Research On The Two-stage Turbocharging System Using On Heavy-duty Diesel Engine

With the development of engine industry, the whole working condition performance of the engine is demanded more highly, many turbochargers and supercharging systems adapting to the whole condition come into being, such as variable turbocharger and two stage supercharging and sequential supercharging and release on high working condition and by-pass on low working condition. Among them, two stage supercharging attracts more and more attention, for it's better characteristic on part load performances and the broader matching scope. This paper gives some researches on two stage supercharging on the basis of full-load performance curve test on the WD615 diesel engine. Design two kinds of intake and exhaust piping system, according to the different spatial arrangement of the two turbochargers.At the beginning of this paper, the development of two stage supercharging in the domestic and foreign has been summarized. To get the boundary conditions and initial conditions of the thermodynamic calculation on turbo-charging. WD615 diesel engine is carried on the steady bench test. The BOOST model of turbo-charging is created on the basis of this experiment. Test data of fuel consumption and the exhaust temperature after the turbo and maximum combustion temperature is compared with the simulation results to correct model. On the base of keeping valve timing and some other parameters unchanged, The model of turbo-charging's intake and exhaust piping is reformed to create the BOOST model of two stage supercharging.The calculation of intensification is carried out, according to the demands of intensification. The parameters of high-pressure stage compressor's inlet is also gained, according to the calculation of low-pressure stage compressor and middle-cooling. And then, the low-pressure stage turbocharger and the high-pressure stage turbocharger is selected for two stage supercharging. Making use of the BOOST model of two stage supercharging, the thermodynamic calculation and influence regularity for the two bypass valves and the influence for the three middle-cooling is finished, and the best valve timing is determined.Three-dimensional modeling of two stage supercharging is designed by the three-dimensional software, according to the spatial arrangement of turbochargers. The inner surface in three-dimensional modeling of exhaust pipe is pulled out and created surface mesh by the software of Hyper-mesh. And then, grids is created by the software of CFD. Then, use the software of CFD to calculation the exhaust pipe of two stage supercharging to test the rationality of the exhaust pipe.