Effects of Non-Thermal Plasma Reformer Assisted Hydrogen Rich Gas and Hydrogen Enrichment on the Lean-Burn Performance of a GDI Engine

Abstract

The lean limit of a gasoline-fuelled spark-ignition engine can be increased by adding hydrogen to the engine thus increase the efficiency and also possible reduction of nitrogen oxide emissions. An electrical energy to non-thermal plasma discharge initiates a partial oxidation reaction in turn produces a hydrogen rich gas consisting mainly of hydrogen, carbon monoxide, and nitrogen. Two different gas mixtures were used to simulate the hydrogen rich gas (HRG) and hydrogen enrichment extending lean burn combustion GDI engine impact of various amounts of (HRG) gas were used, ranging from the equivalent of 10% - 30% of the gasoline being reformed in the hydrogen rich gas.  Theoretically Hydrogen combustion gas mixture (H₂, CO, and N₂) and typical non thermal plasma convert to hydrogen rich gas (H₂, CO, N₂, and CO₂). However, nitrogen oxides (NOx ) were found to increase hydrogen with hydrogen rich gas addition. Maximum Brake Torque (MBT) Timing verses lambda optimize experiment was conducted when spark timing was observed as a constant parameter. Hydrogen addition and hydrogen rich gas actually increases heat transfer out of the cylinder due to improved quenching distance and higher combustion temperature, thus is a straight improvement of thermal efficiency. If spark timing was retarded to MBT, taking advantage of hydrogen’s high burn speed, NOx emissions exhibited no obvious increase after hydrogen and HRG addition. Engine thermal efficiency increased with the increase of hydrogen and HRG fraction. Unburned HC always decreased with the increase of hydrogen fraction.