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Unsettled Impacts of Integrating Automated Electric Vehicles into a Mobility-as-a-Service Ecosystem and Effects on Traditional Transportation and Ownership

Tallinn University of Technology-Raivo Sell
International Transportation Innovation Center (ITIC)-Joachim Taiber
  • Research Report
  • EPR2019004
Published 2019-12-20 by SAE International in United States
The current business model of the automotive industry is based on individual car ownership, yet new ridesharing companies such as Uber and Lyft are well capitalized to invest in large, commercially operated, on-demand mobility service vehicle fleets. Car manufacturers like Tesla want to incorporate personal car owners into part-time fleet operation by utilizing the company’s fleet service. These robotaxi fleets can be operated profitably when the technology works in a reliable manner and regulators allow driverless operation.Although Mobility-as-a-Service (MaaS) models of private and commercial vehicle fleets can complement public transportation models, they may contribute to lower public transportation ridership and thus higher subsidies per ride. This can lead to inefficiencies in the utilization of existing public transportation infrastructure. MaaS platforms can also cause a reduced reliance on parking infrastructure (e.g., street parking lanes and parking garages) which can contribute to an improvement in overall traffic flow, and a reduction in capital investment for commercial and residential real-estate development. Urban planning can be better centered around the true mobility needs of the citizens without sacrificing valuable…
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Performance of Additive Manufactured Stacks in a Small Scale Thermoacoustic Heat Engine

Tallinn University of Technology-Fabio Auriemma, Yaroslav Holovenko
Published 2019-06-05 by SAE International in United States
Thermoacoustic heat engines (TAHEs) are external combustion engines primarily designed to convert thermal power into acoustic power and, eventually, into mechanical, electric or other forms of high grade power. TAHEs rely on the presence of a porous core, often referred to as “stack”. A temperature gradient is established along the porous core and quasi-adiabatic heat exchanges occur between the solid walls of the pores and the surrounding gaseous medium undergoing pressure fluctuations. The internal geometry of the stack has tremendous impact on the efficiency of thermal-to-acoustic power conversion.In this study, the selective laser melting (SLM) has been used to produce stacks. The SLM is an additive manufacturing (AM) technique designed for 3D metal printing. It is based on high power- density laser which melts and fuses metallic powders together. Three sets of stacks, provided with different hydraulic radii and internal geometries, have been produced. Each set is constituted by two stacks with similar hydraulic radii, one with internal parallel plates and one with internal oblique pin array. The SLM provides precise control of the features…
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Design and Performance of Acoustic Metamaterial Structure for Inlet Duct Noise Attenuation

Tallinn University of Technology-Jüri Lavrentjev, Hans Rämmal
  • Technical Paper
  • 2017-32-0066
Published 2017-11-05 by Society of Automotive Engineers of Japan in Japan
To control noise emission from internal combustion inlet, designers often choose small chamber type silencers at the inlet. In order to improve the inlet acoustic efficiency, inlet ducts with improved acoustic attenuation can be used. One potentially applicable material is acoustic metamaterial rapidly gaining popularity in different fields of engineering application. Small engine inlet duct, designed by using acoustic metamaterial structure comprising an array of resonators inside the wall of a rigid duct is investigated in this study. Experimental investigation of different designs is performed to characterize the acoustic behavior in terms of transmission loss (TL). By connecting multiple resonators of different size and location it is shown that a broadband TL can be achieved. The resulted attenuation band can be tuned by varying the resonator physical characteristics, showing promising potentials such of the material in the described application.
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Reliability Study of Micro-Perforated Elements in Small Engine Silencer Application

Tallinn University of Technology-Hans Rämmal, Jüri Lavrentjev
  • Technical Paper
  • 2017-32-0075
Published 2017-11-05 by Society of Automotive Engineers of Japan in Japan
Since the introduction of microperforated (MP) sound absorption elements more than 40 years ago many variations of noise control devices from room acoustics to induct applications have been manufactured based on this technology.It has been demonstrated that micro-perforated elements can provide adequate IC-engine gas exchange noise attenuation. Several exhaust and inlet system silencers incorporating micro-perforated elements have been presented during the past 15 years for engine applications, encouraging the replacement of the typical fibrous materials and aiming several advantages including cleaner environment.The acoustical characteristics of the MP elements, have been studied thoroughly by several authors and good analytical models exist to predict the attenuation performance of those elements. However, almost no published information can be found regarding the reliability of the MP elements utilized in harsh engine exhaust system environment.In this paper the reliability of stainless still MP element designed for small engine exhaust systems is critically studied, with the focus on the durability of the acoustical performance.
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Damping of Acoustic Waves in Straight Ducts and Turbulent Flow Conditions

Tallinn University of Technology-Heiki Tiikoja, Fabio Auriemma, Jüri Lavrentjev
Published 2016-06-15 by SAE International in United States
In this paper the propagation of acoustic plane waves in turbulent, fully developed flow is studied by means of an experimental investigation carried out in a straight, smooth-walled duct.The presence of a coherent perturbation, such as an acoustic wave in a turbulent confined flow, generates the oscillation of the wall shear stress. In this circumstance a shear wave is excited and superimposed on the sound wave. The turbulent shear stress is modulated by the shear wave and the wall shear stress is strongly affected by the turbulence. From the experimental point of view, it results in a measured damping strictly connected to the ratio between the thickness of the acoustic sublayer, which is frequency dependent, and the thickness of the viscous sublayer of the turbulent mean flow, the last one being dependent on the Mach number. By reducing the turbulence, the viscous sublayer thickness increases and the wave propagation is mainly dominated by convective effects.In the present work, the damping and wall impedance have been extracted from the measured complex wavenumber, which represents the most…
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On the Acoustic Impedance of a Fibreless Sound Absorptive Element

SAE International Journal of Engines

Tallinn University of Technology-Fabio Auriemma, Heiki Tiikoja
  • Journal Article
  • 2015-24-2462
Published 2015-09-06 by SAE International in United States
The acoustic impedance exhibited by a new type of element for noise control, the Micro-Grooved Elements (MGEs), has been widely investigated in this paper.The MGEs are typically composed of two overlying layers presenting macroscopic slots and a number of micro-grooves on one of the contact surfaces. The micro-grooves result in micro-channels as the layers are assembled to form the element. Similarly to Micro-Perforated Elements (MPEs), the MGEs have been proved to provide effective dissipation of acoustic energy by the means of viscous losses taking place in the micro-channels. However, in contrast to the MPEs, the MGEs use the grooves, instead of the holes, in which the air is forced to pass through. It results in more cost effective elements, which have been found to represent an adequate alternative for fibrous materials, typically present in silencer units.The design of the MGEs has been largely improved since the year 2012 and a number of configurations, provided with different internal geometries, have been produced during the last three years. For this reason new and more general models are…
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Application of Novel Micro-Grooved Elements to Small Engine Silencer

Tallinn University of Technology-Fabio Auriemma, Hans Rammal, Juri Lavrentjev
Published 2013-10-15 by Society of Automotive Engineers of Japan in Japan
Micro-grooved elements (MGEs) represent a novel technology developed for noise control in automotive, aerospace and room acoustics.The key concept of the MGEs is based on the use of micro-grooved layers forming micro-paths where the energy dissipation of the acoustic waves is primarily originated by viscous friction.Composed of a multi-layer fiber-less material, the MGEs represent a potential alternative to the traditional fibrous material based solutions as well as to the increasingly popular micro-perforated elements (MPEs). MGEs are designed as cost effective elements, found to be suitable for substitution of fibrous materials, typically present in silencer units.In this paper, a design procedure for a fiber-less small engine silencer based on MGEs is presented and experimentally validated.Hereby, the acoustical performance of the MGEs has been modeled by adapting the theoretical models provided by Allard and Maa for rectangular and circular ducts. The simulated impedance and absorption coefficient of a MGE have been compared to the experimentally determined data by following the classical two-port approach.The absorption coefficients of micro-grooved sample and micro-perforated element have also been analyzed in comparison.As…
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Extended Investigations on Micro-Grooved Elements - A Novel Solution for Noise Control

SAE International Journal of Materials and Manufacturing

Tallinn University of Technology-Fabio Auriemma, Hans Rammal, Jüri Lavrentjev
  • Journal Article
  • 2013-24-0068
Published 2013-09-08 by SAE International in United States
The goal of this paper is to provide a complete characterization of acoustic performance for a novel type of advanced acoustic material - micro grooved element (MGE). In a previous study, the MGEs have been proved to offer a respectable alternative for the existing and increasingly popular micro perforated elements (MPEs).The MGEs are multi-layer elements where the acoustic attenuation effect originates from viscous losses taking place in a number of sub-millimeter grooves forming acoustic micro-paths inside the material. This new configuration allows to replace the laser perforation process, used to manufacture the MPEs, with less time consuming and more cost effective technologies. Moreover, such elements preserve low weight and surface roughness. Experiments have demonstrated that the MGEs can be regarded as suitable solution for noise control in a wide range of applications.In this work, the transfer impedance and the absorption coefficient of a number of MGEs, composed of geometrically different apertures, have been investigated by using the classical two-port method. The effect of the main geometrical parameters controlling the acoustic performance has been analyzed and…
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Acoustical Methods for Investigating Turbocharger Flow Instabilities

Tallinn University of Technology-Hans Rammal
KTH Royal Institute of Technology-Mats Abom
Published 2013-05-13 by SAE International in United States
In order to increase the internal combustion engine efficiency turbocharging is today widely used. The trend, in modern engine technology, is towards higher boost pressures while keeping the combustion pressure raise relatively small. The turbocharger surge occurs if the pressure at the outlet of the compressor is greater than it can maintain, i.e., a reverse flow will be induced. In presence of such flow conditions instabilities will occur which can couple to incident acoustic (pressure) waves and amplify them.The main objective of the present work is to propose a novel method for investigation of turbocharger flow instabilities or surge precursors. The method is based on the determination of the acoustic two-port data. The active part of this data describes the sound generation and the passive part the scattering of sound. The scattering data will contain information about flow-acoustic interaction and amplification of sound that could occur close to surge.Here the existence of such amplification will be investigated for a compressor operating at different operating points including points near the surge line. In addition the generated…
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Micro-Grooved Elements - A Novel Solution for Noise Control

SAE International Journal of Materials and Manufacturing

Tallinn University of Technology-Fabio Auriemma, Hans Rammal, Jüri Lavrentjev
  • Journal Article
  • 2013-01-1941
Published 2013-05-13 by SAE International in United States
The goal of this paper is to present a novel type of advanced acoustic material - micro grooved element (MGE) - which is designed for noise control in a wide range of applications. MGEs have been proved to offer a respectable alternative for the existing micro-perforated elements (MPEs), while being cost effective and causing low pressure loss. These elements have been found to be suitable for substitution of fibrous materials, typically present in silencer units.Currently, the cost of the MPEs is relatively high due to the technological complexity of manufacturing process. On the other hand, cheaper solutions of MPEs, based on irregularly shaped micro-apertures, potentially cause higher pressure loss due to surface roughness.The key concept of the MGEs is the use of micro-grooves forming acoustic channels, instead of the micro-holes of MPEs, which the sound wave has to pass. This allows to replace the laser perforation process, used to manufacture the MPEs with circular cross section, with less time consuming and more cost effective alternatives.The acoustical performance of the MGEs has been modeled by adapting…
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