Mechanism of methanol and formaldehyde emissions from methanol-fueled engines

Methanol, as a low-carbon fuel, has broad application prospects in engines. The mechanism of methanol and formaldehyde was investigated respectively in a methanol premixed combustion test bench (PCTB) and a 304 stainless-steel flow reactor (SFR). The results of PCTB indicate that methanol cannot escape from the flame surface to form unburned methanol emissions. Methanol was partially oxidized to formaldehyde in the exhaust system when methanol gas is fed into the upstream exhaust. The results of SFR indicate that the onset temperature of methanol oxidation is approximately 628 K. The methanol concentration decreases rapidly with increasing temperature from 628 to 950 K. Formaldehyde increases firstly and then decreases with increasing temperature. The concentration of formaldehyde reaches the maximum at the critical temperature. At flow velocities of 8, 12, 16, 20 and 24 m/s, the critical temperature is 812, 823.4, 830, 845.5 and 850 K, respectively. This work investigates the mechanism of methanol and formaldehyde at different temperatures, flow velocities, and oxygen concentrations, and provides valuable insights into the control of methanol and formaldehyde emissions from methanol engines. • Methanol cannot escape from the flame surface during combustion. • Unburned Methanol is oxidized in the exhaust system forming formaldehyde. • Initial and complete oxidation temperatures of methanol are about 628 and 973 K. • T cri of formaldehyde are 812 to 850 K at flow velocities of 8 to 24 m/s.