Leakage Rate Performance Mapping of Smooth Stator/Grooved Rotor Labyrinth Seals Using Statistical Tools

2019 ◽  
Author(s):  
Hanxiang Jin ◽  
Alexandrina Untaroiu
Keyword(s):  
Axial Direction ◽  
Surface Geometry ◽  
Labyrinth Seals ◽  
Performance Improvements ◽  
Design Variables ◽  
Liquid Seal ◽  
Baseline Case ◽  
Current Design ◽  
Computational Fluid Dynamics Cfd ◽  
Geometric Variables

Abstract As one of the most widely used annular pressure seals, labyrinth seals are used to reduce the fluid leakage between different pressure stages. They are multi-toothed seals with circumferential grooves located on the rotor surfaces and/or stator surfaces, which are distributed along the axial direction. The intricacy of the surface geometry and directionality of the seal pattern assist in converting pressure into dissipated kinetic energy without rotor-stator rub effects. The majority of previous studies focused on annular labyrinth liquid seals with smooth rotor/grooved stator (SR/GS) case, whereas this paper attempts to elucidate the effects of geometric variables modification for smooth stator/grooved rotor (SS/GR) case using Computational Fluid Dynamics (CFD) and design of experiments (DOE) techniques. In this study, a smooth stator/grooved rotor liquid seal was modeled and validated against experimental data. The model was then used as a baseline case for a sensitivity analysis of its geometry variations. Simulation results under different pressures/rotor speeds were used to validate the CFD setup. Four geometric parameters of the seal were then selected as design variables to adapt the baseline geometry for potential performance improvements. The design space was discretized using the DOE technique. Similar mesh/simulation setups were automatically generated for each design point. Regression analysis was applied based on the CFD results for a better understanding of the effects associated with different design variables. These results can be used to improve the current design of smooth stator/grooved rotor annular pressure seals in order to achieve lower leakage rates.

Design Optimization for the Hydraulic Efficiency Improvement of a Mixed-Flow Pump Diffuser

2015 ◽  
Author(s):  
Sung Kim ◽  
Kyoung-Yong Lee ◽  
Ji-Hyuk Kim ◽  
Young-Seok Choi
Keyword(s):  
Design Optimization ◽  
Meridional Plane ◽  
Total Efficiency ◽  
Mixed Flow ◽  
Design Variables ◽  
Total Head ◽  
Blade Shape ◽  
Computational Fluid Dynamics Cfd ◽  
Geometric Variables ◽  
Flow Pump

In this paper, design optimization for mixed-flow pump diffusers was carried out using a commercial computational fluid dynamics (CFD) code and design-of-experiments (DOE). The design variables of meridional plane and vane plane development were defined for the diffuser design. The blade shape of the diffuser was designed using the traditional method, in which the inlet and exit angles are connected smoothly. First, the design optimization of the defined design variables for vane plane development was achieved. Next, design optimization of the defined design variables for the meridional plane was performed. The objective functions were defined as the total head and total efficiency of the diffusers. The importance of the geometric design variables was analyzed using 2k factorial designs, and the design optimization of the geometric variables was determined using the response surface method (RSM). The numerical results for reference and optimum models in this work were compared and discussed.

Design space optimisation of an unmanned aerial vehicle submerged inlet through the formulation of a data-fusion-based hybrid model

2021 ◽  
pp. 1-18
Author(s):  
F. Akram ◽  
H. A. Khan ◽  
T. A. Shams ◽  
D. Mavris
Keyword(s):  
Data Mining ◽  
Data Fusion ◽  
Design Space ◽  
Design Parameters ◽  
Design Variables ◽  
Current Design ◽  
Aerial Vehicle ◽  
Hybrid Data ◽  
Computational Fluid Dynamics Cfd ◽  
Cruise Flight

ABSTRACT The research focuses on the design space optimisation of National Advisory Committee for Aeronautics (NACA) submerged inlets through the formulation of a hybrid data fusion methodology. Submerged inlets have drawn considerable attention owing to their potential for good on-design performance, for example during cruise flight conditions. However, complexities due to the geometrical topology and interactions among various design variables remain a challenge. This research enhances the current design knowledge of submerged inlets through the utilisation of data mining and Computational Fluid Dynamics (CFD) methodologies, focusing on design space optimisation. A two-pronged approach is employed where the first step encompasses a low-fidelity model through data mining and surrogate modelling to predict and optimise the design parameters, while the second step uses the Design of Experiments (DOE) approach based on the CFD results for the candidate design geometry to construct a surrogate model with high fidelity for design refinement. The feasibility of the proposed methodology is demonstrated for the optimisation of the total pressure recovery of a NACA submerged inlet for the subsonic flight regime. The proposed methodology is found to provide good agreement between the surrogate and CFD-based model and reduce the optimisation processing time by half in comparison with conventional (global-based) CFD optimisation approaches.

scholarly journals Numerical Analysis of Flow across Brush Elements Based on a 2-D Staggered Tube Banks Model

Aerospace ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 19
Author(s):  
Xiaolei Song ◽  
Meihong Liu ◽  
Xiangping Hu ◽  
Xueliang Wang ◽  
Taohong Liao ◽  
...  
Keyword(s):  
Euler Number ◽  
Dynamic Pressure ◽  
Labyrinth Seals ◽  
System A ◽  
Brush Seal ◽  
Back Plate ◽  
Computational Fluid Dynamics Cfd ◽  
Secondary Air ◽  
Tube Banks ◽  
Gas Expansion

In order to improve efficiency in turbomachinery, brush seal replaces labyrinth seals widely in the secondary air system. A 2-d staggered tube bank model is adopted to simulate the gas states and the pressure character in brush seal, and computational fluid dynamics (CFD) is used to solve the model in this paper. According to the simulation results, the corrected formula of the Euler number and dimensionless pressure are given. The results show that gas expands when flow through the bristle pack, and the gas expansion closes to an isotherm process. The dynamic pressure increases with decreasing static pressure. The Euler number can reflect the seal performance of brush seals in leakage characteristics. Compared with increasing the number of rows, the reduction of the gap is a higher-efficiency method to increase the Euler number. The Euler number continually increases as the gap decreases. However, with the differential pressure increasing, Euler number first increases and then decreases as the number of rows increases. Finally, the pressure distribution on the surface of end rows is asymmetric, and it may increase the friction between the bristles and the back plate.

Lateral Forces From Single Gland Rotor Labyrinth Seals in Turbines

2004 ◽  
Vol 126 (3) ◽  
pp. 626-634 ◽  
Author(s):  
Bum Ho Song ◽  
Seung Jin Song
Keyword(s):  
Axial Direction ◽  
Labyrinth Seal ◽  
Turbine Stage ◽  
Labyrinth Seals ◽  
Flow Response ◽  
Lateral Forces ◽  
Downstream Flow ◽  
Shrouded Rotor ◽  
Upstream Flow ◽  
Sealing Gap

Even though interest in labyrinth seal flows has increased recently, an analytical model capable of predicting turbine flow response to labyrinth seals is still lacking. Therefore, this paper presents a new model to predict flow response in an axial turbine stage with a shrouded rotor. A concentric model is first developed, and this model is used to develop an eccentric model. Basic conservation laws are used in each model, and a nonaxisymmetric sealing gap is prescribed for the eccentric model. Thus, the two models can predict the evolution of a uniform upstream flow into a nonuniform downstream flow. In turbines with concentric shrouded rotors, the seal flow is retarded in the axial direction and tangentially underturned. In turbines with eccentric shrouded rotors, flow azimuthally migrates away from and pressure reaches its peak near the maximum sealing gap region. Finally, the rotordynamic implications of such flow nonuniformities are discussed and compared against eccentric unshrouded turbine predictions.

CFD Leakage Predictions of Unworn and Worn Labyrinth Seals With and Without Tooth Axial Offset

2017 ◽  
Author(s):  
Hasham H. Chougule ◽  
Alexander Mirzamoghadam
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Modeling ◽  
Steady State ◽  
Flow Field ◽  
Labyrinth Seals ◽  
Small Clearance ◽  
Total Leakage ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Deflection

The objective of this study is to develop a Computational Fluid Dynamics (CFD) based methodology for analyzing and predicting leakage of worn or rub-intended labyrinth seals during operation. The simulations include intended tooth axial offset and numerical modeling of the flow field. The purpose is to predict total leakage through the seal when an axial tooth offset is provided after the intended/unintended rub. Results indicate that as expected, the leakage for the in-line worn land case (i.e. tooth under rub) is higher compared to unworn. Furthermore, the intended rotor/teeth forward axial offset/shift with respect to the rubbed land reduces the seal leakage. The overall leakage of a rubbed seal with axial tooth offset is observed to be considerably reduced, and it can become even less than a small clearance seal designed not to rub. The reduced leakage during steady state is due to a targeted smaller running gap because of tooth offset under the intended/worn land groove shape, higher blockages, higher turbulence and flow deflection as compared to worn seal model without axial tooth offset.

Numerical Simulation of Thermal Stress for a Liquid-Cooled Exhaust Manifold

2008 ◽  
Author(s):  
Dong Fu ◽  
Dui Huang ◽  
Ahmed Juma ◽  
Curtis M. Schreiber ◽  
Xiuling Wang ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Material Behavior ◽  
Nonlinear Material ◽  
Large Temperature ◽  
Space Partitioning ◽  
Experiment Data ◽  
Industrial Experiment ◽  
Binary Space Partitioning ◽  
Current Design ◽  
Computational Fluid Dynamics Cfd

Liquid-cooled exhaust manifolds are widely used in turbocharged diesel engines. The large temperature gradient in the overall manifold will cause remarkable thermal stress. The objective of the project is to modify the current design for preventing the high thermal stress and extending the life span of the manifold. To achieve the objective, the combination between Computational Fluid Dynamics (CFD) with Finite Element (FE) is introduced. Firstly, CFD analysis is conducted to obtain temperature distribution, providing boundary conditions of the thermal load on the FE mesh. Afterward, FE analysis is carried out to determine the thermal stress. The interpolation of the temperature data from CFD to FE is done by Binary Space Partitioning (BSP) tree algorithm. To accurately quantify the thermal stress, nonlinear material behavior is considered. The computational results are compared with that of Number of Transfer Units (NTU) method, and are further verified with industrial experiment data. All these comparisons indicate that present investigation reasonably predicts the thermal stress behavior. Based on the results, recommendations are given to optimize the manifold design.

Numerical Investigations of Leakage Performance Degradations in Labyrinth and Flexible Seals Due to Wear

2020 ◽  
Author(s):  
Xinbo Dai ◽  
Xin Yan ◽  
Kun He ◽  
Jun Li ◽  
Zhenping Feng
Keyword(s):  
Labyrinth Seal ◽  
Leakage Rate ◽  
Labyrinth Seals ◽  
Element Analysis ◽  
Numerical Investigations ◽  
Forward Bending ◽  
The Finite Element Analysis ◽  
Before And After ◽  
Computational Fluid Dynamics Cfd ◽  
Wear Damage

Abstract The Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) methods are utilized to investigate the leakage performance degradations in two kinds of flexible seals (i.e. forward bending and backward bending) and two kinds of shroud labyrinth seals (i.e. with straight fins and chamfered fins) in rubbing events. With the existing experimental data, FEA methods for contacting simulations and CFD methods for leakage rate and flow pattern predictions are carefully examined. The wear characteristic and leakage performance between labyrinth seals and flexible seals are compared before and after rub. The results show that, in rubbing process, the labyrinth seal with straight (symmetrical) fins is likely to undergo the mushrooming damage, whereas the labyrinth seal with chamfered (asymmetrical) fins is likely to undergo the tooth-bending damage. In rubbing process, compared with the labyrinth seal, the flexible seal has a superior characteristic in resisting the wear damage due to increased flexibility of fin. For a labyrinth seal with 0.3mm design clearance and a flexible seal with 0.15mm design clearance, the 0.5mm radial displacement of rotor will result in 110% increase of leakage rate for labyrinth seal, and 7% increase of leakage rate for flexible seal after wear. Under the same conditions, the forward bending flexible seal has a lower leakage rate than the backward bending flexible seal before and after rub.

On the Leakage and Dynamic Force Coefficients of a Novel Stepped Shaft Pocket Damper Seal: Experimental and Numerical Verification

2020 ◽  
Author(s):  
Jing Yang ◽  
Luis San Andres ◽  
Xueliang Lu
Keyword(s):  
High Performance ◽  
System Stability ◽  
Damping Coefficient ◽  
Dynamic Force ◽  
Numerical Verification ◽  
Labyrinth Seals ◽  
Stepped Shaft ◽  
Blade Tip ◽  
Rotor Surface ◽  
Computational Fluid Dynamics Cfd

Abstract High performance turbomachinery favors annular seals with a large damping coefficient to ensure rotor system stability. Pocket damper seals (PDSs), a variation of labyrinth seals with axial blades (ribs) and adding circumferential partition walls (ridges), produce a favorable damping performance. To further enhance the damping characteristic, a novel stepped shaft PDS is hereby introduced. The invention has a unique arrangement of steps on the rotor, each facing an upstream rib in a pocket. The step and a blade tip form a tight clearance (c1), while the rotor surface and the downstream blade tip make a larger clearance (c2). To validate the invention performance, a stepped shaft PDS (c1/c2 = 0.5) with four ribs and eight pockets is built and tested. For supply pressure (Ps) = 1.1 bar to 3.2 bar, the measured leakage for the stepped shaft PDS is 50% of that for an identical PDS with a smooth rotor surface (c1/c2 = 1, i.e., a uniform clearance PDS). Computational fluid dynamics (CFD) and bulk flow model predicted leakages agree well with the measurements. For Ps = 2.3 bar, the test damping coefficient for the stepped shaft PDS is ~ 1.5 times greater than that for the uniform clearance PDS. With an increase in Ps to 3.2 bar, the stepped shaft PDS shows a 2.5 times increase in damping coefficient. Both the test data and CFD predictions demonstrate the superior damping performance of the invention, thus providing a novel alternative seal configuration for turbomachinery usage.

Computational Investigation of Flows and Pressure Fields Associated With Spur Gear Meshing

2014 ◽  
Author(s):  
Baydu C. Al ◽  
Kathy Simmons ◽  
Herve P. Morvan
Keyword(s):  
Power Transmission ◽  
Axial Direction ◽  
Spur Gear ◽  
Transient Pressure ◽  
Pressure Fields ◽  
Oil Flow ◽  
Power Transmission Systems ◽  
Compression And Expansion ◽  
Potential Applications ◽  
Computational Fluid Dynamics Cfd

The efficiency of power transmission systems is increasingly targeted with a view to reducing parasitic losses and improving specific fuel consumption (SFC). One of the effects associated with such parasitic losses is the successive compression and expansion of fluid within the cavities between teeth of a meshing gear pair as they rotate. This process is cyclic and there are multiple cavities compressed and expanded at the same time. During the meshing process the volume of the cavity between the teeth suddenly contracts and as a result pressure rises. The fluid is therefore expelled primarily in the axial direction (for spur gears) since this area is considerably larger compared to the backlash area. Once the cavity starts to expand fluid is drawn into the cavity between the teeth by the negative pressure. Besides the air flow in the gear box, the meshing point is of particular interest to the oil flow, since oil is typically injected at or upstream of the meshing point. Good understanding of such flows can be used to balance lubrication needs with the need to minimise the required oil volumes and parasitic losses. This paper proposes the use of Computational Fluid Dynamics (CFD) as a means to investigate the phenomenon. A simplified two-dimensional CFD approach has been developed to study flows and pressure fields associated with spur gear meshing. The influence of the rotational speed has been investigated. Good validation is shown for the transient pressure variation within the tooth space. The limitations and potential applications of the modelling strategy are then discussed.

Computational Fluid Dynamics Applied to Bradley Hydrocyclones

2006 ◽  
Vol 530-531 ◽  
pp. 376-381 ◽  
Author(s):  
Luiz Gustavo Martins Vieira ◽  
João Jorge Ribeiro Damasceno ◽  
Marcos A.S. Barrozo
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fluid Model ◽  
Reynolds Stress Model ◽  
Operational Conditions ◽  
Air Core ◽  
Volume Of Fluid Model ◽  
Computational Fluid Dynamics Cfd ◽  
Geometric Variables ◽  
Solid Liquid

Hydrocyclones are centrifugal devices employed on the solid-liquid and liquid-liquid separation. The operation and building of these devices are relatively simple, however the flow inside them is totally complex and its prediction is very difficult. The fluid moves on all possible directions (axial, radial and swirl), the effects of turbulence can not negligible and an air core along the center line of the hydrocyclone can appear when the operational conditions are favorable. For that reason, the most models that are used to predict the hydrocyclone performance are empirical and require the collection of the main operational and geometric variables in order to validate them. This work objectified to apply Computational Fluid Dynamics (CFD) on Bradley Hydrocyclone and compare the results from this technique to empirical models. The numerical simulation was made in a computational code called Fluent® that solves the transport equation by finite volume technique. The turbulence was described by Reynolds Stress Model (RSM) and the liquid-gas interface was treated by Volume of Fluid Model (VOF). In agreement with the results from the simulation, it was possible to predict the internal profiles of velocity, pressure, air core, particle trajectories, efficiencies, pressure drop and underflow-to-throughput ratio.

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