Research And Analysis On Exhaust Muffler Coupling Of Diesel Generating Set

The purpose of this thesis is design an exhaust muffler set to reduce the noise generated from diesel generator,particularly for a type of 220 kW diesel generator.The following research topics have been carried out:1.The influence of fluid velocity and acoustic coupling effect on the acoustic loss of the muffler is studied.Firstly,the theoretical analysis and simulation analysis of the acoustic loss of the single-stage simple resistance muffler are carried out.After comparing the results of the two analyzes,the credibility of the simulation method is verified.Then,single-stage simple resistance muffler is simulated.The results show that the velocity of the internal fluid of the muffler is reduced by the flow rate of the muffler.Finally,the structural modal and acoustic modes of the single-stage simple resistance muffler are simulated and analyzed.The influence of sound-solid coupling on the loss of acoustic sound is mainly observed in the structural modal and harmonic modes.The results show that the acoustic and acoustic coupling have effects on frequency,the loss of sound transmission has mutation at these frequencies,but the mutation is not regular.2.The interaction between the two expansion chambers in the two-stage muffler is studied.The acoustic loss of the two simple resistance mufflers and the two-stage muffler obtained by the two series are simulated respectively.Comparing results have been studies between the sum up values of the two simple resistance muffler and the two-level resistance muffler.The results show that the coupling effect between the two expansion chambers in the two-stage resistance muffler makes the acoustic loss value of the two-stage resistance muffler generally lower than that of the two simple resistance muffler.At the same time,in the low frequency band,there is a through occurred at two resistance muffler sound loss curve,and the valley close to zero,that is,the coupling effect of the muffler more than one through the frequency.In order to further enhance the acoustic performance of the two-stage muffler,the inner tube and the tailpipe are introduced into the muffler,and the acoustic loss is calculated and the structure of the endotracheal tube is improved according to the simulation results.3.The effect of small hole injection tube on the performance of muffler is studied.The results show that the introduction of the small hole injection tube obviously improves the acoustic loss of the muffler,especially in the low frequency band.Small hole injection single-stage resistance muffler sound loss is very impressive.4.In order to meet the requirements of the diesel generator muffler requirements,the two acoustic performance can be complementary to each other hole injection single-level muffler and with a tube of two-level resistance muffler.Composite hole into the multi-level muffler,and in the small hole injection multi-level muffler inside the reasonable filling of sound-absorbing material to get small hole injection impedance composite muffler.The effect of two muffler pairs on the performance of the muffler is studied.The acoustic loss of the muffler is analyzed and compared with the two mufflers before compositing.The results show that the sound loss of the muffler is improved obviously,but the low loss of sound transmission is still not ideal for some certain frequencies.It also proves the necessity of introducing resistive muffler parts.The effect of resistive muffler on the performance of muffler is studied.The acoustic loss of the muffler composite muffler is simulated and compared with the acoustic loss of the multi-level muffler.The results show that the introduction of the resistive muffler makes a more smooth acoustic loss curve.Based on the calculation of small hole injection impedance composite muffler the frequency range of transmission loss value is considerable,and can basically meet the diesel generator set acoustic reduction requirements.