Effect of EGR on Combustion and Emission Characteristics of Marine Dual Fuel Engines

In this paper, in order to obtain performance of marine natural gas/diesel dual fuel engine on exhaust gas recirculation (EGR), the AVL-FIRE software had been adopted to numerical effect analyze of different EGR on combustive process and emission of the engine. The result shows that numerical simulation results are consistent with the tested pressure. The bursts pressure and temperature in-cylinder decrease 4.4% and 5.4% by EGR rate increase every 10%. EGR rate increase make the temperature of the combustion area and the NO generation area in the cylinder decrease, the unburned equivalent ratio increase, the NO emission decrease. Introduction In order to reduce the NOx emission of the LNG / diesel dual fuel engine, part of the exhaust gas from the previous cycle of the engine operation is re-entered into the cylinder by using the exhaust gas recirculation (EGR), replacing part of the fresh air so that the intake charge is diluted and increased Gas heat capacity, which will reduce the combustion temperature in the cylinder. Reduced oxygen concentration, reduced combustion temperature, and reduced flame propagation rate will result in reduced NOx emissions, but a increase of HC emissions due to a decrease of oxygen concentration. With the increase in the amount of exhaust gas, the machine running cycle changes, combustion deterioration, integrated fuel consumption increased. In this paper, the effects on combustion and emission characteristics of diesel engine at different EGR rates of 0%, 10%, 20%, 30% and 40% were studied in this paper. Equations (1) is the EGR rate. EGR rate = mex. G/(mair + mex. g) (1) Where,mex. g is the amount of exhaust gas, kg/s, mair is the fresh air flow entering, kg/s. Calculation model Modeling and meshing was by using AVL-FIRE software. In order to compare the differences of combustion progress by using different exhaust gas recirculations for marine DF engine, the calculations assumed that the initial state of the cylinder pressure and temperature in cylinder were uniform. Throughout the calculation process, the cylinder is closed system, heat transfer process was according to a given wall temperature boundary conditions calculations. The calculation was 194 This is an open access article under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/). Copyright © 2017, the Authors. Published by Atlantis Press. Advances in Computer Science Research (ACSR), volume 81 2017 International Conference on Computational Science and Engineering (ICCSE 2017)