Thermally Induced Seizures of Journal Bearings

1989 ◽  
Vol 111 (2) ◽  
pp. 288-292 ◽  
Author(s):  
K. F. Dufrane ◽  
J. W. Kannel
Keyword(s):  
Journal Bearings ◽  
Supply System ◽  
Simple Theory ◽  
Thermally Induced ◽  
Start Up ◽  
Theoretical Predictions ◽  
Bearing Friction

The paper presents a simple theory for predicting seizure times for journal bearings. Under conditions of insufficient lubrication when bearing friction is high, seizure is predicted to occur in less than 20 seconds of operation. Insufficient lubrication can occur during bearing start-up, application of unusual loads, or as a result of an interruption of the lubricant supply system. Three examples where bearing seizure has been observed are discussed and the actual times to seize are compared with theoretical predictions. The actual seizure times are slightly less than predicted by theory, which is probably the result of bearing imperfections or uneven loading not considered in the theory.

On Thermally Induced Seizure in Journal Bearings

1989 ◽  
Vol 111 (4) ◽  
pp. 661-667 ◽  
Author(s):  
M. M. Khonsari ◽  
H. J. Kim
Keyword(s):  
Thermal Expansion ◽  
Journal Bearings ◽  
Complete Loss ◽  
Thermally Induced ◽  
Bearing Clearance ◽  
Start Up ◽  
Shaft Misalignment

Rapid thermal expansion of the shaft during the start-up period can lead to a complete loss of bearing clearance and seizure in the absence of lubrication. The equations governing the transient thermoelastic behavior of the shaft are solved numerically. Results are provided for the time of seizure as a function of displacement. It is shown that the presence of shaft misalignment can significantly influence the time of seizure.

Model-Based Investigation of Friction During Start-Up of Hydrodynamic Journal Bearings

1995 ◽  
Vol 117 (4) ◽  
pp. 667-673 ◽  
Author(s):  
A. Harnoy
Keyword(s):  
Friction Model ◽  
Journal Bearings ◽  
Time Variable ◽  
Stribeck Curve ◽  
Dynamic Friction ◽  
Stick Slip ◽  
Friction Characteristics ◽  
Start Up ◽  
Variable Friction ◽  
Steady Velocity

An analysis is developed for the time-variable friction during the start-up of a rotor system. The analysis is based on a dynamic friction model that has been developed from the theory of unsteady lubrication and can describe the observed friction characteristics. The model reduces to the Stribeck curve of friction versus steady velocity, and shows hysteresis curves in oscillating velocity. The “Dahl effect” of a presliding displacement before the breakaway is also included. The results indicate that the friction characteristics and energy friction losses, during the start-up, depend on a set of dimensionless parameters that represent the bearing as well as the dynamic system. The study shows that appropriate design and operation can prevent stick-slip friction and minimize wear during start-up.

Report Paper 2: Approximate Short Bearing Analysis and Experimental Results Obtained Using Plastic Bearing Liners

1969 ◽  
Vol 184 (12) ◽  
pp. 190-196 ◽  
Author(s):  
J. P. O'Donoghue ◽  
P. R. Koch ◽  
C. J. Hooke
Keyword(s):  
Approximate Solution ◽  
Film Thickness ◽  
Journal Bearings ◽  
Experimental Results ◽  
Approximate Theory ◽  
Hydrodynamic Problem ◽  
Dynamic Conditions ◽  
Oil Film ◽  
Theoretical Predictions ◽  
Bearing Analysis

This paper outlines a new approximate theory for liquid lubricated plain journal bearings with elastic liners. This is a modified form of Ocvirk's theory and includes the effect of circumferential flow. The results of a series of tests on short plastic bearings are presented to compare with the theoretical predictions of the new theory. The authors conclude that for short bearings the theory gives reasonably good predictions of performance, but the elasticity assumptions cause major errors for length/diameter ratios greater than 0·5 due to the decrease in oil film thickness that occurs near the ends of the bearing. The approximate solution adopted for the hydrodynamic problem may be of use for considering dynamic conditions taking the Reynolds conditions for cavitation.

Thermal Behavior and Friction in Journal Bearings

1970 ◽  
Vol 92 (3) ◽  
pp. 373-380 ◽  
Author(s):  
Al. Nica
Keyword(s):  
Experimental Data ◽  
Thermal Behavior ◽  
Heat Dissipation ◽  
Journal Bearings ◽  
Friction Torque ◽  
Operating Characteristics ◽  
Lubricant Flow ◽  
Theoretical Predictions ◽  
Theoretical Results ◽  
Good Agreement

This paper deals with friction and the field of temperature in the lubricant film of journal bearings. Theoretical results regarding the thermal behavior are checked with experimental data and good agreement is found. Emphasis is put on the variation of temperature and lubricant flow with the operating characteristics of the bearing and it is seen that theoretical predictions for minima of friction torque are backed by temperature measurements. Further on, the friction torque and the mechanism of heat dissipation in bearings are dealt with, in order to verify the assumptions used in the calculation schemes. The means of efficiently cooling the bearing are also discussed, as well as the part played by the divergent zone in this process.

scholarly journals Experimental Aspects in the Vibration-Based Condition Monitoring of Large Hydrogenerators

2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Geraldo Carvalho Brito Junior ◽  
Roberto Dalledone Machado ◽  
Anselmo Chaves Neto ◽  
Mateus Feiertag Martini
Keyword(s):  
Condition Monitoring ◽  
Accurate Determination ◽  
Cooling Water ◽  
Journal Bearings ◽  
Operating Conditions ◽  
Normal Operation ◽  
Steady State Condition ◽  
Dimensional Changes ◽  
Cooling Water Temperature ◽  
Theoretical Predictions

Based on experimental observations on a set of twenty 700 MW hydrogenerators, compiled from several technical reports issued over the last three decades and collected from the reprocessing of the vibration signals recorded during the last commissioning tests, this paper shows that the accurate determination of the journal bearings operating conditions may be a difficult task. It shows that the outsize bearing brackets of large hydrogenerators are subject to substantial dimensional changes caused by external agents, like the generator electromagnetic field and the bearing cooling water temperature. It also shows that the shaft eccentricity of a journal bearing of a healthy large hydrogenerator, operating in steady-state condition, may experience unpredictable, sudden, and significant changes without apparent reasons. Some of these phenomena are reproduced in ordinary commissioning tests or may be noticed even during normal operation, while others are rarely observed or are only detected through special tests. These phenomena modify journal bearings stiffness and damping, changing the hydrogenerator dynamics, creating discrepancies between theoretical predictions and experimental measurements, and making damage detection and diagnostics difficult. Therefore, these phenomena must be analyzed and considered in the application of vibration-based condition monitoring to these rotating machines.

scholarly journals МИНИМИЗАЦИЯ ВРЕМЕНИ ПОДГОТОВКИ РАБОЧЕГО ТЕЛА К ЗАПУСКУ ДВИГАТЕЛЬНОЙ УСТАНОВКИ С ЭЛЕКТРОНАГРЕВНЫМ ДВИГАТЕЛЕМ

2020 ◽  
pp. 4-11
Author(s):  
Андрей Владимирович Погудин ◽  
Сергей Викторович Губин
Keyword(s):  
Energy Balance ◽  
Power Supply ◽  
Power Supply System ◽  
Electric Heating ◽  
Supply System ◽  
Propulsion System ◽  
Working Fluid ◽  
Start Time ◽  
Start Up ◽  
Limited Power

The subject of the research in the article is the process of preparing the working fluid for launching an engine installation with an electric heating engine. The goal is to minimize the time for preparing the working fluid for launch by developing an algorithm for thermostating and barostating of elements of a propulsion system with limited power of the power supply system. Tasks: analysis of the structure of a propulsion system with an electric heating engine, selection of an installation control controller, the formation of an algorithm for preparing the working fluid for the first launch, the study of the reserve time for preparing the working fluid for launch with limited power supply system, the formation of an algorithm for minimizing the starting time. The methods used are: circuit analysis, energy balance and algorithmic analysis. The following results were obtained: the structural diagram of the propulsion system was analyzed, a control unit based on the Arduino Leonardo controller was selected, the first start-up algorithm was compiled, which consisted of the barostatting of the tank, thermostatting of the steam generator, barostatting of the receiver, and thermostatting of the electric heating engine; A start-up cyclogram with reduced time was constructed, an algorithm with a minimum start-up time of the propulsion system was formed. The scientific novelty of the results is as follows: the procedures included in the algorithm for preparing the working fluid for the first launch of the propulsion system are formed, a cyclogram for preparing the working fluid for the first launch is constructed, a cyclogram for reducing the time for preparing the working fluid for the first launch of the installation is constructed based on the energy balance of power consumption with limitation power plant output parameters, an algorithm for reducing the preparation time of the working fluid for the first launch of a propulsion system with an electric heating engine was built, the value of the start time was established by the modified first start algorithm with limited values of the power supply system.

scholarly journals Oscillation damping in the powertrain unit of transport vehicles

2019 ◽  
Vol 287 ◽  
pp. 01021
Author(s):  
Alexander Taratorkin ◽  
Viktor Derzhanskii ◽  
Igor Taratorkin
Keyword(s):  
Control System ◽  
Steady State ◽  
Supply System ◽  
Control Algorithms ◽  
System Control ◽  
Fuel Supply ◽  
Start Up ◽  
Oscillation Damping ◽  
Engine Start ◽  
Oscillatory Processes

The paper presents the results of an analytical experimental research of conditions for excitation of oscillatory processes in steady-state conditions and in the process of starting-up an engine equipped with a modern Common Rail fuel supply control system. Based on the results of mathematical simulation, the dependence of the dynamic torque amplitude on boosting acceleration during engine start-up and on the parameters of the elastic-dissipative coupling (connection) of the engine with the transmission is analyzed. It establishes the rationale for a possibility of optimizing the fuel supply system control algorithms for a modern diesel engine, taking into consideration the dependence of the process on the properties of the transmission and the peculiarities of its operation.

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