Design And Experiment Study Of Double Turbocharge Diesel Engine Exhaust System

Z8170 marine diesel engine is a very important main model for inland navigation vessels. Affected by cargo capacity, water flow, water level and water speed, the variation of the engine load is great. Particularly when the engine runs at long-term low speed and high torque condition, it requires a high response-speed turbocharger. Original Z8170 diesel engine use mixed pulse converter turbocharger system, exhaust flow at engine low speed is not enough, which caused poorly turbine acceleration response and low charge efficiency. At the same time intake flow is accordingly not enough, fuel consumption rate is high, black smoke and friction particles wear are easily happen.In order to reduce the inertia moment of the turbocharger, resolve the problem of slow working, low efficiency at low speed work condition and low response-speed. Compare the characteristics of the pulse converter, multi-pulse, MPC, MIXPC and MMPC supercharging system, and consider the real working condition of the inland navigation vessel diesel engine that is low speed and high torsion, the design of double turbocharger pulse converter system is chosen. The system could improve the response speed, reduce diesel consumption rate, meet the rated load requirements, and control production costs. In this paper, FLUENT + BOOST simulation combined with bench test is used to completed the Z8170 double turbocharger diesel engine exhaust system design work. The main work is as follows:(1) The overall design of 8170 double turbocharger system is determined after full consideration of the diesel engine fuel economy, parts commonality, maintainability and manufacturing cost and other factors.(2) According to the general layout of the diesel engine, with reference to structure domestic and foreign marine engine exhaust manifold, the exhaust manifold of several preliminary design is proposed. CREO three-dimensional mapping software is used to complete the design of the exhaust pipe circulation models, and FLUENT software is used to analyze the gas through-flow characteristics in the exhaust manifold. The exhaust manifold that has a better flow characteristics is chosen as the analysis object.(3) Based on the measured data, thermodynamic cycle analysis model of Z8170-8 single turbocharger diesel engine is calibrated. The performance of the double turbocharger diesel engine with different exhaust manifold is compared, and the optimum exhaust manifold is chosen.(4) Based on the two turbocharger parallel working designing scheme that every four cylinder connected to one turbocharger, the engine exhaust system and the intake system is designed. Diesel engine and supercharger matching performance, fuel economy and transient response characteristics is researched through the bench test.Bench test shows that when Z8170 double turbocharger diesel engine works at propulsion load, the turbocharger compressor is always running in the high efficiency range. Compared with the original Z8170 diesel engine, the double turbocharger diesel engine has the advantages of low fuel consumption rate, good transient speed regulation and short time of speed regulation.