Some aspects of dual fueling of the middle class modern CI engines

The paper presents results of studies on the dual fuel engine equipped with the Common Rail high pressure injection system and low pressure natural gas injection into the inlet collector. Impact of some regulation parameters of the feed system on the engine performance parameters was examined. Research of the pilot dose selection showed that the minimal size of the dose was limited to ca 12+13% of the nominal dose. It is a result of some troubles of the electromagnetic injector operation at short times of control. The effect of that is a notable deterioration of smoothness of the engine operation. However, electronic control of the injector opening timing enables to reduce the pilot dose size as the engine load is reduced. The research showed advantageous impact of the decreasing dose on the engine efficiency and exhaust gas toxicity at partial loads of the engine. The tests reconfirmed full usefulness of the system to combustion process optimization. A delay of the injection start at high engine loads enables to reduce nearly twice the NOx concentration in exhaust gas with insignificant decreasing, some 1+1.5%, of its efficiency. The used systems showed their high suitability to control charge quality in dual fuel engines, in traction applications in particular.