ABSTRACT

Worldwide, the underwater strategic power of the seas is becoming more and more important day by day. Therefore, the place and importance of submarines in the strategic thinking of the navies are getting bigger and bigger. Submarines are considered as the most advanced and powerful combat vehicles. Due to the emergence of new power centers and threats on the seas, countries' interest in underwater warfare platforms has increased. For this reason, big investments are made in advanced, high-capability submarines. In this study, thermodynamic performance analysis of the MESMA system, which is used as an air-independent propulsion system in submarines, was made. First, the working principle of the MESMA system was shown. Energy and exergy calculations of the components that make up the MESMA system were made. A detailed combustion analysis was carried out in the part where the combustion, which is the primary and most important part of the MESMA system, takes place. Combustion products and combustion exergy of actively used methanol and ethanol fuels in the system were compared with their results in combustion with 21% and 25% oxygen ratios. The net power values of the whole system are presented by the combustion of ethanol and methanol fuels according to three different oxygen ratios, the variation of the equivalence ratio, and the combustion chamber inlet temperature. It has been found that the combustion of ethanol and methanol results in a difference between 10 and 50 kW in terms of net power. It has been shown that the power obtained increases with the increase of the oxygen ratio in the combustion. In addition, the system power increased as the combustion chamber inlet temperature increased. Although the obtained powers are close, it was concluded that methanol combustion has a significant excess of ethanol combustion when examined in terms of efficiency. There was a difference of 5 points between the two fuels in terms of efficiency. In addition, it has been examined in terms of ecological performance coefficient (ECOP) and it has been shown under which conditions a more environmentally friendly performance will be achieved. It has been demonstrated that methanol fuel is more advantageous in terms of ECOP.