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Viewing 1 to 30 of 101161
Technical Paper
2015-05-09
Kazumoto Morita, Michiaki Sekine
The number of elderly drivers is increasing in Japan and ensuring the safety of elderly drivers is becoming an important issue. The authors previously conducted an analysis of the characteristics of accidents and traffic violations by elderly drivers based on the number of accidents in which they were rear-ended. This method was used in order to exclude the influence of driving frequency. As a result of that analysis, it was found that the likelihood of violations committed by elderly drivers was not particularly higher than in other age groups, while the likelihood of accidents caused by them was higher. The risk of causing an accident was judged to be about two times higher in elderly drivers than in the 35–44 year age group. However, the methodology presupposed that collisions in which a driver is rear-ended are accidents that occur haphazardly, and that they occur with the same probability in each age group. To verify the results of that study, we attempted a new analytical method that uses the number of stop sign violations, which are considered to occur with the same probability among age groups, as an indicator of driving frequency in place of rear-ended collisions.
Technical Paper
2014-09-16
Zachary A. Collier, Steve Walters, Dan DiMase, Jeffrey M. Keisler, Igor Linkov
Counterfeit electronic components entering into critical infrastructure and applications through the global supply chain threaten the economy and national security. In response to the growing threat from counterfeits, the Society of Automotive Engineers G-19 Committee is developing AS6171. This aerospace standard is focused on testing facilities with a goal of standardizing the process of counterfeit detection. An integral part of the standard is a semi-quantitative risk assessment method. This method assigns risk scores to electronic components based on a number of relevant criteria, and places the components into one of five risk tier levels corresponding to an appropriate level of laboratory testing to ensure the authenticity of the component. In this way, the methodology aims at standardizing the risk assessment process and bases the identified risk as guidance for commensurate testing protocols. This paper outlines the risk assessment method contained within AS6171 and briefly explores other complementary efforts and research gaps within the G-19 and electronics community.
Technical Paper
2014-09-15
Kai Chen
The synthetic paraffinic kerosine (SPK) produced via HEFAs is of great interest for civil aviation industry as it exhibits an excellent thermal oxidative stability with significantly lower particulate matter emission. However, due to its aromatic free characteristics, the widespread use of SPK is limited by its compatibility with non-metal materials such as fuel tank elastomers. In this research the compatibility of SPK and its blends with widely used aircraft fuel tank elastomers were systematically studied. Experimental results demonstrated the volume swellability of all selected materials showed a linear relationship with volume percentage of No.3 jet fuel in SPK blend. The increase of volume percentage of No.3 jet fuel in the SPK blend increased volume swellability for all materials except fluorosilicone gasket. The alkyl benzenes and naphthalenes in the blend acted as the hydrogen donors, which facilitated the formation of polymer matrix and led to the increase of the distance between polymer chains.
Technical Paper
2014-06-30
Koen Vansant, Hadrien Bériot PhD, Claudio Bertolini, Giuseppe Miccoli
As the legislation for pass-by-noise (PBN) has recently become more stringent, it is clear that car manufacturers face again a challenging task to reach the new SPL objective (70dB(A)). Following the well-known scheme of source-transmission-receiver, we can see how a good design of the engine bay is required to sufficiently attenuate the noise coming from sources as the engine and the intake. This involves proper design of the engine bay’s panels including apertures, and a good selection of the type and location of acoustic treatments. Such optimization or redesign can be inspired by a new target SPL, but can also be initiated by a change in source: the radiated noise from an electric motor differs from that of a conventional IC engine. For a given engine bay design, the PBN SPL results can be obtained with a PBN test or by an equivalent simulation. The conditions for a good PBN test setup are well described but not always easy to obtain. Using simulation models however it is possible to create the perfect test environment virtually and moreover to obtain acoustic results for a large number of designs upfront of any actual testing or prototype.
Technical Paper
2014-06-30
Albert Albers, Jan Fischer, David Landes, Matthias Behrendt
Albert Albers 1, *Jan Fischer 1, David Landes 1, Matthias Behrendt 1 1 IPEK - Institut für Produktentwicklung am Karlsruher Institut für Technologie (KIT) * Contact author: Kaiserstr. 10, 76131 Karlsruhe; jan.fischer@kit.edu The driving comfort is an important factor for buying decisions. Especially for battery electric vehicles (BEV) the acoustic quality is an elementary distinguishing feature, since the masking of an internal combustion engine (ICE) is no longer present. Opposing the importance of the acoustic quality is the lack of knowledge of how to measure and interpret the high frequency noise generated by an electric powertrain with respect to the NVH behavior influencing the passengers [1, 2]. In this contribution a method for measuring and interpreting the transfer path of acoustic phenomena from the drivetrain of a battery electric vehicle into the passenger cabin is presented. Due to the lack of masking by the ICE in case of BEV, high frequency phenomena must be considered as well.
Technical Paper
2014-06-30
Ze Zhou, Jonathan Jacqmot, Gai Vo Thi, ChanHee Jeong, Kang-Duck Ih
Abstract: The NVH study of trimmed vehicle body is essential in improving the passenger comfort and optimizing the vehicle weight. Efficient modal finite-element approaches are widely used in the automotive industry for investigating the frequency response of large vibro-acoustic systems involving a body structure coupled to an acoustic cavity. In order to accurately account for the localized and frequency-dependant damping mechanism of the trim components, a direct physical approach is however preferred. Thus, a hybrid modal-physical approach combines both efficiency and accuracy for large trimmed body analysis. Dynamic loads and exterior acoustic loads can then be applied on the trimmed body model in order to evaluate the transfer functions between these loads and the acoustic response in the car compartment. The scenario study of installing different trim components into the vehicle provides information on the acoustic absorption and dynamic damping with regard to added vehicle weight by the trim.
Technical Paper
2014-06-30
Hiromichi Tsuji, Kimihiko Nakano PhD
In the early stage of digital phase and prototype experimental phase, the identification of the operational force on the components and the most important paths of the vibration correlated to the one of the evaluation points, such as steering, seats, and passenger ears, is required for optimizing the dynamic characteristics of the subsystem components of the vehicle. The transfer path analysis (TPA) with the impedance matrix of the component joints is widely used and reliable method to identify the force and the paths of the noise and vibration. However, the conduction of this TPA costs a lot of times. In addition, the estimated force includes not contributing to the evaluation responses. The uncorrelated force to the evaluation responses causes the design errors of the dynamic characteristics in the digital development phase when it has high value at the certain frequency range. To solve the problems, a new force estimation technique is presented in this paper. The proposed technique is based on TPA with the impedance matrix in the frequency domain.
Technical Paper
2014-06-30
Ennes Sarradj, Thomas Geyer, Christoph Jobusch, Sebastian Kießling, Alexander Neefe
The development of energy-efficient and lightweight vehicles is a major challenge for researchers and engineers in the automotive industry, with one solution being the use of micro gas turbines in serial hybrid vehicles. Among other advantages, the use of a micro gas turbine instead of a reciprocating engine, enables a high reliability and low emissions. What makes the concept of using a gas turbine even more interesting are its special NVH characteristics, which are quite different from those of a reciprocating engine. Besides the fact that a gas turbine in general produces less noise and vibration than a diesel engine of the same power, the characteristic noise spectrum is also very different. In this paper, the noise characteristics of a micro gas turbine are compared to those typical for a common reciprocating engine and the sources of the noise are considered. The data that form the basis for these analyses were obtained using measurements on a 70 kW micro gas turbine that is designed to be used in a serial hybrid concept for buses.
Technical Paper
2014-06-30
Barry M. James, Andreas Hofmann
The noise performance of electric vehicles is essential to ensure that they gain market acceptance. This can be a challenge for several reasons. Firstly, there is no masking from the internal combustion engine. Next, there is pressure to move to motor designs such as Switch Reluctance Motors, which have worse dynamic properties than their Permanent Magnet counterparts. Finally, there is the drive towards higher speed motors with their greater power density. Experience has shown that this challenge is frequently not met. It is known that reputable motor suppliers reputable transmission suppliers have designed and developed their "quiet" sub-systems to conventional, state of the art levels, only to discover that the assembled E-powertrain is unacceptably noisy. This paper follows an EU-funded project that is part of the FP7 programme that is focussed on the design of a highly integrated driveline for a passenger car. The consortium is led by Bosch but includes the likes of Renault, Romax Technology, Fuchs and GKN Driveline.
Technical Paper
2014-06-30
Janko Slavic, Martin Cesnik, Miha Boltezar
Car components are exposed to the random/harmonic/impact excitation which can result in component failure due to vibration fatigue. The stress and strain loads do depend on local stress concentration effects and also on the global structural dynamics properties. Standardized fatigue testing is long-lasting, while the dynamic fatigue testing can be much faster; however, the dynamical changes due to fatigue are usually not taken into account and therefore the identified fatigue and structural parameters can be biased. In detail: damage accumulation results in structural changes (stiffness, damping) which are hard to measure in real time; further, structural changes change the dynamics of the loaded system and without taking this changes into account the fatigue load in the stress concentration zone can change significantly (even if the excitation remains the same). This research presents a new approach for accelerated vibration testing of real structures. The new approach bases on phase locked harmonic excitation and can be used for identification of natural frequencies and damping while the damage due to vibration is being accumulated.
Technical Paper
2014-06-30
Jean-Baptiste Dupont, Racha Aydoun, Pascal BOUVET
The noise radiated by an electrical motor is very different from the one generated by an internal combustion engine. It is characterized by the emergence of high frequency pure tones that can be annoying and badly perceived by future drivers, even if the overall noise level is lower than that of a combustion engine. A simulation methodology has been proposed, consisting in a multi-physical approach to simulate the dynamic forces and noise radiated by electric motors. The principle is first to calculate the excitation due to electromagnetic phenomena (Maxwell forces) using an electromagnetic finite element solver. This excitation is then projected onto the structure mesh of the stator in order to calculate the dynamic response. Finally, the radiated sound power is calculated with the aid of a standard acoustic finite element method. The calculation methodology assumes a weak coupling between the different physical levels. It has been validated by comparison with the experiment. This simulation only considers the excitation generated by a perfect machine.
Technical Paper
2014-06-30
Thilo Bein, Dirk Mayer, Jonathan Militzer
The automotive industry is more and more facing the problem of reducing the weight of the vehicle but guaranteeing an equivalent level of comfort in terms of noise, vibration, and harshness (NVH). Improvement of vehicle noise and vibration without affecting other per-formances is proving to be extremely difficult if not impossible with state-of-the-art technolo-gy. Besides advanced passive material systems, active or smart concepts are being increasingly considered for the NVH optimization of vehicles. However, to overcome contradicting re-quirements traditional design and material choices must be revisited. Frequently, new tech-nologies in the fields of smart materials and active control provide potential solutions although they have mainly been proved in the laboratory. Although the principles of controlling NVH in cars was demonstrated some time ago, its commercial application has been slower than in the aviation field, because of the greater cost sensitivity of the automotive industry.
Technical Paper
2014-06-30
Denis Blanchet, Anton Golota, Nicolas Zerbib, Lassen Mebarek
Recent developments in the prediction of the contribution of windnoise to the interior SPL have opened a realm of new possibilities in terms of i) how the convective and acoustic sources terms can be identified, ii) how the interaction between the source terms and the side glass can be described and finally iii) how the transfer path from the sources to the interior of the vehicle can be modeled. This paper discusses in details these three aspects of windnoise simulation and recommends appropriate methods to deliver required results at the right time based on i) simulation and experimental data availability, ii) design stage and iii) time available to deliver these results. Several simulation methods are used to represent the physical phenomena involved such as CFD, FEM, BEM, FE/SEA Coupled and SEA. Furthermore, a 1D and 2D wavenumber transformation is used to extract key parameters such as the convective and the acoustic component of the turbulent flow from CFD and/or experimental data whenever available.
Technical Paper
2014-06-30
Jan Hendrik Elm, Jens Viehöfer, Jan-Welm Biermann
List of authors: Prof. Dr.-Ing. habil. J.-W. Biermann, Dipl.-Ing. Jan Hendrik Elm, Dipl.-Ing. Jens Viehöfer Abstract: The automotive industry permanently enhances Downsizing concepts due to environmental commitments and energy consumption concerns. Even in the category of city- and supermini-cars, great efforts are done for the development of highly charged engines with small displacement. So far the main focus of these developments is set on the reduction of CO2 emissions and fuel consumption. However these are not the only aspects, which have to be fulfilled by the vehicle in order to meet the demands of the customers and to be successful in competition. The NVH-characteristics of such Downsizing vehicles have to match a class-specific level, which can only be achieved by additional measures. Regarding this, a view of the dynamic behavior of the entire vehicle is required. At the Institut für Kraftfahrwesen Aachen (ika) the potential for reducing fuel consumption and CO2 emissions of a Downsizing concept is investigated using a city-car as reference.
Technical Paper
2014-06-30
Bryce Gardner, Tiago Macarios
Speech transmissibility is a critical factor in the design of public address systems for passenger cabins in trains, aircraft and coaches. Speech transmissibility is primarily affected by the direct field, early low order reflections, and late reflections (reverberation) of the source. The direct and low order reflections are affected by the relative location of speakers and seats as well as the acoustic properties of the reflecting walls. To properly capture these early reflections, measures of speech transmissibility typically require time domain information. However, another important factor for speech transmissibility is background noise due to broadband exterior sources such as a flow noise sources. The background noise is typically modeled with broadband steady state assumptions such in statistical energy analysis (SEA). This works presents an efficient method for predicting speech transmissiblity by combining ray tracing with SEA. In this method, the direct field and low order reflections are modelled using raytracing, while the reverberant field and background noise are modelled using SEA.
Technical Paper
2014-06-30
Augusto Medeiros, Tiago Macarios, Gregorio Azevedo, Bryce Gardner
Transmission loss (TL) is a common metric for the comparison of the acoustic performance of mufflers. Muffler TL can be computed from a Boundary Element Method (BEM) model. Perforated tube elements are commonly used in automotive muffler applications. These can be modeled with a detailed BEM model that includes each individual hole in the perforated tube. The main drawback with such a straightforward BEM approach is that the discretionary of the perforated surfaces can result in computationally expensive models. The current work demonstrates an approach to develop a more computationally-efficient, yet, precise way of modeling complex mufflers that contain perforated surfaces with BEM. In this approach, instead of explicitly modeling the perforations explicitly they are taken into account as equivalent transfer impedances. There are several models in the literature that can be used to develop the transfer impedance model of the perforated surface. This paper demonstrates how these models can be used in a BEM prediction and also how one needs to be careful in selecting the cases used to evaluate the models.
Technical Paper
2014-06-30
Arnaud Caillet, Antoine Guellec, Denis Blanchet, Thomas Roy
During the last decade, the automotive industry expressed the need to better understand how the different trim parts are interacting together into a complete car up to 400Hz for structureborne excitations. Classical methods where the acoustic trim is represented as non structural masses (NSM) and high damping in the acoustic cavity can only be used at lower frequency and does not provide insights into the interactions of the acoustic trims with the structure and the acoustic volume. It has been demonstrated in several papers that modelling the acoustic components using poroelastic finite element method (PEM) can yields accurate vibro-acoustic response such as transmission loss of a car component. The increase of performance of today’s computers and the further optimization of industrial simulation codes allow computation to be performed on a full vehicle level with accuracy and computation time adequate for stringent industrial environments such as a car OEM. This paper presents a study of a fully trimmed vehicle excited by structureborne excitations with acoustic trims such as seats, dash insulator, instrument panel, headliner... which are modelled as poroelastic finite elements (PEM) parts.
Technical Paper
2014-06-30
Gilles Nghiem, Shanjin Wang
The vehicle pass-by noise regulation will change (measurement method and noise level limitation) by 2016, and around 2018 the noise limit will be lowered by at least 2dB. This evolution requires naturally significant decreases of engine’s sound radiation. On the other hand, in the current context with high pressure of fuel economy, future engines will be more and more lighten, and this will have negative impact on engine’s sound radiation. Therefore, innovative solutions will be necessary in order improve engine’s sound radiation while keeping engine’s mass reduced. This paper gives an example of solutions developed in Renault. On current engines, heat shields on exhaust face are made with laminated steel which have always negative impact on engine’s radiating noise. A new solution has been developed by Renault with suppliers: a thin metal layer fitted with thick glass fibers. This solution is efficient not only for thermal protection, but also for engine’s noise reduction. By selecting the right material’s density and thickness, the noise reduction can reach 3dB on the exhaust face with the new solution.
Technical Paper
2014-06-30
Dennis Bönnen, Djahanchah Bamdad-Soufi, Hannes Steinkilberg, Kwin Abram
In recent years the automotive industry has been using an increased number of high powered engines with fewer cylinders, with the goal to reduce weight and fuel consumption and hence to achieve lower CO2 emissions. In the following paper an overview about the currently existing methods and products within the exhaust development is given which follow automotive lightweight trend. The typical way of reducing the weight of a system is by decreasing the material thickness. Normally, the acoustic signature of the tailpipe noise does not change for the system, but the risk of introducing unwanted radiation noise is high. In the following, a study of a simple muffler is presented which shows the impact of the thickness reduction on noise radiation. Another possibility is the use of additional components such as valves. In the following, an example of the use of a self-actuated valve is presented. This valve can be implemented upstream in the exhaust system in order to bring a constraint in the system and consequently additional acoustic damping.
Technical Paper
2014-06-30
Antti Hynninen, Mats Abom
The after treatment devices (ATD) used in internal combustion engine (IC-engine) exhaust systems are mainly designed with emphasis on emission control, i.e., chemical efficiency, while paying little attention to the acoustic performance. In automotive applications, the duct diameters are so small that studying the acoustic wave propagation only in the plane wave frequency range is usually sufficient. In the case of medium speed IC-engines, used for example in power plants and ships, the three dimensional acoustic phenomena must also be taken into account. The main elements of the medium speed IC-engine ATD are the selective catalytic reducer (SCR) and oxidation catalyst (OC), which consists of coated capillaries, i.e., the substrates. The number and type of the substrates depends not only on the regional environment legislations but also on the engine type. In this study the acoustic attenuation of the medium speed IC-engine ATD is simulated and the results are compared with measurements.
Technical Paper
2014-06-30
Matt Maunder, Steven A Amphlett, Mathias S Perchanok, Martin Kukacka, Patrick C Niven
Intake and exhaust system development is an important step in automotive design. The intake system must allow sufficient air to flow into the engine, and the exhaust system must allow exhaust gases to depart at the rear of the vehicle, without excessive pressure loss. These systems must also attenuate the acoustic pressure pulsations generated by the engine, such that the noise emitted from the intake and exhaust orifices is constrained within reasonable limits, and exhibits a sound quality in keeping with the brand and vehicle image. Pressure loss and orifice noise tend to be in conflict, so an appropriate trade-off must be sought. Simulation of both parameters allows intake and exhaust systems to be designed effectively, quickly, cheaply and promptly. Linear simulation approaches have been widely used for intake and exhaust acoustic prediction for many decades. The frequency domain characteristics of ducts and mufflers are extremely well established, and calculation times are very short.
Technical Paper
2014-06-30
Gregor Müller, Gottfried Grabner, Michael Wiesenegger, Jörg Jany
The optimal designs of the exterior surface of the vehicle and its suspension system have a direct impact on interior wind noise. They are fixed in early project phases when no hardware prototype is available. Turbulent flows produce both external pressure fluctuations at the vehicle shell, known as hydrodynamic excitation, and excitation by sound waves, known as acoustic excitation. Hydrodynamic and acoustic sound sources are evaluated separately and relative to each other in the frequency domain in order to perform evaluations of different body shapes. MAGNA STEYR Engineering has conducted extensive research, using Computational Aeroacoustic Simulation (CAA) techniques and wind tunnel tests (including clay models), to develop a method that helps the best option is selected in the early project stages.
Technical Paper
2014-06-30
Rebecca Cowles, Andrew Shives, Daniel Rauchholz
Aqueous Heat Reflective Coating for Engine Compartment Insulator ABSTRACT: To satisfy the increased expectations of customers, engineers are challenged to increase fuel economy while also improving noise vibration and harshness (NVH) performance. In order to improve fuel economy, engine compartment designs have become more compact with reduced air flow. Elevated temperatures caused by these designs can degrade the durability and acoustic performance of the fibrous acoustic insulator material. A typical method for protecting insulators from elevated temperatures is to apply an aluminum foil patch to the surface. However, foil patches can restrict the insulator’s ability to absorb sound and can be difficult to apply to complex part shapes. Foil patches can be perforated to allow the insulator to absorb sound, but there is a cost penalty as well as potential of long term performance degradation due to blocked perforations. Since NVH targets are also increasing, it’s important to maximize the benefit of each part.
Technical Paper
2014-06-30
Giorgio Veronesi, Christopher Albert, Eugène Nijman, Jan Rejlek, Arnaud Bocquillet
In many application fields, such as automotive and aerospace, the full FE Biot modelling has been widely applied to elastic structures treated with poroelastic materials in order to predict their vibro-acoustic performance. The main drawback of this approach is the large computational burden and the uncertainty of the input data (Biot parameters) that may lead to less accurate prediction. In order to overcome these disadvantages industry is asking for more efficient techniques. The vibro-acoustic behaviour of structures coupled with poroelastic liners and fluid cavities can be predicted by means of the Patch Transfer Function (PTF) approach. The PTF is a sub-structuring procedure that allows for coupling different sub-systems via impedance relations determined at their common interfaces. The coupling surfaces are discretised into elementary areas called patches. A novel experimental method for the characterisation of poroelastic materials is proposed and validated through an FE model.
Technical Paper
2014-06-30
Hiromichi Tsuji, Satoshi Takabayashi, Eiji Takahashi, Hitoshi Murakami, Shinichi Maruyama
In the prototype experimental phase, no reduction of the noise transfer function (NTF) peak level is occurred even if the level of the vibrational transfer function (VTF) peaks reduces by the countermeasures on the structure. These cases are mainly happened in the frequency range lower than 200Hz. The cause of the issue is difficulty to distinguish which structural modes are coupled with acoustic modes. For this case, the vibrational level created by the suspension modes coupling with the interior acoustic modes is much smaller than the level of the modes creating maximum vibration of suspension in the range of NTF peaks. Therefore, no reduction of NTF can be occurred by reducing the maximum suspension vibration with the countermeasures. In this paper, the method to extract the dominant structural modes coupled with automotive interior acoustic modes is presented. This information is very important to improve the FE model accuracy to represent the physical phenomenon. The applied method was explained with the two cases.
Technical Paper
2014-06-30
Zoran Radmilovic, Josef Zehetner, Daniel Watzenig
Hybrid electric vehicles (HEVs) with a power-split system offer a variety of possibilities in reduction of CO2 emissions and fuel consumption. Power-split systems use a planetary gear sets to create a strong mechanical coupling between the internal combustion engine, the generator and the electric motor. This concept offers rather low oscillations and therefore passive damping components are not needed. Nevertheless, during acceleration or because of external disturbances, oscillations which are mostly influenced by the ICE, can still occur which leads to a drivability and performance downgrade. This paper proposes a design of an active damping control system which uses the electric motor to suppress those oscillations instead of handling them within the ICE control unit. The control algorithm is implemented as part of an existing hybrid controller without any additional hardware introduced. The proposed controller uses a nonlinear observer to estimate the state of the system. Because the system is rather slow and acting upon detection of oscillations has no reasonable effect, the controller predicts the future behavior and the torque distribution in the drive-train.
Technical Paper
2014-06-30
Georg Eisele, Klaus Wolff, Jannis Hoppermanns, Peter Genender
Transfer path analysis is a powerful tool to support the vehicle NVH development. On the one hand it is a fast method to gain an overview of the complex interplay in the vehicle noise generation process. On the other hand it can be used to identify critical noise path and vehicle components responsible for specific noise phenomena. FEV has developed several tools, which are adapted to the considered noise phenomena: Powertrain induced interior noise and vibration is analyzed by VINS (Vehicle Interior Noise Simulation), which allows the deduction of improvement measures fast enough for application in the accelerated vehicle development process. Further on vehicle/powertrain combinations not realized in hardware can be evaluated by virtual installation of the powertrain in the vehicle, which is especially interesting in the context of engine downsizing from four to three or six to four cylinders. Road induced interior noise is investigated by “Chassis-VINS” or “Fast-VINS”, depending on the required level of detailing and project timing.
Technical Paper
2014-06-30
Kasper Steen Andersen, Fuyang Liu
Keywords Aftertreatment system, Exhaust, Silencer, Transfer Matrix, Coupling Introduction The tailpipe noise from an aftertreatment system must comply with legislation and meet customer expectations. The approach to capture the influence of complicated geometries and the ceramic substrates included in full aftertreatment systems is possible by coupling the 1D analytical solution of the substrates with the 3D FEM solution. The originality of the paper This paper present simulation and measurement results for a complete aftertreatment system including DOC, DPF, SCR, mixers and acoustic features with and without mean flow, where the transfer matrix of the aftertreatment system founds the basis for both transmission loss, insertion loss and tail pipe noise calculations. The transfer matrix of the aftertreatment system is extracted after solving the finite element model only once, when applying the appropriate boundary conditions and taking advantage of a symmetric transfer matrix with a determinant of one.
Technical Paper
2014-06-30
Alois Sontacchi, Matthias Frank, Franz Zotter, Christian Kranzler, Stephan Brandl
Today, the number of downsized engines with two or three cylinder engines is increasing due to an increase in fuel efficiency. However, downsized engines exhibit unbalanced interior sound in the range of their optimal engine speed, largely because of their dominant engine orders. In particular, the sound of two-cylinder engines yields half the perceived engine speed of an equivalent four-cylinder engine at the same engine speed. As a result when driving, the two-cylinder engine would be shifted to higher gears much later, diminishing the expected fuel savings. This contribution presents an active in-car sound generation system that makes a two-cylinder engine sound like the more familiar four-cylinder engine. This is done by active, load-dependent playback of signals extracted from the engine vibration through a shaker mounted on the firewall. A blind test with audio experts indicates a significant reduction of the engine speed when shifting to a higher gear. In the blind test, experts favored the interior sound of the proposed sound generation system and perceived better interaction with the vehicle.
Technical Paper
2014-06-30
Alexander Ulz, Alfred Rust, Bernhard Graf, Alois Sontacchi
Due to future directives of the European Union regarding fuel consumption and CO2 emissions the automobile industry is forced to develop new and unconventional technologies. These include for example start-stop-systems, cylinder deactivation or even reduction of the number of cylinders, which however lead to unusual acoustical experiences and customer complaints. Therefore it is necessary to evaluate the sound character of engines with low numbers of cylinders (2 and 3 cylinders) and also the differences to the character of the more common 4-cylinder engines. Psychoacoustic parameters are used to describe and understand the differences and to derive possible potentials for improvement. The used data base consists of artificial head recordings of car interior noise according to defined driving states measured on the AVL test track. Naturally, there are much more recordings available for 4-cylinder engines than for 2- and 3-cylinder engines. This has to be taken into account in the statistical evaluations.
Viewing 1 to 30 of 101161