Effects of the Combustion Enhancer Containing Alkyl Nitrate (CEN) to Methanol in a Direct-Injection Compression Ignition (DICI) Engine

When a biofuel, methanol is an interesting alternative for internal combustion engines (ICE). Despite drawbacks such as misfiring or instabilities at low loads, methanol has several advantages. Today, dual-fuel systems allow the use of methanol in combination with diesel fuel. This paper will present a different approach, the ability to use methanol in a flex-fuel system. The addition of a combustion enhancer containing alkyl nitrate (CEN) allows the use of methanol in a direct-injection compression ignition (DICI) engine without any changing. In this paper, different volume fractions of this additive are tested. The aim is to show the effect of the CEN on the combustion of methanol. The effect of CEN on methanol has been confirmed thanks to previous tests carried out on a Rapid Compression Machine (RCM). Ignition delay times (IDT) and auto-ignition temperature were reduced with small amounts of CEN. The engine is a single-cylinder, with a displacement of 0.499L and a compression ratio (CR) of 17.5. CEN-tested volume fractions are 0 - 1 - 2 - 5%, targeting an Indicated Mean Effective Pressure (IMEP) of 3 bar, aiming not to exceed a coefficient of variation of 5% (CoV_IMEP). Tests show that methanol combustion is highly dependent on intake conditions such as temperature and pressure, while the addition of just 1% CEN in 99% methanol reduces this dependence. Thanks to all the parameters measured, such as in-cylinder pressure or exhaust gases, these results show that methanol, with the help of CEN, could achieve some diesel-like behaviours.