This paper presents a locally resonant phononic crystal with excellent noise reduction in the low-frequency range as a soundproofing plate in mufflers.A locally resonant phononic crystal is established,and the bandgap...This paper presents a locally resonant phononic crystal with excellent noise reduction in the low-frequency range as a soundproofing plate in mufflers.A locally resonant phononic crystal is established,and the bandgap range of the phononic crystal is analyzed by using COMSOL software.Taking the partition plate in the muffler as the object,the acoustic-solid coupling is studied to analyze the sound insulation characteristics of the locally resonant phononic crystal.A phononic crystal plate-like structure is established to analyze its noise reduction performance in the muffler.The results indicate that the locally resonant phononic crystal exhibits favorable low-frequency sound insulation performance within a bandgap range below 200 Hz.At 160 Hz,the noise reduction is 15 dB higher than that of ordinary partition plates.As the number of layers of the phononic crystal plate increases,its noise reduction effect gradually enhances,while the magnitude of the noise reduction increment tends to diminish.At 160 Hz,the single-,double-and triple-layer plates achieve peak reductions of 47,53 and 57 dB,respectively.Compared with the double-layer phononic crystal plate,the composite of the locally resonant phononic crystal plate and the steel plate has an average noise reduction of 5 dB higher.Through research and analysis of the composite locally resonant phononic crystal plates,more feasible combined structures can be provided for future muffler structural design.展开更多
The pressure loss of cross-flow perforated of physical modeling, simulation and data processing. muffler has been computed with the procedure Three-dimensional computational fluid dynamics （CFD） has been used to inv...The pressure loss of cross-flow perforated of physical modeling, simulation and data processing. muffler has been computed with the procedure Three-dimensional computational fluid dynamics （CFD） has been used to investigate the relations of porosities, flow velocity and diameter of the holes with the pressure loss. Accordingly, some preliminary results have been obtained that pressure loss increases with porosity descent as nearly a hyperbolic trend, rising flow velocity of the input makes the pressure loss increasing with parabola trend, diameter of holes affects little about pressure loss of the muffler. Otherwise, the holes on the perforated pipes make the air flow gently and meanly, which decreases the air impact to the wall and pipes in the muffler. A practical perforated muffler is used to illustrate the available of this method for pressure loss computation, and the comparison shows that the computation results with the method of CFD has reference value for muffler design.展开更多
The multilayer impedance composite sound absorption structure of the new muffler is proposed by combining the microporous plate structure with the resonant sound absorption structure of the porous material.Firstly,the...The multilayer impedance composite sound absorption structure of the new muffler is proposed by combining the microporous plate structure with the resonant sound absorption structure of the porous material.Firstly,the acoustic impedance and acoustic absorption coefficient of the new muffler structure are calculated by acoustic electric analogy method,and then the noise attenuation is calculated.When the new muffler structure parameters change,the relationship among the noise frequency,the sound absorption coefficient and the noise attenuation is calculated by using MATLAB.Finally,the calculated results are compared with the experimental data to verify the correctness of the theoretical calculation.The variation of resonance peak,resonance frequency and attenuation band width of each structural parameter is analyzed by the relation curve.The conclusion shows that it is feasible to use multilayer sound absorbing materials as the body structure of the new muffler.And the influence relationship between the change of various parameters of the sound absorption structure with the sound absorption coefficient and noise attenuation is obtained.展开更多
The equation of wave propagation in a circular chamber with mean flow is obtained. Computational solution based on finite element method is employed to determine the transmission loss of expansive chamber. The effect ...The equation of wave propagation in a circular chamber with mean flow is obtained. Computational solution based on finite element method is employed to determine the transmission loss of expansive chamber. The effect of the mean flow and geometry (length of expansion chamber and expansion ratio)on acoustic attenuation performance is discussed, the predicted values of transmission loss of expansion chamber without and with mean flow are compared with those reported in the literature and they agree well. The accuracy of the prediction of transmission loss implies that finite element approximations are applicable to a lot of practical applications.展开更多
Using the multi-physical field simulation software COMSOL,the acoustic characteristics of the multilayer sound absorbing material straight-through perforated pipe muffler are studied by the finite element method.The r...Using the multi-physical field simulation software COMSOL,the acoustic characteristics of the multilayer sound absorbing material straight-through perforated pipe muffler are studied by the finite element method.The results show that the finite element calculation of the multilayer sound absorbing material straight-through the perforated pipe muffler agrees well with the experimental measurement results.The reliability of the finite element method for studying the acoustic performance of the straight-through perforated pipe muffler with multilayer sound absorbing materials is shown.Furthermore,the influence of some structural parameters of porous sound absorbing material and micro-perforated plate on the acoustic performance of the multilayer sound absorbing material straight-through perforated pipe muffler is analyzed.The muffler based on multilayer sound absorbing material is different from the traditional muffler.After applying the multilayer sound absorbing material to the straight-through perforated pipe muffler,the transmission loss value greatly increases,which provides new ideas and directions for future research on the muffler.展开更多
A novel multi-cavity Helmholtz muffler is proposed. The multi-cavity Helmholtz muffler is composed of steel structures and silicone membranes. With suitable construction, the Helmholtz muffler can be designed to exhib...A novel multi-cavity Helmholtz muffler is proposed. The multi-cavity Helmholtz muffler is composed of steel structures and silicone membranes. With suitable construction, the Helmholtz muffler can be designed to exhibit negative mass density in low frequency, and the muffling frequency can be adjusted when we change the internal structure of the cavity,which will be very attractive for noise control. In this paper, we investigate the influence of the membranes and the cavities on noise reduction characteristics with theoretical calculations and simulations. The results show that the numbers of membranes and the volumes of the cavities can have a great effect on the position of the muffling frequency. The number of cavities can have a great effect on the width of the muffling frequency(reduce the noise by 10 dB). With different combinations of the membranes and cavities, we can get different muffling frequencies, which can meet different muffling demands in practical applications and is more flexible than the traditional Helmholtz cavity.展开更多
Ignoring the influence of flow velocity and flow temperature on muffling performance,performance tests were conducted without airflow in the development phase of the muffler which accounts to the difficulty of obtaini...Ignoring the influence of flow velocity and flow temperature on muffling performance,performance tests were conducted without airflow in the development phase of the muffler which accounts to the difficulty of obtaining a perfect match between the actual noise reduction effect and the design goal.Based on the two-load test theory,a set of high-temperature and high-speed airflow simulation measurement devices for the muffler has been built.In order to avoid the impact of high-temperature and high-speed airflow on the sensor,a high temperature resistant sensor holder has been designed for the test rig.The sound pressure has been measured in the pipe by using the lead-out measurement.In addition,a variable impedance load is placed at the end of the test tube to realize the switch between two different impedance loads by the wave handle of the variable impedance load.A sound source correction method is proposed to decrease the random fluctuation of the spectral characteristics of the output noise signal,which is caused by the acoustic impedance variation at the connection between the transition pipeline and the combined sound source system.Finally,an acoustic software has been used to calculate the transmission loss of the muffler in the presence of high temperature airflow.In comparing the experimental measurements and the simulation results,the small difference shows that:the bench not only can effectively simulate high-temperature and flow velocity environment of the engine but also accurately test the transmission loss of the muffler.展开更多
The suction muffler of hermetic reciprocating compressors is installed in order to attenuate the noise generated by the gas pulsation of the flow through the suction valve. However, the installation of the suction muf...The suction muffler of hermetic reciprocating compressors is installed in order to attenuate the noise generated by the gas pulsation of the flow through the suction valve. However, the installation of the suction muffler affects the operation of the compressor owing to gas pressure drop, which causes volumetric and energetic efficiency loss due to the gas specific volume augmentation. Therefore, there is a compromise between sound attenuation and pressure drop increase, which has to be taken into account by compressor designers. In this work, it presents a numerical solution to the flow through a suction muffler in order to analyze the pressure field and point out the main contributions to the overall pressure drop of the flow. A commercial CFD （computational fluid dynamics） code was used to perform the numerical simulations and the results were validated by using experimental data. After analyzing the pressure field, the geometry of the muffler was modified intending to decrease the flow pressure drop. The geometric modification produced a 28% reduction on the overall pressure drop, without influencing the sound attenuation.展开更多
This study represents the influence on exhaust performance by active muffler valve spring.The main experimental parameters were engine speeds and torsion coil spring constants in the active muffler.When the muffler va...This study represents the influence on exhaust performance by active muffler valve spring.The main experimental parameters were engine speeds and torsion coil spring constants in the active muffler.When the muffler valve spring has a low spring constant of k=0.75,the sound pressure level was low at the region of engine speed 2000 to 2500 r/min,and the velocity of exhaust gas was high at spring constant k=0.75.When the engine speed was under 1500 r/min,the mean concentration of CO was high in case without muffler valve.When the engine speed in the range of 1600 to 2600 r/min with spring constant k=0.75,the mean HC concentration showed the lowest value.Without muffler valve,the temperature in the muffler was higher than the case with muffler valve.This research represented that the performance of the active muffler valve spring constant k=0.75 was higher than that without muffler valve and valve spring constant k=0.70.Among the three cases of experimental condition,with a spring constant k=0.75,0.70 and without muffler valve,the exhaust performance was high in case active muffler valve spring constant k=0.70.展开更多
A mathematical model for insertion loss in a micro-perforated muffler with the effects of temperature gradient, gas flow speed and structure parameter is obtained by the mode matching technique. By dividing the microp...A mathematical model for insertion loss in a micro-perforated muffler with the effects of temperature gradient, gas flow speed and structure parameter is obtained by the mode matching technique. By dividing the microperforated tube into N segments, and assuming the flow speed and temperature are constant in each element, sound pressure and volume velocity of each segment can be readily acquired. The transmission matrix of microperforated muffler can be established based on the continuity condition of adjacent elements on the boundary. The numerical results of the present theory are calculated and the experiment is performed in Shanghai-495A engine. The experimental results of microperforated muffler show that they are in good agreement with the theoretical results.展开更多
基金National Natural Science Foundation of China(No.51705545)。
文摘This paper presents a locally resonant phononic crystal with excellent noise reduction in the low-frequency range as a soundproofing plate in mufflers.A locally resonant phononic crystal is established,and the bandgap range of the phononic crystal is analyzed by using COMSOL software.Taking the partition plate in the muffler as the object,the acoustic-solid coupling is studied to analyze the sound insulation characteristics of the locally resonant phononic crystal.A phononic crystal plate-like structure is established to analyze its noise reduction performance in the muffler.The results indicate that the locally resonant phononic crystal exhibits favorable low-frequency sound insulation performance within a bandgap range below 200 Hz.At 160 Hz,the noise reduction is 15 dB higher than that of ordinary partition plates.As the number of layers of the phononic crystal plate increases,its noise reduction effect gradually enhances,while the magnitude of the noise reduction increment tends to diminish.At 160 Hz,the single-,double-and triple-layer plates achieve peak reductions of 47,53 and 57 dB,respectively.Compared with the double-layer phononic crystal plate,the composite of the locally resonant phononic crystal plate and the steel plate has an average noise reduction of 5 dB higher.Through research and analysis of the composite locally resonant phononic crystal plates,more feasible combined structures can be provided for future muffler structural design.
文摘The pressure loss of cross-flow perforated of physical modeling, simulation and data processing. muffler has been computed with the procedure Three-dimensional computational fluid dynamics （CFD） has been used to investigate the relations of porosities, flow velocity and diameter of the holes with the pressure loss. Accordingly, some preliminary results have been obtained that pressure loss increases with porosity descent as nearly a hyperbolic trend, rising flow velocity of the input makes the pressure loss increasing with parabola trend, diameter of holes affects little about pressure loss of the muffler. Otherwise, the holes on the perforated pipes make the air flow gently and meanly, which decreases the air impact to the wall and pipes in the muffler. A practical perforated muffler is used to illustrate the available of this method for pressure loss computation, and the comparison shows that the computation results with the method of CFD has reference value for muffler design.
基金National Natural Science Foundation of China(Nos.51705545 and 15A460041)。
文摘The multilayer impedance composite sound absorption structure of the new muffler is proposed by combining the microporous plate structure with the resonant sound absorption structure of the porous material.Firstly,the acoustic impedance and acoustic absorption coefficient of the new muffler structure are calculated by acoustic electric analogy method,and then the noise attenuation is calculated.When the new muffler structure parameters change,the relationship among the noise frequency,the sound absorption coefficient and the noise attenuation is calculated by using MATLAB.Finally,the calculated results are compared with the experimental data to verify the correctness of the theoretical calculation.The variation of resonance peak,resonance frequency and attenuation band width of each structural parameter is analyzed by the relation curve.The conclusion shows that it is feasible to use multilayer sound absorbing materials as the body structure of the new muffler.And the influence relationship between the change of various parameters of the sound absorption structure with the sound absorption coefficient and noise attenuation is obtained.
文摘The equation of wave propagation in a circular chamber with mean flow is obtained. Computational solution based on finite element method is employed to determine the transmission loss of expansive chamber. The effect of the mean flow and geometry (length of expansion chamber and expansion ratio)on acoustic attenuation performance is discussed, the predicted values of transmission loss of expansion chamber without and with mean flow are compared with those reported in the literature and they agree well. The accuracy of the prediction of transmission loss implies that finite element approximations are applicable to a lot of practical applications.
基金National Natural Science Foundation of China(Nos.51705545 and 15A460041)。
文摘Using the multi-physical field simulation software COMSOL,the acoustic characteristics of the multilayer sound absorbing material straight-through perforated pipe muffler are studied by the finite element method.The results show that the finite element calculation of the multilayer sound absorbing material straight-through the perforated pipe muffler agrees well with the experimental measurement results.The reliability of the finite element method for studying the acoustic performance of the straight-through perforated pipe muffler with multilayer sound absorbing materials is shown.Furthermore,the influence of some structural parameters of porous sound absorbing material and micro-perforated plate on the acoustic performance of the multilayer sound absorbing material straight-through perforated pipe muffler is analyzed.The muffler based on multilayer sound absorbing material is different from the traditional muffler.After applying the multilayer sound absorbing material to the straight-through perforated pipe muffler,the transmission loss value greatly increases,which provides new ideas and directions for future research on the muffler.
基金Project supported by Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX18 0249)
文摘A novel multi-cavity Helmholtz muffler is proposed. The multi-cavity Helmholtz muffler is composed of steel structures and silicone membranes. With suitable construction, the Helmholtz muffler can be designed to exhibit negative mass density in low frequency, and the muffling frequency can be adjusted when we change the internal structure of the cavity,which will be very attractive for noise control. In this paper, we investigate the influence of the membranes and the cavities on noise reduction characteristics with theoretical calculations and simulations. The results show that the numbers of membranes and the volumes of the cavities can have a great effect on the position of the muffling frequency. The number of cavities can have a great effect on the width of the muffling frequency(reduce the noise by 10 dB). With different combinations of the membranes and cavities, we can get different muffling frequencies, which can meet different muffling demands in practical applications and is more flexible than the traditional Helmholtz cavity.
基金Supported by National Key Research and Development Program(2016YFD0700704B)。
文摘Ignoring the influence of flow velocity and flow temperature on muffling performance,performance tests were conducted without airflow in the development phase of the muffler which accounts to the difficulty of obtaining a perfect match between the actual noise reduction effect and the design goal.Based on the two-load test theory,a set of high-temperature and high-speed airflow simulation measurement devices for the muffler has been built.In order to avoid the impact of high-temperature and high-speed airflow on the sensor,a high temperature resistant sensor holder has been designed for the test rig.The sound pressure has been measured in the pipe by using the lead-out measurement.In addition,a variable impedance load is placed at the end of the test tube to realize the switch between two different impedance loads by the wave handle of the variable impedance load.A sound source correction method is proposed to decrease the random fluctuation of the spectral characteristics of the output noise signal,which is caused by the acoustic impedance variation at the connection between the transition pipeline and the combined sound source system.Finally,an acoustic software has been used to calculate the transmission loss of the muffler in the presence of high temperature airflow.In comparing the experimental measurements and the simulation results,the small difference shows that:the bench not only can effectively simulate high-temperature and flow velocity environment of the engine but also accurately test the transmission loss of the muffler.
文摘The suction muffler of hermetic reciprocating compressors is installed in order to attenuate the noise generated by the gas pulsation of the flow through the suction valve. However, the installation of the suction muffler affects the operation of the compressor owing to gas pressure drop, which causes volumetric and energetic efficiency loss due to the gas specific volume augmentation. Therefore, there is a compromise between sound attenuation and pressure drop increase, which has to be taken into account by compressor designers. In this work, it presents a numerical solution to the flow through a suction muffler in order to analyze the pressure field and point out the main contributions to the overall pressure drop of the flow. A commercial CFD （computational fluid dynamics） code was used to perform the numerical simulations and the results were validated by using experimental data. After analyzing the pressure field, the geometry of the muffler was modified intending to decrease the flow pressure drop. The geometric modification produced a 28% reduction on the overall pressure drop, without influencing the sound attenuation.
基金This work was supported by the Brain Korea 21 Projects,and the authors gratefully appreciate the support.
文摘This study represents the influence on exhaust performance by active muffler valve spring.The main experimental parameters were engine speeds and torsion coil spring constants in the active muffler.When the muffler valve spring has a low spring constant of k=0.75,the sound pressure level was low at the region of engine speed 2000 to 2500 r/min,and the velocity of exhaust gas was high at spring constant k=0.75.When the engine speed was under 1500 r/min,the mean concentration of CO was high in case without muffler valve.When the engine speed in the range of 1600 to 2600 r/min with spring constant k=0.75,the mean HC concentration showed the lowest value.Without muffler valve,the temperature in the muffler was higher than the case with muffler valve.This research represented that the performance of the active muffler valve spring constant k=0.75 was higher than that without muffler valve and valve spring constant k=0.70.Among the three cases of experimental condition,with a spring constant k=0.75,0.70 and without muffler valve,the exhaust performance was high in case active muffler valve spring constant k=0.70.
文摘A mathematical model for insertion loss in a micro-perforated muffler with the effects of temperature gradient, gas flow speed and structure parameter is obtained by the mode matching technique. By dividing the microperforated tube into N segments, and assuming the flow speed and temperature are constant in each element, sound pressure and volume velocity of each segment can be readily acquired. The transmission matrix of microperforated muffler can be established based on the continuity condition of adjacent elements on the boundary. The numerical results of the present theory are calculated and the experiment is performed in Shanghai-495A engine. The experimental results of microperforated muffler show that they are in good agreement with the theoretical results.
