【作者】 楚化强；

【导师】 周怀春； Fengshan Liu；

【作者基本信息】 华中科技大学 ， 热能工程， 2012， 博士

【摘要】 辐射换热常常是燃烧系统和各类火焰中主要的换热方式,因此引起了广泛的注意。热辐射为揭示各类状态提供了多种方式,如辐射检测信号等。然而,由于辐射强度一方面依赖于空间和角度影响,另一方面如H2O、CO2等气体的吸收系数随波数剧烈变化,这导致很难准确模拟辐射换热问题。自19世纪50年代,辐射模型的研究已经引起了各国学者的注意。最近20年,发展了各类精确、有效的气体非灰模型,但目前还有待提高模型对气体混合物、气固混合物的处理能力。所以,本文旨在进一步发展已有模型,提高计算精度和效率,并将其应用于燃烧模拟中。具体工作如下：本文首先基于统计窄谱带模型和统计窄谱带关联K模型,研究了水蒸气、二氧化碳和烟黑的辐射热源分布和光谱强度变化情况,同时考察烟黑颗粒对气体壁面热流的影响,得到了气体的平均普朗克吸收系数。基于各个版本的气体谱线数据库,采用逐线法考察了一维平行平板间气体辐射换热情况。针对不同介质浓度和温度分布,考察各个数据库的性能。同时,也采用了统计窄谱带模型,通过逐线法结果来检验统计窄谱带模型谱带参数的准确性。研究显示,光谱数据库的选择对逐线法精度的影响很大。研究还显示,不论是辐射热源还是壁面热流,统计窄谱带模型计算结果都与基于HITEMP2010数据库的逐线法结果吻合的非常好。将逐线法和统计窄谱带关联K模型结合离散坐标法应用到二维含有边界的气体介质的辐射传递过程求解。发展了二维矩形区域基准解,并为多维系统中统计窄谱带关联K模型的可用性提供依据。基于最新光谱数据库,首次得到了水蒸气和二氧化碳的吸收线黑体分布数据库。利用该数据库,将本征正交分解(POD)法应用到气体辐射参数求取中,另外还提出了一个全新的双曲线关联式(HC)。基于此,发展POD-SLW模型。发展逐线法求取窄谱带透射率,进一步检验统计窄谱带模型的准确度；发展逐线法和统计窄谱带模型关于普朗克平均吸收系数新公式,纠正以往文献中的错误解,并将其应用到二维轴对称扩散火焰模拟中,考察辐射在不同重力加速度下对火焰结构、烟黑形成的影响。综上所述,本文发展的统计窄谱带模型、逐线法,为高温气体辐射特性计算及辐射传递的数值模拟提供了一种灵活、有效的方法。更多还原

【Abstract】 The importance of thermal radiation heat transfer in combustion systems and flames has been paid unprecedented attention due to its often dominant role in heat transfer. Thermal radiation also offers various ways to reveal the state of combustion through inverse analysis from the detected radiation signals. Ultrafast pulse radiation is rapidly being deployed in many new applications. However, accurately modeling of thermal radiation is a formidable task due to the spatial and direction dependence of radiation intensity and extremely rapid variation of the absorption coefficient of gaseous species such as CO2 and H2O. Thermal radiation modeling has received attention in the 1950’s. The last 20 years have witnessed rapid progress in the development of accurate and efficient modern non-grey gas radiation models. More research is required to improve the current modeling methods in terms of gas mixture treatment and non-grey particle scattering treatment. Therefore, this article will concentrate on further improve the current non-grey radiation models in terms of accuracy, or efficiency, or both. Specifically as follows:Firstly, the statistical narrow-band (SNB) model and SNB correlated-K method were employed to study the effect of soot volume fraction up to 1 ppm on the source term, the narrow-band radiation intensities along a line-of-sight, and the net wall heat fluxes were investigated for a wide range of temperature. In addition, the Planck-mean absorption coefficients were obtained using these models.Line-by-line calculations using the high-resolution spectral databases were conducted for six test cases of radiative heat transfer in one-dimensional enclosure between two parallel plates. This study demonstrates the importance of spectral database to the accuracy of line-by-line calculations through a systematic comparison of line-by-line results from different databases. The agreement between the LBL results using the HITEMP2010 database and the results of the SNB model was found to be very good for both the wall heat flux and the radiative source term.Radiation heat transfer in two-dimensional rectangular enclosures containing CO2/H2O/N2 mixtures was calculated using the line-by-line and the statistical narrow-band correlated-k models. The present line-by-line results can serve as benchmark results for the purpose of validating other approximate models. The SNBCK results were found in good agreement with those of the LBL model. Therefore, it can provide benchmark solution in the absence of LBL results in multi-dimensional gas radiation heat transfer problems.Databases of the absorption line blackbody distribution function (ALBDF) of CO2 and H2O were firstly generated over a wide range of gas and blackbody temperature and the full range of gas concentration from line-by-line (LBL) calculations using the latest version of HITEMP. Proper orthogonal decomposition (POD) and the new hyperbolic correlations (HC) were developed and used for rapid calculation the ALBDF value at an arbitrary combination of gas and blackbody temperatures and gas concentration. Then, the POD-SLW model was proposed.Narrow-band transmissivities in the spectral range were calculated using the statistical narrow-band model and the line-by-line method along with the HITEMP high-resolution spectral database. New Planck-mean absorption coefficients formats were developed based on these two methods. Planck-mean absorption coefficients obtained using LBL method were applied to the two-dimension diffustion flame.The effect of radiation at different gravity on flame structure and soot formation in coflow CH4/air diffusion flames were investigated.In summary, the LBL and SNB models are flexible and valid computation methods for high temperature gas radiative properties and radiative transfer simulation.更多还原