Effect of Gas Forces on Parametrically Excited Torsional Vibrations of Reciprocating Engines

2001 ◽  
Vol 45 (04) ◽  
pp. 262-268
Author(s):  
M. S. Pasricha
Keyword(s):  
Torsional Vibration ◽  
Parametrically Excited ◽  
Inertia Effects ◽  
Resonance Effects ◽  
The Past ◽  
Secondary Resonances ◽  
Reciprocating Engines ◽  
Marine Diesel ◽  
Crankshaft Rotation ◽  
Engine Systems

In the past the effects of ignoring the variable inertia characteristics of reciprocating engines on the accuracy of torsional vibration calculations were considered to be negligible. The associated secondary resonances tended to be dismissed by most engineers as interesting but of no importance. The situation changed in recent years, since there was evidence of the existence of the secondary inertia effects, which could have contributed to a number of otherwise inexplicable crankshaft failures in large multi-cylinder marine diesel engine systems. In view of these facts, a mathematical model is derived with key nondimensional parameters for the analysis of the effect of gas forces on the motion of the variable inertia system. The complex waveform responses are examined in detail within the range of speeds of engine rotation at which adverse effects are known to have occurred in practice. The effects on the parametrically excited motion of the system are investigated at a particular speed of the crankshaft rotation due to the action of external excitations with respect to changes in phase angle and inertia ratio. It is shown that under certain circumstances, interaction of secondary resonance effects with the excitations can be serious for torsional vibration. General comments on Draminsky's work in the light of present investigations are included.

scholarly journals Effect of the reciprocating mass of slider-crank mechanism on torsional vibrations of diesel engine systems

2017 ◽  
Vol 23 (1&2) ◽  
pp. 71
Author(s):  
M.S. Pasricha Pasricha ◽  
F.M. Hashim
Keyword(s):  
Torsional Vibration ◽  
Periodic Variation ◽  
Partial Explanation ◽  
Mean Values ◽  
Resonance Effects ◽  
Reciprocating Engine ◽  
Marine Engines ◽  
Marine Diesel ◽  
Engine Systems ◽  
Crank Mechanism

The torsional vibration phenomenon in the running gear of reciprocating engine systems isusually dealt with by considering a series of constant inertias connected by sections of massless shafting. However in reality, a slider crank mechanism is a vibrating system with varying inertia because the effective inertia of the total oscillating mass of each crank assembly varies twice per revolution of the crankshaft. Large variations in inertia torques can give rise to the phenomenonof secondary resonance in torsional vibration of modern marine diesel engines which can not be explained by conventional theory incorporating only the mean values of the varying inertias. In the past associated secondary resonances and regions of instability tended to be dismissed by most engineers as interesting but of no importance. The situation changed in recent years since there is evidence of the existence of thesecondary resonance effects which could have contributed to a number of otherwise inexplicable crankshaft failures in large slow speed marine engines. The cyclic variation of the polar moment of inertia of the reciprocating parts during each revolution causes a periodic variation of frequency and corres ponding amplitude of vibration of reciprocating engine systems. It also causes an increase in the speed range over which resonance effects are experienced and only a partial explanation of the behaviour of the systems has been worked out. It is impossible to avoid these instabilities by changes in thedesign , unless of course the variations in mass and spring constant can be made zero. In the present paper a critical appraisal of the regions of instability as determined from the equation of motion which takes into account variation of inertia is given. The motion in the form of complex waveforms is studied at different speeds of engine rotation. A comparison of theoretical results with Goldsbrough’s experimental resultsand Gregory’s analysis is included.

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.

Effect of Damping on Parametrically Excited Torsional Vibrations of Reciprocating Engines Including Gas Forces

2006 ◽  
Vol 50 (02) ◽  
pp. 147-157
Author(s):  
M. S. Pasricha
Keyword(s):  
Physical Phenomenon ◽  
Complete Response ◽  
Design Tool ◽  
Torsional Vibrations ◽  
Limited Information ◽  
Secondary Resonance ◽  
Resonance Effects ◽  
Catastrophic Failures ◽  
Marine Diesel ◽  
Engine Systems

In recent years, several cases of secondary resonance have been found in torsional vibrations of crankshaft systems. In some reciprocating large marine diesel engine systems, these effects have been a contributing factor of catastrophic failures. In these instances, design based on invariable inertia characteristics of the systems and using constant damping could not project the existence of adverse situations that led to excessively large motions. Most of the mathematical models considered thus far either give limited information on the effects of damping or restrict the analysis to an undamped variable inertia system with gas forces to avoid complexities. As a result, these models do not highlight all the consequences of such motion. This paper presents the equation of motion with key nondimensional parameters to include both damping and external excitations in order to predict the complete response of an equivalent single-cylinder engine system. Additionally, the nondimensional mathematical model presented in this paper allows development of design charts and brings the analysis closer to becoming an effective design tool. This model extends the previous analytical model by the author (2001) to include the effects of damping and gas forces acting on the system and captures many of the important concepts of time-dependent inertia systems. The complex waveform responses are examined within the range of engine speeds at which inexplicable crankshaft failures are known to have occurred. The investigations are conducted to study the interaction of secondary resonance effects with harmonic excitations for variation in damping and inertia ratios. These studies show that the observed effect is a natural physical phenomenon arising from the variable inertia characteristics of the system, and under certain circumstances it can have a serious impact on torsional vibration. The conclusions reached in this paper differ from those of Draminsky (1961) and Hesterman and Stone (1994). Comments on these differences are also included.

Transient and Unstable Torsional Vibrations on a 4-Stroke Marine Diesel Engine

2003 ◽  
Author(s):  
D. C. Lee ◽  
J. D. Yu
Keyword(s):  
Diesel Engine ◽  
Torsional Vibration ◽  
Marine Diesel Engine ◽  
Torsional Vibrations ◽  
Steady State Condition ◽  
Marine Propulsion ◽  
Friction Clutch ◽  
Marine Diesel ◽  
Noise Measurements ◽  
Unstable Vibration

Under steady state condition, unstable torsional vibration normally does not occur in shafting systems using 4stroke diesel engine due to hysteresis damping of shafting system and relative damping of standard fitted damper. However, the unstable torsional vibration occurs on marine propulsion shafting systems due to slippage of a multi-friction clutch installed between increasing gear box and shaft generator. To identify this unstable vibration and make proper counter measure, the simulation for transient torsional vibration using the Newmark method is introduced in this paper. The mechanism of this unstable vibration is verified by vibration and noise measurements of the shafting system.

Effect of Forcing Terms and General Characteristics of Torsional Vibrations of Marine Engine Systems with Variable Inertia

1974 ◽  
Vol 18 (02) ◽  
pp. 131-138
Author(s):  
W. D. Carnegie ◽  
M. S. Pasricha
Keyword(s):  
Equations Of Motion ◽  
Mean Value ◽  
Wave Form ◽  
Actual System ◽  
Computer Methods ◽  
Reciprocating Engine ◽  
Complex Wave ◽  
Wave Forms ◽  
Crankshaft Rotation ◽  
Engine Systems

The torsional vibration phenomenon in the running gear of reciprocating engine systems is usually dealt with by considering a series of constant inertias connected by sections of massless shafting. Such a simplified model does not reproduce the exact dynamic characteristics of the actual system. In recent years several cases of marine crankshaft failures have been attributed to the phenomenon of secondary resonance, which is explained by the fact that the effective inertia of each slider crankmechanism varies about a mean value in relation to the position of the crank. When the variableinertia effect is allowed for, the equations of motion taking into account the effect are nonlinear. Assuming small displacements, the equations can be linearized to predict important characteristics of the motion. The motions in the form of complex wave forms are studied at different speeds of engine rotation and some of the wave form solutions are analyzed in the range of present investigations. Computer methods making use of numerical analysis processes, namely, the modifiedEuler's equations and the Runge-Kutta constants, have been applied in the investigations. A study of the effect on the motion of the system due to variation of inertia ratio is carried out at a particular speed of the crankshaft rotation; also investigated are the variations in the motions due to the action of external excitations with respect to changes in phase angle and inertia ratio. General comments on Draminsky's work in the light of the present investigations are included.

Influence of the Instantaneous Angular Speed (IAS) of Marine Diesel Engine on its Indication Results

2015 ◽  
Vol 236 ◽  
pp. 204-211
Author(s):  
Marek Łutowicz ◽  
Dominika Cuper-Przybylska
Keyword(s):  
Time Domain ◽  
Ad Hoc ◽  
Angular Speed ◽  
Time Axis ◽  
Crank Angle ◽  
Instantaneous Angular Speed ◽  
Marine Diesel ◽  
Angle Rotation ◽  
Crankshaft Rotation ◽  
Opening And Closing

The paper presents a method of transforming the time axis to the axis of the crank angle rotation based on the pressure measured in time domain and simplified model of the engine dynamics. Indicating is to register the pressure in synchronism with the engine crank angle rotation. Usually in the ad hoc measurements the crankshaft rotation angle transducer is avoided, and the measurements are performed in time domain. For further analysis time axis is transformed for crank angle axis on the base of linear transform. Pressure waveforms obtained during the research were subject of the described transform. During the research instantaneous angular speed (IAS) of the engine crankshaft has been changed by reducing fuel dosage to selected cylinders. Mean indicated pressure (MIP) was calculated. Values o pressure on the begging and the end of compression, opening and closing angles of valves were also determined.

Nonlinear Aspects of the Performance of Centrifugal Pendulum Vibration Absorbers

1964 ◽  
Vol 86 (3) ◽  
pp. 257-263 ◽  
Author(s):  
D. E. Newland
Keyword(s):  
Torsional Vibration ◽  
Large Amplitude ◽  
Vibration Absorbers ◽  
Aircraft Engines ◽  
Reciprocating Engines ◽  
Centrifugal Pendulum Vibration Absorbers ◽  
Large Amplitude Motion

Centrifugal pendulums have been used for many years to limit the torsional vibration of reciprocating engines. Recently small pendulums, designed to swing through amplitudes of about 45 deg, have been tested for lightweight aircraft engines. These have not functioned properly, and have been found to swing through much larger angles than expected, damaging the stops limiting motion of the pendulum counterweight. This paper investigates the large-amplitude motion of centrifugal-pendulum vibration absorbers.

Probabilistic Torsional Vibration Analysis of a Marine Diesel Engine Shafting System: The Level Crossing Problem

1989 ◽  
Vol 56 (4) ◽  
pp. 953-959 ◽  
Author(s):  
Efstratios Nikolaidis ◽  
Anastassios N. Perakis ◽  
Michael G. Parsons
Keyword(s):  
Diesel Engine ◽  
Torsional Vibration ◽  
Probabilistic Approach ◽  
Series Representation ◽  
Harmonic Series ◽  
Complex Conjugate ◽  
Time Interval ◽  
Marine Diesel Engine ◽  
Level Crossing ◽  
Marine Diesel

A probabilistic approach to the torsional vibration problem of a marine diesel engine shafting system has been developed. In this analysis, the shafting shear stress is found to be a Gaussian, harmonizable cyclostationary process with a harmonic series representation consisting of two complex conjugate components. In this paper, the level crossing problem for this stress process is studied. Two methods for estimating the probability that the stress exceeds a specified threshold at least once over a given time interval are presented. In the first method, a local maximum of the process is approximated by the value of the corresponding envelope at the time of occurrence of this maximum. A Markov-type condition is assumed to hold for the local maxima. The second method assumes that the maximum of the process over a reasonable number of cycles is approximately equal to that of the envelope process. The envelope crossings are assumed to constitute a Poisson process. The two methods are applied to estimate the upcrossing probability in various cases. The results of both approaches are found to be in good agreement with those from Monte Carlo simulation.

Interval-Valued Intuitionistic Fuzzy Topsis-Based Model for Troubleshooting Marine Diesel Engine Auxiliary System

2017 ◽  
Vol Vol 159 (A1) ◽  
Author(s):  
D O Aikhuele ◽  
F M Turan ◽  
S M Odofin ◽  
R H Ansah
Keyword(s):  
Diesel Engine ◽  
Score Function ◽  
Fuzzy Topsis ◽  
Marine Diesel Engine ◽  
Ideal Solution ◽  
Intuitionistic Fuzzy ◽  
Marine Diesel ◽  
Intuitionistic Fuzzy Topsis ◽  
Engine Systems ◽  
Interval Valued

In this paper, we present an interval-valued Intuitionistic Fuzzy TOPSIS model, which is based on an improved score function for detecting failure in a marine diesel engine auxiliary system, using groups of experts’ opinions to detect the root cause of failure in the engine system and the area most affected by failures in the diesel engine. The improved score function has been used for the computation of the separation measures from the intuitionistic fuzzy positive ideal solution (IFPIS) and intuitionistic fuzzy negative ideal solution (IFNIS) of alternatives while the criteria weight have been determined using an intuitionistic fuzzy entropy. The study is aimed at providing an alternative method for the identification and analysis of failure modes in engine systems. The results from the study show that although detection of failures in Engines is quite difficult to identify due to the dependency of the engine systems on each other, however using intuitionistic fuzzy multi-criteria decision-making method the faults/failure can easily be diagnosed.

Sign in / Sign up

Export Citation Format

Share Document