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Viewing 1 to 30 of 18329
2015-06-15
Technical Paper
2015-01-2129
Andrea Munzing, Stephane Catris
A lot of research work on icing scaling laws has been done during the last decades resulting in a today commonly accepted definition of similarity parameters and scaling laws. Those icing scaling laws have essentially been developed for fixed wing applications because airplane aerodynamic surfaces are too big to be tested in icing wind tunnels. This problem does not exist for helicopter blade profiles. However, the use of icing scaling laws is a very interesting feature in order to be able to predict ice shapes or icing performance penalty for a future helicopter still in development. Thanks to the long experience of Airbus Helicopters with icing tests a database of several real ice shapes on helicopter main and tail rotor blade sections is available. The comparison of the ice shapes obtained at the same icing similarity parameters allows the assessment of 2D icing scaling laws established for fixed wing aircrafts.
2015-06-15
Technical Paper
2015-01-2128
Enrico Bellussi
This paper describes the AgustaWestland past and present experience in the use of US Army HISS flight test results in support to the civil ice clearance for rotorcrafts. The US Army HISS is a CH47D Chinook fitted with a spray bar system providing a cloud for in flight icing evaluation with large part of the rotor (or the fuselage) of the rotorcraft immersed during the flight. The HISS allows to have flight data with stable and partially selectable ice parameters for prolonged flight time, conditions extremely difficult to encounter during natural ice flights. AgustaWestland obtained for AW139 the clearance for flight into known icing conditions (FIPS) by EASA, FAA and TCCA in 2010 and by IAC in 2011. AW139 also obtained the clearance for flight into limited ice conditions (LIPS) by EASA in 2013. In both cases the results of the US Army HISS artificial icing trials have been successfully used to support the certification process.
2015-06-15
Technical Paper
2015-01-2162
Krzysztof Szilder, Edward Lozowski
Atmospheric icing resulting from freezing rain, freezing drizzle and freezing cloud droplets occurs when airborne supercooled water drops freeze on objects they encounter. This process is especially hazardous to aircraft, when the build-up of ice changes the stability and control characteristics of the aerodynamic surfaces. Ice can also be shed with disastrous consequences, if it is ingested into engines, strikes the aircraft or leads to unbalanced aerodynamics forces. Ice accretion is a complex phenomenon involving 3-D multi-phase flow, heat transfer, and gravitational, viscous, surface tension and shear forces. An ability to predict how ice accretes on engineering structures is essential to the prediction of its associated aerodynamic penalties. We have developed an original icing modelling capability, called the “morphogenetic” approach, based on a discrete formulation and emulation of ice formation physics.
2015-06-15
Technical Paper
2015-01-2321
Nicholas Oettle, Andrew Bissell, Sivapalan Senthooran, Mohammed Meskine
Car manufacturers put large efforts into reducing wind noise to improve the comfort level of their cars. Each component of the vehicle is designed to meet its individual noise target to ensure the wind noise passenger comfort level inside the vehicle is met. Sunroof designs are tested to meet low-frequency buffeting targets as well as broadband noise targets for the sunroof in vent position and any noise generated by deflectors. Experimentally testing designs and making changes to meet these design targets typically involves high cost prototypes, expensive wind tunnel sessions, and potentially late design changes. To reduce the associated costs as well as development times, there is strong motivation for the use of a reliable numerical prediction capability early in the vehicle design process.
2015-06-15
Technical Paper
2015-01-2325
Paul Bremner, Chris Todter, Scott Clifton
Title: Sideglass Turbulence and Wind Noise Sources Measured with a High Resolution Surface Pressure Array Authors: Paul Bremner – AeroHydroPLUS, Del Mar CA 92104 USA Chris Todter – Keppel Professional Services, San Diego CA 92107 Scott Clifton – c/o AeroHydroPLUS, Del Mar CA 92104 USA The authors report on the design and use of high resolution micro-electro-mechanical (MEMS) microphone arrays for automotive wind noise engineering. The arrays integrate both sensors and random access memory (RAM) chips on a flexible circuit board that eliminates high channel count wiring and allows the array to be deployed on automobile surfaces in a convenient “stick-on/peel-off” configuration. These arrays have application to the quantitative evaluation of interior wind noise from measurements on a clay model in the wind tunnel, when used in conjunction with a body vibro-acoustic model.
2015-06-15
Technical Paper
2015-01-2326
Denis Blanchet, Anton Golota
Recent developments in the prediction of the contribution of wind noise to the interior SPL have opened a realm of new possibilities. The main physical mechanisms related to noise generation within a turbulent flow and transmission through the vehicle greenhouse are nowadays better understood. Several simulation methods such as CFD, FEM, BEM, FE/SEA Coupled and SEA can be coupled together to represent the physical phenomena involved. The main objective being to properly represent the convective and acoustic component within the turbulent flow to ensure proper computation of the wind noise contribution to the interior SPL of a vehicle. This paper presents comparisons between simulations results and measurements for various configurations such as i) with and without mirror, ii) various A-Pillar shapes, iii) various vehicle speeds and finally iv) various yaw angles.
2015-06-15
Technical Paper
2015-01-2331
Alexander Schell, Vincent Cotoni
Aero-vibro-acoustic prediction of interior noise associated with exterior flow requires accurate predictions of both fluctuating surface pressures across the exterior of a vehicle and efficient models of the vibro-acoustic transmission of these surfaces pressures to the interior of a vehicle. The frequency range of interest varies depending on the region and source of interest. For noise transmitted through a sideglass the frequency range of interest is typically from 1-5kHz. The vibro-acoustic methods used to describe noise and vibration transmission also depend on the frequency range of interest. At higher frequencies methods like statistical energy analysis (SEA) are particularly well suited for describing the response of a trimmed cabin due to the short wavelength response of the interior acoustic space and sound package. An accurate prediction of fluctuating surface pressures also requires an accurate model of the flow over the exterior of the vehicle.
2015-06-15
Technical Paper
2015-01-2342
Jun Zhang PhD, Jian Pang, Siwen Zhang PhD, Xiaoxuan Zhang, Congguang Liu
A Lightweight Dash Insulator Development and Engineering Application for the Vehicle NVH Improvement Jun ZHANG 1,2 , Jian PANG 1,2,*, Cong-guang LIU 1,2, Xiao-xuan ZHANG 1,2, 1 Changan Auto Global R&D Center NVH Department, Chongqing, China, 401120 2. State Key Laboratory of Vehicle NVH and Safety Technology, Chongqing, China,, 401120 * Correspondence author, e-mail address: pangjian@changan.com.cn ABSTRACT The lightweight design for sound package is becoming more and more important in automobile development. The research on lightweight sound package has become one of the hot topics in automobile industry. This paper presents a procedure to develop lightweight dash insulator based on NVH targets. The mechanism to reduce dash panel weight and to improve sound insertion loss simultaneously is described in this paper. The paper illustrates a new lightweight dash insulator structure with surface density 2500g/mm2.
2015-06-15
Technical Paper
2015-01-2365
Zhaohui Sun, Jason Ley, Glen Steyer
Alternative powertrains, in particular electric and plug-in hybrids, create a wide range of unique and challenging NVH issues in today’s automotive industry. Among the emerging engineering challenges from these powertrains, their acoustic performances become more complicated, partially due to reduced ambient masking noise level and light weight structure. In addition, the move away from conventional displacement engines to electrical drive units has created a new array of NVH concerns and dynamics, which are relatively unknown as compared to the aforementioned traditional setups In this paper, an NVH optimization study will be presented, focusing on four distinct factors in EDU gear mesh source generation and radiation: EDU housing and bearing dynamics, gear geometry, EDU shafting torsional dynamics, and EDU housing structure. The study involves intensive FEA modeling/analyses jointly with physical validation tests.
2015-06-15
Technical Paper
2015-01-2367
David Lennström, Arne Nykänen
The number of electric vehicle models has significantly grown in the last few years. Most of the car manufacturers can today offer pure electric or some type of hybrid electric alternatives. When it comes to the acoustic properties of electric cars, the powertrain noise differs dramatically compared to traditional vehicles with internal combustion engines. The low frequency firing orders, mechanical and combustion noise are exchanged with a more high frequency whining signature due to electromagnetic forces and gear whine, lower in level but subject to annoyance. Previous papers have highlighted these differences and also investigated perception criteria in terms of psycho-acoustic metrics. However, investigations of differences between different kinds of electric and hybrid electric cars are still rare. In this study, 13 electrified cars on the market were analyzed in order to obtain a broadened view of the tonal compositions.
2015-06-15
Technical Paper
2015-01-2322
Bastien Ganty, Jonathan Jacqmot, Ze Zhou
At high cruising speed, the car A-pillars generate turbulent air flow. The resulting aerodynamic pressure applied on the windows significantly contributes to the total cabin noise. In order to predict this particular noise contribution, the physic of both the flow and the cabin needs to be accurately modeled. This paper presents an efficient methodology to predict the turbulent noise transmission through the car windows. The method relies on a two-step approach: the first step is the computation of the exterior turbulent field using an unsteady CFD solver (EXA PowerFlow); the second step consists in the computation of the acoustic propagation inside the cabin using a finite element vibro-acoustic solver (Actran). The simplified car cabin of Hyundai Motor Company, studied in this paper, involves aluminum skin, windows, sealant, inner air cavity and acoustic treatment (porous material, damping layer). A pure vibro-acoustic model with hammer shock excitation on a window is first built.
2015-06-15
Technical Paper
2015-01-2344
Murteza T. Erman
In today’s world automotive manufacturers are required to decrease CO2 emissions and increase the fuel economy while assuring driver comfort and safety. To achieve desired acoustic performance targets, automotive manufacturers use various Noise-Vibration-Harshness (NVH) materials which they apply to the vehicle structure either in paint shop or assembly shop. Beside sound deadening coatings applied onto underbody of vehicles they use also either constrained or not-constrained layer of sheets. The majority of these sheets are applied onto floor pan inside the vehicle, known as asphalt-sheets. These asphalt-sheets are highly filled systems with high specific gravity and depending on vehicle 10~20 kg/vehicle application is common. Since early 1990’s, automotive manufacturers also have introduced so called Liquid-Applied Sound Damping materials (LASD).
2015-06-15
Technical Paper
2015-01-2363
Jan Fischer, Matthias Behrendt, Albert Albers, Dirk Lieske
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. For the interior noise of BEV high frequency tonal orders are characteristic. They can for example be caused by the gearbox or the electric drive and strongly influence the perception and rating of the interior noise by the customer. Opposing the importance of the acoustic quality is the lack of knowledge of how to measure, analyze and predict the high frequency tonal noise generated by the dynamic torque of the electric drive. In this contribution methods for measuring, analyzing and predicting the excitation by the dynamic torque of the electric drive are presented. The dynamic torque of the electric drive up to 3.5 kHz is measured on a component test bench with the help of high frequency and high precision digital torque transducer.
2015-06-15
Technical Paper
2015-01-2330
Christian Y. Glandier, Oskar Prill, Mark Eiselt
With the reduction of engine and road noise, wind has become an important source of interior noise when cruising at highway speed. The challenges of weight reduction, performance improvement and reduced development time call for stronger support of the development process by numerical methods. CFD and finite element (FE) vibroacoustic computations have reached a level of maturity that makes it possible and meaningful to chain these methods for wind noise prediction. This paper presents a method used for coupling time domain CFD computations with a finite element vibroacoustic model of a vehicle for the prediction of low frequency wind noise below 500 Hz. The procedure is based on time segmentation of the excitation load and transformation into the frequency domain for the vibroacoustic computations. It requires simple signal processing and preserves the random character as well as the spatial correlation of the excitation signal.
2015-06-15
Technical Paper
2015-01-2329
Paolo Di Francescantonio, Charles Hirsch, Piergiorgio Ferrante, Katsutomo Isono
The prediction of the broadband noise generated by the flow interaction with solid bodies such as for example side mirror noise, exhaust pipe noise, or ventilation and air conditioning noise require in principle the execution of extremely high demanding unsteady CFD simulations that nowadays cannot be afforded in an industrial environment. Therefore research efforts have been focused on alternative approaches that could permit to obtain engineering accurate results with much reduced computational efforts by stochastically reconstructing the turbulent velocity field starting from a steady RANS analysis. Two main families of methods have been introduced up to now, SNGR [1], and RPM[2], but applications in industrial environment are still limited mainly due to the lack of reliability of these methods and the need to introduce some tuning parameters.
2015-06-15
Technical Paper
2015-01-2341
Marc Ingelmann, Holger Bickelmann
BASF supplies the automotive industry with parts made of the Micro-cellular Polyurethane Elastomer - Cellasto®, a material with unique characteristics in NVH applications. For over 50 years our automotive customers are relying on our materials, with the Jounce Bumper being our best known applications. Top mounts and coil-spring-isolators are also a key offering to the industry. A lot of functions in automotive and non-automotive products are using Cellasto® as damping element, such as armrests, seats, torque-dampers, handheld machines etc. The dynamic performance of Cellasto , combined with the ability to work in limited packages, makes it the ideal choice. The amplitude selective damping fits to the automotive requirements: small amplitudes are generating a low damping of the material; high amplitudes are increasing the damping.
2015-06-15
Technical Paper
2015-01-2340
Stephen J. Bennison, Steven M. Hansen, Jingjing Xu PhD, Yuki Shitanoki PhD
Reduction of glazing weight in automobiles is now a distinct possibility due to the commercial availability of relatively thin glass (< 2 mm) of suitable quality. However, thinning down the glass inevitably leads to reductions in structural performance and sound barrier properties, hence making the design of lightweight vehicle glazing elements problematic. It is well recognized that laminated glass, where two or more plies of glass are bonded by a tough, transparent polymer, may be used to improve the acoustic barrier performance of glazing elements. Improvements in acoustics often come with a reduction in laminate stiffness and associated load bearing capability. In this contribution we demonstrate that these two conflicting requirements: acoustics and stiffness (strength) may be balanced and optimized through the use of new polymer and film technology.
2015-06-15
Technical Paper
2015-01-2339
Márcio Calçada, Alan Parrett
Sound absorption materials can be key elements for mass-efficient vehicle noise control. They are utilized at multiple locations in the interior and one of the most important areas is the roof. At this location, the acoustic treatment typically comprises a headliner and an air gap up to body sheet metal. The performance requirement for such a vehicle subsystem is normally a sound absorption curve. Based on headliner geometry and construction, the sound absorption curve shape can be adjusted to increase absorption in certain frequency ranges. In this paper an overall absorption metric is developed to relate design parameters to an absorption curve shape which results in improved in-vehicle performance. This metric is based on sound absorption coefficient and articulation index. Johnson-Champoux-Allard equivalent fluid model and diffuse field equations are used. The results are validated using impedance tube measurements.
2015-06-15
Technical Paper
2015-01-2349
Jiantie Zhen, David Copley, Niranjan Londhe, Scott Fredrickson
Structure-borne inputs to hybrid FEA/SEA models could have significant effects on the model prediction accuracy. The purpose of this work was to obtain the structure-borne inputs using a simplified transfer path analysis and identify the significance of the structure-borne and airborne contributions to the spectator sound power of an engine with enclosure for future modeling references. Force inputs to the enclosure from the engine were obtained and used as inputs to a hybrid engine enclosure model for sound prediction.
2015-06-15
Technical Paper
2015-01-2350
Jiantie Zhen, Scott Fredrickson
Off-highway machine mounting system isolation, especially cab mounting system, significantly affects the operator comfort by providing damping to the harsh inputs and isolating the structure-borne energy from traveling into the cab. Mounting system isolation performance is decided by not only the mount component, but also the mounting structure, and should be treated as a system. This paper gives a review of how the mounting system isolates structural energy and the effect of the mounting structures stiffness to the mounting system isolation performance.
2015-06-15
Technical Paper
2015-01-2078
Alric Rothmayer, Hui Hu
A strong air/water interaction theory is used to develop a fast simplified model for the trapping of water in a film that flows over sub-grid surface roughness. The sub-grid model is used to compute correction factors that can alter mass transport within the film. This sub-grid model is integrated into a covariant film mass transport model for film flow past three-dimensional surfaces of a form suitable for aircraft icing codes. Sample calculations are presented to illustrate the application of the model. Aircraft icing codes usually consist of an aerodynamic solver, a droplet trajectory solver and a mechanism to grow the ice surface. Recently, icing codes have also made use of simple models for surface water transport, typically through a film lubrication model.
2015-06-15
Technical Paper
2015-01-2327
Wind noise is one of the important NVH attributes that impacts customer sensation of vehicle interior quietness. Among many factors that influence wind noise performance, the amount of dynamic door deflection under the pressure load due to fast movement of a vehicle plays an key roll. The excessive deflection could potentially cause opened sealing gap, a.k.a. aspiration leakage, which creates a path through which the exterior aerodynamically induced noise propagates into the vehicle cabin. The dynamic door deflection can be predicted using CFD and CAE tools. This work looks into the internal pressure issue associated with the dynamic load setup during the CAE analysis. The capability of predicting the internal pressure due to high wind speed outside of a vehicle still has not been developed, and the work is based on the wind tunnel measurement involving several vehicles.
2015-06-15
Technical Paper
2015-01-2362
Todd Tousignant, Kiran Govindswamy, Mark Stickler, Ming-Ran Lee
The increasing trend toward electric and hybrid-electric vehicles (HEVs) has created unique challenges for NVH development and refinement. Traditionally, characterization of in-vehicle powertrain noise and vibration has been assessed through standard operating conditions such as fixed gear engine speed sweeps at varied loads. Given the multiple modes of operation which typically exist for HEVs, character-ization and source-path analysis of these vehicles can be more complicated than conventional vehicles. In-vehicle NVH assessment of an HEV powertrain requires testing under multiple operating conditions for identification and characterization of the various issues which may be experienced by the driver. Gener-ally, it is necessary to assess issues related to IC engine operation and electric motor operation (running simultaneously with and independent of the IC engine), under both motoring and regeneration conditions.
2015-06-15
Technical Paper
2015-01-2127
Andrea Munzing, Franck Hervy, Stephane Catris
A helicopter blade profile was tested in the DGA Aero-engine’s S1 icing wind tunnel in Saclay, France in winter 2013/2014. The 2D airfoil was a helicopter main rotor blade profile. Ice accretion tests have been performed to assess the profile’s time dependant aerodynamic behaviour during ice accretion. Real ice shapes were collected after each icing test. Moreover, iced profile polars were realized over a large range of angle of attack until stall. This paper presents the test set up, the test model and the test results. The test results presented in this paper are dry air and iced profile polars as well as ice shapes. The complete iced profile polars and the aerodynamic behaviour in time of the iced blade profile during ice accretion will be used for adjusting and validating prediction tools like Airbus Helicopter’s analytical iced rotor performance degradation model and they will aid to appraise the rotor loads evolution in icing conditions.
2015-06-15
Technical Paper
2015-01-2324
Hangsheng Hou, Guiping Yue
When a sunroof opens to let the fresh air in during driving, there might be several noise issues associated with it. The most common and important one is the wind throb issue, which is normally resolved by installing a wind deflector with sufficient height. However with the wind throb issue gone, other sound quality problems may surface. The most obvious one is the hissing noise, which occurs often in higher speed range. This work investigates a sunroof deflector deployment strategy considering wind throb, hissing noise and other psychoacoustic attributes that could be felt subjectively by a customer. The goal is to optimize sound quality associated with an open sunroof, potentially targeting the most NVH demanding customers in the premium vehicle segment.
2015-06-15
Technical Paper
2015-01-2323
Abdelhakim AISSAOUI, Ravindra S Tupake, Vilas Bijwe, Mohammed Meskine, Franck Perot, Alain BELANGER, Rohit J Vaidya
F or the automotive industry, acoustic comfort is of increasing importance and changes in the market make the HVAC system noise quality a question to be addressed as early as possible during the vehicle development process. On one hand, the so-called traditional sources of annoyance such as engine, road-tires contact, exhaust systems and wind-noise have been significantly reduced for most traditional combustion engine vehicles. On the other hand, the rapid expansion of hybrid and electric vehicles and idling stop systems increases the importance of sources such as HVAC systems considered in the past as secondary. At high mass flow rate, the flow-induced contribution from the ducts and registers is the main source of noise in the mid to high frequency ranges and is more important than the HVAC structure borne and blower engine contributions.
2015-06-15
Technical Paper
2015-01-2345
Arnaud Duval, Valérie Marcel, Ludovic Dejaeger, Francis Lhuillier, Moussa Khalfallah
The Flaxpreg™ is a green and light very long flax fibers thermoset reinforced sandwich, that can be effectively used as multi-position trunk loadfloor or structural floor in the passenger compartment of a vehicle. The prepreg FlaxTapes© of about 120 g/m² constituting the skins of the sandwich, are unidirectionally aligned flax fibers tapes, with acrylic resin here, easily manipulable without requiring any spinning or weaving step and thus without any negative out of plane crimping of the almost continuous flax fibers. Thank to their very low 1,45 density combined with an adaptative 0°/90°/0° orientation of the FlaxTapes© (for each skin) depending on the loading boundary conditions, the resulting excellent mechanical properties allow a – 35% weight reduction compared to petro-sourced Glass mat/PUR sandwich solutions (like the Baypreg).
2015-06-15
Technical Paper
2015-01-2088
Richard E. Kreeger, Lakshmi Sankar, Robert Narducci, Robert Kunz
The formation of ice over lifting surfaces can affect aerodynamic performance. In the case of helicopters, this loss in lift and the increase in sectional drag forces will have a dramatic effect on vehicle performance. The ability to predict ice accumulation and the resulting degradation in rotor performance is essential to determine the limitations of rotorcraft in icing encounters. The consequences of underestimating performance degradation can be serious and so it is important to produce accurate predictions, particularly for severe icing conditions. The simulation of rotorcraft ice accretion is a challenging multidisciplinary problem that until recently has lagged in development over its counterparts in the fixed wing community. But now, several approaches for the robust coupling of a computational fluid dynamics code, a rotorcraft structural dynamics code and an ice accretion code have been demonstrated.
2015-06-15
Technical Paper
2015-01-2343
Jian Pan, Yuksel Gur
OEMs are racing to develop light weight vehicles as government regulations now mandate automakers to nearly double the average fuel economy of new cars and trucks by 2025. Light weight materials such as aluminum, magnesium and carbon fiber composites are being used as structural panels in vehicle body. The reduction in weight in structural panels increases noise transmission into passenger compartment. This poses a great challenge in sound package development since simply increasing weight in sound package components to reduce interior noise is no longer an option. This paper discusses weight saving approaches to reduce noise sources, noise transmission paths, and transmitted noise into the passenger. Light weight sound package materials are introduced to treat and reduced airborne noise transmission into multi-material light weight body structure.
2015-06-15
Technical Paper
2015-01-2079
Colin Hatch, Jason Moller, Eleftherios Kalochristianakis, Ian Roberts
Summary The size and shed time of ice shed from a propeller is predicted using a process that determines ice shape, ice growth rate and both internal and ice-structure interface stresses. A brittle failure damage model is used to predict the onset of local failure and to propagate damage in the ice until local ice shedding is obtained. Background Research into suitable ice-phobic coatings as a potential approach in an integrated aircraft ice protection system (IPS) has been ongoing for many years. Durability of these coatings has been an issue; however future research programmes such as the EU programmes AEROMUCO [1] and STORM [2] are looking to improve the Technology Readiness Level (TRL) of the application of these types of coatings. The introduction of ice-phobic coatings may make it possible to provide ice protection on rotating surfaces without the need for specialist ice protection systems.
Viewing 1 to 30 of 18329