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Tribology Design for Components of HiMSEN Engine

Marine diesel engine is composed of many interacting components. In this study, technologies to improve tribological performance of components for HiMSEN engine are explained. Cam-roller system is used as a device for driving the valve train in HiMSEN engine. Real contact stress as well as Hertz stress is very important design parameter of cam and roller. Local contact stress concentration often cause scratches or contact fatigue damage such as fitting on surface of roller and cam. In order to obtain even contact stress distribution, logarithmic roller profile was applied. Three factors which determine the profile were optimized using micro contact analysis and RSM(Response Surface Method). Optimized profile induced 10% lower contact pressure than the previous profile. Hydrodynamic journal bearings are widely used in machinery to support a rotating shaft. In case of connecting rod bearing, lubricating oil is supplied through the rotating crank pin and high load by firing pressure acts on connecting rod body. So fluctuating oil pressure and elastic deformation of connected components should be considered to evaluate the lubrication performance of journal bearing. Elasto-hydrodynamic(EHD) lubrication analysis considering oil supply pressure variation in a cycle was carried out. Based on the analysis results, the optimum oil supply hole size and clearance of bearing were determined. Idle gear serves to transmit torque for the driving valvetrain form crankshaft to camshaft and consists of gear, shaft and shrink-fitted journal bearing. Idle gear shaft is assembled on front end block by bolts in the latest HiMSEN engine. To make sure of robust idle gear system, convergence technology that is a coming together of vibration analysis, structural analysis and lubrication analysis is applied. Through the natural frequency analysis design for idle gear shaft and supporting part of the engine block were determined. Stress analysis and fatigue analysis were carried out to design the shape of idle gear shaft having enough fatigue safety factor. Based on the EHD lubrication analysis results, idle gear bush design was optimized.
发表在 :
作 者 :Sangdon Lee
发表日期:2016-06-10

Testing SCR in high sulphur application

论文已在中国上海举行的第27届CIMAC大会上发表。论文的版权归CIMAC所有。 NOx and SOx emissions from ship exhausts are limited by IMO ship pollution rules. NO.emission limits are set for diesel engines depending on the engine maximum operating speed. Limits are set globally(Tier I and Tier ll) and in addition for emission control areas(Tier ll). Tier ll standard is dated to 2016 and is expected to require the use of emission control technologies. SCR(selective catalytic reduction) is an available technology capable of meeting this requirement. This technology uses a catalyst and ammonia for the reduction of NOx to elemental nitrogen. On the other hand SOx limits are requiring the use oflower sulphur level fuels or aftetreatment systems, like scrubbers, to decrease SO, emissions. Scrubbers might become popular as they allow the use of inexpensive heavy fuel oil. The sulphur is usually considered as poison to catalysts. In SCR's a V2Os catalyst has been widely employed due to its high activity and sulphur tolerance. Even so, sulphur related challenges do occur. At high temperatures the SO3 can result to an unwanted visible plume while at low temperatures the SO2 can react with the ammonia to form ammonium sulphates which deposit on and foul the catalyst. This brings certain requirements to the SCR optimization in high sulphur applications. Ships utilize large engines which require large catalyst volumes todeal with the emissions. Installations to large engineapplications can be difficult and testing rather complex. Only minor(or none) tuning of the parameters is possible in real applications. In this study,a slip-stream emission control test bench is utilized to test smaller SCR units with a proper exhaust gas from a medium speed diesel engine. The test bench has an advantage of easily tuned and controlled parameters(like temperature and exhaust flow).A heavy fuel oil with a sulphur content of 2.5% is utilized as test fuel.Two different SCR catalysts with a volume of 40dm3are tested using engine loads of 100%,75% and 50%.In addition, different exhaust gas flow rates and temperatures, adjusted by the test bench, are utilized in testing. The test bench utilizes NOx sensors placedupstream anddownstream of the test SCR reactor. In addition, the standard analyser to measure the NOx (chemiluminescence) was in use. FTIR was used to measure the NH3. Hydrocarbons, carbon monoxide and carbon dioxide were measure as well. The effect of SCR on particle emissions was studied by collecting particles on filters both before and after the catalyst. The particle filters were further analysed for sulphates and organic and elemental carbon. The results for both test catalysts show NO, conversions of near 80% at 100% load and even 95% at 75% load.The HC and PM emissions were also found to reduce over both catalysts. The organic carbon fraction of PMwas reduced by the catalyst as well as the sulphates.While the organic carbon reduction can be explained by the oxidation over the catalyst the sulphates are believed to store in the catalyst. Overall the two catalysts showed nearly the same observations except in the case of a lower exhaust flow(i.e. lower space velocity)were the behaviours differed.
发表在 :CIMAC Congress 2013, Shanghai
作 者 :Kati Lehtoranta,Raimo Turunen
发表日期:2013-06-01

Development of New Lubricating Oil for Use in Modern High Efficiency Gas Engines

近年来,天然气作为一种能源被广泛应用,预计将进一步增加。这些应用主要体现在移动式和热电联供的固定往复式天然气发动机上。由于这些发动机长期高负荷工作,润滑油承受高应力,致使润滑油的配方面临挑战。 随着发动机效率和功率逐步增加、排放不断降低,发动机厂商针对发动机做出持续改进设计和操作优化。比如为了增加平均有效压力,活塞需要优化设计,金属材料需要改进设计,配缸间隙及公差范围需要减小,这些都导致润滑油面临挑战。从某种程度而言,应用于老发动机的润滑油将不适用于现代发动机,这就迫切需要开发新润滑油以满足这一需求。 未经优化的老发动机润滑油应用于现代发动机将导致润滑油使用寿命下降,发动机润滑保护功能失效,导致发动机大修期缩短并引发潜在故障,使发动机不能实现预期的效率提升。 本文将介绍现代高效气体发动机新型润滑油的开发过程,包含为提高润滑油使用寿命,采取提高抗氧化性能和碱值保持能力的手段,同时酸值仍在控制范围内。现在发动机针对积炭开展的大量研究表明,添加剂正确、合理的使用可以有效控制积炭,避免积炭大量堆积。对于润滑油配方工程师来说,采取有效的工具来评估试验结果是非常关键的。大量的性能试验数据不仅年代久远,不能代表现代发动机,而且来源于其他技术领域,并非专门针对气体发动机。本文将考虑通用试验的有效性,探索本领域范围内有代表性的评价方法,使配方工程师可以在化学领域范围内高效评估优选方案,并应用于现场试验验证。
发表在 :CIMAC 2019
作 者 :Jonathan Hughes
发表日期:2019-06-14

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