Abstract
Increasing the energy efficiency of the marine propulsion systems currently represents one of the priorities that have been placed in front of all subjects of maritime shipping market. More and more ship owners aspired to larger and more powerful diesel engines demanded from the marine engine manufacturers to implement various technological modifications to increase the engine efficiency, extend the life of engine components, and thus prolonge regular overhauling period of them. One of the way to meet these demands, among other things, is to improve the tribological characteristics of engine components. The aim of this paper is to present structural modification of tribological system “cylinder liner - piston ring - piston” of large bore slow speed marine diesel engine to reduce friction problems in mentioned system.
Highlights
The current trend in development of shipping and technology in general has outcome in improving the efficiency of the large two-stroke low-speed marine diesel engines with cylinder unit modifications. Those modifications have resulted in improvement of tribological properties of tribosystem “cylinder liner - piston ring - piston”
The targets of structural modifications are (Wärtsilä Sulzer, 2009): - To give the customer the best standard to achieve an extended TBO (Time Between Overhauling) up to three years for hot parts. - To allow the customer to reduce the cylinder oil feed rate to values of approximate 1.2 g/kWh with no risk of excessive wear. - To reduce the wear rate for the cylinder liner to 0.05 mm/1000 working hours or less over a wide load range of the engine. - To reduce the risk of failing during running-in period as well as sea trial and generally to reduce the running-in time to 10 hours and less
Blue line shows the temperature of cylinder liner of RTA84T engine with tribological insulation in the TDC (Top Dead Centre) area and in the middle of the stroke, indicating that the operating temperature of the cylinder liner deviates significantly from the dew point temperature, which leads to specific wear in diameter under 0.05 mm/1000 working hours
Summary
The current trend in development of shipping and technology in general has outcome in improving the efficiency of the large two-stroke low-speed marine diesel engines with cylinder unit modifications. Those modifications have resulted in improvement of tribological properties of tribosystem “cylinder liner - piston ring - piston”. This paper clearly shows all the modifications that are today’s standard in the construction of large two-stroke low-speed marine diesel engines. The targets of structural modifications are (Wärtsilä Sulzer, 2009): - To give the customer the best standard to achieve an extended TBO (Time Between Overhauling) up to three years for hot parts.
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