Study On Acoustic Performance Of Pipeline And Muffler With Temperature Gradient

Spray cooling is one of the effective ways to control the exhaust temperature of a ship’s engine.The temperature gradient in the exhaust pipe caused by spray cooling will directly affect the sound propagation speed and smoke density in the exhaust pipe,and then change the exhaust pipe.The law of internal sound propagation makes the acoustic prediction of pipes and mufflers more difficult.this paper comprehensively analyzes the influence of temperature gradient on the acoustic performance of pipe and muffler from three aspects:theoretical solution of pipe acoustics,numerical calculation of muffler finite element,engineering application and experimental research.Based on the steady-state temperature fluctuation equation,the acoustic wave equation considering linear temperature gradient is derived in this paper,and introduces the acoustic boundary conditions applicable to the exhaust pipe.The analytical solution of acoustic propagation under linear temperature gradient is obtained.The influence of temperature gradient on the acoustic performance such as sound pressure amplitude and wavelength is analyzed.By comparing the calculation results under different temperature gradients,the characteristics of the overall sound field waveform shifting towards the acoustic entrance with the increase of temperature drop gradient are obtained.For exhaust pipes and mufflers with arbitrary temperature gradient distribution caused by spray cooling,based on a self-programmed finite element program,a fast solution algorithm was written using temperature fitting method.By comparing the calculation results with the coupling calculation results of CFD virtual lab commercial software,the rationality of the coupling calculation method to solve the complex temperature gradient sound propagation caused by spray cooling is verified.Through the calculation and analysis of the spray cooling pipeline and muffler model,the influence of spray cooling on the improvement of low-frequency acoustic performance of the exhaust system is explored,which has engineering significance for the compact design of the muffler.Aiming at the typical complex structure spray-cooled exhaust muffler system,this paper uses the CFD-Virtual Lab coupling method to carry out numerical calculations of acoustic performance.A test bench is set up to conduct acoustic tests to verify the accuracyof the acoustic prediction results.The rationality of the analytic solution of temperature gradient to pipeline and muffler and the finite element numerical algorithm in this paper.