CIMAC Congress - Schiff & Hafen

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<strong>CIMAC</strong> CONGRESS | BERGEN 2010 due to evolving interest in occupational health and safety issues and tightening legislations. Wärtsilä product development organization, in close co-operation with their partners and contractors, has answered the challenge and expectations. Low noise solutions suitable for the existing and future engines have been designed. This paper describes diesel engine noise control measures applied to Wärtsilä 4-stroke diesel engines. In the past five years, an increasing effort has been concentrated on noise and vibration related work in Wärtsilä R&D. The ultimate aim is to reduce noise radiation of medium speed 4-stroke diesel engines. This persistent hard work has resulted in knowledge of the major engine noise sources, in a deeper understanding of the structureborne noise transmission through the engine block and finally, in a definition of effective noise control measures. The measures are the heart of the newly developed noise reduction package. The package includes various enclosure and lagging solutions and cover structures. The solutions are based on add-on methods and structural component design improvements. Tonal noise from turbocharger is reduced by means of sound and heat insulation enclosures and laggings. Noise radiated from the side of the engine is effectively reduced by improved structural design of the covers. The flywheel end and the top part of the engine are enclosed in order to reduce the noise emitted from the subsurface. The beauty of the developed measures is that they can be adapted to any Wärtsilä 4-stroke diesel engine, existing or yet to come, large and even larger ones. Noise control measures, as a package, enables even 5 dB(A) engine noise reduction, depending slightly on engine configuration. Furthermore, the noise control package can be combined with engine room acoustic design to achieve even greater noise reduction. Two node torsional vibration control of the multi-cylinder two-stroke diesel engine S. J. Hwang, K.T. Yoo, STX Heavy Industries, Korea, U. K. Kim, Korea Maritime University, Korea Marine engines have been required higher power to fit the bigger and faster ships aiming at economical operation. To produce higher power, cylinder bore has been larger and the number of the cylinder has been increased. On the other hand, it has been continuously tried to develop components which has influence on engine power, as turbocharger, and to introduce a new fuel injection method etc. For this reason, the shafting system of the large scale diesel engine is getting complicated such that it is impossible to control the vibration in a simple way as before. By increasing the number of cylinders, the torsional vibration encounters another problem, 2-node torsional vibration in a crankshaft at the engine above seven cylinders [1]. As a solution of the problem caused by 2-node torsional vibration, a vibration damper [2] has been usually applied. However, in the future, the vibration damper might not be able to solve the problem by only itself because the power of the engine will be much higher than now. If the engine has a higher power than present engine, the size of the damper could be bigger to have higher damping coefficient [3], which affects bearings due to heavy weight and the damper’s life would be shorter by the influence of the big mass moment of inertia of the inertia ring. In this study, the methods of increasing the crank section [4] and changing the excitation characteristics which can be adopted as an alternative solution to cope with the future requirements have been investigated. The basic concepts of these methods are as follows; the first concept is to lead to increase the modulus of section of a part of the crankshaft by increasing the diameters of one crank. With the increased section modulus, the torsional stress can be reduced. The second is to have proper excitation characteristics by changing the firing order. The firing order can influence on the sub-harmonic resonance. Generally, 2-node vibration is problem with minor order. So it could be effective to change the critical order. By these concepts, the combination of the proper diameters of the crank and the firing order has been found. To select the crank of which section to be increased, the variation tendencies of the torsional stress and the node position by the variation of the crank section, flywheel and tuning wheel mass moment of inertia have been investigated. Also, since the external force, the external moment [5] and the guide force moment [6] by the change of firing order can induce high excitation of engine, it has been also confirmed. In the result of the investigation, the node location becomes more distance from the crank which the diameter is increased due to the stiffness increase by the diameter change of the crank. On the other hand, the node location approaches the wheel which the mass moment of inertia is increased. Accordingly, the node movement by the stiffness increase could be controlled by changing the wheel’s mass moment of inertia, so it could make the suggested method more effectively to control the 2-node vibration. Based on the above results, these methods have been applied at eight cylinder engine shafting system and the effects have been confirmed. Modern ultrasonic quality evaluation of large crankshafts A. Silvonen, P. Halla-aho, Wärtsilä Finland Oy, Finland, T. Hakkarainen, Inspecta Oy, Finland New developments carried out by crankshaft manufacturers in order to fulfil more strict material strength requirements set by engine builders is causing new challenges in crankshaft quality control. Higher stress amplitudes in engine operation and the fact that higher strength materials tend to have smaller allowable flaw size against metal fatigue call for more efficient nondestructive evaluation (NDE) of the crankshafts. Wärtsilä has together with its partners carried out a development work with the intention in implementing new hardware and detection guidelines to safeguard the high-level reliability of the crankshaft material. Introducing of ultra-clean steels already has a very high contribution in crankshaft safety, but in parallel with that new NDE methods are needed with improved accuracy and detection level. The most essential applied stresses in the shaft from the reliability point of view are highly concentrated in a relatively small material volume in the vicinity of the crank fillets. Finite element and fracture mechanical analyses give essential information about the critical defect sizes in function of applied stresses and location, and further, information about the needed accuracy of the used NDE system. As a result of analyses carried out it is possible to guide the ultrasonic NDE in different phases. High performance, but more time consuming techniques, will be applied in critical areas, and, conventional techniques in other parts of the shaft. Based on the required accuracy, i.e. minimum detectable imperfection size, the phased array techniques has been used in the project as a highest accuracy evaluation method. This paper reports the results of the stress and strength analyses made and material tests determining the fracture-mechanical data of modern crankshaft steels, and, finally reports benefits of the phased array NDE method over to conventional nondestructive ultrasonic methods when applied in either as forged 94 Ship & Offshore | 2010 | No. 3
Monday, 14 June Tuesday, 15 June Wednesday, 16 June Thursday, 17 June pre-machined or in finish-ground shafts, including visualization of detectable imperfections. Practical experience of NDE is also discussed including selection of probes; especially for difficult geometries, accuracy and reliability of the methods, option for automated detection, inspection data handling and relative costs. June 17th Poster Session Session 2 Exhibition area Comparison of several methods of improving the part-load performance of a medium-speed engine with a two-stage turbocharging system J. Bucher, BBB, Germany Life assessment of the camshaft in a heavy duty diesel engine using flexible multibody dynamic M. Mehrgou, Iran Heavy Diesel Engine Mfg Co. (DESA), Iran Session 3 New application and modeling of low ignitability fuel for marine engines D. Struckmeier, D. Tsurum, H. Tajima, Kyushu University, Japan Characterisation of residual fuel oil combustion properties and the appropriate selection of marine fuel additives to improve combustion M. Vermeire, Chevron, Belgium, L. Audoire, W. Ang, Infineum UK Ltd., England Syngas production from plasma stabilized diesel partial oxidation A. Nikipelov, A. Rakitin, Y. Leonov, NeqLab Research BV, Netherlands, A. Starikovskii, Drexel Plasma Institute, USA, Non vegetable origin biofuels as a combustibility improver L. Stor, A. Prada, Petrobras SA, Brazil Session 4 The use of tribology and wear metal analysis in two-stroke engines to optimize oil feed rates and reduce liner wear M. Winkler, Kittiwake GmbH, Germany Online oil condition monitoring sensors S. Lunt, Kittiwake Developments Ltd., UK The relationship between the oil analyses results and the running surface conditions of machinery – A report of marine field engineer T. Hashimoto, M. Kawabata, Y. Sasaki, Tribotex Co. Ltd., Japan Development of a new lead-free bearing material for low speed two-stroke diesel engines M. Yamada, W. Zhong, N. Kawakami, A. Ono, Daido Metal Co., Ltd., Japan Slide bearing monitoring system: Recognizing friction before noticeable mechanical damage occurs; a field report H. R. Uebel, M. Theobald, Schaller Automation GmbH Co. KG, Germany Session 5 Development of integrated vibration analysis and monitoring system for marine diesel engines and ship machineries D. Lee, K. Joo, T. Nam, Mokpo National Maritime University, Korea, E. Kim, S. Kim, Vitech, Korea Effects of inertia and gas torques on the crankshaft in determining vibration amplitudes for condition monitoring in preventive maintenance J. C. Orji, Starzs Marine, Nigeria Sound field adjustment using sound absorber in the ISO type sound insulation test facilities M.-S. Kim, STX Heavy Industries, Korea No. 3 | 2010 | Ship & Offshore 95
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