In two-cycle marine Diesel engine there is a movement which the efficiency of the engine power system including the propeller system is going to be improving by matching with the propeller efficiency. The reduction of engine revolution by means of the long stroke is also one way for it. It seems to be a problem to what extent the long stroke is possible in point of the scavenging action of this type of engine. From such a back ground this paper reports the experimental results that the scavenging action in case of the long stroke of this type of engine was examined by the model. Two kind of tests were done, one is one cycle scavenging model test for surveying the relation between stroke-bore ratio and scavenging efficiency, another is steady flow scavenging tests for the relation between stroke-bore ratio and the flow in the model cylinder. From the results it was found that the change of the scavenging efficiency is not big up to the stroke-bore ratio 2.00, and the extreme reducing appears in case of that is more than the stroke-bore ratio 2.00. They are discussed in the relation among the stroke-bore ratio, the scavenging efficiency and the scavenge passages in the model cylinder.
As the theme of fuel oil saving has been recently highlighted together with the theme of man power saving and that of reliability in ships, systems driving large propellers of super-low speed such as 50 rpm by low speed two cycle diesel engines are becoming systems of main stream. Electromagnetic gears can be thought as the most suitable power transmitting device installed between such super-low speed propellers and low speed diesel engines. One of the most excellent special features of the electromagnetic gears is that starting and reversing of propellers, particularly turning from normal direction running of propellers to reverse direction running can be easily carried out. In general, turning over of revolving direction of a propeller is necessary in case of crush astern and operation in port of a vessel. There are two methods of the turning over of propeller direction by electromagnetic gears, as follows: One is a method in which the direction of the propeller can be turned over while the prime mover connected with the gear is driving keeping the rotating direction of the prime mover constant, and the other is a method in which the direction of the propeller is turned over by changing the rotating direction of the prime mover. Consideration, calculation and results of tests in connection with reversing of propeller by the electromagnetic gear of the rating capacity 16, 000 ps 430/107.5 rpm are described in this paper.
A new type torsionmeter applying digital technique has been developed for the measurement of propeller shaft torque in ships. The accuracy was calibrated experimentally by applying various known twisting moments on the shaft, and it was found better than±0.12%. The torsionmeter was connected between an engine and a water-brake-dynamometer, and the transmitted torque TSon the torsionmeter and the absorbed torque TB by the water-brake-dynamometer were compared. At that time, it was found that the error of TS due to the change of temperature at the shaft was approximately 0.4%, and the error of TB due to the loss torque in the water-brake-dynamometer was approximately 1%. In order to confirm the reliability of the instrument for practical use, this measuring device was installed on an intermediate shaft connected between the main engine and the propeller shaft of the cargo vessel. On the trial trip a good agreement could be confirmed between the measurement and the estimated value that could be estimated from the cruising condition. Furthermore, torque fluctuation due to the surging phenomena of the vessel could be clearly observed on the measurement.
There have been many new developments in the studies on the formation of soot. The soot formation of hydrocarbons with air in a diffusion flame, however, is a very complicated process, from the viewpoints of both the kinetics of reaction and the effects of the mixing processes. But, little has been published on the soot formation process and measuring methods of soot particles in the flame. At the same time the intermediate products for soot formation have not been investigated. In this paper, three different fuels have been used: C3H8, C3H8/N2 (70/30, vol.%) and C2H2. The soot particles are obtained through the profiles of both the relative value and absolute quantity in which they are collected on a filter paper and a glass wool at the end of a cooled probe. The concentration in flames of methane, progressively less-saturated straight-chain hydrocarbons and polycyclic aromatic hydrocarbons (p.c.a.h) as intermediate products for the soot formation has been analysed by chromatography and ultraviolet spectrocopy. To sum up the results of our experiments, the most important points are as follows: 1) The soot particles collected on the glass wools are shown by absolute quantity as mass fraction. The distribution of soot concentration along the flame axis, regardless of the fuel, is demonstrated by the normal distribution over the flame. 2) The intermediate species for soot formation can be regarded not only as the less-saturated straightchain hydrocarbons, but also as the important role on the formation of polycyclic aromatic hydrocarbons. The relative values of p.c.a.h can be availably detected by ultraviolet absorption spectrogram. Finally, it is necessary to ensure the higher precision of soot quantity and intermediate products.
Two new advanced design multi-purpose standard cargo ships-“Friendship”and“Freedom Mark II”-have been developed jointly by IHI and the Canadian naval consulting firm of G.T.R. Campbell, to meet the pressing needs of shipowners faced with the current rise in fuel prices and the depressed shipping market, as well as the increasing severity of regulatory requirements. In realizing these designs embodying many departures from customary practices, a prominent role was played by innovations brought to the main propulsion gearing. Both types of ship feature a propulsion system comprising mainly an IHI-SEMT Pielstick medium-speed diesel engine, Integrated Main Reduction Gearing, and IHI-LIPS controllable-pitch propeller, engineered to combine overall economy of operating cost and ease of operation with enhanced plant reliability. The Integrated Main Reduction Gearing features: (1) Power take-off gearing for electric generator permitting its operation with main propulsion engine running at either 520 or 340 rpm. (2) Special gear arrangement permitting the auxiliary diesel for generator to propel the ship in the event of main engine failure or for any other special purpose (attainable speed about 6 knots) . (3) Main reduction gear assembly incorporating power take-off not only for the generator but also for all essential service pumps. The resulting Integrated Main Reduction Gearing represents a compact, efficient, reliable and easily maintained assembly capable of operating in any of the six operational modes depicted in Fig. 6.
Recently, the geared diesel plant has been gaining its position in the field of marine propulsion system because of its energy saving characteristics. Among several kinds of reduction gear, the epicyclic gear type is fairly compact and light and has been increasing its share of sales. Our company has been producing the IMT type epicyclic reduction gear, of which the basic technical patent is held by Toyo Seimitsu Zoki. This type of reduction gear is equipped with special“equalizer pins” to support the ring gear. The equalizer pin is flexible against the transmitted torque and because of this flexibility, the torsional vibration system must be specially analyzed so that the flexibility is fully represented in the calculation. In this paper, the theoretical analysis of such a system is given, then the calculation and measurement results are also shown on one particular case as an example.