An experimental study was carried out in order to clarify combustion characteristics of low grade future fuels. The tested fuels were some conventional fuels and those produced by the thermal and the catalytic cracking. The experiment was made on a high, a medium and a low speed marine diesel engine.
The main results obtained are (1) ignition lag increases with content of aromatics in the range over about 30%, (2) the exhaust gas temperature increases with content of aromatics while temperature of combustion chamber components increases with asphaltenes, (3) wear of piston rings increases with aromatics and (4) the Alumina Gel Chromatography is a recommendable method to determine content of aromatics in the case of heavy fuel oils.

抄録全体を表示

In the previous study combustion characteristics were mainly investigated based on engine tests and, as a result, FCC oils were found to be the most problematical not only in wear but also in combustion.
In this study it was tried to establish some methods to identify FCC oils. The main results obtained are (1) the molecular weight charts of GPC can clearly identify FCC oils (2) evaporation diagrams of TGA are, however, unable to identify them and (3) “particle gauge” is recommendable as an instrument on board because the gauge enables it not only to detect FCC catalyst fines but also to make broad estimation of their content in a simple practice.

抄録全体を表示

A method to estimate the fatigue crack initiation life of notched specimens from the S-N curve of smooth specimens had been proposed in the previous papers by the present authors. In the method, the local stress and strain were calculated through the relationships of cyclic stress-strain and K_σ-K_ε, where K_σ and K_ε are the stress and strain concentration factors respectively, based on the assumption that the damage in local material by local stress was just the same as the damage in material of smooth specimen by nominal stress, provided that the local stress of the notched specimen was equal to the nominal stress of the smooth one. From the test results, the applicability of the method was shown to be good for carbon steels (S35C, S15C) in reversed stress.
In order to confirm its applicability to high strength steel, fatigue tests were executed on the notched specimens of an alloy steel (SCM435). The influence of mean stress on fatigue crack initiation life of notched specimens was also investigated on both SCM435 and S15C steels. The results showed that the fatigue life prediction method proposed by the authors was valid to SCM435 and that the influence of mean stress was insignificant.

抄録全体を表示