Leakage and Stiffness Characteristics of Bionic Cluster Spiral Groove Dry Gas Seal

Spiral groove dry gas seal(S?DGS), the most widely used DGS in the world, encounters the problem of high leakage rate and inferior film stability when used in high?speed machinery equipment, which could not be well solved by optimization of geometrical parameters and molded line of spiral groove. A new type of bionic cluster spiral groove DGS(CS?DGS) is proved to have superior film stability than S?DGS at the condition of high?speed and low?pressure numerically. A bionic CS?DGS is experimentally investigated and compared with common S?DGS in order to provide evidence for theoretical study. The film thickness and leakage rate of both bionic spiral groove and common spiral groove DGS are measured and compared with each other and with theoretical values under different closing force at the condition of static pressure, high?speed and low?pressure, and the film stiffness and stiffness?leakage ratio of these two face seals are derived by the relationship between closing force and film thickness at the steady state. Experimental results agree well with the theory that the leakage and stiffness of bionic CS?DGS are superior to that of common S?DGS under the condition of high?speed and low?pressure, with the decreasing amplitude of 20% to 40% and the growth amplitude of 20%, respectively. The opening performance and stiffness characteristics of bionic CS?DGS are inferior to that of common S?DGS when rotation speed equals to 0 r/min. The proposed research provides a new method to measure the axis film stiffness of DGS, and validates the superior performance of bionic CS?DGS at the condition of high?speed and low?pressure experimentally.

Influence Analysis of Secondary O-ring Seals in Dynamic Behavior of Spiral Groove Gas Face Seals

The current research on secondary O-ring seals used in mechanical seals has begun to focus on their dynamic properties. However, detailed analysis of the dynamic properties of O-ring seals in spiral groove gas face seals is lacking. In particular a transient study and a difference analysis of steady-state and transient performance are imperative. In this paper, a case study is performed to gauge the effect of secondary O-ring seals on the dynamic behavior（steady-state performance and transient performance） of face seals. A numerical finite element method（FEM） model is developed for the dynamic analysis of spiral groove gas face seals with a flexibly mounted stator in the axial and angular modes. The rotor tilt angle, static stator tilt angle and O-ring damping are selected to investigate the effect of O-ring seals on face seals during stable running operation. The results show that the angular factor can be ignored to save time in the simulation under small damping or undamped conditions. However, large O-ring damping has an enormous effect on the angular phase difference of mated rings, affecting the steady-state performance of face seals and largely increasing the possibility of face contact that reduces the service life of face seals. A pressure drop fluctuation is carried out to analyze the effect of O-ring seals on the transient performance of face seals. The results show that face seals could remain stable without support stiffness and O-ring damping during normal stable operation but may enter a large-leakage state when confronting instantaneous fluctuations. The oscillation-amplitude shortening effect of O-ring damping on the axial mode is much greater than that on the angular modes and O-ring damping prefers to cater for axial motion at the cost of angular motion. This research proposes a detailed dynamic-property study of O-ring seals in spiral groove gas face seals, to assist in the design of face seals.

Numerical Analysis of a Spiral-groove Dry-gas Seal Considering Micro-scale Effects

A dry-gas seal system is a non-contact seal technology that is widely used in different industrial applications.Spiral-groove dry-gas seal utilizes fluid dynamic pressure effects to realize the seal and lubrication processes,while forming a high pressure gas film between two sealing faces due to the deceleration of the gas pumped in or out.There is little research into the effects and the influence on seal performance,if the grooves and the gas film are at the micro-scale.This paper investigates the micro-scale effects on spiral-groove dry-gas seal performance in a numerical solution of a corrected Reynolds equation.The Reynolds equation is discretized by means of the finite difference method with the second order scheme and solved by the successive-over-relaxation（SOR） iterative method.The Knudsen number of the flow in the sealing gas film is changed from 0.005 to 0.120 with a variation of film depth and sealing pressure.The numerical results show that the average pressure in the gas film and the sealed gas leakage increase due to micro-scale effects.The open force is enlarged,while the gas film stiffness is significantly decreased due to micro-scale effects.The friction torque and power consumption remain constant,even in low sealing pressure and spin speed conditions.In this paper,the seal performance at different rotor face spin speeds is also described.The proposed research clarifies the micro-scale effects in a spiral-groove dry-gas seal and their influence on seal performance,which is expected to be useful for the improvement of the design of dry-gas seal systems operating in the slip flow regime.

Flow Dynamics of a Spiral-groove Dry-gas Seal

The dry-gas seal has been widely used in different industries. With increased spin speed of the rotator shaft, turbulence occurs in the gas film between the stator and rotor seal faces. For the micro-scale flow in the gas film and grooves, turbulence can change the pressure distribution of the gas film. Hence, the seal performance is influenced. However, turbulence effects and methods for their evaluation are not considered in the existing industrial designs of dry-gas seal. The present paper numerically obtains the turbulent flow fields of a spiral-groove dry-gas seal to analyze turbulence effects on seal performance. The direct numerical simulation （DNS） and Reynolds-averaged Navier-Stokes （RANS） methods are utilized to predict the velocity field properties in the grooves and gas film. The key performance parameter, open force, is obtained by integrating the pressure distribution, and the obtained result is in good agreement with the experimental data of other researchers. Very large velocity gradients are found in the sealing gas film because of the geometrical effects of the grooves. Considering turbulence effects, the calculation results show that both the gas film pressure and open force decrease. The RANS method underestimates the performance, compared with the DNS. The solution of the conventional Reynolds lubrication equation without turbulence effects suffers from significant calculation errors and a small application scope. The present study helps elucidate the physical mechanism of the hydrodynamic effects of grooves for improving and optimizing the industrial design or seal face pattern of a dry-gas seal.

Dynamic Coupling Correlation of Gas Film in Dry Gas Seal with Spiral Groove

In working state, the dynamic performance of dry gas seal, generated by the rotating end face with spiral grooves, is determined by the open force of gas film and leakage flow rate. Generally, the open force and the leakage flow rate can be obtained by finite element method, computational fluid dynamics method and experimental measurement method. However, it will take much time to carry out the above measurements and calculations. In this paper, the approximate model of parallel grooves based on the narrow groove theory is used to establish the dynamic equations of the gas film for the purpose of obtaining the dynamic parameters of gas film. The nonlinear differential equations of gas film model are solved by Runge-Kutta method and shooting method. The numerical values of the pressure profiles, leakage flux and opening force on the seal surface are integrated, and then compared to experimental data for the reliability of the numerical simulation. The results show that the numerical simulation curves are in good agreement with experimental values. Furthermore, the opening force and the leakage flux are proved to be strongly correlated with the operating parameters. Then, the function-coupling method is introduced to analyze the numerical results to obtain the correlation formulae of the opening force and leakage flux respectively with the operating parameters, i.e., the inlet pressure and the rotating speed. This study intends to provide an effective way to predict the aerodynamic performance for designing and optimizing the groove styles in dry gas seal rapidly and accurately.

An Improved Design of Spiral Groove Mechanical Seal

The coupling effect among the flow of fluid film, the frictional heat of fluid film and the thermal deformation of sealing rings is inherent in mechanical seals. The frictional heat transfer analysis was carded out to optimize 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 decrease 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.

Research on the Performance of Supercritical CO_2 Dry Gas Seal with Different Deep Spiral Groove

The performance of supercritical CO_2(SCO_2) dry gas seal(DGS) with different deep spiral groove is investigated with the thermal-fluid-solid coupling method. The performance parameters of DGSs with five different kinds of grooves are obtained. The influence of inlet temperature, inlet pressure, velocity and film thickness on performance is analyzed compared with air DGS. The average film pressure, open force and leakage decrease while the average face temperature and flow velocity increase as the spiral groove number increases. The average film pressure, average face temperature, open force and leakage of DGS with radial different deep groove are higher than those of DGS with circumferential different deep groove respectively under the same spiral groove number while the average flow velocity is the opposite. SCO_2 DGS can generate larger average film pressure, open force and leakage with lower average face temperature than air DGS. SCO_2 DGS could maintain better sealing performance despite larger leakage with the variations of inlet temperature, inlet pressure, velocity and film thickness. The variables hold a more remarkable influence on SCO_2 DGS compared with air DGS.

Performance comparison and parametric study on spiral groove gas film face seals

Several spiral groove gas film face seals (SGFS) with different layouts are compared quantitatively to analyze their merits and faults and application behaviors. In addition, a parametric study on downstream mode SGFS is conducted to determine its optimal parameters under certain working conditions. In tne computation of gas film pressure on the face, finite element method (FEM) is applied to adapt to complicated geometrical boundary.

A Comparative Study on the Performance of Typical Types of Bionic Groove Dry Gas Seal based on Bird Wing

A series of bionic grooves based on bird wing, such as cluster spiral groove, multi-array spiral groove and flow-split spiral groove, are introduced to improve the film stiffness and sealing properties of dry gas seal. A theoretical model solved with Finite Difference Method （FMD） is developed to study the static sealing performance, such as film stiffness and leakage rate of these bionic groove dry gas seals. Then, a performance comparative study between the bionic groove dry gas seals and common spiral groove dry gas seal with different groove geometry parameters such as groove depth ratio, spiral angle and micro groove number under different average linear velocity at seal ring face and seal pressure is carried out. The closing force, film thickness and leakage rate of dry gas seals with bionic grooves and common spiral groove are measured experimentally. Results show that cluster spiral groove and multi-array spiral groove dry gas seals have superiority in the film stiffness and stiffness-leakage ratio compared with common spiral groove under the condition of high-speed and low-pressure, while flow-split spiral groove dry gas seal has no obvious advantages of performance. Film stiffness of cluster spiral groove dry gas seal and stiffness-leakage ratio of multi-array spiral groove dry gas are 20% and 50% larger than that of common spiral groove dry gas seal, respectively, which are verified by the experimental results.

Optimization design of main parameters for double spiral grooves face seal

The optimization design of the parameters, such as the groove depth, groove number, ratio of the groove width to the land width, and spiral angle of a new kind of double spiral grooves face seal, which works under the condition of high velocity, high sealing pressure and ultra-low temperature, is presented under the assump-tion of fixed closure force by finite element analysis method. The results show that the stiffness of the maximum film can be obtained when the ratio of the groove width to the land width is 0.5 and the spiral angle is about 75 degrees, when the influence of the groove number on the sealing performance is not obvious.

超高速干气密封微织构气膜润滑特性研究

针对航天航空领域,设备超高速、高压运转,干气密封稳定性问题,依据槽型织构优化设计,提出一种槽底微织构螺旋槽干气密封结构,以解决密封在超高速旋转过程中气膜稳定性问题。基于气体润滑理论,建模、划分网格,再导入FLUENT软件对流场进行仿真模拟;改变工况参数和槽型结构参数后,在超高速、高压工况下,相比于普通螺旋槽,槽底微织构螺旋槽干气密封的动压效果有显著提升。结果表明,槽深h_(g)=6μm,膜厚h_(0)=2μm,微织构槽深δ=2μm、微织构槽宽取3.97 mm,微织构槽位于螺旋槽底中间位置时,槽底微织构螺旋槽相比于普通螺旋槽可产生明显的动压效应。

高速深螺旋槽机械密封端面环形槽降温传热机理分析

间隙内流体黏性生热量大、端面温升高是机械密封在高速工况下存在的关键共性问题之一,密封端面型槽将对跨尺度间隙内流体传热产生重要的影响。既有研究发现,静环内径侧开设环形槽可有效减小密封端面温升,为深入研究其传热过程及降温作用机理,应用ANSYS Fluent软件建立了深环形槽–深螺旋槽复合式端面构型(ASG)与经典深螺旋槽端面构型(SG)的热流体动力润滑(THD)模型,并在湍流计算模型下对比分析环形槽的传热过程,揭示其降温作用机理,讨论其几何参数对机械密封性能及降温效果的影响规律。结果表明:密封端面内径侧环形槽区因液膜较厚、流体剪切作用较小,润滑流体黏性产热量显著减小,从而有效降低了润滑液膜及密封端面温度;且环形槽槽深、槽宽的适当增加可强化其降温作用,最高达15 K,即温升下降约33%。此外,环形槽的降温作用导致流体黏度损失减小,故深环形槽–深螺旋槽复合式端面构型的密封承载性能与摩擦学性能相比经典深螺旋槽端面构型均有所提升。环形槽使密封环内径侧径向压力梯度增大,密封泄漏率有所增加,单位时间内泄漏流体带走了更多的黏性热量,加之环形槽的开设增加了内径侧高温流体与静环的对流换热面积,均有助于降温。上述结构及环形槽可有效降低润滑液膜与密封端面温升,增加液膜汽化裕度,对机械密封的高速化具有显著的工程意义。

基于湍流模型的螺旋槽机械密封端面流动特性分析

为了研究高转速液膜润滑螺旋槽机械密封湍流流动特性,基于k-ω湍流模型,计算了密封端面液膜相对速度、压力与湍动能分布,并分析了不同转速与膜厚下密封开启力、泄漏率与端面各流动熵产损失占比。结果表明:槽区位置流体速度小,密封堰区流体速度大;液膜压力分布呈周期性,在螺旋槽背面前1/2流向位置处产生了空化;螺旋槽入口湍动能较大,在螺旋槽深度方向上,越靠近密封动环螺旋槽底壁面,流体湍动能越大;流体膜区域总熵产损失明显大于螺旋槽区域,总壁面熵产损失占比≥60%,总湍流流动损失占比≥30%;随着转速增加,开启力与泄漏率增大,壁面熵产损失增加,直接熵产损失降低,当转速≥10000 r/min时,湍流与脉动熵产损失相对稳定,占比35.64%~37.24%;随着膜厚增加,开启力降低,泄漏率增大,壁面熵产损失先增大后减小再增大,直接熵产损失降低,当膜厚≥4μm时,湍流与脉动熵产损失相对稳定,占比40.26%~42.15%。研究结果可为高转速低能耗机械密封结构设计提供理论指导。

磁流体润滑螺旋槽机械密封中的热流固耦合分析

为了研究磁流体润滑螺旋槽机械密封中的热流固耦合效应,利用ANSYS Workbench软件计算了磁流体膜的压力分布、温度分布和动环的变形量,分析了电流强度、转速和磁性颗粒体积分数对磁流体膜压力、温度和动环变形的影响。结果表明:随着电流强度、转速和磁性颗粒体积分数的升高,磁流体膜的动压、温度和密封环的热变形都增大;内径处的磁流体温度最高但压力最低,磁流体基液易汽化;动环的压力变形远小于热变形;磁流体膜的压力、磁流体膜温度的数值解大于试验值和解析值,其主要原因在于数值解考虑了密封堰和离心力对磁流体膜的影响。

润滑液膜在热力耦合下对螺旋槽密封环变形的影响

以螺旋槽机械密封的动静环为研究对象,首先在Solidworks建立三维密封环模型,然后将其导入ANSYS-Workbench的Static Structural场进行热-力耦合模拟计算,研究两环在液膜力与环境热共同耦合作用下的变形情况。结果表明:动环端面由于微沟槽存在结构不连续,应力集中明显,槽根径区域的应力较大;静环端面结构连续,中径处没有应力集中现象,内外径边缘由于强制约束以及接触应力的作用,致使应力较大。动静环的变形量均随压力的增大线性增大,密封环材料始终处在线弹性阶段,材料对热效应不敏感。此时,应力引起的变形起主导作用。

煤层气压缩机干气密封仿真实验研究

为探究煤层气压缩机干气密封结构可能的优化路径,以螺旋槽型干气密封为例,在建立干气密封结构仿真模型的基础上,对该结构的压力分布进行分析,基于压力分布结果,进一步针对设备主轴转速、螺旋角度和螺旋槽数量三项主要参数对干气密封结构密封性能的影响开展仿真分析,并据分析结果提出干气密封结构设计与优化的相关建议,以期为今后的研究工作提供参考与借鉴。

螺旋槽端面干气密封的参数研究

螺旋槽干气密封试验分析了干气密封螺旋槽几何参数对开启力、功耗、泄漏率和气膜刚度的影响 ,并通过理论计算对试验数据给予了验证。理论计算和试验结果的对比表明了试验数据的可靠性。整体来讲 ,在其他参数固定的条件下 ,槽深比、螺旋角对密封性能的影响较为突出 ,而槽数、密封坝宽度比、槽台宽比、压力比对密封性能的影响相对较弱。最后给出密封结构和试验条件下的最优几何参数取值范围 (12 <Ng<18,14° <β <16° ,0 4 <αg<0 6 ,0 3<l<0 5 ,1 6 <δ<1 8,10 <Pr<2 0 )。

螺旋槽干气密封润滑气膜角向涡动的稳定性分析

螺旋槽干气密封操作的稳定性和可靠性与其槽形参数密切相关,优化槽形参数一直是该领域研究的热点。应用PH线性化方法及变分运算干气密封螺旋槽内瞬态微尺度流动场的非线性雷诺方程,得到了气膜角向涡动刚度的解析式。继而利用复数转换和迭代法对稳态下气膜边值问题进行求解,求得了气膜涡动刚度的近似解析解。通过动态稳定性分析,获得了不同介质粘度、压力和转速下稳定性最佳的螺旋角数值。研究结果表明:随介质压力和转速增大,气膜涡动刚度越大,稳定性越好。

带内环槽的螺旋槽干式气体端面密封的静压性能

针对现场使用的带内环槽的螺旋槽干式气体端面密封,建立了用于预测其端面气膜压力的等温可压缩流二维雷诺方程,在只考虑静压效应的条件下应用有限元法计算了端面开启力、泄漏率、气膜刚度和刚漏比等密封性能参数,并与典型螺旋槽干式气体端面密封(S-DGS)进行了比较.结果表明:与S-DGS相比,前者具有更好的稳定性、润滑性能和开启特性.以获得最大刚漏比为优化原则,综合考虑密封的稳定性、密封性和开启特性,获得了带内环槽S-DGS在静压作用下的端面规则微槽几何参数的优选值,研究结果对有关密封的设计与选用具有指导意义.

表面粗糙度对螺旋槽干式气体端面密封性能预测与结构优化的影响

将螺旋槽干式气体端面密封(S-DGS)的粗糙表面分成软环端表面、硬环端面开槽底面与非开槽表面3个区域,建立粗糙表面S-DGS性能的有限元分析理论模型,采用该模型研究3个区域表面粗糙度对S-DGS性能参数和端面几何结构参数优化的影响.结果表明:在相同工况和表面综合均方根差的条件下,粗糙表面S-DGS的开启力、气膜刚度和摩擦扭矩均大于光滑表面S-DGS,而泄漏量较小;在有关标准范围之内,硬环端面槽底面和软环端面的表面粗糙度对S-DGS的性能参数预测值产生较大影响,而硬环端面表面粗糙度的影响可以忽略;表面粗糙度对S-DGS端面几何结构参数的优化值没有影响.研究结果对S-DGS性能的正确预测和结构优化设计以及密封的修复工作具有重要的指导意义.