This report describes flow characteristics of small orifices. The experiment was carried out using a 0.4 mm diameter orifice under injection pressures from 25 to 417 atg and under back pressures up to 50 atg. The results are as follows: (1) Flow coefficient is expressed as a function of Reynolds number in the range of Et<Etc, where Et is Euler number and Etc is the critical Euler number. (2) Relation between cavitation and flow conditions is: a) Noncavitation region (Et<Etc) -laminar flow b) Transitional region - mixed flow where cavitation initiates or disappears (Et≅Etc) c) Cavitation development region (Etc<Et<200) -turbulent flow of low Reynolds number d) Limited cavitation region (Et≥200) -turbulent flow of high Reynolds number. (3) Flow characteristics of small orifices were obtained plainly. Especially for Et≥Etc and Et≥3, flow rate at small orifices is determined only by injection pressure and given by equation (17) .
Cavitation may sometimes occur, on water jacket of cylinder liners or cylinder blocks in water cooled engines to cause serious troubles due to cavitation holes penetrating through them. This cause is not water flow as in the case of cavitation generated on a propeller etc., but is air bubbles generating mechanism of which is that: a slapping phenomenon arises in a piston, a striking force on that occasion brings about vibration of a liner, the vibration produces cooling water pressure fluctuation in a water jacket, magnitude of the pressure fluctuation becomes larger than static pressure of cooling water. Thus the air bubbles are generated by the liner vibration, and micro jet stream and shock wave generated when the air bubbles collapse erode the cylinder liner and the cylinder block.
It is quite important to have a clear understanding of the air motion within the combustion chamber and resultant fuel spray pattern which have a large influence on the combustion in a direct injection diesel engine. In view of this, the authors conducted component tests, that is, steady-flow rig tests to investigate the characteristics of intake port which develops air motion in the combustion chamber and tests to observe the growth of fuel spray in a high-pressure vessel. The effects of intake port characteristics, combustion chamber shapes and fuel nozzle specifications on the specific fuel consumption and smoke were confirmed in engine tests, and were evaluated in relation to the results of component tests. Moreover, the trends of specific fuel consumption and smoke were predicted by using a combustion model. As a result, the authors could determine the effects of intake port characteristics, combustion chamber shapes and fuel nozzle specifications on the specific fuel consumption and smoke quantitatively to some degree. It was also corroborated that the results of qualitative prediction of specific fuel consumption and smoke show a good agreement with measured results.
It has already been long time ago that energy saving began to be grappled as the most important problem. So many kinds of countermeasures for energy saving have been contributed to apply them to actual ships. A super large bulk (ore/coal) carrier“HOEI MARU”was built by Kawasaki and entered into service in September 1982. She is equipped or applied with various energy saving systems and we are convinced that her successful result, especially lower fuel consumption rate for ton of cargo, opens the new page in history of such energy saving technology development.
The main engine fuel saving system reported here actively reduces fuel consumption during operation by controlling the fuel injection timing of the diesel engine and by making the scavenging air temperature fit for the changes of the environmental conditions at sea. It also improves the longevity and performance of the main engine by the abnormality diagnosis and the trend analysis. These functions are systematically controlled by the computer so as to respond directly to continuously changing external circumstances, and to process the relevant data. This paper describes outline of the system and intends to introduce some of the results of performance on board.
Recently, anti-corrosive pipe lined with rubber or polyethylene is used for sea water system, especially sea water cooling system in many vessels. In such system using lining pipe, pipes without lining are very often installed near pumps and heat exchangers in order to protect them. They are called sacrificial pipe. This paper shows the effect of the sacrificial pipe and gives the instruction for its installation. The instruction is based on two activities of the sacrificial pipe, one of which is sacrificial anode and the other is supplier of ferrous ion.