EXPERIMENTAL DETERMINATION OF OPTIMAL PHASES OF FUEL SUPPLY TO THE CYLINDER OF MARINE DIESEL ENGINES

Abstract

Consider the issue of experimental determination of the optimal phases of fuel supply to the diesel cylinder during the change of one type of fuel to another. It was determined that in accordance with the requirements of Annex VI of the MARPOL International Convention, the operation of marine diesel engines in some areas of the world ocean is possible only under the condition of using fuel with a sulfur content of no more than 0.1 %. Similar types of fuel are characterized by a lower auto-ignition temperature and higher calorific value. During combustion, this leads to an increase in the rate of fuel combustion and the degree of pressure increase during combustion, precisely because of this, the dynamic loads on the parts of the cylinder-piston group and diesel engine bearings increase. Also, this (due to the increase in temperature at the end of combustion) creates conditions for an increase in the concentration of nitrogen oxides in diesel exhaust gases. Reconfiguration of the high-pressure fuel equipment, namely changing the fuel injection angles, is proposed as a method that contributes to the prevention or reduction of the negative effects of these phenomena. The research was carried out on a General Cargo class vessel with a 7S50ME-B9.3-TII MAN-Diesel & Turbo main engine. Combustion pressure, the degree of pressure increase during combustion, the temperature of exhaust gases, and the concentration of nitrogen oxides in exhaust gases were chosen as the indicators for evaluating the use and implementation of the proposed method. It has been experimentally proven that this results in an increase in the environmental sustainability of diesel operation by 7.08-15.15 %, an increase in thermal stability – up to 8.93 %, and an increase in dynamic stability – up to 2.72 %. This is due to the shift of the self-ignition and combustion process towards expansion and the corresponding decrease in pressure and temperature at the end of combustion. The most favorable use of this method is on modern diesel engines that have an electronic fuel injection control system, so they do not require mechanical reconfiguration of fuel pumps. Taking this into account, the method based on the change of fuel injection angles is defined in such a way as to ensure the maintenance of environmental and energy indicators of marine diesel engines during their transfer from one type of fuel to another.