A Review of the Rotordynamic Thermally Induced Synchronous Instability (Morton) Effect

2017 ◽  
Vol 69 (6) ◽  
Author(s):  
Xiaomeng Tong ◽  
Alan Palazzolo ◽  
Junho Suh
Keyword(s):  
Case Studies ◽  
Design Stage ◽  
Trial And Error ◽  
Thermally Induced ◽  
Conventional View ◽  
Fluid Film Bearings ◽  
Morton Effect ◽  
Theoretical Predictions ◽  
Rotating Shafts ◽  
Universal Solutions

The Morton effect (ME) is a thermally induced instability problem that most commonly appears in rotating shafts with large overhung masses and supported by fluid-film bearings. The time-varying thermal bow, due to the asymmetric journal temperature distribution, may cause intolerable synchronous vibrations that exhibit a hysteresis behavior with respect to rotor speed. First discovered by Morton in the 1970s and theoretically analyzed by Keogh and Morton in the 1990s, the ME is still not fully understood by industry and academia experts. Traditional rotordynamic analysis generally fails to predict the potential existence of ME-induced instability in the design stage or troubleshooting process, and the induced excessive rotor vibrations cannot be effectively suppressed through conventional balancing, due to the continuous fluctuation of vibration amplitude and phase angle. In recent years, a fast growing number of case studies of ME have sparked academic interest in analyzing the causes and solutions of ME, and engineers have moved from an initial trial and error approach to more research inspired modification of the rotor and bearing. To facilitate the understanding of ME, the current review is intended to give the most comprehensive summary of ME in terms of symptoms, causes, prediction theories, and solutions. Published case studies in the past are also analyzed for ME diagnosis based on both the conventional view of critical speed, separation margin (SM), and the more recent view of the rotor thermal bow and instability speed band shifting. Although no universal solutions of ME are reported academically and industrially, recommendations to help avoid the ME are proposed based on both theoretical predictions and case studies.

Double Overhung Disk and Parameter Effect on Rotordynamic Synchronous Instability—Morton Effect—Part I: Theory and Modeling Approach

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
Xiaomeng Tong ◽  
Alan Palazzolo
Keyword(s):  
Linear Method ◽  
Response Prediction ◽  
Transient Method ◽  
Thermally Induced ◽  
Morton Effect ◽  
Nonlinear Transient ◽  
Rotating Shafts ◽  
Overhung Rotors ◽  
Different Response ◽  
Theory And Modeling

The Morton effect (ME) is a thermally induced instability problem that most commonly appears in rotating shafts with large overhung masses, outboard of the bearing span. The time-varying thermal bow due to the asymmetric journal temperature distribution may cause intolerable synchronous vibrations that exhibit a hysteresis behavior with respect to rotor speed. The fully nonlinear transient method designed for the ME prediction, in general, overhung rotors is proposed with the capability to perform the thermoelastohydrodynamic analysis for all the bearings and model the rotor thermal bow at both overhung ends with equivalent distributed unbalances. The more accurate nonlinear, coupled, double overhung approach is shown to provide significantly different response prediction relative to the more approximate linear method based using bearing coefficients and the single-overhung method, which assumes that the ME on both rotor ends can be decoupled. The flexibility of the bearing pad and pivot is investigated to demonstrate that the pivot flexibility can significantly affect the rotordynamics and ME, while the rigid pad model is generally a good approximation.

Coding in Qualitative Research

2018 ◽  
Author(s):  
Mohammad Yaghi
Keyword(s):  
Qualitative Research ◽  
Case Studies ◽  
Qualitative Data ◽  
Doctoral Dissertation ◽  
Sufficient Data ◽  
Trial And Error ◽  
Amount Of Information ◽  
Potential Problems

In this chapter, Yaghi offers detailed suggestions on how to code qualitative data after they have been gathered. Based on his doctoral dissertation, this chapter explains that the logic behind coding qualitative data is to turn a significant amount of information into categories that can be used to explain a phenomenon, reveal a concept, or render the data comparable across different case studies. It also elaborates through examples from author’s fieldwork in Tunisia, Egypt, and Jordan on four potential problems that may face researchers in coding qualitative data. These are the questions of preparation, categorization, consistency, and saturation. The chapter concludes by asking researchers to be flexible, and open to the process of trial and error in coding, to confront the data with questions before categorization, and to gather sufficient data on their topics before running their qualitative surveys.

scholarly journals Rotor Loading Characteristics of a Full-Scale Tidal Turbine

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1035 ◽  
Author(s):  
Magnus Harrold ◽  
Pablo Ouro
Keyword(s):  
Turbulent Flows ◽  
Mechanical Loading ◽  
Full Scale ◽  
Design Stage ◽  
Flow Profile ◽  
Expected Return ◽  
Tidal Turbines ◽  
Theoretical Predictions ◽  
Tidal Turbine

Tidal turbines are subject to highly dynamic mechanical loading through operation in some of the most energetic waters. If these loads cannot be accurately quantified at the design stage, turbine developers run the risk of a major failure, or must choose to conservatively over-engineer the device at additional cost. Both of these scenarios have consequences on the expected return from the project. Despite an extensive amount of research on the mechanical loading of model scale tidal turbines, very little is known from full-scale devices operating in real sea conditions. This paper addresses this by reporting on the rotor loads measured on a 400 kW tidal turbine. The results obtained during ebb tidal conditions were found to agree well with theoretical predictions of rotor loading, but the measurements during flood were lower than expected. This is believed to be due to a disturbance in the approaching flood flow created by the turbine frame geometry, and, to a lesser extent, the non-typical vertical flow profile during this tidal phase. These findings outline the necessity to quantify the characteristics of the turbulent flows at sea sites during the entire tidal cycle to ensure the long-term integrity of the deployed tidal turbines.

Hands-On Graduate Courses in Lean Manufacturing (LM) Emphasizing Green and Total Productive Maintenance (TPM)

2010 ◽  
Author(s):  
Geoffrey J. Peter
Keyword(s):  
Graduate Students ◽  
Case Studies ◽  
Lean Manufacturing ◽  
Building Design ◽  
Pilot Project ◽  
Design Stage ◽  
Total Productive Maintenance ◽  
Initial Product ◽  
Hands On ◽  
Institute Of Technology

The author developed and taught the second hands-on graduate course in a series of three Environmentally Friendly Manufacturing (EFM) courses offered at the Manufacturing and Mechanical Engineering and Technology (MMET) Masters Program at the Oregon Institute of Technology (OIT), Portland Center. Courses in this series include Environmentally Conscious Manufacturing (ECM-1), Lean Manufacturing (LM) emphasizing Green and Total Productive Maintenance (TPM), and Emission Control in Manufacturing (ECM-II). The first two-thirds of the course curriculum consisted of regular classroom lectures, limited homework, two case studies, discussions, videos, and visits to two companies that were implementing or had implemented LM. In addition, a guest lecturer from Washington State Department of Ecology discussed relevant LM and environmental case studies. The final third of the course curriculum consisted of hands-on industry-based case studies. Students gained real-world experience in the manufacturing facilities of the four companies that elected to participate in the pilot project. The LM course, taught from an engineer’s point of view, emphasized the engineer’s role at the initial product design stage, and or manufacturing process design, including building design. This paper describes the course content of the LM curriculum, the innovative methods developed to teach the course, and the methods used to teach LM to graduate students with different undergraduate educational backgrounds including individuals with no prior industrial experience. It discusses three industry-based case studies, company profiles, and the benefits derived by participating companies and graduate students. Curriculum effectiveness was determined at the end of the course in part through students’ and industry participant’s comments. Future publication will describe the contents and case studies of the third ECM II in the EFM course curricula.

scholarly journals Dynamic Analysis of Composite Rotors

1996 ◽  
Vol 2 (3) ◽  
pp. 179-186 ◽  
Author(s):  
S. P. Singh ◽  
K. Gupta
Keyword(s):  
Stability Analysis ◽  
Dynamic Analysis ◽  
Case Studies ◽  
Dynamic Behavior ◽  
Beam Theory ◽  
Interesting Case ◽  
Layerwise Theory ◽  
Inertia Effects ◽  
Fluid Film Bearings ◽  
Equivalent Modulus

An outline of formulation based on a layerwise beam theory for unbalance response and stability analysis of a multi mass, multi bearing composite rotor mounted on fluid film bearings is presented. Disc gyroscopics and rotary inertia effects are accounted for. Material damping is also taken into account. The layerwise theory is compared with conventionally used equivalent modulus beam theory. Some interesting case studies are presented. The effect of various parameters on dynamic behavior and stability of a composite rotor is presented.

Thermally Induced Synchronous Instability of a Radial Inflow Overhung Turbine: Part I

1997 ◽  
Author(s):  
H. B. Faulkner ◽  
W. F. Strong ◽  
R. G. Kirk
Keyword(s):  
Thermal Expansion ◽  
Operating Speed ◽  
Lateral Motion ◽  
Turbine Wheel ◽  
Thermally Induced ◽  
Lateral Dynamics ◽  
Morton Effect ◽  
Speed Range ◽  
Differential Thermal Expansion ◽  
Rotor Dynamic

Abstract This paper is in two parts, and concerns the lateral dynamics of a large turbocharger rotor with overhung wheels. Initial rotor dynamic analysis indicated no excessive motion in the operating speed range. However, testing showed excessive motion, which was initially traced to the radial-inflow turbine wheel becoming loose on the shaft, due to transient differential thermal expansion in the wheel on startup. The attachment of the wheel was modified to eliminate this problem. The discussion up to this point is in Part I of the paper, and the remainder is in Part II. The wheel attachment modification extended the range of satisfactory operation upward considerably, but excessive lateral motion was again encountered near the upper end of the operating speed range. This behavior was traced to thermal bowing of the shaft at the turbine end, known as the Morton Effect. The turbine end bearing was modified to eliminate this problem, and satisfactory operation was then achieved throughout the operating speed range.

Influence of Coupled Asymmetric Bearings on the Motion of a Massive Flexible Rotor

1967 ◽  
Vol 182 (1) ◽  
pp. 255-280 ◽  
Author(s):  
P. G. Morton
Keyword(s):  
Equations Of Motion ◽  
Arbitrary Mass ◽  
Dynamical Characteristics ◽  
Theoretical Predictions ◽  
Method Of Solution ◽  
Rotating Shafts ◽  
Stiffness And Damping ◽  
Oil Films ◽  
Stiffness Distribution ◽  
Model Rotor

The rotors of a majority of rotating machines are supported upon bearings whose flexibility has a significant effect on the dynamics of the system. Supports incorporating hydrodynamically maintained oil films in particular, in addition to possessing different stiffness and damping in mutually perpendicular planes, exhibit non-reciprocal coupling between motions in these planes. The author develops the equations of motion for a rotor-bearing system of this type, and describes how both the response to an out-of-balance forcing and the unstable behaviour of such a system may be predicted by evaluating separately the dynamical characteristics of the rotor and the bearings. The method is applicable to systems in which the rotor is axisymmetric and has an arbitrary mass and stiffness distribution symmetrically disposed about its centre of span. Some new aspects of the resonant and unstable behaviour of rotating shafts are brought out due to the nature of the method of solution. Theoretical predictions are compared and agree very well with the results of tests on a 1380 lb model rotor supported on two 4 in diameter cylindrical journal bearings.

scholarly journals Understanding Computational Methods for Solar Envelopes Based on Design Parameters, Tools, and Case Studies: A Review

Energies ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3302 ◽  
Author(s):  
Miktha Farid Alkadri ◽  
Francesco De Luca ◽  
Michela Turrin ◽  
Sevil Sariyildiz
Keyword(s):  
Case Studies ◽  
Urban Areas ◽  
Urban Infrastructure ◽  
Digital Tools ◽  
Design Stage ◽  
Design Parameters ◽  
Design Strategies ◽  
The Past ◽  
Local Contexts ◽  
Urban Heat

The increasing population density in urban areas simultaneously impacts the trend of energy consumption in building sectors and the urban heat island (UHI) effects of urban infrastructure. Accordingly, passive design strategies to create sustainable buildings play a major role in addressing these issues, while solar envelopes prove to be a relevant concept that specifically considers the environmental performance aspects of a proposed building given their local contexts. As significant advances have been made over the past decades regarding the development and implementation of computational solar envelopes, this study presents a comprehensive review of solar envelopes while specifically taking into account design parameters, digital tools, and the implementation of case studies in various contextual settings. This extensive review is conducted in several stages. First, an investigation of the scope and procedural steps of the review is conducted to frame the boundary of the topic to be analyzed within the conceptual framework of solar envelopes. Second, comparative analyses between categorized design methods in parallel with a database of design parameters are conducted, followed by an in-depth discussion of the criteria for the digital tools and case studies extracted from the selected references. Third, knowledge gaps are identified, and the future development of solar envelopes is discussed to complete the review. This study ultimately provides an inclusive understanding for designers and architects regarding the progressive methods of the development of solar envelopes during the conceptual design stage.

Morton Effect Induced Synchronous Instability in Mid-Span Rotor–Bearing Systems, Part 2: Models and Simulations

2011 ◽  
Vol 133 (6) ◽  
Author(s):  
Zenglin Guo ◽  
Gordon Kirk
Keyword(s):  
Journal Bearing ◽  
Negative Impact ◽  
System Stability ◽  
Stability Performance ◽  
Fluid Film Bearings ◽  
Morton Effect ◽  
Thermal Bending ◽  
Hydrodynamic Journal Bearing ◽  
The Stability ◽  
Thermal Imbalance

The mechanism of the Morton Effect induced synchronous instability has been discussed in Part 1, using an assumption of isotropic linear bearings. The second part of the current study will now focus on the more realistic systems, mid-span rotors supported by the hydrodynamic journal bearings. First, the models to calculate the thermal bending of the shaft and the temperature distribution across the journal surface are established. This can be used to calculate the equivalent thermal imbalance. The calculations of the temperature difference and its equivalent thermal imbalance using hydrodynamic plain journal bearing models are conducted and discussed with the comparison to the analytical results obtained in Part 1. It shows that the thermal imbalance induced by the Morton Effect may increase to the level of the mechanical imbalance and then its influence on the system stability should be included. The suggested thermal bending model also partially explains that the mid-span rotors are less liable to be influenced by the Morton Effect induced instability than are the overhung configurations, because of the restraining effect between two supports. Finally, a symmetric mid-span rotor - hydrodynamic journal bearing system is calculated to show its stability performance. The results show the inclusion of the Morton Effect may lead to an unstable operation of the system. Considering the existence of the oil film self-induced vibration due to the dynamic characteristics of fluid film bearings, the Morton Effect may make a further negative impact on the stability of the system. The simulation results of the unbalance response show that the Morton Effect changes the shapes of the whirling orbits and makes them no longer the standard elliptical orbits around the static equilibriums.

EXPLORING INTERNAL CORPORATE VENTURING IN SMEs: EFFECTUATION AT WORK IN A NEW CONTEXT

2013 ◽  
Vol 21 (03) ◽  
pp. 275-299 ◽  
Author(s):  
MAJBRITT ROSTGAARD EVALD ◽  
MARTIN SENDEROVITZ
Keyword(s):  
Case Studies ◽  
Exploratory Study ◽  
Business Development ◽  
Venture Creation ◽  
Trial And Error ◽  
Corporate Venturing ◽  
Strategic Behaviour ◽  
Business Opportunities ◽  
New Business ◽  
Innovative Thinking

This exploratory study investigates how small- and medium-sized enterprises (SMEs) may engage in business development through internal corporate venturing (ICV). We show, based upon three case studies, how ICV in SMEs may be organised in a predominantly improvised manner wherein unforeseen new business opportunities are created in an emergent and iterative trial-and-error process without predetermined goals and without pre-planned strategies. This is a process, we argue, that resembles predominantly effectuation logic. The study contributes to the stream of extant ICV literature by focusing on how SMEs engage in ICV. Moreover, the study contributes to the development of effectuation theory by demonstrating that effectuation logic makes sense, not only in its original venture creation context as suggested by Sarasvathy, but also with regard to how established SMEs infuse more innovative thinking through improvised ICV activities. Findings illustrate that, overall, SMEs act more effectual than causational; and also more than parts of the ICV literature suggest. However, looking at SMEs' ICV activities over several years, it becomes apparent that effectual logics are combined with more causational, pre-planned strategic behaviour.

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