A Study on the Thermal Efficiency of a Four-Stroke Cycle Medium Speed Diesel Engine

Nowadays, fuel prices are very expensive. Therefore, reducing the fuel costs has become one of the most important concerns for shipowners. There are some methods to lower the fuel costs of a ship. But improving the performance of the main engine is fundamental. On the other hand, a diesel engine has the highest thermal efficiency among the existing power sources. So that, it is the most suitable power source these days when many efforts to save energy are considered. We are now concentrating our efforts to increase this profit. In order to do this, it is useful to list all factors concerned with the thermal efficiency of a diesel engine and to analyse their abilities. In this paper, we will report the results of our analysis. At first, we estimated the abilities of many factors including thermodynamic cycle problem, combustion rate of a fuel spray, cooling loss, gas exchange process, mechanical efficiency and heat recovery, respectively. And then we consider the total ability of all factors in combination. In conclusion, we got 60% as the maximum thermal efficiency of a diesel engine. This value can be realized using a diesel engine, a gas turbine and a Rankine cycle engine in combination. And that this value will be realized with the up-to-date technology or through improvements in existing technology. We will make this 60% value as the next target.