Effect of oxygen supply on dual-fuel engine performance using natural gas as primary fuel

Governments world wide agree that action needs to be taken to improve the state of the environment. The use of renewable energy sources is the obvious choice to decrease carbon dioxide (CO2) emissions. Many energy fuels are therefore, being investigated as potential substitute for current high pollutant fossil fuel. The paper investigates the lean-Limit for combustion of natural gas in an unmodified diesel engine using pilot injection ignition. This report is confined to experimental work in a naturally aspirated dual gas engine. Ignition delay was noted to feature in defining light load hydrocarbon (HC) and carbon monoxide (CO) emissions. Several reasons are given illustrating why engine performance deteriorates when operating beyond this limit. Cylinder pressure and heat release diagrams indicate longer ignition delay and slower burning rates when running on natural gas. These diagrams showed improved performance with oxygen (O2) enrichment within the limit of flammability compared to normal-dual (no O2 enrichment) operation.