Controlling natural gas combustion timing in HCCI engine with synthetic gas enrichment using a chemical kinetic model

In recent years, HCCI engines have been in the center of attentions due to their high thermal efficiency, low emission rate (e.g. NOx) and low fuel consumption. The main drawback in these engines is the combustion control, which happens in a limited operation range between the knock and misfiring. The natural gas is a commonly used fuel in internal combustion engines (ICE). However, using the natural gas in HCCI engines is challenging due to its low tendency to the self-ignition. Hence, approaches like the reformer gas enrichment should be employed. In this paper, a zero-dimensional model was introduced in order to predict combustion timing and investigate effects of the variable composition reformer gas with different contents of H2 and CO. Experimental results from a single-cylinder CFR engine was used to validate the proposed model. Results showed that the addition of synthetic gas (RG) and changes in the H2 content of RG could affect ignition timing and could be used in the combustion control in HCCI engines, which expanded the limit of the operation, increased the engine efficiency and reduced the fuel consumption especially in lower air/fuel ratio and the inlet temperature.