The Impact of Gas-Air Composition on Combustion Parameters of Dual Fuel Engines Fed CNG 2002-01-2235

The paper presents the results of investigation of gas-air mixture composition impact on combustion parameters of dual fuel engine operated on CNG (Compressed Natural Gas). The tests were carried out on a single cylinder compression ignition direct injection engine. Combustion parameters calculated on base of recorded indicator diagrams were analysed. The tests have demonstrated capability of dual fuel engine to combustion gas mixtures in wide range of the composition, λ_CNG=1.8-8.0, with satisfactory efficiency. Reduce of thermal efficiency on partial loads did not exceed 6%. Combustion in dual fuel engine occurs with heat release rate reduced with 40-75% in comparison to conventional engine, what results in reduction of NOx concentration of about 30-35%. Prolongation of ignition delay with 4-6 deg.CA has been observed during the tests, what should be corrected by active change of injection advance angle of pilot dose.