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Technical Paper

Acoustic Fluid-Structure Interaction (AFSI) in the car underbody

2022-06-15
2022-01-0937
The turbulent flow around vehicles causes high pressure fluctuations at the underbody, consisting of both hydromechanic and acoustic contributions. This causes vibrations in the underbody structures, which in turn may lead to sound transmission into the passenger compartment, especially at low frequencies. In this contribution we analyse these phenomena by studying the flow, acoustics and structural vibration of the SAE body in a wind tunnel. The excited and vibrating underbody is resembled by an aluminium plate in the underbody of the SAE body which allows for sound transmission into the interior. Different excitation situations are generated by placing obstacles at the underbody in front of the aluminium plate. For this setup we carry out a fully coupled simulation of flow, acoustics and vibration of the plate. The flow and acoustics are computed with a hybrid method (MGLET), which is two way coupled to a simultaneous solution of the structural vibrations.
Technical Paper

Study of Installation Effects on Automotive Cooling Fan Noise

2022-06-15
2022-01-0935
Vehicle electrification is one of the biggest trends in the automotive industry. Without the presence of a combustion engine, the masking effect from it reduces massively and noise from other components becomes perceivable. Among all, the cooling fan is one of the major noise sources, especially during battery charging. The design of cooling fan modules is usually carried out in the early stage before building prototype vehicles. To understand the effect of the vehicle installation of the cooling fan on the radiated sound is therefore essential to secure good customer satisfaction. In this study, three different measurement setups of cooling fans are carried out, namely free space, wall mounted, and in-vehicle measurement. Four cooling fan prototypes with different fan blade designs are used in each measurement. Correlations of these measurements are investigated through comparisons of the measurement results.
Technical Paper

Aero-acoustic source terms from Large-Eddy Simulation in turbulent pipe flow

2022-06-15
2022-01-0940
In the acoustic design of electric vehicles, novel simulation technologies for predicting relevant sound sources early in the design state become increasingly important. This requires accurate numerical methods to describe these phenomena. The present study computationally investigates the flow-induced noise from aero acoustic sound sources, generated in turbulent pipe flow. The analysis follows a hybrid approach, where the acoustic sound field is predicted separately from the underlying the turbulent flow field, however supplied with acoustic source terms from an incompressible flow simulation of the considered configuration in the limit of low Mach number. Source terms from for use as input into different acoustic analogies, the Lighthill’s wave equation, the vortex-sound theory, and the Perturbed Convective Wave Equation (PCWE) are computed performing incompressible Direct Numerical Simulation (DNS) and Large-Eddy Simulations (LES) of fully developed pipe flow.
Technical Paper

Time-Domain Simulation Approach for the Electromagnetically Excited Vibrations of Squirrel-Cage Induction Machine Drives under Pulse-Width Modulated Supply

2022-06-15
2022-01-0932
One key point of the design process of electrified drive trains is the optimization regarding noise, vibration and harshness (NVH). An important task in this regard is to identify NVH related issues in early design phases by means of computer simulations. A main contributor for vibrations and noises are electromagnetically excited forces and torque stemming from the electric motor that propagate to housing and transmission. In our current study we explore the whole multi-physical simulation workflow from electromagnetics and structural dynamics to acoustics. In electromagnetic simulations, forces and torque signals are calculated for specific speed-torque operation points. In order to consider all system non-linearities correctly, time-domain simulations are carried out. The electric motor investigated in this study is a squirrel-cage induction machine. For this machine type, the simulation effort with full transient numerical methods like finite element analysis is very high.
Technical Paper

Energy Harvesting for lightweight design by means of ferroelectret transmission mechanisms arranged in clusters

2022-06-15
2022-01-0949
Aircraft traffic causes a significant amount of greenhouse gas emissions. Since modern aircrafts are highly electrified, the total weight is affected by cables within the components. Piezoelectric energy harvesting appears to be a reasonable option for reducing cables in certain parts of the aircraft and hence reducing fuel consumption. The proposed work covers energy harvesting in lightweight design with transmission mechanisms using so-called ferroelectrets. The energy harvester (EH) design is motivated by a strain-excitation in an aircraft wing caused by a quasi-stationary dynamic pressure. Ferroelectrets are piezoelectric polymers that show a higher ecological compatibility and a much higher structural flexibility than piezoceramics. Furthermore they provide charge constants in the same order of magnitude as piezoceramics.
Technical Paper

On the different contributions of mounts and flexible hoses on the structure borne noise of refrigerant compressors

2022-06-15
2022-01-0983
Air conditioning acoustics have become of paramount importance in electric vehicles, where noise from electromechanical components is no longer masked by the presence of the internal combustion engine. The coolant compressor is one of the most important elements in the HVAC systems of a car in terms of vibration and noise generation. The generated structural noise is studied in detail in a prototype installation, and the noise transmission and propagation mechanisms are analyzed and discussed. Through ”in situ” measurements and virtual point transformation the rotor unbalance forces and torques acting within the component are identified. The dynamic properties of the rubber mounts installed between the compressor and its support are identified thanks to matrix inversion methods. To assess the quality of the proposed procedure, the synthesised sound pressure level (SPL) is compared with experimental (SPL) measurements in different operational conditions.
Technical Paper

A hybrid numerical/experimental technique for the determination of operative airborne acoustic loads for tire interior noise SEA prediction

2022-06-15
2022-01-0975
The present work deals with the prediction of tire interior noise, a topic that has gained substantial relevance in the last few years with the growth of the number of Battery Electric Vehicle models developed by car manufacturers, for which tire noise is a major contributor to interior noise, especially for urban and peri-urban speeds. For the prediction of tire interior noise, SEA models are widely used, but very seldom in operative driving conditions, mostly because of the difficulties related to the measurement of the corresponding acoustic loads. This article is aimed at proposing a hybrid experimental/numerical procedure for the determination of the tire noise operative acoustic loads acting on a body in white, even in transient conditions.
Technical Paper

Personalized EV Driving Sound Design Based on the Drivier's Total Emotion Recognition

2022-06-15
2022-01-0972
An active sound design (ASD) technique enables the implementation of a specific sound in addition to the real engine/e-motor sound in a vehicle. However, it is difficult to satisfy the various needs of customers because it can provide only a few sounds designed by the manufacturer. This paper presents the method of providing the appropriate driving sounds in an electrical vehicle (EV) according to the driver’s face emotion and physical information in real-time. For this purpose, it is studied to synthesize the characteristic driving sound of EV using the various sound sources, theory of musical harmonics, and granular synthesis method. Also, it is studied to recognize the driver's total emotion using the AI algorithms such as CNN and SVM(support vector machine) and the multi-modal data such as a driver’s facial expression, the heart rate estimated from a driver's face image, and the physical information obtained from a GSR sensor.
Technical Paper

An alternative Solution to Vehicles Audio System using Inertial Transducers integrated in Trim Parts: Advanced Developments.

2022-06-15
2022-01-0970
The use of inertial transducers instead of traditional loudspeakers is an innovative way to reproduce a quality audio signal in a vehicle cockpit while significantly reducing on-board mass and overall volume of the audio system. This paper presents the development process of a new inertial transducer and its optimization by computer simulation, validated by tests on physical prototypes. The innovation uses a new patented mechanism for suspending and guiding the moving magnetic mass. The principle is based on the assembly of two stages of antagonistic springs, allowing a strict oscillating movement guided orthogonaly with respect to the radiating surface, while reducing very strongly the transverse movements, such as pitch and roll, largely responsible for the loss of quality and distortion of the reproduced audio signal. The resonant frequency related to the impedance of the transducer can also be modified by changing the material and geometry of the suspension springs.
Technical Paper

AN IN-DEPTH STUDY ON THE CUSTOMER PERCEPTION OF THE NOISE EMITTED BY ELECTRIC VEHICLES

2022-06-15
2022-01-0968
The interior noise scenario on xEV shows a huge difference with respect to conventional vehicles: the lack of masking from the internal combustion engine dramatically changes the customer driving experience. In addition to this, new and additional acoustic sources become more relevant, and these sources may play a crucial role in determining the NVH footprint of the electrified vehicle. This paper describes how an engineering process can manage the customer’s perception of xEV’s noise.
Technical Paper

Strategies for Minimising the Noise Impact of a Range Extender for an Electric Vehicle

2022-06-15
2022-01-0964
The car buying public’s enthusiasm for electric vehicles continues to accelerate rapidly, driven by a desire to fulfil global climate change objectives, and supported by tax incentives. However, range anxiety persists as one of the main barriers to take-up, because larger battery packs remain heavy and expensive (cell price reductions are slowing). One way to mitigate these disadvantages is to fit a range extender system, powered by an efficient internal combustion engine, but such systems can cause noise concerns. Ricardo has developed a simulation-based approach to define the range extender operating conditions that minimise the impact on noise heard by the driver and passengers inside the vehicle. Transfer path analysis considered both air-borne and structure-borne noise contributions from the range extender, in context with noise contributions from electric drive unit, road and wind, under various typical vehicle operating conditions.
Technical Paper

Improving the sound transmission loss of an aircraft ceiling panel by locally resonant metamaterials

2022-06-15
2022-01-0960
Lightweight structures and designs have been widely used in a number of engineered structures due to ecological and environmental aspects. Nonetheless, lightweight structures typically experience a reduced noise and vibration reduction performance as a consequence of their increased stiffness-to-mass-ratio. To enhance it, novel low mass and compact countermeasures are often sought to address the challenges of achieving not only a good NVH reduction performance but also maintaining a lightweight design. Recently, locally resonant metamaterials have emerged and shown potential as a lightweight noise and vibration solution with a superior performance in tunable frequency ranges, known as stop bands i.e. frequency regions where free wave propagation is not allowed. These can be achieved by assembling resonant elements that are tuned to the targeted frequency range onto a host structure.
Technical Paper

Experimental characterization and dynamic modelling of electrical cables

2022-06-15
2022-01-0952
Electric high voltage (HV) cables are commonly used in electrified vehicles. These cables are well known for being potential flanking transmission paths for structure-borne sound in a broad frequency range and must therefore be included in the NVH design process. Although many different layouts exist automotive HV cables fundamentally exhibit a layered structure consisting of a conductive core covered by, in sequence, an isolating sheath, a wire mesh shield to minimize electromagnetic interference and an outer jacket. The conductive core consists of hundreds of thin copper or aluminum wires organized in strands which are wound in a helical pattern. An extensive measurement campaign was carried out to dynamically characterize different cable specimen in terms of multi-degree of freedom transfer impedances.
Technical Paper

Opening Distortion Fingerprint (ODF) – A New Body Evaluation Method for Perceived Quality and Vehicle Dynamics

2022-06-15
2022-01-0950
The body performance of an electrical vehicle is significantly affected by the structural integration of the stiff battery package. In addition, the body topology of future electrical vehicles/mobility solutions will differ from conventional ones, e.g. no B-pillar. This makes the current body requirements such as static torsional stiffness less relevant. In order to meet these new challenges during the virtual development phase a new body evaluation method has been developed. The method uses the dynamic distortion in all closure openings in a complete vehicle setup to calculate the so-called Opening Distortion Fingerprint (ODF). The ODF evaluation is performed in time and frequency domain. The application of this new method is shown in both test and simulation. There are two main areas of application. One of them is the perceived quality where the ODF can be used as a new body assessment criterion.
Technical Paper

A Study on the Sound Transmission Loss of Split HVAC for Electric Vehicles.

2022-06-15
2022-01-0981
Generally, the HVAC system of a vehicle is composed of Blower unit assembly and Heater unit assembly, and is located at the interior compartment’s side of the dash panel for IC (internal combustion engine) vehicles. Electric vehicles have large space in the PE (power electric) room. This allows HVAC to be pushed to PE room side by placing the Blower unit at the PE room to make the cockpit slim and expand the interior space. However, this new HVAC structure, called the Split HVAC System, is passing through the dash, and allowing the PE noise to transmit to the interior relatively easily. In this paper, a study was performed to enhance the sound transmission of a Split HVAC. A hybrid (FEM+SEA) analysis was performed using VA One, a vibro-acoustic analysis software, in order to simulate the STL up to the high frequency range (~4 kHz) by reflecting the structural and acoustical characteristics of the split HVAC.
Technical Paper

ANC: A Low-cost Implementation Perspective

2022-06-15
2022-01-0967
In the present work, we describe a low-cost implementation of an Active Noise Cancellation (ANC) system. The most interesting feature of our implementation is the use of general-purpose hardware, without the need of expensive and hard-to-program Digital Signal Processing (DSP) devices. In particular, the reference signals, collected with accelerometers properly placed on noise-generating parts and the error feedback signals are collected by means of an USB interface. All signal processing, aimed at primary path estimation and anti-noise audio signal generation, is performed using Simulink running on a commercial mini PC. The Exponential Sine Sweep (ESS) method is adopted for the measurement of the secondary path from the cancellation loudspeakers to the error microphones. An adaptive Filtered-X Least Mean Square (LMS) algorithm determines the anti-noise audio signal to be emitted.
Technical Paper

Strategies for Minimising the Noise Impact of a Range Extender for an Electric Vehicle

2022-06-15
2022-01-0966
The car buying public’s enthusiasm for electric vehicles continues to accelerate rapidly, driven by a desire to fulfil global climate change objectives, and supported by tax incentives. However, range anxiety persists as one of the main barriers to take-up, because larger battery packs remain heavy and expensive (cell price reductions are slowing). One way to mitigate these disadvantages is to fit a range extender system, powered by an efficient internal combustion engine, but such systems can cause noise concerns. Ricardo has developed a simulation-based approach to define the range extender operating conditions that minimise the impact on noise heard by the driver and passengers inside the vehicle. Transfer path analysis considered both air-borne and structure-borne noise contributions from the range extender, in context with noise contributions from electric drive unit, road and wind, under various typical vehicle operating conditions.
Technical Paper

Acoustic Fluid-Structure Interaction (AFSI) in the car underbody

2022-06-15
2022-01-0938
The turbulent flow around vehicles causes high pressure fluctuations at the underbody, consisting of both hydromechanic and acoustic contributions. This causes vibrations in the underbody structures, which in turn may lead to sound transmission into the passenger compartment, especially at low frequencies. In this contribution we analyse these phenomena by studying the flow, acoustics and structural vibration of the SAE body in a wind tunnel. The excited and vibrating underbody is resembled by an aluminium plate in the underbody of the SAE body which allows for sound transmission into the interior. Different excitation situations are generated by placing obstacles at the underbody in front of the aluminium plate. For this setup we carry out a fully coupled simulation of flow, acoustics and vibration of the plate. The flow and acoustics are computed with a hybrid method (MGLET), which is two way coupled to a simultaneous solution of the structural vibrations.
Technical Paper

Assessing low frequency flow noise based on an experimentally validated modal substructuring strategy featuring non-conforming grids

2022-06-15
2022-01-0939
The continuous encouragement of lightweight design in modern vehicles demands a reliable and efficient method to predict and ameliorate the interior acoustic comfort for passengers. Due to considerable psychological effects on stress and concentration, the low frequency contribution plays a vital rule regarding interior noise perception. Apart other contributors, low frequency noise can be induced by transient aerodynamic excitation and the related structural vibrations. Assessing this disturbancy requires the reliable simulation of the complex multi-physical mechanisms involved, such as transient aerodynamics, structural dynamics and acoustics. The domain of structural dynamics is particularly sensitive regarding the modelling of attachments restraining the vibrational behavior of incorporated membrane-like structures. In a later development stage, when prototypes are available, it is therefore desirable to replace or update purely numerical models with experimental data.
Technical Paper

Experimental Assessment of Powertrain Components and Energy Flow Analysis of a Fuel Cell Electric Vehicle (FCEV)

2022-06-14
2022-37-0009
European Union's (EU) Climate Law sets a legally binding target of net-zero greenhouse gas emissions by 2050. EU identified hydrogen technologies as a priority introducing hydrogen-powered propulsion systems into the market. Even though the new registrations of fuel cell (FC) passenger cars increased by 41% in 2020 in Europe, the research community faces a lack of public and independent available data regarding the performance and energy efficiency of state-of-the-art FC electric vehicles. This study introduces a tailored methodology to characterise the different powertrain components and analyse the energy flow for a Fuel Cell Electric Vehicle (FCEV) already available on the market. Experimental data are gathered over different driving conditions, including standard driving cycles such as WLTP and US06 tests performed in a laboratory.
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