Muffler Design Research Articles

Design and performance analysis of multi-section expansion chamber muffler based on Actran

Abstract. In order to compare and analyze the influence of different structural parameters on the muffler performance of multi-section expansion chamber muffler, this paper explores the main factors affecting the noise suppression performance through the transmission loss formula, and it establishes the model of two cylindrical expansion chamber silencer. The muffler expansion chamber is analyzed by changing the section number of the muffler expansion chamber, the cross-section diameter of the front and rear expansion chamber, the length of the front and rear expansion chamber, the length of connecting tube, the arrangement order of expansion chamber with different cross-section area and the arrangement order of expansion chamber with different length. The simulation results show that the muffler volume can be effectively increased by increasing the number of expansion chamber and the cross-section diameter of expansion chamber. The length of the expansion chamber does not show the peak value of the transmission loss curve, which only affects the span of the transfer loss curve; the order of the expansion chamber with different diameters and the arrangement order of the expansion chamber with different lengths have little influence on the transmission loss peak value of the muffler; the change of the length of the connecting tube affects the span of the transmission loss curve, but the peak value of the transfer loss curve is not affected. This study can be used as a reference for the design of a multi-section expansion chamber silencer.

Structural Performance Analysis and Optimization of Small Diesel Engine Exhaust Muffler

In recent years, the optimization of diesel engine exhaust mufflers has predominantly targeted acoustic performance, while the impact on engine power performance has often been overlooked. Therefore, this paper proposes a parallel perforated tube expansion muffler and conducts a numerical analysis of its acoustic and aerodynamic performance using the finite element method. Then, a Kriging model is established based on the Design of Experiments to reveal the impact of different parameter couplings on muffler performance. With transmission loss (TL) and pressure loss (PL) as the optimization objectives, a multi-objective optimization study is carried out using the competitive multi-objective particle swarm optimization (CMOPSO). The optimization results indicate that this method can simplify the optimization model and improve optimization efficiency. After CMOPSO calculation, the average TL of the muffler increased from 27.3 dB to 31.6 dB, and the PL decreased from 1087 Pa to 953 Pa, which reduced the exhaust noise and improved the fuel economy of the engine, thus enhancing the overall performance of the muffler. This work provides a reference and guidance for the optimal design of mufflers for small agricultural diesel engines.

Innovative silencer for window air inlets

This presentation introduces an innovative window air inlets silencer. The product is intended for exterior installation, tailored to match the standard dimensions of window air inlets, specifically the slot through the window. It is designed to complement internal window air inlet equipment. The silencer's design encompasses multiple functionalities. The main one is reducing external noise transmission (such as traffic, airport, and city center noise) from outside to inside the room equipped with the air inlet. Additionally, it minimally impacts air flow, ensures resistance to water and sunlight, offers washability for accumulated dust, and emphasizes aesthetics compared to other existing silencers. The development of the silencer involves a comprehensive approach, incorporating numerical simulations, optimizations, prototypes, and standard experimental tests. The performance of the developed silencer is compared with similar products already available in the market.

The effect of muffler design on reducing the noise pollution of a small two-stroke engine

Designing an efficient muffler for single-cylinder IC engines is not an easy task due to the limitation in designing a large muffler and the possibility of engine suffocation. In this regard, this research aims to experimentally investigate the feasibility of inexpensive muffler modification of a small portable two-stroke engine to reduce noise pollution. In experiments, the default muffler as a control treatment and a modified muffler together with a redesigned muffler have been examined to investigate the effect of muffler internal geometry and muffler design on sound emission characteristics. Based on the obtained results, the sound pressure level (SPL) of the modified and redesigned mufflers decreased by 5.31 and 6.86 percent compared to the default muffler, respectively. Meanwhile, installing the modified and redesigned mufflers increased the transmission loss (TL) equal to 8.62 % and 10.08 % compared to the default muffler, respectively. Also, the outcome of Discrete Fourier Transform (DFT) revealed that the intensity and amplitude of output frequencies from the redesigned muffler was significantly reduced in the frequency range of 2–6 kHz. As a general conclusion of this study, by installing the redesigned muffler, the maximum working times of the operator increased by 12.1 h at 5000 rpm.

Analytical, computational, and experimental investigations on the impact of side outlet on the simple expansion chamber with axial outlet

In this study, an investigation on the acoustic performance of a simple expansion chamber muffler with side outlet has been presented. The investigation for the muffler is done in the 10–2400 Hz frequency range. The muffler is analyzed analytically, computationally, and experimentally. The computational and analytical modellings of the muffler have been done by using the finite element and transfer matrix methods, respectively for the determination of transmission loss. As the transfer matrix method is unable to capture the higher order modes above the cut-off frequency of the muffler, the finite element method has been adopted as the computational method. Additionally, the accuracy in the analytical and computational modelling of the muffler is checked with the experimental investigation. The two-load method is used in this study for muffler to determine the transmission loss and band power. The side outlet of the muffler introduces an extra impedance due to the shunt element and hence the effectiveness of the muffler can be improved. This muffler shows an overall improvement of 24.73 dB in the transmission loss when compared with the transmission loss of the simple expansion chamber muffler with an axial outlet in 10–2400 Hz frequency range. Specifically, the simple expansion chamber muffler with side outlet is more effective than the simple expansion chamber muffler with an axial outlet in 350–680 Hz, 1040–1350 Hz, 1570–1590 Hz, and 1850–2400 Hz frequency ranges. The comparison among the different techniques shows a fair agreement in the results. The transmission loss, variation of the band power in the 1/3rd octave band, and sound pressure level contours for the muffler at the selected frequencies have been presented. This study offers an advantage in the design of the automotive mufflers.

Design and simulation of an exhaust muffler for a single cylinder diesel engine for the Wuzheng tricycle model 7YPJ-1750PD

Design and simulation of an exhaust muffler for a single cylinder diesel engine for the Wuzheng tricycle model 7YPJ-1750PD

Muffler Design for Noise Reduction and Pressure Loss Optimization Using Multiobjective Genetic Algorithm

The muffler plays a crucial role in reducing the noise generated by the internal combustion engine exhaust gases. Therefore, an effective muffler design should be capable of significantly reducing noise levels. However, we must also consider backpressure, which can negatively impact engine performance. Backpressure is the additional pressure exerted by the muffler towards the engine, and it can have adverse effects on engine performance, thus requiring minimization. These two objectives often conflict with each other. Hence, in this research, we utilize multiobjective genetic algorithms as a tool to optimize muffler design. Inspired by the natural selection process, genetic algorithms aim to find a muffler design that is not only effective in reducing noise but also produces minimal backpressure. Thus, this study aims to achieve a balance between noise reduction and backpressure minimization in muffler design. The multiobjective genetic algorithm proposes 105 muffler design solutions. These solutions are not dominated by each other against both TL and PL objectives. The design that has the best value in the TL objective is solution 1 with TL and PL values of 26.06 dBA and 2.27 kPa. The design that has the best value in the PL objective is solution 3 with TL and PL values of 8.36 dBA and 1.87 kPa. The muffler compromise design chosen was a solution 41 with TL and PL values of 17.78 dBA and 2.07 kPa.

Design and Analysis of the Exhaust Muffler for Two-Wheeler Vehicle

The muffler is an essential part of every type of car. On two-wheelers, however, it disperses flue gases throughout the atmosphere and reduces engine noise to a bearable level. It is occasionally called an exhaust muffler or a muffler. A silencer's main function is to block off noise produced when flue gas rushes past it quickly. Furthermore, the exhaust gases ought to be released into the atmosphere. The primary focus of this work is on two-wheeled vehicle exhaust mufflers. The current exhaust silencer design is subjected to CFD and fluid structure interaction analysis with engine-specific boundary conditions. The specifications will guide the creation of the muffler's design. ANSYS, a finite element analysis tool is used to measure and verify exhaust gas temperatures, velocities, and back pressure. Furthermore, a modal analysis is conducted to figure out how a geometric adaptation affects the fundamental frequency of the system. The actual testing consists of fabricating a customized exhaust silencer and evaluating it for noise and back pressure on a two-wheeler engine test rig.

Design and verification of diesel generator exhaust muffler

The exhaust muffler is one of the most effective methods to control the exhaust noise of diesel generator. In this paper, a new type of impedance composite muffler is designed for the spectral characteristics of diesel engines and the shortcomings of existing mufflers. The main idea of the design is to reasonably design the key structures such as the length-diameter ratio, the insert-pipe, and the sound-absorbing material of the muffler under the condition of keeping the shape unchanged and low cost, so as to achieve the broadband noise reduction performance and improve the working efficiency of the diesel engine. The basic structure of the designed muffler is introduced. The transmission loss and pressure loss are numerically simulated and analyzed by finite element method, and the experimental verification is carried out. The results show that the structural parameters of the muffler have little effect on the transmission loss in the low frequency range, and the influence is more obvious in the middle- and high-frequency range. Compared with the existing muffler, the designed muffler significantly improves the noise reduction performance and reduces the exhaust back pressure.

Recent Developments in Using a Modified Transfer Matrix Method for an Automotive Exhaust Muffler Design Based on Computation Fluid Dynamics in 3D

The present work aims to investigate the newly modified transfer matrix method (MTMM) to predict an automotive exhaust muffler’s transmission loss (AEMTL). The MTMM is a mixed method between a 3D-CFD (Computation Fluid Dynamics in 3D), namely AVL FIRETM M Engine (process-safe 3D-CFD Simulations of Internal Combustions Engines), and the classic TMM for the exhaust muffler. For all the continuous and discontinuous sections of the exhaust muffler, the Mach number of the cross-section, the temperature, and the type of discontinuity of the exhaust gas flow were taken into consideration to evaluate the specific elements of the acoustic quadrupole that define the MTMM coupled with AVL FIRETM M Engine for one given muffler exhaust. Also, the perforations of intermediary ducts were considered in the new MTMM (AVL FIRETM M Engine linked with TMM) to predict the TL (transmission loss) of an automotive exhaust muffler with three expansion chambers. The results obtained for the TL in the frequency range 0.1-4 kHz agree with the experimental results published in the literature. The TMM was improved by adding the AVL FIRETM M Engine as a valuable tool in designing the automotive exhaust muffler (AEM).

Establishing the parameters of the operation mode of the electric pulse automobile muffler

The purpose of the research in the article is to obtain analytical and experimental results on the purification of internal combustion engine exhaust gases by an electric pulse, allowing us to determine the main parameters of the muffler operation. The set goal was achieved by performing the following methodology. A mathematical model of the motion of a gas particle in a muffler has been developed and investigated, the relationship between the capacity of the engine combustion chamber, the number of revolutions of the crankshaft, the pulse intensity, and the dynamic viscosity of the medium has been established. The condition of the muffler operation is determined through the parameter - the distance between the electrodes. The optimality criterion is justified - the smokiness of the gas before and after purification. A nonlinear experimental plan has been compiled using the methods of similarity theory and dimension analysis. An experimental stand has been developed and results linking the process parameters have been obtained. The results obtained are the basis for the methodology for calculating the design of electric pulse mufflers with optimal smoke ratios.

Analysis of Noise Level with Convergent and Divergent Shape of Muffler and its Impact on Noise Pollution

Noise pollution is one of the key hazards that decreases people's quality of life globally. Due to the rapid development of technology, industrialization, urbanization, and transportation networks, noise pollution has reached serious levels in recent years. Sound transmission loss, the attenuation of sound as it passes through diverse objects and environments, is crucial in lowering noise pollution and preserving the acoustic integrity of ecosystems. Due to de-throttling tactics implemented to optimize cylinder fill, the intake system of internal combustion engines is the primary noise source while the vehicle is at low speeds and high loads. Therefore, achieving high acoustic performance of intake systems constitutes a critical issue in complying with the increasingly stringent European regulations for overall noise emission. The Transmission Loss computation is typically the most used technique for describing a system's acoustic performances. This work provided an overview of sound transmission loss and discussed its substantial environmental effects. It investigates the fundamentals of sound transmission, the factors that influence it, and the environmental impacts of sound attenuation. This paper proposed a comparison of three designs like straight duct (muffler), convergent and divergent design of muffler. The main aim is to observe sound transmission loss and compare the noise level with three muffler configurations with the same gas volume. High transmission loss indicates more noise reduction in muffler design, which will help reduce environmental noise pollution.

SIMULATION OF MUFFLER PARAMETERS IN VENTILATION CHANNELS OF VENTILATORS

During long-term observation of the operation of the ventilator (artificial lung ventilation) of the UVENT-T model, a violation of repeatability was noticed under the same operating conditions. That is, on some devices of this particular model, the air flow sensor under the same conditions showed different values when repeating the measurements.Through experiments, it was established that this is caused by the unevenness of the air flow inside the ventilation channels of the ventilator, which is most likely caused by the design of the silencers installed there.The article highlights the process of research and modeling of air flow in ventilation channels of ventilators of the apparatus due to the manufacture of several test variants of muffler designs, which should solve the problem of various deviations of flow measurements. The main idea was to change the number and size of the muffler holes. Obviously, the 5 holes of 2 mm scattered the air flow too much, due to which there was an increased risk of turbulence in the air flow, which could have caused the unevenness of its measurements. Therefore, on all new mufflers, the holes were reduced to1 mm, but their number was increased by 2 times. In total, 6 design options were obtained. All 6 options were designed in CAD SolidWorks, and flow simulation was also carried out for test models. According to the results of air flow measurements, graphic dependencies were obtained for each of the silencer samples, namely the integral of the absolute error of the flow measurement, the integral of the flow noise power, the integral of the acoustic noise power and the maximum absolute error of the flow measurement.In the future, it is proposed to develop a mathematical model of laminar air flow in a ventilator taking into account new designs of silencers, as well as to develop software for testing according to the developed algorithm and model. Conduct experimental testing of designed mufflers, as well as evaluate the results of the experiment. According to the research results, a conclusion will be made about the most effective muffler design, and its design will be used inthe production of ventilators.

Design and demonstration of composite mufflers based on dissipative and reactive units

We have proposed and validated a design of a composite muffler. By a combination of dissipative and reactive units with different operating mechanisms, the advantages of both structures are utilized to achieve high transmission loss (TL) from low to high frequency in the ventilation duct system. A dissipative muffler composed of porous sound absorbing materials (PSAM) is chosen for noise attenuation above 1000 Hz, and a reactive muffler composed of Helmholtz resonators is used to reduce the noise below 1000 Hz. The combination of the two can achieve a TL above 20 dB in the broadband range of 244–1600 Hz and up to 30 dB in the vast majority of the frequency band, demonstrating excellent noise reduction effect. The proposed composite muffler has great advantages in broadband noise reduction for ventilation systems.

Harmonizing Muffler Design: The Virtuoso Performance based on Inlet Diameter, Outlet Diameter and Material in Orchestrating Transmission Loss

This research paper delves into the intricate relationship between muffler design & acoustic performance, uncovering a symphony of variables that influence transmission loss (TL dB) in muffler systems. This comprehensive analysis explores the impact of inlet diameter, outlet diameter, muffler length, and material choice on noise reduction, presenting a nuanced understanding of their roles in achieving optimal acoustic outcomes. The data reveals that increasing the inlet diameter generally enhances noise reduction, akin to a conductor orchestrating a crescendo of frequencies. This effect is particularly pronounced during the transition from an inlet diameter of 15 to 19, resembling a musical composition reaching a breathtaking climax. Conversely, enlarging the outlet diameter plays a consistent baseline, driving frequencies to higher octaves with unwavering precision.
 Muffler length emerges as a significant factor, the longer mufflers consistently exhibit higher TL values, although exceptions exist. Like a subtle harmony in a musical composition, the length of the muffler occasionally introduces its own unique influence. Material choice, akin to soloists in an orchestra, presents its own set of unique characteristics.
 In the intricate realm of refrigeration systems, where science and engineering converge, refrigerants take centre stage as the virtuoso performers of the heat transfer ballet. With an artful choreography that rivals any stage production, elegant transition of these refrigerants takes place from gas to liquid and back to gas, all the while embracing and relinquishing heat with finesse. It's a performance that keeps our environments comfortable and our perishables preserved. In this captivating spectacle of thermodynamics, a diverse cast of refrigerants takes the limelight. Hydro-fluorocarbons (HFCs) like R-134a and R-410A perform their roles with precision, offering a symphony of cooling capabilities. Hydro-chlorofluorocarbons (HCFCs), once stalwarts of the industry, exemplified by R-22, now take a humble exit, prompted by environmental concerns, as the show must evolve.

Optimized muffler design and its performance evaluation to environmental noise reduction on classrooms

Generators powered by diesel engines are widely used as a backup source of electrical energy. However, the generator produces very high noise, which is around 73–110 dBA. In this study, we designed a muffler and optimized to the highest possible noise reduction. We constructed and installed the designed muffler to evaluate the performance an absorptive muffler on the exhaust pipe of the simulated muffler with the installed one. We measured the sound pressure level (SPL) at the source of exhaust gas noise before the proposed muffler installed and after installation, including inside the surrounding classrooms. A survey was also conducted to determine the annoyance response of the teachers and the students. The results show that the presence of an absorptive muffler can reduce noise by 10 dBA and attenuate more at high frequencies (<500–16000 > 500–16000 Hz) at the source of the noise and also in the surrounding environment. The annoyance rating for generator exhaust noise is moderate to very disturbing for listeners who are outside the room and moderate for listeners positions in the room.

Comparison of the Efficiency of Cleaning the Exhaust Gas of Internal Combustion Engines of Cars with Ultrasonic Emitters

. The conducted research is connected with ultrasonic cleaning of exhaust gases of internal combustion engines of passenger cars running on gasoline. A hypothesis is proposed for the use of ultrasonic radiation to clean exhaust gases from harmful impurities and solid particles. An experimental automobile muffler has been developed that simulates the ultrasonic cleaning process. The results of experimental studies are presented, proving the possibility and efficiency of using the process of ultrasonic cleaning from harmful impurities and solid particles. Experimental data on changes in toxic impurities and the dependence of the mass of solid particles (soot) on the settling distance are shown, which will be used in the calculation and design methodology when creating the design of an ultrasonic automobile muffler

Sensitivity analysis and noise reduction optimization design of the insert-pipe double expansion chamber muffler

The insert-pipe double expansion chamber muffler has less passbands and higher sound attenuation in the plane wave range, which is widely used to reduce noise of industrial equipment. But there are many parameters that affect the transmission loss of the insert-pipe double expansion chamber muffler, and the sensitivity of each factor is not clear. Identifying the most influential factor among numerous parameters is an important challenge. It is necessary to investigate the sensitivity of all parameters and study parameter optimization algorithms. Based on the method of transfer matrix analysis, this paper studies the insert-pipe double expansion chamber muffler and its sound elimination mechanism. The global sensitivity analysis of the transmission loss of insert-pipe double expansion chamber muffler was conducted using Sobol's method, and the influence of each parameter sensitivity was examined. According to the noise characteristics of an air conditioner compressor, the external penalty function method (EPFM) algorithm is used to optimize the insert-pipe double expansion chamber muffler, and the maximum transmission loss is obtained in a specific frequency band. According to the optimized parameters, the muffler is designed, manufactured, and installed in a pipeline system to carry out a noise experiment to verify the effectiveness of the optimization scheme.

Case study: Noise attenuating performance of perforated corrugated lined straight-through perforated pipe-resistant muffler

Noise of internal combustion engine is the main source of noise pollution, and mufflers are the main means to reduce exhaust noise of internal combustion engine. In the process of improving the acoustic performance of the exhaust muffler based on the three-dimensional numerical method, the influence of the high speed and high temperature airflow discharged by the engine in the actual working process on the acoustic performance of the exhaust muffler is often ignored, which leads to the obvious deviation between the predicted results and the actual situation. In this paper, based on the structural optimization design of the straight-through perforated pipe resistance muffler, the noise characteristics of the straight-through perforated pipe resistance muffler with perforated corrugated lining was analyzed considering the airflow velocity and temperature inside the muffler. The influence of temperature and velocity fields on the acoustic performance of muffler was studied by using numerical simulation method, which takes the solution results inside muffler as boundary conditions of sound field analysis. The influence of changing the internal structure of muffler on the aerodynamic performance of muffler was discussed, and the pressure loss is analyzed. The research has shown that adding perforated corrugated lining inside muffler could effectively improve the transmission loss of muffler and the noise reduction performance of prototype straight-through perforated pipe-resistant muffler.

State of the art of rational design of efficient mufflers

An efficient exhaust muffler needs to satisfy the rather conflicting requirements of adequate insertion loss (IL) with limited back pressure, weight, size and cost. The unmuffled exhaust noise of an internal combustion engine peaks at the engine firing frequency and the first few harmonics thereof. Designing the muffler (a wide-band low pass acoustical filter) for such low frequencies is quite a challenge. Therefore, design of efficient mufflers has remained an art as well as science. During the last two decades or so, however, (a) multi-hole cross-flow perforates, (b) multiply connected perforated pipes and baffles, and (c) the double-tuned, grazing-flow concentric tube resonators have emerged as promising constituent elements. In this paper, elements (a) and (c) have been combined ingeniously to synthesize efficient muffler configuration for diesel generator (DG) sets as well as automotive engines. Relatively simpler lumped parameter approximation for perforates opening into cavities, electro-acoustic analogies, and the simple expansion chamber equivalence of the double-tuned concentric tube resonator have been used to develop a rational design methodology. A novel feature of this methodology is incorporation of the given back-pressure limit into the acoustic design process. The resulting muffler configurations are robust and can be scaled up (and down) easily for IL as well as back pressure.