喷动流化床射流穿透深度试验研究

提出射流穿透深度是表征喷动流化床煤气化过程中射流特性的重要参数.在300 mm×30mm×2 000 mm的喷动流化床煤气化炉冷态试验装置上,采用压力信号分析和快速摄像图像分析相结合的方法,系统地考察了喷动气速、喷口直径、物料特性、静止床高和流化气流率对射流穿透深度的影响.结果表明,射流穿透深度随喷动气速、喷口直径的增大而增大,随静止床高、物料密度、物料直径、流化气流率的增大而减小.另外,引入两相弗劳德数(Fr)、颗粒雷诺数(Rep)等无量纲参数,对试验结果进行多元回归分析,建立了喷动流化床射流穿透深度的关联式,该关联式全面考虑了各种影响因素,特别是静止床高和流化气流率的影响.关联式的预测值与本文及国内外其他一些研究者的试验值进行了比较,结果吻合得较好.     

管道喷射吸附法净化垃圾焚烧尾气试验研究

在流化床试验装置上进行垃圾焚烧,焚烧尾气采用管道喷射吸附工艺净化.在活性炭加料量为1.6 g/m3时,脱硫率为83%,脱硝率为88%,脱氯率为27%.试验可得:活性碳、高岭土和活性矾土3种吸附剂对垃圾焚烧烟气中酸性气体的净化效果活性炭效果最好,高岭土效果最差;随着吸附剂加料量的增加,重金属的脱除率增加,且增幅逐渐趋缓.3种吸附剂对重金属的吸附能力比较表明:对Cd,Pb,Cu的吸附效果活性炭最好,高岭土次之,活性矾土最差;而对于Hg活性矾土的吸附效果最好;活性矾土对Cd也有较好的脱除效果.垃圾焚烧飞灰中多环芳烃主要以3环、4环和5环的形式存在,其他各环多环芳烃的数量较少;烟气中主要是3环和4环多环芳烃,未检测到6环多环芳烃,2环和5环多环芳烃的质量浓度相对较低;在喷入量相同的条件下,高岭土去除多环芳烃的效率最高,活性炭次之,活性矾土最低.总体而言,活性炭具有较好的综合吸附性能.     

25°Ahmed模型射流主动控制气动减阻策略

采用剪切应力输送(SST)κ-ω(湍动能-比耗散率)湍流模型对标准25°Ahmed模型进行基于计算流体力学(CFD)数值模拟的稳态射流减阻研究.在模型尾部设置射流孔,分别探究各位置处射流孔的孔径、到边线的距离、形状、射流速度和角度的最佳值,分析不同射流状态对流场结构、总阻力系数及局部阻力系数的影响.仿真的基本工况与风洞实验数据一致性很好,验证所采用数值方法的准确性和可靠性.研究结果表明,与未设置射流孔的模型相比,设置射流方案的模型尾流结构得以改善,纵向涡得以抑制,同时其阻力系数明显降低.单独位置布置射流孔方案中在斜面上方进行射流时,阻力系数最低,为0.252 2,减阻率为11.3%.通过正交试验获得最佳组合方案得到阻力系数0.246 7,减阻率达13.23%.     

高压天然气管道喷射火热辐射计算

天然气燃爆喷射火事故可能造成人员建筑严重损害,为研究大型天然气喷射火燃爆特性,使用CFD计算软件,对质量流量在5 kg/s以上,压力分别为12 MPa与6 MPa,泄漏孔径在25 mm、50 mm与100 mm时的高压天然气喷射火进行仿真,得到这六种工况下喷射火火焰尺寸、温度分布和近地热辐射强度分布曲线,并得到喷射火长度与宽度和泄漏孔直径的线性变化关系.与喷射火常用的Thornton模型对比,仿真结果计算的火焰长度基本符合,热辐射结果在泄漏中心30 m以外基本相近,两种方法都可用于估算远距离喷射火热辐射强度,为天然气设施安全设计提供参考.     

聚能射流水中侵爆盖板B炸药仿真研究

为获得聚能射流对水中盖板B炸药侵爆作用能力,开展水层厚度影响规律研究.基于准定常侵彻理论得到了紫铜聚能射流侵彻水介质时射流速度计算式;建立侵爆仿真模型,研究了聚能射流水中成型与运动、侵彻盖板及起爆装药的变化特性,计算给出了射流侵彻盖板前后的速度和直径的变化,结果表明,射流侵爆水中盖板B炸药的临界水层厚度为261 mm,并依据Held判据得出B炸药的起爆阈值为18.598 mm³·μs^-2.研究结果对聚能射流水下毁伤技术的应用提供技术参考.     

Numerical modeling of chlorine concentration in water storage tanks

In this paper, we describe a numerical model to simulate the evolution in time of the hydrodynamics of water storage tanks, with particular emphasis on the time evolution of chlorine concentration. The mathematical model contains several ingredients particularly designed for this problem, namely, a boundary condition to model falling jets on free surfaces, an arbitrary Lagrangian–Eulerian formulation to account for the motion of the free surface because of demand and supply of water, and a coupling of the hydrodynamics with a convection–diffusion–reaction equation modeling the time evolution of chlorine. From the numerical point of view, the equations resulting from the mathematical model are approximated using a finite element formulation, with linear continuous interpolations on tetrahedra for all the unknowns. To make it possible, and also to be able to deal with convection‐dominated flows, a stabilized formulation is used. In order to capture the sharp gradients present in the chlorine concentration, particularly near the injection zone, a discontinuity capturing technique is employed. Copyright © 2015 John Wiley & Sons, Ltd.     

A puzzle of the radio-quiet quasar PG 1407+265: Are optical and X-ray emissions produced from a relativistic jet?

PG 1407+265 is a radio quiet quasar that has a relativistic jet.In this report,we show some peculiar properties of its optical and X-ray emissions,which indicate possible non-thermal origins produced from the jet.We use a simple synchrotron + synchrotron self Compton (SSC) model to fit the emissions with different ratios of energy densities between the magnetic field and electrons (η≡U B/U e),which predicts a different γ-ray luminosity.The First LAT AGN Catalog (1LAC) did not include PG 1407+265,which indic...     

Reinvestigation of the ν2 + 2ν3 subband in the overtone icosad of 12CH4 using cavity ring-down (CRD) spectroscopy of a supersonic jet expansion

We report a detailed reinvestigation of the ν₂?+?2ν₃ combination band of methane ¹²CH₄ centred at (7510.3378?±?0.003)?cm^?1 ((225.154263?±?0.0001)?THz) within the icosad of the overtone absorption. A new experimental setup is described, allowing us to carry out cw-laser cavity ring-down spectroscopy (cw-CRDS) at instrumental resolution in the MHz range in seeded supersonic jet expansions down to rotational temperature of 7?K compared to previous cw-CRDS measurements in our group achieving about 50?K in expansions of neat CH₄. We provide a careful re-analysis on the basis of our new experimental results for the Q and R branch transitions including data obtained between about 7 and 300?K under various conditions. We resolve previously observed discrepancies of assignments and are able to present a definitive assignment for lines involving angular momentum quantum numbers up to J?=?4. The analysis of relative intensities in spectra taken at rotational and effective translational temperatures between about 50?K and less than 10?K indicate conservation of nuclear spin symmetry upon supersonic jet expansion, in agreement with previous results using other techniques and covering other spectral ranges.     

Dynamics of plasma channel in a parallel-plate plasma gun

Lumped parameter models for describing dynamics of the plasma channel in a parallel-plate plasma gun are compared with the experimental results obtained from two plasma guns with different rail geometries. Comparison between the experiments and the numerical calculations reveals that the lumped parameter models can be utilized to describe the dynamic motion of the plasma channel quite well. Parametric study shows that minimizing the line inductance and increasing the charging voltage on a capacitor as well as minimizing the gas injection time for reducing the mass of the plasma channel are the key factors to increase the flow velocity of the plasma jet ejected from the plasma gun.