Abstract
With the aid of a derivative spectrophotometer, emission characteristics of formaldehyde from a methanol fueled S. I. engine were obtained. Formaldehyde and unburned methanol were measured at several distances along the exhaust tube for various air-fuel equivalence ratios and ignition timings. Experiments show that dominant oxidation of unburned methanol in exhaust system is obtained at temperatures above 400°C. However, formaldehyde levels were maintained during the exhaust movement for a fuel rich mixture. In fuel lean operation, formaldehyde increased in exhaust tube. This fact suggests that formaldehyde is formed by the oxidation of unburned methanol during the exhaust process, and the formation already begins in the cylinder. Careful experiments using a heated tube reactor set at engine exhaust port, and kept at a constant temperature range of 300-650°C probe that formaldehyde accumulation occurs in exhaust system at a temperature range of approximately 400-600°C.
