Wyniki wyszukiwania - BazTech

1

Numerical investigation on the vibration reduction of rotating shaft using different groove shapes of tilt bearing

Abbood Ahmed Imad, Abdulla Fadhel Abbas

Diagnostyka

|

2023

|

Vol. 24, No. 3

art. no. 2023304

EN

Vibration control is very important for high-speed rotors. Oil film damping is considered an effective vibration-damping method, especially for long shafts in gas turbines, ships, and other high-speed rotating equipment. The existing groove in the internal surface of the tilt bearing increases the amount of oil that flows through the bearing; this is more effective in suppressing the vibration of the rotor system carried by the plain bearing. In order to suppress the vibration of the rotor system, which is supported by sliding bearings, a different groove-shaped oil flow (GSOF) is studied and analysed in this paper. A different shape of grooves in bearings was set up and measured to study the vibration-damping effect of the flow oil shape with GSOF. ANSYS software presents significant benefits to engage Fluent for oil flow with Transient structural for vibration measurements. This paper uses these terms to perform the simulation numerically to explore the groove-shaped damper's damping effect under the rotor system. The study identified three enhancements of vibration and settling time. First, the circular groove showed a 35.71% reduction in amplitude and 10% increase in stilling time; the next one is the circular groove which reduced the amplitude by 42.85% and the settling time by 0%. The third modification was the inclined groove which reduced the amplitude by 42.85% and the settling time by 12%. The last one was the triple-inclined groove, which reduced the amplitude and settling time by 57.14% and 20%, respectively.

2

The impact estimation of damping foundations in dynamics of the rotor system

Grządziela A., Kluczyk M.

Diagnostyka

|

2017

|

Vol. 18, No. 3

55--61

EN

The paper presents results of dynamic researches conducted on test bed of rotor system. The aim of research was to identify the impact of damping washers to natural frequency of the system. The first part of paper treats with measurements of rotor system in non-stationary states and the second one is about vibration performances parameters in stationary states. Article presents an example of approach to the problem conducted in laboratory conditions, the results of which can be easily transferred on board of a ship or vessel.

PL

W artykule przedstawiono wyniki badań przeprowadzonych na stanowisku modelowym układu wirującego. Celem badań było zidentyfikowanie wpływu podkładek tłumiących na częstotliwość rezonansową systemu. W pierwszej część pracy zaprezentowano wyniki uzyskane podczas pomiarów parametrów drganiowych w czasie pracy układu wirnikowego w stanach nieustalonych, natomiast druga dotyczy parametrów drgań w stanie ustalonym. Artykuł przedstawia przykład podejścia do problemu prowadzonego w warunkach laboratoryjnych, którego wyniki można łatwo zaimplementować podczas pomiarów na okrętach lub innych jednostkach pływających.

3

Determination of critical speeds of a centrifugal pump impeller in annular seals

Kundera C., Marcinkowski W. A.

International Journal of Applied Mechanics and Engineering

|

2012

|

Vol. 17, no. 3

873-883

EN

The paper deals with combined transverse and angular vibrations of a single-disc impeller in annular seals. The formulated equations of vibrations include additional (i.e., inertia, damping, potential, gyroscopic and circular) hydrodynamic forces and moments occurring in clearances of non-contact seals. The study involved performing digital calculations to determine the natural frequencies in two models of the rotor, both for constant pressure drops in seals and for a square relationship between the pressure drops and the rotational frequency of the impeller. It was also necessary to estimate the influence of the conicity of the annular clearance gaps in non-contacting seals on the natural and critical frequencies of the rotor.

4

Mathematical modelling of a long squeeze film magnetorheological damper for rotor systems

Zapomel J., Ferfecki P.

Modelling and Optimization of Physical Systems

|

2010

|

z. 9

97--102

EN

Lateral vibration of rotor systems can be efficiently reduced by damping devices included between the rotor and the stationary part of the rotating machine. To achieve their optimum performance the damping effect must be controllable. This is enabled by magnetorheological dampers. Their damping depends on resistance against the flow of the magnetorheological liquid which can be controlled by the change of intensity of the magnetic field. This paper deals with the procedure for determination of the pressure distribution in the gap of a long squeeze film magnetorheological damper and with investigation of its behaviour by means of computational simulations. The results show that the developed model has all properties of real magnetorheological dampers observed during their operation.

CS

Příčné kmitání rotorů může byt učinne tlumeno tlumicími zařízenimi umistenymi mezi rotující a stacionární čast rotorové soustavy. Aby se dosáhlo jejich optimálního vykonu, musí byt tlumicí učinek řiditelny. To je umožneno použitím magnetoreologickych tlumičů. Jejich tlumicí učinek závisí na odporu proti proudení magnetoreologické kapaliny, ktery může byt řízen zmenou intenzity magnetického pole. Předloženy článek se zabyva postupem pro stanovení tlakoveho rozložení v mezeře dlouhého squeeze filmového magnetoreologického tlumiče a zkoumáním jeho chování cestou počítačovych simulací. Vysledky ukazují, že vypracovany matematicky model pokryvá vsechny podstatne vlastnosti magnetoreologickych tlumičů pozorované při jejich provozu.

5

The effect of annular seal parameters on the dynamics of a rotor system

Kundera C., Marcinkowski W. A.

International Journal of Applied Mechanics and Engineering

|

2010

|

Vol. 15, no 3

719-730

EN

The paper analyzes the influence of annular seal parameters on the critical angular velocity and the dynamic stability of rotor system consisting of a shaft and a symmetrical impeller rotating in two seals. The equations of motion of the rotor system were formulated. The special model developed to describe the seal fluid forces takes into account not only the stiffness and damping forces but also the inertial, gyroscopic and circulatory forces. The calculation results show that the clearance shape has a considerable effect on the critical velocity of the rotor. The greater the pressure drop in the seal, the greater the influence of the clearance conicity.

6

Numerical simulation of feedback controlled fluid-induced instabilities in rotor system supported by hydrodynamic bearings

Ferfecki P., Sikora R., Poruba Z.

Archives of Control Sciences

|

2010

|

Vol. 20, no. 3

287-301

EN

In certain operating conditions, the oil-film forces, by which the hydrodynamic bearings act on the rotor, destabilize and induce a self-excited vibration. There are many solution based on modifications of the bearing geometry to enlarge the operational range of the hydrodynamic bearing as a tilting pad bearing, lemon bore, etc. or usage of the dampers whose operation is based only on the dissipation of mechanical energy. In this paper several concepts based on controlled kinematic excitation of the bearing shells is investigated by computer simulation and by experimental test. The mathematical model of the uncontrolled and controlled rotor system contains the nonlinear hydrodynamic forces determined by the solution of the Reynolds equation assuming short case of bearing. To solve the equation of motion the Runge-Kutta method of the 4th order with Dormand-Prince modification and variable length of the integration step is used. The computer simulations were performed for rotor system without feedback control and with feedback controller. The main objectives of the numerical analysis were determination of the stability regions of the vibration excited by the imbalance forces. Results of the computer simulations proved that the analyzed approaches reduce amplitude of the rotor vibration caused by the imbalance forces. Experimental test and computer simulations demonstrate that the active vibration control increases considerably the rotation speed when the self-excited vibration of the oil-film occurred.

7

Research on rotary system with tilting-pad journal bearings

Vekteris V., Cereska A.

Archive of Mechanical Engineering

|

2008

|

Vol. LV, nr 1

5-12

EN

This paper presents the results of research on self-vibrations of rotary systems with segmental tilting-pad journal bearings having different frequencies of rotor revolution. The problem of research formulated in this work concerns technical characteristics of primary elements of the investigated system and its principle of operation. The obtained results are illustrated with graphs. The paper also contains comparison of results and discussion. General conclusions are given at the end of the paper.

PL

W pracy przedstawiono wyniki badań drgań własnych w systemach obrotowych z segmentowymi łożyskami ślizgowymi, pracującymi przy różnych częstotliwościach obrotów wirnika. Sformułowano problem badawczy, który dotyczy charakterystyk technicznych podstawowych elementów badanego systemu i jego zasady działania. Uzyskane wyniki zilustrowano wykresami. W pracy zamieszczono także porównanie wyników i dyskusję. Ogólne wnioski sformułowano w końcowej części artykułu.

8

Numerical investigation of a response of the rotor KJT4 (RK4) with a fatigue crack excited by centrifugal forces due to the disk unbalance

Ferfecki P., Ondrouch J.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

|

2006

|

z. 31

11-14

EN

A method of computational modelling is applicd for invcstigation of influence of transverse fatigue crack located in the midspan of rotor system RK 4. The response of rotor system RK 4 is computed from equations of motion derived in the rotor-fixed co-ordinate system utilizing the Runge-Kutta method of the 4th order. The influence of the crack in rotor system is investigated by means of frequency spectra obtained from time domain response.

9

Numerical evaluation of amplitude-frequency characteristic of linear rotor system using distributed computation

Musil T.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

|

2006

|

z. 31

107-110

EN

Using distributed computation is numerically assembled amplitude-frequency characteristic of the linear rotor system. Evaluation is performed on a parallel computer with distributed memory and with eight processors.

10

Estimation of the critical velocities of the rotor systems containing random parameters

Dupal J.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

|

2004

|

z. 25

39-42

EN

The paper deals with an approach to statistic estimation of mean, standard deviation and variance of the rotor system critical velocities by means of perturbation method. The model of the rotor takes into account inner damping (Kelvin - Voigth material), rotary inertia and gyroscopic effect. The random parameters are geometrical and material parameters of the rotor system whose mean, variances and cross covariances are known as the inputs.

PL

W pracy przedstawiono metodę statystycznego oszacowania wartości średniej, odchylenia standardowego i wariancji prędkości krytycznych dla rozpatrywanych układów za pomocą metody zaburzeń. Prezentowany w artykule model wirnika uwzględnia wewnętrzne tłumienie, bezwładność wirnika i efekt żyroskopowy. Losowe parametry to parametry geometryczne i materiałowe układu wirnika, których wartości średnie, wariancje kowariancje wzajemne są znane.

11

Some Dynamic Effects of Gear Couplings in Rotor Systems

Brommundt E.

Machine Dynamics Problems

|

2004

|

Vol. 28, No. 1

41-44

EN

This is a brief survey on dynamic effects due to the presence of a strongly non-linear gear coupling in an otherwise linear rotor system. Numerical results show strong influences of the gear coupling on the system behavior, and a high sensitivity to parameter variations. Proper misalignment can stabilize the rotor (the model of the gear coupling characteristic is the topic of a paper under preparation).

12

The judgement of stability of non-linear rotor systems with a flexible shaft and a stationary part

Zapoměl J.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

|

2001

|

z. 17

237-244

EN

Motion of a rotor system operating close to a stability limit can tend to jump between different attractors. Such working conditions are undesirable especially from the point of view of control. If a rotor supported by hydrodynamical bearings yibrates periodically, then its equation of motion can be considered as linear but with coefficients that are periodic functions of time. In this case analysis of stability of the vibration comes from a Floquet theory. The motion is stable if magnitudes of all eigenvalues of the transition matrix assigned to the investigated system are less than 1. Periodic solution of the equation of motion can be obtained for a certain class of problems by means of a trigonometric collocation method.

PL

Ruch układu wirnikowego pracujący w pobliżu granicy stabilności może powodować przeskoki pomiędzy różnymi atraktorami. Takie warunki pracy są niepożądane zwłaszcza z punktu widzenia sterowania układu. Jeśli wirnik osadzony w łożyskach hydrodynamicznych drga okresowo, wówczas jego równanie ruchu może być uważane za liniowe, ale współczynniki tego równania są okresowymi funkcjami czasu. W tym przypadku ta analiza stabilności drgań opiera się na teorii Floqueta. Ruch jest stabilny jeśli wartości bezwzględne wszystkich wartości własnych wyznaczonej macierzy przejścia dla badanego układu są mniejsze niż 1. Rozwiązanie okresowe równania ruchu można uzyskać dla pewnej grupy zagadnień przy pomocy trygonometrycznej metody kolokacji.

13

Diagnostic structural model of rotor system

Drożyner P., Michalski R.

Prace Naukowe Instytutu Górnictwa Politechniki Wrocławskiej. Konferencje

|

1999

|

Vol. 86, nr 24

112-117

EN

The stages of building the diagnostic structural model of the rotor system on the example of a rotary mower were presented in the paper. The model was developed on the base of preliminary research, which allowed to assume, that the considered system is the object with two degrees of freedom. On the base of the created physical model, the mathematical model was developed with use of the Lagrange equations. The coefficients of the equations ware established on the base of the results of carried out active experiment. The relation between state and signal obtained that way is the diagnostic structural model of rotary mower. The model, together with established limit values makes possible to evaluate the technical state of rotary drums of a mower.