Numerical investigation of the effect of two-step injection (direct and port injection) of hydrogen blending and natural gas on engine performance and exhaust gas emissions

Abstract

The present work investigates the effect of two-step fuel injection on a four-cylinder engine which has been altered from port injection to direct injection. Hydrogen enriched compressed natural gas (HCNG) blend has been utilized as a substitute in replacement of gasoline. Initially, CNG as a 10% of the total fuel mass fraction is injected into the air manifold and the remaining 90% fuel is HCNG which is injected into the cylinder by direct injection. Primarily, the CNG was injected at 160° BTDC with 20° stroke duration. HCNG fuel was injected at 130° BTDC with a 50° stroke duration being injected from (0%–40%) step.AVL software has been utilized for this investigation to inspect the engine performance, efficiency, fuel consumption, and exhaust emissions. The collected data indicates that by injecting 30% HCNG blend, the brake power, brake thermal efficiency, and in-cylinder pressure is increased from 8% to 13.64%, and the specific fuel consumption is reduced from 6.2% to 18% due to a rise in flame propagation speed in the combustion chamber. The addition of hydrogen has decreased carbon monoxide and unburned hydrocarbons by up to 14% on a complete combustion. NOx has been increased due to the increase in the exhaust gas temperature.