Possibilities of using the free-end of crankshaft in diagnosis of slow speed marine diesel engines (original) (raw)
Related papers
Design and Numerical evaluation of crankshaft of diesel engine for total deformation and strain
IOP Conf. Series: Materials Science and Engineering , 2020
The crankshaft is an engine component that converts the linear (reciprocating) motion of the piston into rotary motion. Features of a crankshaft include the crankpin journal, throw, bearing journals, counterweights, crank gear, and a power takeoff (PTO). Crankshafts are machined through a sequence of automated operations that remove material using lathes and milling machines. Other off-the line processes include inspection, test and repair. High-count cylinder engines involve higher inertias, overlapping combustion events and torsional vibrations of the flexible crankshaft which strongly complicate the diagnostics. The equivalent inertias and stiffness's of the system were calculated from drawings, modelling of the crankshaft with a CAD (computer-aided design) software and finite element method. Crankshaft is Internal cylinder pressure (or torque) estimation is an important engine parameter with significant implications for diagnostic and control applications in internal combustion (IC) engines. Many speed-based diagnostics methods employ models of the engine dynamics. In a dynamic model of a small four-cylinder diesel engine with the assumption of a rigid crankshaft is employed to estimate individual cylinder power production.
A review on vibration analysis of crankshaft of internal combustion engine
2015
Crankshaft is mechanical component with a complex geometry which transforms reciprocating motion into rotational motion. The conversion of reciprocatory motion of the crank to rotational motion in an IC engine is done by the crankshaft. Crankshaft plays a pivotal role in its functioning. The stress and fatigue that the crankshaft can handle decides the satisfactory working period of crankshaft. Any defect in the crankshaft deteriorates the performance of the engine. Faults in crankshafts can result in degradation of the engine and lead to losses in terms of revenue. Hence, it is important to analyze the crankshaft and predict its failures before a severe catastrophe occurs. Vibrations give a good amount of information on the characteristics of the vibrating structures and hence vibration analysis can be used to inspect and evaluate the crankshaft. In this paper, a brief review of analyzing crankshaft by means of vibration analysis which forms an integral part in almost all the field...
The torsional vibrations of marine Diesel engines under fault operation of its cylinders
Forschung Im Ingenieurwesen-engineering Research, 1992
The torsional vibrations calculation of Diesel engines is usually performed for different speeds of revolutions but for uniform operation and behaviour of each cylinder. This condition is true only for new of very well maintained engines but generally the different cylinders operate with considerable deviations from its design conditions. This situation may influence strongly the torsional vibrations of the system, since the spectrum of the exciting forces is dfferent. In some cases this non uniform operation of the different cylinders may induce severe torsional stresses leading to serious vibrations or even to damage. This contribution presents same theoretical and experimental results obtained on this subject taking into account usual engines conditions showing wrong injection timing, not proper operation of the turbocharging device, incorrect valve timing, excessive wear of piston rings and~or piston liners etc. All these faults result in an exciting force spectrum that is different in frequency and~or phase from the corresponding of uniform normal operation of each cylinder. This deviating spectrum can be predicted and practical measured by the thermodynamic behaviour and the indicators diagrams of the engine and the corresponding stresses can be calculated accordingly. The torsional stresses on the intermediated shaft can measured using strain gauges method and the bridge voltage output converting to numerical file stored on a miniature computer which running with the shaft. The method reported here has been verified for two identical ship engines MIRRLEES JVSS12 having different faults. The corresponding results after both engines has been tuned properly are reported too to show the influence of the improper maintenance.
Computer Aided Design and Analysis of Crankshaft for Diesel Engine
TJPRC, 2013
Crankshaft is one of the critical components for the effective and precise working of the internal combustion engine. In this paper a dynamic simulation is conducted on a crankshaft from a single cylinder 4- stroke diesel engine. A three-dimension model of diesel engine crankshaft is modeled using UNIGRAPHICS software. Finite element analysis (FEA) is performed to obtain the variation of stress magnitude at critical locations of crankshaft. Simulation inputs are taken from the engine specification chart. The dynamic analysis is done using FEA Software ANSYS which resulted in the load spectrum applied to crank pin bearing. This load is applied to the FE model in ANSYS, and boundary conditions are applied according to the engine mounting conditions. The analysis was done for different engine speeds and as a result critical engine speed and critical region on the crankshaft were obtained. Stress variation over the engine cycle and the effect of torsional load in the analysis were investigated.
A new approach for determining the torsional stiffness coefficient of an equivalent mechanical system's crankshaft section, which can be used to study torsional vibrations, is presented. In order to describe mathematically the torsional vibration of a reciprocating engine, it is necessary to replace the actual system consisting of the crankshaft, connection rods, and reciprocating elements by an equivalent system, usually modelled as a lumpedparameter system. The present authors, in accordance with their personal experiences, have found the determination of the equivalent system's parameters to be a very important and demanding task, especially in regard to torsional stiffness and damping coefficients. This paper analyses all aspects of determining a crankshaft section's torsional stiffness coefficient, which is the most complex element in a torsional dynamic model of a crankshaft. The method analysing the crank torsional stiffness coefficient determination has been given in the literature. The real boundary conditions of the crankshaft are emphasized as a problem, which makes determination of the torsional stiffness coefficient of the crankshaft section even more difficult. An indirect method for this determination is explained in this paper. By using this method, the real boundary conditions of the crankshaft of the diesel engine used in heavy-duty vehicles are considered, and the results obtained are reliable and confirmed by experiment.
Transactions of FAMENA
In a four cylinder four stroke diesel engine, the crankshaft angular velocity fluctuation during the steady state operation is the result of the cylinder pressure variation, the engine friction and the dynamics of the crankshaft. The mentioned dependency of the parameters is used to create the equivalent lumped mass model to correctly represent its dynamics. Based on this model, the relationship between the engine torque variation and the crankshaft angular velocity fluctuation for steady state operation is presented in this paper. Analyzing only the lower harmonic orders of the angular velocity possible distortions in the engine operation can be identified. The information obtained by the harmonic analysis permits to establish the correlations between the measurements and the average gas pressure torque of the engine, and to detect the malfunctions and identify faulty cylinders. In the paper, a methodology has been developed for the determination of the gas pressure in a cylinder o...
Failure mode analysis of a diesel motor crankshaft
Engineering Failure Analysis, 2017
A failure mode analysis of a diesel motor (110 kW) crankshaft from an automobile vehicle is presented. After 120,000 km in service, an abnormal vibration was detected which was increasing with the time. The diesel motor was disassembled first for determining the root cause, however without success. No defect was detected, but since a suspicion of damage was present, and being this failure recurrent in this type of diesel motor series, the crankshaft was disassembled again. Then the crankshaft was subjected to a simple vibration analysis and a preliminary indication of possible existence of a crack was concluded. The crankshaft was then replaced by a new one, and the old was subjected to a failure analysis for determining the root cause. A crack was found at the crankpin web-fillet and after a complete opening of the crack, the failure analysis showed that fatigue was the dominant failure mechanism. Observations were carried out by optical and Scanning Electronic Microscope. Material defects at the crack initiation zone were not found. The root cause of damage seems to be a misalignment of the main journals and a weakness of design close to the gear at the region where the crack was initiated. Therefore, probably a poor design and a deficient assembling of the crankshaft helical gear coupled to the main journal end was the first cause of the failure.
On the assessment of fatigue life of marine diesel engine crankshafts
The fatigue strength and its correct assessment play an important role in design and maintenance of marine crankshafts to obtain operational safety and reliability. Crankshafts are under alternating bending on crankpins and rotating bending combined with torsion on main journals, which mostly are responsible for fatigue failure. The commercial management success substantially depends on the main engine in service and of its design crankshaft, in particular. The crankshaft design strictly follows the rules of classification societies. The present study provides an overview on the assessment of fatigue life of marine engine crankshafts and its maintenance taking into account the design improving in the last decades, considering that accurate estimation of fatigue life is very important to ensure safety of components and its reliability. An example of a semi-built crankshaft failure is also presented and the probable root case of damage, and at the end some final remarks are presented.
Polish Maritime Research, 2010
Periodically changeable gas and inertia forces which occur during operation of engine generate transverse, axial and torsional vibrations of crankshafts of multi-cylinder combustion engines. Torsional vibrations are those which endanger crankshafts of multicylinder combustion engines the most. In order to minimize their impact a torsional vibration damper is installed at crankshaft's free end. Its technical state directly influences lifetime and reliability of engine. In this paper methods of diagnosing, maintenance and regeneration of torsional vibration dampers used in shipbuilding, are discussed. Also, are presented results of multi-year statistical investigations carried out in cooperation with a firm maintaining and regenerating ship engine torsional vibration dampers, which illustrate types of failures occurring in viscous and spring torsional vibration dampers.
Instantaneous crankshaft torsional deformation during turbocharged diesel engine operation
2010
An experimentally validated diesel engine code is used to study the crankshaft torsional deformations originating in the difference between instantaneous engine and load torques. The analysis aims in studying the phenomena under critical conditions, namely operation when one cylinder malfunctions ('open valves' or motoring situation) as well as during transient conditions. A detailed crankshaft torsional model is formulated; this takes into account cylinder gas, inertia, friction, load and stiffness and damping torques. Details are provided concerning the underlying mechanism of the crankshaft torsional deformations, which can assume significant values depending on the specific configuration, being important for safe engine operation.