The Research On VGT Sequential Turbocharging Systematic Technology Of Diesel

For high-power marine diesel engines,Sequential booster technology can be used to ease the contradiction between diesel and turbocharger,improve diesel engine torque at low speed and partial load economy,and expand diesel engine operating range.But VGT supercharger technology can not only enhance the low speed diesel engine characteristics,but also raise the transient performance and strengthen the overall performance of diesel engine.In order to make the best of sequential pressurization technology and VGT supercharger technology,this paper will take GT2566 variable section turbine supercharger(VGT),J68 supercharger and TBD234V12 diesel engine as the research object.Through the performance test of turbocharger,we get the flow characteristics and efficiency characteristics of turbocharger,then establish sequential VGT turbocharged diesel engine model and carry out the related theoretical calculation and analysis.Firstly,we operate the test on the flow characteristics and efficiency characteristics of GT2556,and require the date to build the turbocharger model.Simultaneously,a method of predicting flow characteristics of variable nozzle turbine is proposed.By the test verified,the method of predicting flow characteristics can quickly obtain the flow characteristics of a variable nozzle turbine,and possess the better accuracy.Secondly,based on GT-Power software,a simulation model of TBD234V12 turbocharged and intercooled diesel engine is built.According to the existing experiment data,the original simulation model is to be tested.On this basis the original machine structure was modified to establish VGT sequential turbocharged diesel engine model.Based on the standard propeller characteristics of diesel engine,the turbocharger and diesel engine is operated performance matching calculation and divided two operating modes(1TC and 2TC)of the operating range.At the same time,by the diesel 1TC model and the diesel 2TC model of operation which means GT2556 and J68 turbocharger are running simultaneously,we study excess air ratio and air flow of the diesel engine,and the effect of 2TC on diesel economy and power is analyzed and calculated.In order to provide the data foundation for the subsequent establishment of VGT sequential transient simulation models,with the principle of optimal economy,the best nozzle ring opening and the best supercharge pressure pulse spectrum aredraught.Lastly calculated and analyzed the load characteristics and limiting characteristics of VGT sequential turbocharged diesel engines,the improvement of the main performance parameters on diesel engine is studied under different operating conditions.According to the calculation data of different working conditions and the limited characteristics,the universal characteristic curves of VGT sequential turbocharged diesel engines is drafted and compared with the original engine.It turns out that VGT sequential turbocharged diesel engines apparently expands the operating range of diesel,extends the area of low fuel consumption which is passed through by curve of propeller characteristics,and the exhaust gas temperature of diesel before the turbine drops significantly.On the basis of the universal characteristic curves of VGT sequential turbocharged diesel engines,the switching boundaries between the switching boundary of speed and the VGT nozzle ring opening of the diesel engine are determined.Then we summarize the control strategy of VGT sequential turbocharged diesel engine.Studied the transient characteristics of VGT sequential turbocharged diesel engines,the transient process of diesel engine in 2TC operating mode was simulated.The results show that due to intervention to GT2556 variable nozzle turbocharger,it greatly improved the transient characteristics of diesel engine.