ANALYSIS OF NATURAL GAS SUPPLY SYSTEMS TO TWO STROKE GAS DIESELS ON LNG CARRIERS

Abstract

The classic steam turbine propulsion complex of LNG carriers is becoming  less needed. The economic factor of minimizing cargo vapor losses and strengthening environmental requirements for air emissions from ships are the main incentives for improving processing of cargo vapors and propulsion systems. Analysis of the fleet of LNG (methane) carriers under construction shows that 85 % of the methane carriers will be equipped with a propulsion system with gas diesel engines. In its turn, 30 percent of the LNG (methane) carrier fleet will be equipped with the two-stroke gas diesel propulsion  complex of the company «MAN Diesel & Turbo».The main problem connected with the implementation of this complex was the  creation of an effective gas supply system which, due to the peculiarities of the operation of a two stroke gas diesel, should supply gas at a pressure of 300 kgf/cm2 and the temperature of 45 °C. Manufacturers of the cryogenic equipment, together with «MAN Diesel & Turbo» developed two main ways to solve this problem: a system with a high-pressure compressor and a system with a high pressure pump and the evaporator. The offered systems of gas supply and their individual components are considered. The analysis of the rationality of the use of systems in a variety of operation conditions of methane carriers is considered.