| Sequential turbocharging technology is an effective method to improve the performance of high pressurized diesel engine which is in low working condition, and also can effectively expand operational range of diesel engine, improve the economic performance and reduce emissions. If the sequential turbocharging switching points and delay time are not improper especially in transient working process of diesel engine, it is easy to make the compressor surge, supercharger over-speeding and fuel consumption increase. For switching points and delay time are the main parameters of pneumatic butterfly valve control system(PBVCS), PBVCS is important for sequential turbocharging diesel engine. PBVCS was analyzed in terms of pneumatic dynamic theory and numerical simulation comprehensively, which provided basic theory for understanding PBVCS.Using Pro/E software, based on sequential turbocharging butterfly valve control system of TBD234V12 testing engine, established the 3-D entity model of PBVCS. Basing on the pneumatic transmission theory, the mathematical model of PBVCS was established and simulation model was programmed by using the MATLAB/Simulink software. From the conclusion of simulating, air pressure influence switching time of the butterfly valve most, executive cylinder resistance is lesser, and pipe length is the least..Basing on the simulation software-FLUENT,2-D simplified calculation model of PBVCS was established. Adopting turbulent mathematical model and SIMPLE algorithm, unsteady numerical simulation model was analyzed. The conclusion shows that gas pressure, velocity and temperature of PBVCS change acutely in throttle of the electro-magnetic valve, the elbow of pipe and inlet-outlet of execution cylinder, while changing gently in the interior of the pipe and execute cylinder.Finally, in order to verify the validity of the simulantion model, detection test bench of PBVCS is designed and built. Through the comparison of test data and simulating data, when variable parameter conditions P*=0.8MPa,L=3.5m,F=3000N, simulation switching time is 0.51s which is close to the experimental result 0.47s. Curve changing trend of experimental and simulation result changing is unanimous and in a good coincidence.Getting the important factors which influent the performance of PBVCS by analyzing performance of pneumatic control system comprehensively. The factors are namely pressure of air supply, length of pipe and cylinder resistance. Feasible suggestions are put forward for improving switching time in the light of influencing factors, which provides a strong theoretical basis to lucubrate sequential turbocharging system of diesel engine. |
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