A Model-Based Prediction of Balancing Behavior of Rotors Above the Speed Range in Available Balancing Systems

2020 ◽  
Author(s):  
Paolo Pennacchi ◽  
Riccardo Ferraro ◽  
Steven Chatterton ◽  
Damaso Checcacci
Keyword(s):  
Rotor Dynamics ◽  
Turbine Rotor ◽  
Point Of View ◽  
Small Scale ◽  
Traditional Methods ◽  
Vibration Measurements ◽  
Industrial Practice ◽  
Speed Range ◽  
Identification Techniques ◽  
Rotor Balancing

Abstract Rotor balancing is probably the most discussed topic in the entire literature about rotor dynamics. It would therefore seem that, from the point of view of theory, this is a problem of little interest, however, balancing is very relevant in the industrial practice and sometimes there are very particular cases that cannot be addressed and solved by traditional methods. Moreover, many papers deal with only simulated results or with small-scale tests-rigs, which can hardly reproduce the behavior of real rotors. The case described in this paper is just one of these and presents what could be defined as “predicting the effect of balancing” at rotational speeds that are higher than those possible on balancing machines. Rotordynamics modeling, identification techniques developed by the authors and the available vibration measurements allow the simulation of the behavior, i.e. the vibrations, of the considered turbine rotor on the balancing machine, even at rotational speeds higher than those are possible to be reached, but that correspond to the trip speed in the plant.

Towards a New Model of Conversion Careers: the Impact of Personality and Contingency Factors

Exchange ◽  
2005 ◽  
Vol 34 (2) ◽  
pp. 149-166 ◽  
Author(s):  
Henri Gooren
Keyword(s):  
Religious Conversion ◽  
Religious Affiliation ◽  
Point Of View ◽  
Small Scale ◽  
Central Question ◽  
Roman Catholicism ◽  
Guatemala City ◽  
Practical Point ◽  
The Poor ◽  
The Impact

AbstractThe central question of this article — why people may change their religious affiliation or become disaffiliated — is relevant from both an academic and a practical point of view. The article makes first an inventory of existing literature on religious conversion. Next I sketch the contours of the new conversion careers approach I am currently working on. I make some comparisons with a region that is not usually mentioned in the literature on conversion: Latin America. These comparisons are based on my earlier fieldwork on Roman Catholicism, Pentecostalism, and Mormonism in Costa Rica and Guatemala (H. Gooren, Rich among the Poor: Church, Firm, and Household among Small-scale Entrepreneurs in Guatemala City, Amsterdam: Thela Thesis 1999).

scholarly journals Gogolesque in the novel “The Life of Arseniev” by Ivan Bunin

2021 ◽  
Author(s):  
Elena Vranchan
Keyword(s):  
Point Of View ◽  
Small Scale ◽  
The Novel ◽  
Old World ◽  
The Past ◽  
The Family ◽  
Artistic Interpretation

The article deals with the peculiarities of the patriarchal noble-peasant life description in the novel “The Life of Arseniev” (1930) by Ivan Bunin, focuses on the use of characteristic Gogol’s images and techniques. Moreover, the comparison of the artistic interpretation ways of the patriarchal past by the writers reveals the Gogol's influence on the position of Bunin as the author, which is presented in the novel in different ways: from the point of view of an observer narrator who topographically accurately depicts the reality and life of the family estate, and from the point of view of an emigrant, focused on memories of the past, conveying an emotional sense of the connection between generations. In general, Bunin continues to develop the theme of the collision of immobile patriarchy with the quick movement of time that destroys the old serfdom, so his novel is imbued with nostalgia for the small-scale world going into the past. In Bunin's nostalgia, there are echoes of Gogol's sorrow about the doomed old world life.

scholarly journals EFFICIENCY OF CLASSICAL AND MODERN DISTANT METHODS OF TEACHING PHONETICS IN THE SYSTEM OF SCHOOL EDUCATION

2020 ◽  
pp. 141-145
Author(s):  
Елена Анатольевна Филатова
Keyword(s):  
Comparative Analysis ◽  
Computer Programs ◽  
Point Of View ◽  
Specific Training ◽  
Teaching English ◽  
Traditional Methods ◽  
Computer Methods ◽  
Russian State ◽  
Modern Methods ◽  
And Training

Приводится сравнительно-сопоставительный анализ современных традиционных и компьютерных методик обучения сегментной и супрасегментной фонетике английского языка в условиях аудиторного билингвизма, обосновывается необходимость введения новых методик обучения устной речи в современных школьных УМК, нацеленных на подготовку к устной части ЕГЭ по иностранному языку, а также необходимость разработки в них новых критериев оценивания фонетической стороны речи. Автор дает обобщенную характеристику традиционных методов обучения произношению и анализируют эффективность их применения на уроке иностранного языка в современной школе в среднем и старшем звене обучения. Приводятся основные задачи и цели компьютерного обучения фонетике, а также специфика его использования в аудитории искусственного билингвизма. На примере конкретных компьютерных программ анализируется эффективность дистанционных методов обучения с точки зрения подготовки школьников к сдаче государственных экзаменов. A comparative analysis of traditional and computer methods of teaching English segmental and suprasegmental phonetics in conditions of auditory bilingualism is given. The need for new modern methods of teaching and textbooks is justified. It is revealed that new computer methods of teaching should be aimed for preparing and training for the oral part of the Russian State Exam and have different estimation criteria. General characteristics of basic traditional methods (articulatory and acoustic) and their effectiveness is shown on the examples of concrete Russian and foreign editions, in comparison with popular computer programs. Computer programs for teaching English phonetics are analyzed from the point of view of their specific training of auditory bilinguals.

scholarly journals Double-Stage H-Darrieus Wind Turbine - Rotor Aerodynamics

2016 ◽  
Vol 829 ◽  
pp. 21-26
Author(s):  
Mahdi Torabi Asr ◽  
Reza Osloob ◽  
Faizal Mustapha
Keyword(s):  
Turbine Rotor ◽  
Point Of View ◽  
Peak Performance ◽  
Average Wind Speed ◽  
Stage Design ◽  
Rotor Aerodynamics ◽  
Rotor Design ◽  
Average Wind ◽  
Start Up ◽  
Novel Design

H-Darrieus wind turbines, due to their simple design and relatively low manufacturing costs have recently received much attention particularly for standalone applications. However start-up issues associated with their operation restricted their operation in areas of low average wind speed and encourages engineers to develop novel design. Several design proposed in this way but in most cases design came up with complex sensing mechanisms and mechanical actuators or high cost manufacturing parts. A recent rotor design called double Darrieus rotor proposed as a German patent case bridged these complexities appropriately. The aim of present study is to investigate this innovative design from aerodynamic point of view by means of validated CFD techniques. A flow-driven simulation setup based on 6DOF calculations employed in order to study rotor operation from stand still until peak performance obtained. Results from these precise modeling reveal the superiority of the proposed double-stage design in compare with the original H-Darrieus rotors in terms of start-up behavior and optimum performance.

Bearing Housing Design for Vibration Control, Using Tilting Pad Bearings Instead of Lemon-Bore Type on a Gas Turbine

2020 ◽  
Author(s):  
Chippa Anil ◽  
Aparna Satheesh ◽  
Babu Santhanagopalakrishnan ◽  
Marcin Bielecki
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Structural Integrity ◽  
Plane Surface ◽  
Rotor Dynamics ◽  
Turbine Rotor ◽  
Outer Diameter ◽  
Housing Design ◽  
Tilting Pad ◽  
And Performance

Abstract Heavy duty gas turbines are usually equipped with hydrodynamic bearings which are either lemon-bore or tilting pad type. Baker Hughes legacy gas turbines use these two types of bearings, and its selection is based on 1) considering pros & cons from Rotor dynamics, 2) bearing performance, 3) bearing housing stiffness, 4) vibration detection & control. Non-contact probes are used to monitor the vibrations of rotor. Majority of legacy gas turbines are not equipped with these probes. Due to this fact, over the years it resulted in non-detection of dynamics & vibration issue, which caused frequent bearing replacement. As the increase in industry demand to apply and measure vibrations using non-contact probes on bearings, an effort was made by Baker Hughes to implement these on existing fleet units. Also, in order to increase rotor dynamics stability of low-pressure rotor, to improve bearing life and performance, effort was made to replace lemon-bore bearings with tilting pad. This paper demonstrates efforts made to design the titling pad which would fit within envelop of already available bearing housing. Bearing/shaft clearance, bearing performance, modification of bearing retainer clearances are the mandatory tasks which would be dealt in this study. The swap of bearing type, and its effect on whole gas turbine rotor dynamic stability, checking the frequency crossovers with Campbell diagram would also be dealt in this paper. This paper also focuses on assessment on oil passage routing, temperature & proximity probe instrumentation routing design. Re-design is performed by analyzing various configuration, assessing different sensitivity studies & validation of modified bearing housing from structural integrity, ultimate load capability, & split plane oil leakage retention and its comparison with baseline are most important aspects of finalization of this change, which will be showcased in this paper. Instrumentation routing was a critical task when the considering bearing replacement from lemon-bore to tilting pad. As lemon-bore type bearings just have an elliptical inner surface, it’s quite easy to install the thermocouples into a simple hole. But as replacement has tilting pads, the challenge is to instrument the pads without effecting their movement and functionality. Such best practices are also dealt in this paper. Comparison of tilting-pad with lemon-bore, considering the fixed shaft diameter, the retainer outer diameter of tilting pad is higher than lemon-bore. This effect has a change in bearing seat on bearing housing, thereby reducing the effective stiffness of the housing, and the reduced split plane surface. To tackle this situation, several sensitivities were executed, by re-modifying the bolts and bolt holes on the existing housing, without modifying the housing envelop.

Diagnosing chromospheric magnetic field through simultaneous spectropolarimetry in Hα and Ca II 854.2 nm

2019 ◽  
Vol 15 (S354) ◽  
pp. 46-52
Author(s):  
K. Nagaraju ◽  
K. Sankarasubramanian ◽  
K. E. Rangarajan
Keyword(s):  
Magnetic Field ◽  
Time Evolution ◽  
Opposite Polarity ◽  
Point Of View ◽  
Current Understanding ◽  
Small Scale ◽  
Preliminary Results

AbstractMeasurement of magnetic field in this layer is challenging both from point of view of observations and interpretation of the data. We present in this work about spectropolarimetric observations of a pore, simultaneously in Ca ii (CaIR) at 854.2 nm (CaIR) and H α (656.28 nm). The observed region includes a small scale energetic event (SSEE) taking place in the region between the pore and the region which show opposite polarity to that of pore at the photosphere. The energetic event appears to be a progressive reconnection event as shown by the time evolution of the intensity profiles. Closer examination of the intensity profiles from the downflow regions suggest that the height of formation of CaIR is higher than that of Hi α, contrary to the current understanding about their height of formation. Preliminary results on the inversion of Stokes-I and V profiles of CaIR are also presented.

scholarly journals General Theory of Subglacial Cavitation and Sliding of Temperate Glaciers

1968 ◽  
Vol 7 (49) ◽  
pp. 21-58 ◽  
Author(s):  
L. Lliboutry
Keyword(s):  
Frictional Force ◽  
Atmospheric Pressure ◽  
Hydraulic System ◽  
Water Pressure ◽  
Realistic Model ◽  
Point Of View ◽  
Small Scale ◽  
Sliding Velocity ◽  
Surface Slope ◽  
Geometrical Progression

AbstractEarlier theories of Weertman and the present author are reviewed and compared; both are insufficient to account for the facts observed at the tongue of the Allalingletscher.A calculation of the stresses and heat flow at the bed of a glacier with a sinusoidal profile is given which takes account of any degree of subglacial cavitation. The sliding due to plasticity and that due to pressure melting are related to this degree of cavitation and it is shown that these two terms are additive. There results an expression for the frictionfωin terms of the total sliding velocityuand the height of the bumpsa. For a given and large enough value ofu,fω(a) exhibits two maxima which are equal and independent ofu.The paper then considers a more realistic model of the bed consisting of a superposition of sine waves all having the same roughnessr, andadecreasing in a geometrical progression. The biggestamay be inferred from the overall profile of the bedrock; the resulting frictional force can be regarded either as part of the total frictional forcefin an overall view for whichf=ρghsinαholds, or else as a correction to such a value on the small scale (the best point of view for crevasse studies). To a first approximation Coulomb’s law of friction holds provided one takes account of the interstitial water pressure at the ice-rock interface.This interstitial pressurepis next related to the thickness of the glacierh. If the subglacial hydraulic system is at atmospheric pressure,pis proportional toh. Next, if the sliding velocity is not too large, the surface slope approaches 1.6r≈ 0.12 and kinematic waves (which move four times as fast as the ice) disappear rapidly. If the hydraulic system is not at atmospheric pressure the surface slope is smaller and flow instabilities can occur.

Genetic Optimization of Geometrical Parameters of High Speed Rotor

2015 ◽  
Author(s):  
Behnam Ghalamchi ◽  
Adam Kłodowski ◽  
Jussi T. Sopanen ◽  
Aki M. Mikkola
Keyword(s):  
High Speed ◽  
Turbine Rotor ◽  
Optimization Techniques ◽  
Design Parameters ◽  
Geometrical Parameters ◽  
Campbell Diagram ◽  
Critical Speeds ◽  
Operation Speed ◽  
Wide Range ◽  
Speed Range

The main scope of this paper is optimization of high speed rotor systems by using Evolutionary Algorithm. The target of the optimization is finding geometrical parameters of the shaft, in such a way that the critical speeds are not occurring in the operation speed range. Rotating machines have a wide range of applications in industrial machinery and applying numerical optimization techniques helps engineers to improve the performance of rotor bearing systems. A schematic of a turbine rotor system is studied. The rotor is modeled using finite element method and Timoshenko beam elements having four degrees of freedom (DOF) per node — two translational and two rotational. Critical speeds are identified using Campbell diagram. The outcome of the simulation is looking to find the widest safe margin for operation speed range without any critical speed in Campbell diagram within the operation range. Design parameters for optimization are overhang shafts lengths and diameters. Several simulation runs with different variables shows a significant effect of these parameters in dynamic behavior of the system. Comparison of the results with the basic design of turbine rotor reveals that all constraints are satisfied.

scholarly journals The Högdalen urban farm: a real case assessment of sustainability attributes

Food Security ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1461-1475
Author(s):  
Rebecka Milestad ◽  
Annika Carlsson-Kanyama ◽  
Christina Schaffer
Keyword(s):  
Urban Space ◽  
Food Production ◽  
Production Systems ◽  
Ghg Emissions ◽  
Point Of View ◽  
Small Scale ◽  
Food Provisioning ◽  
Urban Farm ◽  
City District ◽  
The City

AbstractWhile urban indoor farming is a fairly new phenomenon, there is a growing interest from producers, authorities and consumers alike. However, many assumptions are made, and expectations held, about urban indoor farming from a sustainability, food production and food provisioning point of view. These assumptions and expectations need to be tested and assessed. This study assessed greenhouse gas (GHG) emissions and a number of social aspects of a newly established indoor urban farm in Stockholm. The farm was the result of a project created by commercial, civil society and municipal actors with the aim to make use of unused urban space, create jobs and produce food. While lettuce grown on the indoor farm emitted more GHG than lettuce cultivated outdoors in Sweden, it was more climate friendly than imported lettuce in our comparison. Furthermore, the indoor farm created value for the actors involved and for the city district, albeit on a small scale. Many of the positive environmental and social features owed to the small scale of the indoor farm and the context in which it developed. Thus, when evaluating production systems like this one, we need to be cautious and refrain from extrapolating the results.

scholarly journals Effective Null Raychaudhuri Equation

Particles ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 230-237 ◽  
Author(s):  
Alessandro Pesci
Keyword(s):  
Focal Point ◽  
Effective Rate ◽  
Rate Of Change ◽  
Point Of View ◽  
Small Scale ◽  
Generic Point ◽  
Cross Sectional ◽  
Effective Expansion ◽  
Continuous Description ◽  
Particle Nature

The effects on Raychaudhuri’s equation of an intrinsically-discrete or particle nature of spacetime are investigated. This is done through the consideration of null congruences emerging from, or converging to, a generic point of spacetime, i.e., in geometric circumstances somehow prototypical of singularity issues. We do this from an effective point of view, that is through a (continuous) description of spacetime modified to embody the existence of an intrinsic discreteness on the small scale, this adding to previous results for non-null congruences. Various expressions for the effective rate of change of expansion are derived. They in particular provide finite values for the limiting effective expansion and its rate of variation when approaching the focal point. Further, this results in a non-vanishing of the limiting cross-sectional area itself of the congruence.

Sign in / Sign up

Export Citation Format

Share Document