The improvement of marine boiler furnace has mainly been done emprically. This is due to the complicated phenomena such as combution, heat transfer and flow in the furnace. Among them, heat transfer by radiation is especially important because heat transfer to the furnace wall is mainly done by radiation. New analytical methods are proposed for the radiative heat transfer analysis to increase the accuracy and to reduce the computation time compared with the conventional Monte Carlo method. They are composed of the radiative heat ray method and READ (Radiative Energy Absorption Rate Distribution) method. The radiative heat ray method can calculate the radiative energy transfer from a small element of gas or wall in the furnace to other elements by using nonstochastic method. The result is used repeatedly in the iterational calculation of temperature distribution in the furnace. This method is called the READ method and eliminates the repeated calculation of radiative heat flux during the iteration which is necessary in the conventional Monte Carlo method. Temperature and wall heat flux distribution are calculated by using these methods and experimentally obtained velocity profile and flame shape. The results are compared with the experimental results and show good agreements. The radiative heat transfer diagnosis in the furnace is also carried out. This diagnosis is useful to consider the method to flatten the wall heat flux distribution.
The utilization of coal, an alternative to petroleum, has been expected to expand especially for large-size, low-speed internal combustion engines. The purpose of this investigation is to clarify the physical properties and spray characteristics of liquefied coal diesel fuel blends, and also to analyze the combustion characteristics, engine performance, and exhaust gas emissions in a small-size, high-speed diesel engine with these blends. As a result of the present investigation, it was found that the MacCoul equation describes the viscosity-temperature property of the blends, and that their spray is adequately and perhaps better atomized than usual diesel fuel sprays. The recommended blending ratio of liquefied coal fuel is 40v-% or less to achieve smoke reduction with a minimum increase in specific heat consumption, noise, and NOx emissions. Some of the combustion properties of the blends such as ignition lag, smoke, noise and others, can be evaluated qualitatively by the cetane index calculated from the API density and the 50% distillation temperature.
FCC slurry bottom oil and FCC cycle oil are getting used as base stock for making a marine heavy fuel even in Japan. The marine heavy fuel which contains FCC slurry bottom oil and FCC cycle oil contains small quantity of catalyst fines, because it can not be recovered completely by a catalyst reclaimer. The catalyst fines in a fuel oil are very abrasive ones and wear engine parts such as piston rings, a cylinder liner and parts of a fuel injection pump. But, few data concerned with the relation between catalyst fines and engine wear have been presented, specially the quantitative relations. Therefore, influence of catalyst fines on engine wear has been investigated by the engine tests with the heavy fuels contained known quantities of catalyst fines. The five kinds of heavy fuels which contain catalyst fines of 0, 30, 60, 100 and 150 ppm, were prepared for the engine tests. The engine test of 30 hour duration was carried out for each fuel. Main items measured included the wears of piston rings, a cylinder liner, crank-pin metals, a plunger, a barrel, a delivery valve and a needle valve, and Fe and n-pentane insoluble contents in lubricant. From the test results, the followings are concluded. 1. Piston ring and cylinder liner wears increase in proportion to an increase of catalyst fines content in a fuel oil. 2. In the case of a trunk piston type engine, Fe and n-pentane insoluble contents in lubricant increase in proportion to an increase of catalyst fines content in a fuel oil, and crank pin metal wear increases consequently.
The exhaust gas economizer is one of the most efficient measures for the exhaust heat recovery of the Diesel ship. In responding the strong demand of the fuel conservation, various advanced plants with turbo-generating system have been developed and have been successfully installed onto the Diesel ships in service. In spite of the difficulties of the decreasing gas temperature, the decreasing gas flow rate, the severe deterioration of fuel grade, etc., those newly developed plants have achieved the remarkable improvement of the exhaust heat recovery rate in comparison with the plants in the age of 1969. The main technological features of the advanced plants are the followings, that is, the first is the introduction of two-or three-stage pressure system, the second is the use of extended heating surface, and the third is the designs of various countermeasures against the low temperature fouling and corrosion. These features, however, have brought not only desirable improvements but also undesirable impacts such as the damage of generating tubes, the soot fire etc. Although most of impacts have already been overcomed, the soot fire, which is the most impressive and serious fault, is still troubling the people concerned and is demanding the reliable solution.