Numerical Modelling of Three Dimensional Honeycomb Labyrinth Seals Employing a Simplified Approach

2006 ◽  
Author(s):  
Dermot Collins ◽  
Joao Amaral Teixeira ◽  
Pete Crudgington ◽  
Paul C. Ivey
Keyword(s):  
Three Dimensional ◽  
Two Dimensional ◽  
Labyrinth Seals ◽  
Cfd Simulations ◽  
Simplified Approach ◽  
Pressure Profiles ◽  
Single Tooth ◽  
Average Variation ◽  
Flow Through ◽  
Overall Performance

This paper numerically analyses the flow through abradable honeycomb labyrinth seals using CFD. Three-dimensional CFD simulations using a single tooth have been compared to representative two-dimensional simulations. Two sizes of honeycomb (1.60mm and 3.20mm) have been analysed at pressure ratios from 1.20 up to 1.60. The seal geometry was kept constant throughout with a running clearance of 1.00mm. The honeycomb has been oriented in two planes with respect to the labyrinth teeth. The two-dimensional planes show equivalence both in terms of overall performance and inter-cavity pressure profiles. Comparisons of Cd typically agree within 2.5%, having an average variation of 1.3%. Total pressure profiles at the middle of the upstream and downstream cavity have been compared. These reveal typical average RMS variations of less than 3% between 3-D and 2-D profiles. It has also been shown that the honeycomb surface causes velocity effects in 3-D that propagate into the seal cavity. The technique used has achieved significant reductions in modelling times.

CFD Leakage Predictions of Labyrinth Seals Having Straight and Inclined Notched Teeth With Staggered Honeycomb Land

2018 ◽  
Author(s):  
Hasham H. Chougule ◽  
A. V. Mirzamoghadam
Keyword(s):  
Flow Resistance ◽  
Three Dimensional ◽  
Labyrinth Seal ◽  
Operating Conditions ◽  
Labyrinth Seals ◽  
Cfd Simulations ◽  
Maximum Improvement ◽  
Total Leakage ◽  
Flow Through ◽  
Honeycomb Cell

Labyrinth seal designs for reduced leakage have been analyzed by three-dimensional CFD simulations. The objective is to learn the effect of seal geometry modifications on total leakage through the seal and arrive at an advanced seal setting for improved seal effectiveness through reduction in leakage. Numerical modeling of the flow field were conducted at various operating conditions. The baseline seal model for this study is a conventional straight-through rotating four-tooth labyrinth seal and static honeycomb land having symmetrical hexagonal cells. The tooth design configurations include stepped single & double notched straight and inclined teeth. Another objective is to learn the effect of staggered honeycomb land with respect to rotor/teeth rotation. The effect of teeth inclination & teeth rotation compared to stationary is also discussed. CFD results indicate improved seal effectiveness with staggered honeycomb cell land. The maximum improvement of ∼9% was observed with stepped and notched inclined teeth configuration when combined with staggered honeycomb land. The leakage reduction leading to improvement in seal effectiveness as compared to baseline configuration is largely due to higher flow resistance, higher turbulence and higher blockages by introducing vortex in leakage flow through step and cavities.

Influence of a Honeycomb Facing on the Flow Through a Stepped Labyrinth Seal

2000 ◽  
Vol 124 (1) ◽  
pp. 140-146 ◽  
Author(s):  
V. Schramm ◽  
K. Willenborg ◽  
S. Kim ◽  
S. Wittig
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Theoretical Work ◽  
Labyrinth Seal ◽  
Honeycomb Structure ◽  
Experimental Investigations ◽  
Labyrinth Seals ◽  
Numerical Predictions ◽  
Flow Through ◽  
Aero Engines

This paper reports numerical predictions and measurements of the flow field in a stepped labyrinth seal. The theoretical work and the experimental investigations were successfully combined to gain a comprehensive understanding of the flow patterns existing in such elements. In order to identify the influence of the honeycomb structure, a smooth stator as well as a seal configuration with a honeycomb facing mounted on the stator wall were investigated. The seal geometry is representative of typical three-step labyrinth seals of modern aero engines. The flow field was predicted using a commercial finite volume code with the standard k-ε turbulence model. The computational grid includes the basic seal geometry as well as the three-dimensional honeycomb structures.

Numerical and Experimental Investigation of Return Channel Vane Aerodynamics With Two-Dimensional and Three-Dimensional Vanes

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
A. Hildebrandt ◽  
F. Schilling
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Static Pressure ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Field Performance ◽  
Two Dimensional ◽  
Flow Angle ◽  
Overall Performance ◽  
Return Channel

The present paper deals with the numerical and experimental investigation of the effect of return channel (RCH) dimensions of a centrifugal compressor stage on the aerodynamic performance. Three different return channel stages were investigated, two stages comprising three-dimensional (3D) return channel blades and one stage comprising two-dimensional (2D) RCH vanes. The analysis was performed regarding both the investigation of overall performance (stage efficiency, RCH total pressure loss coefficient) and detailed flow-field performance. For detailed experimental flow-field investigation at the stage exit, six circumferentially traversed three-hole probes were positioned downstream the return channel exit in order to get two-dimensional flow-field information. Additionally, static pressure wall measurements were taken at the hub and shroud pressure and suction side (SS) of the 2D and 3D return channel blades. The return channel system overall performance was calculated by measurements of the circumferentially averaged 1D flow field downstream the diffuser exit and downstream the stage exit. Dependent on the type of return channel blade, the numerical and experimental results show a significant effect on the flow field overall and detail performance. In general, satisfactory agreement between computational fluid dynamics (CFD)-prediction and test-rig measurements was achieved regarding overall and flow-field performance. In comparison with the measurements, the CFD-calculated stage performance (efficiency and pressure rise coefficient) of all the 3D-RCH stages was slightly overpredicted. Very good agreement between CFD and measurement results was found for the static pressure distribution on the RCH wall surfaces while small CFD-deviations occur in the measured flow angle at the stage exit, dependent on the turbulence model selected.

General principles of echocardiography

2016 ◽  
Author(s):  
Madalina Garbi ◽  
Jan D’hooge ◽  
Evgeny Shkolnik
Keyword(s):  
Blood Flow ◽  
Image Interpretation ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Post Processing ◽  
Ultrasound Waves ◽  
Advantages And Disadvantages ◽  
Biologic Effects ◽  
Flow Through ◽  
And Function

Echocardiography uses ultrasound waves to generate images of cardiovascular structures and to display information regarding the blood flow through these structures. Knowledge of basic ultrasound principles and current technology is essential for image interpretation and for optimal use of equipment during image acquisition and post-processing. This chapter starts by presenting the physics of ultrasound and the construction and function of instruments. Image formation, optimization, display, presentation, storage, and communication are explained. Advantages and disadvantages of available imaging modes (M-mode, two-dimensional, and three-dimensional) are detailed and imaging artefacts are illustrated. The potential biologic effects of ultrasound and the need for quality assurance are discussed.

scholarly journals A New Approach to Accuracy Evaluation of Single-Tooth Abutment Using Two-Dimensional Analysis in Two Intraoral Scanners

2019 ◽  
Vol 16 (6) ◽  
pp. 1021 ◽  
Author(s):  
Jiyoun Maeng ◽  
Young-Jun Lim ◽  
Bongju Kim ◽  
Myung-Joo Kim ◽  
Ho-Beom Kwon
Keyword(s):  
Dimensional Analysis ◽  
Cross Sections ◽  
Three Dimensional ◽  
Accuracy Evaluation ◽  
Two Dimensional ◽  
3D Data ◽  
Accuracy Comparison ◽  
Single Tooth ◽  
Sharp Edges ◽  
Data Files

The aim of this study was to two-dimensionally evaluate deviation errors at five digital cross-sections of single-tooth abutment in regards to data obtained from two intraoral scanners, and to evaluate accuracy of individual scanners. Two intraoral scanners, the Trios 3® (3 Shape, Copenhagen, Denmark) and EzScan® (Vatech, Hwaseong, Korea), were evaluated by utilizing 13 stone models. The superimposed 3D data files were sectioned into five different planes: buccal-lingual section (BL), mesial-distal section (MD), transverse high section (TH), transverse middle section (TM), and transverse low section (TL). Accuracy comparison between the two scanners in 5 groups was performed. BL vs. MD of each scanner, and three transverse groups (TH, TM, TL) of each scanner were analyzed for accuracy comparison. In comparison of 2-D analyses for two intraoral scanners, Trios 3® showed statistically significant higher accuracy in root mean square (RMS) at BL, TH, and TL (p < 0.05). For each scanner, RMS value showed that mesial-distal sections were more prone to error than buccal-lingual section, which exhibited statistically significant errors (p < 0.05) while the transverse groups did not. Two-dimensional analysis is more insightful than three-dimensional analysis on single-tooth abutment. In mesiodistal areas, rough prepped areas, and sharp edges where scanner accessibility is difficult, high deviation errors are shown.

scholarly journals Automated Quantification of Pneumothorax in CT

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Synho Do ◽  
Kristen Salvaggio ◽  
Supriya Gupta ◽  
Mannudeep Kalra ◽  
Nabeel U. Ali ◽  
...  
Keyword(s):  
Processing Time ◽  
Three Dimensional ◽  
Average Error ◽  
Two Dimensional ◽  
Algorithm Performance ◽  
Automated Method ◽  
Automated Quantification ◽  
Overall Performance ◽  
Processing Techniques ◽  
Aided Diagnosis

An automated, computer-aided diagnosis (CAD) algorithm for the quantification of pneumothoraces from Multidetector Computed Tomography (MDCT) images has been developed. Algorithm performance was evaluated through comparison to manual segmentation by expert radiologists. A combination of two-dimensional and three-dimensional processing techniques was incorporated to reduce required processing time by two-thirds (as compared to similar techniques). Volumetric measurements on relative pneumothorax size were obtained and the overall performance of the automated method shows an average error of just below 1%.

The Compressible Flow Through Cascade Actuator Discs

1958 ◽  
Vol 9 (2) ◽  
pp. 110-130 ◽  
Author(s):  
J. H. Horlock
Keyword(s):  
Shear Flow ◽  
Compressible Flow ◽  
Incompressible Flow ◽  
Three Dimensional ◽  
Approximate Solutions ◽  
Two Dimensional ◽  
Guide Vanes ◽  
The Past ◽  
Flow Through ◽  
Annular Cascade

SummaryA theory of the incompressible flow through two- and three-dimensional cascade actuator discs has been developed by several workers over the past ten years, and its accuracy has been confirmed in several experiments. This theory is briefly reviewed, and a parallel theory for subsonic compressible flow through actuator discs is developed. Approximate solutions for several examples are considered, including a compressible shear flow through a two-dimensional cascade, and a compressible flow through an annular cascade of guide vanes.

scholarly journals Performance Characteristics of Two- and Three-Dimensional Impellers in Centrifugal Compressors

1986 ◽  
Author(s):  
H. Harada
Keyword(s):  
Centrifugal Compressor ◽  
Closed Loop ◽  
Three Dimensional ◽  
Performance Characteristics ◽  
Working Fluid ◽  
Angle Distribution ◽  
Two Dimensional ◽  
Blade Angle ◽  
Operating Range ◽  
Overall Performance

The overall performance of two- and three-dimensional impellers of a centrifugal compressor were tested and compared. A closed loop test stand with Freon gas as working fluid was employed for the experiments. The inlet and outlet velocity distribtions of all impellers were measured using three hole cobra probes. As a result, it has been revealed that three-dimensional impellers are superior to two-dimensional one in terms of efficiency, head coefficient and operating range. Further, it has also been clarified that the impeller slip factor is affected by blade angle distribution.

Wake behaviour and instability of flow through a partially blocked channel

2007 ◽  
Vol 582 ◽  
pp. 319-340 ◽  
Author(s):  
M. D. GRIFFITH ◽  
M. C. THOMPSON ◽  
T. LEWEKE ◽  
K. HOURIGAN ◽  
W. P. ANDERSON
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Underlying Mechanism ◽  
Two Dimensional ◽  
Recirculation Bubble ◽  
Dimensional Flow ◽  
Starting Point ◽  
Two Dimensional Flow ◽  
Flow Through ◽  
The Stability

The two-dimensional flow through a constricted channel is studied. A semi-circular bump is located on one side of the channel and the extent of blockage is varied by adjusting the radius of the bump. The blockage is varied between 0.05 and 0.9 of the channel width and the upstream Reynolds number between 25 and 3000. The geometry presents a simplified blockage specified by a single parameter, serving as a starting point for investigations of other more complex blockage geometries. For blockage ratios in excess of 0.4, the variation of reattachment length with Reynolds number collapses to within approximately 15%, while at lower ratios the behaviour differs. For the constrained two-dimensional flow, various phenomena are identified, such as multiple mini-recirculations contained within the main recirculation bubble and vortex shedding at higher Reynolds numbers. The stability of the flow to three-dimensional perturbations is analysed, revealing a transition to a three-dimensional state at a critical Reynolds number which decreases with higher blockage ratios. Separation lengths and the onset and structure of three-dimensional instability observed from the geometry of blockage ratio 0.5 resemble results taken from backward-facing step investigations. The question of the underlying mechanism behind the instability being either centrifugal or elliptic in nature and operating within the initial recirculation zone is analytically tested.

Three-Dimensional Lifting-Surface Theory for an Annular Blade Row

1979 ◽  
Author(s):  
G. F. Homicz ◽  
J. A. Lordi
Keyword(s):  
Integral Equation ◽  
Three Dimensional ◽  
Computer Time ◽  
Two Dimensional ◽  
Blade Loading ◽  
Surface Theory ◽  
Lifting Surface ◽  
Strip Theory ◽  
Blade Row ◽  
Flow Through

A lifting-surface analysis is presented for the steady, three-dimensional, compressible flow through an annular blade row. A kernel-function procedure is used to solve the linearized integral equation which relates the unknown blade loading to a specified camber line. The unknown loading is expanded in a finite series of prescribed loading functions which allows the required integrations to be performed analytically, leading to a great savings in computer time. Numerical results are reported for a range of solidities and hub-to-tip ratios; comparisons are made with both two-dimensional strip theory and other three-dimensional results.

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