The object of research is marine diesel engine oils, which provide lubrication, cooling and separation of friction surfaces. The subject of the research is the process of ensuring minimum mechanical losses in marine diesel engines. A problematic point in ensuring the lubrication of the cylinder-piston group and motion bearings is the lack of analytical and experimental studies that establish the relationship between the structural characteristics of engine oils and mechanical losses arising in marine internal combustion engines. The degree of orientational ordering of molecules and the thickness of the boundary lubricating layer are considered as the structural characteristics of engine oils. The determination of these values was carried out using the optical method based on the anisotropy of the light absorption coefficient by the boundary lubricant layer and the isotropic volume of the liquid (engine oil). The assessment of the level of mechanical losses arising in marine diesel engines was carried out according to an indirect indicator – the overshoot of the rotational speed and the time to reach the steady state of operation in the event of a change in load. It has been experimentally established that for engine oils used in marine internal combustion engines, the thickness of the boundary layer can be 15–17.5 µm. Motor oils, which are characterized by a higher ordering of molecules and a thickness of the boundary lubricant layer, ensure the flow of transient dynamic processes with less overshoot and a shorter transient time. This ensures the level of minimal mechanical losses occurring in marine diesel engines. The technology for determining the structural characteristics of engine oils can be used for any type and grade of oil (mineral or synthetic; high or low viscosity; used in both circulating and cylinder lubrication systems). The method of indirect assessment of mechanical losses of marine diesel engines can be used for any types of internal combustion engines of ships of sea and river transport (low-, medium- and high-speed; as well as performing the functions of both main and auxiliary engines).

The paper considers processes of treatment for fuels with high sulphur content, when applied in marine medium-speed diesel engines. The paper describes features of operating marine medium-speed diesel engine fuel systems with high-viscosity fuels. The paper offers an option for the cavitation fuel treatment to disrupt the sulphur-carbon bonds in the marine fuels. The authors developed a scheme of the experimental installation, which allows performing cavitation fuel treatment. The results of the analysis are provided in the paper, as well as the fuel cavitation treatment effect on sulphur wear of diesel engine cylinder and piston assembly parts (bushing and top piston ring) is analysed, as well as its operational parameters (maximum cylinder pressure, gases temperature in the exhaust manifold).

The phenomenon of the motor oil viscosity stratification in lubricating the cylinder-piston units of marine diesel engines has been investigated. The correlations for determining the shear stress and the velocity, occurring in the liquid flow between the parallel planes, have been given. The modes of the hydrodynamic and the boundary lubrication, taking place in the cylinder assembly of the marine diesel engine operation, have been considered. The methodology has been introduced for determining the viscosity of the boundary layer, which separates the surfaces of the piston ring and that of the cylinder bushing in the marine diesel motor operation. The results of the experiments, confirming the presence of the viscosity stratification in the boundary lubrication layer of the marine motor oil, have been submitted.

Abstract:The possibility of marine slow-speed diesel engine cylinderpiston group diagnosis with view to the specification of waste oil taken from the under-piston space has been discussed. The specifics of using high-base cylinder oils in marine slow-speed diesel engines to prevent sulfur corrosion of the cylinders have been described. Typical challenges, arising in the process of using oils for lubricating the cylinder-piston group and ways to overcome such challenges have been specified. Empirical data that allowed for determining the optimum cylinder oil consumption and ensuring minimum wear diesel engine cylinder bushings have been provided. The experiments that were carried out in sea ship conditions are proved by findings of an oil analysis at a third-party onshore research laboratory.

The study objective is to identify to what extent the recirculation of exhaust gas from a low-speed marine diesel engine affects environmental, economic and power-related parameters in engine operation. Concentration of nitrogen oxides in exhaust gases was assumed to be the environmental parameter of an engine, specific fuel consumption as its economic parameter while effective (brake) power as its power-related parameter. Content of nitrogen oxides in exhaust gases discharged by low-speed marine diesel engines shall remain within the range of 3.4…14.4 g/(kW•h) depending on the area of marine vessel operation as specified by requirements of Annex VI MARPOL. Exhaust gas recirculation (EGR) was reviewed as a way to provide for such values. It was proven experimentally that recirculation of exhaust gas in the range of 4.7…18.8 % provides for reduction in concentration of nitrogen oxide (NO х) in the exhaust gases respectively down to 13.3…3.3 g NO x /(kW•h) depending on the rotation speed and load of diesel engine. Drop of NO х concentration in exhaust gases (as compared to NO х concentration without any circulation system used) was shown to reach 37.9…53.5%. It is proposed to apply the EGR system as a major technique to reduce NO х-emissions and bring the aforesaid parameter in compliance with requirements of international agencies. Sažetak Cilj studije je identificirati: "Do koje mjere ponovno strujanje ispušnoga plina iz sporohodnog dizelskog stroja, utječe na okolišne, ekonomske i energetske parametre pri radu stroja?" Koncentracija nitrogen oksida pri ispušnim plinovima, smatra se energetskim parametrom stroja, a specifična potrošnja goriva, kao ekonomski parametar, dok je učinkovita (konjska) snaga energetski parametar. Sadržaj nitrogen oksida pri ispušnim plinovima koje ispušta sporohodni brodski dizelski stroj, ostat će unutar dometa od 3.4…14.4g/(kW•h) ovisno o području djelovanja broda na moru, kako je specificirano zahtjevima Annexa MARPOL Konvencije Ponovno strujanje plina (EGR) odabrano je za dokazivanje tih vrijednosti. Eksperimentalno je dokazano da ponovno strujanje ispušnoga plina u dometu od 4.7…18.8% osigurava smanjenje koncentracije nitrogen oksida (NO x) pri ispušnim plinovima, prema redosljedu navođenja sve do 13.3…3.3 g NO x /kW•h ovisno o rotacionoj brzini i opterećenju dizelskoga stroja. Pad koncentracije pri ispušnim plinovima (u usporedbi s NO x) koncentracijom bez ikakva sustava cirkulacije dostigao je 37.9…53.5%. Predlaže se da se primijeni EGR sustav kao glavna tehnika smanjenja NO x emisija i da se dovede spomenuti parametar u skladu sa zahtjevima međunarodnih agencija. KEY WORDS low-speed marine diesel engine environmental indicators of diesel engine operation concentration of nitrogen oxides in exhaust gases exhaust gas recirculation (EGR) system brake power specific fuel oil consumption KLJUČNE RIJEČI sporohodni dizelski motor okolišni pokazatelji djelovanja dizelskoga stroja koncentracija nitrogen oksida pri ispušnim plinovima sustav ponovnoga strujanja plina konjska snaga specifič...