Changes on the horizon for marine engine technology
Although the two-stroke, large bore diesel engine is generally regarded as the most economical, reliable and durable motor for the marine transport fleet, there remains plenty of room for improvement. This is especially the case when it comes to the maintenance and reliability of certain components, such as the exhaust system, cylinder cover, piston top, rods and bearings. One practical and cost-effective approach to improving the performance of these parts is to spray them with advanced functional coatings, and that is exactly what the EU-funded ‘Development of new thermal spraying equipment and technology for production of components for marine transport engines’ (Ofiengine) project set out to do. Ofiengine focused on a number of critical components, namely valve spindles, piston crowns and cylinder covers. In recent years, the rapid development of new materials has led to the emergence of promising new coating systems. In addition to the coating materials themselves, selection of the optimal spraying method is essential to ensure the greatest level of durability for the components in question. After conducting a comprehensive screening test for the processing of carbide-based materials to meet industrial requirements, Ofiengine developed and validated a new OFI gun prototype with the ability to deposit high-quality cermet-type coating. In addition, the main controller, chiller unit, gas lines and powder feeder were (re)designed for the new system. After further optimisation, the prototype gun was manufactured and validated. Three different demonstrators were produced and coated: a piston crown, a piston pin and a valve spindle. Of these, only one was of sufficient quality to send to the end user. Ofiengine also included four modelling components, each related to one of the sub-processes of the system: plasma formation, combustion, expansion of the flame in the barrel and in the ambient air. The system’s control software was developed to be user friendly and allows different levels of access, as well as the specification of various set points and parameters. The gun’s design is so flexible that it should be adaptable for use with other coating materials.
