0D Laminar Flame Speed Model for Methane Lean Mixture in Dual Fuel Combustion Engine

For decades, the compression ignition (CI) engines are widespread in the market because of their reliability and efficiency. But, they have high exhaust emissions of particulate matter (PM) and nitric oxides (NOx) which can be problematic for environment. It is necessary to emphasize on reducing emissions in order to keep up with the latest stringent regulations on emissions [1, 2]. This can be achieved with the implementation of alternative solutions like the usage of after treatment systems, usage of gaseous fuels along with diesel fuel etc. The solution to use after treatment systems is not cost efficient and decreases global efficiency because of the higher pumping work required. Dual fuel operation, where gaseous fuels are used with pilot diesel injection, is considered as one efficient solutions used in diesel engines to improve exhaust emissions. Indeed, part of the diesel liquid fuel is substituted with alternative gaseous fuels [3, 4] that is introduced into the intake manifold to form a premixed charge with air, in this way both PM and NOx can be significantly reduced. Methane is mostly used gaseous fuel for the dual fuel compression ignition engine. It is an economical fuel with a wide availability across the globe. Methane is well-suited with the high compression ratios of CI engine. It has high auto-ignition temperature, low carbon content and high knock resistivity [5-8]. Nevertheless, dual fuel combustion results extremely complex to model, since it is characterized by the oxidation of two fuels presenting different physical and chemical features. As a matter of fact, a small amount of diesel, burning in a diffusive flame, starts via a multipoint ignition the propagation of a flame in the air-methane premixed charge. In the present work, a dual-fuel combustion model was built in a commercial software with the aim of simulating the experimental results and investigating the characteristics of methane-diesel combustion. The software used to build and simulate the engine model is GT-Power. Modelling a dual fuel engine with methane is an important task as the model built must respond to the inputs in accordance with experimental results. The main emphasis will be on combustion, which includes a laminar flame speed model. For methane, the combustion model available in GT power does not have pre-defined constants for laminar flame speed model. This work aims to build a laminar flame speed model and incorporate it in the combustion model of the GT power. It uses approaches from Heywood [9] and Gülder [10, 11] and it was validated with experimental results.