Fuel economy is a critical issue in marine shipping from the standpoint of both reducing greenhouse gas emissions and cutting fuel costs. The authors pursued the lubricants could improve the fuel efficiency of marine engines such as low-speed 2-stroke crosshead engines. The authors studied the effects of a lubricant’s viscosity characteristics and additives (e.g. viscosity index improvers and friction modifiers) on its fuel-saving performance. The authors also looked at how to maximize fuel-saving performance without sacrificing reliability, which is so crucial for marine engines. Engine testing with a fuel-efficient 2-stroke marine engine oil showed that fuel efficiency improved by 1.2% when using a fuel-efficient cylinder oil.

The gradual tightening of regulations on greenhouse gas (GHG) emissions by the International Maritime Organization (IMO) and the steep rise in the price of fuel oil have led to a strong demand for energy saving in ships. As a result, ships have become larger in size, have been reduced service speeds, have been equipped low speed main engines, have been equipped with energy-saving devices, etc., and corresponding propellers have become necessary. This section describes recent technological trends in propellers.

Recent progress of air lubrication technology for reducing frictional resistance of marine vessels is introduced, including its physical mechanisms having been explored in the last two decades. The technology is classified into air filming on the wetted surface and suppression of turbulence using small bubbles injected into the turbulent boundary layer. The former approach needs stabilization of the gas-liquid free surface characterized by Froude number. The latter asks how turbulent shear stress is modified by various sized bubbles. Both approaches have recently advanced and implemented to large commercial ships, which are expected further to be improved toward low CO2 emission policy in world shipping industry.

This paper outlines the design technique of hull form. First, this paper discusses two conventional ideas and problems on hull form design. Next, the state-of-the-art research situations are overviewed by dividing hull form design technology into two categories of “hull form and performance database” and “hull form design technique based on simulation”. After that, this paper mentions the latest research of hull form optimization, and hull form expression method and deformation technique as a basis of database construction, Finally, it summarizes the latest research activities on the application of machine learning technology to hull form design.

Global warming has become one of the important social problems. The main cause for the global warming is carbon dioxide, CO₂ generated when fossil fuels such as oil and natural gas are burned. Thereby recently the momentum for reducing CO₂ emissions in maritime industry has been growing globally. International Maritime Organization, IMO, agreed a GHG reduction target in 2018. A long-term goal is to achieve zero GHG emissions from ships as early as possible in this century. In order to realize a zero GHG emission ship, it is needed to use zero-carbon fuel such as hydrogen and ammonia. In this paper, the author shows various alternative fuels and the technologies for the utilization, and discusses the technical issues for realizing the zero-emission ship.

Trains often operate as a shuttle service. When a train arrives at the terminal station, its direction of travel is reversed, and therefore so is the rolling direction of the wheels. It is therefore important to investigate how the crack propagation, and wear on the wheel tread are changed by reversing the rolling direction. In this study, twin disc wear-fatigue tests were carried out under various conditions to study the effect on the behaviour of rolling contact fatigue (RCF) cracks and wear. Also, finite element analyses (FEA) were performed in order to clarify the results of these tests. In the lubricated condition, the cumulative wear tended to increase when the rolling direction of the wheel specimen was reversed if the slip ratio was 1%. On the other hand, in the dry condition, there was almost no change in the wear before and after reversing. FEA suggested that, when the wheel specimen was reversed, lubricant was trapped in the RCF crack and the friction coefficient between the crack faces was reduced, leading to shear mode crack growth and increased the fatigue wear.

Contact Lens (CL) is used as a medical device correcting eyesight. However, it causes discomfort and eye damage by increasing friction on the upper eyelids. Therefore, to improve the safety and wearing comfort of CL, it is important to understand the friction mechanism between a CL and an upper eyelid. Although the hydration layer on a CL is understood as a key factor to reduce friction, a detailed study on the hydration layer has not been done due to the difficulty in detecting such weak structure. Frequency-modulation atomic force microscope (FM-AFM) is attracting attention as an experimental method for directly observing hydration/solvation structure at a solid-liquid interface with high resolution. In this study, we investigated the relationship between hydration structure of CL surface in physiological saline and frictional property using FM-AFM and nanotribometer. According to the friction test results, the friction coefficient increased as the number of slides increased. FM-AFM measurement confirmed the existence of a hydration layer on the CL surface. The thickness of this hydration layer decreased after the friction test. Moreover, the decreased hydration layer recovered by immersing in physiological saline, and friction coefficient of the recovered hydration layer was identical to that before the friction test.

In the oil refinery and petrochemical industry, a containment seal (CS) can be applied to a flashing hydrocarbon pump as a sealing device to prevent environmental pollution. It is extremely difficult to design a CS to ensure the contradictory functions of fluid-tight sealing and sealing surface wear resistance, which are required in both conditions of dry-running in gas and wet-running in liquid. In this study, a new CS design concept “CSAM” (Containment Seal by Additive Manufacturing) for the sealing surface and internal structure of a sealing ring was developed utilizing additive manufacturing. Basically, a lubrication film formed on sealing surfaces of mechanical seals is maintained by opening force (OF) with fluid pressure and closing force (CF) with fluid pressure and spring load. In order to obtain a desired OF, CSAM controls pressure distribution across the sealing surfaces by introducing outside pressure through slots on the sealing surfaces, and an annular cavity is formed within the sealing ring. Based on a series of numerical analyses and static tests, it has been found that the difference between OF and CF can be properly controlled with slot design parameters. The result suggests a possibility of achieving the contradictory functions of sealing and wear resistance in both gas and liquid conditions required of CSs.