Characteristics of Auto-Ignition in Internal Combustion Engines Operated with Gaseous Fuels of Variable Methane Number

Abstract

This paper explores the feasibility of using Syngas with low methane number as fuel for commercial turbocharged internal combustion engines. The effect of methane number (MN), compression ratio (CR), and intake pressure on auto-ignition tendency in spark ignition internal combustion engines was determined. A nondimensional model of the engine was performed by using kinetics mechanisms of 98 chemical species in order to simulate the combustion of the gaseous fuels produced from different thermochemical processes. An error function, which combines the Livengood-Wu with ignition delay time correlation, to estimate the knock occurrence crank angle (KOCA) was proposed. The results showed that the KOCA decreases significantly as the MN increases. Results also showed that Syngas obtained from coal gasification is not a suitable fuel for engines because auto-ignition takes place near the beginning of the combustion phase, but it could be used in internal combustion engines with reactivity controlled compression ignition (RCCI) technology. For the case of high compression ratio and a high inlet pressure at the engine's manifold, fuels with high MN are suitable for the operating conditions proposed.