共查询到18条相似文献,搜索用时 203 毫秒
1.
《低温与超导》2016,(12)
Laval喷管作为天然气超音速旋流分离器的核心部件,其几何结构对喷管制冷性能和分离器的分离效率有着决定性影响。文中利用FLUENT软件进行数值模拟,系统研究了Laval喷管渐缩段线型、渐扩段张角及旋流器位置对Laval喷管内压力分布和制冷性能的影响。结果表明:渐缩段线型对喷管制冷性能有较大影响,采用维托辛斯基曲线进行Laval喷管渐缩段的设计可以获得较好的制冷效果;渐扩段张角越大,温降趋势越明显,喷管出口所能获得的温度越低,制冷效果也越好,但随着渐扩段张角的增大,在喷管存在背压的情况下易造成激波前移,破坏喷管内的低温环境;Laval喷管(加旋流器)的旋流分离能力和制冷性能存在着明显的制约关系,需要在二者之间寻找一个平衡点,使得Laval喷管(加旋流器)可以取得较好的旋流效应和膨胀制冷效果。 相似文献
2.
《低温与超导》2016,(6)
明确激波在Laval喷管内的发生位置,能够为设计及优化Laval喷管线型提供理论依据,从而提高Laval喷管的制冷性能和整个天然气超音速分离器的分离效率。文中对Laval喷管进行了结构设计,对不同背压条件下Laval喷管内激波位置进行了理论分析与计算,并利用FLUENT软件进行了数值模拟,通过研究不同背压条件下Laval喷管内气体马赫数、压力和温度分布,对喷管制冷性能进行了对比分析。结果表明:保持Laval喷管入口压力不变,随出口背压增大,激波位置逐渐从喷管出口向喷管入口方向移动,气体受到激波的影响,在喷管所能达到的最大马赫数不断降低,所能产生的最低温度不断上升,喷管的制冷性能越差;理论计算与数值模拟结果基本一致,数值模拟验证了理论计算的正确性。 相似文献
3.
4.
5.
6.
7.
针对抛物形喷管与圆柱形喷管相组合的带延长圆柱形喷管激光推力器模型,通过求解含激光能量源项的流体力学方程组,计算得到了不同单脉冲激光能量条件下3种构形参数对冲量耦合系数和推力的影响。结果显示带延长圆柱形喷管可获得高于600N/MW的冲量耦合系数,同时表明冲量耦合系数随圆柱喷管长度的增加而增大并趋于饱和,圆柱喷管饱和长度与激光能量呈线性关系。冲量耦合系数随抛物形喷管张角的增大先增大后减小,对于总长度为100mm的喷管,半张角在33°左右时取得最大值且受激光能量的影响很小。冲量耦合系数随点火位置的增大也存在最大值,最大值对应的点火位置与激光能量成线性关系。 相似文献
8.
9.
T形管中非共沸工质的组分分布对组分可调热力循环性能有重要影响。但目前的研究均是基于理想分离假设分析T形管对热力循环的影响。为研究T形管实际分离性能对热力循环性能的影响,设计了一种基于T形管的新型自复叠制冷系统。对制冷工况下T形管中R134a/R600a的组分分布进行数值模拟,基于数值模拟结果对新型自复叠制冷系统性能进行计算分析。结果表明:T形管出口的流量分配比越高,其分离效率越大。当干度大于0.8或R134a质量分数大于0.7时,T形管两个出口的分离效率相对较小。与无分离的制冷系统相比,基于T形管的自复叠制冷系统的COP可提升0.83%至18.69%,单位容积制冷量可提高3.09%至36.2%,过冷器热负荷可降低11.6%至31.3%。 相似文献
10.
介绍一种跟踪式圆台聚光装置, 利用跟踪系统, 沿着东西、 南北两个方向, 对太阳光线进行双向实时跟
踪, 使太阳光线垂直或近垂直照入大圆台大口部. 经反射, 以垂直或近垂直方式投射到受光框架4个侧面和底面上,
将受光器照射; 受光器可以是太阳能高温集热管, 或平板集热器、 或太阳能电池板; 聚光系统与受光系统以模块形式
进行组合或分离. 本装置聚能功效高、 稳固性强、 应用范围广, 可为太阳能集热、 光伏发电提供高效低廉的聚能装置 相似文献
11.
A method is described to evaluate the radiation impedance spectra of a duct-nozzle system with and without mean flow by using measured reflection coefficient data. In this method the impedance at the junction of the duct and nozzle is first evaluated by using complex reflection coefficient data measured experimentally with an impulse technique. This impedance is then transferred to the nozzle exit by using a solution of the wave equation appropriate for the duct-nozzle system. The application of this method is described and results are presented to show the effect of nozzle geometry and the effect of mean flow on the radiation impedance of the duct-nozzle system. The results derived by using this method are compared with the similar results derived by using some approximate methods. 相似文献
12.
利用脉冲Nd:YAG激光作用在铝、铜靶上,研究了不同入射激光能量下冲量耦合系数和离焦量之间的关系,以及不同功率密度情况下冲量耦合系数和光斑直径的关系。实验表明铝靶在入射激光脉冲能量由75.8 mJ增加到382.3 mJ时,冲量耦合系数峰值对应的最佳离焦量由-10 mm处远离焦点向透镜方向移到-18 mm,而对应的激光功率密度仅由2.0×109 W/cm2增加到3.9×109 W/cm2;铜靶实验规律和铝靶类似。等离子体屏蔽的吸收作用导致了冲量耦合系数达到最大值后迅速降低。铝靶在入射激光功率密度由0.7×109 W/cm2增大到1.0×1010W/cm2时,冲量耦合系数随光斑直径增大而增大,对应变化斜率由5.2×10-5N·s/(mm·J)增大到49.2×10-5N·s/(mm·J),表明了稀疏波对冲量耦合系数的削弱作用随入射激光功率密度增加而增加,随光斑直径增大而减小。 相似文献
13.
利用透镜聚焦,抛物面喷管约束,结合复摆和光指针测量系统研究了单脉冲能量对吸气式激光推进冲量耦合系数的影响,实验中通过调节激光器工作电压和硅片衰减实现了脉冲能量5~70 J范围的有效拓展;进一步采用纳秒分幅高速相机拍摄了24 J能量下的流场纹影照片。结果表明:在4~9 J低能量和32~70 J较高能量区间,冲量耦合系数均较稳定;9~32 J能量下冲量耦合系数呈线性增长趋势,变化范围(6.5~21.0)×10-5 N·s·J-1;纹影照片显示流场演化经历了激光支持爆轰波、爆燃波和激波3个阶段,耦合系数的变化规律源于不同单脉冲能量对应不同的能量沉积效率。 相似文献
14.
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.
《中国光学快报(英文版)》2018,(12)
Impact and torsion pendulums are applied in impulse coupling experiments of high-energy laser irradiation of space debris. It is difficult to achieve a multi-pulse experiment and thus hard to analyze the multi-pulse impulse coupling effect. Here, we designed a new recoil impulse experimental measurement system of non-contact, multidegrees of freedom, and multi-pulse irradiation. The system used a low-pressure and low-temperature vacuum chamber to simulate the space environment, the pinning effect of magnetic levitation to achieve aluminum target suspension, and high-speed cameras to record the displacement over time to calculate the impulse of the target.Then the impulse coupling experiment of multi-pulse laser irradiation on the aluminum target was performed.The result shows that the multi-pulse impulse coupling effect is not the linear accumulation of coupling results by every single-pulse and multi-pulse coefficient that decreases with the increase of the number of pulses, and eventually stabilizes as the decrease gets smaller. 相似文献
17.
Hua Tan Fengying Zhang Rujun WenJing Chen Weidong Huang 《Optics and Lasers in Engineering》2012,50(3):391-398
A photographic system for the powder feed process of laser solid forming (LSF) was developed using a high speed camera, and the powder feed behaviors (the particle speed and the powder flow concentration) were described based on the powder flow images. The influences of the powder feed parameters and the distance below the nozzle exit plane on the powder feed behaviors were discussed, and the influences of the powder feed behaviors on the deposited layer quality were also investigated. It can be seen that the smooth finish of the deposited layer surface was improved remarkably by increasing the particle speed, and the deposited layer height decreases with the increase of the particle speed. It can also be found that the variation of the deposited layer height with the increase of the distance between the deposited surface and the nozzle exit plane is similar to that of the powder mass concentrations on the vertical symmetry axis. 相似文献
18.
为了验证理论分析得到的圆锥形喷管在单脉冲条件下的激光推进能量相似律,用2维轴对称辐射流体动力学方法,计算得到了不同构形的推进性能参数,分析了锥角、长度、无量纲因子、入射激光能量对冲量、冲量耦合系数的影响。计算揭示的激光推进能量相似律合理,在理论模型可以描述的范围内,其定性规律与理论分析、实验结果之间相互印证。结果表明:当锥角固定时,冲量和冲量耦合系数随无量纲因子先增大后减小,极大值对应的无量纲因子仅与气体比热比相关;当无量纲因子固定时,冲量随入射激光能量增加而增大,冲量耦合系数受激光能量的影响很小,冲量和冲量耦合系数均随锥角增大而单调减小。 相似文献