滤芯褶数对气体过滤器流体动力学性能影响的研究

基于三维褶模型,采用CFD技术对空气过滤器性能进行数值模拟计算,使用FLUENT软件中的多孔介质模型对空气过滤器进行了流体动力学分析。结果表明,增大进口风量会使过滤器阻力增大;增加滤芯褶数会增大过滤器的有效过滤面积,增大有效过滤面积可以降低过滤速度,从而减小滤芯过滤阻力。然而这种增加不是无限制的,增加褶数会减小褶间距,过小的褶间距会导致气流局部紊乱,气体间摩擦阻力增大,从而使得整个过滤器阻力增大。对于一定尺寸的过滤器存在一个最优的褶数使得过滤阻力最小。

基于CFD的双褶数滤袋阻力特性的数值模拟

为了研究过滤阻力对除尘器过滤性能的影响,建立基于CFD的标准k-ε湍流模型和多孔跳跃模型,对褶数为8和10的2种除尘器滤袋在不同入口风速时沿轴向过滤压降分布进行数值模拟。模拟出一种新型组合式双褶数滤袋,采用不均匀度和相对标准差分析双褶数滤袋与常规褶式滤袋的压降分布不均匀性。结果表明:褶式滤袋沿轴向上的压降分布呈非均匀现象,从袋底到袋口呈梯次变化,靠近袋口位置的压降较大;压降的不均匀性随着入口风速的增大而更加明显。增加滤袋的上半部褶数从而增大相应的过滤面积,使气流流量分布均匀,可使顶部的压降有效降低11.2%~15.4%;双褶数滤袋的压降分布相对较均匀,除尘器进出口过滤压降最大可降低13.5%,有效降低除尘器的运行能耗。

滤筒结构优化试验研究

首先分析了滤筒的直径、褶高、褶数和滤筒夹角之间的关系 ,然后通过试验研究 ,对比了同一直径不同褶高不同褶数的 6种滤筒的性能 ,得到了滤筒理想夹角和褶高。

褶型筒式空气过滤器过滤压降的数值模拟

基于计算流体力学(CFD),采用FLUENT中的多孔介质模型对褶型空气过滤器进行数值模拟研究,通过模拟计算和实验研究得到了空气过滤器的一些阻力性能。结果表明,褶型空气过滤器在过滤气体中的杂质时,过滤器的阻力随着进口风量的增大而增大;而增加过滤器的褶数会增大过滤器的过滤面积,过滤器的过滤面积增大之后过滤器的过滤速度会相应减小,由此可以减小过滤器的阻力。但是增加过滤器的褶数之后会相应的改变过滤器滤芯的褶间距,褶间距的大小会对气流的流动产生影响。气流的流动会影响过滤器的阻力。这些研究可以为过滤器滤芯的设计及应用提供一定的依据。

精血归颗粒对初老大白鼠阴道组织的影响

精血归颗粒能使初老大白鼠阴道粘膜增厚、褶襞数增多 ,阴道上皮细胞糖原含量反应增高 。

Nonstationary sparsity-constrained seismic deconvolution

The Robinson convolution model is mainly restricted by three inappropriate assumptions, i.e., statistically white reflectivity, minimum-phase wavelet, and stationarity. Modern reflectivity inversion methods（e.g., sparsity-constrained deconvolution） generally attempt to suppress the problems associated with the first two assumptions but often ignore that seismic traces are nonstationary signals, which undermines the basic assumption of unchanging wavelet in reflectivity inversion. Through tests on reflectivity series, we confirm the effects of nonstationarity on reflectivity estimation and the loss of significant information, especially in deep layers. To overcome the problems caused by nonstationarity, we propose a nonstationary convolutional model, and then use the attenuation curve in log spectra to detect and correct the influences of nonstationarity. We use Gabor deconvolution to handle nonstationarity and sparsity-constrained deconvolution to separating reflectivity and wavelet. The combination of the two deconvolution methods effectively handles nonstationarity and greatly reduces the problems associated with the unreasonable assumptions regarding reflectivity and wavelet. Using marine seismic data, we show that correcting nonstationarity helps recover subtle reflectivity information and enhances the characterization of details with respect to the geological record.

Experimental analysis and application of sparsity constrained deconvolution

Sparsity constrained deconvolution can improve the resolution of band-limited seismic data compared to conventional deconvolution. However, such deconvolution methods result in nonunique solutions and suppress weak reflections. The Cauchy function, modified Cauchy function, and Huber function are commonly used constraint criteria in sparse deconvolution. We used numerical experiments to analyze the ability of sparsity constrained deconvolution to restore reflectivity sequences and protect weak reflections under different constraint criteria. The experimental results demonstrate that the performance of sparsity constrained deconvolution depends on the agreement between the constraint criteria and the probability distribution of the reflectivity sequences; furthermore, the modified Cauchy- constrained criterion protects the weak reflections better than the other criteria. Based on the model experiments, the probability distribution of the reflectivity sequences of carbonate and clastic formations is statistically analyzed by using well-logging data and then the modified Cauchy-constrained deconvolution is applied to real seismic data much improving the resolution.

Fransdimensional Bayesian inversion of timedomain airborne EM data

To reduce the dependence of EM inversion on the choice of initial model and to obtain the global minimum, we apply transdimensional Bayesian inversion to time-domain airborne electromagnetic data. The transdimensional Bayesian inversion uses the Monte Carlo method to search the model space and yields models that simultaneously satisfy the acceptance probability and data fitting requirements. Finally, we obtain the probability distribution and uncertainty of the model parameters as well as the maximum probability. Because it is difficult to know the height of the transmitting source during flight, we consider a fixed and a variable flight height. Furthermore, we introduce weights into the prior probability density function of the resistivity and adjust the constraint strength in the inversion model by changing the weighing coefficients. This effectively solves the problem of unsatisfactory inversion results in the middle high-resistivity layer. We validate the proposed method by inverting synthetic data with 3% Gaussian noise and field survey data.

Numerical simulation of wrinkle phenomenon during multi-point forming process of shallow rectangle cup

In this paper, the principle of multi-point forming (MPF) technique is presented. One of the most serious defects, wrinkling, during the multi-point forming process of a shallow rectangle cup is discussed by means of numerical simulation on the shallow rectangle cup forming process. The effects of thickness, material of sheet metal and the pressure of the blank holder are investigated. Based on the simulation results, the reasons and control methods of wrinkling are pointed out. Moreover, the experiment on the multi-point die forming of the shallow rectangle cup by the MPF machine is done to validate the efficiency of the numerical simulation, and the result proves that the application of an elastic cushion in the forming can restrain wrinkling efficiently.

Estimating Field Source Parameters of Gravity Change in North China Based on the Euler Deconvolution Method

Based on the absolute and relative gravity observations in North China from 2009 to 2014,spatial dynamic variations of the regional gravity field are obtained. We employed the Euler deconvolution method and the theoretical model to get the best estimates of parameters. Gravity field change caused by the depth and distribution in North China is calculated by back analysis. The results show the structural index that equals 1 is suitable for inversion of the gravity variation data. The inversion results indicate that the depths of anomaly field sources are spread over the Hetao fault. The research method of this paper can be used in the quantitative study on the field source and may shed new light on the interpretations of gravity change, and also provide quantitative basis for earthquake prediction index criterions based on the gravity change.

无纺针刺毡滤料褶式滤袋的阻力特性分析

以滤袋褶形结构的高宽比ɑ为优化对象,建立不同褶数下的褶式滤袋结构的三维几何模型,采用多孔介质及标准k-e双方程湍流模型对褶数N=8, 12, 16, 20, 24、袋长L=2.5, 3.0, 3.5 m的褶式滤袋进行气相流场的数值模拟。结果表明,相同进口风速下,褶数N=12 (ɑ=1.12)的褶式滤袋的过滤阻力最小,过滤阻力随进口风速的增长率明显小于其它4种褶数,袋室内的流场分布更均匀,对不同处理风量的工况适应性较好。不同袋长的褶式滤袋除尘器的过滤阻力均随进口风速增加呈二次曲线式增长,处理风量较小时,褶式滤袋越长系统压损越小,但褶式滤袋过短或过长时因系统压损较大均不适宜在高风量下运行,其中L=3.0 m的滤袋其垂直方向的压差梯度较小,袋室内的压力及速度分布更均匀,有利于保护滤袋,降低运行能耗。