Novel marine diesel particulate filter (DPF) which traps particulate matter (PM) exhausted from a marine diesel engine on the surface of a nonwoven fabric metallic filter has been developed. PM trapping characteristics in relation to the PM reduction ratio and pressure loss in the DPF unit have been investigated through experiments on a running diesel engine. Trapped PM was eliminated by high frequency induction heating, effectively regenerating the DPF. The experimental results which show the mutual relation between the pressure losses and PM reduction ratio in the DPF were investigated and estimated on the basis of the DPF unit’s construction.

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 Biofuel has lately attracted considerable attention as an effective renewable energy and as a countermeasure against global warming. This paper presents results of improvement of combustion in a 4 stroke cycle medium speed marine diesel engine using marine diesel oil (MDO), marine fuel oil (MFO) and biofuels without esterification such as rapeseed oil and used vegetable oil. The authors systematically investigated the effect of biofuel content of fuel oil, the effect of fuel injection timing, and the effect of assist injection system which is a new fuel injection system composed of a common rail system and a cam drive pump. The findings are the following: (1) In high engine load conditions, it is possible to reduce CO, PM and smoke by mixing used vegetable oil with MFO because the combustion of biofuel achieves low CO, PM, and smoke emissions in these conditions. (2) In low engine load conditions, the combustion of biofuel results in higher CO and smoke emissions, but it is possible to reduce CO and smoke significantly by using assist injection system (a small amount of low pressure pre-injection).

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 In this research, used vegetable oil without esterification was used in a medium speed marine diesel engine as an alternative fuel. The effects of fuel properties, such as kinematic viscosity, evaporation characteristics, ignition delay, and fuel injection control, such as fuel injection pressure and fuel injection pattern (pre-injection and after-injection) on the combustion characteristics and the exhaust emissions were investigated using a test bench. Results show that: the evaporation characteristics and ignition delay of the fuel have much effect on combustion characteristics and the exhaust emissions, but kinematic viscosity has hardly any effect; the fuel injection control such as pre-injection with little injection quantity is effective in reducing smoke, CO, unburned HC and PM at low load operation.

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 In lubricated surfaces of reciprocating engine components, such as piston rings and cylinder liners in marine diesel engines, the effects of surface texturing on lubrication characteristics are considered to be important. In addition, measurement of the electrical contact resistance between the lubricated surfaces of reciprocating components is thought to be effective for lubrication condition monitoring, particularly the existence or absence of oil film. In this study, well-regulated “micro dimples” and “micro grooves” were formed on a flat surface using the method of micro fabrication. A bearing steel (HV760) was used for the specimens with ball-on flat configuration. The friction force, relative movement, and electrical contact resistance between the specimens were measured simultaneously during reciprocation at a stroke of 1 mm under lubricated conditions of 70 and 460 mm²/s oil (non additive mineral oil). The normal load and frequency were varied in the range of 4.9 to 19.6 N, 1 to 5 Hz respectively with comparisons made between specimens with flat surfaces. Furthermore, a direct observation of the contacting surfaces was carried out with a hemispherical sapphire glass using a high speed digital camera. Using these results, the effects of surface texturing of reciprocating component surfaces on the lubrication conditions are discussed.

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 Cast iron is used as material for motor and pump casings due to its superior casting characteristics. In addition, it is used for cylinder liners and pistons exposed to high temperatures because its strength does not deteriorate even at high temperature conditions. For parts made of cast iron, examples of brittle fracture damage induced by thermal stress are reported. However, there are a few failure examples where cracks lead to fracture. Therefore, a study was conducted to clarify the transition process of stationary crack to brittle dynamic fracture induced by thermal stress. All processes of fracture phenomena were recorded by an ultra-highspeed video camera. The position of the crack tip was determined from image data, and the propagation velocity of the crack was surmised. Then, the authors measured the surface roughness of the fracture process zone caused by crack propagation. Furthermore, the stress intensity factor which is a condition for a crack to propagate was obtained by calculation using the load data value of the specimen.

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 The purpose of this study is to improve the wear resistant properties of DLC film coated on Cr-Mo steel used in seawater. DLC films are often used in sliding systems of machinery, but they are easily fractured and detached because of corrosion of the foundation material when these are used in corrosive environments such as in seawater. In this paper, a cathode rust prevention technique is attempted to prevent corrosion of the steel foundation using Zn material which is coated on the edge of the steel foundation. The wear tests show that DLC films coated on the Zn processed steel foundation possess good anti-wear performance in artificial seawater. Based on these tests and surface observations using several microscopes, the experimental results are discussed.

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