Abstract: This article proposes an acoustic muffler design procedure based on finite element models and a Bi-directional Evolutionary Acoustic Topology Optimization. The main goal is to find the best configuration of barriers inside acoustic mufflers used in the automotive industry that reduces sound pressure level in the outlet of the muffler. The acoustic medium is governed by Helmholtz equation and rigid wall boundary conditions are introduced to represent acoustic barriers. The continuum problem is written in the frequency domain and it is discretized using the finite element method. The adopted objective function is Transmission Loss (TL). Increasing TL guarantees that the sound pressure level ratio between outlet and inlet of the muffler is reduced. To find the configuration of acoustic barriers that increases the Transmission Loss function of the muffler an adaptation of the Bi-directional Evolutionary Structural Optimization (BESO) method is used. Applying the proposed design procedure topologies in 2D models are reached, which raises the Transmission Loss function for one or multiple frequencies. Three examples are presented to show the efficiency of the proposed procedure.

Abstract: Several thermal management applications involve fan-mounted heat sinks that result in fan-generated noise as an undesired by-product. These applications require noise reduction and attempt to reduce noise using separate muffler devices. However, space for separate heat-sinking and noise-reducing functionalities may be challenging in high-performance applications such as electronics cooling, data centers, automotive, aviation, and various others. A first-principles-based approach for combined heat sinking and noise reduction in the same functional volume is discussed in this paper. This paper reports on thermal-acoustic co-design of 3-D periodic porous foam structures. In order to enable a design strategy, an analytical framework that characterizes the governing performance indicators of both acoustic and thermo-fluid design on a unifying platform is laid out. A combination of analytical and phenomenological models is used to predict the absorption coefficient, transmission loss (TL), and other acoustic performance indicators. For thermal predictions, an experimentally validated semiempirical model is presented to estimate thermal resistance and static pressure drop of foam heat sink as a function of geometrical parameters as well as flow rates. Octave-band weighted values of acoustic indicators are then compared against thermal indicators to investigate thermal-acoustic co-design aspects. As hydraulic pore radius of porous foam decreases, the acoustic absorption coefficient increases reaching local maxima. Concomitantly, the pore radius decrease not only increases the absorption coefficient while dissipating heat, but also increases the heat sink pressure drop. For a chosen sound absorption region of interest, there exists a particular static pressure drop that maximizes heat sink dissipation for a given radius. The paper concludes by reporting TL and heat sink thermal performance for a generic electronics cooling configuration while elucidating the nuances of the proposed heat sink design using a thermal-acoustic index.

Abstract: One of the main sources of air pollution is exhaust emission from vehicles. In the developing countries such as Indonesia, the most highest number of vehicles is motorcycle. Some of gas components from the exhaust emission that are commonly measured are carbon monoxide (CO) and hydrocarbon (HC). One of technology that can reduce the emission of CO and HC is the use of catalytic converter in the motorcycle's exhaust system/muffler to assist the oxidation of carbon monoxide (CO) and hydrocarbon (HC). In the present study, Copper-Zinc (Cu-Zn) metal was selected as the catalyst. The selection of this combination of non-noble metals is due to their low cost materials, abundant materials, low cost production, and low-temperature oxidation). The objective of this study are to prepare the catalytic converter based on non-noble metal (i.e. Cu-Zn) and to study the performance of the catalytic converter installed in the muffler in converting exhaust gases of CO and HC into less harmful gases. The effect of two different motor engine rotation speeds (i.e. 2000 and 2500) on the conversion of CO and HC was also studied. The analysis of the emission from the muffler was carried out using gas analyzer. Additionally, the kinetic of oxidation reaction of CO and HC was also studied using pseudo homogeneous approach. The emission analysis results show that the use of Cu-Zn catalyst was effective to decrease the emission level of CO and HC. The CO and HC concentration level decreased up to 47.71 % at 2000 rpm and 55.34 % at 2500 rpm, respectively.

Abstract: To provide low frequency noise control in the fluid-filled pipe systems of ships, a periodic waveguide made of an array of expansionary mufflers (referred to as anechoic nodes) installed axially on a pipe is proposed. Broad and low frequency acoustic band gaps can be generated with this periodic pipe system from the destructive interference of reflected, transmitted, and incident waves at the muffler installation nodes, and will be reinforced over some desired low frequency ranges. Within the band gaps, the transmission of acoustic noise inside the internal media of the periodic pipe system will be effectively attenuated. Key parameters for modulating the central frequency, bandwidth, and attenuation coefficient of the band gaps include the lattice constant, expansion ratio, and muffler length, and these factors are investigated following analysis of the formation mechanism of the band gaps. The results obtained in this study suggest that the introduction of a muffler array to form a periodic structure in the piping system can suppress the propagation of acoustic waves with longer wavelengths, thus achieving control of lower frequency pipe noises.

Abstract: The purpose of this paper is to improve the emission performance of diesel engines. A novel exhaust purification muffler was proposed and designed. The flow field characteristics of the exhaust pur...

Abstract: From the flow analysis of the silencer for 8 kW diesel generators, the following results were obtained. For silencer-1, it was confirmed that the holes formed at the inlet-side portion connect into the exhaust pipe in the chamber. The exhaust pipe installed inside silencer-1 was integrally connected through the holes in the chamber. As a result, it was confirmed that the pressure inside the chamber was kept stable. It was confirmed that the pressure loss generated inside an absorptive type silencer such as silencer-2 was small. The differential pressure of the inlet-outlet of silencer-1 and silencer-2 was confirmed to be 494 Pa at 15 m/s, 859 Pa at 20 m/s, 1326 Pa at 25 m/s, and 1911 Pa at 30 m/s.

Abstract: In the present study, a muffler for a 40 mm medium caliber gun is designed and manufactured. A muffler is composed of holes, blades and several spaces in the tube. Computational fluid dynamics (CFD) was performed before firing test, and the results were validated by comparing them to the test results. Numerical analysis is examined by analyzing of CFD. In conclusion, CFD was successfully applied to a muffler design. As the results of CFD and field test agreed well on the noise level. The results of test also indicated that a noise reduction about 10 dB and the muzzle velocity was almost equivalent regardless of with or without muffler.

Abstract: Expansion chamber and Helmholtz resonators are widely used in noise control. In this paper, they are combined to use as a hybrid muffler. The analysis is done to investigate the influence of the parameters of Helmholtz resonator on transmission loss. The transfer matrix method is used in the analysis. The result of transmission loss from the transfer matrix method is validated with the result from experimental two-load method using four microphones impedance tube. After had the transmission loss of the hybrid muffler been validated, the study was proceeded to investigate the effects of parameters of Helmholtz resonator on the transmission loss. The root mean square value of transmission loss were also calculated to compare the transmission losses clearly. In this paper, we investigated the effect of length of the neck of Helmholtz resonator, the effect of diameter of the neck of Helmholtz resonator, the effect of the length of the Helmholtz resonator cavity and the effect of the diameter of the Helmholtz resonator cavity for stationary medium. It is found that the transmission loss is increased when the diameter of the neck of Helmholtz resonator is increased. When the length of the neck is reduced, the transmission loss is increased. The transmission loss can also be increased by reducing the diameter of resonator cavity. It is better to increase the transmission loss at low frequencies by increasing the length of the resonator cavity.

Abstract: The invention discloses a multifunctional hardware fitting processing operation stand, which comprises polishing equipment and cleaning equipment. The polishing equipment is fixedly connected to one end of a conveyor belt, and comprises a polishing motor and a working table; the cleaning equipment is fixedly connected to the other end of the conveyor belt, and comprises a rotary motor, an air blower and a hairbrush; a muffler cover is welded on the conveyor belt; an exhaust fan is arranged on the upper end of the muffler cover; an incandescent light bulb is arranged on the lower end of the exhaust fan; the muffler cover is provided with dust collection covers at two sides of the incandescent light bulb; a waste recovery tank is fixedly connected to the other side surface of the cleaning equipment; and a control switch is arranged on an outer surface of one end, close to the waste recovery tank, of the muffler cover. The multifunctional hardware fitting processing operation stand has multiple functions when being used for processing hardware fittings through the polishing equipment and the cleaning equipment, and has a higher use value.

Abstract: The Exhaust Pipe Preheated Fuel System (EP2FS) is a fuel preheating system that utilizes wasted heat from the muffler. Fuel heating aims to improve the homogeneity of fuel and air mixtures to improve the combustion process in the engine. Making EP2FS requires careful design and calculation because the fuel temperature should not exceed 60 o C so as not to evaporate. Design and calculation, using heat transfer theory of helical heat exchanger. A ready-made system will be applied in motor vehicles to be tested for combustion efficiency and performance.

Abstract: For a GTCP36-28 auxiliary power unit (APU), a set of mufflers has been designed and tested for some representative operating conditions. The first muffler design uses cavities of different sizes in conjunction with a bias flow for efficient broadband sound absorption. The second design - also expected to perform well over a large frequency range - makes use of a variable perforation and some porous absorber material. The acoustic damping performance of the mufflers was assessed using a downstream section of dedicated microphone probes. Individual spectra and circumferential averages have been computed and are used for a comparison to a hard-walled duct section of the same length. Results show a reasonable broadband absorption for most configurations. For one operating point, significant differences were found while comparing the performance of the cavity muffler with and without bias flow. The results suggest, that a small amount of air - less than initially expected - is sufficient to obtain the desired noise reduction.

Abstract: This paper is the results of an undergraduate final term project. The aim of project was to investigate the passive noise reduction methods in mufflers. Also, another aim of this study is to examine and design mufflers with various geometries. This is learning the effect of geometry on noise transmission loss maximization performance of mufflers. Four-pole method is used to determine the noise transmission loss. Two different cross-sectional geometries are considered for the mufflers, i.e. rectangular and circular. These mufflers are produced and tested. A noise transmission test bench is used for the measurement of noise transmission loss of these mufflers. The analytical results from simulation are compared with the experimental results. The effect of geometry of mufflers on the maximization of the transmitted noise loss are investigated and reported. The results of this study can help students to learn the basics of muffler design for noise reduction applications. Furthermore, it shows the effect of geometry on the acoustic performance of mufflers.

Abstract: The utility model provides a muffler and engine intake manifold relates to the engine field. The muffler includes inner tube, urceolus and adjusting device. The inner tube is the tubular structure, has the relative inlet end and the end of giving vent to anger, inlet end and give vent to anger the pipe wall department of the inner tube between holding and be equipped with a plurality of soundproofing hole. Urceolus fixed mounting is in the outside of inner tube, and with the inner tube formation resonant cavity that matches, the gaseous produced sound wave of flowing through in the inner tubepasses through soundproofing hole and gets into the resonant cavity. Adjusting device is nested to cooperate in order to form a relatively independent annular regulation cavity in the resonant cavitywith the urceolus in the outside of inner tube, prevents the sound wave to get into and adjusts the cavity. Adjusting device is piston motion with the volume of regulation resonant cavity and soundproofing hole's quantity through the axis direction along the inner tube. This structure can guarantee to verify resonant cavity volume and synchronal induction noise of the equal bu xiang of soundproofing hole quantity and intake resistance's the circumstances under the circumstances of same intake pipe, eliminated the distubance variable, has guaranteed to verify reliably.

Abstract: The utility model discloses a double -shell automobile muffler, including shell body and interior casing, it has soundproof cotton to pack between shell body and the interior casing, be equipped withcirculating cooling water pipe between shell body and the interior casing, the inner shell is internal to be equipped with preceding baffle, median septum and back baffle, the bottom of preceding baffle is equipped with the through -hole, it has the amortization cotton to pack between median septum and the back baffle, the front end of interior casing is equipped with the intake pipe, the rear endof intake pipe is connected with the reposition of redundant personnel chamber of admitting air, the inner shell is internal to be equipped with all the first honeycomb duct that extends along the fore -and -aft direction, second honeycomb duct and third honeycomb duct, interior body case rear's bottom is equipped with main exhausting pipe, the end connection that main exhausting pipe stretches out the shell body has tail pipe, main exhausting pipe's rear portion intercommunication has exhaust branch. The utility model discloses can the separation reach the outside noise of casing through themuffler inner chamber, reduced exhaust noise intensity to avoid acid condensate water because of untimely discharge causes the inside corrosion of muffler effectively, improved the life of muffler.

Abstract: Solution: A catalyst which cleans the exhaust gas is provided in an exhaust pipe in an exhaust device that includes a muffler coupled downstream of the exhaust pipe, and an oxygen sensor is mounted on a pipe portion that is disposed downstream from the catalyst and that is directly coupled to the catalyst. The oxygen sensor is provided substantially perpendicular to the axial direction of the pipe portion through which the exhaust gas flows. The oxygen sensor includes a detecting portion, the detecting portion is disposed in a recessed portion formed in the muffler, and a wire is disposed on an outer side of the recessed portion.

Abstract: PROBLEM TO BE SOLVED: To provide an exhaust system for an engine capable of enhancing oxygen detection accuracy.SOLUTION: In an exhaust system for an engine including an exhaust pipe and a muffler connected to the downstream side of the exhaust pipe, the exhaust pipe has a catalyst, and the muffler has an expansion chamber in which exhaust gas is expanded. The exhaust pipe is extended to the expansion chamber, and the expansion chamber has a first expansion chamber and a second expansion chamber coupled to the downstream side of the first expansion chamber. The first expansion chamber and the second expansion chamber are coupled to each other by a first communication pipe, and a downstream side oxygen sensor for detecting an oxygen constituent in exhaust gas is provided downstream of the catalyst to face an opening of the first communication pipe. The exhaust pipe has a plurality of upstream side exhaust pipes and an exhaust collection section coupled to the downstream sides of the upstream side exhaust pipes. An upstream side oxygen sensor for detecting the oxygen constituent in exhaust gas is provided in the vicinity of a rear end of the exhaust collection section and on the upstream side of the catalyst.SELECTED DRAWING: Figure 2

Abstract: The utility model discloses a diesel engine post -processing system, include: blast pipe, catalytic muffler, NOx sensor, add blue jar, the supplementary injection system of compressed air, add blue nozzle and back process control unit ACU. Wherein, catalytic muffler is connected with the blast pipe for nitrogen oxide in the reduction waste gas is and reduce the exhaust noise of engine, it installsand adds blue pump, sensor and heater to add blue jar for the splendid attire urea aqueous solution, the supplementary injection system of compressed air is connected through adding the blue tube wayand adding blue jar, and the supplementary injection system of compressed air is including the measurement jet pump, add blue nozzle set up in on the blast pipe to be connected with the measurement jet pump through adding the blue tube way, back process control unit ACU and measurement jet pump communication connection for control measuring pump and compressed air solenoid valve are worked according to predetermined program. This diesel engine post -processing system reasonable in design, high, the urea injection atomization efficiency height, with low costs of integrated level.

Abstract: In this paper, the engine model is built and the boundary parameters of specified conditions are gotten by using GT-SUITE software. The acoustic performance and fluid dynamics are analyzed by means of GT-POWER software and CFX module of ANSYS software. The original muffler is evaluated by searching the transmission loss and pressure loss. Based on the simulation results and muffler theory, the relevant parameters and layout of the original muffler structure are improved. Two different improved schemes are put forward, through the obtained acoustic data and the hydrodynamic performance diagram, the mufflers of two schemes are evaluated respectively. The results show that the improved schemes are feasible to enhance the performance of muffler and noise elimination effects in high frequency performs are well. DOI: http://dx.doi.org/10.5755/j01.mech.24.5.17784

Abstract: An experimental study was conducted to generate electrical power from the waste heat of a four-stroke single-cylinder, air cooled SI engine. This study was accomplished by installing a single module thermoelectric generator (TEG) between the hot surface of the engine muffler and a heat sink.The experimental results showed that the maximum voltage generated was 5 volts at an engine speed of 2,500 rpm with a 121 °C difference in temperature between the two sides (hot and cold) of the TEG. The engine fuel consumption was 0.7 L/hr, with a maximum temperature on the hot side of 195 °C.

Abstract: The invention discloses a diesel engine after-treatment system. The diesel engine after-treatment system comprises an exhaust pipe, a catalytic muffler, a NOx sensor, a standardized aqueous urea tank,a compressed air auxiliary injection system, a standardized aqueous urea nozzle and an after-treatment control unit (ACU), wherein the catalytic muffler is connected with the exhaust pipe and used for reducing nitric oxide in waste gas and lowering the exhaust noise of an engine; the standardized aqueous urea tank is provided with a standardized aqueous urea pump, a sensor and a heater and is used for containing aqueous urea; the compressed air auxiliary injection system is connected with the standardized aqueous urea tank through a standardized aqueous urea pipeline and comprises a meteringinjection pump; the standardized aqueous urea nozzle is arranged on the exhaust pipe and connected with the metering injection pump through a standardized aqueous urea pipeline; and the after-treatment control unit (ACU) is in communication connection with the metering injection pump and is used for controlling the metering injection pump and a compressed air electromagnetic valve to operation according to preset programs. The diesel engine after-treatment system is reasonable in design, high in integration and urea injection atomizing effect and low in cost.