Exhaust emissions characteristics of a multi-cylinder 18.1-L diesel engine converted to fueled with natural gas and diesel pilot

A six-cylinder, turbocharged and aftercooled diesel engine was converted to operate with natural gas and diesel pilot for generator application. The flow of natural gas was electronically controlled using a throttle valve, and it was pre-mixed with air before being introduced into the combustion chambers. The aim of this work was to study the exhaust emissions characteristics under diesel and dual fuel operations at different operating conditions. Exhaust emissions of total hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), soot, particulate matter and carbon dioxide were measured at different loads. This work also presents the effects of diesel oxidation catalyst on HC and CO conversions under dual fuel operation. Results showed that NOx emission was reduced at all operating loads under dual fuel operation compared to diesel operation. HC and CO emissions were increased under dual fuel operation, but their concentrations were considerably reduced with oxidation catalyst. Contrary to conventional wisdom, it was found that soot and particulate matter were increased under dual fuel operation compared to diesel operation.