scholarly journals A novel 4-sensor fast-response aerodynamic probe for non-isotropic turbulence measurement in turbomachinery flows

2018 ◽  
Vol 2 ◽  
pp. UALS07 ◽  
Author(s):  
Alexandros C. Chasoglou ◽  
Michel Mansour ◽  
Anestis I. Kalfas ◽  
Reza S. Abhari
Keyword(s):  
Isotropic Turbulence ◽  
Three Dimensional ◽  
Fast Response ◽  
Turbulent Structures ◽  
Turbulence Measurement ◽  
Time Resolved ◽  
Accuracy Comparison ◽  
Degree Of Anisotropy ◽  
Current Article ◽  
High Degree

Abstract In modern computational studies for turbomachinery applications, time, length scales and isotropy of turbulent structures are important for representative modelling. To this end, experimental data are essential to validate the numerical tools. The current article presents the development and application of a newly designed 4-sensor Fast Response Aerodynamic Probe (FRAP-4S) enabling time-resolved measurement of the three-dimensional unsteady flow velocity vector in turbomachines. The miniature multi-sensor probe demonstrates a 4 mm probe-tip. In the first part of this article the design, manufacturing and calibration results of the FRAP-4S are presented in detail. To assess the newly developed probe accuracy, comparison against traditional instrumentation developed at the Laboratory for Energy Conversion is also provided. In the second part of this work, measurements are performed at the rotor exit of a one-and-a-half stage, unshrouded and highly-loaded axial turbine configuration. The results showed increased level of unsteadiness and turbulence levels with peak-to-peak fluctuation from 5 to 35%. More importantly, in some regions stream-wise unsteadiness was found to be ten times higher, compared to the cross-wise components, an indication of the high degree of anisotropy.

Electrophoretic Deposition of Metal Nanoparticle Monolayers from Nonpolar Solvents for Hydrogen Sensing

2015 ◽  
Vol 654 ◽  
pp. 213-217 ◽  
Author(s):  
Jan Grym ◽  
Roman Yatskiv ◽  
Ondřej Černohorský ◽  
María Verde ◽  
Jan Lorinčík ◽  
...  
Keyword(s):  
Electrophoretic Deposition ◽  
Reverse Micelles ◽  
Three Dimensional ◽  
Fast Response ◽  
Metal Nanoparticle ◽  
Hydrogen Sensors ◽  
Hydrogen Sensing ◽  
Nonpolar Solvents ◽  
Dimensional Growth ◽  
High Degree

We report on the electrophoretic deposition (EPD) of metal nanoparticles (NPs) prepared in reverse micelles on semiconductor substrates with the aim to fabricate sensitive Schottky-based hydrogen sensors with fast response and high degree of selectivity. We discuss the mechanism of NP monolayer formation and show which parameters are essential for the transition from three-dimensional to two-dimensional growth.

Three Dimensional Clocking Effects in a One and a Half Stage Transonic Turbine

2009 ◽  
Vol 132 (1) ◽  
Author(s):  
O. Schennach ◽  
J. Woisetschläger ◽  
B. Paradiso ◽  
G. Persico ◽  
P. Gaetani
Keyword(s):  
Flow Field ◽  
Three Dimensional ◽  
Fast Response ◽  
Secondary Flows ◽  
Pressure Probe ◽  
Time Resolved ◽  
Flow Angle ◽  
Aerodynamic Pressure ◽  
Velocity Flow ◽  
Transonic Turbine

This paper presents an experimental investigation of the flow field in a high-pressure transonic turbine with a downstream vane row (1.5 stage machine) concerning the airfoil indexing. The objective is a detailed analysis of the three-dimensional aerodynamics of the second vane for different clocking positions. To give an overview of the time-averaged flow field, five-hole probe measurements were performed upstream and downstream of the second stator. Furthermore in these planes additional unsteady measurements were carried out with laser Doppler velocimetry in order to record rotor phase-resolved velocity, flow angle, and turbulence distributions at two different clocking positions. In the planes upstream of the second vane, the time-resolved pressure field has been measured by means of a fast response aerodynamic pressure probe. This paper shows that the secondary flows of the second vane are significantly modified by the different clocking positions, in connection with the first vane modulation of the rotor secondary flows. An analysis of the performance of the second vane is also carried out, and a 0.6% variation in the second vane loss coefficient has been recorded among the different clocking positions.

Unsteady Aerodynamics of a Low Aspect Ratio Turbine Stage: Modeling Issues and Flow Physics

2012 ◽  
Vol 134 (6) ◽  
Author(s):  
G. Persico ◽  
A. Mora ◽  
P. Gaetani ◽  
M. Savini
Keyword(s):  
Aspect Ratio ◽  
Coming Out ◽  
Three Dimensional ◽  
Unsteady Aerodynamics ◽  
Fast Response ◽  
Operating Conditions ◽  
Pressure Probe ◽  
Turbine Stage ◽  
Time Resolved ◽  
Low Aspect Ratio

In this paper the three-dimensional unsteady aerodynamics of a low aspect ratio, high pressure turbine stage are studied. In particular, the results of fully unsteady three-dimensional numerical simulations, performed with ANSYS-CFX, are critically evaluated against experimental data. Measurements were carried out with a novel three-dimensional fast-response pressure probe in the closed-loop test rig of the Laboratorio di Fluidodinamica delle Macchine of the Politecnico di Milano. An analysis is first reported about the strategy to limit the CPU and memory requirements while performing three-dimensional simulations of blade row interaction when the rotor and stator blade numbers are prime to each other. What emerges as the best choice is to simulate the unsteady behavior of the rotor alone by applying the stator outlet flow field as a rotating inlet boundary condition (scaled on the rotor blade pitch). Thanks to the reliability of the numerical model, a detailed analysis of the physical mechanisms acting inside the rotor channel is performed. Two operating conditions at different vane incidence are considered, in a configuration where the effects of the vortex-blade interaction are highlighted. Different vane incidence angles lead to different size, position, and strength of secondary vortices coming out from the stator, thus promoting different interaction processes in the subsequent rotor channel. However some general trends can be recognized in the vortex-blade interaction: the sense of rotation and the spanwise position of the incoming vortices play a crucial role on the dynamics of the rotor vortices, determining both the time-mean and the time-resolved characteristics of the secondary field at the exit of the stage.

Time-Resolved Near-Wake Measurements of a 2MW Wind Turbine

2013 ◽  
Author(s):  
Michel Mansour ◽  
Caglar Atalayer ◽  
Ndaona Chokani ◽  
Reza Abhari
Keyword(s):  
Wind Turbine ◽  
Real Time ◽  
Three Dimensional ◽  
Pressure Sensors ◽  
Fast Response ◽  
Near Wake ◽  
Time Resolved ◽  
Wind Speeds ◽  
Ultrasonic Anemometer ◽  
Yaw Angle

This paper presents time-resolved velocity measurements performed in the near wake of a multi-megawatt wind turbine, using a novel nacelle-mounted fast-response aerodynamic probe. The aerodynamic probe, which has been developed at ETH Zurich, consists of a hemispherical 5-hole probe equipped with fast-pressure sensors. The probe has a measurement uncertainty of ±0.1m/s and a measurement bandwidth of 65Hz. In addition to measurement of the three-dimensional wind velocity vector, the probe is instrumented for the real-time monitoring of meteorological conditions. The measured data are processed in real-time, stored on on-board and accessible via a GPRS modem. As the aerodynamic probe is installed adjacent to the wind turbine’s ultrasonic anemometer, the measurements of the two systems can be compared. The measured wind speeds are found to be in very good agreement and remains on an averaged within ±0.24m/s deviation to the ultrasonic anemometer. The measured yaw angle shows an average offset of −7.5°. This difference is observed since the ultrasonic anemometer does not accurately capture the turning of the flow across the wind turbine’s rotor. From the time-resolved measurements of the aerodynamic probe, the phase-lock averaged measurements show that over one blade passing period the turbulence intensity varies from 13 to 24%, with a maximum degree of anisotropy above 1.4. It is found that a hub passage vortex, which extends over more than 50% of the blade passage width, is present. Thus, from a turbine control perspective the actual placement of the ultrasonic anemometer, even when corrected, can lead to high yaw angle misalignment when the wind turbine is located in moderately or highly complex terrain.

The Dynamics of the Vorticity Field in a Low Solidity Axial Turbine

2008 ◽  
Author(s):  
K. G. Barmpalias ◽  
A. I. Kalfas ◽  
N. Chokani ◽  
R. S. Abhari
Keyword(s):  
Current Trend ◽  
Three Dimensional ◽  
Fast Response ◽  
Secondary Flows ◽  
Vorticity Field ◽  
Time Resolved ◽  
Axial Turbine ◽  
Unsteady Interaction ◽  
Vorticity Transport ◽  
Highly Loaded

A current trend in turbomachinery design is the use of low solidity axial turbines that can generate a given power with fewer blades. However, due to the higher turning of the flow, relative to a high solidity turbine, there is an increase in secondary flows and their associated losses. In order to increase the efficiency of these more highly loaded stages, an improved understanding of the mechanisms related to the development, evolution and unsteady interaction of the secondary flows is required. An experimental investigation of the unsteady vorticity field in highly loaded stages of a research turbine is presented here. The research turbine facility is equipped with a two-stage axial turbine that is representative of the high-pressure section of a steam turbine. Steady and unsteady area measurements are performed, with the use of miniature pneumatic and fast response aerodynamic probes, in closely spaced planes at the exits of each blade row. In addition to the 3D total pressure flowfield, the multi-plane measurements allow the full three-dimensional time-resolved vorticity and velocity fields to be determined. These measurements are then used to describe the development, evolution and unsteady interaction of the secondary flows and loss generation. Particular emphasis is given to the vortex stretching term of the vorticity transport equation, which gives new insight into the vortex tilting and stretching that is associated with the secondary loss generation.

Unsteady, 3-Dimensional Flow Measurement Using a Miniature Virtual 4 Sensor Fast Response Aerodynamic Probe (FRAP)

2003 ◽  
Author(s):  
A. Pfau ◽  
J. Schlienger ◽  
A. I. Kalfas ◽  
R. S. Abhari
Keyword(s):  
Three Dimensional ◽  
Fast Response ◽  
Outer Diameter ◽  
Three Dimensional Flow ◽  
Flow Measurements ◽  
Time Resolved ◽  
3 Dimensional ◽  
Dimensional Flow ◽  
Sensor Probe ◽  
Probe Head

This paper introduces the new fast response aerodynamic probe, which was recently developed at the ETH Zurich. The technique provides time-resolved, three-dimensional flow measurements using the virtual four sensor technique. The concept and the evaluation of the virtual four sensor probe is discussed in detail. The basic results consist of yaw and pitch flow angles as well as the total and static pressure. They combine to form the unsteady, three dimensional flow vector. The outer diameter of the cylindrical probe head was miniaturized to 0.84mm, hence probe blockage effects as well as dynamic lift effects are reduced. The shape of the probe head was optimized in view of the manufacturing process as well as aerodynamic considerations. The optimum geometry for pitch sensitivity was found to be a cylindrical surface with the axis perpendicular to the probe shaft. The internal design of the probes led to a sensor cavity eigenfrequency of 44kHz for the yaw sensitive and 34kHz for the pitch sensitive probe. Data acquisition is done with a fully automated traversing system, which moves the probe within the test rig and samples the signal with a PC-based A/D-board. An error analysis implemented into the data reduction routines revealed acceptable accuracy for flow angles as well as pressures for many turbomachinery flows. Depending on the dynamic head of the application the yaw angle is accurate within ±0.35° and pitch angle within ±0.7°. In the final section, a comparison of time averaged results to five hole probe measurements is discussed. The advantages of the new probe, beside its unique smallness, are the complete unsteady kinematic information and the improved recording of unsteady total pressure measurement as it is pointed out in a comparison against a 2D virtual three sensor probe.

Operational Model and its Validation with Drift Tests in Water Areas Around the Baltic Sea

1994 ◽  
Vol 29 (2-3) ◽  
pp. 293-308
Author(s):  
J. Koponen ◽  
M. Virtanen ◽  
H. Vepsä ◽  
E. Alasaarela
Keyword(s):  
Three Dimensional ◽  
Fast Response ◽  
Velocity Measurements ◽  
Short Term ◽  
Large Lakes ◽  
Operational Model ◽  
Water Currents ◽  
Emergency Situations ◽  
Sensitivity Tests ◽  
The Baltic

Abstract Three-dimensional (3-D) mathematical models of water currents, transport, mixing, reaction kinetic, and interactions with bottom and air have been used in Finland regularly since 1982 and applied to about 40 cases in large lakes, inland seas and their coastal waters. In each case, model validity has been carefully tested with available flow velocity measurements, tracer studies and water quality observations. For operational use, i.e., for spill combatting and sea rescue, the models need fast response, proven validity and illustrative visualization. In 1987-90, validated models were implemented for operational use at five sea areas along the Finnish coast. Further validation was obtained in model applications from nine documented or arranged cases and from seven emergency situations. Sensitivity tests supplement short-term validation. In the Bothnian Sea, it was nescessary to start the calculation of water currents three days prior to the start of the experiment to reduce initial inaccuracies and to make the coastal transport estimates meaningful.

scholarly journals A 3D hydrodynamic flow-focusing device for cell sorting

2021 ◽  
Vol 25 (3) ◽  
Author(s):  
Xiaofei Yuan ◽  
Andrew Glidle ◽  
Hitoshi Furusho ◽  
Huabing Yin
Keyword(s):  
Cell Sorting ◽  
Control Strategies ◽  
Three Dimensional ◽  
Hydrodynamic Flow ◽  
Proof Of Concept ◽  
Flow Focusing ◽  
Hydrodynamic Focusing ◽  
Cell Handling ◽  
Fluid Flow Control ◽  
High Degree

AbstractOptical-based microfluidic cell sorting has become increasingly attractive for applications in life and environmental sciences due to its ability of sophisticated cell handling in flow. The majority of these microfluidic cell sorting devices employ two-dimensional fluid flow control strategies, which lack the ability to manipulate the position of cells arbitrarily for precise optical detection, therefore resulting in reduced sorting accuracy and purity. Although three-dimensional (3D) hydrodynamic devices have better flow-focusing characteristics, most lack the flexibility to arbitrarily position the sample flow in each direction. Thus, there have been very few studies using 3D hydrodynamic flow focusing for sorting. Herein, we designed a 3D hydrodynamic focusing sorting platform based on independent sheath flow-focusing and pressure-actuated switching. This design offers many advantages in terms of reliable acquisition of weak Raman signals due to the ability to precisely control the speed and position of samples in 3D. With a proof-of-concept demonstration, we show this 3D hydrodynamic focusing-based sorting device has the potential to reach a high degree of accuracy for Raman activated sorting.

scholarly journals Comparative Study of Silk Fibroin-Based Hydrogels and Their Potential as Material for 3-Dimensional (3D) Printing

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3887
Author(s):  
Watcharapong Pudkon ◽  
Chavee Laomeephol ◽  
Siriporn Damrongsakkul ◽  
Sorada Kanokpanont ◽  
Juthamas Ratanavaraporn
Keyword(s):  
3D Printing ◽  
Silk Fibroin ◽  
Biomedical Applications ◽  
Mechanical Stability ◽  
Three Dimensional ◽  
Structure Stability ◽  
3 Dimensional ◽  
Critical Technology ◽  
Box Structure ◽  
High Degree

Three-dimensional (3D) printing is regarded as a critical technology in material engineering for biomedical applications. From a previous report, silk fibroin (SF) has been used as a biomaterial for tissue engineering due to its biocompatibility, biodegradability, non-toxicity and robust mechanical properties which provide a potential as material for 3D-printing. In this study, SF-based hydrogels with different formulations and SF concentrations (1–3%wt) were prepared by natural gelation (SF/self-gelled), sodium tetradecyl sulfate-induced (SF/STS) and dimyristoyl glycerophosphorylglycerol-induced (SF/DMPG). From the results, 2%wt SF-based (2SF) hydrogels showed suitable properties for extrusion, such as storage modulus, shear-thinning behavior and degree of structure recovery. The 4-layer box structure of all 2SF-based hydrogel formulations could be printed without structural collapse. In addition, the mechanical stability of printed structures after three-step post-treatment was investigated. The printed structure of 2SF/STS and 2SF/DMPG hydrogels exhibited high stability with high degree of structure recovery as 70.4% and 53.7%, respectively, compared to 2SF/self-gelled construct as 38.9%. The 2SF/STS and 2SF/DMPG hydrogels showed a great potential to use as material for 3D-printing due to its rheological properties, printability and structure stability.

scholarly journals Picosecond time-resolved photon antibunching measures nanoscale exciton motion and the true number of chromophores

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Gordon J. Hedley ◽  
Tim Schröder ◽  
Florian Steiner ◽  
Theresa Eder ◽  
Felix J. Hofmann ◽  
...  
Keyword(s):  
Rational Design ◽  
Three Dimensional ◽  
Dna Origami ◽  
Fluorescent Nanoparticles ◽  
Time Resolved ◽  
Exciton Diffusion ◽  
Polymer Aggregates ◽  
True Number ◽  
Particle Level ◽  
Photon Antibunching

AbstractThe particle-like nature of light becomes evident in the photon statistics of fluorescence from single quantum systems as photon antibunching. In multichromophoric systems, exciton diffusion and subsequent annihilation occurs. These processes also yield photon antibunching but cannot be interpreted reliably. Here we develop picosecond time-resolved antibunching to identify and decode such processes. We use this method to measure the true number of chromophores on well-defined multichromophoric DNA-origami structures, and precisely determine the distance-dependent rates of annihilation between excitons. Further, this allows us to measure exciton diffusion in mesoscopic H- and J-type conjugated-polymer aggregates. We distinguish between one-dimensional intra-chain and three-dimensional inter-chain exciton diffusion at different times after excitation and determine the disorder-dependent diffusion lengths. Our method provides a powerful lens through which excitons can be studied at the single-particle level, enabling the rational design of improved excitonic probes such as ultra-bright fluorescent nanoparticles and materials for optoelectronic devices.

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