Conversion of Fuel Nitrogen to NO in Automotive Engines 831675
Nitrogen-free and nitrogen-doped fuels were investigated using a single-cylinder, spark-ignition engine, and gasoline and diesel-powered vehicles. The single-cylinder engine experiments showed that only NO (nitric oxide) emissions were affected by nitrogen in the fuel and that the percentage of fuel nitrogen converted to NO (PNCNO) ranged from about 5 to 100. Generally, PNCNO increased when equivalence ratio, concentration of nitrogen in the fuel, engine load, or compression ratio decreased; PNCNO also increased as the level of EGR or engine speed increased, or as spark timing was retarded from MBT.
The vehicle experiments showed PNCNO to be substantially higher (∼80-90) in gasoline engines than in a diesel engine (∼35), and that equivalence ratio, fuel-nitrogen concentration and EGR affected PNCNO in a multi-cylinder gasoline engine in the same manner as in the single-cylinder engine.
The above experimental results could be rationalized on the basis of a speculative mechanism which incorporated the fuel-nitrogen reactions, the Zeldovich reactions and their interactions.