Since the beginning of 2020, the sulfur content in fuel oil has been limited to 0.5% or less in all sea areas in order to reduce the volume of sulfur oxides (SOx) and particulate matter (PM) in exhaust gas emitted from ships.
Japan Engine Corporation and Onomichi Dockyard Co., Ltd. developed the state-of-the-art engine "UEC-LSJ" that can operate exclusively on Marine Gas Oil (MGO) or Marine Diesel Oil (MDO) with the support of the Nippon Foundation.
This engine complies with SOx and NOx Tier II/Tier III regulations and also contributes to the compliance with the EEDI (CO2) regulations, meeting the three environmental emission requirements of NOx, SOx, and CO2 at the same time.
As part of a study designed to build a marine fuel cell system, the authors carried out a series of performance tests on a Polymer Electrolyte Fuel Cell (PEFC) which generates 1 kilowatt of electricity. The tests were aimed at investigating effects of fuel cell temperatures, cell stack inclination and air supply variation on power output. In these tests, the authors also examined how cell output follows load variation. The following results were obtained on the fuel cell stack the authors used: (1) Within a range of 60 to 75 degrees Celsius, the temperature level of the cell stack hardly affected power output. (2) When the cell stack was tilted up to 22.5 degrees, power output was slightly higher than the case in which the cell stack was in the upright position. This imperceptible power increase is thought to be caused by water droplets staying in the anode exhaust pipe, which resulted in a slight rise in the system pressure. (3) Even when the air utilization jumped from 25 to 60 percent, there was no sign of a remarkable drop in power output. (4) When the cell stack was in the upright attitude, power output could follow temporal changes in electrical current values. Even when the cell stack was in an inclined position, it showed high followability to rapid load changes.
Convective heat transfer in wavy channels is investigated for laminar flow between the wavy walls with unequal amplitudes. The fluid flow and heat transfer characteristics are evaluated and a thermal enhanced factor defined as a ratio of the heat transfer augmentation to the increase of pressure drop is examined. The results show that the heat transfer enhancement becomes more when the amplitude of either of the wavy walls increases. This increase of convection heat transfer is due to the formation of vortices near the wavy walls and these local circulations facilitate the mixing of the colder coolant at the center with the hotter coolant near the walls. Moreover, it was found that the location of the vortices shifts to the mainstream centerline with an increase in Reynolds number. The results also reveal that nevertheless the heat transfer augments due to better mixing of the flow as either of the wall amplitude is increased, the corresponding pressure drop is even larger for the examined cases.
The author used an experimental method to clarify characteristics of In-line flow-induced vibration of two circular cylinders. Experiments were conducted on (1) an elastic cylinder and a rigid cylinder; (2) two elastic cylinders by changing their positions in water flows and radiusdistance ratios d/a. When the rigid cylinder was in a downstream position, the range of nondimensional flow velocity that can excite hydrodynamic vibration was widened compared to the case of using a single cylinder. When the rigid cylinder was in an upstream position, the bigger d/a grew, the lower peak amplitude became compared to the single cylinder case. When the rigid cylinder was positioned vertical to flows, it had a wider excitation region than the single cylinder case. When the two elastic cylinders were placed in parallel to flows, the peak amplitudes of the upstream and downstream cylinders were higher than the case (1) with a wider range of nondimensional flow velocity. When the two elastic cylinders were placed perpendicular to flows, the peak amplitude was also higher than the case of using a single rigid cylinder. When they were placed diagonally, the vibration amplitude became smaller after they formed a large angle.