In recent years, the probabilistic safety assessment (PSA) has come to occupy an important position in the reliability estimation for the large-scale system. To take an example applied in the reliability problem of the nuclear plant, the fault tree analysis (FTA) is recognized to be a very effective method for the reliability estimation. But, it is also a fact that FTA is not easy for many users. On the other hand, the GO-FLOW methodology is not only effective but also convenient for practical use on the system reliability estimation. The GO-FLOW methodology is a software for the system reliability analysis and it is the useful way for the quantitative estimation on the reliability of large-scale system. It can be considered that the ship is a huge plant or a large-scale system. Because the ship cruising on the sea is never simply obtained in the help from others, it is important that the high reliability and the self-contained ability are provided for the safety operation on the ship. And, the GO-FLOW methodology is a good way on PSA for ship as a system. The purpose of this study is to carry out the probabilistic safety assessment for the ship equipment system. And, the actual safety condition of the ship equipment system and the failure mechanism were became clear by the quantitative analysis using the GO-FLOW methodology.
An experimental work has been carried out to explain the Diesel spray behavior. The measurement is per-formed for the spray tip penetration and the spray angle with three different injection pressures and ambient gas density. The change of ambient gas density has been done with pressured N2 gas and a high density SF6 gas. The density of SF6 gas is about 5.3 times N2 gas at room conditions. The obtained results for spray tip penetration are simplified with non-dimensional form. The form is based on Break-up length and time. As a result, the non-dimensional data with N2 gas fit to a curve that is unaffected with different injection pressure and ambient gas density. Moreovere, the measurement result (penetration and angle) with SF6 gas has been shown same result with N2 gas. Therefore, the potential of the non-dimensional expression method for the spray tip penetration is confirmed.
Recently, from the viewpoint of prevention of serious air pollution and global warming, reduction of harmful exhaust emissions and further improvement of thermal efficiency are requested. The electronically controlled hydraulic system for fuel injection had been mounted on the medium speed 4-stroke diesel engine and reduced specific fuel consumption and harmful exhaust emissions simultaneously. This time, the engine has been also added the electronically controlled hydraulic system for inlet/exhaust valve actuation and we report the test results of the engine with the electronically controlled fuel injection and inlet/exhaust valve actuation. Because the fuel injection pump and the inlet/exhaust valve were driven by hydraulic pressure on this electronic control system, time lag between control signal and motion of them existed, and unevenness caused by the electromagnetic valve motion and others existed inevitably. That was serious problem to operate the engine. To cope with that, average values of each motion-timing datum were displayed and stable operation of the engine was realized. As the experimental result, it was found that further improvement of engine performance could be expected by optimum combination of fuel injection timing and inlet/exhaust valve opening/closing timing.
The reliability of the main engine must be extremely high in order to ensure the safe navigation of ships. This paper describes the construction of monitoring system capable of grasping the condition of the engine by using vibration signal of a diesel engine. The vibration was measured by sensors on cylinder jaket walls. The data of vibration were recorded on both normal and abnormal engine conditions. The following two kinds of conditions were used as an abnormal engine condition: running with fuel oil cut and the use of stopped-up fuel injection nozzle. Author executed visual judgment by means of the spectrum of the vibration in three-dimensional mannar and analyzed statistically as one method to estimate the condition of engine by the information from the vibration. It was found that one abnormal cylinder affected on vibration of other normal cylinders. Author succeeded to recognize abnormal engine condition correctly by mean of their information.
In ship's engine room, many fire detectors are positioned for rapid detection of the onset of fire, and most of them are smoke detectors. The purpose of this study is to present a guidance for the arrangement of smoke detectors under the actual ventilating condition in engine room. As the 1st report, this paper shows the performance results of smoke detectors in some fire tests based on the combustion of marine fuel oils. In the tests, the effects of height of detectors above fire source and the speed of ventilation air were investigated. In addition, considering fire alarm tests on board, we proposed the method of fire test using smoke signals for automobiles which is equivalent to fire test using marine fuel oils.
The crew of high speed boats often have to absorb sudden shocks due to the g-forces associated with acceleration. During rapid acceleration, a secondary shock sometimes develops between the body of the crew and the boat's interior structure. The body either absorbs this shock or experiences increased vibration. Such shocks are caused by resistance to the g-forces, which are distributed throughout the body; the pressure bring dissipated in some places and concentrated in others. Analysis of the g-forces on crew members sitting in seats designed to dissipate the secondary shock revealed the need to protect the body by preventing sudden shocks and increased g-forces.