Direct Injection of Natural Gas/Liquid Diesel Fuel Sprays

Dual-fuelling provides a suitable method for operating compression-ignition engines on alternative fuels. The CFD package Fluent is being used to model the direct-injection of two such fuels simultaneously into an engine. The CFD models have been initially calibrated using high-speed photographic visualisation of the jets. Different orientations and staging of the jets with respect to each other are now being simulated. Salient features of the two fuel jets are being studied to optimise the design of a dual-fuel injector for compression-ignition engines. Analysis of the fuel/air mixture strength during the injection allows the ignition delay to be estimated and thus the best staging of the jets to be determined