Design And Research Of Sequential Turbocharging System With Two Unequal-size Turbochargers For V Type Marine Diesel Engine

This paper designs and develops the sequential turbocharging system with twounequal-size turbochargers for V type marine diesel engine. The steady matching principlesand switching control strategies after three-zone sequential turbocharging of two unequal-sizeturbochargers for this type of diesel engine are also investigated through experiments. Theresults show that this type of diesel engine has great superiority and feasibility in adoptingsequential turbocharging system with two equal-size turbochargers.Based on TBD234V12general turbocharged diesel engine, the paper designs and buildstest-bed of sequential turbocharging system with two unequal-size turbochargers for dieselengine, selecting appropriate unequal-size turbochargers and designing intake and exhaustpipes and control system. The calculation and study of matching performance of theturbocharger with GT-Power software show that the two selected unequal-size turbochargersmatch pretty well with diesel engine and adopting three-zone sequential turbocharging ofunequal-size turbochargers can greatly improve fuel economy of diesel engine and reduceheat loads. According to the spatial arrangement of diesel engine and test-bed, two differentkinds of exhaust connecting pipes are devised and their calculating models are alsoestablished with CFD software. After computation simulation, the design of the final exhaustconnecting pipe is fixed by analyzing flow field distribution under different turbochargedstates.This paper designs control system of sequential turbocharging with two unequal-sizeturbochargers based on PLC, taking Siemens S7-300series PLC as the core to build hardwareconfiguration of control system and using the STEP7software to write the control proceduresof sequential turbocharging system with two unequal-size turbochargers used in diesel engine.The main control parameters are switching speed and switching delay. The monitoringinterface of the control system is designed based on King View software. The commissioningand operation show that the control system of sequential turbocharging with two unequal-sizeturbochargers based on PLC is safe and reliable.The steady state performance tests on standard propeller characteristics and loadcharacteristics of diesel engine adopting sequential turbocharging system with two unequal-size turbochargers are made and the universal characteristic curves of diesel engineare also presented. Steady switching principles are established depending on optimization offuel economy. The contrast with the experimental results of original engine shows that whendiesel engine runs under standard propeller characteristics, sequential turbocharging with twounequal-size turbochargers can improve economical efficiency of diesel engine greatly andexhaust temperature before turbine is significant lower than that of original engine. Dieselengine adopting three-zone sequential turbocharging of two unequal-size turbochargers canenlarge its operation range and ameliorate its performance under low speed and high load.Experimental investigations on transient switching process of sequential turbochargingsystem with two unequal-size turbochargers are carried out when diesel engine runs understandard propeller characteristics. By the study on experimental results of different switchingdelay times, switching control strategies of each switching process are determined. The studyshows that choosing reasonable switching delay time can effectively improve the engine’stransient performance during the switching process. Otherwise, if switching delay time is tooshort or two long, adverse effects will be caused both on the operation of turbochargers anddiesel engine.