Numerical analysis of carbon monoxide, formaldehyde and unburned methanol emissions with ozone addition from a direct-injection spark-ignition methanol engine

Highlights: • CO and unregulated emissions with O₃ addition are numerically investigated. • Effects of O₃ addition on CO and unregulated emissions are clarify. • Effect of O₃ addition in cylinder is: formaldehyde > CO > unburned methanol. • CO and unregulated tailpipe emissions decrease with increasing O₃ addition. 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.