Optimization of Ship Propulsion Diesel Engine to Fulfill the New Requirements for Exhaust Emissions

Abstract

Impacts of exhaust gas emissions on the environment and air pollution from ships have received considerable attention in the past few decades. Due to the characteristics of the combustion process, typical for large marine two-stroke low-speed engines, and the use of residual fossil fuels, the world’s fleet emits into the atmosphere significant amount of pollutants such as nitrogen oxides (NOx), carbon monoxide (CO), carbon dioxide (CO2), hydrocarbons (HC), sulphur oxides (SOx) and carbon particles (PM). Impact assessment of the process of their formation, emitted amounts and the influence of emission are important factors for decision making in regulation development and also for engine designers who aim to improve low-speed two-stroke marine engines, for further tightening of regulations regarding limiting emissions. This paper consists of three parts: the first section describes the injection and combustion process in lowspeed two-stroke marine engines, the second part describes the formation of the exhaust as emissions as a product of the combustion process and the third part, in which the known techniques to reduce harmful emissions that are currently used in low-speed two-stroke marine engines are described.

Analysis of Exhaust Gas Emission in the Marine Two-Stroke Slow-Speed Diesel Engine

“…Also, the higher the temperature, the shorter the ignition delays. From the environmental standpoint, attempts are made to shorten the time of reactions in high temperature areas rich in oxygen [7,8].…”

Two-Stroke Low Speed Diesel Engine Simulation Model for NOx Analysis

“…Since NO is the primary product (over 90 %) of combustion in diesel engines, its formation merits further clarification. The formation of thermal nitric oxide was described in (Heywood, 1988;McAllistar et al, 2011;Lalić et al, 2014;Lalić et al, 2016). The reactions required for the formation of NO from atmospheric nitrogen have been studied extensively.…”

Sea Transport Air Pollution

“…The formation of thermal NO may be reduced by lowering and controlling the temperature peaks and minimising flue gas residence at high temperatures. As in [17], the equation for the total formation rate of thermal nitrogen oxides (NOx) is 69090 16 0,5 2 2 0,5 6 10 ,…”

“…The NOx emission limits are expressed as dependent on engine speed (n) in revolution per minute (RPM). These are shown in Table 1 and Figure 2 [6,7]. For engines with an engine speed lower than 130 RPM, the Tier III level is 3.4 g/kWh.…”

“…The MARPOL Annex VI has undertaken a review with the intention to further reduce emissions from ships. The current and upcoming limits for future fuel oil sulphur contents are presented in Table 2 and Figure 2 [6,7]. The rules of SOx apply to all ships, no matter the date of ship construction.…”