When the waste oil is heated in the conventional basic operating method onboard ships, there is a trend that the level rises due to the swelling of water as the boiling of water is started when heated if the liquid high in viscosity such as lubricating oil is mixed. Thus, a sufficient empty space should be ensured in the waste oil tank when the waste oil is transferred, and in this case, a much larger empty space was ensured. Nevertheless, the waste oil overflowed the waste oil tank again. When the full running operation was started, the subsequent incineration works were stopped considering the possibility of the mixing of unexpected foreign matters (other than the conventional waste oil generated onboard) in the waste oil tank.
The emulsified fuel of water-droplet-in-oil type used in this test is of the structure that fine water particles are enveloped by the oil film, and there is a report 3) that water lower in boiling point than the fuel oil is first evaporated and inflated at a stretch when heated. It is told that this phenomenon achieves the excellent fuel oil additive effect as the small explosion effect during the after-burning period in the case of the in-cylinder combustion.
In this test, the additive was poured in order to unify the properties of the emulsified fuel, and it is considered that the water in the waste oil was enveloped and this phenomenon was further amplified. Fig.6 shows the image of the oil swelling in the waste oil tank. The test to heat the waste oil was carried out on board the ship to confirm the instantaneously bubbling phenomenon when the temperature reaches the boiling point of water. Thus, the leaked emulsified fuel in the Electric generator No. 3 was separated from other waste oils and independently collected, soaked in dothes, and incinerated in the waste oil incinerator.
4.3 Result of NOx concentration reduction
The NOx concentration, etc. in the exhaust gas was measured twice, i.e., before starting and after completing the full running operation as illustrated in Fig.7, in addition to the measurement operation, confirming that the effect of reducing the NOx concentration is maintained.
5. Influence of the use of emulsified fuel on engines, and consideration thereof
An outline is given on the maintenance works during the full running period, and the results of the engine overhaul inspection before and after the operation. The parts expected to be largely influenced were observed by the cut inspection and by the Scanning Electronic Microscope (SEM) on the running surface. In order to compare the influence of each parts in the use of the emulsified fuel, the parts for the A-oil mono-fuel combustion which were used for a similar period and the new parts which are not used were similarly inspected.
The crystalline phase of the component of the combustion products deposited on each part, and the element were analyzed by the X-Ray Diffraction (XRD) and the Electronic Probe Micro Analyzer (EPMA).
5.1 Fuel injection valve
5.1.1 Drop of valve opening pressure
The fuel injection valve was exchanged and maintained at the interval of about 900 hours in service time as usual. Generally, there is a trend that the valveopening pressure of 29.4 MPa (300 kgf/cm2) is dropped by about 0.98 MPa (10 kgf/cm2) with the A-oil mono-fuel combustion at the timing of exchange. However, the pressure drop was 1.96 to 2.94 MPa (20-30 kgf/cm2) for 5 maintenance results after the valve was used and exchanged in the emulsified fuel mode, and this pressure drop was larger than that of the A-oil mono-combustion mode. The cause thereof has not been elucidated clearly; however, it is considered that the valve opening period of the fuel injection valve is longer than that in the A-oil mono-combustion mode with the same load since more added water must be ejected during the full running condition. However, no noticeable abnormality was found in the temperature of the exhaust gas during the operation.
5.1.2 Observation of each part after the test is completed
The photos of the inside of the nozzle and the surface and cut of the needle show the trace of promotion of the corrosion on the surface of the nozzle injection holes and oil storage parts of the fuel injection valve used in the test, while no remarkable changes are found in the diameter of the injection holes.
