Since the invention of internal combustion engine, various kinds of diesel engines were developed for the demands and requirements of industry. The reason for the adoption of diesel engine is the fact that it can accommodate many requirements of modern ship propulsion system.
There were non-interrupted research and development in accordance with the applications and necessities required by many areas ranging small engines for agricultural uses and industrial uses, diesel engines of 50 to 550BHP for motors, some hundreds to 2,000BHP for trains, and 10,000 to over 100,000BHP for large ships.
The performance of the engine can be distinguished by economic, conductive performance and environmental affinity.
Conductive performance can be mentioned as credibility, maintenance management, minimization of components numbers, usage of lower grade heavy oil. And the economic performance means conductive expenses, conductive life, initial investment, minimization of weight, flexibility of installation. Conductive expenses include the factors resulted by thermodynamic characteristics such as heat efficiency and fuel consumption.
With this reason such as economic consideration, over 95 percent of the modern world commercial ships and navy vessels gain propulsion by Diesel engines.
Therefore, consideration of security, economy, and environmental affinity will be the direction of the development from now on.
And performance renewed consistently and finally reached current level. with a review of the process of development carried out up to now, characteristics of the diesel engine can be optimized as follows
(1) Grass-cutters, which is portable and super small-sized, 2-stroke gasoline engines are used as the power engines. The major reason is that they are simple in structure and light in weight.
(2) Little HP power engines, which is used for cars and ocean leisure, 4-stroke gasoline engines are used because they are comfortable with a small tremble.
(3) Little HP power engines for industrial uses are 4-stroke diesel engines. The reason includes the economic consideration, which is superior in fuel consumption, or heat efficiency.
(4) Medium HP power engines for industrial uses are both 4-stroke and 2-stroke diesel engines. It is because of the major consideration of economic propriety.
(5) For the merchant large ships 2-stroke diesel engines are used. The major consideration is lower fuel consumption and capability of lower-grade heavy oil application. And also cross-head engines are used, respectably.
As shown above, the structures of the engines are discernable by their application. Therefore, 2-stroke, 4-stroke, gasoline and diesel engines have distinct characteristics and have developed to optimize their superiority.
But in the range of medium sized HP, the range of the 2-stroke and 4-stroke engines are overlapping. To select the power engine in this range properly, the quantitative comparison and analysis of the characteristics in the range are need.
The characteristics of the engines can not be said simply, because they can be considered in many different view points. But it is necessary to make characteristics distinctive by comparative analysis in many different views, which can be usefully applicant to the collective judgement in the selection of a proper engine.
In this research, we will make a comparative approach which is restricted to the output performance in the view of thermodynamic cycle.