Study On Control Parameters Of Sequential Turbocharged Diesel Engine With Two Unequal Turbochargers And Design Of Exhaust Connected Pipe

Sequential turbo charging (STC) technology is one of the effective methods to overcome the difficulty in applying the turbocharger to diesel engine and improve the performance of diesel engines in low-condition. Especially for high-power V-type marine diesel engine, STC technology is the most economically feasible way. In this paper, TBD234V12 diesel engine is the research object. Through a more comprehensive theoretical calculation and analysis, the feasibility of marine V-type diesel engine with two unequal size turbochargers using three-stage STC is studied, which provide reference for the experimental research.Firstly, the simulation model of working process for the engine is established using the software GT-Power, and verified by its experimental data. On this basis, groups of GT Series turbochargers of Garrett Company are selected, which carried out matching calculation with the diesel engine. At last a more reasonable turbocharger is selected according to comparison with performance parameters of diesel engine by the propeller characteristic running.Secondly, the load and confinement characteristics of TBD234V12 diesel engine with two unequal size turbochargers system are simulated, so as to study the performance parameter variation of diesel engine after using STC system in different operating conditions. On the basis of that, universal characteristic map of diesel engine in three operating conditions is drawn, which compared with the original engine map. The results show that the operating range and low fuel consumption region are significantly expanded and diesel heat load is reduced after using two unequal size turbochargers system. According to the universal characteristic map, the switching border of the diesel engine with three-stage STC is obtained. After that, transient switching process of diesel engine are calculated and analyzed. And the control strategy of turbocharger switching process is determined.Finally, exhaust connecting pipe is designed for TBD234V12 diesel engine with two unequal size turbochargers system. In different operating conditions, the exhaust pipe is performed three-dimensional flow field computation using STAR-CD software. Analysis of its flow field characteristics provides reference for the exhaust system design and improvement. According to the flow field calculation of gas valve installed in different locations, the conclusion is that the installation position of gas valve should be as close as possible to the connecting branch pipe.