Refine Your Search

Topic

Author

Search Results

Journal Article

A Computational Approach to Evaluate the Automotive Windscreen Wiper Placement Options Early in the Design Process

2013-05-13
2013-01-1933
For most car manufacturers, wind noise from the greenhouse region has become the dominant high frequency noise contributor at highway speeds. Addressing this wind noise issue using experimental procedures 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. Previously, a computational approach that couples an unsteady computational fluid dynamics solver (based on a Lattice Boltzmann method) to a Statistical Energy Analysis (SEA) solver had been validated for predicting the noise contribution from the side mirrors. This paper presents the use of this computational approach to predict the vehicle interior noise from the windshield wipers, so that different wiper placement options can be evaluated early in the design process before the surface is frozen.
Technical Paper

A Computational Approach to Evaluate the Vehicle Interior Noise from Greenhouse Wind Noise Sources - Part II

2011-05-17
2011-01-1620
For most car manufacturers, aerodynamic noise is becoming the dominant high frequency noise source (≻ 500 Hz) at highway speeds. Design optimization and early detection of issues related to aeroacoustics remain mainly an experimental art implying 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 development of a reliable numerical prediction capability. This paper presents a computational approach that can be used to predict the vehicle interior noise from the greenhouse wind noise sources, during the early stages of the vehicle developmental process so that design changes can be made to improve the wind noise performance of the vehicle.
Journal Article

A Computational Process for Early Stage Assessment of Automotive Buffeting and Wind Noise

2013-05-13
2013-01-1929
A computational process for early stage vehicle shape assessment for automotive front window buffeting and greenhouse wind noise is presented. It is a challenging problem in an experimental process as the vehicle geometry is not always finalized. For example, the buffeting behavior typically worsens during the vehicle development process as the vehicle gets tighter, leading to expensive late counter measures. We present a solution using previously validated CFD/CAA software based on the Lattice Boltzmann Method (LBM). A CAD model with realistic automotive geometry was chosen to simultaneously study the potential of different side mirror geometries to influence the front window buffeting and greenhouse wind noise phenomena. A glass mounted mirror and a door mounted mirror were used for this comparative study. Interior noise is investigated for the two phenomena studied. The unsteady flow is visualized and changes in the buffeting and wind noise behavior are explored.
Technical Paper

Application of a New Method for On-Line Oil Consumption Measurement

1999-10-25
1999-01-3460
Fast and exact measurement of engine oil consumption is a very difficult task. Our aim is to achieve this measurement at a common test bed without engine modifications. We resolved this problem with a new technique using Laser Mass Spectrometry to detect appropriate tracers in the raw engine exhaust. The tracers are added to the engine oil. to the engine oil. For detection of these tracers we use a Laser Mass Spectrometer (LAMS). This is a combination of resonant laser ionization (with an all-solid-state laser) and Time-of-Flight Mass Spectrometry. Currently this is the only way to detect oil originated molecules (like our tracers) in the raw exhaust very fast (50 Hz) and sensitive (ppb-region). Thus, engine mapping of oil consumption over load and speed can be performed in 1-2 days with about 90 measurements. Even measurement during dynamic engine operation is possible, but not quantitative (due to the lack of information about dynamic exhaust gas mass flow).
Journal Article

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 disturbance 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 behaviour 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.
Journal Article

Assessment of Broadband Noise Generated by a Vehicle Sunroof at Different Flow Conditions using a Digital Wind Tunnel

2015-06-15
2015-01-2321
For the automotive industry, the quality and level of the wind noise contribution has a growing importance and therefore should be addressed as early as possible in the development process. 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 broadband noise is generated by the turbulent flow developed over the roof opening. A strong shear layer and vortices impacting on the trailing edge of the sunroof are typical mechanisms related to the noise production. Sunroof designs are tested to meet broadband noise targets. 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.
Technical Paper

Convected Wave Equation for a Moving Body in an Inhomogeneous Flow

2018-06-13
2018-01-1517
Sound field around a moving body in a mean flow of fluid is commonly estimated with Ffowcs Williams and Hawkings equation. Similarly as Lighthill’s aeroacoustic analogy, Ffowcs Williams and Hawkings equation includes sound propagation phenomena in moving and inhomogeneous media, such as convection and refraction, implicitly within the source terms on the right-hand side of the equation. Consequently, the equation is primarily applicable when the surrounding fluid is quiescent everywhere outside the source region. In this work, we follow the approach of Phillips and derive an exact aeroacoustic equation for a moving body in an inviscid and isentropic flow, which separates source and propagation terms on the two sides of the equation. As such, the equation can be used even when the sound propagation effects have a significant influence on the sound field.
Technical Paper

Data Reduction in Automotive Multiplex Systems

1994-03-01
940135
Increasing demand for utilities like navigation systems or user-defined electronic phonebooks on one hand and sophisticated engine and gear controls on the other hand leads to growing bus load between distributed local control units. This paper shows the benefits and the characteristics of various state of the art data-compression algorithms and their impact on typical automotive multiplex dataclasses. The evaluation and optimization of promising algorithms can be done via a proposed “communications prototyping”-approach. The hardware/software components of such a rapid prototyping package are outlined. Finally, first performance results of suitable data-compression measures are presented.
Technical Paper

Digital Aeroacoustics Design Method of Climate Systems for Improved Cabin Comfort

2017-06-05
2017-01-1787
Over the past decades, interior noise from wind noise or engine noise have been significantly reduced by leveraging improvements of both the overall vehicle design and of sound package. Consequently, noise sources originating from HVAC systems (Heat Ventilation and Air Conditioning), fans or exhaust systems are becoming more relevant for perceived quality and passenger comfort. This study focuses on HVAC systems and discusses a Flow-Induced Noise Detection Contributions (FIND Contributions) numerical method enabling the identification of the flow-induced noise sources inside and around HVAC systems. This methodology is based on the post-processing of unsteady flow results obtained using Lattice Boltzmann based Method (LBM) Computational Fluid Dynamics (CFD) simulations combined with LBM-simulated Acoustic Transfer Functions (ATF) between the position of the sources inside the system and the passenger’s ears.
Technical Paper

Direct Aeroacoustics Predictions of Automotive HVAC Systems based on Lattice Boltzmann Method

2018-06-13
2018-01-1520
The demand for low noise level in vehicle cabin continues to rise lately. In particular, noise generated by eco-friendly cars such as hybrid and electric ones tends to become lower and lower. In this market environment, the noise contributions caused by HVAC systems are also increasing. Therefore, it becomes increasingly important to accurately predict noise generated by HVAC systems and analyze the noise sources and resolve the noise issue. In this study, direct acoustics prediction approach based on Lattice Boltzmann Method is applied to predict the flow-induced noise from HVAC systems including blower and ducts and find noise sources. In order to validate the simulation result, acoustics measurements are performed on HVAC systems in an anechoic room and the results are compared to each other. A new technique is applied to finding a noise source for a specific frequency and shows improved noise level through modifying the geometry related to noise sources detected by the simulation.
Technical Paper

Evaluation and Improvement of Greenhouse Wind Noise of a SGMW SUV using Simulation Driven Design

2018-04-03
2018-01-0737
At SAIC-GM-Wuling (SGMW) the greenhouse wind noise performance of their vehicles has gained a lot of attention in the development process. In order to evaluate and improve the noise quality of a newly developed SUV a digital simulation based process has been employed during the early stage of the design. CFD simulation was used for obtaining the flow induced exterior noise sources. Performance metrics for the quality were based on interior noise levels which were calculated from the exterior sources using a SEA approach for the noise transmission through the glass panels and propagation to the driver’s or passenger’s head space. Detailed analysis of the CFD results allowed to identify noise sources and related flow structures. Based on this analysis, design modifications were then applied and tested in a sequential iterative process. As a result an improvement of more than 2 dB in overall sound pressure level could be achieved.
Journal Article

Evaluation and Optimization of Aerodynamic and Aero-Acoustic Performance of a Heavy Truck using Digital Simulation

2011-04-12
2011-01-0162
The engineering process in the development of commercial vehicles is facing more and more stringent emission regulations while at the same time the market demands for better performance but with lower fuel consumption. The optimization of aerodynamic performance for reduced drag is a key element for achieving related performance targets. Closely related to aerodynamics are wind noise and cabin soiling and both of them are becoming more and more important as a quality criterion in many markets. This paper describes the aerodynamic and aero-acoustic performance evaluation of a Dongfeng heavy truck using digital simulation based on a LBM approach. It includes a study for improving drag within the design of a facelift of the truck. A soiling analysis is performed for each aerodynamic result by calculating the accumulation of particles emitted form the wheels on the cabin. One of the challenges in the development process of trucks is that different cabin types have to be designed.
Technical Paper

Evaluation of Intersection Assistance Systems Based on Vehicular Communication Systems

2014-04-01
2014-01-0162
Within this work we demonstrate the implementation and evaluation of a vehicle-to-vehicle based intersection assistance system, relying only on communication between the vehicles and not requiring any communication with infrastructural components as it is the case with typical complex intersection assistance systems. It also requires no additional information like right-of-way or maps and works out-of-the-box for nearly all types of intersections. The intersection assistance system utilizes GPS, yaw rate, vehicle acceleration, speed and heading as indicators for a 3D path prediction. While the x-y layer aids in the detection of possible collisions, the z axis is used for detecting bridges and overpasses. By applying several sophisticated filter levels and algorithms, the amount of false positives can massively be reduced while the true positives can be maintained. Finally, the developed simple intersection assistance system is compared to a sophisticated intersection assistance system.
Technical Paper

Evolution of Passenger Car Emission in Germany - A Comparative Assessment of Two Forecast Models

1993-11-01
931988
Two models for the forecast of road traffic emissions, independently developed in parallel, are comparatively presented and assessed: EPROG developed by BMW and enlarged by VDA for a national application (Germany) and FOREMOVE, developed for application on European Community scale. The analysis of the methodological character of the two algorithms proves that the models are fundamentally similar with regard to the basic calculation schemes used for the emissions. The same holds true as far as the significant dependencies of the emission factors, and the recognition and incorporation of the fundamental framework referring to traffic important parameters (speeds, mileage and mileage distribution etc) are concerned.
Technical Paper

Hybrid Technique for Underbody Noise Transmission of Wind Noise

2011-05-17
2011-01-1700
Wind noise has become an important indicator for passenger automobile quality. Several transmission paths can be related to different parts of the vehicle exterior. While the greenhouse (side glasses, windshield, seals & others) often dominates the interior noise level above 500 Hz, the contribution coming from the underbody area usually dominates the interior noise spectrum at lower frequencies. This paper describes a framework of numerical tools which is capable of determining realistic underbody turbulent and acoustic loads being generated for typical driving conditions, as well as performing the noise transmission through underbody panels and the propagation of sound to the drivers ear location.
Technical Paper

Investigations of Automotive Defroster and Windshield Flow

2001-10-01
2001-01-3441
The specification of automotive ventilation / defrosting systems has often utilized “trial-and-error” and “prior experience” techniques. But design development and production efficiency has generated a strong interest in using more sophisticated design tools such as computational fluid dynamics. For this purpose a joint experimental and numerical study was undertaken. This comprehensive investigation was divided into two parts. First, the three dimensional defroster flow field was measured using LDA in an actual automobile. Second, LDA and infrared thermography was used to map the flow and temperature fields for a two dimensional jet impinging upon a slanted plate -- a simplified representation of a car defroster geometry.
Technical Paper

Local Gaussian Process Regression in Order to Model Air Charge of Turbocharged Gasoline SI Engines

2016-04-05
2016-01-0624
A local Gaussian process regression approach is presented, which allows to model nonlinearities of internal combustion engines more accurate than global Gaussian process regression. By building smaller models, the prediction of local system behavior improves significantly. In order to predict a value, the algorithm chooses the nearest training points. The number of chosen training points depends on the intensity of estimated nonlinearity. After determining the training points, a model is built, the prediction performed and the model discarded. The approach is demonstrated with a benchmark system and air charge test bed measurements. The measurements are taken from a turbocharged SI gasoline engine with both variable inlet valve lift and variable inlet and exhaust valve opening angle. The results show how local Gaussian process regression outmatches global Gaussian process regression concerning model quality and nonlinearities in particular.
Technical Paper

Long Term Transient Cooling of Heavy Vehicle Cabin Compartments

2010-10-05
2010-01-2018
A newly developed simulation methodology for a long term, transient tractor cabin cool-down is presented in this paper. The air flow was simulated using a Lattice-Boltzmann Equation (LBE) based 3-dimensional flow solver. The conduction and radiation effects on the solid parts as well as the average cabin air temperature evolution were solved by the thermal solver, which also includes a human comfort model. The simulation results were compared with the measured experimental test data and good agreement was observed validating the developed simulation approach. The developed methodology can be applied to all other ground vehicles cabin comfort applications.
Technical Paper

Model-Based Calibration of an Automotive Climate Control System

2020-04-14
2020-01-1253
This paper describes a novel approach for modeling an automotive HVAC unit. The model consists of black-box models trained with experimental data from a self-developed measurement setup. It is capable of predicting the temperature and mass flow of the air entering the vehicle cabin at the various air vents. A combination of temperature and velocity sensors is the basis of the measurement setup. A measurement fault analysis is conducted to validate the accuracy of the measurement system. As the data collection is done under fluctuating ambient conditions, a review of the impact of various ambient conditions on the HVAC unit is performed. Correction models that account for the different ambient conditions incorporate these results. Numerous types of black-box models are compared to identify the best-suited type for this approach. Moreover, the accuracy of the model is validated using test drive data.
Technical Paper

Model-based Engineering Workflow for Automotive Safety Concepts

2015-04-14
2015-01-0273
Although the ISO 26262 provides requirements and recommendations for an automotive functional safety lifecycle, practical guidance on how to handle these safety activities and safety artifacts is still lacking. This paper provides an overview of a semi-formal safety engineering approach based on SysML for specifying the relevant safety artifacts in the concept phase. Using specific diagram types, different views of the available data can be provided that reflects the specific needs of the stakeholders involved. One objective of this work is to improve the common understanding of the relevant safety aspects during the system design. The approach, which is demonstrated here from the perspective of a Tier1 supplier for an automotive battery system, covers different breakdown levels of a vehicle. The safety workflow presented here supports engineers' efforts to meet the safety standard ISO 26262 in a systematic way.
X