The predominance of marine [0]fuels with sulfur levels of ≤ 0.50 wt% has significantly reduced industry-wide concern about corrosive wear: this wear stems from the formation of sulfuric acid due to combustion of high sulfur fuel in large two-stroke marine diesel engines. However, other fundamental wear mechanisms do exist and must be properly controlled to ensure hardware durability and reliable engine operation. Liner scuffing, which can be described fundamentally as adhesive wear, continues to occur in large two-stroke marine engines regardless of fuel sulfur level. In the combustion chamber of these engines, piston rings slide against cylinder liners under conditions of high pressures and temperatures. Beyond acid neutralization and deposit control, a key function of the cylinder oil [0]is to form a durable protective film between moving surfaces that mitigate metal-to-metal contact. Multiple factors such as metallurgy, operating conditions (pressure, temperature, etc.), and lubricant impact scuffing and other types of wear. However, this article focuses on the role cylinder oils play in mitigating ring and liner wear. Engine builders determine liner wall surface finish, piston ring pack design and ring coating materials and thickness, while lubricant suppliers and additive companies develop cylinder oils to provide adequate film thickness and, in some cases, dedicated anti-wear / extreme pressure additive technology to reduce friction, minimize wear, and impart high load-carrying capability to the lubricant.

A feasibility study was conducted on examining combustion and emission characteristics of a diesel dual fuel (DDF) engine that uses gas to liquids (GTL) diesel fuel and natural gas. Natural gas can reduce carbon dioxide (CO2) emissions and shale gas is expected to be supplied more stably and inexpensively. However, natural gas engines generally employ the Otto cycle, which is ignited by a spark plug, due to their low self-ignitability. Therefore, their thermal efficiency is lower than that of diesel engines, and this makes their brake specific fuel consumption (BSFC) higher. For this reason, Diesel cycle-based DDF engines were developed in an attempt to improve BSFC levels. DDF engines ignite natural gas by self-ignition of injected gas oil. On the other hand, GTL diesel fuel is expected as a possible alternative fuel made from natural gas, thanks to its high ignitability. Therefore, it can be considered that replacing gas oil with GTL diesel fuel will lead to an improvement in combustion characteristics of DDF engines that are ignited by liquid fuel. Consequently, in this study, a test was conducted to apply GTL diesel fuel to a DDF engine. A conventional 1007-cc diesel engine was modified into a test engine by installing a gas mixer on its intake pipe in order to take in natural gas from the manifold, making it possible for the engine to suck premixed natural gas and air. This premixed gas was ignited by injected GTL after compression. The test was aimed at making clear combustion and emission characteristics of the DDF engine. In the combustion process, nitrogen oxides (NOx) emissions increased at high load. However, smoke emissions were significantly lower than the case of diesel combustion. Moreover, it was found that BSFC of the DDF engine was lower at middle and high loads compared to diesel combustion. Although total hydro carbon (THC) emissions from the DDF engine were high at low load, the use of GTL diesel fuel made it possible to reduce such emissions.

  Plastic waste is one of the biggest issues for the marine environment as it riddles our oceans and it will take more than 450 years for it to biodegrade even if it ever does so. When considering the protection of the marine environment, another big issue is greenhouse gas (GHG) emissions from ships, as pointed out by the Initial IMO GHG Strategy for the shipping sector.

  Considering the need to address these issues, we have carried out combustion tests of Waste Plastic Oil (WPO), Biofuel and mixtures of these two fuels, by using a small-bore one-cylinder four stroke diesel engine. WPO has low viscosity and a low flash point, and Biofuel has high viscosity and a high flash point. We have tested several types by combining the two fuels to analyze their combustion performance and identified an optimal mixture of the two fuels for the small-bore diesel engine. The results found that blending Biofuel with WPO led to proper viscosity for diesel combustion, and that mixing up to around 50% of Biofuel produced positive results for the combustion of the diesel engine regarding NOx and smoke emissions, without jeopardizing many other parameters like CO and thermal efficiency. Since the flash point of WPO is lower than 60 °C, it is necessary to pay sufficient attention to the safe handling of mixed oils containing WPO.

  Sulfur oxide (SOx) affects environment, for example, in the form of acid rain. Marine SOx scrubbers are used to remove SOx in exhaust gas from ships when using fuels with high sulfur content. The SOx scrubbers require a relatively large space for installation and are difficult to apply to small vessels. In this study, we developed a simplified model applicable to calculating changes in SO₂ concentrations in SOx scrubbers with the aim of developing smaller SOx scrubbers. Our model is based on the steady state one-dimensional equations in the flow direction. In order to simplify the complex physics, the model assumed a uniform flow for exhaust gas and spray droplets absorbing SO₂. The performance of desulphurization of the prototype small scrubber was evaluated by comparing the results of desulfurization experiments using actual engine exhaust gases with those of model calculations. As a result, it was shown that the developed scrubber can achieve sufficiently high desulphurization performance to meet regulations.

  Electrostatic precipitator is one of the technologies to reduce PM emissions from marine diesel engines. However, when electrostatic precipitators are applied to the exhaust gas treatment of diesel engines, their discharge characteristics have not been clarified. In this study, the effects of ambient gas conditions on the discharge characteristics of electrostatic precipitators have been investigated to develop an electrostatic-cyclone type precipitator. A high-pressure chamber with a discharge electrode and a collection plate placed inside was manufactured and used in the experiment. The ambient temperature and pressure could be adjusted within the range of room temperature and 300 deg C and the range of 0.1 and 0.5 MPa (abs.), respectively. The experimental results show that the discharge current of the saw-type electrode used here changes depending on the atmospheric temperature and pressure and is basically determined by the gas density of the atmosphere. Furthermore, the discharge characteristics in the exhaust gas of a 2-Stroke marine diesel engine was examined. The results show that the discharge characteristics in the exhaust gas are different from those in the atmosphere.