Hydrodynamics and Sonic Flow Transition in Dry Gas Seals

2014 ◽  
Author(s):  
Azam Thatte ◽  
Xiaoqing Zheng
Keyword(s):  
Linear Partial Differential Equation ◽  
Hydrodynamic Pressure ◽  
Secondary Flows ◽  
Operating Conditions ◽  
Operating Pressure ◽  
Spiral Groove ◽  
Local Pressure ◽  
Choked Flow ◽  
Gas Seals ◽  
Film Stiffness

Dry gas seals (DGS) are widely used in turbomachinery applications. They are recently being also recommended for sealing novel super critical CO2 turbomachinery space. However, these seals can render interesting behavior under certain operating conditions which needs to be carefully monitored so that intended level of dynamic characteristics can be achieved. The ability of these seals to maintain low leakage by riding at small clearances makes them an attractive solution where secondary flows need to be minimized. To understand the significance of some of the key design features of these seals, in this work an analysis on a gas lubricated spiral groove dry gas seal is presented. Equations in polar coordinates governing the compressible flow through the DGS gap and a numerical method to solve such non-linear partial differential equation is presented. The resulting sets of equations are solved for hydrodynamic pressure distribution and the axial separation force and the film stiffness at the rotor-stator interface is calculated. A detailed study on key spiral groove features is then performed to investigate the effect of spiral angle, groove depth, groove pitch and dam width ratio on the hydrodynamic pressure generation capacity, film stiffness and hence on overall performance of the DGS. Another important phenomenon that can occur in DGS under high operating pressure is the sonic transition. It is shown that choked flow under such conditions can take place over the dam section of the seal which manifests itself into large local pressure and temperature variations and can result into dynamic instabilities.

Coupled Thermal-Structural-Fluid Numerical Analysis of Gas Lubricated Mechanical Seals

2018 ◽  
Author(s):  
Jingjing Luo ◽  
Hans Josef Dohmen ◽  
Friedrich-Karl Benra
Keyword(s):  
Numerical Analysis ◽  
Hydrodynamic Pressure ◽  
Operating Conditions ◽  
Design Parameters ◽  
Transfer Model ◽  
Operating Pressure ◽  
Mechanical Seals ◽  
Choked Flow ◽  
Leakage Flows ◽  
Mechanical Deformations

With the increase of the operating pressure of gas compressors, the demand for a robust and reliable shaft end sealing solution, namely dry gas seal, has risen. The narrow sealing gap formed between the rotating and the stationary rings, about 2–5 micrometers wide, is subject to the hydrodynamic pressure on sealing surfaces and deflections on both rings due to mechanical forces and thermal loads. In order to estimate the seal performance in terms of film thicknesses, leakage flows and radial tapers, a numerical program which automatically couples the simulation of the pressure field in micro-scale based on the Reynolds equation for compressible fluids, the heat generation and transfer model between the fluid and solids as well as the structural and thermal distortion of both rings, has been developed by the authors to address the mechanical seal problem as a whole system. In this way, the interaction of all arising forces, mechanical deformations and thermal deviations is taken into account in the design process of the seals. The choked flow exit boundary is also taken into considerations for high pressure conditions. The method to solve this interactive problem as a whole is discussed. The paper presents the numerical analysis carried out with various groove parameters, seal geometries and operating conditions. Results are compared and show a good agreement with actual experimental data. Design parameters which have strong influences on the seal performance are as well discussed.

Comparison of the Load-Carrying Performance of Mechanical Gas Seals Textured With Microgrooves and Microdimples

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Liping Shi ◽  
Xiuying Wang ◽  
Xiao Su ◽  
Wei Huang ◽  
Xiaolei Wang
Keyword(s):  
Reynolds Equation ◽  
Hydrodynamic Pressure ◽  
Area Density ◽  
Low Area ◽  
Optimal Load ◽  
High Area ◽  
Load Carrying ◽  
Small Clearance ◽  
Gas Seals ◽  
Film Stiffness

The effects of microgrooves and microdimples on the load-carrying performance of mechanical gas seals are compared in this study. Numerical model based on the Reynolds equation for compressible Newtonian fluid is utilized to investigate the load-carrying performance including the hydrodynamic pressure, the load-carrying force, and gas film stiffness of the gas seals. The results indicate that both microgrooves and microdimples can improve the load-carrying performance of mechanical gas seals, particularly under a small clearance condition. Furthermore, different texture patterns achieve optimal load-carrying performance at different area density, seal clearance, and depth: microgrooves with a low area density can obtain higher load-carrying force and gas film stiffness than the dimple patterns, but with high area density, elliptical dimples yield better load-carrying performance than the groove patterns.

Performance Analyses of the Spiral Groove Dry Gas Seal with Inner Annular Groove

2013 ◽  
Vol 420 ◽  
pp. 51-55 ◽  
Author(s):  
Ying Li ◽  
Peng Yun Song ◽  
Heng Jie Xu
Keyword(s):  
Pressure Control ◽  
Operating Conditions ◽  
Performance Parameters ◽  
Spiral Groove ◽  
Dry Gas Seal ◽  
Sealing Performance ◽  
The Common ◽  
The Difference ◽  
Film Stiffness ◽  
The Given

In order to improve the performance of the spiral groove dry gas seal (S-DGS), the spiral groove dry gas seal with an inner annular groove (AS-DGS) was invented. Based on the narrow groove theory, the sealing performance parameters of the AS-DGS were gained by using approximate analytical method to solve the gas film pressure control equations, and the results were compared with those of the common S-DGS. The results show that, in the given operating conditions, the opening force of AS-DGS is smaller than that of the S-DGS with the difference less than 0.5%, and the film stiffness is larger than that of the common S-DGS with the difference less than 5% in the case of low-speed or high-pressure operation, but the leakage is a little larger.

scholarly journals A comprehensive multi-objective, multi-parameter and multi-condition optimization of a spiral groove in dry gas seals

2020 ◽  
Author(s):  
Jinbo Jiang ◽  
Wenjing Zhao ◽  
Jie Jin ◽  
Jiyun Li ◽  
Xudong Peng
Keyword(s):  
Genetic Algorithm ◽  
Working Conditions ◽  
Optimization Problems ◽  
Geometric Parameters ◽  
The Other ◽  
Operating Efficiency ◽  
Spiral Groove ◽  
Gas Seals ◽  
Film Stiffness ◽  
Dimensional Optimization

Abstract Dry gas seals are widely used in rotating equipment for fluid leakage control and operating efficiency enhancement. Multi-dimensional optimization of geometric parameters of the spiral groove was conducted with considering the comprehensive effect of working conditions, objective functions and the other geometric parameters. Different optimization methods were proposed for solving the multi-dimensional optimization problems. The optimal values of groove width ratio, groove length ratio and spiral angle for the excellent steady performance of spiral grooves under different working conditions were obtained by employing a genetic algorithm and loop iteration optimization method. The performance comparison of two dry gas seals with different geometric parameters was conducted experimentally to verify the effectiveness of numerical results. The results showed that optimal geometric parameters of the spiral groove were significantly influenced by working conditions, objective function and the other geometric parameters. Maximum film stiffness and stiffness-leakage ratio of the spiral groove dry gas seal obtained by genetic algorithm enhanced up to 30% and 45% larger than those obtained by the conventional single factor optimization. The film stiffness and stiffness-leakage ratio were more sensitive to geometric parameters of a spiral groove than that of opening force. The optimization results obtained in this paper provide a theoretical and experimental reference for the design of dry gas seals in different working conditions to meet various sealing performance requirements.

Effect of operating conditions on rejection of anionic pollutants in the water environment by nanofiltration especially in very low pressure range

1996 ◽  
Vol 34 (9) ◽  
pp. 149-156 ◽  
Author(s):  
C. Ratanatamskul ◽  
K. Yamamoto ◽  
T. Urase ◽  
S. Ohgaki
Keyword(s):  
Water Environment ◽  
Chloride Ions ◽  
Operating Conditions ◽  
Transmembrane Pressure ◽  
Operating Pressure ◽  
Nanofiltration Membranes ◽  
Single Solution ◽  
Crossflow Velocity ◽  
Membrane Type ◽  
New Generation

The recent development of new generation LPRO or nanofiltration membranes have received attraction for application in the field of wastewater and water treatment through an increasingly stringent regulation for drinking purpose and water reclamation. In this research, the application on treatment of anionic pollutants (nitrate, nitrite, phosphate, sulfate and chloride ions) have been investigated as functions of transmembrane pressure, crossflow velocity and temperature under very much lower pressure operation range (0.49 to 0.03 MPa) than any other previous research used to do. Negative rejection was also observed under very much low range of operating pressure in the case of membrane type NTR-7250. Moreover, the extended Nernst-Planck model was used for analysis of the experimental data of the rejection of nitrate, nitrite and chloride ions in single solution by considering effective charged density of the membranes.

Numerical Investigation on the Leakage and Static Stability Characteristics of Pocket Damper Seals at High Eccentricity Ratios

2017 ◽  
Vol 140 (4) ◽  
Author(s):  
Zhigang Li ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Static Stability ◽  
Operating Conditions ◽  
Eccentricity Ratio ◽  
Static Stiffness ◽  
Flow Conditions ◽  
Experiment Data ◽  
High Eccentricity ◽  
Stiffness Coefficients ◽  
Direct Stiffness ◽  
Gas Seals

Annular gas seals for compressors and turbines are designed to operate in a nominally centered position in which the rotor and stator are at concentric condition, but due to the rotor–stator misalignment or flexible rotor deflection, many seals usually are suffering from high eccentricity. The centering force (represented by static stiffness) of an annular gas seal at eccentricity plays a pronounced effect on the rotordynamic and static stability behavior of rotating machines. The paper deals with the leakage and static stability behavior of a fully partitioned pocket damper seal (FPDS) at high eccentricity ratios. The present work introduces a novel mesh generation method for the full 360 deg mesh of annular gas seals with eccentric rotor, based on the mesh deformation technique. The leakage flow rates, static fluid-induced response forces, and static stiffness coefficients were solved for the FPDS at high eccentricity ratios, using the steady Reynolds-averaged Navier–Stokes solution approach. The calculations were performed at typical operating conditions including seven rotor eccentricity ratios up to 0.9 for four rotational speeds (0 rpm, 7000 rpm, 11,000 rpm, and 15,000 rpm) including the nonrotating condition, three pressure ratios (0.17, 0.35, and 0.50) including the choked exit flow condition, two inlet preswirl velocities (0 m/s, 60 m/s). The numerical method was validated by comparisons to the experiment data of static stiffness coefficients at choked exit flow conditions. The static direct and cross-coupling stiffness coefficients are in reasonable agreement with the experiment data. An interesting observation stemming from these numerical results is that the FPDS has a positive direct stiffness as long as it operates at subsonic exit flow conditions; no matter the eccentricity ratio and rotational speed are high or low. For the choked exit condition, the FPDS shows negative direct stiffness at low eccentricity ratio and then crosses over to positive value at the crossover eccentricity ratio (0.5–0.7) following a trend indicative of a parabola. Therefore, the negative static direct stiffness is limited to the specific operating conditions: choked exit flow condition and low eccentricity ratio less than the crossover eccentricity ratio, where the pocket damper seal (PDS) would be statically unstable.

Compressible Flowfield Characteristics of Butterfly Valves

1989 ◽  
Vol 111 (4) ◽  
pp. 400-407 ◽  
Author(s):  
M. J. Morris ◽  
J. C. Dutton
Keyword(s):  
Flow Separation ◽  
Pressure Ratio ◽  
Disk Surface ◽  
Surface Flow ◽  
Operating Conditions ◽  
Local Geometry ◽  
Operating Pressure ◽  
Butterfly Valve ◽  
Pressure Distributions ◽  
Flow Separation And Reattachment

The results of an experimental investigation into the flowfield characteristics of butterfly valves under compressible flow operating conditions are reported. The experimental results include Schlieren and surface flow visualizations and flowfield static pressure distributions. Two valve disk shapes have been studied in a planar, two-dimensional test section: a generic biconvex circular arc profile and the midplane cross-section of a prototype butterfly valve. The valve disk angle and operating pressure ratio have also been varied in these experiments. The results demonstrate that under certain conditions of operation the butterfly valve flowfield can be extremely complex with oblique shock waves, expansion fans, and regions of flow separation and reattachment. In addition, the sensitivity of the valve disk surface pressure distributions to the local geometry near the leading and trailing edges and the relation of the aerodynamic torque to flow separation and reattachment on the disk are shown.

Designing CO2 Transmission Pipelines Without Crack Arrestors

2010 ◽  
Author(s):  
Graeme G. King ◽  
Satish Kumar
Keyword(s):  
Wall Thickness ◽  
Carbon Capture ◽  
Power Plants ◽  
Oil And Gas ◽  
Cost Optimization ◽  
Operating Conditions ◽  
Operating Pressure ◽  
Design Work ◽  
Industrial Facilities ◽  
Pipeline Network

Masdar is developing several carbon capture projects from power plants, smelters, steel works, industrial facilities and oil and gas processing plants in Abu Dhabi in a phased series of projects. Captured CO2 will be transported in a new national CO2 pipeline network with a nominal capacity of 20×106 T/y to oil reservoirs where it will be injected for reservoir management and sequestration. Design of the pipeline network considered three primary factors in the selection of wall thickness and toughness, (a) steady and transient operating conditions, (b) prevention of longitudinal ductile fractures and (c) optimization of total project owning and operating costs. The paper explains how the three factors affect wall thickness and toughness. It sets out code requirements that must be satisfied when choosing wall thickness and gives details of how to calculate toughness to prevent propagation of long ductile fracture in CO2 pipelines. It then uses cost optimization to resolve contention between the different requirements and arrive at a safe and economical pipeline design. The design work selected a design pressure of 24.5 MPa, well above the critical point for CO2 and much higher than is normally seen in conventional oil and gas pipelines. Despite its high operating pressure, the proposed network will be one of the safest pipeline systems in the world today.

Morphological Adaptation for Speed Control of Pipeline Inspection Gauges MC-PIG

2021 ◽  
Author(s):  
Sujet Phodapol ◽  
Tachadol Suthisomboon ◽  
Pong Kosanunt ◽  
Ravipas Vongasemjit ◽  
Petch Janbanjong ◽  
...  
Keyword(s):  
Fluid Velocity ◽  
Operating Conditions ◽  
Pi Control ◽  
Operating Pressure ◽  
Acceptable Error ◽  
Valve Unit ◽  
Pipeline Inspection ◽  
Flow Adjustment ◽  
Valve Angle ◽  
Moving Speed

Abstract Passive and active hybrid pipeline inspection gauges (PIGs) have been used for in-pipe inspection. While a passive PIG cannot control its speed, the hybrid version can achieve this by using an integrated valve specifically designed and embedded in the PIG. This study proposes a generic new method for speed adaptation in PIGs (called MC-PIG) by introducing a generic, modular, controllable, external valve unit add-on for attaching to existing conventional (passive) PIGs with minimal change. The MC-PIG method is based on the principle of morphological computation with closed-loop control. It is achieved by regulating/computing the PIG's morphology (i.e., a modular rotary valve unit add-on) to control bypass flow. Adjustment of the valve angle can affect the flow rate passing through the PIG, resulting in speed regulation ability. We use numerical simulation with computational fluid dynamics (CFD) to investigate and analyze the speed of a simulated PIG with the valve unit adjusted by proportional-integral (PI) control under various in-pipe pressure conditions. Our simulation experiments are performed under different operating conditions in three pipe sizes (16″, 18″, and 22″ in diameter) to manifest the speed adaptation of the PIG with the modular valve unit add-on and PI control. Our results show that the PIG can effectively perform real-time adaptation (i.e., adjusting its valve angle) to maintain the desired speed. The valve design can be adjusted from 5 degrees (closed valve, resulting in high moving speed) to a maximum of 45 degrees (fully open valve, resulting in low moving speed). The speed of the PIG can be regulated from 0.59 m/s to 3.88 m/s in a 16″ pipe at 4.38 m/s (in-pipe fluid velocity), 2500 kPa (operating pressure), and 62 °C (operating temperature). Finally, the MC-PIG method is validated using a 3D-printed prototype in a 6″ pipe. Through the investigation, we observed that two factors influence speed adaptation; the pressure drop coefficient and friction of the PIG and pipeline. In conclusion, the results from the simulation and prototype show close characteristics with an acceptable error.

In-Field Application of Steel Strip Reinforcement for Pipeline External Rehabilitation

2010 ◽  
Author(s):  
Nicholas J. Venero ◽  
Tim J. M. Bond ◽  
Raymond N. Burke ◽  
David J. Miles
Keyword(s):  
Steel Strip ◽  
New Technology ◽  
High Strength ◽  
Field Application ◽  
Operating Conditions ◽  
Operating Pressure ◽  
Precise Control ◽  
Ultra High Strength Steel ◽  
Structural Adhesive ◽  
Pipeline Design

A new technology for external rehabilitation of pipelines, known as XHab™, has been developed. This method involves wrapping multiple layers of ultra-high strength steel (UHSS) strip in a helical form continuously over an extended length of pipeline using a dedicated forming and wrapping machine. The reinforcement afforded by the strip can be used to bring a defective section of pipe (e.g. externally corroded or dented) back to its original allowable operating conditions, or even to increase the allowable operating pressure if the desired operating conditions exceed the original pipeline design limits. This paper describes the design, manufacture and testing process for a self-propelled wrapping machine for in-field rehabilitation. The wrapping apparatus consists of several major components including an opening sufficiently wide to receive the pipe, a movement assembly, a winding head, a preforming device, an accumulator and an oscillating adhesive applicator. The wrapping apparatus uses the winding head to wrap the reinforcing steel strip around the pipe. The movement assembly uses a pair of tracks in contact with the pipe to drive the wrapping apparatus along which enables helical wrapping of the reinforcing strip material. The oscillating adhesive assembly applies structural adhesive to the pipe immediately before the strip is wound. The winding head, motive assembly and adhesive applicator are electronically synchronized to one another to enable precise control of pitch and adhesive volume. The paper also describes the field application of XHab including mobilization/demobilization of equipment and interaction with other rehabilitation equipment, as well as specific aspects such as initiation and termination of wrapping, protection of rehabilitated area and implementation of cathodic protection.

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