Insertion Loss Of Muffler Research Articles

Research on Computational Data Simulation of Automobile Engine Exhaust Muffler Performance

In this paper, the transfer matrix method is used to simulate and calculate the insertion loss of muffler. This simulation method can evaluate the acoustic characteristics of the exhaust system. After deriving the transfer matrix of six kinds of silencing units, it is applied to the calculation of insertion loss. In this paper, a mathematical model of noise attenuation is established to analyze the relationship between the characteristics of muffler and acoustic attenuation. We can take the noise reduction as the objective function to optimize the muffler design. The mathematical model of pressure loss can be used to evaluate the aerodynamic performance of muffler.

Assessing the Effects of Impedance Modifications Using the Moebius Transformation

The Moebius transformation maps straight lines or circles in one complex domain into straight lines or circles in another. It has been observed that the equations relating acoustic or mechanical impedance modifications to responses under harmonic excitation are in the form of the Moebius transformation. Using the properties of the Moebius transformation, the impedance modification that will minimize the response at a particular frequency can be predicted provided that the modification is between two positions. To prove the utility of this method for acoustic and mechanical systems, it is demonstrated that the equations for calculation of transmission and insertion loss of mufflers, insertion loss of enclosures, and insertion loss of mounts are in the form of the Moebius transformation for impedance modifications. The method is demonstrated for enclosure insertion loss by adding a short duct in a partition introduced to an enclosure. In a similar manner, it is shown that the length or area of a bypass duct in a muffler can be tuned to maximize the transmission loss. In the final example, the insertion loss of an isolator system is improved at a particular frequency by adding mass to one side of the isolator.

Simulation and Optimization Design of Gasoline Engine Exhaust Muffler

The coupling simulation model of a gasoline engine’s working process and muffler is established by GT-Power software, and related data are obtained by simulation calculation. It is found that the calculating results are consistent with the actual data, which validates the correctness of this simulation model. Through the analysis processing of the coupling simulation model, it is put forward an improved case for the exhaust muffler in this paper. Based on a local optimization, the simulation results show that the insertion loss of muffler has improved markedly, the exhaust noise values decreased and indicated power engine remain basically unchanged.

IC-Engine Exhaust and Intake System Acoustic Source Characterization

The paper gives an overview of techniques used for characterization of IC-engines as acoustic sources of exhaust and intake system noise. Some recent advances regarding nonlinear source models are introduced and discussed. To calculate insertion loss of mufflers or the level of radiated sound information about the engine as an acoustic source is needed. The source model used in the low frequency plane wave range is often the linear time invariant one-port model. The acoustic source data is obtained from experimental tests or from 1-D CFD codes describing the engine gas exchange process. The IC-engine is a high level acoustic source and in most cases not completely linear. It is therefore of interest to have models taking weak non-linearity into account while still maintaining a simple method for interfacing the source model with a linear frequency domain model for the attached exhaust or intake system. The use of source characterization in acoustic design of mufflers is also briefly discussed.

Analysis and Improvement on Acoustic Performance of Muffler with the Consideration of Temperature and Flow Velocity

Aiming for the acoustic performance of expanded-muffler, the acoustic fields, flow field, temperature field and flow regenerated noise inside the expanded-muffler were studied. Furthermore, with the consideration of temperature and flow velocity, the influence of temperature and flow velocity on acoustic performance was obtained. Based on the research, the acoustic performance of an exhaust muffler was studied. By adjusting the structural parameters, without affecting the engine output power, the insertion loss of muffler has average increased by 5.1 dB (A).

Technical Note: Effects Due to Exhaust and Tail Pipes on Insertion Loss of Mufflers

(Submitted 28 September 2010; revised 13 August 2010; accepted 18 February 2011) In this study, the influence of exhaust pipe lengths on insertion loss(IL) which has not been analyzed in previous studies is investigated. IL is calculated analytically for a simple expansion chamber including source impedance, exhaust and tail pipe lengths. The prediction of frequencies based on models of quarter wave tube and half wave tube for exhaust and tail pipe resonances agree well with the effects seen in experimentally measured IL.

Modified multi-load method for nonlinear source characterisation

Linear frequency domain prediction codes are useful for calculation of low-frequency sound transmission in duct and pipe systems. To calculate insertion loss of mufflers or the level of radiated sound information about the acoustic source is needed. The source model used in the low-frequency plane wave range is the linear time invariant one-port model. The acoustic source data is usually obtained from experimental tests where multi-load methods and especially the two-load method are most commonly used. The exhaust pulsations of for example an IC-engine are of high level, and the engine is not a perfectly linear and time invariant source. It is therefore of interest to develop source models and experimental techniques that try to take this nonlinearity into account. In this paper a modified version of the two-load method to improve the characterisation of nonlinear acoustic one-port sources has been developed and tested. Simulation results as well as experimental data from various source configurations for a modified compressor and experimental data from 6-cylinder turbocharged truck diesel engine were used to validate the method. The influence of parameters controlling the linearity of the system was investigated. The time-variance of the source model was varied and the accuracy of source characterisation results using the two-load method and the modified two-load method was evaluated.