共查询到19条相似文献,搜索用时 78 毫秒
1.
2.
建立了三种不同宽高比矩形喷管的物理模型,采用Fluent6.3软件对三种矩形尾喷管外的三维流场进行了数值模拟,得到尾焰流场的温度、压强和密度等数据,并根据矩形尾喷管外尾焰的特点确立三种矩形尾喷管外尾焰的红外辐射核心计算区域.利用基于洛伦兹线型的统计窄带模型,求出尾焰在窄带l的平均吸收系数;然后采用有限体积法(FVM)求解气体介质中辐射传输方程,最后得到了尾焰的红外辐射的光谱特性与三种矩形喷管尾焰在3~5 μm波段的总强度分布.结果表明:尾焰辐射在2.7 μm和4.3 μm处出现两个辐射峰,并且随着矩形喷管宽高比的增加,尾焰的红外辐射强度大大降低. 相似文献
3.
卫星轨控推进器尾焰红外辐射的数值模拟 总被引:1,自引:1,他引:0
为全面了解卫星的红外辐射特性,需掌握卫星轨控推进器尾焰的红外辐射特性.按照先计算尾焰的流场、再计算尾焰的吸收系数、最后用有限体积法求解尾焰红外辐射亮度的先后顺序,较完整地建立了卫星轨控推进器尾焰红外辐射的求解模型.根据该模型计算得到的尾焰辐射亮度,进一步求解获得了1 000~4 500 cm-1 内的光谱和波段辐射强度.通过分析,光谱辐射强度在1 525 cm-1、1 700 cm-1、2 155 cm-1、2 175 cm-1、2 350 cm-1 和3 750 cm-1附近的数值较大;到喷管出口截面的垂直距离不同,最大的波段辐射强度可能对应不同的方位角.在波数2 350cm-1和3 750 cm-1 附近,光谱辐射强度与同类文献中的计算结果能够相互吻合.此结果表明,该模型具有较高的可行性和精确性. 相似文献
4.
5.
随着无人机技术在各个领域崭露头角,无人机目标在红外波段的辐射特性成为人们非常关注的问题。本文首先对中、长波红外探测器进行辐射定标,针对飞行中的无人机目标的辐射特性进行测量,对飞行状态下的无人机目标的温度进行了反演,分别采用了单波段、双波段比色法、基于黑体校正的双波段法进行探测,结合实测数据对上述各种方法进行了分析对比,对测量结果进行了精度分析并给出误差源。结果表明,实验中的无人机中波辐射强度约为0.04 W/sr、长波辐射强度在0.5 W/sr左右,采用基于黑体校正的双波段测量方法能极大提高无人机目标温度反演的精度。反演温度的绝对误差降低至2 K,相对误差仅为0.5%左右。 相似文献
6.
结合某吊舱加装红外热像仪的使用,基于红外热像仪测试目标辐射亮度、辐射强度的功能,提出了在目标红外辐射特性测试中扣除整流罩影响的方法 ,并在实验室利用黑体、整流罩、长波红外热像仪,测试了整流罩的波段透过率,给出了某吊舱扣除整流罩影响的修正公式,并在型号测试中应用,取得了良好的效果。 相似文献
7.
8.
9.
在理论分析的基础上,构造了基于λ水平能量聚点的目标辐射噪声线谱的特征量模型.在利用中值痣波去除信号功率谱中“平台型”的λ水平能量聚点后,计算其λ水平能量聚点作为拟线谱频率,通过拟线谱频率对应周期的整周期延时叠加突出线谱特征,以提高辐射噪声线谱的检测率.理论分析和对仿真信号的计算结果表明,该算法是有效的. 相似文献
10.
基于OpenFlight模型的通用桥梁红外辐射特性模拟方法 总被引:1,自引:0,他引:1
对桥梁结构进行分析及简化,提出了基于OpenFlight模型的通用桥梁建模方法,将梁式桥、斜拉索桥、拱桥和悬索桥统一为一种通用的模型结构,并分别针对桥梁箱体结构、主缆、索塔、护栏等典型部件的热特性,综合考虑各种自然因素,建立桥梁红外辐射特性计算理论模型,并以图像的灰度信息模拟红外辐射特性,开发了通用的桥梁红外辐射特性计算及成像仿真软件系统,实现了任意时刻、任意地理位置、任意气象条件下不同类型桥梁的红外辐射特性模拟。实验结果表明提出方法与现有桥梁红外成像仿真结果具有一致性,符合典型桥梁的红外热辐射规律。 相似文献
11.
T. Morrow H. F. Sakeek A. El Astal W. G. Graham D. G. Walmsley 《Journal of Superconductivity》1994,7(5):823-828
The plasma produced during laser ablation deposition of thin film YBCO has been studied by optical emission spectroscopy. There is evidence of increased YO band emission in the range 590–625 nm as the ambient oxygen gas pressure confining the plume is increased in the range 30–200 m Torr. Temporal profiles show that close to the target the plume is insensitive to ambient oxygen pressure. It is deduced that the optical emission here is excited by electron impact excitation. Further away from the target there is evidence that two distinct processes are at work. One is again electron excitation; the emission from this process decreases with distance because the expanding plume cools and collisions become less frequent in the expanding gas. The second is driven by oxidation of atomic species expelled at high speeds from the target. The main region of this activity is in the plume sheath where a shock front ensures heating of ambient O2 and reaction of monatomic plasma species to form oxide in an exothermic reaction. Spatial mapping of the emission demonstrates clearly how increasing oxygen gas pressure confines the plasma and enhances the emission intensity from the molecular YO species ejected from the target in a smaller region close to the target. Ba+ is observed as a dominant species only very close to (within 1 mm of) the target. Absorption spectra have been taken in an attempt to examine ground state and cool species in the plume. They reveal the quite surprising result that YO persists in the chamber for periods up to 1 msec. This suggests an explanation for the recent report of off-axis laser deposition in terms of simple condensation. Previously, quasi-ballistic transfer of material from target to substrate has been considered the only significant process. 相似文献
12.
The principles of constructing a simulation model for an electromagnetic flowmeter are considered by means of which it is
possible to carry out research into the metrological characteristics of instruments.
__________
Translated from Izmeritel’naya Tekhnika, No. 5, pp. 38–43, May, 2006. 相似文献
13.
分别采用标准κ-ε模型、重整化群(RNG)κ-ε模型和可实现的(Realizable)κ-ε模型对某喷嘴型真空高压气淬淬火过程进行了数值模拟.结果表明:通过合理选择湍流模型,可以通过数值模拟的方式实现对淬火过程的预测和分析.由于三种湍流模型对湍流耗散率处理方式的不同,使其适用领域有所不同,对于真空气淬过程,可实现的( Realizable)κ-ε模型适用性最好,重整化群(RNG)κ-ε模型次之,标准κ-ε模型与实验吻合度最差. 相似文献
14.
Large eddy simulation of fire-induced buoyancy driven plume dispersion in an urban street canyon under perpendicular wind flow 总被引:1,自引:0,他引:1
The dispersion of fire-induced buoyancy driven plume in and above an idealized street canyon of 18 m (width) × 18 m (height) × 40 m (length) with a wind flow perpendicular to its axis was investigated by Fire Dynamics Simulator (FDS), Large Eddy Simulation (LES). Former studies, such as that by Oka [T.R. Oke, Street design and urban canopy layer climate, Energy Build. 11 (1988) 103–113], Gayev and Savory [Y.A. Gayev, E. Savory, Influence of street obstructions on flow processes within street canyons. J. Wind Eng. Ind. Aerodyn. 82 (1999) 89–103], Xie et al. [S. Xie, Y. Zhang, L. Qi, X. Tang, Spatial distribution of traffic-related pollutant concentrations in street canyons. Atmos. Environ. 37 (2003) 3213–3224], Baker et al. [J. Baker, H. L. Walker, X. M. Cai, A study of the dispersion and transport of reactive pollutants in and above street canyons—a large eddy simulation, Atmos. Environ. 38 (2004) 6883–6892] and Baik et al. [J.-J. Baik, Y.-S. Kang, J.-J. Kim, Modeling reactive pollutant dispersion in an urban street canyon, Atmos. Environ. 41 (2007) 934–949], focus on the flow pattern and pollutant dispersion in the street canyon with no buoyancy effect. Results showed that with the increase of the wind flow velocity, the dispersion pattern of a buoyant plume fell into four regimes. When the wind flow velocity increased up to a certain critical level, the buoyancy driven upward rising plume was re-entrained back into the street canyon. This is a dangerous situation as the harmful fire smoke will accumulate to pollute the environment and thus threaten the safety of the people in the street canyon. This critical re-entrainment wind velocity, as an important parameter to be concerned, was further revealed to increase asymptotically with the heat/buoyancy release rate of the fire. 相似文献
15.
16.
对瞬态变化的高温气流温场温度的准确测量一直是工程测量中的难点,超声波测温技术作为一种新型的非接触式测温方法,其测温原理简单,响应速度快,便于工程安装,可用于多种特殊工况下温度的测量。但由于超声信号在传播过程中的衰减及温场外界条件的干扰问题,使得超声波测温技术还未有广泛应用,目前仍处于研究试验阶段。本文介绍了超声波测温技术的发展历史及测温原理,对超声波测温技术目前存在的问题进行了分析,对超声波测温技术的发展进行了展望。 相似文献
17.
置换通风系统中人体产生的对流气流量的简化模型 总被引:1,自引:0,他引:1
置换通风系统常用于会议室、教室和剧院等人员较密集的场合,这是由于其特殊的气流形式能给呼吸区提供较新鲜的冷空气。呼吸区的空气品质和热舒适性很大程度上受到室内热源驱动的上升气流的影响,而上述场合中的主要热源是人,在设计类似场合的置换通风系统时,研究人体产生的上升气流很有必要。在前人热羽流量模型的基础上,扩展出适用于人体热源的热羽流量模型,并将其与Mundt的研究结果进行了对比,指出该模型在一定条件下具有较好的正确性。 相似文献
18.