Injection strategy of methanol for high loads and low NOx emissions in a neat methanol LTC engine

Abstract

Methanol is a low carbon and clean burning renewable fuel. Though low temperature combustion (LTC) of neat methanol results in almost no smoke with ultra-low NOx, the extremely low cetane number poses challenges. This experimental study demonstrates LTC of neat methanol at full load by combining direct and port injection of this fuel with controlled intake air temperature (IAT). The effects of important variables including IAT and port (premixed) and direct-injected methanol shares on combustion, performance, regulated and unregulated emissions were investigated. The timing of the direct-injected methanol had to be retarded with an increase in the premixed methanol share and IAT in order to limit the pressure rise rate without affecting the ITE. At high IATs, the premixed methanol burned first, followed by the directly injected methanol, at low IATs, these phases merged, resulting in a high rate of heat release. Employing the lowest possible IAT and the highest possible premixed methanol share led to high ITE. Increase in the MDIP to 450 bar was advantageous due to better fuel evaporation and enhanced combustion. Negligible smoke, very low NOx of 2.7 g/kWh, high ITE of 45% and unburned HC and methanol emissions lesser than 3 g/kWh could be achieved.