Prediction And Control Of Intake Noise Of Low-speed Diesel Engine

Intake noise is one of the main noise sources of turbocharged diesel engines,controlling intake noise effectively is critical.In this thesis,numerical simulation software GT-Power was employed to establish a model of the 6EX340 EF diesel engine firstly,which was verified by the experimental data.Then,the acoustic characteristics of the intake noise generated by the diesel engine are analyzed and the intake state parameters are extracted.Based on the intake state parameters obtained by simulation calculation and the empirical formula for predicting the noise of the supercharger,the noise of the compressor is predicted.Then,With the energy superposition method,the total intake noise which was superimposed by the engine noise and compressor noise of diesel engine under different loads is obtained and analyzed.Muffler is an effective method to control intake noise,in this paper,according to the frequency spectrum characteristics of the intake noise of diesel engines,an intake muffler is designed,and the transmission loss and insertion loss with four different felts are calculated using finite element method.In order to investigate the influence of the muffler structure on the acoustic performance,the insertion loss of mufflers with different throat inlet diameters,different throat diameters,different numbers of sound-absorbing blades and different felt thicknesses were calculated and analyzed.Aerodynamics is an important indicator of muffler design,and the pressure loss of the muffler has an important impact on the economy and power of diesel engines.In this paper,the CFD software was used to analyze the flow field of the intake muffler,and the contribution of muffler cavity and throat on the pressure loss under different intake air flow rates is studied.In order to explore the difference in aerodynamics of mufflers with different structures,number of sound-absorbing pieces and felt thickness on the pressure loss of the muffler was analyzed.Finally,an expansion chamber with the same pressure loss as the muffler was installed on the intake system,the dynamic and economic changes of the diesel engine under different working conditions were calculated and analyzed,and the influence of the structural change of the muffler on the performance of the diesel engine was studied.