Development of a CNG-Diesel Dual Fuel Tractor with Mechanical Fuel Injection System

Identification of renewable and sustainable energy solutions remains a key focus area for the engine designers of the modern world. An avenue of research and development is being vastly dedicated to propelling engines using alternate fuels. The chemistry of these alternate fuels is in general much simpler than fossil fuels, like diesel and gasoline. One such promising and easily available alternate fuel is compressed natural gas (CNG). In this work, a 3-cylinder, 3-liter naturally aspirated air-cooled diesel engine from the off-highway tractor application is converted into a CNG Diesel Dual fuel (CNG-DDF) engine. A comparative performance shows that the thermal efficiency is up to 5% lower with CNG-DDF with respect to diesel. However, it has shown the benefit of 44% in Particulate Matter (PM), while retaining the same NOx + NMHC levels as baseline diesel engine. The cycle average CO emission was found to increase by 40% simultaneously, which has been controlled by an oxidation catalyst in the aftertreatment. The observed that exhaust gas temperature was found to be lower by 43°C with CNG-DDF. To control the particulate and HC levels of the baseline NA engine, the CNG injection has been confined from 20% to 90% engine loads, across all engine speeds. The peak firing pressure and in-cylinder temperature was lower by 3% and 7%, and the SoC got retarded by max 4°CA with CNG-DDF which is in-agreement with drop in thermal efficiency. The outcome from the engine dyno level testing has been successfully validated through the tractor testing.