Optimization of the Straight-Through Labyrinth Seal With a Smooth Land

2018 ◽  
Author(s):  
Włodzimierz Wróblewski ◽  
Daniel Frączek ◽  
Artur Szymański ◽  
Krzysztof Bochon ◽  
Sławomir Dykas ◽  
...  
Keyword(s):  
Discharge Coefficient ◽  
Experimental Testing ◽  
High Capacity ◽  
Labyrinth Seal ◽  
Response Surfaces ◽  
Measuring System ◽  
Cfd Model ◽  
Test Rig ◽  
Ansys Cfx ◽  
Wide Range

The primary goal of this study was to develop and experimentally validate the methodology of labyrinth seals optimization concerning leakage. The problem was investigated using the ANSYS CFX commercial software. This paper presents the methodology and results of the optimization of a straight-through labyrinth seal with two inclined fins against smooth-land. The optimization was performed using commercial tools implemented in the ANSYS Workbench environment, such as Goal-Driven Optimization (GDO). The response surfaces were created based on Latin hypercube samples found from CFD calculations. The CFD solver — Ansys CFX, using a steady-state scheme with the k-omega Shear Stress Transport turbulence model, was applied. The CFD model was previously validated concerning spatial discretisation and turbulence modelling. A screening algorithm was used to find the best candidates on the response surfaces. The objective function adopted in the labyrinth seal optimization was the minimization of the discharge coefficient value. A wide range of parameters of the fins position and shape, such as the angles, heights and widths, were taken into account, with physically justified degrees of freedom. The leakage reductions being the effect of the optimization were considerable. The cuts in the discharge coefficient significantly exceed the uncertainties of the CFD model and the test rig accuracy. The factors that have the strongest impact on the leakage reduction in are the inclination, thickness of the fin tips, and the distance between fins. The optimization results were supported with the results of an in-house experiment performed on a stationary, linear test rig. The specimens tested experimentally were on the same scale (1:1) as the optimised ones. The test rig was fed by a high-capacity vacuum air blower, which made it possible to reach critical pressure ratios, with high-precision hot wire anemometry (HWA) mass flow evaluation. The measuring system also enabled assessment of the pressure distribution along the labyrinth structure. The experimental testing results were compared to the CFD calculations and the optimization effects, highlighting some specific tendencies in the labyrinth seal flow behaviour. Good agreement was obtained between the optimization results and the experimental data, which proves that the presented methodology is sufficient for the labyrinth seal optimization. The same methods will also be applied to more sophisticated sealing structures.

Optimization of the Straight-Through Labyrinth Seal With a Smooth Land

2018 ◽  
Vol 140 (12) ◽  
Author(s):  
Artur Szymański ◽  
Włodzimierz Wróblewski ◽  
Daniel Frączek ◽  
Krzysztof Bochon ◽  
Sławomir Dykas ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Flow Behavior ◽  
High Capacity ◽  
Labyrinth Seal ◽  
Response Surfaces ◽  
Test Rig ◽  
Substantial Impact ◽  
Screening Algorithm ◽  
Wide Range ◽  
Sst Turbulence Model

This paper presents the methodology and results of the optimization of a straight-through labyrinth seal with two inclined fins against smooth-land. The optimization was performed using commercial tools implemented in the ANSYS environment, such as goal-driven optimization. The response surfaces were created based on Latin hypercube samples found from computational fluid dynamics (CFD) calculations. The CFD solver, using a steady-state scheme with the k–ω shear stress transport (SST) turbulence model, was applied. A screening algorithm was used to find the best candidates on the response surfaces. The objective function adopted in the labyrinth seal optimization was the minimization of the discharge coefficient value. A wide range of parameters of the fins position and shape were taken into account, with physically justified degrees-of-freedom. The optimization results were supported by the results of an in-house experiment performed on a stationary, linear test rig. The test rig was fed by a high-capacity vacuum air blower with high-precision hot-wire anemometry mass flow evaluation. The reductions in the leakage significantly exceed the uncertainties of the CFD model and the test rig accuracy. The factors that had the most substantial impact on the leakage reduction were the location, inclination, and thickness of the fins. The experimental results were compared with the calculations and the optimization effects, highlighting some tendencies in the labyrinth seal flow behavior. Good agreement was obtained between the optimization results and the experimental data, proving that the presented methodology is sufficient for the labyrinth seal optimization.

Experimental and Numerical Investigations on Basic Characteristics of High-Performance Abradable-Aero Hybrid Seal

2014 ◽  
Author(s):  
Yoshihiro Kuwamura ◽  
Kazuyuki Matsumoto ◽  
Hidekazu Uehara ◽  
Hiroharu Ooyama ◽  
Yoshinori Tanaka ◽  
...  
Keyword(s):  
Mass Flow ◽  
Vortex Structure ◽  
High Performance ◽  
Discharge Coefficient ◽  
Labyrinth Seal ◽  
Axial Position ◽  
Leakage Flow ◽  
Flow Measurements ◽  
Wide Range ◽  
Basic Characteristics

As key technologies to improve the performance of steam turbines, various types of high performance seal, such as active clearance control (ACC) seals and leaf seals [1], have been developed by Mitsubishi Heavy Industries, LTD (MHI). In recent years, a new seal concept using an aerodynamic approach called “aero seal” has also been developed, which remarkably reduces the leakage flow while maintaining fin clearances. Furthermore, more robust and higher performance sealing technology called “abradable-aero hybrid seal” which combines the aero seal concept with the abradable seal technology was proposed. The main concept of the aero seal is to control and utilize the vortex structure in the cavities of the labyrinth seal. In the cavities of the aero seal, the locally-controlled flow on the upstream side of the fin tip causes a strong contraction of the leakage flow and reduces the discharge coefficient significantly. This concept allows for a remarkably reduced leakage flow while maintaining fin clearances. Moreover, in order to achieve more robust and higher performance by minimizing the fin clearances, the abradable seal technology was applied to the aero seal concept. However, when the abradable seal is applied, the grooves may be formed on the wall surface of the abradable material due to rubbing of the fin into the abradable material. This situation leads to concern that the groove breaks the effective vortex structure of aero seal and causes negative effects on the seal performance. In this paper, the improved aero seal configuration consisting of slant fins was proposed and it was verified that the reduction in the discharge coefficient of improved aero seal is up to 40% compared to the conventional labyrinth seal. Furthermore, more robust and higher performance sealing technology called “abradable-aero hybrid seal” was proposed and basic characteristics such as the effects of the presence of grooves, the axial position of the fin and seal clearance on the leakage mass flow and the vortex structure were parametrically investigated both experimentally and numerically. In the experiments, not only leakage mass flow measurements but also PIV measurements were carried out in order to visualize the flow patterns in the cavity of the abradable-aero hybrid seal. From the results, it was confirmed that the effective vortex structures were formed even with grooves at various fin positions and the leakage flow can be stably reduced over 40% in a wide range of axial position and reduced by 50% at the optimum position.

scholarly journals Measuring system for comprehensive testing of electrical machines

2020 ◽  
Vol 69 (1) ◽  
pp. 35-56
Author(s):  
Adam Biernat ◽  
Włodzimierz Przyborowski
Keyword(s):  
Experimental Testing ◽  
Electric Machines ◽  
Electrical Machines ◽  
Measuring System ◽  
Machine Construction ◽  
Signal Acquisition ◽  
State Variables ◽  
Measuring Systems ◽  
Wide Range ◽  
Different Characteristics

The article presents a measuring system designed for a comprehensive experimental testing of various types of electric machines. These tests include measurements of electrical, electromagnetic, kinematic, as well as mechanical and thermal quantities. The basic measurements of electrical machines include currents and voltages in electrical circuits, including voltages on resistive and generally impedance elements of these circuits, and induced voltages. Depending on the machine class and type, the measured values are constant or change over time. Some magnitudes of electromagnetic transformations are measured in the area of machine construction. In addition, the parameters of the measured values of the type of signal discriminants (average, effective and maximum values) and their waveforms are presented. Due to the wide range of machine state parameters, i.e. its state variables - in different load states, the multiplicity of these signals and the need to know their different characteristics, it becomes necessary to use individually adopted signal processing subsystems, i.e. signal acquisition systems, in the measuring systems. It is now possible thanks to the development in the CAM (Computer Aided Measurement) programming, for example using the graphical programming language of the integrated LabVIEW system. The article also presents examples of subsystems for the acquisition of measurements of nonelectromagnetic signals like vibrational and acoustic ones generated in machines. Keywords: electric machines, measurements, measuring system

Mixed Helical Labyrinth Groove Seal Optimization Using Computational Fluid Dynamics

2017 ◽  
Author(s):  
Wisher Paudel ◽  
Cori Watson ◽  
Houston G. Wood
Keyword(s):  
Kinetic Energy ◽  
Regression Models ◽  
Labyrinth Seal ◽  
Response Surfaces ◽  
Design Parameters ◽  
Labyrinth Seals ◽  
Ansys Cfx ◽  
Helical Groove ◽  
Groove Seal ◽  
Annular Seals

Non-contacting annular seals are used in rotating machinery to reduce the flow of fluid across a pressure differential. Helical and labyrinth groove seals are two types of non-contacting annular seals frequently used between the impeller stages in a pump. Labyrinth seals have circumferential grooves cut into the surface of the rotor, the stator, or both. They function to reduce leakage by dissipating kinetic energy as fluid expands in the grooves and then is forced to contract in the jet stream region. Helical groove seals have continuously cut grooves in either or both of the rotor and stator surfaces. Like labyrinth seals, they reduce leakage through dissipation of kinetic energy, but have the added mechanism of functioning as a pump to push the fluid back towards the high pressure region as it tries to escape. Previous work has shown that both labyrinth and helical groove seals with grooves on both the rotor and the stator have lower leakage than seals with grooves on just one surface. The goal of this work is to analyze seals with helical grooves on one surface and labyrinth grooves on the other. Designs for both helical stator, labyrinth rotor and labyrinth stator, helical rotor will be simulated and the performance of each configuration will be compared. The primary variables considered for the designs of the seals include the width, depth, and the number of grooves for labyrinth seal and the width, depth, and the angle of the grooves for helical. The designs to simulate will be chosen using a Kennard-stone algorithm to optimally space them within the design space. Then, for both configurations, multi-factor quadratic regression models will be generated. Backward regression will be used to reduce the models to only statistically significant design parameters. From there, the response surfaces will be created to demonstrate the effects of each design parameter on the performance of the seal. Finally, optimal designs will be produced based on the regression models. These designs will be simulated to show the predictive power of the regression models. The simulations for this work will be run in ANSYS CFX for each seal type and configuration will be used to compare solutions for the two different types of designs to previous studies. The findings from this study is expected to show substantial decrease in leakage for a mixed helical-labyrinth seal in comparison to the seal with either helical or labyrinth grooves on both surfaces and thus will provide useful results needed to minimize amount of leakage and therefore improve the efficiency of the machine.

scholarly journals Quantification of assembly forces during creation of head-neck taper junction considering soft tissue bearing: a biomechanical study

Arthroplasty ◽  
2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Toni Wendler ◽  
Torsten Prietzel ◽  
Robert Möbius ◽  
Jean-Pierre Fischer ◽  
Andreas Roth ◽  
...  
Keyword(s):  
Soft Tissue ◽  
Work Experience ◽  
Soft Tissues ◽  
Force Sensor ◽  
Biomechanical Study ◽  
Measuring System ◽  
Wide Range ◽  
Head Neck

Abstract Background All current total hip arthroplasty (THA) systems are modular in design. Only during the operation femoral head and stem get connected by a Morse taper junction. The junction is realized by hammer blows from the surgeon. Decisive for the junction strength is the maximum force acting once in the direction of the neck axis, which is mainly influenced by the applied impulse and surrounding soft tissues. This leads to large differences in assembly forces between the surgeries. This study aimed to quantify the assembly forces of different surgeons under influence of surrounding soft tissue. Methods First, a measuring system, consisting of a prosthesis and a hammer, was developed. Both components are equipped with a piezoelectric force sensor. Initially, in situ experiments on human cadavers were carried out using this system in order to determine the actual assembly forces and to characterize the influence of human soft tissues. Afterwards, an in vitro model in the form of an artificial femur (Sawbones Europe AB, Malmo, Sweden) with implanted measuring stem embedded in gelatine was developed. The gelatine mixture was chosen in such a way that assembly forces applied to the model corresponded to those in situ. A study involving 31 surgeons was carried out on the aforementioned in vitro model, in which the assembly forces were determined. Results A model was developed, with the influence of human soft tissues being taken into account. The assembly forces measured on the in vitro model were, on average, 2037.2 N ± 724.9 N, ranging from 822.5 N to 3835.2 N. The comparison among the surgeons showed no significant differences in sex (P = 0.09), work experience (P = 0.71) and number of THAs performed per year (P = 0.69). Conclusions All measured assembly forces were below 4 kN, which is recommended in the literature. This could lead to increased corrosion following fretting in the head-neck interface. In addition, there was a very wide range of assembly forces among the surgeons, although other influencing factors such as different implant sizes or materials were not taken into account. To ensure optimal assembly force, the impaction should be standardized, e.g., by using an appropriate surgical instrument.

scholarly journals Mass and Heat Transfer Coefficients in Automotive Exhaust Catalytic Converter Channels

Catalysts ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 507
Author(s):  
Chrysovalantis C. Templis ◽  
Nikos G. Papayannakos
Keyword(s):  
Heat Transfer ◽  
Flow Reactor ◽  
Catalytic Converter ◽  
Reaction Rates ◽  
Cfd Model ◽  
Automotive Exhaust ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Wide Range ◽  
Mass And Heat Transfer

Mass and heat transfer coefficients (MTC and HTC) in automotive exhaust catalytic monolith channels are estimated and correlated for a wide range of gas velocities and prevailing conditions of small up to real size converters. The coefficient estimation is based on a two dimensional computational fluid dynamic (2-D CFD) model developed in Comsol Multiphysics, taking into account catalytic rates of a real catalytic converter. The effect of channel size and reaction rates on mass and heat transfer coefficients and the applicability of the proposed correlations at different conditions are discussed. The correlations proposed predict very satisfactorily the mass and heat transfer coefficients calculated from the 2-D CFD model along the channel length. The use of a one dimensional (1-D) simplified model that couples a plug flow reactor (PFR) with mass transport and heat transport effects using the mass and heat transfer correlations of this study is proved to be appropriate for the simulation of the monolith channel operation.

scholarly journals Plasmonic semiconductor nanogroove array enhanced broad spectral band millimetre and terahertz wave detection

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Jinchao Tong ◽  
Fei Suo ◽  
Tianning Zhang ◽  
Zhiming Huang ◽  
Junhao Chu ◽  
...  
Keyword(s):  
Surface Plasmon ◽  
High Performance ◽  
Room Temperature ◽  
Spectral Band ◽  
High Capacity ◽  
Terahertz Wave ◽  
Semiconductor Surface ◽  
Wide Range ◽  
Low Sensitivity ◽  
Air Interfaces

AbstractHigh-performance uncooled millimetre and terahertz wave detectors are required as a building block for a wide range of applications. The state-of-the-art technologies, however, are plagued by low sensitivity, narrow spectral bandwidth, and complicated architecture. Here, we report semiconductor surface plasmon enhanced high-performance broadband millimetre and terahertz wave detectors which are based on nanogroove InSb array epitaxially grown on GaAs substrate for room temperature operation. By making a nanogroove array in the grown InSb layer, strong millimetre and terahertz wave surface plasmon polaritons can be generated at the InSb–air interfaces, which results in significant improvement in detecting performance. A noise equivalent power (NEP) of 2.2 × 10−14 W Hz−1/2 or a detectivity (D*) of 2.7 × 1012 cm Hz1/2 W−1 at 1.75 mm (0.171 THz) is achieved at room temperature. By lowering the temperature to the thermoelectric cooling available 200 K, the corresponding NEP and D* of the nanogroove device can be improved to 3.8 × 10−15 W Hz−1/2 and 1.6 × 1013 cm Hz1/2 W−1, respectively. In addition, such a single device can perform broad spectral band detection from 0.9 mm (0.330 THz) to 9.4 mm (0.032 THz). Fast responses of 3.5 µs and 780 ns are achieved at room temperature and 200 K, respectively. Such high-performance millimetre and terahertz wave photodetectors are useful for wide applications such as high capacity communications, walk-through security, biological diagnosis, spectroscopy, and remote sensing. In addition, the integration of plasmonic semiconductor nanostructures paves a way for realizing high performance and multifunctional long-wavelength optoelectrical devices.

scholarly journals Prototype Design and Experimental Evaluation of Autonomous Collaborative Communication System for Emerging Maritime Use Cases

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3871
Author(s):  
Jiri Pokorny ◽  
Khanh Ma ◽  
Salwa Saafi ◽  
Jakub Frolka ◽  
Jose Villa ◽  
...  
Keyword(s):  
Communication System ◽  
Autonomous Vehicles ◽  
High Speed ◽  
High Capacity ◽  
Workplace Safety ◽  
Unmanned Vehicles ◽  
Use Cases ◽  
Automated Systems ◽  
Collaborative Communication ◽  
Wide Range

Automated systems have been seamlessly integrated into several industries as part of their industrial automation processes. Employing automated systems, such as autonomous vehicles, allows industries to increase productivity, benefit from a wide range of technologies and capabilities, and improve workplace safety. So far, most of the existing systems consider utilizing one type of autonomous vehicle. In this work, we propose a collaboration of different types of unmanned vehicles in maritime offshore scenarios. Providing high capacity, extended coverage, and better quality of services, autonomous collaborative systems can enable emerging maritime use cases, such as remote monitoring and navigation assistance. Motivated by these potential benefits, we propose the deployment of an Unmanned Surface Vehicle (USV) and an Unmanned Aerial Vehicle (UAV) in an autonomous collaborative communication system. Specifically, we design high-speed, directional communication links between a terrestrial control station and the two unmanned vehicles. Using measurement and simulation results, we evaluate the performance of the designed links in different communication scenarios and we show the benefits of employing multiple autonomous vehicles in the proposed communication system.

On LES Methods Applied to Seal Geometries

2012 ◽  
Author(s):  
James Tyacke ◽  
Richard Jefferson-Loveday ◽  
Paul Tucker
Keyword(s):  
Maximum Error ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Final Solution ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Wide Range ◽  
Large Eddy ◽  
Rans Models ◽  
Flow Through

Nine Large Eddy Simulation (LES) methods are used to simulate flow through two labyrinth seal geometries and are compared with a wide range of Reynolds-Averaged Navier-Stokes (RANS) solutions. These involve one-equation, two-equation and Reynolds Stress RANS models. Also applied are linear and nonlinear pure LES models, hybrid RANS-Numerical-LES (RANS-NLES) and Numerical-LES (NLES). RANS is found to have a maximum error and a scatter of 20%. A similar level of scatter is also found among the same turbulence model implemented in different codes. In a design context, this makes RANS unusable as a final solution. Results show that LES and RANS-NLES is capable of accurately predicting flow behaviour of two seals with a scatter of less than 5%. The complex flow physics gives rise to both laminar and turbulent zones making most LES models inappropriate. Nonetheless, this is found to have minimal tangible results impact. In accord with experimental observations, the ability of LES to find multiple solutions due to solution non-uniqueness is also observed.

Compressor Performance and Operability in Swirl Distortion

2010 ◽  
Author(s):  
Yogi Sheoran ◽  
Bruce Bouldin ◽  
P. Murali Krishnan
Keyword(s):  
Gas Turbine ◽  
Complex Geometry ◽  
Full Range ◽  
Axial Compressor ◽  
Cfd Model ◽  
Generator System ◽  
Sliding Mesh ◽  
Wide Range ◽  
Compressor Performance ◽  
The Impact

Inlet swirl distortion has become a major area of concern in the gas turbine engine community. Gas turbine engines are increasingly installed with more complicated and tortuous inlet systems, like those found on embedded installations on Unmanned Aerial Vehicles (UAVs). These inlet systems can produce complex swirl patterns in addition to total pressure distortion. The effect of swirl distortion on engine or compressor performance and operability must be evaluated. The gas turbine community is developing methodologies to measure and characterize swirl distortion. There is a strong need to develop a database containing the impact of a range of swirl distortion patterns on a compressor performance and operability. A recent paper presented by the authors described a versatile swirl distortion generator system that produced a wide range of swirl distortion patterns of a prescribed strength, including bulk swirl, twin swirl and offset swirl. The design of these swirl generators greatly improved the understanding of the formation of swirl. The next step of this process is to understand the effect of swirl on compressor performance. A previously published paper by the authors used parallel compressor analysis to map out different speed lines that resulted from different types of swirl distortion. For the study described in this paper, a computational fluid dynamics (CFD) model is used to couple upstream swirl generator geometry to a single stage of an axial compressor in order to generate a family of compressor speed lines. The complex geometry of the analyzed swirl generators requires that the full 360° compressor be included in the CFD model. A full compressor can be modeled several ways in a CFD analysis, including sliding mesh and frozen rotor techniques. For a single operating condition, a study was conducted using both of these techniques to determine the best method given the large size of the CFD model and the number of data points that needed to be run to generate speed lines. This study compared the CFD results for the undistorted compressor at 100% speed to comparable test data. Results of this study indicated that the frozen rotor approach provided just as accurate results as the sliding mesh but with a greatly reduced cycle time. Once the CFD approach was calibrated, the same techniques were used to determine compressor performance and operability when a full range of swirl distortion patterns were generated by upstream swirl generators. The compressor speed line shift due to co-rotating and counter-rotating bulk swirl resulted in a predictable performance and operability shift. Of particular importance is the compressor performance and operability resulting from an exposure to a set of paired swirl distortions. The CFD generated speed lines follow similar trends to those produced by parallel compressor analysis.

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