Research On Control Method Of Two Stage Sequential Turbocharging System For Large Power Diesel Engine

With the increase of power density and the requirement of performance optimization under all working conditions,the requirements of turbocharging system for diesel engines are becoming higher and higher.The two-stage sequential turbocharging technology adopts different supercharging schemes according to the different working conditions of diesel engine,so as to expand the range of efficient operation of the supercharging system,and meet the requirements of higher average effective pressure and larger operating range of diesel engine.In this paper,150 Diesel engine is equipped with two-stage sequential turbocharging system,and the operation law of its steady-state and transient switching process is studied。Aiming at the phenomenon of compressor surge and reverse flow during the switching process of two-stage sequential supercharging,the GT power / Simulink coupled simulation model of sequential turbocharging was established.The steady-state and transient conditions were tested and verified,and the simulation error was controlled within 5%.Based on the principle of energy distribution,a two-stage sequential turbocharging system is matched for 150 Diesel engine,and the turbocharging regulation scheme for land and water conditions is determined.Compared with the original engine,the fuel consumption rate of the diesel engine is reduced by8.7% under the external characteristic condition of 1000 r / min.The fuel consumption of diesel engine is reduced by 2.1% at 2400 r / min.The rated volumetric power of the diesel engine is increased from 44.1k W/L to54.4k W/L.The switching process of single-stage sequential supercharging and two-stage sequential supercharging is studied.Through reasonable opening delay time of intake valve,the energy loss of controlled turbocharger caused by compressor backflow can be avoided,and the speed fluctuation of diesel engine during the cut in process of single-stage sequential supercharging is reduced by 39 r/min,and that of two-stage sequential supercharging is reduced by 17 r/min.The surge duration of the controlled supercharger can be shortened by the delayed closing of the intake valve during the switching out process of the supercharger.The energy distribution law of two-stage sequential turbocharging system is studied.The exhaust energy distribution control can be realized by using the bypass valve.During the switching process,the optimal opening angle of the bypass valve is 45 °,so that the transient turbine power increases by 16.1% when the turbocharger cuts in and 12.6% when the turbocharger is cut out.By adjusting the opening speed of the intake and exhaust valves and the transient coordinated control with the bypass valve,the fluctuation of diesel engine speed can be reduced by 11r/min when the turbocharger is cut out.