Optimal Matching Of Two-stage Turbocharged System For Heavy Diesel Engine

Diesel engine is becoming increasingly popular because of its higherthermal efficiency, lower fuel consumption and lower CO2emission.Therefore,howto improve the dynamic characteristic,consumption and emission of a dieselengine becomes one of the hot topics recently. Among the numerous technicalmethods of improving engine performance, the effective one is two-stageturbocharged system for diesel engine. Diesel engine matched with two-stageturbocharged system can obtain high even super higher pressure ratio, whichmake the air mass in the cylinder increased. It is favorable for the cylindercombustion which resulted in the reduction of fuel consumption and smokeemission eventually. More fuel can be injected in the cylinder for theincreasing of air mass which improved the power per liter of the engine.Compressor with small structure and size was choosed as high stage of a two-stageturbocharged system,the pressure ratio and mass flow rate are also small inthe high efficiency zone, so the engine performance at low speed was improved.In addition, the energy distribution between high and low stages can be adjustedby a wastegate fixed in high-stage turbo.An optimum matching of Two-StageTurbocharged System for Diesel Engine can be achieve in a wider flow range.This paper based on an one-dimension engine performance simulationsoftware-GT-Power, optimal matching of two-Stage turbocharged system for sixcylinders heavy diesel engine through analogue computation and experimentalstudies. First of all, the P-V chart, torque, mass flow rate etc. were achievedthrough the calculations of the initial engine simulation model established.The computational error was controled in5%range, through the comparison withthe initial engine test and simulation data. On that basis, a two-Stageturbocharged system engine simulation model was established, the law of engineperformance affected by the two-Stage turbocharged system was calculated. In the next place, a two-Stage turbocharged system engine test bed was establishedand the evaluation was made for the capability that a two-Stage turbochargedsystem improving the engine performance. At last further optimization of thematch was made through simulation method.The result proves that, the two-stage turbocharged system can effectivelyimprove engine performance, fuel economy and cylinder combustion, especiallywhen engine working at low speed conditions. The effective specific fuelconsumption reduced8%compared with the initial engine at1200RPM. Theimprovements of engine performance reduced because of the Increases ofmechanical loss of the engine. The mass flow rate increased of the two-Stageturbocharged system engine, which can reduce the exhaust smoke. But, the richoxygen rate and combustion temperature increased in the cylinder, whichincreased the NOXemission. In addition, the augment of explosion pressure inthe cylinder improving the mechanical load and friction losses which caninfluence the reliability of the engine. The engine performance can furtherto improve through optimal matching of two-Stage turbocharged system with theengine, and the two-Stage turbocharged system engine can achieve bigger EGVratio，which reduce the NOXemission.