LAUSR

Abstract Numerical simulations were performed to assess the relationship between carbon monoxide (CO) and formaldehyde and unburned methanol-unregulated emissions in cylinders and a tailpipe with ozone (O3) addition from a direct-injection spark-ignition methanol engine. This simulation study was performed during cold-start and steady-state modes with O3 addition of 3000 and 7000 ppm. The initial phase of produced CO and formaldehyde is advanced significantly with O3 addition, but the initial phase of produced unburned methanol had little impact. The effects of O3 addition on the formation and oxidation of CO, formaldehyde and unburned methanol are lower for the steady-state compared with the cold-start mode. The effects of O3 addition on CO, formaldehyde and unburned methanol production and consumption in the cylinder are formaldehyde > CO > unburned methanol. CO, formaldehyde and unburned methanol emissions decrease with increasing O3 addition. When the exhaust valve opened, CO, formaldehyde and unburned methanol emissions with 7000 ppm O3 addition for the cold-start mode are 15.3%, 52% and 70% lower than those without O3 addition, respectively. CO, formaldehyde and unburned methanol emissions with 7000 ppm O3 addition for the steady-state mode are 52.6%, 28% and 28% lower than those without O3 addition, respectively.