共查询到19条相似文献,搜索用时 328 毫秒
1.
2.
3.
引入水蒸气非平衡相变的动力学模型和水蒸气真实物性模型,建立了水蒸气跨声速非平衡流动的守恒型数值计算模型,采用Roe-FDS计算格式数值捕捉了水蒸气超声速流动中的非平衡相变与激波效应,在此基础上开展了气动激波与凝结激波的耦合计算,分析了气动激波波锋面与凝结激波波锋面相遇时,气动激波与非平衡相变之间的相互作用规律。研究显示,随着背压的不断升高,气动压缩激波不断向喷管喉口位置推移。当气动激波发生在凝结激波的下游位置时,气动激波的耗散效应使得喷管内的液相质量分数逐渐减小而不会对上游的非平衡相变和凝结激波产生影响。当气动激波随背压继续上行与气动激波交汇时,气动激波强烈的耗散效应使得凝结激波特征迅速减弱,非平衡相变逐渐退化到喷管边界区域,而气动激波由于受到凝结激波的强烈干扰,激波强度迅速减弱,显现出明显的斜弱激波特征.当气动激波上行至喷管喉口附近时,X型凝结激波逐渐消退,非平衡相变在喷管主流区消失。 相似文献
4.
5.
为了探寻直排型连续波DF/HF化学激光器的起动特性,建立了一套化学激光器气流通道单喷管小型模型实验装置,通过选用不同的气体(冷气流)作为工作介质和不同的扩压器进行实验,分别研究了工作介质的气动参量对模型起动特性和扩压器喉道最小面积的影响,并与1维定常流理论的计算结果作了比较。最后分析了基区对模型起动特性的影响,比较了两种类型基区的差异。实验结果表明:对于直排型连续波DF/HF化学激光器,采用大比热容比、小相对分子质量的介质作为引射气流,喷管出口和基区之间带有一个向内的圆角,对提高DDCL整体性能是有利的。 相似文献
6.
7.
针对低场核磁共振一维反演中无法分辨一维谱中重叠组分和目前报道的扩散-横向弛豫二维反演算法计算量大、计算耗时长的问题,提出了一种计算量小、计算效率高、耗时短的扩散-横向弛豫二维反演算法. 首先对扩散系数D-和横向弛豫时间T2进行布点;其次根据信号采集条件计算出两个核心矩阵,并分别进行奇异值分解;然后,由所采集信号计算出两个核心矩阵的奇异值截断值,分别对两个核心矩阵的奇异值矩阵进行截断并求其逆矩阵;最后计算出初始反演结果,并添加非负约束经过多次迭代得到最终反演结果. 实验结果证明,提出的扩散-横向弛豫二维反演算法在不影响反演结果准确性的基础上,能极大提高计算效率. 相似文献
8.
本文用微扰方法计算了电子分布函数,得到了康普顿型谐波自由电子激光器小信号增益及饱和增益的公式,最后对模型及结果进行了分析与讨论。 相似文献
9.
10.
11.
Several new results are derived upon gas density as well as upon velocity and force fields relative to a gasdynamic laser within a supersonic nozzle. Evolution equations, including the continuity equation, are employed to obtain the above results. In particular, the continuity equation is used to determine the shape of the nozzle so that its cross-sectional area is calculated as a function of distance. This function is one of the ingredients to get our results relative to gas density, velocity, and force. In addition, the time-dependent power associated with the vibrational non-equilibrium expansion in the nozzle of hot gas at high pressure is evaluated. 相似文献
12.
O. P. Nechesov 《Russian Physics Journal》1979,22(7):776-780
An economical and consistent, in mathematical respects, method of analyzing the flow of a relaxing gas or plasma in a supersonic nozzle is developed. The method is used in analyzing the vibrational relaxation of a two-phase mixture in the nozzle of a combustion gasdynamic laser. It is shown that the use of the Gear method in the numerical integration stage permits passage of the near-equilibrium sections with a large spacing, which substantially cuts down the computing time.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 99–104, July, 1979. 相似文献
13.
A comprehensive theoretical analysis of optimization of gain in CO2-N2 gasdynamic laser employing wedge or conical or hyperbolic nozzles with either H2O or He as the catalyst is presented. After a review of previous work, the usual governing equations for the steady inviscid
quasi-one-dimensional flow in a supersonic nozzle of a gasdynamic laser are used to obtain similar solutions for the various
flow quantities, which variables are subsequently used to optimize the small-signal gain on theP(20) line of the (001) → (100) transition of CO2 at wavelength 10.6μm. The corresponding optimum values like reservoir pressure and temperature and nozzle area ratio also have been predicted
and presented in the form of graphs. The analysis predicts that employing of 2D-wedge nozzle results in higher gain values and the CO2-N2-H2O gasdynamic laser employing 2D-wedge nozzle is operationally the best laser system for which the optimum value as high as 3.1 m−1 gain can be obtained. 相似文献
14.
马靖 《光谱学与光谱分析》2014,34(7):1865-1868
为实现对有机物混合物的快速、无损检测,提出一种基于激光拉曼光谱技术的二维分析方法。研究结果表明,采用532 nm波长激光作为激发光源,观测到236.2,348.9,449.4,513.6 cm-1四条振动拉曼谱线,且这些谱线的强度比为6.4∶1.7∶9.4∶1.0,可确定四氯乙烯的存在。观测到707.5,1 087.9,1 175.8, 3 078.6 cm-1四条振动拉曼谱线,其强度比为9.6∶6.4∶1.0∶3.9,可确定氯苯的存在。即通过综合分析特征谱线及若干特征谱线的强度比,可快速判断有机混合溶液中某种物质的存在。在定量分析方面,采用多光谱分析结合最小二乘法拟合提高了测量的可靠性,所测样品浓度的准确率为98.4%。本研究为有机物混合物成分识别和浓度探测提供了一套可行的光谱测量方法,有着十分重要的应用前景。 相似文献
15.
Cinthya Toro Nicolás D. Gómez Norberto G. Boggio Jorge Codnia M. Laura Azcárate Carlos Rinaldi 《Applied Physics A: Materials Science & Processing》2014,117(1):43-47
In this article, we present an experimental study of the effect of conical section nozzles coupled to solid targets on laser ablation propulsion. The impulse produced on the target by laser ablation was measured in terms of the coupling coefficient C m using a piezoelectric (PZT) sensor. The standard deviation of the PZT signal was used as an estimator of the transferred impulse. The ablation was performed with a TEA CO2 laser at room temperature and atmospheric pressure. The targets were pellets of 90/10 % w/w Zn/CaCO3 concentration ratio. Aluminum nozzles with conical section were coupled to these propellant pellets. A comparative study of the variation of C m using nozzles of different inlet and outlet diameters of the ejected material as well as of different heights was made. The results demonstrate that for the pellet composition analyzed, as the nozzle’s height increases and its diameter decreases improvements up to 250 % respect to the target without nozzle are obtained. These are promising results for the potential development of laser ablation microthrusters. 相似文献
16.
17.
An analytical method has been proposed to optimise the small-signaloptical gain of CO2-N2 gasdynamic lasers (gdl) employing two-dimensional (2D) wedge nozzles. Following our earlier work the equations governing the steady, inviscid, quasi-one-dimensional
flow in the wedge nozzle of thegdl are reduced to a universal form so that their solutions depend on a single unifying parameter. These equations are solved
numerically to obtain similar solutions for the various flow quantities, which variables are subsequently used to optimize
the small-signal-gain. The corresponding optimum values like reservoir pressure and temperature and 2D nozzle area ratio also
have been predicted and graphed for a wide range of laser gas compositions, with either H2O or He as the catalyst. A large number of graphs are presented which may be used to obtain the optimum values of small signal
gain for a wide range of laser compositions without further computations. 相似文献
18.
A theoretical analysis of a downstream-mixing 16-μm CO2 gasdynamic laser revealed the possibility of utilizing the downstream-mixing scheme for the generation of 9.4-μm radiation using a CO2 gasdynamic laser. The flow-field has been analyzed using complete two-dimensional, unsteady laminar form of Navier-Stokes
equations coupled with the finite rate vibrational kinetic equations. The analysis showed that integrated small-signal gain
of 11.5m−1 for Lorentzian broadening and 4.8m−1 considering Voigt function can be obtained for N2 reservoir temperature of 2000°K and velocity ratio 1:1 between the CO2 and N2 mixing streams. These results (presented in graphs) clearly highlight the large potential of downstream-mixing CO2 gasdynamic laser for 9.4-μm laser generation. 相似文献