Seal Groove Research Articles

Gas Seal Performance and Start up Condition Enhancing with Different Seal Groove Geometries

New dry gas seal “DGS” groove geometry has been developed, using a verified three dimensional simulations. The effect of the various groove profiles; standard spiral, tapered-spiral, spiral with an annulus and tapered-spiral with an annulus were studied at wide range of operating speed. The results indicate that, tapered type spiral groove causes a reduction in opening force and in the leakage rate. In addition, increasing the taper angle reduces the temperature distribution inside the gas film and reduces the thermal stresses on the seal mating rings. The combined use of annuals and taper spiral groove decrease the leakage rate for spiral DGS with annular groove only. The final optimized spiral tapered seal with annuals reduces the leakage rate by 18.5% from standard seal, ensures uniform pressure distribution and hydrostatic lift at low speeds, resulting in low torque and reliable operating at start-up condition.

Improvement and experimental research of CO2 two-rolling piston expander

Owing to the poor performance of the previous CO2 two-rolling piston expander prototype, improvements were made to increase its efficiency. The improvement measures included increasing the expansion ratio by minimizing the size of the intermediate channel and adopting some sealing methods to block the leakages, such as integrating the intermediate plate and filling O-rings in the seal grooves of the end covers. To reduce the leakage and irreversible losses, lubrication of the expander was investigated as a measure. The improved expander was tested in the CO2 water-to-water heat pump system. The experimental results showed that the revised expander had a much higher efficiency compared to the primary one, reaching a maximum of 77% at the revolution speed of 867 rpm, and a maximum recovered expansion work of 242 W at the revolution speed of 770 rpm. However, further improvement of the expander is necessary because the measured parameters of the prototype do not yet approach the design values.

Study of magnetic abrasive finishing in seal ring groove surface operations

Because the seal ring groove is used in conjunction with rubber seals, it needs a higher surface quality. Traditional finishing methods are difficult to implement on its bottom and side synchronization finishing because of the special structure of the seal ring groove, and the finishing efficiency is low. To resolve these problems, a magnetic abrasive finishing (MAF) process has been created. As a non-traditional precise machining process, MAF has many advantages. By utilizing the magnet to generate a magnetic field, the magnetic abrasive particles (MAPs) are bound and formed as a flexible magnetic abrasive brush (MAB) for pressing and finishing the workpiece. The external seal ring groove surface can be polished synchronously in the MAF mechanism. Hence, three types of flux paths with the magnet poles in 45°, 90°, and 180° layout were simulated and compared by ANSYS software. The magnet poles’ arrangement and the magnetic flux density were confirmed using measuring equipment. The synchronous MAF device was developed based on the simulation and detection results. The viscosity of lubricant (the percentage between lubricant and water), the spindle speed, the gap between magnet poles and the bottom of the ring groove (gap 1), and the gap between magnet poles and the sides of the ring groove (gap 2) are selected as study objects. Furthermore, the experimental data has been collected using the orthogonal experimental design, and the experimental data on process parameters have been analyzed to determine the optimal conditions. The finished surface of the ring groove about the bottom or side surface has been detected based on the optimal conditions, and it has been found that the surface roughness from initial Ra4.3 μm decreased to Ra0.6 μm. The 3D surface topography has become more uniform and smoother. The results revealed that the MAF can provide a highly efficient way of obtaining high quality and can operate the external seal ring groove surface synchronously.

Influence of Geometry on Vortex Configuration and Dimension in LRE Turbopump Labyrinth Seal

Rotor seals are the most important element of turbomachine. Seals characteristics determine efficiency, reliability and lifetime of turbopump. Labyrinth seals have lower flow coefficient compared to gap seals. However they are used not so often because under certain conditions they may cause of rotor dynamic instability. Vortex in seal grooves are one of the causes of rotor oscillations. And their number, configuration, dimensions and velocity directly depend on groove geometry. The paper describes the modeling of the flow in labyrinth seal using ANSYS CFX, the influence of groove geometry on vortex number, dimension and configuration.

Capabilities of Theoretical and Empirical Methods of Calculating the Parameters of Viscous Flow of a Medium in Cylindrical Annular Channels

Questions related to the selection and application of theoretical or empirical methods for the calculation of the parameters of the groove seals of shafts widely used in pumps and compressors are considered. A theoretical method of calculation through the compilation and solution of a system of equations that describe the flow of a medium in the channel of a groove seal is successfully applied for the case of a laminar regime of flow of a medium in a channel. It is not possible to describe such flow by means of a closed system of equations in the case of a turbulent regime of flow of a medium in the channel of a groove seal. The new theoretical method of determining the unknown parameters of the turbulent flow of a medium in annular groove seals, which is related to the solution of the Martsinkovskii equation, may serve only as a tool for studying the nature of the processes that occur in a groove seal. Thus, empirical methods based on Bernoulli’s equation and the data of experimental investigations are still the only reliable tool for calculating the characteristics of groove seals in the case of a turbulent regime of flow of a medium.

마모 실 홈 형상이 펌프 성능에 미치는 영향에 관한 실험적 연구

마모 실 홈 형상이 펌프 성능에 미치는 영향에 관한 실험적 연구

Correlational Research of Bionics Design of Dry Gas Face Seal Groove

Based on statistical method and gas lubrication theory, the correlation mathematical models of outline constructional feature of a bird wing and face groove feature of a dry gas seal(DGS) are established, and the film pressure controlling equation of a DGS is set up. The membership grades and their calculation expressions used to define face groove geometrical feature of a DGS are presented based on fuzzy mathematics, and DGSs are classified according to the membership grades. The gas film pressure control equations are resolved by use of finite difference method, and the gas film stiffness of a DGS is obtained. The correlation between the constructional feature parameters of bird wing outlines and flight speed and the correlation between face groove geometric parameters and operational stability of a DGS at different speeds are comparatively analyzed. Results show that the correlations between the geometric constructional feature parameters of bird wing outlines or face grooves and their flight speeds or operational speeds are in moderate degree. That is to say long wings give a bird stability, and long narrow wings give a bird more stability at high flight speeds, and long grooves give a DGS stability, and long narrow grooves give a DGS more stability at high operational speeds, correspondingly. Results also reveal that the relationship between a bird biological model and a DGS engineering model exists exactly. The feasibility of bionic design of face groove based on the geometric characteristics of bird wing outlines is demonstrated. The important theory basis is provided for the bionic design of a DGS.

Numerical Analysis of General Groove Geometry for Dry Gas Seals

By Changing the key points on the spiral curve, general groove geometry was determined. Considering the simplicity of modeling and analysis, cubic spline function was used to express the general groove profile. By using the boundary fitted coordinate system transformation, irregular computational domain was transferred to regular region; Based on flow conservation principle, finite volume method was applied to discrete compressible Reynolds equation; By the application of Newton-Raphson iteration method for solving algebraic equation, numerical model of general groove dry gas seals was established. When compared sample results with shallow groove theory, the capacity and stiffness of numerical results match well with theoretical ones, verifying the accuracy of novel numerical model. Through analysis of three typical groove seals, spiral groove seal has strongest carrying capacity. Pressure distribution of three groove seals subjects to the law of hydrodynamic pressure effect. And the numerical model established in this paper will offer a general calculate platform for optimization of groove geometry in the future.

Computed Universal Dependence for Determining Leakage of Media Through Groove Seals

The calculation of leakages of liquid and gaseous media through straight-through and non-straight-through groove seals is currently performed using dependences that differ in terms of the composition and form of the representation of the input parameters. In the present article questions related to the use of a generalized universal dependence for calculations of leakages of compressible and incompressible media in the channels of groove and labyrinth seals of shafts that are widely used in pumps, turbines, and compressors are considered. An analysis of the well-known dependences is carried out, a technique for processing the results of studies of leakages for groove seals that differ in terms of the shape of the channels of the seals, and the use of these results in a standardized universal dependence for calculation of leakages is proposed.

Effect of transfer medium on wear rate of groove seals of centrifugal pumps

The effect of various liquids (oil, water) transferred by centrifugal pumps on the wear rate of their groove seals is studied and the findings are analyzed. The transfer medium was shown to significantly influence the wear rate. The liquid effect can be both positive and negative depending on the metal used to make the components of the groove seal. The wear of the groove seal is low if alloys based on copper are used. To the contrary, the wear increases if groove seals are made of steel, which may be due to the specific physicochemical processes.

FEM analysis of magnetorheological fluid seal of circular cooler and its experimental research

Magnetorheological fluid (MRF) exhibits drastic changes in rheological properties adjustable and controllable yield stress under external magnetic field. Based on its specialty, the MRF seal technique is proposed to deal with the air leakage of circular cooler to improve the energy efficiency for the steel industry. MRF is regarded as Bingham fluid with its magnetization vector and magnetic force expressed by mathematical functions. The FEM analysis results show that, under magnetic field, MRF which presents good pressure resistance as a result of its yield stress is in a dynamic equilibrium state in non-magnetic seal groove even with pressure difference, and due to the volume force, it presents unsteady swirl flow obviously at the right- angle edges of the two permanent magnets nearby non-magnetic separator, whereas, due to pressure difference, it shows an obvious flow without magnetic field. In the meantime, according to the experiment, it indicates that the air leakage of circular cooler is solvable effectively with the MRF seal method, and it is also proved that MRF shows controllable yield stress under magnetic field.

Active and Passive Flow Control of Turbomachines

Turbomachines are used in a wide range of applications. Increasing the efficiency and operating range of turbomachines reduces fuel consumption of gas turbine power plants and other applications. Over the years, many attempts have been made to achieve these objectives. e present special issue addresses these goals with special emphasis on active and passive �ow control techniques. is special issue compiles 7 original research articles that describe active and passive �ow control techniques applied to different types of turbomachines. e theme for this special issue is set by J. P. Gostelow et al. ey describe various types of vortices encountered in a transonic turbine nozzle blade passage. Active and passive control of these vortices is essential to improve the performance of turbines. ere are two more papers on control of turbine �ows. e paper by R. Da Soghe et al. describes aerothermal analysis of a turbine casing impingement cooling system. T. Matsunuma and T. Segawa systematically varied the input voltage of plasma actuators to reattach the simulated boundary layer on the suction surface of a turbine at a low Reynolds number. e low-pressure turbine of aircra gas turbine power plants operating at high altitudes operates at low Reynolds numbers. Losses in turbines operating at low Reynolds numbers increase rapidly due to large separation occurring on the suction surfaces of the turbine blades. Many researchers used dielectric barrier discharge (DBD) plasma actuators to actively control �ow separation, tip clearance �ows, and so forth in turbines and other turbomachinery components. e present paper by T. Matsunuma and T. Segawa is a great addition to the available data that addresses the effects of input voltage to plasma actuators on �ow control effectiveness. Two papers describe active and passive �ow control techniques applied to centrifugal compressors. A. Marsan et al. numerically investigated boundary layer suction technique applied to the radial diffuser of a transonic centrifugal compressor. ey had presented an efficient control technique, which used a suction mass �ow rate of 0.1% of global mass �ow to increase the compressor operating range by 40%. T. Hirano et al. experimentally investigated a passive nozzle injection system to control surge and rotating stall in high speed centrifugal compressors. ey demonstrated optimum circumferential position of the injection nozzle. S. Kyparissis and D. Margaris tested impellers with three different leading edge angles to optimize the leading edge angle to reduce cavitation development and enhance the performance of a centrifugal pump. Active and passive �ow control techniques are being extensively investigated in the primary components of turbomachinery. However to further improve the performance of turbomachinery, active and passive �ow control techniques need to be applied to secondary components of turbomachines, such as seals. e last paper of the special issue by M. �hang et al. addresses leakage �ow characteristics of seals used in reactor coolant pumps. ey had numerically shown that helical groove seal controls the leakage along the front surface of the impeller face due to its higher resistance than the circumferential grooved seal. It is hoped that this special issue will provide useful information to wide readership from academia, industry and research establishments and inspire new and more efficient control techniques.

Numerical Simulation of the Flow Field in Circumferential Grooved Liquid Seals

Circumferential grooved liquid seals are utilized inside turbomachinery to provide noncontacting control of internal incompressible fluid leakage. Accurate prediction of the flow field is fundamental in producing robust and efficient designs. To validate the capabilities of the computational fluid dynamics FLUENT for incompressible fluid seal flow, comparisons of velocity parameters are made to the published experimental results and other CFD code for a circumferential grooved liquid seal. This work employs a pressure-based CFD code FLUENT to calculate the flow field in the seal, using four different turbulence models respectively. The velocity contours are compared with experimental values. It shows good overall agreement of the axial, radial, and azimuthal velocities in the through-flow jet, shear layer, and recirculation zone. Quantitative comparisons of velocity profiles at the center of the groove are made to experiment. This study verifies the prediction accuracy of three turbulence models. Various structures were considered to obtain a better understanding of the circumferential grooved liquid flow characteristics. The best groove structure to control leakage was also found within the limited designed seal. This study will provide a useful reference for designing the circumferential grooved liquid seal.

The Rubber O-Ring Seal Structure Simulation Research of Electromagnetic Measurement while Drilling Instrument

The instrument of electromagnetic measurement while drilling （EM-WMD）works in the underground environment. In the case of mechanical structure design, sealing is a key problem that needs to be focused. Based on the application of using the traditional design theory to determine the sealing structure and size, finite element analysis is implemented on the rubber O-ring radial seal structure by using the nonlinear finite element software MSC.Marc. The numerical simulation is processed according to different parameters both of axis and axle sleeve gap value and seal groove fillet radius value, and then both of the influence factors of sealing effect are analyzed. Finally , based on this, the relevant seal structure size is optimized.

Investigations of groove seal wear in centrifugal oil pumps

The paper presents the results of study of the factors affecting the wear rate in groove seal components used for crude oil centrifugal pumps. A test technique is proposed for the groove seal components that forecasts their wear resistance in specified conditions.

A Novel Bulk-Flow Model for Improved Predictions of Force Coefficients in Grooved Oil Seals Operating Eccentrically

Oil seals in centrifugal compressors reduce leakage of the process gas into the support bearings and ambient. Under certain operating conditions of speed and pressure, oil seals lock, becoming a source of hydrodynamic instability due to excessively large cross coupled stiffness coefficients. It is a common practice to machine circumferential grooves, breaking the seal land, to isolate shear flow induced film pressures in contiguous lands, and hence reducing the seal cross coupled stiffnesses. Published tests results for oil seal rings shows that an inner land groove, shallow or deep, does not actually reduce the cross-stiffnesses as much as conventional models predict. In addition, the tested grooved oil seals evidenced large added mass coefficients while predictive models, based on classical lubrication theory, neglect fluid inertia effects. This paper introduces a bulk-flow model for groove oil seals operating eccentrically and its solution via the finite element (FE) method. The analysis relies on an effective groove depth, different from the physical depth, which delimits the upper boundary for the squeeze film flow. Predictions of rotordynamic force coefficients are compared to published experimental force coefficients for a smooth land seal and a seal with a single inner groove with depth equaling 15 times the land clearance. The test data represent operation at 10 krpm and 70 bar supply pressure, and four journal eccentricity ratios (e/c= 0, 0.3, 0.5, 0.7). Predictions from the current model agree with the test data for operation at the lowest eccentricities (e/c= 0.3) with discrepancies increasing at larger journal eccentricities. The new flow model is a significant improvement towards the accurate estimation of grooved seal cross-coupled stiffnesses and added mass coefficients; the latter was previously ignored or largely under predicted.

Leakage Characteristic of Helical Groove Seal Designed in Reactor Coolant Pump

Helical groove seal is designed in reactor coolant pump to control the leakage along the front surface of the impeller face due to its higher resistance than the circumferentially grooved seal. The flow and the friction factors in helical groove seals are predicted by employing a commercial CFD code, FLUENT. The friction factors of the helical groove seals with helix angles varying from 20 deg to 50 deg, at a range of rotational speed and axial Reynolds number, were, respectively, calculated. For the helically grooved stator with the helix angle greater than 20 deg, the leakage shows an upward trend with the helix angle. The circumferentially grooved stator has a lower resistance to leakage than the 20 deg and 30 deg stators. It can be predicated that, for a bigger helix angle, the friction factor increases slightly with an increase in high axial Reynolds number, which arises from the high-pressure operation condition, and the friction factor is generally sensitive to changes in the helix angle in this operation condition. The study lays the theoretical foundation for liquid seal design of reactor coolant pump and future experimental study to account for the high-pressure condition affecting the leakage characteristic.

A Theoretical and Experimental Study on Characteristics of Water-Lubricated Double Spiral–Grooved Seals

The spiral-grooved seal is a prime candidate for application to liquid oxygen (LOX) turbopumps. A theoretical model of double spiral–grooved seals dealing with the viscosity–temperature relation is presented. The effect of operating parameters (rotational speed, supply pressure) and configurative parameters (depth of spiral groove) on the basic static characteristics (opening force, leakage, static friction torque, face temperature, and power loss) of double spiral–grooved seals are examined. Comparisons are presented between measurements and theoretical predications for a narrow spiral-grooved face seal with an average diameter of 100 mm, operating at high speed and using water as a test fluid. The theoretical and experimental results indicate that the temperature on seal faces rises and friction torque increases with the speed and supply pressure, and these increases vary slightly with the depth of the spiral groove. These findings lend great theoretical and experimental insights to the design of face seals applied in liquid engine turbopumps.

Lubrication characteristics of spiral groove liquid seals for use in the carrier of a vane-type external LPG fuel pump

We analyzed the lubrication characteristics of a design-selected spiral groove liquid seal for the critical component, the carrier, of a rotary vane-type fuel pump developed for external installation on fuel tanks for liquid phase LPG (liquefied petroleum gas) injection (LPLi) vehicles, with the aim of fundamentally improving lubrication performance and so protecting the carrier from early frictional wear damage at its suction face. The main reason for selecting a spiral groove pattern was because the viscosity of liquid LPG is very low, comparable to that of air, and current commercial dry gas seals adopting spiral grooves have been successfully employed in completely noncontacting applications. Utilizing the Galerkin finite element lubrication analysis method, a detailed lubrication characteristic analysis of the seal was performed, and lubrication performance optimization was performed by systematic parameter analyses of the design variables. Compared to the initial reference design, the final optimized spiral groove seal design had a groove depth increased by 66.7% and an equilibrium seal clearance increased by 65.3%. Our model also predicted that under a condition of equilibrium between the closing force of the pumping pressure and the seal opening force, the optimally designed carrier spiral groove liquid seal was capable of maintaining a stable lubricating film with sufficient axial stiffness and thereby demonstrated successful noncontact operation; in addition, leakage through the seal was minimal.

FEA and Structural Optimization of Seal Structure of a Leak-Off Pipe Quick Repairing Joint

With the help of FEA software ABAQUS, the seal structure of a leak-off pipe quick repairing joint was simulated and calculated. Different parameters influencing maximum contact stress and shearing stress of sealing face were taken into account. Essential sealing conditions of the leak-off pipe quick repairing joint were simplified, and the optimal structure of seal groove was obtained by orthogonal design. The results of FEA show that the structure could satisfy the sealing requirement of fluid pressure 1.4MPa.