Characterization of Tandem Airfoil Configurations of Axial Compressors

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
Manas M P ◽  
Shine S R
Keyword(s):  
Loss Ratio ◽  
Load Shifting ◽  
Tandem Configuration ◽  
Diffusion Factor ◽  
Axial Compressors ◽  
Cascade Flow ◽  
Gap Ratio ◽  
Loss Parameter ◽  
Performance Behavior

AbstractThe objective of the current study is to investigate the effects of geometric parameters on the fluid flow patterns, diffusion factor, load-split, and off-design performance of the tandem configuration under subsonic, rectilinear, cascade flow. A 2-D computational model using finite volume formulation has been developed and validated against available experimental data. The obtained data is presented in a format involving loss parameter and loading and will help the designer to have sufficient number of combinations within the useful range of application. It is observed that general performance behavior of tandem cascade is similar to a single airfoil data. Load shifting from the front airfoil to the rear airfoil is noted at positive axial overlaps and higher camber ratios. An optimum gap ratio of around 2 is observed for the range of configurations investigated. Contrary to the previous literature, the present study indicates higher loading of the front airfoil for the best overall loading-to-loss ratio of the tandem configuration.

The Impact of Inlet Distortion and Reduced Frequency on the Performance of Centrifugal Compressors

2018 ◽  
Vol 141 (2) ◽  
Author(s):  
A. Grimaldi ◽  
V. Michelassi
Keyword(s):  
Experimental Data ◽  
Liquefied Natural Gas ◽  
Design Phase ◽  
Centrifugal Compressors ◽  
Axial Compressors ◽  
Inlet Distortion ◽  
Side Stream ◽  
Reduced Frequency ◽  
The Impact

This paper discusses the impact of inlet flow distortions on centrifugal compressors based upon a large experimental data base in which the performance of several impellers in a range of corrected flows and corrected speeds have been measured after been coupled with different inlet plenums technologies. The analysis extends to centrifugal compressor inlets including a side stream, typical of liquefied natural gas applications. The detailed measurements allow a thorough characterization of the flow field and associated performance. The results suggest that distortions can alter the head by as much as 3% and efficiency of around 1%. A theoretical analysis allowed to identify the design features that are responsible for this deviation. In particular, an extension of the so-called “reduced-frequency,” a coefficient routinely used in axial compressors and turbine aerodynamics to weigh the unsteadiness generated by upstream to downstream blade rows, allowed to determine a plenum-to-impeller reduced frequency that correlates very well with the measured performance. The theory behind the new coefficient is discussed together with the measurement details and validates the correlation that can be used in the design phase to determine the best compromise between the inlet plenum complexity and impact on the first stage.

Incoming Stall Identification in Axial Compressors by Vibration Analysis

2013 ◽  
Author(s):  
Gianluca D’Elia ◽  
Giorgio Dalpiaz
Keyword(s):  
Vibration Analysis ◽  
Axial Compressor ◽  
Acoustic Signals ◽  
Rotating Stall ◽  
Test Results ◽  
Vibration Signals ◽  
Axial Compressors ◽  
Centrifugal Stage ◽  
Acoustic Characterization

This work addresses on a complete vibro-acoustic characterization of an axial compressor with the aim to foresee the rotor instability. The tests were performed on a turboshaft Allison 250-C18. The compressor is composed of six axial stages and one centrifugal stage. Four vibration signals were simultaneously measured by means of accelerometers, while the acoustic signals were measured by means of two microphones. Two different kinds of tests have been carried out on the compressor that operates at constant speed: in the course of the first test the six signals were acquired at different positions of the throttle opening, whereas during the second test, the signals were acquired while the throttle was gradually opened. The test results show a sensitive increase of the sub-synchronous activity in the accelerometers spectrum map, moreover, closing the throttle, the amplitude of the spectrum components increases. These phenomena can be related to the rotating stall behavior.

Validation and Characterization of an Acoustic Sensor Based on PVDF Micropillars and Patterned Electrodes

2010 ◽  
Author(s):  
Jian Xu ◽  
Marcelo J. Dapino ◽  
Daniel Gallego-Perez ◽  
Derek Hansford
Keyword(s):  
Acoustic Waves ◽  
Polyvinylidene Fluoride ◽  
Notch Filter ◽  
Design Principles ◽  
Pvdf Film ◽  
Acoustic Sensor ◽  
Gap Ratio ◽  
Patterned Electrodes ◽  
The Individual

This paper addresses the fabrication, validation, and characterization of a millimeter-size acoustic sensor consisting of Polyvinylidene Fluoride (PVDF) micropillars and patterned electrodes. The sensor takes advantage of two key design principles: stress amplification through the area ratio between the overall surface exposed to acoustic waves and the area of the individual micropillars, and patterned electrodes which reduce the capacitance of the sensor by excluding the capacitance of the air between micropillars. In combination, these design principles enable a sensor capable of achieving 100× the sensitivity of flat PVDF film. A sensitivity analysis is presented and sensor fabrication details are described. An experimental setup was developed to characterize the sensor against a reference microphone. A signal conditioning circuit including a preamplifier circuit and a notch filter was designed and constructed. Sensitivity calibration tests show that a micropillar array with a gap ratio of 5.82 exhibits a stress constant g33 = −19.93 V/m/Pa, which is 60.39 times greater than the stress constant of commercial PVDF film. Experimental results also show that the sensitivity of the sensor is in close agreement with theory, thus confirming the performance advantages of the micropillar sensor.

The Impact of Inlet Distortion and Reduced Frequency on the Performance of Centrifugal Compressors

2018 ◽  
Author(s):  
A. Grimaldi ◽  
V. Michelassi
Keyword(s):  
Experimental Data ◽  
Liquefied Natural Gas ◽  
Design Phase ◽  
Centrifugal Compressors ◽  
Axial Compressors ◽  
Inlet Distortion ◽  
Side Stream ◽  
Reduced Frequency ◽  
The Impact

This paper discusses the impact of inlet flow distortions on centrifugal compressors based upon a large experimental data base in which the performance of several impellers in a range of corrected flows and corrected speeds have been measured after been coupled with different inlet plenums technologies. The analysis extends to centrifugal compressor inlets including a side stream, typical of Liquefied Natural Gas (LNG) applications. The detailed measurements allow a thorough characterization of the flow field and associated performance. The results suggest that distortions can alter the head by as much as 3% and efficiency of around 1%. A theoretical analysis allowed to identify the design features that are responsible for this deviation. In particular, an extension of the so-called “reduced-frequency”, a coefficient routinely used in axial compressors and turbine aerodynamics to weigh the unsteadiness generated by upstream to downstream blade rows, allowed to determine a plenum-to-impeller reduced frequency that correlates very well with the measured performance. The theory behind the new coefficient is discussed together with the measurement details, and validate the correlation that can be used in the design phase to determine the best compromise between the inlet plenum complexity and impact on the first stage.

scholarly journals Characterization of interaction between electric vehicles and smart grid

2021 ◽  
Vol 237 ◽  
pp. 02004
Author(s):  
Yan Zhang ◽  
Yongxiu He ◽  
Fengyu Su ◽  
Xiaoqing Wang ◽  
Diling Zhang
Keyword(s):  
Smart Grid ◽  
Electric Vehicles ◽  
Economic Benefit ◽  
Power Grid ◽  
Peak Load ◽  
Fluctuation Effect ◽  
Load Shifting ◽  
Significant Fluctuation ◽  
Grid Load

With the development of smart distribution technology in the future, electric vehicle users can not only charge reasonably based on peak-valley price, they can also discharge electricity into the power grid to realize their economic benefit when it’s necessary and thus promote peak load shifting. According to the characteristic that future electric vehicles can discharge, this paper studies the interactive characteristics between electric vehicles and smart grid. In this paper, the example shows that the charging and discharging behaviour of EV users will bring significant fluctuation effect to the power grid load, and the reasonable TOU strategy can stimulate EV users to conduct reasonable charging and discharging, so as to smooth the peak and valley difference of some power grid.

scholarly journals Characterization of Flow Separation around Inline Cylinders within Oscillatory Flow

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Yiding Zhao ◽  
Yao Shi
Keyword(s):  
Vortex Shedding ◽  
Flow Separation ◽  
Oscillatory Flow ◽  
Central Area ◽  
Piv Method ◽  
Influence Area ◽  
Gap Flow ◽  
Gap Ratio ◽  
Flow Motion

This paper has examined the effects of Reynolds number (Re), Keulegan–Carpenter number (KC), and gap ratio on flow separation around a cylinder array by PIV method in experiment. The vortex shedding in such situation occurs each half period of the oscillatory motion from the observation. No matter how many cylinders, KC is the key dominant parameter under low Re that has a great impact on the flow regime and flow motion in oscillatory flows. There is an influence area of vortex shedding around the cylinder. When two inline cylinders are in the flow, smaller gap ratio may extend the influence area of the vortex shedding. For s/d = 2, the vortex shedding that happens in each cylinder has a simultaneity and independence. For s/d = 1.5, the reduced gap ratio leads the upstream shed vortex to interact with downstream cylinder and makes the influence area of vortex shedding around downstream cylinder extends further. For s/d = 1, the interference in the central area is significantly obvious and the vortex shedding is suppressed and even follows the cross gap flow.

scholarly journals Analyse of Measurement Based Admission Control Methods in IMS Networks and Simulation Principle

2018 ◽  
Vol 210 ◽  
pp. 03003
Author(s):  
Erik Chromy ◽  
Tomas Simoncik ◽  
Marek Holiencin ◽  
Ivan Baronak
Keyword(s):  
Admission Control ◽  
Control Method ◽  
Time Window ◽  
Ip Multimedia Subsystem ◽  
Control Methods ◽  
Loss Ratio ◽  
Traffic Measurement ◽  
Qos Parameters ◽  
Loss Parameter

This paper deals with the quality of service in IP Multimedia Subsystem networks. The evaluation of Quality o Service (QoS) is done through admission control methods. We analyse various methods, which are based on the traffic measurement. The approach that can be applied in finding the suitable admission control method while considering selected QoS parameters is described. Different important QoS parameters can be defined, however we decided to focus on the loss parameter. In our simulations we have used Simple Sum method. Based on the simulation results, we have used new algorithm. The main difference is that it uses the mechanism of time window for achieving more accurate traffic estimate. Algorithm Measured Sum with implementation of time window T has better ability to predict the traffic fluctuation. Compared to the Simple Sum algorithm it achieves lower link utilisation, but also lower level of loss ratio.

scholarly journals The Effect of Trailing Edge Clearance in Suppressing Hub-Corner Stall

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 256
Author(s):  
Wenfeng Zhao ◽  
Qun Zheng ◽  
Adil Malik ◽  
Bin Jiang
Keyword(s):  
Flow Separation ◽  
Dominant Role ◽  
Constant Flow ◽  
Trailing Edge ◽  
Flow Area ◽  
Diffusion Factor ◽  
High Loss ◽  
Axial Compressors ◽  
Transverse Pressure ◽  
The Stability

Hub corner is a high-loss area located within in the blade passages of turbomachinery. It is well known that flow separation and vortex development in this area directly affects, not only energy loss and efficiency, but also the stability of axial compressors. In this paper, a high diffusion factor cascade is used in order to analyze the vortex structure which causes the hub-corner stall in cascade. The trailing edge clearance method is proposed for controlling the hub-boundary layer and this is compared with full uniform clearance. Our research highlights that the trailing edge clearance suppress the radial development of the suction separation vortex (SSV) in the hub corner and restrains the concentrated separation vortex (CSV). The influence of trailing edge clearance parameters and its effect on control of hub-corner stall is discussed in detail. It is revealed that clearance height avoids flow separation and suppresses radial vortex development, while the clearance length resists the overturning that is caused by transverse pressure gradient and controls the development of CSV. As the radial vortex plays a dominant role in hub-corner stall, clearance height has a better effect in controlling hub-corner stall in comparison to length at the constant flow area.

Morphological Characterization of Mycobacteriophage R1

1974 ◽  
Vol 32 ◽  
pp. 254-255
Author(s):  
B. L. Soloff ◽  
T. A. Rado
Keyword(s):  
Carbon Source ◽  
Stationary Phase ◽  
Growth Phase ◽  
Minimal Medium ◽  
Morphological Characterization ◽  
Logarithmic Growth Phase ◽  
Complete Lysis ◽  
Lysogenic Culture ◽  
Logarithmic Growth

Mycobacteriophage R1 was originally isolated from a lysogenic culture of M. butyricum. The virus was propagated on a leucine-requiring derivative of M. smegmatis, 607 leu−, isolated by nitrosoguanidine mutagenesis of typestrain ATCC 607. Growth was accomplished in a minimal medium containing glycerol and glucose as carbon source and enriched by the addition of 80 μg/ ml L-leucine. Bacteria in early logarithmic growth phase were infected with virus at a multiplicity of 5, and incubated with aeration for 8 hours. The partially lysed suspension was diluted 1:10 in growth medium and incubated for a further 8 hours. This permitted stationary phase cells to re-enter logarithmic growth and resulted in complete lysis of the culture.

AEM analysis of crystallization in Ti-based amorphous alloys

1983 ◽  
Vol 41 ◽  
pp. 270-271
Author(s):  
A.R. Pelton ◽  
A.F. Marshall ◽  
Y.S. Lee
Keyword(s):  
Magnetic Properties ◽  
Amorphous Alloys ◽  
Amorphous Materials ◽  
Isothermal Annealing ◽  
Amorphous Matrix ◽  
Nucleation And Growth ◽  
Current Interest ◽  
Amorphous Films ◽  
Electrical And Magnetic Properties

Amorphous materials are of current interest due to their desirable mechanical, electrical and magnetic properties. Furthermore, crystallizing amorphous alloys provides an avenue for discerning sequential and competitive phases thus allowing access to otherwise inaccessible crystalline structures. Previous studies have shown the benefits of using AEM to determine crystal structures and compositions of partially crystallized alloys. The present paper will discuss the AEM characterization of crystallized Cu-Ti and Ni-Ti amorphous films.Cu60Ti40: The amorphous alloy Cu60Ti40, when continuously heated, forms a simple intermediate, macrocrystalline phase which then transforms to the ordered, equilibrium Cu3Ti2 phase. However, contrary to what one would expect from kinetic considerations, isothermal annealing below the isochronal crystallization temperature results in direct nucleation and growth of Cu3Ti2 from the amorphous matrix.

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