USING A HIGH-PRESSURE EXHAUST GAS RECIRCULATION SYSTEM TO ENSURE THE ENVIRONMENTAL PERFORMANCE OF MARINE DIESEL ENGINES

Abstract

Introduction. The movement of sea and inland waterway vessels is impossible without the use of internal combustion engines, which are currently the main generator of mechanical energy. The use of alternative energy sources (solar, wind, as well as energy from various types of batteries) is limited to vessels that make long autonomous navigational crossings. The main type of fuel used in marine diesel engines and subsequently contributes to obtaining effective power is liquid fuel of petroleum origin. The circular operating cycle of a marine diesel engine is impossible without the formation of exhaust gases, which include dangerous toxic components. Marine diesel engines in operation require a constant search for effective ways to reduce the toxicity of exhaust gases, primarily nitrogen oxide emissions. The relevance of this task is confirmed by the requirements of international and national conventions that regulate the content of nitrogen oxides in exhaust gases depending on the type of diesel engine and the year of construction of the vessel. Ensuring the requirements of these conventions is possible by using various methods, one of which is exhaust gas recirculation. The purpose of the study is to determine the impact of the high-pressure exhaust gas recirculation system on the environmental performance of a low-speed marine diesel engine. Results. To consider the issue of ensuring the environmental performance of marine diesel engines by using high-pressure exhaust gas recirculation systems. The features of high-pressure exhaust gas recirculation systems installed on high-power low-speed marine diesel engines are highlighted. The results of research carried out on the 8G60ME MAN Diesel low-speed marine diesel engine equipped with a high-pressure exhaust gas recirculation system are presented. The design feature of these systems is the return of a certain amount of exhaust gases past the gas turbocharger to the diesel cylinder. This contributes to the deterioration of the composition of the fuel-air mixture in the cylinder and, therefore, reduces the combustion temperature. It is this phenomenon that interrupts the chain reaction of the formation of nitrogen oxides and reduces the level of their emissions. Conclusions. It has been experimentally established that changing the degree of exhaust gas recirculation in the range of 5–20 % provides a decrease in the concentration of nitrogen oxides in exhaust gases by 5.7–38.5 %, respectively, depending on the load of the diesel engine. A negative factor in using a high-pressure exhaust gas recirculation system is the increase in temperature loads on the cylinder group and the gas exhaust system of a marine diesel engine.