scholarly journals Effect of Clearance and Cavity Geometries on Leakage Performance of a Stepped Labyrinth Seal

Processes ◽  
2020 ◽  
Vol 8 (11) ◽  
pp. 1496
Author(s):  
Min Seok Hur ◽  
Soo In Lee ◽  
Seong Won Moon ◽  
Tong Seop Kim ◽  
Jae Su Kwak ◽  
...  
Keyword(s):  
Dimensionless Parameter ◽  
Flow Analysis ◽  
Labyrinth Seal ◽  
Performance Parameter ◽  
Design Parameters ◽  
Cfd Analysis ◽  
Cavity Size ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd ◽  
Leakage Characteristics

This study evaluated the leakage characteristics of a stepped labyrinth seal. Experiments and computational fluid dynamics (CFD) analysis were conducted for a wide range of pressure ratios and clearance sizes, and the effect of the clearance on the leakage characteristics was analyzed by determining the performance of the seal using a dimensionless parameter. It was observed from the analysis that the performance parameter of the seal decreases as the clearance size increases, but it tends to increase when the clearance size exceeds a certain value. In other words, it was revealed that there exists a specific clearance size (Smin) which minimizes the performance parameter of the seal. To identify the cause of this tendency change, a flow analysis was conducted using CFD. It was confirmed that the leakage characteristics of the stepped seal are affected by the size of the cavity, which is the space between the teeth. Therefore, a parametric study was conducted on the design parameters related to the cavity size (tooth height and pitch). The results show that the performance parameter decreases as the tooth height and pitch decreases. Moreover, Smin increases as the tooth height increases and the pitch decreases.

Piston-Lift Check Valve Flow Verification Using CFD

2018 ◽  
Author(s):  
Matthew Laney ◽  
Ronald Farrell
Keyword(s):  
Flow Characteristics ◽  
Check Valve ◽  
Valve Lift ◽  
Cfd Analysis ◽  
Test Results ◽  
Finite Element Software ◽  
Translational Movement ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

Computational Fluid Dynamics (CFD) is increasingly being used as a reliable method for determining flow characteristics of a wide range of flow situations. This paper presents an extension of paper PVP2017-66269, “Check Valve Flow and Disk Lift Simulation Using CFD” [1], and utilizes some of the same concepts to characterize flow through piston-lift check valves. The previous example considered a swing check valve involving rotational movement; this example considers a vertical lift piston check valve involving translational movement. Specifically, CFD was used to determine valve flow coefficients (CV) as a function of disk lift position as well as to determine the flow rate required to achieve full open or predict intermediate disk lift positions. The CFX application, which is part of the ANSYS suite of finite element software, was used to determine the flow characteristics. As presented in PVP2017-66269, balancing flow-induced forces on the check element and considering the disk assembly weight, the valve lift behavior can be predicted. Results from the CFX analysis were compared to recent test results of a skirted disk-piston check valve and previous test results of a standard disk-piston check valve. The results showed good agreement in most cases. This validates that flow characteristics across valves with different types of check elements at different disk lift positions can be reliably predicted using CFD analysis. It is important to note that while the test results and CFD analysis showed good agreement, it was vital that actual testing be performed in order to validate the approach. This follows the recommendation outlined in the previous paper.

Check Valve Flow and Disk Lift Simulation Using CFD

2017 ◽  
Author(s):  
Ronald Farrell ◽  
L. Ike Ezekoye ◽  
Mark Rain
Keyword(s):  
Flow Analysis ◽  
Flow Characteristics ◽  
Check Valve ◽  
Valve Lift ◽  
Valve Design ◽  
Valve Development ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd ◽  
Opening And Closing ◽  
Good Agreement

Computational Fluid Dynamics (CFD) is increasingly being used as a reliable method for determining flow characteristics of a wide range of flow situations. This paper presents an investigation on the application of CFD to characterize the opening and closing of check valves. Specifically, using CFD results, a procedure was developed to determine valve flow coefficients (CV) as a function of disk lift positions as well as to determine the flow rate required to achieve full open or predict intermediate disk lift positions. The method could be used for a wide range of check valves such as swing check valves, lift check valves, tilting disk check valves, or inline check valves. Using CFX which is a part of the ANSYS suite of finite element programs, examples of the predictive nature of CFD to characterize check valve performance are presented to address swing check and lift check valve designs. It is shown that balancing flow-induced forces on the disk and considering the disk assembly weight in the process is sufficient to model the valve lift behavior. Analysis results from this approach were compared with available test data of the modeled valves. The comparison showed good agreement, thus validating that both flow coefficients (CV) and flow rates across the valves at different disk lift positions can be reasonably predicted with this approach. The results of this study suggest that this approach can be used for valve design optimization and flow analysis of check valves. However, it should be pointed out that CFD is an evolving technology and is not a substitute for testing. The use of this tool compliments testing and, if carefully managed, can save valve development cost.

Multi-Objective Optimization of a Steam Surface Condenser Using the Territorial Particle Swarm Technique

2016 ◽  
Vol 138 (5) ◽  
Author(s):  
Pooya Mirzabeygi ◽  
Chao Zhang
Keyword(s):  
Particle Swarm ◽  
Design Parameters ◽  
Cfd Analysis ◽  
Multi Objective Optimization ◽  
Multi Objective ◽  
Flow And Heat Transfer ◽  
Surface Condenser ◽  
Computational Fluid Dynamics Cfd ◽  
Shell And Tube ◽  
Outside Diameter

The multi-objective territorial particle swarm optimization (MOTPSO) technique is proposed in this work for the optimal design of steam surface condensers. The main objective of this work is to maximize the condensation rate in a condenser while the pressure loss is minimized. Various design parameters, such as the tube outside diameter, thickness, and pitch, are considered to find the optimal ones for shell and tube heat exchangers considered in this study. The two-dimensional computational fluid dynamics (CFD) analysis is performed to solve the fluid flow and heat transfer in the condenser to assess the performance of different designs.

scholarly journals A Study on the Leakage Characteristics of a Stepped Labyrinth Seal with a Ribbed Casing

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3719
Author(s):  
Min-Seok Hur ◽  
Seong-Won Moon ◽  
Tong-Seop Kim
Keyword(s):  
Turbine Blades ◽  
Labyrinth Seal ◽  
Leakage Flow ◽  
Flow Function ◽  
Labyrinth Seals ◽  
Leakage Flow Rate ◽  
New Type ◽  
Computational Fluid Dynamics Cfd ◽  
Leakage Characteristics ◽  
Wide Operating

A new type of stepped seal with a ribbed casing is proposed to efficiently reduce the leakage at the tips of turbine blades. The leakage characteristics of two different types of labyrinth seals (conventional seal vs. ribbed seal) were compared and analyzed through computational fluid dynamics (CFD) in a wide operating range of pressure ratios and clearances. The analysis showed that the ribbed seal has superior leakage performance to the conventional seal at all clearance sizes. With the same clearance size (S/H = 1.0), the flow function of the ribbed seal was approximately 21.5–42.6% less than that of the conventional seal. Also, different trends of variation in the flow function according to the increase of the clearance were found between the conventional and ribbed seals. The leakage flow inside the labyrinth seal was analyzed to explain the cause of this difference in tendency, and it was confirmed that the added ribs cause collision between the leakage flow and the tooth wall, even with the increase of the clearance. Also, the ribbed seal enables operation at a larger clearance with the same leakage performance when comparing the absolute leakage flow rate of the two seals. In addition, a parametric study on the influence of the rib height and rib inclination angle revealed that the flow function generally decreases as both parameters increase.

Flow Analysis in Pipe of a Manifold Block

2012 ◽  
Vol 6 (4) ◽  
pp. 494-501 ◽  
Author(s):  
Osamu Abe ◽  
◽  
Tetsuhiro Tsukiji ◽  
Takeshi Hara ◽  
Kazutoshi Yasunaga ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Pipe Flow ◽  
Hydraulic System ◽  
Flow Analysis ◽  
Cfd Analysis ◽  
Hydraulic Systems ◽  
Pressure Drops ◽  
Computational Fluid Dynamics Cfd ◽  
Pipeline Design

Manifold blocks are recently used to connect hydraulic components in hydraulic system, which has flow channel inside. They are useful for reducing the size and weight of hydraulic systems. This paper deals with solid manifold block and laminated manifold block. They are different from machining. We investigate pressure drops of their pipe flow with Computational Fluid Dynamics (CFD) and compare those of two types. And then, we conduct experiment, measuring pressure and visualization, to validate the results of CFD analysis. By using these results, we are intended to obtain guidelines for pipeline design in laminated manifold block.

EFFECT OF SKIRT ANGLE AND FEATHERS FORMATION ON SHUTTLECOCK AERODYNAMICS PERFORMANCE

2015 ◽  
Vol 76 (8) ◽  
Author(s):  
Tajuddin Md. Jahi ◽  
Haziq Ikhwan Zawawi ◽  
Norazah Abd Rahman
Keyword(s):  
Aerodynamic Drag ◽  
Aerodynamic Characteristics ◽  
Spin Rotation ◽  
Design Parameters ◽  
World Federation ◽  
Cfd Analysis ◽  
Optimal Value ◽  
Computational Fluid Dynamics Cfd ◽  
Α Angle ◽  
Very High

Aerodynamic characteristics of badminton shuttlecock are significantly different from balls used in other sports. Shuttlecock can achieve a very high initial speed and at the same time, it can decelerate very fast. This is due to the significant aerodynamic drag it experiences during its in-flight motion. A computational fluid dynamics (CFD) analysis was carried out to understand the aerodynamics of a feathers shuttlecock approved by Badminton World Federation (BWF) for international tournaments. The aerodynamics performance of a standard shuttlecock at steady-state flight was investigated. The shuttlecock was assumed to be rigid and have no spin rotation; and velocity considered was 92 m/s. Effects of parameters such as angle of attack, α; angle of skirt, Ɵ; and angle of feathers, β; on the shuttlecock drag coefficient, Cd; were studied. It is found that smaller Ɵ leads to smaller Cd. Analysis shows that the Cd is the largest when the shuttlecock is at α = 0°. Besides that, the Cd is also influenced by β which the standard shuttlecock has fairly small Cd. Formation of feathers of the standard shuttlecock may be further twisted to the optimal value of β in order to increase its drag. As a result, Ɵ and β may be considered as design parameters in order to obtain the desired aerodynamics performance.

Power Dissipation in Smooth and Honeycomb Labyrinth Seals

1989 ◽  
Author(s):  
W. F. McGreehan ◽  
S. H. Ko
Keyword(s):  
Power Dissipation ◽  
High Speed ◽  
Material Design ◽  
Labyrinth Seal ◽  
General Assumption ◽  
Design Parameters ◽  
Leakage Flow ◽  
Labyrinth Seals ◽  
Seal Design ◽  
Wide Range

The surface frictional characteristics of a labyrinth seal can result in significant windage power dissipation for high speed seals. Recent advances in seal design have produced high speed, high pressure labyrinth seals which operate at very low leakage rates. The reduced leakage is beneficial to gas turbine efficiency, but seal discharge temperatures can approach material design limits with high windage power dissipation. Also, a high air temperature rise can influence seal leakage flow. Consequently, the general assumption of negligible rotational effect on leakage is not always valid. A method is presented for the prediction of seal power dissipation and leakage flow over a wide range of design parameters. Results are compared to available test data and several approaches examined for the reduction of seal windage.

Leakage characteristics of flanged pipe joints

1977 ◽  
Vol 12 (1) ◽  
pp. 29-36 ◽  
Author(s):  
H Fessler ◽  
D A Perry
Keyword(s):  
Surface Finish ◽  
Joint Surface ◽  
Clamping Force ◽  
Face Surface ◽  
Joint Efficiency ◽  
Wide Range ◽  
Pipe Joints ◽  
Surface Profiles ◽  
Leakage Characteristics ◽  
Gasket Material

Standard flanges for five widely differing pressure ratings, having a wide range of different joint surface profiles, were sealed by flat rubber or asbestos gaskets. Different initial bolt tensions were applied and the variation of clamping force with internal pressure was measured up to leakage of the joint. The joint efficiency, defined as: (end thrust due to leakage pressure on bore area of pipe)/(total initial bolting force), is not affected by variations in joint-face surface finish if machining grooves across the joint surface are avoided. Minimum values of joint efficiency are given. The effects of gasket material, width and thickness and number of bolts on joint efficiency are considered.

scholarly journals Flow and Particle Modelling of Dry Powder Inhalers: Methodologies, Recent Development and Emerging Applications

Pharmaceutics ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 189
Author(s):  
Zhanying Zheng ◽  
Sharon Shui Yee Leung ◽  
Raghvendra Gupta
Keyword(s):  
Dry Powder Inhaler ◽  
Research Direction ◽  
Particle Methods ◽  
Future Research ◽  
High Dose ◽  
Dry Powder ◽  
Multi Scale ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd ◽  
Discrete Element Methods

Dry powder inhaler (DPI) is a device used to deliver a drug in dry powder form to the lungs. A wide range of DPI products is currently available, with the choice of DPI device largely depending on the dose, dosing frequency and powder properties of formulations. Computational fluid dynamics (CFD), together with various particle motion modelling tools, such as discrete particle methods (DPM) and discrete element methods (DEM), have been increasingly used to optimise DPI design by revealing the details of flow patterns, particle trajectories, de-agglomerations and depositions within the device and the delivery paths. This review article focuses on the development of the modelling methodologies of flow and particle behaviours in DPI devices and their applications to device design in several emerging fields. Various modelling methods, including the most recent multi-scale approaches, are covered and the latest simulation studies of different devices are summarised and critically assessed. The potential and effectiveness of the modelling tools in optimising designs of emerging DPI devices are specifically discussed, such as those with the features of high-dose, pediatric patient compatibility and independency of patients’ inhalation manoeuvres. Lastly, we summarise the challenges that remain to be addressed in DPI-related fluid and particle modelling and provide our thoughts on future research direction in this field.

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