Progress of Direct Injection and Jet Ignition in Throttle Controlled Engines 2019-26-0045
Direct injection and jet ignition has recently become popular in motor sport racing. Pressure to reduce fuel consumption has forced most of the F1 teams to adopt jet ignition in their direct injection turbocharged engines, where operation of the turbo is controlled by the motor-generator unit connected to the turbocharger shaft. Running lean of stoichiometry and stratified, with fast combustion of reduced cyclic variability thanks to the enhanced ignition by multiple jets of hot, partially reacting products travelling the combustion chamber, the fuel consumption has been drastically reduced. Moving down from full load, despite the engine is still controlled by the throttle, it operates lean of stoichiometry λ=1.3-1.4. Despite jet ignition was historically proposed to run the engine throttle-less diesel-like by using fuel air mixtures from stoichiometric to ultra-lean, this latest development in F1 racing paves the way to better economies of passenger cars similarly operating at a fixed lean lambda over the full range of speeds and loads. The lean stratified mixture by late direct injection is less prone to knock than a homogeneous, stoichiometric mixture by early direct injection or port fuel injection. The additional opportunity to control the pressure boost by the turbocharger that may have almost any speed no matter the relative work of turbine and compressor also helps achieving knock free operation with high fuel conversion efficiencies. A further improvement being considered is the use of water injection. All these options are here discussed for passenger car engine applications, where the only downfall may be the aftertreatment.
Symposium on International Automotive Technology 2019