This report outlines revisions made to IACS(International Association of Classification Societies Ltd.) UR M68 and the properties of an intermediate shaft material developed by Kobe Steel, Ltd. (40CrMo8). The company received special approval from ClassNK in February 2014 for this steel material, which has a minimum tensile strength greater than 800N/mm2.
The material has a torsional fatigue strength equal to or greater than that of conventional steel. Furthermore, the material does not exhibit any deterioration of notch sensitivity despite an increase in tensile strength.
Using this high strength intermediate shaft material is expected to increase permissible torsional vibration stresses and reduce shaft weight.
The present study has experimentally investigated the effect of fuel gas composition on the combustion and emission characteristics of a marine lean burn gas engine. The gas engine has the rated power output of 400 kW with a spark ignition pre-chamber system. In the experiments, the gas engine was operated with various fuel gas compositions using Japanese city gas mixed with propane-based LPG (P-LPG), butane-based LPG (B-LPG) and hydrogen. This paper reports in detail the experimental results on the combustion and emission characteristics of the lean burn gas engine affected by the different fuel gas compositions.
In order to raise thermal efficiency and to reduce exhaust emissions of pre-chamber type gas engines, it is important to understand combustion phenomena inside of pre-chamber and flame-jet behaviors into main chamber. A constant volume vessel was used to simulate combustion in pre-chamber type gas engines. We observed combustion phenomena in the pre-chamber and flame-jet behaviors in the main chamber using high-speed direct photography and Schlieren photography We found that the change of the igniter position in the pre-chamber showed significant changes in combustion regime in the main chamber. We also found that a change in the shape of the connecting nozzle has promoted mixing and combustion in the main chamber.
The steady and transient pool boiling experiments were performed on a horizontal cylinder in a pool of ion-exchange-distilled water at pressures of 20 kPa to 101.6 kPa. The steady state Critical Heat Flux (CHF) data under one atmosphere and sub-atmospheric pressures for the subcoolings ranging from zero up to 40 K were compared with conventional correlations such as Kutateladze and Zuber’s ones both of which are based on hydrodynamic instability. The results showed that CHF data for one atmosphere matched conventional correlations but CHF data for sub-atmospheric pressures showed higher values. The transient CHF due to exponentially increasing heat inputs, Q0exp(t/τ), with the exponential periods (τ) ranging from 20 s down to 10 ms were measured at one atmosphere and sub-atmospheric pressures for the subcoolings ranging from zero up to 40 K. It was observed that the transient pool boiling CHF values first increased with a decrease in period up to a maximum CHF, then decreased down to a minimum one and again increased with a decrease in period. The transient CHF values under sub-atmospheric pressures could be divided into two groups based on periods of exponential heat generation.