我国岩土与工程研究的现状与展望——第三届全国岩土与工程大会学术总结

采用激波管方法研究了酚醛树脂在温度范围1100K～1800K之间的热解过程。在激波管高温和短实验时间的条件下,分析了实验样品颗粒在高温气相中的传热过程,讨论了样品颗粒达到热平衡的条件。通过色谱和质谱方法检测热解产物,获得了酚醛树脂高温热解产物分布和热解速率常数。酚醛树脂高温热解最主要的产物为水、一氧化碳、氢、乙炔和苯。温度1400K将酚醛树脂热解分为高温和低温区,分别表现出不同的热解速率常数与温度的关系。 关键词：酚醛树脂,热解,再入过程,激波管,质谱分析,色谱分析     

JP-10裂解的激波管实验与动力学模拟

利用单脉冲激波管对碳氢燃料JP-10在1150~1300K条件下的高温热裂解特性进行了实验研究,采用气相色谱法分析热裂解产物并获得了热裂解速率系数.主要裂解产物有乙烯、乙炔、丙烯、丁烯、1,3-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.将每次激波管实验后所有产物浓度累加, JP-10裂解速率系数由实验测定.为了消除激波运行中非理想性和边界层效应导致反应温度确定的误差,采用对比速率法确定裂解温度,即在反应物中加入少量热解速率已知的内标物,根据内标物在相同的激波管实验条件下的裂解程度确定反应温度.根据内标物裂解量确定的激波管裂解反应温度通常小于采用传统测量激波速度由激波关系计算的反射激波后5区温度.在1200~1300K之间两种方法得到的温度吻合得较好,差异在20K以内,随着温度升高,两者差异增大.在实验研究的基础上,依据San Diego Mechanism对JP-10高温裂解过程进行了动力学模拟.结果显示:主要裂解产物中乙烯、乙炔和1,3-丁二烯产量随温度变化的实验值与San Diego Mechanism的模拟结果有很好的一致性,但环戊烯产量的实验值比模拟值高很多,预示JP-10裂解中完全开环和部分开环反应都是重要的裂解通道.      

JP-10裂解的激波管实验与动力学模拟

利用单脉冲激波管对碳氢燃料JP-10在1150～1300 K条件下的高温热裂解特性进行了实验研究,采用气相色谱法分析热裂解产物并获得了热裂解速率系数.主要裂解产物有乙烯、乙炔、丙烯、丁烯、1,3-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.将每次激波管实验后所有产物浓度累加, JP-10裂解速率系数由实验测定.为了消除激波运行中非理想性和边界层效应导致反应温度确定的误差,采用对比速率法确定裂解温度,即在反应物中加入少量热解速率已知的内标物,根据内标物在相同的激波管实验条件下的裂解程度确定反应温度.根据内标物裂解量确定的激波管裂解反应温度通常小于采用传统测量激波速度由激波关系计算的反射激波后5区温度.在1200～1300 K之间两种方法得到的温度吻合得较好,差异在20K以内,随着温度升高,两者差异增大.在实验研究的基础上,依据San Diego Mechanism对JP-10高温裂解过程进行了动力学模拟.结果显示:主要裂解产物中乙烯、乙炔和1,3-丁二烯产量随温度变化的实验值与San Diego Mechanism的模拟结果有很好的一致性,但环戊烯产量的实验值比模拟值高很多,预示JP-10裂解中完全开环和部分开环反应都是重要的裂解通道.     

激波管研究—氯化碘高温气相分解反应动力学

我们建立了一套激波管高温快速反应动力学实验装置。利用双光路分光吸收技术研究了一氯化碘分子在1000—2000°K之间解离的动力学过程,测得了M反应以及反应的速率常数。我们发现,Ⅰ原子和氯原子的三体复合速率K_(-1)比Ⅰ原子和Ⅰ原子之间的三体复合速率要大一个数量级,而且有较大的负温度系数,这可用Cl和Ar之间生成Cl-Ar自由基复合物的理论来解释。     

高温激波管化学非平衡流动数值模拟研究

为了预测氢氧定容燃烧驱动的高温激波管性能,需要准确分析激波管非定常化学非平衡流动过程.本文在破膜前的驱动段定容燃烧以及破膜后的化学非平衡流动数值模拟中,引入双时间步长方法,发展高温激波管化学非平衡流动数值模拟方法,该方法在时间上具有二阶精度.计算结果与目前存在的激波管流动解析解以及零维化学反应系统的数值解进行了比较,吻合较好.对于典型高温激波管状态,采用有限体积方法离散准一维流动Euler控制方程,并通过将流动过程和化学反应动力学过程耦合求解,获得了激波管内部的化学非平衡流动特征.     

钠离子与电子复合电离动力学的激波管研究基金项目

利用反射激波加热使试验气体电离,继之以强稀疏波快速冷却,构成一种新的激波管方法,并测定了在氩气氛中钠离子与电子三体复合速率系数.由于稀疏波冷却速度达106K/s,电离过程处于非平衡状态.选用氨基钠作为向实验体系中引入钠离子的源物质.用压电传感器和Langmuir静电探针分别监测反射激波后5区压力和离子浓度变化.稀疏波的冷却过程被视为绝热的.分析了探针工作状态,引入了探针鞘层内的弹性散射修正.测定了在800～2600K温度范围内以惰性气体氩为碰撞第三体的钠离子与电子电离复合速率系数kr＝3.43×10-14T-3.77cm6s-1.     

疏导式热防护在翼前缘中的应用探索

针对高超声速飞行器飞行时翼前缘存在着严重的气动加热问题,为了保证翼前缘的尖锐外形,提出疏导式热防护结构,利用内置高温热管结构为翼前缘提供热防护。采用数值模拟和电弧风洞试验的方法对翼前缘疏导式结构进行了分析,得到翼前缘内置高温热管具有的防热效果。数值模拟结果表明在一定热环境条件下,翼前缘驻点温度下降了304 K,尾部最低温度升高了130 K,实现了热流从高温区到低温区的疏导,减弱了翼前缘的热载荷,强化了翼前缘的热防护能力。通过电弧风洞试验可以获得相同的热防护结果,并且在一定飞行条件下高温热管可以自适应启动,验证了数值模拟方法的准确性以及翼前缘内置高温热管疏导式热防护结构的可行性。     

铝颗粒激波点火机制初探

通过对铝颗粒在激波后的高温热气流中由于温度升高产生的热应力进行分析计算 ,对铝颗粒的激波点火机制进行初步探讨。计算结果表明在激波后的气流中 ,铝颗粒的温度只要升高 70C左右 ,铝颗粒的氧化层就会产生裂纹。当铝颗粒的铝完全熔化后 ,如果这时气流对颗粒的作用使得已经产生裂纹的氧化层进一步破裂并失去对铝的保护 ,铝颗粒将被点火 ;但如果此时气流对铝颗粒的作用未能使氧化层失去保护作用 ,铝颗粒的温度需达到或接近三氧化二铝的熔点时才能被点火。     

HEAT-PIPE-COOLED THERMAL PROTECTION FOR THE LEADING EDGE OF THE WING

针对高超声速飞行器飞行时翼前缘存在着严重的气动加热问题，为了保证翼前缘的尖锐外形，提出疏导式热防护结构，利用内置高温热管结构为翼前缘提供热防护。采用数值模拟和电弧风洞试验的方法对翼前缘疏导式结构进行了分析，得到翼前缘内置高温热管具有的防热效果。数值模拟结果表明在一定热环境条件下，翼前缘驻点温度下降了304K，尾部最低温度升高了130K，实现了热流从高温区到低温区的疏导，减弱了翼前缘的热载荷，强化了翼前缘的热防护能力。通过电弧风洞试验可以获得相同的热防护结果，并且在一定飞行条件下高温热管可以自适应启动，验证了数值模拟方法的准确性以及翼前缘内置高温热管疏导式热防护结构的可行性。     

高温非平衡流动中的氧分子振动态精细分析

高超声速流动在头激波压缩后常处于高 温条件下的热化学非平衡状态. 本文采用态-态方法和双温度模型计算分析了一维正激波后和高超声速钝体绕流驻点线上的氧气热化学非平衡流动. 态-态方法将氧气的每个振动能级当成独立的组分,通过耦合 Euler 方程或驻点线上的降维 Navier-Stokes 方程,数值求解得 到了高温流动中的精细热化学非平衡状态. 而双温度模型假设氧气的振动能级服从 Boltzmann 分布,通过求解振动能方程得到振动温度. 一维正激波后热化学松弛过程的计算结果表明,态-态计算预测的温度分布和氧原子浓度分布较好地吻合了文 献中的实验结果,而经典的双温度模型的预测结果误差较大,且不同双温度模型的计算结果比较发散. 态-态方法详细地给出了所有振动能级的变化过程. 无论是正激波还是脱体激波后的流场,都是高振动能级首先得到激发;但是数密度大的低振动能级先达到热平衡,而高能级 分子要经过很长距离后才能达到热平衡. 在驻点附近,复合反应生成的氧气分子处于高振动能级,导致高振动能级分子数密度显著高于平衡分布. 计算还发现,经典双温度模型的离解反应速率明显偏离态-态计算结果,无法准确体现振动离解耦合效应对离解反应 速率的影响,但是 Park 双温度模型将离解失去的振动能取为 0.3$\sim 高超声速流动在头激波压缩后常处于高 温条件下的热化学非平衡状态. 本文采用态-态方法和双温度模型计算分析了一维正激波后和高超声速钝体绕流驻点线上的氧气热化学非平衡流动. 态-态方法将氧气的每个振动能级当成独立的组分,通过耦合 Euler 方程或驻点线上的降维 Navier-Stokes 方程,数值求解得 到了高温流动中的精细热化学非平衡状态. 而双温度模型假设氧气的振动能级服从 Boltzmann 分布,通过求解振动能方程得到振动温度. 一维正激波后热化学松弛过程的计算结果表明,态-态计算预测的温度分布和氧原子浓度分布较好地吻合了文 献中的实验结果,而经典的双温度模型的预测结果误差较大,且不同双温度模型的计算结果比较发散. 态-态方法详细地给出了所有振动能级的变化过程. 无论是正激波还是脱体激波后的流场,都是高振动能级首先得到激发;但是数密度大的低振动能级先达到热平衡,而高能级 分子要经过很长距离后才能达到热平衡. 在驻点附近,复合反应生成的氧气分子处于高振动能级,导致高振动能级分子数密度显著高于平衡分布. 计算还发现,经典双温度模型的离解反应速率明显偏离态-态计算结果,无法准确体现振动离解耦合效应对离解反应 速率的影响,但是 Park 双温度模型将离解失去的振动能取为 0.3$\sim $0.5 倍分子离解能是比较合理的.     

Effect of wall heat transfer on shock-tube test temperature at long times

When performing chemical kinetics experiments behind reflected shock waves at conditions of lower temperature (<1,000 K), longer test times on the order of 10–20 ms may be required. The integrity of the test temperature during such experiments may be in question, because heat loss to the tube walls may play a larger role than is generally seen in shock-tube kinetics experiments that are over within a millisecond or two. A series of detailed calculations was performed to estimate the effect of longer test times on the temperature uniformity of the post-shock test gas. Assuming the main mode of heat transfer is conduction between the high-temperature gas and the colder shock-tube walls, a comprehensive set of calculations covering a range of conditions including test temperatures between 800 and 1,800 K, pressures between 1 and 50 atm, driven-tube inner diameters between 3 and 16.2 cm, and test gases of N₂ and Ar was performed. Based on the results, heat loss to the tube walls does not significantly reduce the area-averaged temperature behind the reflected shock wave for test conditions that are likely to be used in shock-tube studies for test times up to 20 ms (and higher), provided the shock-tube inner diameter is sufficiently large (>8cm). Smaller diameters on the order of 3 cm or less can experience significant temperature loss near the reflected-shock region. Although the area-averaged gas temperature decreases due to the heat loss, the main core region remains spatially uniform so that the zone of temperature change is limited to only the thermal layer adjacent to the walls. Although the heat conduction model assumes the gas and wall to behave as solid bodies, resulting in a core gas temperature that remains constant at the initial temperature, a two-zone gas model that accounts for density loss from the core to the colder thermal layer indicates that the core temperature and gas pressure both decrease slightly with time. A full CFD solution of the shock-tube flow field and heat transfer at long test times was also performed for one typical condition (800 K, 1 atm, Ar), the results of which indicate that the simpler analytical conduction model is realistic but somewhat conservative in that it over predicts the mean temperature loss by a few Kelvins. This paper presents the first comprehensive study on the effects of long test times on the average test gas temperature behind the reflected shock wave for conditions representative of chemical kinetics experiments.     

Experimental investigation of CO vibrational deactivation in a supersonic cooling gas flow

Abstract. The vibrational relaxation time of CO molecules at collisions with H atoms was measured in shock tube experiments by means of the CARS-spectroscopy method. The measurements of the CO vibrational temperature at gas temperatures of 1800–3000 K were performed in a supersonic cooling gas flow. The gas was heated behind the incident and reflected shock wave and then flowed out of a wedge-shaped nozzle. H atoms were generated in the reflected shock wave because of dissociation of H and HO admixtures. The extremely high efficiency of H atoms in CO vibrational deactivation was confirmed. Received 1 February 2000 / Accepted 20 February 2000     

Near-wall imaging using toluene-based planar laser-induced fluorescence in shock tube flow

A quantitative thermometry technique, based on planar laser-induced fluorescence (PLIF), was applied to image temperature fields immediately next to walls in shock tube flows. Two types of near-wall flows were considered: the side wall thermal boundary layer behind an incident shock wave, and the end wall thermal layer behind a reflected shock wave. These thin layers are imaged with high spatial resolution (15μm/pixel) in conjunction with fused silica walls and near-UV bandpass filters to accurately measure fluorescence signal levels with minimal interferences from scatter and reflection at the wall surface. Nitrogen, hydrogen or argon gas were premixed with 1–12% toluene, the LIF tracer, and tested under various shock flow conditions. The measured pressures and temperatures ranged between 0.01 and 0.8 bar and 293 and 600 K, respectively. Temperature field measurements were found to be in good agreement with theoretical values calculated using 2-D laminar boundary layer and 1-D heat diffusion equations, respectively. In addition, PLIF images were taken at various time delays behind incident and reflected shock waves to observe the development of the side wall and end wall layers, respectively. The demonstrated diagnostic strategy can be used to accurately measure temperature to about 60 μm from the wall.     

爆轰驱动惰性气体磁流体发电试验研究

磁流体发电装置作为一种特殊的高功率脉冲电源,具有效率高、容量大、启动快的优点,制约其发展的关键在于如何获得高电导率的发电工质.爆轰驱动具有远超常规方式的驱动能力,在提供高温、高电导率气体方面独具优势.将爆轰驱动激波管技术应用于磁流体发电,有利于突破磁流体发电技术瓶颈,故据此开展了基于爆轰驱动激波管技术的惰性气体磁流体发电试验研究.爆轰驱动根据激波管点火位置不同分为反向和正向两种运行模式,反向爆轰驱动可提供时间较长、状态稳定的试验气流,而正向爆轰优势在于产生高焓试验气流.试验系统由爆轰驱动激波管、拉瓦尔喷管、发电通道、电磁铁和真空罐等组成,试验中分别以反向爆轰和正向爆轰驱动激波管产生发电工质,利用激波将惰性气体压缩至高温从而发生电离,形成的等离子体经喷管加速后,最终在法拉第直线型发电机内切割磁感线输出电能.磁场强度0.9 T的条件下,反向爆轰在负载3.5Ω时获得了较稳定的1.9 kW输出功率,持续时间1.5 ms;外接35 mΩ负载时,正向爆轰在0.3 ms内短时输出功率高达212 k W,功率密度为0.2 GW/m³.试验成功验证了基于爆轰驱动激波管技术的惰性气体...     

硅烷对JP10和煤油点火特性影响的激波管研究

在JP10和煤油点火特性激波管实验的基础上，实验研究了硅烷对这两种典型高碳数碳氢燃 料点火特性的影响. 在预加热到70 C的激波管上，采用缝合运行条件获得了近7ms 的实验时间，将实验延伸至低温区. 采用气相色谱分析和高精度真空仪直接测定压力相结合 的方法，确定了燃料气相浓度，解决了高碳数碳氢燃料点火激波管实验时由于管壁吸附影响 燃料气相浓度确定的困难. 实验记录了点火过程中OH自由基发射强度变化，并作为判断点 火发生的标志. 实验温度范围880~1800K, 压力范 围0.16~0.53\,MPa. 当硅烷加入量约为燃料的10%~15%(摩尔比)， 质量比为2%~3%, 观测到明显的点火促进作用. 该研究对超燃研究中发动机设计、 燃料选择等方面具有直接的工程意义，也可用于检验燃烧化学动力学模型的合理性.     

Evaluation of an energy relaxation method for the simulation of unsteady,viscous, real gas flows

This study investigates a new energy relaxation method designed to capture the dynamics of unsteady, viscous, real gas flows governed by the compressible Navier–Stokes equations. We focus on real gas models accounting for inelastic molecular collisions and yielding temperature‐dependent heat capacities. The relaxed Navier–Stokes equations are discretized using a mixed finite volume/finite element method and a high‐order time integration scheme. The accuracy of the energy relaxation method is investigated on three test problems of increasing complexity: the advection of a periodic set of vortices, the interaction of a temperature spot with a weak shock, and finally, the interaction of a reflected shock with its trailing boundary layer in a shock tube. In all cases, the method is validated against benchmark solutions and the numerical errors resulting from both discretization and energy relaxation are assessed independently. Copyright © 2004 John Wiley & Sons, Ltd.     

Characteristics of an annular vertical diaphragmless shock tube

Abstract. This paper reports on the characteristics of a compact vertical diaphragmless shock tube, which was constructed and tested in the Shock Wave Research Center to study experimentally the behavior of toroidal shock waves. It is 1.15 m in height and has a self-sustained co-axial vertical structure consisting of a 100 mm i.d. outer tube and an 80 mm o.d. inner tube. To create a ring shaped shock wave between the inner and outer tubes, a rubber sheet is inserted to separate a high pressure driver gas from a test gas, which is bulged with auxiliary high pressure helium from the behind. When the rubber membrane is contracted by the sudden release of the auxiliary gas so as to break the seal, shock waves are formed. Special design features of the shock tube are described and their role in producing repeatable shock waves is discussed. Its special opening characteristics make possible the production of annular shaped shock waves that are unlikely met with a conventional tube that uses rupturing diaphragms. Performance of the shock tube is evaluated in terms of the shock wave Mach numbers and the measured flow properties. It eventually showed a higher degree of repeatability and the scatter in the shock wave Mach numbers Ms was found to be 0.2% for Ms ranging from 1.1 to 1.8. The shock wave Mach number so far measured agreed very well with the simple shock tube theory. Received 3 February 1999 / Accepted 6 April 2000     

Sand attrition in conical spouted beds

A study was carried out on the attrition in conical spouted beds using two sands with different properties for several bed heights and gas flow rates. Furthermore, the influence of a draft tube was studied at ambient and high temperatures. The main objective was to acquire knowledge on the attrition of sand beds for biomass pyrolysis in a pilot plant provided with a conical spouted bed reactor. A first-order kinetic equation is proposed for sand attrition in a conical spouted bed at room temperature. The predicted attrition rate constant depends exponentially on excess air velocity over that for minimum spouting. Both the draft tube and temperature increase contribute to reduction of attrition.     

IR-diode laser measurements on the decomposition of NO behind shock waves

The decomposition of NO diluted in Ar was measured in the temperature range 2,500 K T 3,500 K at pressures between 0.5 and 1.9 bar using the shock tube method. The gas mixtures containing 10 to 25% NO in Ar were shock heated and the time-dependent NO concentrations were monitored by using a tunable IR-diode laser. The measured NO concentration profiles in the post-shock reaction zone were interpreted by means of computer simulations. With a reaction mechanism developed by Thielen and Roth (1984) nearly complete agreement between calculated and measured NO concentration profiles was obtained.