Study On Stability Of Sequential Turbocharging Engine’s Switching Processse

Sequential turbocharing technology is widely used in naval ship diesel engine, which isan effective way to improve diesel engine steady state performance. But switching processesof sequential turbocharging engine present several problems, such as surging, speedfluctuation, black smoke, high exhaust temperature and noise. These comprehensiveperformance relative to the combustion process in cylinder and the property of combustionprocess is depended on the reasonable matching among fuel injection system, intake system,and combustion chamber.On the condition of not changing structural parameters, the sole solution is changinginjecting process and intake process for the existing types. The domestic researches mainlyfocus on intake process and build a certain theoretical system. As a consequence, this paperstarting from the aspects of injection, explores the influence of fuel delivery per cycle,injection advance angle and injection pressure on the stability of switching process forsequential turbocharging engine and provides useful information for future research.It is proposed to optimize the transient switching process of TBD234V12sequentialturbocharging diesel design by using the multi objective evolutionary algorithm. By takingthe fuel delivery per cycle per cylinder and fuel injection advance angle in cut-in delay timeas the design variables, under the constraint condition of power and maximum cylinderpressure, generating the initial uniform population by using the Sobol sequence，andoptimizing the fuel injection strategy of transient switching process by applying Pareto’snon-dominated sorting method, to get the lower fluctuation of speed and the less dischargevalue of Soot and NOx.Due to the lower accuracy of adjustment and degree of freedom of the traditionalmechanical fuel injection system, it is adverse for stably swiching and quick transition ofsequential turbocharging engine. Therefore, in order to improve the stability of optimizedsequential turbocharging diesel engine, this paper applies the advanced commercial softwareGT-Fuel to match electronic unit pump for diesel engine TBD234V12STC and simulate forelectronic unit pump, achieves simulation parameters such as the mass of fuel delivery percycle、needle valve lift and the pressure of high-pressure tube. Further simulate switchingprocess for diesel engine TBD234V12STC which electronic unit pump fuel injection system and analyse the engine’s performance and emission indexes in detail to expose superiority ofelectronic unit pump which used in sequential turbocharging diesel engine.