through a turbulent flow. The Mach number of the incident shock was equal to 1.9–4, the Mach number of the reflected wave was equal to 1.6–2.5. We found the autocorrelation functions of pressure fluctuations and their phase diagrams. The turbulent length scale of pressure fluctuations behind the incident shock was determined. The appropriate quantity behind the reflected wave is less of an order as compared with the previous case. It is established that the pressure behind the reflected wave in the turbulent flow is 7–8% higher as compared with the pressure in the laminar flow, if other conditions are the same.  相似文献   

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