Diesel-Natural Gas Engine Emissions and Performance

Exhaust emissions from compression ignition engine such as particulate matter and nitrogen oxides pollute the environment and contributes to global warming, smog and health problem. One of the strategies to overcome this problem is the diesel derivative dual fuel engine with natural gas as supplement fuel. These engines are originally sold as diesel engines. They are converted to dual fuel (diesel-natural gas) operation with an aftermarket dual fuel kit. Natural gas is blended with the intake air. As natural gas is mixed with air intake, the amount of diesel used is reduced. By substituting a portion of diesel fuel with natural gas, this engine is capable to give optimum combustion and minimum emissions. I However, this creates another problem with other emissions such as higher carbon monoxides and unburned hydrocarbons. Thus, the main purpose of this research is to quantify the emission reductions with diesel-natural gas engine and its performance. In this research a John Deere 6068H diesel engine is converted to dual fuel operation. The engine is a Tier II, 6 cylinder, 6.8 liter, 4-stroke compression ignition engine with a compression ratio of 17:1 and a power rating of 168 kW at 2200 rpm. The engine operates at 1800 rpm through five different load points in diesel and dual fuel operating modes. Data for thermal efficiency, in-cylinder pressure, and net heat release rate are presented in this study. Additionally, fuel consumption and pollutant emissions are also measured. The maximum natural gas substitution is limited by knock/engine stability or emissions of carbon monoxide and total hydrocarbons.