The Onset of Whirl Instability in Journal Bearings of Various Bore Shapes and Groove Sizes

1983 ◽  
Vol 105 (3) ◽  
pp. 342-352 ◽  
Author(s):  
M. Akko¨k ◽  
C. M. McC. Ettles
Keyword(s):  
Beneficial Effect ◽  
Load Capacity ◽  
Journal Bearings ◽  
Experimental Results ◽  
General Validity ◽  
Model Based ◽  
Linearized Model ◽  
Varying Viscosity

Experimental results are given for load capacity and whirl onset in journal bearings of circular, elliptical and offset halves bore shape. The general validity of the linearized model for predicting whirl is confirmed experimentally. Deviations between experimental results and the model, based on an isoviscous film, are attributed to the varying viscosity that occurs in practice, and to unavoidable excitation that gives rise to premature whirl. It is shown that increasing groove size has a destabilizing effect that can more than cancel the beneficial effect of preloading. This result is particularly relevant to the design of journal bearings in turbomachinery.

Orifice Restrictor Losses in Journal Bearings

1979 ◽  
Vol 193 (1) ◽  
pp. 47-52 ◽  
Author(s):  
E. G. Pink ◽  
K. J. Stout
Keyword(s):  
Radial Flow ◽  
Load Capacity ◽  
Journal Bearings ◽  
Experimental Results ◽  
Pressure Recovery ◽  
Pressure Profiles ◽  
Compensation Factor ◽  
Good Agreement

Details of a study concerning orifice restrictor losses in externally pressurized gas lubricated journal bearings are given. The type of compensation considered is the pocketed orifice design. The analysis presented includes the effects of pressure recovery in the pocket and entrance loss effects at inlet to the bearing film. Also, by treating the flow in the bearing film local to the pocket as radial flow, the effect of dispersion is accounted for. It is shown that good agreement exists between computed and experimental results in pressure profiles and also for load capacity up to touch-down conditions. From the analysis, the effect of the inherent compensation factor, number of orifices and pocket diameter on load capacity is discussed.

Rotordynamic and Bearing Upgrade of a High-Speed Turbocharger

2002 ◽  
Vol 125 (1) ◽  
pp. 95-101 ◽  
Author(s):  
B. C. Pettinato ◽  
P. DeChoudhury
Keyword(s):  
High Speed ◽  
Thrust Bearing ◽  
Load Capacity ◽  
Journal Bearings ◽  
Experimental Results ◽  
Thrust Bearings ◽  
Vibration Data ◽  
Oil Leakage ◽  
Bearing Life ◽  
Thrust Load

The paper discusses the redesign of a high-speed turbocharger for improved bearing life and mechanical operation. The bearings were changed from a pair of combination journal/thrust bearings to a pair of redesigned journal bearings with double acting thrust bearing at the center of the unit. Internal oil passages, drain cavities, and seals were also revised. These modifications resulted in reduced oil leakage across end seals, reduced coke buildup at the turbine, increased thrust load capacity, and improved rotordynamics. Both the analytical and experimental results, which consisted of bearing performance and vibration data of original and modified systems are presented.

scholarly journals Generalized analytical model based on harmonic coupling for hybrid plasmonic modes: comparison with numerical and experimental results

2015 ◽  
Vol 23 (21) ◽  
pp. 27376 ◽  
Author(s):  
Mitradeep Sarkar ◽  
Jean-François Bryche ◽  
Julien Moreau ◽  
Mondher Besbes ◽  
Grégory Barbillon ◽  
...  
Keyword(s):  
Analytical Model ◽  
Experimental Results ◽  
Model Based

scholarly journals Difficulties in Comprehending Affirmative and Negative Sentences: Evidence From Chinese Children With Reading Difficulties

2017 ◽  
Vol 51 (2) ◽  
pp. 181-193 ◽  
Author(s):  
Shenai Hu ◽  
Maria Vender ◽  
Gaetano Fiorin ◽  
Denis Delfitto
Keyword(s):  
Mandarin Chinese ◽  
Reading Difficulties ◽  
Judgment Task ◽  
Experimental Results ◽  
Chinese Children ◽  
Behavioral Data ◽  
Poor Readers ◽  
Value Judgment ◽  
General Validity ◽  
Truth Value

Recent experimental results suggest that negation is particularly challenging for children with reading difficulties. This study looks at how young poor readers, speakers of Mandarin Chinese, comprehend affirmative and negative sentences as compared with a group of age-matched typical readers. Forty-four Chinese children were tested with a truth value judgment task. The results reveal that negative sentences were harder to process than affirmative ones, irrespective of the distinction between poor and typical readers. Moreover, poor readers performed worse than typical readers in comprehending sentences, regardless of whether they were affirmative or negative sentences. We interpret the results as (a) confirming the two-step simulation hypothesis, based on the result that the difficulty in processing negation has a general validity (persisting in pragmatically felicitous contexts), and (b) disconfirming that negation, as far as behavioral data are concerned, can be used as a reliable linguistic predictor of reading difficulties.

scholarly journals Research of Personalized Recommendation Technology Based on Knowledge Graphs

2021 ◽  
Vol 11 (15) ◽  
pp. 7104
Author(s):  
Xu Yang ◽  
Ziyi Huan ◽  
Yisong Zhai ◽  
Ting Lin
Keyword(s):  
Neural Network ◽  
Hot Spot ◽  
Experimental Results ◽  
Graph Representation ◽  
Personalized Recommendation ◽  
Knowledge Graph ◽  
Learning Technology ◽  
Data Set ◽  
Model Based ◽  
Knowledge Graphs

Nowadays, personalized recommendation based on knowledge graphs has become a hot spot for researchers due to its good recommendation effect. In this paper, we researched personalized recommendation based on knowledge graphs. First of all, we study the knowledge graphs’ construction method and complete the construction of the movie knowledge graphs. Furthermore, we use Neo4j graph database to store the movie data and vividly display it. Then, the classical translation model TransE algorithm in knowledge graph representation learning technology is studied in this paper, and we improved the algorithm through a cross-training method by using the information of the neighboring feature structures of the entities in the knowledge graph. Furthermore, the negative sampling process of TransE algorithm is improved. The experimental results show that the improved TransE model can more accurately vectorize entities and relations. Finally, this paper constructs a recommendation model by combining knowledge graphs with ranking learning and neural network. We propose the Bayesian personalized recommendation model based on knowledge graphs (KG-BPR) and the neural network recommendation model based on knowledge graphs(KG-NN). The semantic information of entities and relations in knowledge graphs is embedded into vector space by using improved TransE method, and we compare the results. The item entity vectors containing external knowledge information are integrated into the BPR model and neural network, respectively, which make up for the lack of knowledge information of the item itself. Finally, the experimental analysis is carried out on MovieLens-1M data set. The experimental results show that the two recommendation models proposed in this paper can effectively improve the accuracy, recall, F1 value and MAP value of recommendation.

An Approximate THD Theory for Journal Bearings

1990 ◽  
Vol 112 (2) ◽  
pp. 224-229 ◽  
Author(s):  
G. Gupta ◽  
C. R. Hammond ◽  
A. Z. Szeri
Keyword(s):  
Journal Bearing ◽  
Load Capacity ◽  
Pressure Coefficient ◽  
Journal Bearings ◽  
Maximum Pressure ◽  
Substantial Agreement ◽  
Interactive Mode ◽  
Lubricant Flow ◽  
Bearing Load ◽  
Sophisticated Model

The aim of this paper is to make available to the industrial designer results of the thermohydrodynamic theory of journal bearings, by providing a simplified, yet accurate model of journal bearing lubrication that can be implemented on a personal computer and be used in an interactive mode. The simplified THD theory we propose consists of two coupled ordinary differential equations for pressure and energy and an algebraic equation for viscosity, which are to be solved iteratively. Bearing load capacity, maximum bearing temperature, maximum pressure, coefficient of friction and lubricant flow rate calculated from this simplified theory compare well with results from a more sophisticated model. We also make comparisons with experimental data on full journal bearings, demonstrating substantial agreement between experiment and simplified theory.

Geometric Effects on Eddy Current Bearing Performance

1989 ◽  
Vol 111 (2) ◽  
pp. 209-214 ◽  
Author(s):  
J. A. Tichy ◽  
K. A. Connor
Keyword(s):  
Eddy Current ◽  
Eddy Currents ◽  
Load Capacity ◽  
Complex Mixture ◽  
Journal Bearings ◽  
Magnetic Bearings ◽  
Repulsive Forces ◽  
The Magnetic Field ◽  
Geometric Effects ◽  
Current Journal

The properties of magnetic bearings, particularly those based on repulsive forces due to eddy currents, are determined by a complex mixture of electrical and mechanical length and time scales. A perturbation solution for the magnetic field structure based on careful ordering of these parameters has permitted the effects of realistic gap geometries to be analyzed. The load capacity of eddy current journal bearings is found to be somewhat larger than previously predicted in an earlier paper which used magnetic fields based on constant gap size. The present results may be of interest to those concerned with calculating eddy currents in conventional attractive magnetic bearings.

An Analysis of Conventional and Self-Aligned four Terminal Resistor Structures for The Determination of The Contact Resistivity from End Resistance Measurements

1986 ◽  
Vol 71 ◽  
Author(s):  
I. Suni ◽  
M. Finetti ◽  
K. Grahn
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Computer Model ◽  
Contact Resistivity ◽  
Experimental Results ◽  
The Finite Element Method ◽  
Model Based ◽  
A Value ◽  
And Diffusion

AbstractA computer model based on the finite element method has been applied to evaluate the effect of the parasitic area between contact and diffusion edges on end resistance measurements in four terminal Kelvin resistor structures. The model is then applied to Al/Ti/n+ Si contacts and a value of contact resistivity of Qc = 1.8×10−7.Ωcm2 is derived. For comparison, the use of a self-aligned structure to avoid parasitic effects is presented and the first experimental results obtained on Al/Ti/n+Si and Al/CoSi2/n+Si contacts are shown and discussed.

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