月牙肋岔管肋板內缘曲线对结构受力特性的影响

重点研究肋板內缘曲线对肋板乃至管壳受力特性的影响,采用有限单元法,通过对典型月牙肋钢岔管肋板内缘采用不同曲线型式时的结构特性分析,研究月牙肋岔管肋板內缘曲线对肋板乃至管壳结构受力特性的影响。研究结果表明:在肋宽比相同的前提下,肋板采用椭圆曲线或抛物线对管壳应力的计算结果影响不大,而对肋板的应力分布影响较大。肋板的内缘曲线宜优先选用椭圆曲线,并通过有限元法计算优化内缘曲线方程。     

考虑初始几何缺陷的大型钢板筒仓构造措施的研究

钢板筒仓在煤炭、电力、粮食等行业中有着广泛的应用,对其构造措施进行研究十分必要。通过数值分析方法,从加劲肋的设置范围及位置、加劲肋宽度、加劲肋厚度、加劲肋间距等方面对存在初始几何缺陷的钢板筒仓不同加劲肋构造的稳定性能进行了研究。研究表明,加劲肋应设置在0～16 m范围内;环向加劲肋选L125×10号等边角钢,环向加劲肋间距2 000 mm;竖向加劲肋选10 mm厚100 mm宽的钢板,竖向加劲肋间距1 600 mm。影响仓壁屈曲承载力的主要因素是加劲肋的设置范围,其次加劲肋的宽度、间距和厚度也是影响仓壁屈曲承载力的重要参数。     

某高水头电站地下埋藏式钢岔管体型结构优化

受复杂水文地质条件影响,地下埋藏式钢岔管体型结构设计难度较大。根据某高水头抽水蓄能电站实际地质资料及岔管体型参数,采用有限元计算方法研究不同管壁厚度及不同月牙肋肋宽比方案钢岔管应力分布情况。结果表明,管壁及月牙肋厚度不变的情况下,适当加大月牙肋肋宽比,可显著降低月牙肋应力,同时钢管管壁应力也有所降低。在月牙肋厚度及肋宽比不变的情况下,管壁及月牙肋应力均随着管壁厚度加大而降低,但幅值较加大肋宽比方案小。     

渔洞水库北干渠葡萄井肋拱渡槽结构计算研讨

采用大跨度的肋拱支承渡槽，肋拱型式和结构尺寸对肋拱纵向、横向稳定影响很大，采用悬链线拱时，截面优选变截面肋拱，变截面肋拱较能适应内力和应力变化。     

肋板形状对月牙肋钢岔管应力影响的研究

结合某水电站月牙肋钢岔管的工程实际,利用自主研发的月牙肋岔管体形设计程序和ANSYS软件,对岔管结构进行三维有限元计算,得到了不同分岔角下各肋板方案的计算结果,对比了管壳及肋板关键点的应力,讨论了不同肋板形状对肋板应力分布及管壳应力的影响。研究认为,管壳最大应力在肋板内缘曲线为椭圆曲线时较小,肋板水平截面应力在肋板内缘曲线为椭圆曲线,外缘曲线相对于相贯线偏移不等宽时较小,同时应力分布更加均匀,有利于发挥钢材的作用。     

拱肋间距对喷混凝土拱肋加固效应的影响研究

喷混凝土拱肋是加固软弱围岩的一种有效支护形式,其间距主要根据经验确定,可能偏大或偏小。为了揭示拱肋间距对加筋拱肋加固效应的影响,采用基于有限差分法的FLAC3D软件对施工期某地下厂房交通洞软弱围岩在拱肋间距分别在1.0―5.0m之间变化情况下变形、应力和屈服区等分布规律进行了对比仿真模拟。仿真结果表明:拱肋间距越大,围岩变形、顶拱最大主压应力和塑性屈服区越大,拱肋承受荷载越大;且拱肋间距介于2.0―3.0m时,能充分发挥围岩自承作用和拱肋支护潜力,围岩变形稳定满足要求,支护成本最低。本文的研究成果为确定喷混凝土拱肋合理间距提供了重要参考。     

水电站月牙肋岔管设计及其计算绘图程序开发

对水电站压力钢管中的月牙肋岔管肋板设计进行分析,并给出了肋板曲线方程,同时采用Auto LISP语言开发出可以在Auto CAD下运行的月牙肋岔管计算及绘图程序。图4幅。     

大跨度钢管混凝土拱桥拱肋混凝土无隔舱泵送施工技术

在一般的大跨度钢管拱桥拱肋混凝土施工中,一般采用有隔舱泵送施工方法,即在拱肋间加焊隔舱板并在两侧分别设置排气孔,使拱肋内混凝土气泡顺利排出,使拱肋混凝土密实、饱满。而作者结合其施工大跨度钢拱桥拱肋混凝土泵送施工经验,总结出了一套无隔舱泵送大跨度钢管拱肋混凝土施工技术,采用此方法施工后的拱肋内混凝土同样饱满、密实。     

凉风垭肋拱渡槽设计与施工

本文介绍了一座肋拱连拱渡槽采用单片拱肋侧卧地面全肋预测，吊起悬空翻转扶直，组合安装就位技术及相应的设计施工情况，该技术对于修建中、短跨度的肋拱结构具有借鉴、推广应用价值。     

冷轧带肋钢筋焊接网的工程应用

扼要介绍冷轧带肋钢筋焊接网所用的材料－－冷轧带肋钢筋（LL550级）的性能以及冷轧带肋钢筋焊接网的施工技术要点和在工程中的具体应用。     

内管纵向敷肋时套管式换热器传热研究

本文对水平放置的套管式换热器内管外表面纵向敷肋时的传热性能作了数值计算。研究了管径比，肋高比及Ｒａｙｌｅｉｇｈ数的影响。     

Numerical simulation of thermal convection of viscoelastic fluids in an open-top porous medium with constant heat flux

This paper makes a numerical study of the buoyancy-driven convection of a viscoelastic fluid saturated in an open-top porous square box under the constant heat flux boundary condition. The effects of the relaxation and retardation times on the onset of the oscillatory convection, the convection heat transfer rate and the flow pattern transition are investigated. It is shown that a large relaxation time can destabilize the fluid flow leading to an early onset of the thermal convection and a high heat transfer rate, while a large retardation time tends to stabilize the flow and suppress the convection onset and the heat transfer. After the convection sets in, the flow bifurcation appears earlier with the increase of the relaxation time and the decrease of the retardation time, resulting in more complicated flow patterns in the porous medium. Furthermore, with the increase of the ratio of the relaxation time to the retardation time, the fluid may be blocked from flowing through the open-top boundary, which may be caused by the viscoelastic effect. Finally, the comparison of our results with those under isothermal heating boundary conditions reveals that the heat transfer rate corresponding to a constant heat flux boundary is always higher.     

墙体传热对流辐射比例的特性研究

利用实验室墙体内壁敷设电热膜模拟实际墙体传热,通过表面热流计获得该壁面的总传热量,通过有效辐射计算方法和热平衡方法获得墙体净辐射热量和对流换热量,由此达到对流热量和辐射热量分离的目的。论文通过实验结果探讨墙体传热中对流辐射分离比例与墙体传热量、房间换气次数以及传热墙体附近气流形式的关联。结果表明:对流辐射分离中,对流比例受墙体传热量和换气次数的影响不大;受传热墙体附近气流形式影响很大,送风口下墙体传热量中对流比例远大于回风口下墙体传热量中的对流比例。     

泵站技术供水盘管冷却器布置与换热面积计算

根据泵站工程特点,利用置于天然水体中进行冷却的盘管冷却器组成的密闭循环供水系统,是一种节能、可靠的技术供水方式。依据传热学理论对盘管冷却器传热原理进行分析后,提出不同安装形式的冷却盘管换热面积计算公式。研究发现,当盘管处于静止水体中且以自然对流传热为主而利用水体容量带走热量时,所需盘管的换热面积最大;当盘管处于流动水体中且以强制对流传热为主而利用水体流动带走热量时,所需盘管换热面积较小;采取加大管道内部热流体或管道外部冷却水体流速代射,可以减少换热面积,但需相应增加管道安装要求和运行成本;为节省投资、延长使用寿命,盘管换热材料建议采用不锈钢材质。     

混水角对强迫对流混水过程影响的熵产数值分析

以两入口流速相同情况下强迫对流混水过程这一物理问题为研究对象,采用计算流体力学、数值传热学理论进行数值计算,分析讨论了对流混水角在30°、45°、60°、90°条件下速度、温度、熵产的分布以及变化关系.计算、分析结果表明:熵产主要分布在两根进水管的交汇区域,及混水后的出水管区域,最大值发生在混水交点处,而两进口支管区域...     

圆形封闭水箱非稳态数值模拟

采用数值方法对圆形封闭水箱内放置两根加热管的二维流动传热进行了非稳态数值模拟,探讨了Ra数从104到107四种情况和封闭水箱的加热管不同摆放位置下的流动和换热;对流场和温度场进行了分析,讨论了不同情况下加热管平均努赛尔数(Nuavg)的变化情况。数值模拟结果表明,随着Ra数增大水箱内的流动表现出了很大变化,决定了传热是导热或者是对流;两个水平加热管在水箱存在最佳的放置距离,这样可以使自然对流情况下的换热达到最好。     

NUMERICAL STUDY ON SORET-EFFECT AND DUFOUR-EFFECT FOR DOUBLE-DIFFUSIVE NATURAL CONVECTION IN POROUS ENCLOSURE

The influences of Soret effect and Dufour effect on the natural convection and heat and mass transfer for a porous enclosure were investigated by means of the penalty finite element method. Numerical results indicate that the Soret and Dufour effects have significant influences on heat and mass transfer in the presence of large temperature gradient and concentration gradient.     

NATURAL CONVECTIVE HEAT AND MASS TRANSFER BY THE COUPLING OF TEMPERATURE CRADIENT AND CONCENTRATION GRADIENT IN A POROUS MEDIUM

ＮＡＴＵＲＡＬＣＯＮＶＥＣＴＩＶＥＨＥＡＴＡＮＤＭＡＳＳＴＲＡＮＳＦＥＲＢＹＴＨＥＣＯＵＰＬＩＮＧＯＦＴＥＭＰＥＲＡＴＵＲＥＣＲＡＤＩＥＮＴ　ＡＮＤＣＯＮＣＥＮＴＲＡＴＩＯＮＧＲＡＤＩＥＮＴＩＮＡＰＯＲＯＵＳＭＥＤＩＵＭ￥ＣｈｅｎＢａＯ－Ｍｉｎｇ；Ｆ...     

Combined effect of Reynolds and Grashof numbers on mixed convection in a lid-driven T-shaped cavity filled with water-Al_2O_3 nanofluid

Lid-driven mixed convection has been given immense importance due to its wide range of applications. A T-shaped cavity is introduced and pertinent parameters controlling mixed convection phenomenon are analyzed in this paper. Water-Al2O3 nanofluid is considered inside the cavity to augment heat transfer rate. Galerkin weighted residual method of finite element analysis is applied for the numerical simulations. Numerical solution is obtained for different solid volume fractions of nanofluid(?= 0- 0.15), Grashof numbers(Gr= 0.1 ?5 000) and Reynolds numbers(Re= 0.31 ?1 000) in laminar flow regime. Special attention is given on the analysis of flow at the pure mixed convection regime. It is found that Grashof, Reynolds and Richardson numbers along with solid volume fraction of nanofluid have significant effect on heat transfer characteristics inside the cavity. Results are presented using streamline and isotherm contours along with related variation of average Nusselt numbers of the heated wall and average fluid temperature inside the cavity.     

The viscoelastic effects on thermal convection of an Oldroyd-B fluid in open-top porous media

The effects of two viscoelastic parameters on the thermal convection of a viscoelastic Oldroyd-B fluid in an open-top porous square box with constant heat flux are investigated. The results show that the increase of relaxation time is able to destabilize the fluid flow leading to a higher heat transfer rate, while the increase of retardation time tends to stabilize the flow and suppress the heat transfer. The flow bifurcation appears earlier with the increase of the relaxation time and the decrease of the retardation time, resulting in more complicated flow patterns in the porous medium.