基于相变效应的内压型螺旋槽液膜密封性能分析

液膜相变现象不仅改变了端面润滑状态,而且对密封性能及稳定性有着显著的影响。使用有限体积法对控制方程进行离散,研究了螺旋槽结构参数与密封工况参数对密封性能及液膜相变率的影响。结果表明：开启力与泄漏量随螺旋角、槽数、槽深、压差、转速的增大而增大,随槽面宽比、槽台宽比的增大先增大后减小,分别在槽面宽比ζ=0.5与槽台宽比φ=0.7时取到最大值。相变率随螺旋角、转速的增大而增大,随槽数、槽深、压差、槽台宽比的增大而减小,随槽面宽比的增大先减小后增大,在槽面宽比ζ=0.8时取最小值。通过对各参数合理地选择与组合,可以有效地抑制相变进程,进而在保证密封运行稳定的同时利用相变现象提高密封性能。     

基于相变效应的内压型螺旋槽液膜密封性能分析

液膜相变现象不仅改变了端面润滑状态,而且对密封性能及稳定性有着显著的影响。使用有限体积法对控制方程进行离散,研究了螺旋槽结构参数与密封工况参数对密封性能及液膜相变率的影响。结果表明:开启力与泄漏量随螺旋角、槽数、槽深、压差、转速的增大而增大,随槽面宽比、槽台宽比的增大先增大后减小,分别在槽面宽比ζ=0.5与槽台宽比φ=0.7时取到最大值。相变率随螺旋角、转速的增大而增大,随槽数、槽深、压差、槽台宽比的增大而减小,随槽面宽比的增大先减小后增大,在槽面宽比ζ=0.8时取最小值。通过对各参数合理地选择与组合,可以有效地抑制相变进程,进而在保证密封运行稳定的同时利用相变现象提高密封性能。     

柱面螺旋槽气膜密封微尺度流动场稳态特性分析

针对燃气轮机转子振动较大的特点,提出一种新型柱面螺旋槽气膜密封。利用考虑滑移边界条件下的微尺度效应稳态柱面雷诺方程,求解柱面气膜的压力的近似解析解,获得柱面螺旋槽气膜量纲1浮升力、泄漏量以及摩擦转矩,并讨论了工况参数和螺旋槽结构参数对稳态性能的影响。综合考虑参数对稳态特性的影响,提出优化结构参数。结果表明:密封压差对稳态特性的影响要远大于偏心率。在不同的偏心率下,螺旋槽槽数对浮升力的影响不明显,随着槽数的增加,摩擦转矩升高,泄漏量降低并在槽数n=12左右趋于稳定;随着槽深的增大,浮升力呈下降趋势,摩擦转矩和泄漏量相应增大;随着密封宽度增大,浮升力呈上升趋势,但偏心率不同,上升幅度不同;泄漏量在密封宽度L=0.035 m处基本稳定。螺旋角的增大导致了浮升力的下降,摩擦转矩和泄漏量呈上升趋势。在密封压差的作用下,摩擦转矩随着4种结构参数的增大而上升。槽数增大导致浮升力下降,与槽深的影响刚好相反。随着密封宽度的增加浮升力先降低后升高,与螺旋角的影响刚好相反。槽数和密封宽度的增加导致泄漏量快速下降至稳定值。提出优化的结构参数如下:槽数n=12~18,密封宽度L=0.03~0.045 m,螺旋角α=40°~50°。     

干气密封螺旋槽几何参数优选交互影响

为解决干气密封（DGS）端面型槽优化中未考虑型槽几何参数之间对目标函数交互影响而导致几何参数优化结果不准确的问题,研究了不同速度条件下DGS螺旋槽中其他几何参数对某一几何参数优选值的交互影响。基于气体润滑理论,建立了螺旋槽DGS的几何模型和数学模型,数值求解获得端面膜压分布和稳态性能参数,定义了综合表征螺旋槽几何结构的特征参数。以气膜刚度最大为优选目标,获得了不同速度条件下DGS螺旋槽中某一几何参数优选值随其他几何参数的变化规律。结果表明：DGS螺旋槽各几何参数两两之间呈现出复杂的交互影响关系,不过总体符合趋向于降低槽内实际通流面积、槽长宽比和槽长深比3个综合参数变化幅值的原则;与单因素优化方法相比,在给定算例参数条件下所提出的考虑几何参数交互影响的优化方法所获得气膜刚度最优值提高11.4%。     

上游泵送人字槽液膜密封结构优化设计

以上游泵送人字槽液膜密封为研究对象,采用有限差分法求解稳态雷诺方程和传热方程,分析密封端面结构参数对密封稳态性能的影响。结果表明:随台槽比的增大,泄漏量和液膜刚度先增大后减小,密封环最高温度和总变形锥度变大;随螺旋角和槽深的增大,泄漏量和液膜刚度变大,密封环最高温度和总变形锥度变小;随槽数的增多,泄漏量和液膜刚度减小,密封环最高温度和总变形锥度变大。为保证上游泵送人字槽液膜密封有较好的密封性能,建议取台槽比为1~1.5,螺旋角为20°~24°,槽深为9~13μm,槽数为24~36个。     

干气密封螺旋槽几何参数优选交互影响

为解决干气密封(DGS)端面型槽优化中未考虑型槽几何参数之间对目标函数交互影响而导致几何参数优化结果不准确的问题,研究了不同速度条件下DGS螺旋槽中其他几何参数对某一几何参数优选值的交互影响。基于气体润滑理论,建立了螺旋槽DGS的几何模型和数学模型,数值求解获得端面膜压分布和稳态性能参数,定义了综合表征螺旋槽几何结构的特征参数。以气膜刚度最大为优选目标,获得了不同速度条件下DGS螺旋槽中某一几何参数优选值随其他几何参数的变化规律。结果表明:DGS螺旋槽各几何参数两两之间呈现出复杂的交互影响关系,不过总体符合趋向于降低槽内实际通流面积、槽长宽比和槽长深比3个综合参数变化幅值的原则;与单因素优化方法相比,在给定算例参数条件下所提出的考虑几何参数交互影响的优化方法所获得气膜刚度最优值提高11.4%。     

含气条件对井下油水分离旋流器性能影响的数值模拟

为探究气体对井下油水旋流器性能的影响规律,针对新型螺旋流道倒锥式旋流器,采用Fluent软件对气液比分别为0.01、0.03、0.05、0.08、0.10时旋流器的油相分布进行模拟分析。通过对比分析发现:不含气时旋流器的分离效率为89.31%;在结构参数和分流比不变的条件下,旋流器分离效率随气液比的增加呈降低趋势,气液比为0.10时,分离效率为36.90%;气液比越大,溢流口的油相体积分数越小,底流口的油相体积分数越大;溢流口和底流口的压力损失随气液比的增大而递减。     

双列螺旋槽液膜密封相变现象及性能

为了探究相变现象对密封性能的影响规律,通过联立N-S方程与质量输运方程,建立了液膜密封相变模型,使用有限体积法对控制方程进行离散,对双列螺旋槽液膜密封相变现象进行了仿真模拟,获得了液膜流线及相态分布并分析了结构参数对相变区域与密封性能的影响。结果表明：液膜发生相变后物性参数发生变化,密封间隙内流场与端面压力分布发生明显改变。内侧螺旋槽可以提供稳定的开启力并保证密封端面处于较好的润滑状态,但同时导致密封泄漏增加。通过减小外侧螺旋槽槽面宽比、槽台宽比、螺旋角、槽深或增大外侧螺旋槽槽数均可降低密封泄漏量,提升密封性能。     

双列螺旋槽液膜密封相变现象及性能

为了探究相变现象对密封性能的影响规律,通过联立N-S方程与质量输运方程,建立了液膜密封相变模型,使用有限体积法对控制方程进行离散,对双列螺旋槽液膜密封相变现象进行了仿真模拟,获得了液膜流线及相态分布并分析了结构参数对相变区域与密封性能的影响。结果表明:液膜发生相变后物性参数发生变化,密封间隙内流场与端面压力分布发生明显改变。内侧螺旋槽可以提供稳定的开启力并保证密封端面处于较好的润滑状态,但同时导致密封泄漏增加。通过减小外侧螺旋槽槽面宽比、槽台宽比、螺旋角、槽深或增大外侧螺旋槽槽数均可降低密封泄漏量,提升密封性能。     

自泵送流体动压型机械密封性能分析

基于离心泵工作原理提出了一种自泵送流体动压型机械密封,并运用Fluent软件对自泵送型槽进行了三维流场动力学仿真分析,探讨了几何参数和工况参数对自泵送流体动压型机械密封性能即端面开启力和泄漏率的影响。研究结果表明:转速增大,开启力和泄漏率均减小;介质压力、槽台宽比、引流孔孔径及螺旋角增大,开启力和泄漏率均增大;随着槽数、槽长坝长比的增大,开启力均有所降低,泄漏率略有增大;槽深对开启力和泄漏率的影响趋势相似,存在一个使开启力较大而泄漏率较小的槽深;通过型槽参数匹配,自泵送流体动压型机械密封可以获得足够的开启力和较低的泄漏率。     

螺旋槽机械密封的改进设计

The coupling effect among the flow of fluid film,the frictional heat of fluid film and the thermal de- formation of sealing rings is inherent in mechanical seals.The frictional heat transfer analysis was carried out to op- timize the geometrical parameters of the sealing rings,such as the length,the inner radius and the outer radius.The geometrical parameters of spiral grooves,such as the spiral angle,the end radius,the groove depth,the ratio of the groove width to the weir width and the number of the grooves,were optimized by regarding the maximum bearing force of fluid film as the optimization objective with the coupling effect considered.The depth of spiral groove was designed to gradually increase from the end radius of spiral groove to the outer radius of end face in order to de- crease the weakening effect of thermal deformation on the hydrodynamic effect of spiral grooves.The end faces of sealing rings were machined to form a divergent gap at inner radius,and a parallel gap will form to reduce the leakage rate when the thermal deformation takes place.The improved spiral groove mechanical seal possesses good heat transfer performance and sealing ability.     

Influence of slug flow on flow fields in a gas-liquid cylindrical cyclone separator: A simulation study

A simulation method for slug flow based on the VOF multiphase flow model was implemented in ANSYS^® Fluent via a user-defined function (UDF) and applied to the dissipation of liquid slugs in the inlet pipe of a gas-liquid cylindrical cyclone (GLCC) separator while varying the expanding diameter ratio and angle of inclination. The dissipation of liquid slug in inlet pipe is analyzed under different expanding diameter ratios and inclination angles. In the inlet pipe, it is found that increasing expanding diameter ratio and inclination angle can reduce the liquid slug stability and enhancing the effect of gravity, which is beneficial to slug flow dissipation. In the cylinder, increasing the expanding diameter ratio can significantly reduce the liquid carrying depth of the gas phase but result in a slightly increase of the gas content in the liquid phase space. Moreover, increasing the inclination angle results in a decrease in the carrying depth of liquid in the vapor phase, but enhances gas-liquid mixing and increases the gas-carrying depth in the liquid phase. Taking into consideration the dual effects of slug dissipation in the inlet pipe and carrying capacity of gas/liquid spaces in the cylinder, the optimal expanding diameter ratio and inclination angle values can be determined.     

Influence of slug flow on flow fields in a gas–liquid cylindrical cyclone separator:A simulation study

A simulation method for slug flow based on the VOF multiphase flow model was implemented in ANSYS? Fluent via a user-defined function(UDF) and applied to the dissipation of liquid slugs in the inlet pipe of a gas–liquid cylindrical cyclone(GLCC) separator while varying the expanding diameter ratio and angle of inclination. The dissipation of liquid slug in inlet pipe is analyzed under different expanding diameter ratios and inclination angles.In the inlet pipe, it is found that increasing expanding diameter ratio and inclination angle can reduce the liquid slug stability and enhancing the effect of gravity, which is beneficial to slug flow dissipation. In the cylinder, increasing the expanding diameter ratio can significantly reduce the liquid carrying depth of the gas phase but result in a slightly increase of the gas content in the liquid phase space. Moreover, increasing the inclination angle results in a decrease in the carrying depth of liquid in the vapor phase, but enhances gas–liquid mixing and increases the gas-carrying depth in the liquid phase. Taking into consideration the dual effects of slug dissipation in the inlet pipe and carrying capacity of gas/liquid spaces in the cylinder, the optimal expanding diameter ratio and inclination angle values can be determined.     

横纹管强化吸收器的传热传质实验研究

在吸收式热泵的吸收器中,利用LiBr水溶液为工质,对横纹管强化管外降膜吸收过程进行了研究。实验结果表明:影响横纹管传热强化的主要因素为LiBr水溶液喷淋密度、横纹管结构参数节距和槽深,各个因素对强化效果影响不同;与光管相比,横纹管的传热传质效果明显得到了增强,但是不同结构参数节距与槽深的横纹管,其强化传热传质的效果不同。在实验范围内,横纹管强化LiBr溶液吸收水蒸气的传热系数是光管的2.1—3.25倍,传质系数是光管的1.25—1.93倍。     

Shape optimization of a micromixer with staggered herringbone groove

Shape optimization of a staggered herringbone groove micromixer using three-dimensional Navier-Stokes analysis has been carried out. The analysis of the degree of mixing is performed by the calculation of spatial data statistics. The calculation of the variance of the mass fraction at various nodes on a plane in the channel is used to quantify mixing. A numerical optimization technique is applied to optimize the shape of the grooves on a single wall of the channel. Two design variables, namely, the ratio of the groove depth to channel height ratio and the angle of the groove, are selected for optimization. A mixing index is used as the objective function. The results of the optimization show that the mixing is very sensitive to the shape of the groove which can be used in controlling the mixing in microdevices. The mixing is affected by the depth of the groove much more than the angle of the groove.     

喷嘴雾化特性及脱硫废水蒸发数值模拟

利用相位多普勒粒度分析仪（PDA）实验台测量了双流体喷嘴出口速度与粒径分布,利用得到的速度与粒径数据对江苏某生物质电厂进行小水量脱硫废水蒸发的数值模拟,着重研究了液滴粒径以及烟气中水蒸气的体积分数对液滴蒸发过程的影响。PDA实验结果表明,该双流体喷嘴在特定气液比条件下出口粒径均小于100μm。应用离散相模型与随机轨道模型,利用Rosin-Rammler分布模拟喷雾液滴分布范围（0～100μm）。模拟结果表明,粒径低于100μm的液滴能够完全蒸发,液滴粒径越小,完全蒸发时间越短,液滴经历的平稳吸热时间越短。随着粒径的增加,液滴完全蒸发时间增幅变大。随着烟气中水蒸气体积分数增加,液滴蒸发速率变缓,液滴开始蒸发的时间延长,且体积分数越大,出口未蒸发完全的液滴直径越大,但出口液滴粒径增大的幅度在减小。     

Flow distribution in spiral mandrel dies

An analysis of flow of a power law fluid in a spiral mandrel die is presented. The analysis is applied to study the effect of various die design parameters on the flow distribution at the end of the spiral mandrel section. Three variables that have a very strong effect on the flow distribution are the number of grooves, the initial clearance, and the groove helix angle. The distribution is improved by increasing the number of grooves, by using a non-zero initial clearance, and a relatively small helix angle. Two more variables that have a significant effect on the flow distribution are the taper angle and the initial groove depth. The optimum taper angle was found to be between 1 and 3 degrees. The distribution uniformity improves with the initial groove depth, while the pressure drop reduces at the same time.     

新型气液逆流撞击洗涤喷嘴的优化

针对一种新型气液逆流撞击式洗涤喷嘴,通过冷模实验,采用溶氧法考察了不同结构喷嘴的气液两相传质性能。结合解析率及流型变化,考察了喷嘴出口直径、切向进液口倾角、旋流室收敛段锥角、切向进液口直径、喷口长度5个参数对传质的影响,确定了优选喷嘴的结构尺寸,分析了该优选喷嘴在不同操作条件下(气速、表观液气比和轴切比)的传质效果。结果表明,优选喷嘴在轴切比为0.4~0.6且气速较高时传质效果较好。