액화천연가스 고압 연료공급시스템의 운전특성에 관한 연구

Abstract

As the regulations of the International Maritime Organization have been strengthened to restrain harmful emissions from vessels, the maritime industry is making efforts to use a clean fuel, namely, natural gas as the main fuel for ships. The use of natural gas can reduce the emission of nitrogen oxides, sulfur oxides and carbon dioxide simultaneously, as compared to the heavy fuel oil used in conventional vessels. However, separate fuel supply facilities must be installed in order to safely supply fuel to engines. The main engines that use natural gas as the primary fuel for ships are generally classified into two types according to the method of injecting gaseous natural gas into the combustion chamber. One engine type uses the Diesel cycle, in which high-pressure natural gas (not less than 300 bar) is directly injected into the combustion chamber at the end of the compression stroke. The other uses the Otto cycle in which low-pressure gas is injected into the combustion chamber during the compression stroke and the piston is raised and premixed with scavenging air. The thermodynamic efficiency of Diesel cycle engines is higher than that of Otto cycle engines, but the high pressure of the natural gas supplied to the combustion chamber could cause a significant number of technical problems during equipment operation. Therefore, this study investigated the optimized operating characteristics of a fuel supply system that could supply high pressure natural gas to a marine Diesel cycle engine operated using natural gas as the main fuel. Experiments corresponding to the engine load for safe supply of natural gas to the engine were conducted, and based on the results, suggestions to improve the design were proposed.