Abstract
Abstract Modernisation of the power plants of cargo fleet vessels to satisfy the requirements set out by the International Maritime Organisation is an urgent scientific and technical problem. The article presents the results of developing a solution to this problem that focuses on the exhaust gas system. We propose the use of ejection nozzles as part of this system. It was found that when the ejection coefficient in these nozzles is n = 3, it is possible to exclude the use of SCR reactors, thus reducing the operating costs of the marine power plant. Using a mathematical modelling method, the efficiency of operation of six types of nozzle as part of the exhaust gas system was investigated, and a constructive layout was proposed for the gas ducts and inlet louvres for supplying ambient air. To increase the efficiency of the proposed system, we consider several options for intensifying heat transfer processes through the use of dimple systems in the nozzles and nozzles with swirling flow. We found that these technical solutions would make it possible to further increase the efficiency of the systems by up to 19% abs.
Highlights
The introduction of new requirements by the International Maritime Organisation (IMO) has given rise to a need to improve the existing cargo fleet to ensure the possibility of working under modern conditions.The main focus of these new requirements is a significant reduction in the levels of harmful emissions of NOx and SOx (Fig. 1), since these constitute the highest proportion of the exhaust gases from diesel engines [1, 2]. а bPOLISH MARITIME RESEARCH, No 1/2021The areas of operation of modern vessels are wide, and include special zones, meaning that it is necessary to implement appropriate measures to meet the requirements for emissions of harmful substances
The ejection coefficient is calculated as set out in [24]: An analysis of this graph shows that when the ejection coefficient in the nozzles is n=3, it is possible to meet the Tier III requirements for NOx emissions without using SCR reactors
The results showed that an intensification of the heat transfer processes reduces the gas temperature behind the cooler to 17% abs. when the dimple systems are used, and for swirling flow in smooth channels, this rises to 19% abs
Summary
The introduction of new requirements by the International Maritime Organisation (IMO) has given rise to a need to improve the existing cargo fleet to ensure the possibility of working under modern conditions.The main focus of these new requirements is a significant reduction in the levels of harmful emissions of NOx and SOx (Fig. 1), since these constitute the highest proportion of the exhaust gases from diesel engines [1, 2]. а bPOLISH MARITIME RESEARCH, No 1/2021The areas of operation of modern vessels are wide, and include special zones- (the South Sea, the Baltic Sea, the English Channel, etc.), meaning that it is necessary to implement appropriate measures to meet the requirements for emissions of harmful substances. The main focus of these new requirements is a significant reduction in the levels of harmful emissions of NOx and SOx (Fig. 1), since these constitute the highest proportion of the exhaust gases from diesel engines [1, 2]. One option for solving this problem is to improve the exhaust gas systems of marine power plants, and the present work addresses this topic. These systems can operate on open or closed circuits, and can be installed both on newly built vessels and as part of the modernisation of existing marine power plants. The efficiency of this approach does not exceed 95% [10], and it is advisable to develop other ways of reducing the level of NOx emissions that can help to improve the efficiency and reduce the weight-size parameters [11,12,13,14]
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