scholarly journals Examination of the contact pattern of rolling surfaces

2019 ◽  
Vol 9 (2) ◽  
pp. 38-43
Author(s):  
Ferenc Sarka
Keyword(s):  
Operating Conditions ◽  
Contact Pattern ◽  
Rolling Bearings ◽  
Contact Patterns ◽  
Potential Applications ◽  
Gear Drives ◽  
Shape And Size

This article provides a brief summary of the potential applications of contact pattern examinations. The examination of contact pattern is a frequently used test for gear drives, rolling bearings and checking support rollers. It is used on gear drives and support rollers to test operating conditions, whereas in the case of rolling bearings the cause of the failure has already been identified. The chapters mention the types of contact patterns, the shape and size of contact patterns. This article is an introduction to a multi-part article series that presents the computerbased capabilities of contact pattern examination.

scholarly journals Virulence evolution of a parasite infecting male and female hosts

2017 ◽  
Author(s):  
Alison M. Wardlaw ◽  
Aneil F. Agrawal
Keyword(s):  
Death Rate ◽  
Host Population ◽  
Reproductive Value ◽  
Contact Pattern ◽  
Male And Female ◽  
Virulence Evolution ◽  
Host Type ◽  
Contact Patterns ◽  
Exploitation Rate ◽  
Evolutionarily Stable

AbstractParasites experience different tradeoffs between transmission and virulence in male and female hosts if the sexes vary in life history or disease-related traits. We determine the evolutionarily stable levels of exploitation by pathogens under two scenarios: an unconstrained pathogen that expresses different exploitation rates within each host type as well as a pathogen constrained to express the same exploitation rate in each sex. We show that an unconstrained horizontally-transmitted parasite evolves to express the same sex-specific exploitation rate within each sex as it would in a host population composed entirely of hosts with that sex’s resistance and intrinsic death rate. In contrast, the ESS exploitation rate of a constrained pathogen is affected by sex-differences in susceptibility and non-random contact patterns between host types that differ in resistance. As the amount of within-sex transmission increases, the ESS shifts closer to the optimum trait value in the more susceptible sex. Allowing for some degree of vertical transmission, the exploitation rate expressed in females (but not males) changes with contact pattern even in unconstrained pathogens. Differences in contact pattern and susceptibility play an important role in determining the ESS exploitation rate by shifting the reproductive value of each host type.

Impacts of Dilution on Hydrogen Combustion Characteristics and NOx Emissions

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
P. R. Resende ◽  
Alexandre Afonso ◽  
Carlos Pinho ◽  
Mohsen Ayoobi
Keyword(s):  
Flame Stabilization ◽  
Combustion Characteristics ◽  
Operating Conditions ◽  
Nox Emissions ◽  
Detailed Chemical Kinetics ◽  
Portable Power ◽  
Small Scales ◽  
Potential Applications ◽  
Flame Behavior ◽  
Detailed Chemical

Combustion characteristics at small scales have been studied continuously due to the potential applications in portable power devices. It is known that heat release impacts at small scales result in different flame behavior as compared to conventional scales. The impacts of geometry, stoichiometry, flow rates, wall temperatures, etc., are widely studied in the literature. However, dilution impacts still need to be further studied due to its important role on controlling the flame behavior and subsequent pollutants emissions at these scales. In this work, premixed hydrogen/air combustion is simulated at an axis-symmetric microchannel (with diameter D = 0.8 mm and length L = 10 mm), where detailed chemical kinetics are implemented in simulations (32 species and 173 reactions). The heat transfer on the wall is considered by imposing a hyperbolic temperature profile on the wall, where the wall temperature increases from 300 K at the inlet to 1300 K at the outlet. With this setup, a range of equivalence ratios including a typical fuel-lean regime (ϕ = 0.7), stoichiometric regime (ϕ = 1.0), and two cases at an ultra-rich regime (ϕ = 2.0 and ϕ = 3.0) are investigated. For each equivalence ratio, excess dilution (using N2) is introduced to the mixture, and its impact is compared with other cases. With that, the impacts of dilution variations on the combustion characteristics of premixed hydrogen/air are investigated for different equivalence ratios. More specifically, several incidents such as flame dynamics, flame stabilization, extinctions, and NOx emissions are studied for the aforementioned operating conditions.

Incipient Surge Detection in Large Volume Energy Systems Based On Wigner-Ville Distribution Evaluated On Vibration Signals

2021 ◽  
Author(s):  
Carlo Alberto Niccolini Marmont Du Haut Champ ◽  
Paolo Silvestri ◽  
Mario L. Ferrari ◽  
Aristide Fausto Massardo
Keyword(s):  
Research Field ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Rolling Bearings ◽  
Time Frequency ◽  
Rotating Machine ◽  
Large Size ◽  
Critical Issues ◽  
Volume Energy ◽  
Transient Operations

Abstract Compressor response investigation in nearly unstable operating conditions, like rotating stall and incipient surge, is a challenging topic nowadays in the turbomachinery research field. Indeed, turbines connected with large-size volumes are affected by critical issues related to surge prevention, particularly during transient operations. Advanced signal-processing operations conducted on vibrational responses provide an insight into possible diagnostic and predictive solutions which can be derived from accelerometer measurements. Indeed, vibrational investigation is largely employed in rotating-machine diagnostics together with time-frequency analysis such as smoothed pseudo-Wigner Ville (SPWVD) time-frequency distribution (TFD) considered in this paper. It is characterized by excellent time and frequency resolutions and thus it is effectively employed in numerous applications in the condition monitoring of machinery. The aim and the innovation of this work regards SPWVD utilization to study turbomachinery behavior in detail in order to identify incipient surge conditions in the centrifugal compressor starting from operational vibrational responses measured at significant plant locations. To this aim, an experimental campaign has been conducted on a T100 microturbine connected with different volume sizes to collect significant data to be analyzed. The results show that SPWVD is able to successfully identify system evolution towards an unstable condition, by recognizing different levels and features of the particular kind of instability that is going to take place within the plant. Instability phenomena regarding rolling bearings have also been identified and their interaction with surge onset has been investigated for diagnostic purposes.

scholarly journals A Novel Hierarchical Algorithm for Bearing Fault Diagnosis Based on Stacked LSTM

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Lu Yu ◽  
Jianling Qu ◽  
Feng Gao ◽  
Yanping Tian
Keyword(s):  
Fault Diagnosis ◽  
Short Term Memory ◽  
Operating Conditions ◽  
Support Vector ◽  
Rolling Bearings ◽  
Hierarchical Algorithm ◽  
Bearing Fault Diagnosis ◽  
Rotary Machinery ◽  
Proposed Model ◽  
Series Of Experiments

Faced with severe operating conditions, rolling bearings tend to be one of the most vulnerable components in mechanical systems. Due to the requirements of economic efficiency and reliability, effective fault diagnosis methods for rolling bearings have long been a hot research topic of rotary machinery fields. However, traditional methods such as support vector machine (SVM) and backpropagation neural network (BP-NN) which are composed of shallow structures trap into a dilemma when further improving their accuracies. Aiming to overcome shortcomings of shallow structures, a novel hierarchical algorithm based on stacked LSTM (long short-term memory) is proposed in this text. Without any preprocessing operation or manual feature extraction, the proposed method constructs a framework of end-to-end fault diagnosis system for rolling bearings. Beneficial from the memorize-forget mechanism of LSTM, features inherent in raw temporal signals are extracted hierarchically and automatically by stacking LSTM. A series of experiments demonstrate that the proposed model can not only achieve up to 99% accuracy but also outperform some state-of-the-art intelligent fault diagnosis methods.

Performance and Development of a Miniature Rotary Shaft Pump

2005 ◽  
Vol 127 (4) ◽  
pp. 752-760 ◽  
Author(s):  
Danny Blanchard ◽  
Phil Ligrani ◽  
Bruce Gale
Keyword(s):  
Flow Rate ◽  
Pressure Rise ◽  
Electronics Cooling ◽  
Maximum Flow ◽  
Operating Conditions ◽  
Working Fluid ◽  
Hydraulic Efficiency ◽  
Potential Applications ◽  
Total Analysis ◽  
And Performance

The development and performance of a novel miniature pump called the rotary shaft pump (RSP) is described. The impeller is made by boring a 1.168 mm hole in one end of a 2.38 mm dia shaft and cutting slots in the side of the shaft at the bottom of the bored hole such that the metal between the slots defines the impeller blades. The impeller blades and slots are 0.38 mm tall. Several impeller designs are tested over a range of operating conditions. Pump performance characteristics, including pressure rise, hydraulic efficiency, slip factor, and flow rate, are presented for several different pump configurations, with maximum flow rate and pressure rise of 64.9ml∕min and 2.1 kPa, respectively, when the working fluid is water. Potential applications include transport of biomedical fluids, drug delivery, total analysis systems, and electronics cooling.

scholarly journals Laser alloying of bearing steel with boron and self-lubricating addition

2016 ◽  
Vol 36 (1) ◽  
pp. 7-11 ◽  
Author(s):  
Mateusz Kotkowiak ◽  
Adam Piasecki ◽  
Michał Kulka
Keyword(s):  
Wear Resistance ◽  
Calcium Fluoride ◽  
High Hardness ◽  
Bearing Steel ◽  
Operating Conditions ◽  
High Wear Resistance ◽  
Laser Alloying ◽  
Amorphous Boron ◽  
Rolling Bearings ◽  
Borided Layer

Abstract 100CrMnSi6-4 bearing steel has been widely used for many applications, e.g. rolling bearings which work in difficult operating conditions. Therefore, this steel has to be characterized by special properties such as high wear resistance and high hardness. In this study laser-boriding was applied to improve these properties. Laser alloying was conducted as the two step process with two different types of alloying material: amorphous boron only and amorphous boron with addition of calcium fluoride CaF2. At first, the surface was coated with paste including alloying material. Second step of the process consisted in laser re-melting. The surface of sample, coated with the paste, was irradiated by the laser beam. In this study, TRUMPF TLF 2600 Turbo CO2 laser was used. The microstructure, microhardness and wear resistance of both laser-borided layer and laser-borided layer with the addition of calcium fluoride were investigated. The layer, alloyed with boron and CaF2, was characterized by higher wear resistance than the layer after laser boriding only.

scholarly journals Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 2: Two-Phase Ejectors

Inventions ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 16 ◽  
Author(s):  
Zine Aidoun ◽  
Khaled Ameur ◽  
Mehdi Falsafioon ◽  
Messaoud Badache
Keyword(s):  
Heat Pumps ◽  
Operating Conditions ◽  
Industrial Processes ◽  
Experimental Investigations ◽  
Mixing Enhancement ◽  
Data Generation ◽  
Two Phase ◽  
Wide Range ◽  
Potential Applications ◽  
And Performance

Two-phase ejectors play a major role as refrigerant expansion devices in vapor compression systems and can find potential applications in many other industrial processes. As a result, they have become a focus of attention for the last few decades from the scientific community, not only for the expansion work recovery in a wide range of refrigeration and heat pump cycles but also in industrial processes as entrainment and mixing enhancement agents. This review provides relevant findings and trends, characterizing the design, operation and performance of the two-phase ejector as a component. Effects of geometry, operating conditions and the main developments in terms of theoretical and experimental approaches, rating methods and applications are discussed in detail. Ejector expansion refrigeration cycles (EERC) as well as the related theoretical and experimental research are reported. New and other relevant cycle combinations proposed in the recent literature are organized under theoretical and experimental headings by refrigerant types and/or by chronology whenever appropriate and systematically commented. This review brings out the fact that theoretical ejector and cycle studies outnumber experimental investigations and data generation. More emerging numerical studies of two-phase ejectors are a positive step, which has to be further supported by more validation work.

scholarly journals Development and Testing of Woven FRP Flexure Hinges for Pressure-Actuated Cellular Structures with Regard to Morphing Wing Applications

Aerospace ◽  
2019 ◽  
Vol 6 (11) ◽  
pp. 116
Author(s):  
Patrick Meyer ◽  
Johannes Boblenz ◽  
Cornelia Sennewald ◽  
Michael Vorhof ◽  
Christian Hühne ◽  
...  
Keyword(s):  
Operating Conditions ◽  
Cellular Structures ◽  
High Lift ◽  
Reinforced Plastics ◽  
Flexure Hinges ◽  
Key Factor ◽  
Potential Applications ◽  
Fiber Reinforced Plastics ◽  
The One ◽  
External Forces

Shape-variable structures can change their geometry in a targeted way and thus adapt their outer shape to different operating conditions. The potential applications in aviation are manifold and far-reaching. The substitution of conventional flaps in high-lift systems or even the deformation of entire wing profiles is conceivable. All morphing approaches have to deal with the same challenge: A conflict between minimizing actuating forces on the one hand, and maximizing structural deflections and resistance to external forces on the other. A promising concept of shape variability to face this challenging conflict is found in biology. Pressure-actuated cellular structures (PACS) are based on the movement of nastic plants. Firstly, a brief review of the holistic design approach of PACS is presented. The aim of the following study is to investigate manufacturing possibilities for woven flexure hinges in closed cellular structures. Weaving trials are first performed on the material level and finally on a five-cell PACS cantilever. The overall feasibility of woven fiber reinforced plastics (FRP)-PACS is proven. However, the results show that the materials selection in the weaving process substantially influences the mechanical behavior of flexure hinges. Thus, the optimization of manufacturing parameters is a key factor for the realization of woven FRP-PACS.

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