Numerical Analysis For4190Z_LC Diesel Engine’s Air Intake-Compression-Burning Processes

With the energy crisis erupted and the environmental pollution increases seriously, morestringent requirements for to the economy and emission of marine diesel engine are applied. Theobject of this study is4190ZLC type marine medium-speed diesel engine, this engine does notmeet the IMO Tier II emission standards. For these reasons, the university decided to improvethe fuel supply and fuel injection system of the engine for achieving better economy and loweremission.Multi-dimensional transient numerical simulations for4190ZLC diesel engine’s inlet andcompression processes are made by using AVL FIRE software. The effect analyses of the inletvalve movement on the flow fields inside the air-inlet and the cylinder are made; the flowfields in air-inlet and in cylinder at different instants are obtained, The researches finds that：asthe inlet valve open，instantaneous inlet flow rate increased rapidly in cylinder and the airvelocity distribution in cylinder is non-uniform；when the valve lift changes from big to small,the pressure and velocity fields gradually tend to be uniform in cylinder； When the valve lift issmall，the velocity of throat increases sharply due to the throttling effect of inlet valve; theposition of eddy current under the helical model is nearer to the inlet valve comparing to thetangential model. As the piston movement，the cylinder pressure gradually increases，turbulentkinetic energy spreads from the throat position to cylinder gradually; finally the turbulent kineticenergy and temperature distribute uniformly in cylinder.4190ZLC Diesel engine combustion model is built by using ESE-Diesel Module in AVLFIRE software. The simulation results show that: the nozzle Angle has a significant influence ondiesel engine emissions cause the oil and air mixture changed directly. When the nozzle Angle is140°the lowest NOx emissions can be obtained with140°nozzle Angle，but the smokeemissions is higher. When other conditions are equal, reduced nozzle diameter can make the spryrefine, fuel and air mixed more evenly; the smoke emissions deteriorate with0.26mm nozzlehole; NOx emissions is highest with0.28mm nozzle hole; along with the injection advanceincreases, NOx emission increases and the smoke emissions reduce.