An Experimental Investigation of the Dynamics of a Blade With Two Under-Platform Dampers

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Daniele Botto ◽  
Chiara Gastadi ◽  
Muzio M. Gola ◽  
Muhammad Umer
Keyword(s):  
Tangential Force ◽  
Turbine Blades ◽  
Relative Displacement ◽  
Point Of View ◽  
Test Rig ◽  
New Approach ◽  
Ground Support ◽  
The Past ◽  
Force Components ◽  
Blade Frequency

Several experimental apparatuses have been designed in the past to evaluate the effectiveness of under-platform dampers. Most of these experimental setups allow to measure the overall damper efficiency in terms of reduction of vibration amplitude in turbine blades. The experimental data collected with these test rigs do not increase the knowledge about the damper dynamics, and therefore, the uncertainty on the damper behavior remains a big issue. In this paper, a different approach to evaluate the damper–blade interaction has been put forward. A test rig has been purposely designed to accommodate a single blade and two under-platform dampers. One side of each damper is in contact with a ground support specifically designed to measure two independent forces on the damper. In this way, both the normal and the tangential force components in the damper–blade contact can be inferred. Damper kinematics is rebuilt by using the relative displacement measured between damper and blade. This paper describes the concept behind the new approach, shows the details of the new test rig, and discusses the blade frequency response from a new point of view.

An Experimental Investigation of the Dynamic of a Blade With Two Under-Platform Dampers

2017 ◽  
Author(s):  
Daniele Botto ◽  
Muhammad Umer ◽  
Chiara Gastaldi ◽  
Muzio M. Gola
Keyword(s):  
Tangential Force ◽  
Turbine Blades ◽  
Relative Displacement ◽  
Point Of View ◽  
Test Rig ◽  
New Approach ◽  
Ground Support ◽  
Experimental Apparatus ◽  
Force Components ◽  
Blade Frequency

Several experimental apparatus have been designed in the past to evaluate the effectiveness of under-platform dampers. Most of these experimental setups allow to measure the overall damper efficiency in terms of reduction of vibration amplitude in turbine blades. The experimental data collected with these test rigs do not increase the knowledge about the damper dynamics and therefore the uncertainty on the damper behavior remains a big issue. In this paper a different approach to evaluate the damper-blade interaction has been put forward. A test rig has been purposely designed to accommodate a single blade and two under-platform dampers. One side of each damper is in contact with a ground support specifically designed to measure two independent forces on the damper. In this way both the normal and the tangential force components in the damper-blade contact can be inferred. Damper kinematics is rebuilt by using the relative displacement measured between damper and blade. This paper describes the concept behind the new approach, shows the details of the new test rig and discuss the blade frequency response from a new point of view.

scholarly journals Oil Spill Detection and Mapping: A 50-Year Bibliometric Analysis

2020 ◽  
Vol 12 (21) ◽  
pp. 3647
Author(s):  
Rodrigo N. Vasconcelos ◽  
André T. Cunha Lima ◽  
Carlos A. D. Lentini ◽  
Garcia V. Miranda ◽  
Luís F. Mendonça ◽  
...  
Keyword(s):  
Oil Spill ◽  
Remote Sensing Data ◽  
Strong Relationship ◽  
The United States ◽  
Point Of View ◽  
Technological Evolution ◽  
New Approach ◽  
Oil Spill Detection ◽  
The Past ◽  
Access Information

Oil spill detection and mapping (OSPM) is an extremely relevant issue from a scientific point of view due to the environmental impact on coastal and marine ecosystems. In this study, we present a new approach to assess scientific literature for the past 50 years. In this sense, our study aims to perform a bibliometric and network analysis using a literature review on the application of OSPM to assess researchers and trends in this field of science. In methodological terms we used the Scopus base to search for articles in the literature, then we used bibliometric tools to access information and reveal quantifying patterns in this field of literature. Our results suggest that the detection of oil in the sea has undergone a great evolution in the last decades and there is a strong relationship between the technological evolution aimed at detection with the improvement of remote sensing data acquisition methods. The most relevant contributions in this field of science involved countries such as China, the United States, and Canada. We revealed aspects of great importance and interest in OSPM literature using a bibliometric and network approach to give a clear overview of this field’s research trends.

scholarly journals The comparative method for policy studies: the thorny aspects

2019 ◽  
Vol 10 (1) ◽  
pp. 56-67
Author(s):  
Tatiana-Camelia Dogaru Cruceanu
Keyword(s):  
Comparative Research ◽  
Comparative Method ◽  
Policy Research ◽  
Point Of View ◽  
Decision Makers ◽  
Theoretical Point ◽  
Policy Studies ◽  
New Approach ◽  
The Past ◽  
Policy Systems

Abstract Over the past decades, the comparative method has attracted the attention of the theorists, and studies based on this approach have increased in applied policy research. In their daily and strategically policy decisions, the decision makers from local, regional and national levels use more and more the comparative research methods, especially due to interlinked relationship and the need for bench learning and benchmarking practices. The comparative method allows the actors to analyse other experiences, and thus to take decisions more efficient. This is a normal, an inevitable situation, when the unit of analysis is a country, a field of matters or a process where researchers compare cases from empirical or theoretical point of view. The purpose of this paper is to provide a critical view on the capacity of comparative method to foster knowledge in policy studies. The intention is to see and to explore the utility of comparative method for policy studies and policy analysis, since a new approach “evidence-based policymaking” arise, emphasising the importance of using evidence from other political and policy systems.

Numerical and Experimental Estimation of the Turbine Blade Damper Efficiency

2018 ◽  
Author(s):  
Boris Shorr ◽  
Nikolay Serebriakov ◽  
Galina Mel'nikova ◽  
Dmitri Shadrin ◽  
Boris Vasilyev ◽  
...  
Keyword(s):  
Turbine Blade ◽  
Vibrational Energy ◽  
Turbine Blades ◽  
Relative Displacement ◽  
Design Stage ◽  
Turbine Wheel ◽  
Friction Forces ◽  
Operational Conditions ◽  
Frequency Changes ◽  
Blade Frequency

Prevention of high cycle fatigue failures of blades caused by increased level of vibrational stresses is important problem in engine design and development. Different types of dampers are usually installed under the blade platforms in the region between the shanks of adjacent blades are usually used to reduce the vibrational stresses in the turbine blades. The action of these dampers is based on the vibrational energy dissipation by the dry friction forces arising due to the relative displacement of the contacting surfaces of the damper and the blade. Adoption of a reliable choice of damper design mass and stiffness at the design stage of the aircraft engines requires an experimentally validated estimation of its damping efficiency and its influence on the blade frequency characteristics. The dampers need to be tested under conditions that are maximally close to the operational conditions. This paper presents an analysis of the stress gauging results of a turbine wheel with box-type dampers of various mass. The tests were carried out on a dynamic bench where resonance oscillations of a stage for a given mode were excited by one of the harmonics to a given rotational speed under the corresponding forces pressing the dampers onto the blade platform. An estimation of the damper efficiency in a wider range of pressing forces was also obtained by conducting the laboratory tests using on a specially designed vibration unit that simulates the dampers effect on a set of three blades. Numerical analysis of the damper mass and stiffness influence on the frequency and damping characteristics of a real turbine wheel was performed. Obtained experimental data and the GAP model of contact interaction of the insert with blades were used in the MSC. Nastran software package. Analysis showed a satisfactory correlation between the calculated and experimental estimates of the decrease in resonant stresses and resonance frequency changes when the dampers are inserted. The results presented here confirm the possibility of increasing the reliability of the choice of mass and stiffness of turbine blade dampers at the design stage.

scholarly journals The Evaluation of the Damping Characteristics of a Hard Coating on Titanium

2007 ◽  
Vol 14 (1) ◽  
pp. 37-51 ◽  
Author(s):  
Christopher Blackwell ◽  
Anthony Palazotto ◽  
Tommy J. George ◽  
Charles J. Cross
Keyword(s):  
Aspect Ratio ◽  
Turbine Blades ◽  
Plate Thickness ◽  
Point Of View ◽  
Internal Stresses ◽  
Experimental Point ◽  
Laser Vibrometer ◽  
The Past ◽  
Damping Characteristics ◽  
Bending Mode

Engine failures due to fatigue have cost the Air Force an estimated $400 million dollars per year over the past two decades. Damping treatments capable of reducing the internal stresses of fan and turbine blades to levels where fatigue is less likely to occur have the potential for reducing cost while enhancing reliability. This research evaluates the damping characteristics of magnesium aluminate spinel, MgO+Al2O3, (mag spinel) on titanium plates from an experimental point of view. The material and aspect ratio were chosen to approximate the low aspect ratio blades found in military gas turbine fans. In the past, work has generally been performed on cantilever supported beams, and thus the two-dimensional features of damping were lost. In this study plates were tested with a cantilevered boundary condition, using electrodynamic shaker excitation. The effective test area of each specimen was 4.5 in × 4.5 in. The nominal plate thickness was 0.125 in. Mag spinel was applied to both sides of the plate, at a thickness of 0.01 in, and damping tests were run at room temperature. The effect of the coating was evaluated at the 2nd bending mode (mode 3) and the chord wise bending mode (mode 4). A scanning laser vibrometer revealed the frequency and shape of each mode for the plates. Sine sweeps were used to characterize the damping of the coated and uncoated specimens for the modes tested. The coating increased damping nonlinearly for both modes tested in which the general outcome was similar to that found in beams.

TEM study of a biofilm on copper corrosion

1996 ◽  
Vol 54 ◽  
pp. 220-221
Author(s):  
W. A. Chiou ◽  
N. Kohyama ◽  
B. Little ◽  
P. Wagner ◽  
M. Meshii
Keyword(s):  
Marine Bacterium ◽  
Culture Medium ◽  
Copper Alloys ◽  
Pure Copper ◽  
Localized Corrosion ◽  
Natural Seawater ◽  
Copper Corrosion ◽  
New Approach ◽  
The Past ◽  
Copper Tolerant

The corrosion of copper and copper alloys in a marine environment is of great concern because of their widespread use in heat exchangers and steam condensers in which natural seawater is the coolant. It has become increasingly evident that microorganisms play an important role in the corrosion of a number of metals and alloys under a variety of environments. For the past 15 years the use of SEM has proven to be useful in studying biofilms and spatial relationships between bacteria and localized corrosion of metals. Little information, however, has been obtained using TEM capitalizing on its higher spacial resolution and the transmission observation of interfaces. The research presented herein is the first step of this new approach in studying the corrosion with biological influence in pure copper.Commercially produced copper (Cu, 99%) foils of approximately 120 μm thick exposed to a copper-tolerant marine bacterium, Oceanospirillum, and an abiotic culture medium were subsampled (1 cm × 1 cm) for this study along with unexposed control samples.

Chelovek.RU/Человек.RU

Chelovek RU ◽  
2020 ◽  
pp. 18-53
Author(s):  
Sergei Avanesov ◽  
Keyword(s):  
Family History ◽  
Great Distance ◽  
Point Of View ◽  
The Past ◽  
Russian Philosopher ◽  
True Meaning ◽  
The Future ◽  
Pavel Florensky ◽  
The Moment

Abstract. The article analyzes the autobiography of the famous Russian philosopher, theologian and scientist Pavel Florensky, as well as those of his texts that retain traces of memories. According to Florensky, the personal biography is based on family history and continues in children. He addresses his own biography to his children. Memories based on diary entries are designed as a memory diary, that is, as material for future memories. The past becomes actual in autobiography, turns into a kind of present. The past, from the point of view of its realization in the present, gains meaning and significance. The au-thor is active in relation to his own past, transforming it from a collection of disparate facts into a se-quence of events. A person can only see the true meaning of such events from a great distance. Therefore, the philosopher remembers not so much the circumstances of his life as the inner impressions of the en-counter with reality. The most powerful personality-forming experiences are associated with childhood. Even the moment of birth can decisively affect the character of a person and the range of his interests. The foundations of a person's worldview are laid precisely in childhood. Florensky not only writes mem-oirs about himself, but also tries to analyze the problems of time and memory. A person is immersed in time, but he is able to move into the past through memory and into the future through faith. An autobi-ography can never be written to the end because its author lives on. However, reaching the depths of life, he is able to build his path in such a way that at the end of this path he will unite with the fullness of time, with eternity.

Portuguese Sardines - from the ritual to the brand

2017 ◽  
Vol 5 (2) ◽  
pp. 109-120
Author(s):  
Cecília Avelino Barbosa
Keyword(s):  
Social Construction ◽  
Place Branding ◽  
Symbolic Capital ◽  
City Council ◽  
Point Of View ◽  
City Branding ◽  
The Past ◽  
Behavioral Expression ◽  
The City ◽  
City Identity

Place branding is a network of associations in the consumer’s mind, based on the visual, verbal, and behavioral expression of a place. Food can be an important tool to summarize it as it is part of the culture of a city and its symbolic capital. Food is imaginary, a ritual and a social construction. This paper aims to explore a ritual that has turned into one of the brands of Lisbon in the past few years. The fresh sardines barbecued out of doors, during Saint Anthony’s festival, has become a symbol that can be found on t-shirts, magnets and all kinds of souvenirs. Over the year, tourists can buy sardine shaped objects in very cheap stores to luxurious shops. There is even a whole boutique dedicated to the fish: “The Fantastic World of Portuguese Sardines” and an annual competition promoted by the city council to choose the five most emblematic designs of sardines. In order to analyze the Sardine phenomenon from a city branding point of view, the objective of this paper is to comprehend what associations are made by foreigners when they are outside of Lisbon. As a methodological procedure five design sardines, were used of last year to questioning to which city they relate them in interviews carried in Madrid, Lyon, Rome and London. Upon completion of the analysis, the results of the city branding strategy adopted by the city council to promote the sardines as the official symbol of Lisbon is seen as a Folkmarketing action. The effects are positive, but still quite local. On the other hand, significant participation of the Lisbon´s dwellers in the Sardine Contest was observed, which seems to be a good way to promote the city identity and pride in their best ambassador: the citizens.

History of Tour de France from the Geographical Point of View

2013 ◽  
Vol 22 (3-4) ◽  
pp. 255-277 ◽  
Author(s):  
Vladimír Bačík ◽  
Michal Klobučník
Keyword(s):  
Point Of View ◽  
The Past ◽  
Advanced Technologies ◽  
The World ◽  
Spatial Dimensions ◽  
Tour De France ◽  
Wide Circle ◽  
History Of ◽  
Expert Community ◽  
Geographical Point

Abstract The Tour de France, a three week bicycle race has a unique place in the world of sports. The 100th edition of the event took place in 2013. In the past of 110 years of its history, people noticed unique stories and duels in particular periods, celebrities that became legends that the world of sports will never forget. Also many places where the races unfolded made history in the Tour de France. In this article we tried to point out the spatial context of this event using advanced technologies for distribution of historical facts over the Internet. The Introduction briefly displays the attendance of a particular stage based on a regional point of view. The main topic deals with selected historical aspects of difficult ascents which every year decide the winner of Tour de France, and also attract fans from all over the world. In the final stage of the research, the distribution of results on the website available to a wide circle of fans of this sports event played a very significant part (www.tdfrance.eu). Using advanced methods and procedures we have tried to capture the historical and spatial dimensions of Tour de France in its general form and thus offering a new view of this unique sports event not only to the expert community, but for the general public as well.

Sign in / Sign up

Export Citation Format

Share Document