共查询到19条相似文献,搜索用时 193 毫秒
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为研究螺旋转速对物料在垂直螺旋输送机中运动过程的影响,应用FLUENT软件,采用欧拉双流体模型以及RNG k-ε湍流模型,建立垂直螺旋输送机仿真模型,在进料量Q=1.2 kg/s、颗粒平均粒径为38.25μm和螺旋转速为475、500、525、550和600 r/min条件下,分析螺旋转速对垂直螺旋输送机内部流场的影响。研究表明:物料轴向速度随螺旋转速的增大而增大,增加螺旋转速能够较为平稳地提高输送量;颗粒填充率随螺旋转速的增大而减小,螺旋轴轴向力随螺旋转速提高而下降;随螺旋转速的增大,螺旋轴的轴向总力矩和功率呈下降趋势,但降幅逐渐减小。 相似文献
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采用三准则相似理论设计了循环流化床烟气脱硫气固两相流动试验台.通过对循环流化床脱硫反应器试验装置内沿高度方向阻力分布和不同高度截面上局部颗粒质量通量的测量,详细地研究了脱硫反应器内气固两相流动规律和内循环特性.结果表明:脱硫反应器阻力主要集中在文丘里管段,而且随着循环物料量和气体流量的增加,系统阻力显著增加;脱硫反应器内气固两相流动呈典型的环核流动结构,边壁下降流颗粒浓度高,中心区域上升流颗粒浓度低,且固体质量回流比率随着脱硫反应器高度的上升而下降.研究结果为循环流化床烟气脱硫系统的设计与放大提供了依据. 相似文献
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制造发生炉煤气的设备称为煤气发生炉。发生炉的类型,从床层的情况不同,可分为:1、固定床:间歇加料(煤块)、出料、床层固定不动;2、移动床:连续加料(煤块)与出料、床层中物料系连续移动,但床层高度及床层内各层分布稳定不变,故有时亦称之为固定床;3、流化床:当气体通过煤粉床层时,当流速增大时,煤粒被吹起而悬浮于气体中,自山地向各方运动,当流速继续增大床层中颗粒运动加剧,且作上下翻滚运动,此时整个床层具有类似流休的性质,称为流化床。根据气化时的压力不同,可分为常压气化与高压气化两种类型。 相似文献
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利用数值分析方法研究了新型仿螺旋肋片内冷通道的传热与流动特性。采用横截面积为矩形、上下表面带有间断性倾斜矩形肋片叉排且对置的仿螺旋肋片内部冷却通道。分析了在通道宽高比AR=2.9、肋化比Ff/F=2.545、肋高与通道当量直径比e/Dh=0.336、肋间距与肋高比p/e=0.6、肋片与轴面的夹角β=15°及R e在1×104~2×105时的非旋转情况下,R e、肋片与主流方向夹角α等参数对内冷通道强化传热与流动阻力特性的影响。计算结果表明,该仿螺旋矩形肋片作为旋流形成装置起到了迫使流体旋转运动、提高流速和减小层流底层厚度的作用,通道内流体流动达到了预期的螺旋流动效果,通道平均换热系数得到了明显的提高,但同时流动阻力也显著增加。 相似文献
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为了探究级联堆积床内不同相变材料(PCM)的比例对热性能的影响,共建立7种堆积比的相变胶囊蓄热堆积床物理模型,通过数值模拟方法监测换热流体和PCM温度等指标,并对比分析了蓄热量、?效率、蓄热速率和蓄热速率密度等表征堆积床热性能的指标。结果表明:随着高熔点相变材料占比的增加,堆积床可以获得较高的?效率,但其他指标均随着低熔点相变材料占比的增加而升高;与均分的级联堆积床相比,按熔点从低至高,PCM占比呈梯级升高或降低的级联堆积床的蓄热品质及蓄热效率提升显著,证明合理优化级联堆积床内相变材料的比例可有效提升级联堆积床的热性能。 相似文献
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为了分析颗粒浓度对高比转速离心泵非定常特性的影响,采用Mixture混合多相流模型,利用CFX软件进行数值模拟,分析了不同颗粒浓度时的瞬时湍动能、压力脉动及径向力。研究表明:随着颗粒浓度的增加,效率有所下降,清水条件下的离心泵效率最优;随着颗粒浓度的增大,叶轮内的瞬时湍动能明显增强,叶轮流道内及隔舌处的压力值均减小,脉动幅值均增大,作用在叶轮上的径向力会增大,而作用在隔舌处的径向力会减小;在不同颗粒浓度下,叶轮流道内的压力脉动主频均出现在转频处;隔舌处的压力脉动主频出现在叶频处;叶轮流道内、隔舌处的压力值和压力脉动幅值增减速度快慢的分界点和叶轮上、隔舌处的径向力增减速度快慢的分界点均在颗粒浓度为1%附近。 相似文献
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Jianjun DaiJohn R. Grace 《Biomass & bioenergy》2011,35(2):942-955
Successful feeding is critical to biomass utilization processes, but difficult due to the heterogeneity, physical properties and moisture content of the particles. The objectives of the present study were to find the mechanisms of blockage in screw feeding and to determine the effects of particle mean size (0.5-15 mm), size distribution, shape, moisture content (10-60%), density and compressibility on biomass particle feeding at room temperature. Wood pellets, sawdust, hog fuel and wood shavings were tested in a screw feeder/lock hopper system previously employed to feed sawdust into a pilot-scale circulating fluidized-bed gasifier. Experimental results showed that large particles, wide size distributions, large bulk densities and high moisture contents generally led to larger torque requirements for screw feeding. The “choke section” and seal plug play important roles in determining the torque requirements. 相似文献
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Full-annulus three-dimensional unsteady numerical simulations were conducted for a low-speed isolated axial compressor rotor,
intending to identify the behavior of self-induced unsteady tip leakage flow within multi-blade passages. There is a critical
mass flow rate near stall point, below it, the self-induced unsteadiness of tip leakage flow can propagate circumferentially
and thus initiates two circumferential waves. Otherwise, the self-induced unsteady tip leakage flow oscillates synchronously
in each single blade passage. The major findings are: 1) while the self-induced unsteadiness of tip leakage flow is a single-passage
phenomenon, there exist phase shifts among blade passages in multi-passage environments then evolving into the first short
length wave propagating at about two times of rotor rotation speed after the transient period ends; and 2) the time traces
of the pseudo sensors located on the rotor blade tips reveal another much longer length-scale wave modulated with the first
wave due to phase shift propagating at about half of rotor rotation speed. Features of the short and long length-scale circumferential
waves are similar to those of rotating instability and modal wave, respectively. 相似文献
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PIV measurements and CFD simulation of the performance and flow physics and of a small‐scale vertical axis wind turbine 下载免费PDF全文
The aerodynamics generated by a small small‐scale vertical axis wind turbine are illustrated in detail as a NACA0022 rotor blade carries out a complete rotation at three tip speed ratios. These aerodynamic details are then linked to the wind turbine performance. This is achieved by using detailed experimental measurements of performance and near‐blade particle image velocimetry (PIV) and also by using a two‐dimensional Reynolds‐averaged Navier–Stokes‐based computational fluid dynamics (CFD) model. Uniquely, therefore, the CFD model is validated against both PIV visualizations and performance measurements. At low tip speed ratios ( λ = 2), the flow field is dominated by large‐scale stalling behaviour as shown in both the experimental results and simulations. The onset of stall appears to be different between the experiment and simulation, with the simulation showing a gradual separation progressing forward from the trailing edge, while the experiment shows a more sudden leading‐edge roll‐up. Overall, similar scales of vortices are shed at a similar rate in both the experimental results and simulations. The most significant CFD–PIV differences are observed in predicting flow re‐attachment. At a higher tip speed ratio ( λ = 3), the flow separates slightly later than in the previous condition, and as occurs in the lower tip speed ratio, the main differences between the experiment and the simulation are in the flow re‐attachment process, specifically that the simulations predicts a delay in the process. At a tip speed ratio of 4, smaller predicted flow separation in the latter stages of the upwind part of the rotation is the main difference in comparison to the experiment. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献