Effect of Exhaust Gas Recirculation on Combustion and Emission Performance of a Dual Fuel CI Engine – A Numerical Investigation

Abstract

Due to the depletion of Diesel fuel and higher cost, it is desirable to find alternative fuel with lower cost and better combustion and emission characteristics. As, gaseous fuel is cheaper than liquid fuel, one of the effective solutions to obtain better engine performance is replacing a portion of liquid fuel by gaseous fuel in CI engine which is called dual fuel CI engine. In dual fuel engine, main gaseous fuel is provided through intake manifold by premixing with air and the mixture is ignited by injecting liquid pilot fuel at near the end of the compression stroke. The process is cost effective as well as the engine obtain higher thermal efficiency and lower soot, CO, UHC emission. But NOx emission is increased in CI engine with dual fuel mode which adversely affected the human health and pollute the environment. By applying Exhaust Gas Recirculation (EGR), NOx emission and knocking of the engine can be reduced. In this numerical simulation, the effect of EGR on combustion and emission performance of dual fuel CI is investigated through ANSYS Forte 18.1. In this study, gasoline is considered as main gaseous fuel and diesel is considered as liquid pilot fuel. Effect of EGR on various engine parameters such as in-cylinder pressure, temperature, heat release rate, ignition delay, combustion duration, NOx, CO and UHC emission is investigated. It is seen that, in-cylinder peak pressure is reduced to 50.65% and in-cylinder maximum temperature is reduced to 60.19% for the addition of 40% EGR. NOx emission is reduced to 57.19% for the addition of 10% EGR, 21.32% for 20% EGR, 1.57% for 30% EGR and 0.014% for 40% EGR.