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Viewing 1 to 30 of 43119
2011-05-17
Technical Paper
2011-01-1621
Frank Friedrich
While the microcellular urethane is widely known in the automotive industry for its use in jounce bumpers, its use in Noise Vibration Harshness (NVH) applications is often not as well recognized. Even though there are some NVH parts in the market, rubber still dominates it. The objective of this paper is to demonstrate the material properties of MCU and their relevance for NVH applications in chassis and suspension components. It will also demonstrate the importance of package design to suit the use of the MCU material. This is especially important to not only achieve the best performance but also keep overall cost and weight under control. Several application types will be introduced with general design suggestions. A detailed design guideline for these applications is not part of this paper. Each application has a large variety of parameters to be considered in the design. They need to be selectively applied based on customer performance targets.
2011-05-17
Technical Paper
2011-01-1623
Alan V. Parrett, Chong Wang, Xiandi Zeng, David Nielubowicz, Mark Snowden, Jonathon H. Alexander, Ronald Gerdes, Bill Leeder, Charles Zupan
In recent years several variants of lightweight multi-layered acoustic treatments have been used successfully in vehicles to replace conventional barrier-decoupler interior dash mats. The principle involved is to utilize increased acoustic absorption to offset the decrease in insertion loss from the reduced mass such that equivalent vehicle level performance can be achieved. Typical dual density fibrous constructions consist of a relatively dense cap layer on top of a lofted layer. The density and flow resistivity of these layers are tuned to optimize a balance of insertion loss and absorption performance. Generally these have been found to be very effective with the exception of dash mats with very high insertion loss requirements. This paper describes an alternative treatment which consists of a micro-perforated film top layer and fibrous decoupler layer.
2011-05-17
Technical Paper
2011-01-1619
Shi Zheng, Chris Kleinfeld
This paper presents a hybrid method that predicts the whistle occurrence of an automotive exhaust tuning device. The method utilizes inputs from a limited amount of test work or numerical simulation to predict the whistle occurrence in a wider range of flow conditions (temperature and velocity). It has the advantages of being quick and low cost compared with extensive tests or the computational fluid dynamics approach.
2011-05-17
Technical Paper
2011-01-1628
Hejie Lin, Turgay Bengisu, Zissimos Mourelatos
Styrene-Butadiene Rubber (SBR), a copolymer of butadiene and styrene, is widely used in the automotive industry due to its high durability and resistance to abrasion, oils and oxidation. Some of the common applications include tires, vibration isolators, and gaskets, among others. This paper characterizes the dynamic behavior of SBR and discusses the suitability of a visco-elastic model of elastomers, known as the Kelvin model, from a mathematical and physical point of view. An optimization algorithm is used to estimate the parameters of the Kelvin model. The resulting model was shown to produce reasonable approximations of measured dynamic stiffness. The model was also used to calculate the self heating of the elastomer due to energy dissipation by the viscous damping components in the model. Developing such a predictive capability is essential in understanding the dynamic behavior of elastomers considering that their dynamic stiffness can in general depend on temperature.
2011-05-17
Technical Paper
2011-01-1629
Saurabh Suresh, Jeff Kastner, Teik Lim
Reduction of noise transmitted through laminated glass with interlayer is of interest to vehicle applications. Altering the structure of the interlayer can impact sound transmission loss particularly at the coincidence frequency. This study investigates the feasibility of including a porous layer within the laminated glass to act as an acoustic damper. To understand the underlying physics controlling transmission loss in laminated glass design, an approach utilizing transfer matrices is used for modeling each layer in the laminated glass. These transfer matrices are used to relate the acoustic characteristics of two points within a layer. For any two layers in contact, an interface matrix is defined that relates the acoustic fields of the layers depending on their individual characteristics. The solid layer is modeled as an elastic element and the sound propagation through the porous materials is described using the Biot theory.
2011-05-17
Technical Paper
2011-01-1632
Ion Pelinescu, Andrew Christie
One of the most effective NVH solutions used in the automotive industry to reduce structure-borne noise is to apply vibration damping treatments to the vehicle structure. These damping treatments need to meet increasing weight reduction targets, while offering the same or better damping properties. While Liquid Applied Structural Dampers (LASD) are now delivering high damping performance at lower densities, traditional damping measuring techniques are falling short in describing the performance of these extensional layers when applied onto more realistic test samples or real structures. This paper discusses the damping performance of LASD technology, in particular the newer generations of acrylic-based waterborne LASD materials, which through improvements in polymer architecture are achieving increased damping efficiencies together with reduced density.
2011-05-17
Technical Paper
2011-01-1624
Prasanth B, Sachin Wagh, David Hudson
Baffle plates with heat reactive expandable foam sealants have increasingly found their applications in automotives. They are used to separate body cavities and to impede noise, water and dust propagation inside of body cavities, thus control noise intrusion into the passenger compartment. Use of these sealant materials has grown significantly as the demands to improve vehicle acoustic performance has increased. Traditionally quantification of the acoustic performance of expandable baffle samples involved making separate vehicles with and without expandable baffles and measure the incab noise to know the effect. The absolute acoustic evaluation of the baffles is very difficult as number of other vehicle parameters is also responsible for vehicle incab noise. Also, it is a time consuming and a costly method to evaluate.
2011-05-17
Technical Paper
2011-01-1625
John G. Cherng, Qian Xi, Pravansu Mohanty, Gordon Ebbitt
Acoustical materials are widely used in automotive vehicles and other industrial applications. Two important parameters namely Sound Transmission Loss (STL) and absorption coefficient are commonly used to evaluate the acoustical performance of these materials. Other parameters, such as insertion loss, noise reduction, and loss factors are also used to judge their performance depending on the application of these materials. A systematic comparative study of STL and absorption coefficient was conducted on various porous acoustical materials. Several dozen materials including needled cotton fiber (shoddy) and foam materials with or without barrier/scrim were investigated. The results of STL and absorption coefficient are presented and compared. As expected, it was found that most of materials are either good in STL or good in absorption. However, some combinations can achieve a balance of performance in both categories.
2011-05-17
Technical Paper
2011-01-1626
Jonathan Alexander, David Reed, Ronald Gerdes
Flat, constant thickness composites that consisted of a microperforated top layer plus a fibrous decoupler layer were tested for random absorption and transmission loss (TL) performance. The top, microperforated layer consisted of a relatively thick film that contained small, precise micro-perforations. For reference, top layers that consisted of a resistive scrim and an impervious film were also included in this study. Two fibrous materials of constant thickness were used for the decoupler layer between a steel panel and the top microperforated film. The composites' absorption and TL performance were also modeled using the well-known transfer matrix method. This method has been implemented in a commercially available statistical energy analysis (SEA) software package. A comparison of testing and modeling results showed reasonable agreement for absorption results and even better agreement for transmission loss and insertion loss results.
2011-05-17
Journal Article
2011-01-1627
J. Liu, D. W. Herrin
Microperforated panel (MPP) absorbers are rugged, non-combustible, and do not deteriorate over time. That being the case, they are especially suitable for long term use in harsh environments. However, the acoustic performance is modified when contaminated by dust, dirt, or fluids (i.e. oil, water). This paper examines that effect experimentally and correlates the absorption performance with Maa's theory for micro-perforated panels. Transfer impedance and absorption coefficient are measured for different levels of aluminum oxide and carbon dust accumulation. The amount of dust contamination is quantified by measuring the luminance difference between clean and dirty panels with a light meter. The porosity and hole diameter in Maa's equation are modified to account for dust obstruction. The effect of coating the MPP with oil, water, and other appropriate viscous fluids was also measured. This effect was simulated by modifying the viscous factor in Maa's equation.
2011-05-17
Technical Paper
2011-01-1639
Jan Krueger, Michael Pommerer, Tom Frei
In the past years Eberspaecher has installed Active Exhaust Silencers on several passenger vehicles with different diesel and gasoline engines on a prototype level. Meanwhile, a substantial reduction of the exhaust noise is regularly achieved in a broad frequency range covering all relevant engine orders. Due to the higher acoustic excitation and higher exhaust temperatures in gasoline engines it is more difficult to implement the ANC-technology on those engines. However, results from roller test benches focus on the acoustic performance as well as weight and volume reductions and demonstrate a marked improvement which was achieved with gasoline engines too. Further progress was made in the development of the durability and industrialization of all relevant components of the system. Finally, current design trends and possible fields of application will be discussed.
2011-05-17
Technical Paper
2011-01-1634
Michael Dinsmore, Richard Bliton, Scott Perz
Using advanced, multi-layer poro-elastic acoustical material modeling technologies, an example of acoustical performance optimization of an underhood sound absorber application is presented. In this case, a porous facing in combination with a fibrous sound absorber pad is optimized for maximum efficiency, which allows for dramatic reduction in pad density and weight. Overall sound absorption performance is shown to be equal or improved versus frequency relative to the incumbent design.
2011-05-17
Technical Paper
2011-01-1637
Ahad Khezerloo, Amin owhadi Esfahani PhD, Sina Jalily lng
One of important problems in railway transportation systems is control of noise and vibration. Metal foams are very good medias for absorbing noise. So in this paper, noise of motion of a train is simulated by MATLAB software and the reduction of noise level in a compartment of passenger car that is equipped by metal foam sheets is considered. Commonly, the sound absorption coefficients are obtained experimentally and they are available in datasheets and references. The different parameters that influence on the capability of this equipment were considered. For example the microstructure, thickness, magnitude of compaction, relative density and etc of metal foam is effective parameters. High porosity has good effect on the performance of absorber sheet. By increasing of compaction ratio, in frequency domain we will have enhancing of absorption of the noise. Compaction process is done by two different ways: one is direct and else is progressively.
2011-05-17
Technical Paper
2011-01-1564
Tony Karlsson, Ragnar Glav
Simulation using basic acoustic 2-port elements is a time effective method for prediction of the attenuation of single components as well as of complete exhaust aftertreatment and silencer systems. However, with the complexity of current systems, the transformation from design geometries to networks of basic elements is not straightforward. In this paper a practical example of the modelling of a modern exhaust aftertreatment system is presented. A silencer aimed at the Euro 6 heavy duty emissions legislation containing complex flow turnings, parallel branches, DOC (Diesel Oxidation Catalyst), DPF (Diesel Particulate Filter) and SCR (Selective Catalytic Reduction) catalysts was modelled. Evaluation against measurements in order to understand the influence of the different acoustic elements upon overall attenuation and to improve the model with respect to near field and higher order mode effects was done.
2011-05-17
Journal Article
2011-01-1562
Tamer Elnady, Sara Elsaadany, D. W. Herrin
Diesel engines produce harmful exhaust emissions and high exhaust noise levels. One way of mitigating both exhaust emissions and noise is via the use of after treatment devices such as Catalytic Converters (CC), Selective Catalytic Reducers (SCR), Diesel Oxidation Catalysts (DOC), and Diesel Particulate Filters (DPF). The objective of this investigation is to characterize and simulate the acoustic performance of different types of filters so that maximum benefit can be achieved. A number of after treatment device configurations for trucks were selected and measured. A measurement campaign was conducted to characterize the two-port transfer matrix of these devices. The simulation was performed using the two-port theory where the two-port models are limited to the plane wave range in the filter cavity.
2011-05-17
Journal Article
2011-01-1575
John David Fieldhouse, David Bryant, Chris John Talbot
Thermo-elastic and thermo-plastic behaviour takes place with a disc brake during heavy braking and it is this aspect of braking that this paper considers. The work is concerned with working towards developing design advice that provides uniform heating of the disc, and equally important, even dissipation of heat from the disc blade. The material presented emanates from a combination of modeling, on-vehicle testing but mainly laboratory observations and subsequent investigations. The experimental work makes use of a purpose built high speed brake dynamometer which incorporates the full vehicle suspension for controlled simulation of the brake and vehicle operating conditions. Advanced instrumentation allows dynamic measurement of brake pressure fluctuations, disc surface temperature and discrete vibration measurements.
2011-05-17
Technical Paper
2011-01-1601
Abolfazl Eskandari, Mostafa haghroosta, Kia Valefi
One of the most important factors that must be taken into account during vehicle design is the quality of noise and vibration produced by the vehicle. This is evident from manufacturer's attempt to produce quieter product. On the other hand, some of the vehicles have not good NVH properties and must be modified in order to be successful in the market. In this type of vehicles, no basic changes can be made, and focus must be on restricted improvements. In this research, a vehicle of this kind is selected and measures have been taken to improve its noise and vibration behavior. By implementing suspension techniques, some of the vibration characteristics of drive train and its influence on the interior noise at different engine speeds and under road load have been investigated. In addition, the effect of double layer instead of single layer muffler skin on the cabin noise has been probed.
2011-05-17
Technical Paper
2011-01-1528
Deepak Rana, Felix Regin, Mohan Makana
A muffler or silencer is an integral part of the exhaust system and is a device used to prevent sound from reaching the openings of the exhaust duct and radiating as far field noise. Different acoustical design and analysis techniques are used to predict the acoustical performance of exhaust systems. Flow noise from exhaust tail pipe is one of the major noise sources in a vehicle. Flow noise is generated mainly during fast acceleration operating condition due to complex flow behavior. In this paper, we have studied the detailed flow field and tried to establish an analyses procedure for flow noise prediction. The flow analysis is carried out in commercial CFD solver Star CCM+. The transient engine boundary conditions are obtained from the experimental testing. The flow noise generated from the muffler was calculated by acoustic analogy of Lighthill using the above boundary conditions.
2011-05-17
Journal Article
2011-01-1529
Zhenlin Ji, Zhi Fang
The one-dimensional analytical approach, three-dimensional finite element method (FEM) and boundary element method (BEM) are developed to predict and analyze the acoustic attenuation performance of three-pass perforated tube muffler with end-resonator. For an elliptical muffler, the predictions of transmission loss from the FEM and BEM agree well each other throughout the frequency range of interest, while the one-dimensional analytical solution shows a reasonable agreement with the numerical predictions at lower frequencies and deviates at higher frequencies. The FEM is then used to investigate the effects of geometrical parameters and internal structure on the acoustic attenuation performance of three-pass perforated tube muffler with end-resonator.
2011-05-17
Technical Paper
2011-01-1559
X. Hua, J. Liu, D. W. Herrin, T. Elnady
This paper documents a finite element approach to predict the attenuation of muffler and silencer systems that incorporate diesel particulate filters (DPF). Two finite element models were developed. The first is a micro FEM model, where a subset of channels is modeled and transmission matrices are determined in a manner consistent with prior published work by Allam and Åbom. Flow effects are considered at the inlet and outlet to the DPF as well as viscous effects in the channels themselves. The results are then used in a macro FEM model of the exhaust system where the transmission relationship from the micro-model is used to simulate the DPF. The modeling approach was validated experimentally on an example in which the plane wave cutoff frequency was exceeded in the chambers upstream and downstream to the DPF.
2011-04-12
Journal Article
2011-01-1401
Yoolkoo Kim, Hyundal Park, Jeong Uk An, Tae-Suek Kan, Joonsung Park
Various polymer-based coatings are applied on piston skirt to reduce friction loss between the piston skirt and cylinder bore which is one of main factors of energy loss in an automotive engine system. These coatings generally consist of polymer binder (PAI) and solid lubricants (graphite or MoS₂) for low friction property. On the other hand, the present study found that PTFE as a solid lubricant and nano diamond as hard particles can be used to improve the low friction and wear resistance simultaneously. In the process of producing coating material, diamond particles pulverized to a nano size tend to agglomerate. To prevent this, silane (silicon coupling agent) treatment was applied. The inorganic functional groups of silane are attached to the nano diamond surface, which keep the diamond particles are apart.
2011-04-12
Technical Paper
2011-01-1413
Akira Yamashita, Hisashi Ohki, Terutoshi Tomoda, Koichiro Nakatani
Low pressure loop (LPL) EGR systems are effective means of simultaneously reducing the NOx emissions and fuel consumption of diesel engines. Further lower emission levels can be achieved by adopting a system that combines LPL EGR with a NOx storage and reduction (NSR) catalyst. However, this combined system has to overcome the issue of combustion fluctuations resulting from changes in the air-fuel ratio due to EGR gas recirculation from either NOx reduction control or diesel particulate filter (DPF) regeneration. The aim of this research was to reduce combustion fluctuations by developing LPL EGR control logic. In order to control the combustion fluctuations caused by LPL EGR, it is necessary to estimate the recirculation time. First, recirculation delay was investigated. It was found that recirculation delay becomes longer when the LPL EGR flow rate or engine speed is low.
2011-05-17
Journal Article
2011-01-1517
Robert E. Powell, Dena Hendriana, Brian Gutzeit, Kevin Golsch, Gregory Fadler
Unusual noises during vehicle acceleration often reflect poorly on customer perception of product quality and must be removed in the product development process. Flow simulation can be a valuable tool in identifying root causes of exhaust noises created due to tailpipe openings surrounded by fascia structure. This paper describes a case study where an unsteady Computational Fluid Dynamics (CFD) simulation of the combined flow and acoustic radiation from an exhaust opening through fascia components provided valuable insight into the cause of an annoying flow noise. Simulation results from a coupled thermal/acoustic analysis of detailed tailpipe opening geometry were first validated with off-axis microphone spectra under wide open throttle acceleration. After studying the visualizations of unsteady flow velocity and pressure from the CFD, a problem that had proved difficult to solve by traditional “cut and try” methods was corrected rapidly.
2011-05-17
Technical Paper
2011-01-1724
Juliette Florentin, Francois Durieux, Yukihisa Kuriyama, Toyoki Yamamoto
The present work attempts a complete noise and vibration analysis for an electric vehicle at concept stage. The candidate vehicle is the Future Steel Vehicle (FSV), a lightweight steel body with an electric motor developed by WorldAutoSteel [1,2,3]. Measurements were conducted on two small Mitsubishi vehicles that both share the same body, yet one is equipped with an internal combustion engine and the other with an electric motor. The outcome was used as a starting point to identify assets and pitfalls of electric motor noise and draw a set of Noise Vibration and Harshness (NVH) targets for FSV. Compared to a combustion engine, the electric motor shows significantly lower sound pressure levels, except for an isolated high frequency peak heard at high speeds (3500 Hz when the vehicle drives at top speed). The prominence of this peak is lowered by increased use of acoustic absorbent materials in the motor compartment.
2011-05-17
Journal Article
2011-01-1693
Luca Guj, Theophane Courtois, Claudio Bertolini
Typically, in the automotive industry, the design of the body damping treatment package with respect to NVH targets is carried out in such a way to achieve panel mobility targets, within given weight and cost constraints. Vibration mobility reduction can be efficiently achieved thanks to dedicated CAE FE tools, which can take into account the properties of damping composites, and also, which can provide their optimal location on the body structure, for a minimal added mass and a maximized efficiency. This need has led to the development of different numerical design and optimization strategies, all based on the modeling of the damping composites by mean of equivalent shell representations, which is a versatile solution for the full vehicle simulation with various damping layouts.
2011-05-17
Technical Paper
2011-01-1710
Diego d'Udekem, Masatake Saitoh, Benoit Van den Nieuwenhof, Takashi Yamamoto
During the acceleration of a vehicle, the contribution of the exhaust noise to the interior sound pressure level is significant. The acoustic insulation brought by the trim components must be designed with that consideration in mind. As such, there is an increasing need for developing reliable methods for predicting the airborne noise transmission between the exhaust system and the sound pressure level at the passenger's ears, taking into account the positive impact of various trim components. This paper presents a methodology that has been developed for addressing this need. Based on a finite/infinite element method, the computational procedure is divided in two steps: 1 The first step involves the exterior acoustic field all around the vehicle.
2011-08-30
Technical Paper
2011-01-2094
Boonlue Sawatmongkhon, Athanasios Tsolakis, Andrew P. E. York, Kampanart Theinnoi
Computational Fluid Dynamics (CFD) is used to simulate chemical reactions and transport phenomena occurring in a single channel of a honeycomb-type automotive catalytic converter under lean burn combustion. Microkinetic analysis is adopted to develop a detailed elementary reaction mechanism for propane oxidation on a silver catalyst. Activation energies are calculated based on the theory of the Unity Bond Index-Quadratic Exponential Potential (UBI-QEP) method. The order-of-magnitude of the pre-exponential factors is obtained from Transition State Theory (TST). Sensitivity analysis is applied to identify the important elementary steps and refine the pre-exponential factors of these reactions. These pre-exponential factors depend on inlet temperatures and propane concentration; therefore optimised pre-exponential factors are written in polynomial forms. The results of numerical simulations are validated by comparison with experimental data.
2011-08-30
Technical Paper
2011-01-2095
Georg Huthwohl, Sascha Dolenec
SCR technology is becoming more and more important for the segment of diesel-driven passenger cars. Due to space and functional demands the dependency of SCR performance on a uniform supply of ammonia into the catalytic substrates is highly increased. Both an even distribution of the AdBlue® spray and a completed evaporation and decomposition of the droplets are the key to achieve the desired ammonia spread. Evaluation of the influence of spray quality on the AdBlue® decomposition and catalyst performance are leading to a new approach in dosing, using a special nozzle and air-supply strategy. The resulting new technology is evaluated and compared to the state of the art.
2011-08-30
Technical Paper
2011-01-2096
Aaro Kopperoinen, Matti Kyto, Seppo Mikkonen
When a new type of fuel is introduced, it is necessary to ensure that exhaust gas aftertreatment systems work properly with these fuels. Today diesel particulate filter (DPF) is an inherent part of current diesel engine's exhaust gas aftertreatment system due to stringent exhaust emission limits. The functioning of DPF depends on the composition of soot particulates of exhaust gas, whereas the type of soot depends on the fuel used. To avoid clogging, DPF has to be regenerated regularly. This regeneration is usually increasing fuel consumption, so the longer the regeneration interval is, the better is fuel economy. Fuel quality and engine-out particulate emissions are important factors affecting to the need of regeneration. Renewable fuels burn cleanly and produce less particulate emissions than ordinary diesel fuel. Therefore, the increase of exhaust backpressure is slower enabling longer regeneration frequency.
2011-08-30
Journal Article
2011-01-2089
Yuki Bisaiji, Kohei Yoshida, Mikio Inoue, Kazuhiro Umemoto, Takao Fukuma
An unprecedented phenomenon that achieves high NOx conversion was found over an NSR catalyst. This phenomenon occurs when continuous short cycle injections of hydrocarbons (HCs) are supplied at a predetermined concentration in lean conditions. Furthermore, this phenomenon has a wider range of applicability for different catalyst temperatures (up to 800 degrees Celsius) and SVs, and for extending thermal and sulfur durability than a conventional NOx storage and reduction system. This paper analyzes the reaction mechanism and concludes it to be highly active HC-deNOx by intermediates generated from adsorbed NOx over the base catalysts and HCs partially oxidized by oscillated HC injection. Subsequently, a high performance deNOx system named Di-Air (diesel NOx aftertreatment by adsorbed intermediate reductants) was demonstrated that applies this concept to high speed driving cycles.
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