Exhaust Noise Research Articles

Analysis of Performance of Automotive Exhaust Muffler Based on ANSYS Finite Element

At present, the control of the automobile engine exhaust noise is mainly installed exhaust muffler. Muffler design and performance research mainly around the silencing performance and the influence to engine power loss. This article built the 3d modeling of automobile exhaust muffler and through simulation analysis obtained the muffler internal acoustic pressure distribution and changes of insertion loss with frequency. Predict the silencer muffler performance as well as the influence on engine power loss. Provide a reference basis for the design of the silencer and optimization. Compared to the traditional experiment method, the method in this article has the advantages of short cycle, low cost.

On the nonlinear and time-varying acoustic modeling of the simplified intake or exhaust silencing system

The intake or exhaust noise of an internal combustion engine is usually predicted by the linear, time-invariant source model in frequency domain with reasonable precision. However, the actual finite amplitude pulsation involves the nonlinear, time-varying characteristics that are prominent in time-domain. To overcome the discrepancy between two source models, an approximate nonlinear and time-varying frequency domain source model can be employed by appending the nonlinear or time-varying terms to the linear, time-invariant source model. Proper selection of the nonlinear describing terms varying with time is important for the realistic and precise prediction of the radiated sound. For the selection of such terms, flow and motional characteristics in the valve and orifice of a simplified fluid machine comprised of very large reservoir, valve, and duct is considered. Effects of each describing term and the combined terms are investigated by comparing the sound spectrum predicted from nonlinear source model to that from linear source model. In the comparison, the sound spectrum calculated by the method of characteristics is used as a reference. It is found that the source model using only the velocityrelated terms yields the best result among all the models using various combinations of the terms with different characteristics. The best model yields a difference from the linear source model within ±5 dB in overall sound level. Change of acoustic loads results in a difference of 20–27 dB in linear source model from the reference data; however, maximum 10–22 dB deviations are observed in using the various nonlinear source models. It is concluded that more than 4 describing terms should be employed in the nonlinear model to obtain a realistic result of the radiated sound from the intake or exhaust system.

Green logistic vehicle routing problem: Routing light delivery vehicles in urban areas using a neuro-fuzzy model

Today’s growth in the level of traffic in cities is leading to both congestion and environmental pollution (exhaust emissions and noise), as well as increased costs. Traffic congestion makes cities less pleasant places to live in, a particular problem being the negative impact on health as a result of increased exhaust emissions. In addition to these emissions, another major effect of transport which can lead to serious health problems is noise (EEA, 2013a, 2013b). There is a strong tendency in the world towards the development of “clean” motor vehicles that do not pollute the environment, that is, that do not emit harmful substances in their exhaust fumes and which create less noise without causing other types of pollution. The growth in the influence of transport on the environment has resulted in planners formulating procedures which take into account the effect of traffic on the quality of life in urban areas. This paper presents a model for the routing of light delivery vehicles by logistics operators. The model presented takes into account the fact that logistics operators have a limited number of environmentally friendly vehicles (EFV) available to them. When defining a route, EFV vehicles and environmentally unfriendly vehicles (EUV) are considered separately. For solving the problem of routing in the model, an adaptive neural network was used which was trained by a simulated annealing algorithm. An adaptive neural network was used for assessing the performance of the network branches. The input parameters of the neural network were the logistics operating costs and environmental parameters (exhaust emissions and noise) for the given vehicle route. Each of the input parameters of the neural network was thoroughly examined. The input parameters were broken down into elements which further describe the state of the environment, noise and logistics operating costs. After obtaining the performance of the network links for calculating the route for EFV and EUV vehicles a modified Clark–Wright algorithm was used. The proposed model was tested on a network which simulates the conditions in the very centre of Belgrade. All of the input parameters of the model were obtained on the basis of 40 automatic measuring stations for monitoring the air quality (SEA, 2012).

Design of a Muffler & Effect of Resonator length for 3 Cylinder SI Engine

An IC engine is a major source of noise pollution, where exhaust noise play major contribution. That is why the reduction of exhaust noise from engines is an important issue. A muffler in the exhaust pipe is used for reducing noise. Muffler requires specific design considering various noise parameters. In this the tunable resonator is used whose length can be varied by using a piston that can be set at different positions. Noise level is also measured at the different positions of resonator to check the effect of variation of length of silencer that shows the smaller the resonator size better is insertion loss. A muffler for stationary petrol engine (engine test rig) has been designed. Sound level is measured before and muffler installation at different position of resonator piston & the effect of resonator length is studied.

Current Research Trends in Sound Transmission Loss of Silencers

In recent years, the influence of automobile emissions and noise on the environment has become an increasingly serious problem. Particularly, exhaust system is known to be a predominant component of the automobile emissions and noise. Fortunately, over the last few decades, engine exhaust noise is controlled through the use of silencers or mufflers.The analysis of such complex mufflers has always been a great challenge and an active area of research in recent years. For a suitable design of mufflers, there are two main categories that are used to study this problem: the Transmission Loss (TL) and Insertion Loss (IL). Currently the transmission lossis preferred and widely used for determining muffler performance. This paper aims to present an updated review of papers, conference papers, books, dissertations dealing with muffler acoustics performance using transmission loss.

An adaptive quarter-wave tube that uses the sliding-Goertzel algorithm for estimation of phase

This paper describes an adaptive quarter wave tube used to attenuate a tone from the exhaust noise of a large diesel engine. A sliding-Goertzel algorithm was used to calculate the phase angle of the transfer function between a microphone in the adaptive quarter wave tube and in the main exhaust duct. The control system adjusted the length of the adaptive quarter wave tube until the phase angle was −90° and caused the sound pressure level at the cylinder firing frequency in the exhaust duct to be minimized. The system was able to adapt to changes in engine speed, exhaust gas temperature, and load applied to the engine. The results demonstrate that the sliding-Goertzel algorithm can be used effectively to estimate the phase angle in an adaptive–passive acoustic control system.

Acoustic Source Characterization for Prediction of Medium Speed Diesel Engine Exhaust Noise

To achieve reliable results when simulating the acoustics of the internal combustion engine (IC-engine) exhaust system and its components, the source characteristics of the engine must be known. In the low frequency range only plane waves propagate and then one-port source data can be determined using, for example, the acoustic multiload method. For the medium speed IC-engines used in power plants and ships, the exhaust duct noise often needs to be analyzed up to 10 kHz, i.e., far beyond the plane wave range, and it is then more appropriate to use acoustic power to characterize the source. This power should ideally be measured under reflection-free conditions in the exhaust duct. The results from an earlier study showed that a suitable way to characterize the source for any frequency is to determine the in-duct sound power by extending the plane wave formulation with frequency band power weighting factors. The aim of this study is to apply this high frequency range method in situ to a real test engine. Another aim is to define, theoretically, how to combine the source data in the low frequency plane wave range with those in the high frequency nonplane wave range using a source sound power formulation.

Theoretical and experimental study on underwater jet characteristics from a submerged combustion system

In this paper, an exhaust noise underwater is investigated experimentally and theoretically. The effects of high temperature and gas-water two-phase on underwater jet noise are analyzed. Results show that, higher exhaust gas temperatures generate louder jet noise underwater, including radiated noise from the tube orifice and bubble noise after detachment from orifice. But gas temperature has little effect on air-air jet noise. Another conclusion from experimental results is that injecting water into air-air jet system can effectively reduce jet noise but has less effect on air-water jet system. Turbulent dynamic noise, generated by air-air interaction, is the main noise source for air-air jet, but turbulent dynamic noise can be ignored in air-water jet considering gas-liquid density difference.And water droplet injected into air reduces the turbulent kinetic energy of the gas, therefor reduces the turbulent dynamic noise in air-air jet system.

Measurement of Noise inside the Compartment and Vibration on both Sides of Elastomeric Powertrain Mounts of Passenger Car

This paper presents an evaluation on elastomeric mount used to isolate vibration from powertrain to chassis or structure vehicle. The assessments started with measurement of noise inside compartment, and exhaust noise. This is followed by the measurement of vibration on both sides of elastomeric mounts. The noise in the compartment and exhaust noise is measured according to BS 6086: 1981 and BS ISO 5130: 2007. The noise in the compartment and vibration is tested in three conditions. Firstly, engine is run-up with load (driving at second gear); secondly, without load; and thirdly, without load but hanging. A microphone is fixed at the ear of the mannequin. The fast response and A weighting sound level meter were used for measurement noise in the compartment and exhaust noise. The vibration is measured in terms of acceleration on both sides of each elastomeric powertrain mounts. Two accelerometer transducers are fixed on both sides of powertrain elastomeric mounts. One side was identified as a source of vibration and the other as receiver of vibrations. The results showed that the pattern of overall vibration level on source and receiver increased from 1050 RPM (idling) to 4000 RPM on all test conditions. Vibration transmitted to chassis or receiver structure was analyzed using transmissibility concept. By evaluating test condition of engine run-up without load, informed that the front and rear mounts showed a high level transmissibility contributing to structure-borne noise.

Numerical Investigation of Lobe Structure on Performance of Lobed Forced Mixing Exhaust System

Geometric models of lobed mixer nozzle with different lobe shapes are created. The Reynolds Averaged Navier-Stokes (RANS) equations with standard k-e turbulence model are selected as controlling equations to simulate the corresponding flow field, and they are discretized by the Arbitrary Lagrange Euler method. The simulation results are compared with the splitter mixer nozzle, and the comparison outcomes indicate that lobed mixer can not only greatly increase the mixing between the core and fan flow, but also reduce the noise of exhaust. Besides, although energy loss of lobed mixer is bigger than splitter mixer, the difference of total pressure recovery coefficient and thrust coefficient between lobed mixer nozzle and splitter mixer nozzle is small. Among different lobe shape models, the straight cut and elliptical cut at the lobe exit can enhance the mixing, and their energy loss is slightly bigger than the corresponding model without cut. When the guide lines of lobed mixer is modified, thermal mixing efficiency declines, but the total pressure recovery coefficient increases. In addition, as lobe shape changes, although thrust coefficient varies, the difference between maximum and minimum thrust coefficient is less than 1%.

CABARET method on unstructured hexahedral grids for jet noise computation

A new scalable high-resolution CABARET MILES method coupled with a porous Ffowcs Williams–Hawking formulation for far-field noise modelling is applied for the computation of flow and noise from a high-speed turbulent jet, which corresponds to a converging axi-symmetric nozzle and static isothermal conditions of the Jet Exhaust Aerodynamics and Noise experiment. Computational simulation results are provided for a range of grid resolutions. The results for simple means, turbulent kinetic energy, and fourth-order velocity correlations are compared with the experimental data and with a reference LES-Smagorinsky calculation from the literature. Far-field-noise predictions are obtained based on several integral control surfaces, which are used for consistency of the model. The far-field noise spectra are also compared with the experiment. The directivity of the far field noise predicted is analysed with the Azimuthal Decomposition Technique and compared with jet noise data from the TsAGI experimental database.

Study on Internal Combustion Engine Exhaust Noise by Orthogonal Test

On type 380 diesel engine, orthogonal experimental studying on exhaust noise was carried out. This is to study the influence factors and degree on exhaust noise of internal combustion engine, and determine the main and secondary influence factors on diesel exhaust noise and their interaction. A noise prediction equations was established by studying the test samples based on genetic algorithm neural network. The results is very precise by test.

Study on Integrated System of SCR and Muffler for Heavy-Duty Diesel Vehicle

SCR (Selective Catalytic Reduction) is widely used as a good solution of reducing NOx emissions. For NOx emissions and exhaust noise for heavy-duty diesel vehicles, the paper studied the acoustic performance for the integrated system of SCR and muffler. By analyzing the action of the perforated pipe, the exhaust pressure loss and the impact on the performance of the integrated system, the integrated system was developed for heavy-duty diesel vehicles to solve the technical problem on the integration and performance optimization for the SCR system and muffler structure. Extrusion-type vanadium-based catalyst replaces the current coated-type catalysts, and improves the reduction efficiency. The two-stage rough and fine filter and the heating device for the urea pump are designed to increase the adaptability of the SCR system. The research shows that through the structural improvements, the exhaust noise is reduced by 28.5dB.

Radiated Noise Source Localization of Hydraulic Excavator Based on Wavelet Packet Analysis

Collect a hydraulic excavators radiated noise ten meters away under set conditions, and also the relevant noises near the excavator. Analyze noise signals with wavelet packet to get the main band of energy distribution. Then calculate the two signals correlation coefficient, which identifies the muffler exhaust noise and inlet noise as the main source for right rear radiated noise.

Analysis and Research of the Combustion Process of YN4100QB Diesel Engine

In order to obtain the foundation to the research on the Diesel Engine YN4100QB combustion process, exhaust, the optimal design of combustion chamber and the useful information for the design of exhaust muffler, the geometric model and mesh model of a type internal combustion engine are constructed by using FIRE software to analyze the working process of internal combustion engine. Exhaust noise is the main component of automobile noise in the study of controlling vehicle noise. It is primary to design a type of muffler which is good for agricultural automobile engine matching and noise reduction effect. The present car mufflers are all development means. So it is bound to cause the long cycle of product development and waste of resources. Even sometimes not only can it not reach the purpose of reducing the noise but also it leads to reduce the engine dynamic. The strength of the exhaust noise is closely related to engine combustion temperature and pressure. The calculation and initial parameters are applied to the software based on the combustion model and theory. According to the specific operation process of internal combustion engine. Five kinds of common operation condition was compiled. It is obtained for the detailed distribution parameters of combusted gas temperature pressure . It is also got for flow velocity of the fields in cylinder and given for the relation of the parameters and crankshaft angle for the further research. At the same time NOx emissions situation are got. The numerical results show that not only does it provide the 3D distribution data in different crank shaft angle inside the cylinder in the simulation of combustion process, but also it provides a basis for the engine combustion ,emission research, the optimization design of the combustion chamber and the useful information for the designs of muffler.

Research on Noise Control of Wheel Loader and Frequency Spectrum Analysis

The tested wheel loader machinery noise was 110dB and driver position was 108dB, more than Chinese earth-moving machinery standard. Engine noise is the main noise, so thirty-five test points were arranged around the cab and engine to analyze and find the main noise points. The frequency spectrogram show that the main frequency band for the engine and exterior cab are 120Hz and 216Hz, and the interior cab noise was caused by the vibration of the power train passed through the frame result in resonance. Analyzed and calculated the main frequency concludes that the main noise resources are engine exhaust noise and cooling fan noise. To decrease the noise, proper damping materials were affixed to the engine hood and interior cab, the metal pieces were tightened and the cooling fan and shock absorber were replaced with new ones that match the main noise frequency.

대향류식 배기열 회수장치의 가솔린기관 적용 특성에 관한 연구

Abstract : The purpose of this study is to investigate the performance characteristics of the counterflow exhaust heat recovery device for the applied gasoline engines. The EHRS device is installed behind the catalyst. This study investigates the engine warm-up characteristic, the exhaust noise characteristic, the back-pressure characteristic . The engine warm-up characteristics is (load 0%, load 10%, load 20%) in (idle, 1000rpm, 1500rpm, 2000rpm, 2500rpm) conditions by measuring the time it warmed up, coolant temperature (25°C~80°C) until the performance evaluation is performed. The wide open throttle and the coast down the exhaust noise and the back-pressure characteristic experiment repeated twice. The test conditions is 950rpm~6,050rpm proceed experiment repeated 3-5 times. Load 0% idle conditions except the results improved engine warm-up characteristics. The exhaust noise obtain similar results the BASE+EHRS W/O_FRT_MUFF with BASE and back-pressure to obtain similar results BASE+EHRS W/O_FRT_ MUFF with BASE+EHRS.

Aerodynamics and Stealth of the Low-observability RQ-3 DarkStar

Marques P. (2013). Aerodynamics and stealth of the low- observability DarkStar vehicle. International Journal of Unmanned Systems Engineering. 1(S3): 1-5. The RQ-3 DarkStar high-altitude endurance UAV has an unusual shape that represents a compromise between aerodynamic efficiency and stealth constraints for low detectability in heavily guarded airspace. This technical note examines the aerodynamic and stealth characteristics of the rare RQ-3 DarkStar configuration. The distinctive flying-saucer fuselage and slightly-forward-swept rectangular wings present a challenge in aerodynamic design. The vehicle's lifting body sheds a leading edge vortex that triggers flow separation in the wing root region at high angles of attack. Also, the disk-shaped body generates upwash in the inboard wing area, increasing the angle of attack and the likelihood of flow separation. CFD played an integral role in the rapid prototyping environment in which the DarkStar was designed, built, and fight- tested. A wing root insert was devised using CFD that decreased the lift generated by the body, and attenuated the strength of the leading edge vortex and flow separation. Therefore, CFD was essential in diagnosing the complex aerodynamics and preventing the pitch up tendency of the initial DarkStar prototype. The turbo engine is mounted above the fuselage to shield the compressor and exhaust noise and heat signatures. The small size and low-profile airframe of the DarkStar is the result of shaping for radar concealment at the expense of downgraded aerodynamic performance. © Marques Aviation Ltd - Press.

Noise Reduction of Single Cylinder Diesel Engine Based on Virtual Prototype

Based on the one-dimensional and unsteady flow theory of gas dynamics and acoustic analysis method, a thermodynamics and acoustics model of single cylinder diesel engine was established, then the model was realized using GT-Power. A method combined with mechanic analysis and acoustic prediction was presented. With this method, the influence of compression ratio, inlet and outlet channels, intake valve and exhaust valve timing on engine exciting force and noise is analyzed. Then the optimization value of each factor is determined to improve the muffler. The intake and exhaust noise of the optimized engine is simulated with this model, the simulating results indicated that the exhaust noise reduces 2.6~3dB, and the intake noise reduces 1.1~1.4dB.

Acoustic Performance of Exhaust Muffler Based Genetic Algorithms and Artificial Neural Network

The noise level wa s one of the important indicators as a measure of the quality and performance of the diesel engine.Exhaust noise in diesel engines machine accounted for an important proportion of installed performance exhaust muffler and it w as an effective way to control exhaust noise. This article using orthogonal test program for the muffler structure parameters as input to the sound pressure level and diesel fuel each output artificial neural network (BP network) learning sample. Matlab artificial neural network toolbox to complete the training of the network, and better noise performance and fuel consumption rate performance muffler internal structure parameters combination was obtained through genetic algorithm gifted collaborative validation of artificial neural networks and genetic algorithms to optimize application exhaust muffler design is entirely feasible.