A Systems Approach to the Torsional Vibration of Multi-Cylinder Reciprocating Engines and Pumps

1994 ◽  
Vol 208 (6) ◽  
pp. 395-408 ◽  
Author(s):  
D C Hesterman ◽  
B J Stone
Keyword(s):  
Time Domain ◽  
Torsional Vibration ◽  
Natural Frequencies ◽  
Systems Approach ◽  
Angular Position ◽  
Rotary Inertia ◽  
Rotating Systems ◽  
Simulation Techniques ◽  
Reciprocating Engines ◽  
The Time Domain

The systems approach for the vibration analysis of complex systems requires that the receptances of the sub-systems are available. For the torsional vibration of rotating systems including reciprocating engines and/or pumps it has been the practice to represent the reciprocating mechanism by a constant rotary inertia. This paper describes the derivation of the receptance for such reciprocating mechanisms, which includes the effects of non-constant rotary inertia. It is then shown how the natural frequencies for torsional vibration vary with angular position and how this in turn affects the vibration in the time domain. The significance of the effects indicated by these simulation techniques is then demonstrated by comparing with results obtained from an experimental investigation.

Secondary Inertia Effects in the Torsional Vibration of Reciprocating Engines—A Literature Review

1995 ◽  
Vol 209 (1) ◽  
pp. 11-15 ◽  
Author(s):  
D C Hesterman ◽  
B J Stone
Keyword(s):  
Literature Review ◽  
Recent Work ◽  
Current Literature ◽  
Torsional Vibration ◽  
Angular Position ◽  
Inertia Effect ◽  
Secondary Resonance ◽  
Inertia Effects ◽  
Reciprocating Engines ◽  
The Subject

It has been known for some time that the torsional vibration of reciprocating engines and pumps cannot be modelled accurately by representing the reciprocating mechanism by a constant inertia. There have been many publications describing better models than those that use constant inertia and these indicate that the effective inertia of a reciprocating mechanism varies with angular position. The major component of this variation is a twice per revolution cyclic effect—hence the term ‘secondary inertia’. The consequences of this secondary inertia effect can be serious for torsional vibration causing ‘secondary resonance,’ and even instability. This paper contains a review of the current literature on the subject and introduces some recent work by the authors.

ACTIVE MULTIPLE TUNED MASS DAMPERS FOR REDUCTION OF UNDESIRABLE OSCILLATIONS OF STRUCTURES UNDER WIND LOADS

2009 ◽  
Vol 09 (01) ◽  
pp. 127-149 ◽  
Author(s):  
CHUNXIANG LI ◽  
BINGKANG HAN ◽  
JINGYI ZHANG ◽  
YAN QU ◽  
JINHUA LI
Keyword(s):  
Time Domain ◽  
Natural Frequencies ◽  
Wind Loads ◽  
Control Force ◽  
Tuned Mass Dampers ◽  
Vibration Mitigation ◽  
Simulation Results ◽  
The Time Domain ◽  
Control Forces ◽  
Multiple Tuned Mass Dampers

Active multiple tuned mass dampers (AMTMDs) consisting of several active tuned mass dampers (ATMDs) with uniform distribution of natural frequencies have been proposed for vibration mitigation of structures under wind loads. In this regard, the optimum parameter criterion is defined as the minimization of the root-mean-square (RMS) displacement and acceleration responses of the structure with the AMTMD. Meanwhile, the effectiveness criterion is defined as the ratio of the minimum RMS displacement and RMS acceleration of the structure with the AMTMD to those without the devices, respectively referred to as the displacement and acceleration reduction factors (DRF and ARF). With these two criteria, the influences of the selective parameters on the effectiveness and robustness of the devices for vibration control under wind loads are studied. In addition, the stroke of the AMTMD is examined by quantitatively assessing the RMS displacement of each ATMD. Results indicate that in comparison with a single ATMD, the AMTMD can cause more reduction in the displacement and acceleration responses of the structure under wind loads. The stroke of the AMTMD is greater based on the ARF than the DRF criterion. In particular, the simulation results in the time domain confirm that by resorting to the AMTMD, a large control force can indeed be decentralized into many smaller control forces without losing the level of response reduction.

scholarly journals Analysis of the sensitivity of the identification method of inability states of rotating systems to the conditions of the experiment

2021 ◽  
Vol 332 ◽  
pp. 01016
Author(s):  
Michał Pająk ◽  
Dragutin Lisjak ◽  
Marcin Kluczyk ◽  
Davor Kolar
Keyword(s):  
Time Domain ◽  
System Approach ◽  
Academic Research ◽  
Diagnostic Methods ◽  
Operational Environment ◽  
Technical Object ◽  
Operation Conditions ◽  
Rotating Systems ◽  
Industrial Implementation ◽  
The Time Domain

One of the most important subsystems of the vehicles and machines operating currently in industry and transportation are the rotating subsystems. Monitoring of its technical state is an important issue of the engineering and academic research. As a result of the research a lot of new diagnostic methods have been formulated but one of the most important characteristic of them is the ability to industrial implementation. It depends on the insensitivity to disturbance which can arise in real operational environment. In the paper the method formulated by the authors is analysed. This is the method of the identification of inability states of rotating subsystems based on the vibrations analyses in the time domain. It constitutes the system approach to the considered issue. There are three applications of the method described - research on simulation laboratory stand, research on a real technical object conducted in the laboratory and research carried out on a real technical object under the real operation conditions. In each case different accuracy of the ability and inability states identification is achieved. Analysing the differences in accuracy of the method applications the conclusion of its sensitivity to the conditions of the experiment were formulated which are presented in the end of the paper.

Forced Axial Vibration of a Single-Walled Carbon Nanotube Embedded in Elastic Medium under Various Moving Forces

2020 ◽  
Vol 63 ◽  
pp. 112-133 ◽  
Author(s):  
Farshad Khosravi ◽  
Seyyed Amirhosein Hosseini ◽  
Abdelouahed Tounsi
Keyword(s):  
Carbon Nanotube ◽  
Boundary Conditions ◽  
Elastic Medium ◽  
Time Domain ◽  
Natural Frequencies ◽  
Moving Load ◽  
Nonlocal Parameter ◽  
Single Walled Carbon Nanotube ◽  
Single Walled Carbon ◽  
The Time Domain

The dynamic free and forced axial vibrations subjected to moving exponential and harmonic axial forces of a single-walled carbon nanotube (SWCNT) embedded in an elastic medium, are studied in this paper. Two different boundary conditions of SWCNT, including clamped-clamped and clamped-free, are taken into account. Eringen’s nonlocal elasticity theory is used to show the nonlocality for the model. The constitutive equations and their boundary conditions are derived by Hamilton’s principle. Employing the general solution, the derived equations are analytically solved to obtain two items. Firstly, the axial natural frequencies, secondly, the time-domain axial displacements at the middle of the carbon nanotube (CNT), and then the maximum axial displacements. The responses are validated with previous works, and the results demonstrates good agreement to them to verify the influence of the nonlocal parameter on the nondimensional natural frequencies for three various mode numbers. In the time-domain section, the effects of the nonlocal parameter, length, nondimensional stiffness of the elastic medium, and velocity of the moving load on the axial displacement are investigated. Also, the influences of the excitation frequency to natural frequency for the harmonic moving load, as well as the time constant for the exponential moving load on the axial displacement, are illustrated. Finally, the effect of the nonlocal parameter on the maximum axial deflection versus velocity parameter is schematically indicated.

Vehicle Vibration Safety Evaluation in the Time Domain

2018 ◽  
pp. 1-15 ◽  
Author(s):  
L. F. Zheglov ◽  
A. B. Fominykh
Keyword(s):  
Dynamic System ◽  
Frequency Domain ◽  
Time Domain ◽  
Vibration Isolation ◽  
Natural Frequencies ◽  
Spectral Characteristics ◽  
Isolation System ◽  
Vibration Isolation System ◽  
Calculation Results ◽  
The Time Domain

The article is a sequel to studies of the nonlinear vibration isolation systems of a vehicle. The first published papers considered an application of the known methods of statistical linearization when determining the vibration safety performance in the frequency domain. The frequency domain is the most adaptive in the context of analysis of the obtained calculation results and evaluation of the initial dynamic system features. Therefore, a problem to determine the adequacy range of such calculations in the frequency and time domain is relevant.The paper deals with the problem of creating a technique to determine and analyze the spectral characteristics of the vehicle vibration isolation system when modeling in the time domain. Considers as an object, a nonlinear dynamic system equivalent to the nonlinear vibration isolation system of a vehicle under its spatial vibrations. In formulating a system of equations-of-motion of the adopted system a module-based method was used. As an example, the power unit is given. Modeling of input random perturbations, provided that the solutions obtained are adequate, is based on the recurrent difference equations. The subsequent transformation of the calculation results into the frequency domain is based on the finite Fourier transforms.To determine the final parameters which characterise the effectiveness of the vibration isolation system, at the first stage of calculations the dynamic system was tested in a linear setting.The vector of natural frequencies of a conservative system defined in the frequency domain was compared with the spectrum of natural frequencies (the frequency response) calculated in the time domain. Besides, the article has carried out a conformity evaluation of the amplitude-frequency characteristics obtained in the frequency and time domain and their determining accuracy. The obtained positive results made it possible to compare and analyze the spectral characteristics of vibration signals and dynamic system in its nonlinear and linearized formulation. The coherence function, the amplitude-frequency characteristic, the spectral density of perturbation and output vibration signal, the vehicle suspension and tyre load characteristics are considered as the analyzed ones. The article compares the output characteristics of the dynamic system under consideration for the case in linear, linearized, and nonlinear formulation of the problem.

scholarly journals Performance comparison between variants PID controllers and unity feedback control system for the response of the angular position of the DC motor

2021 ◽  
Vol 11 (1) ◽  
pp. 802
Author(s):  
Mustafa A. Mhawesh
Keyword(s):  
Time Domain ◽  
Pid Controller ◽  
Transfer Functions ◽  
Angular Position ◽  
Dc Motor ◽  
Performance Comparison ◽  
Pid Controllers ◽  
Pd Controller ◽  
Matlab Program ◽  
The Time Domain

This paper proposed a detailed study for the response of angular position of the rotor of a DC motor. It is a comparative analysis to the behavior of the DC motor when the motor is alone and when it is with controllers. Furthermore, a comparison between the responses of controllers themselves. A conventional PID controller which was tuned by using Ziegler and Nichols method was proposed in this paper. Also, Modification PID controllers were proposed in this paper. The modification PID controllers are PI-D controller and I-PD controller. Mathematical calculations were done to get the transfer functions for the DC motor and the controllers. Time domain specifications and figures were obtained for each case by using Matlab program. The obtained results were summarized in tables. This paper determined which the controller is the best one depending on the obtained figures and the time domain specifications.

Apodisation in the time domain

1992 ◽  
Vol 2 (4) ◽  
pp. 615-620
Author(s):  
G. W. Series
Keyword(s):  
Time Domain ◽  
The Time Domain

JOINT INTERPRETATION OF AIRBORNE ELECTROMAGNETIC DATA IN THE TIME DOMAIN AND FREQUENCY DOMAIN

2018 ◽  
Vol 12 (7-8) ◽  
pp. 76-83
Author(s):  
E. V. KARSHAKOV ◽  
J. MOILANEN
Keyword(s):  
Fourier Transform ◽  
Frequency Domain ◽  
Time Domain ◽  
Frequency Interval ◽  
Single Spectrum ◽  
Simultaneous Inversion ◽  
Homogeneous Half Space ◽  
Time Domain Data ◽  
The Time Domain

Тhe advantage of combine processing of frequency domain and time domain data provided by the EQUATOR system is discussed. The heliborne complex has a towed transmitter, and, raised above it on the same cable a towed receiver. The excitation signal contains both pulsed and harmonic components. In fact, there are two independent transmitters operate in the system: one of them is a normal pulsed domain transmitter, with a half-sinusoidal pulse and a small "cut" on the falling edge, and the other one is a classical frequency domain transmitter at several specially selected frequencies. The received signal is first processed to a direct Fourier transform with high Q-factor detection at all significant frequencies. After that, in the spectral region, operations of converting the spectra of two sounding signals to a single spectrum of an ideal transmitter are performed. Than we do an inverse Fourier transform and return to the time domain. The detection of spectral components is done at a frequency band of several Hz, the receiver has the ability to perfectly suppress all sorts of extra-band noise. The detection bandwidth is several dozen times less the frequency interval between the harmonics, it turns out thatto achieve the same measurement quality of ground response without using out-of-band suppression you need several dozen times higher moment of airborne transmitting system. The data obtained from the model of a homogeneous half-space, a two-layered model, and a model of a horizontally layered medium is considered. A time-domain data makes it easier to detect a conductor in a relative insulator at greater depths. The data in the frequency domain gives more detailed information about subsurface. These conclusions are illustrated by the example of processing the survey data of the Republic of Rwanda in 2017. The simultaneous inversion of data in frequency domain and time domain can significantly improve the quality of interpretation.

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