共查询到19条相似文献,搜索用时 187 毫秒
1.
2.
3.
4.
提出了一种液氧煤油发动机尾焰红外辐射特性计算方法,首先采用计算流体力学软件对液氧煤油发动机内流场进行计算,然后以获得喷管喉部截面参数作为入口边界条件计算发动机尾焰流场,最后以发动机尾焰流场参数分布为基础,采用有限体积法对发动机尾焰红外光谱辐射特性和成像特性进行计算,并对比验证了模型和方法的准确性。在此基础上,研究了化学反应机理和复燃反应过程对尾焰红外辐射特性影响。结果表明,采用多步化学反应能够准确模拟液氧煤油发动机内流场,温度相比热力学计算大3.34%,压力相比试车测量大2.89%;考虑复燃反应使尾焰红外辐射强度增强显著,在采用单步化学反应和多步化学反应两种工况下2~5波段红外辐射强度分别增大50%~100%和150%~170%,但不会影响尾焰红外光谱辐射特性和红外总辐射强度随探测角变化趋势;采用单步化学反应和多步化学反应都能够获得清晰结构的红外成像图像,但是前者2~5尾焰红外辐射强度要比后者增大90%~190%,且两种工况下发动机尾焰红外光谱辐射特性差别很大,尾焰红外总辐射强度随探测角变化趋势也不同。 相似文献
5.
复燃对液体火箭尾焰红外辐射特性的影响 总被引:2,自引:0,他引:2
为了定量研究复燃对液体火箭尾焰红外辐射特性的影响,建立了一个可以计算液体火箭尾焰复燃流场和红外辐射特性的模型.首先,使用FLUENT软件计算液体火箭尾焰复燃流场,其中尾焰中的复燃反应使用有限速率化学反应模型计算;然后,使用基于HITEMP数据库的窄带模型计算尾焰内气体的辐射参量;最后,使用有限体积法求解尾焰中的辐射传输方程.通过比较该模型计算的Titan ⅢB尾焰光谱辐射强度与(美国)国家航空航天局公布结果的一致性,证明了该模型的正确性.最后,利用该模型计算了复燃对某液体火箭尾焰光谱和波段红外辐射强度的影响,结果表明,复燃反应可以显著增加尾焰红外光谱辐射强度,在2.5~3.0 μm和4.2~4.7 μm两个主要辐射波段平均辐射强度的增加比例分别达到了30.8%和28.3%,所以,在计算液体火箭尾焰准确的红外辐射特性时,需要考虑复燃的影响. 相似文献
6.
为了定量研究复燃对液体火箭尾焰红外辐射特性的影响,建立了一个可以计算液体火箭尾焰复燃流场和红外辐射特性的模型.首先,使用FLUENT软件计算液体火箭尾焰复燃流场,其中尾焰中的复燃反应使用有限速率化学反应模型计算;然后,使用基于HITEMP数据库的窄带模型计算尾焰内气体的辐射参量;最后,使用有限体积法求解尾焰中的辐射传输方程.通过比较该模型计算的Titan IIIB尾焰光谱辐射强度与(美国)国家航空航天局公布结果的一致性,证明了该模型的正确性.最后,利用该模型计算了复燃对某液体火箭尾焰光谱和波段红外辐射强度的影响,结果表明,复燃反应可以显著增加尾焰红外光谱辐射强度,在2.5~3.0 μm和4.2~4.7 μm两个主要辐射波段平均辐射强度的增加比例分别达到了30.8%和28.3%,所以,在计算液体火箭尾焰准确的红外辐射特性时,需要考虑复燃的影响. 相似文献
7.
首先介绍固体发动机尾焰中钾原子的来源及其在尾焰中的辐射机理,并基于原子谱线理论对尾焰钾共振双线的光谱线型特征进行分析。然后,采用理想模型及半经验公式法对尾焰流场分布进行数值模拟,通过尾焰的流场参数使用C-G近似法数值计算尾焰钾共振双线的辐射特性。最后,利用大气辐射传输模型计算尾焰中钾共振双线辐射信号经过大气传输后到达探测系统的光谱特征。结果表明,该方法能有效地仿真计算尾焰近红外钾线高光谱精细结构。仿真结果亦表明钾共振双线光谱信号能有效通过大气传输,可作为尾焰探测识别的依据。 相似文献
8.
隐身飞机尾焰的红外辐射是隐身飞机探测的主要辐射源.本文提出了一种新的隐身飞机尾焰红外辐射特性计算模型.该模型以普通飞机尾焰红外辐射特性计算模型为基础,进而考虑红外隐身措施的影响,间接实现隐身飞机尾焰的红外辐射特性的计算.计算模型分别考虑了隐身飞机的二元喷口、引射技术、红外遮蔽云以及遮挡对尾焰辐射的影响.计算结果得出,添加隐身措施后尾焰辐射强度仅为添加前辐射强度的5.8%.针对隐身飞机尾焰红外辐射特性很难获取的问题,将计算结果与喷灯燃烧航空煤油的光谱峰位数据进行了比较,实验结果显示隐身前后辐射能量量级变化与国外文献相同,表明该模型可以用于隐身飞机尾焰红外辐射特性计算. 相似文献
9.
10.
11.
L.H. Liu H.P. TanB.X. Li 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,73(6):641-648
An iteration method is extended to analyze the influences of the turbulent fluctuation on the reconstruction of Reynolds time-averaged temperature in turbulent axisymmetric free flames when the temperature profiles are retrieved by the low time-resolution data of outgoing emission and transmission radiation intensities. A simplified probability density function is used to simulate the turbulent fluctuation of temperature and absorption coefficient. The effects of turbulent fluctuating intensities on the estimation of the Reynolds time-averaged temperature and absorption coefficient are examined. The results show that the effects of turbulent fluctuation on the reconstruction of time-averaged absorption coefficient are not significant. In the case of weak turbulent fluctuation, the influences of turbulent fluctuation on the estimation of time-averaged temperature profiles are small. But in the case of strong turbulent fluctuation, the influences of turbulent fluctuation on the estimation of time-averaged temperature profiles are significant. 相似文献
12.
An iteration method is extended to reconstruct the time-averaged temperature distribution in turbulent axisymmetric sooting free flame by the multi-wavelength measured data of low time-resolution outgoing emission and transmission radiation intensities. A Gaussian probability density function is used to simulate the turbulent fluctuation of temperature. The reconstruction of time-averaged temperature profile consists of three steps. First, the time-averaged spectral absorption coefficient is retrieved from the time-averaged transmissivity data by iteration method. Then the time-averaged blackbody spectral radiation intensity is estimated from the low time-resolution outgoing spectral emission radiation intensities. Finally, the time-averaged temperature and its standard deviation are approximately reconstructed from the multi-wavelength time-averaged spectral emission radiation data by the least-square method. Both exact and noisy input data have been used to test the performance of the proposed inversion method. The results show that the time-averaged temperature profiles can be estimated with good accuracy by the presented inversion method, even with noisy input data, and the standard deviation of temperature is more sensitive to the measurement errors. In the case of large temperature fluctuation, the errors of estimation for time-averaged temperature profile are large if the turbulent fluctuation is not taken into account. 相似文献
13.
Reconstruction of time-averaged temperature of non-axisymmetric turbulent unconfined sooting flame by inverse radiation analysis 总被引:1,自引:0,他引:1
A multi-wavelength inversion method is extended to reconstruct the time-averaged temperature distribution in non-axisymmetric turbulent unconfined sooting flame by the multi-wavelength measured data of low time-resolution outgoing emission and transmission radiation intensities. Gaussian, β and uniform distribution probability density functions (PDF) are used to simulate the turbulent fluctuation of temperature, respectively. The reconstruction of time-averaged temperature consists of three steps. First, the time-averaged spectral absorption coefficient is retrieved from the time-averaged transmissivity data by an algebraic reconstruction technique. Then, the time-averaged blackbody spectral radiation intensity is estimated from the outgoing spectral emission radiation intensities. Finally, the time-averaged temperature is approximately reconstructed from the multi-wavelength time-averaged spectral emission radiation data by the least-squares method. Noisy input data have been used to test the performance of the proposed inversion method. The results show that the time-averaged temperature distribution can be estimated with good accuracy, even with noisy input data. The accuracy of the estimation decreases with the increase of turbulent fluctuation intensity of temperature and the effects of assumed PDF on the reconstruction of temperature are small. 相似文献
14.
The Monte Carlo ray-tracing method (MCRT) based on the concept of radiation distribution factor is extended to solve radiative heat transfer problem in turbulent fluctuating media under the optically thin fluctuation approximation. A one-dimensional non-scattering turbulent fluctuating media is considered, in which the mean temperature and absorption coefficient distribution are assumed and the shape of probability density function is given. The distribution of the time-averaged volume radiation heat source is solved by MCRT and direct integration method. It is shown that the results of MCRT based on the concept of radiation distribution factor agree with these of integration solution very well, but results of MCRT based on the concept of radiative transfer coefficient do not agree with these of integration solution. The solution of time-averaged radiative transfer equation by the concept of radiative transfer coefficient should be treated with caution. 相似文献
15.
16.
An experimental study has been conducted to investigate the combined influence of length scale of free-stream turbulence, A, and cylinder diameter, D, on heal transfer from slightly heated circular cylinders in cross flow. By using a hot-wire anemometer, spectrum analysis of its signal with a Fourier analyzer is employed to investigate the separated shear layer formed behind the circular cylinder. A resistance thermometer is used to measure the time-averaged temperature behind the cylinder and the power-spectral density of the temperature fluctuation in the thermal boundary layer. It is found that (I) the Nusselt number at the rear stagnation point varies with the relative scale A / D, at the same Reynolds number, (2) the laminar-to-turbulence transition region in the separated shear layer moves in the streamwise direction with the change in the length-scale ratio, and (3) a streamwise shift of the transition region in the separated shear layer causes a substantial increase in the power spectrum of the temperature fluctuation. A correlation equation with A/ Das a parameter is derived to predict the heat transfer rate at the rear stagnation point. 相似文献
17.
本文对几种二阶矩湍流反应模型,包括统一二阶矩模型、只考虑温度脉动的二阶矩模型、只考虑浓度脉动关联的二阶矩模型、及同时考虑温度脉动和浓度脉动关联的二阶矩模型,进行了比较。将上述模型加入到FLUENT6.0软件平台上,模拟了不同旋流数下甲烷-空气的旋流燃烧。模拟结果和实验结果进行了比较,探讨了各关联量大小及其对时平均反应率的影响。结果表明,统一二阶矩湍流反应模型具有最好的模拟效果。其原因是,各种关联矩中,化学反应率系数与浓度间的脉动关联最重要。 相似文献
18.
LIU Nansheng LU Xiyun & ZHUANG Lixian Department of Mechanics Mechanical Engineering University of Science Technology of China Hefei China 《中国科学G辑(英文版)》2005,48(2)
Turbulent flow in an axially rotating pipe, involving complicated physical mecha- nism of turbulence, is a typical problem for the study of rotating turbulent flow. The pipe rotation induces two effects on the flow. One is the stabilizing effect due to the centrifu- gal and Coriolis forces, which accounts for the relaminarization of the turbulence[1—3] and the reduction of the friction coefficient at the pipe wall. The behavior is also related to the wall streaks inclining to the azimuthal di… 相似文献
19.
被动式遥感FTIR测量时的仪器响应函数校正 总被引:5,自引:3,他引:2
在应用红外发射光谱来获得某些红外源的绝对光谱能量数据,如辐射源光谱辐射通量密度、辐射源光谱辐射强度、辐射源光谱辐射亮度及光谱辐射照度等时,需要得知不同条件下的仪器响应函数。文章对被动式遥感FTIR测量时的仪器响应函数进行了校正,实验结果表明:在不同的实验条件下,仪器响应函数的变化规律是不同的,它不仅和校正时所采用的绝对黑体温度有关,而且和校正中仪器接收到的信号大小有直接关系。因此,在被动式测量时,要密切注意发射源温度以及发射源发射信号大小,以便获得最佳仪器响应函数校正结果。 相似文献