The SAE MOBILUS platform will continue to be accessible and populated with high quality technical content during the coronavirus (COVID-19) pandemic. x

Your Selections

Vienna University of Technology
Show Only

Collections

File Formats

Content Types

Dates

Sectors

Topics

Authors

Publishers

Affiliations

Events

   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

A Generic Testbody for Low-Frequency Aeroacoustic Buffeting Phenomena

Vienna University of Technology-Stefan Schoder, Manfred Kaltenbacher
BMW Group, Munich, Germany-Rafael Engelmann, Christoph Gabriel
  • Technical Paper
  • 2020-01-1515
To be published on 2020-06-03 by SAE International in United States
Raising demands towards lightweight design paired with a loss of originally predominant engine noise pose significant challenges for NVH engineers in the automotive industry. Wall thickness reductions particularly emphasize low frequency contributors due to decreasing panel stiffness. From an aeroacoustic point of view, low frequency buffeting ranks among the most frequently encountered issues. The phenomenon typically arises from rooftop or side-window buffeting, structural transmission of hydrodynamic wall pressure fluctuations or, as indicated in this work, through rear vent excitation. A convenient workflow to simulate structure-excited buffeting contains a strongly coupled vibro-acoustic model for structure and interior cavity excited by a spatial pressure distribution obtained from CFD. In the case of rear vent buffeting no validated workflow has been published yet. While approaches have been made to simulate the problem for a real-car geometry, such attempts suffer from tremendous computation costs, meshing effort and lack of flexibility. Additionally, low frequency structural behavior strongly depends on appropriate boundary conditions being subject to manufacturing and mounting tolerances. The goal of this work is to develop, simulate and experimentally…
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

A Fast Modeling Approach for Prediction of SCR Deposits – Implementation and Validation with Advanced Optical Techniques

Vienna University of Technology-Uladzimir Budziankou, Max Quissek, Thomas Lauer
  • Technical Paper
  • 2020-01-0358
To be published on 2020-04-14 by SAE International in United States
The permanently tightening emission regulations for NOx pollutants force further development of automotive exhaust aftertreatment systems with selective catalytic reduction (SCR). Of particular interest is the long-term reliability of SCR-systems with regard to unfavorable operating conditions, such as high injection rates of urea water solution (UWS) or a low exhaust gas temperature. Both of them may lead to formation of solid deposits which decrease system efficiency by increasing backpressure and impairing ammonia uniformity. A fast modeling approach for numerical prediction of deposit formation in urea SCR systems is desired for optimization of system design. This paper presents a modified Smith´s methodology for the modeling of deposit formation risk. A new criterion for determination of the initial foot print of the spray, where the deposit formation is inhibited, is proposed. The threshold values for the evaluation of the liquid film dynamic were validated based on experimental results. Furthermore, for a better prediction of the liquid film pathways, a new approach for realistic modeling of the film viscosity was developed. To achieve a more realistic simulation in…
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Energetic Costs of ICE Starts in (P)HEV - Experimental Evaluation and Its Influence on Optimization Based Energy Management Strategies

Vienna University of Technology-Bernhard Geringer
Daimler AG-Lukas Engbroks, Pascal Knappe, Daniel Goerke, Stefan Schmiedler, Tobias Goedecke
Published 2019-09-09 by SAE International in United States
The overall efficiency of hybrid electric vehicles largely depends on the design and application of its energy management system (EMS). Despite the load coordination when operating the system in a hybrid mode, the EMS accounts for state changes between the different driving modes. Whether a transition between pure electric driving and internal combustion engine (ICE) powered driving is beneficial depends, among others, on the respective operation point, the route ahead as well as on the energetic expense for the engine start itself. The latter results from a complex interaction of the powertrain components and has a tremendous impact on the efficiency and quality of EMSs. Optimization based methods such as dynamic programming serve as benchmark for the design process of rule based control strategies. In case no energetic expenses are assigned to a state change, the resulting EMS suffers from being sub-optimal regarding the fuel consumption. However, an exact determination of such engine start costs has hardly been researched, yet leads to a more efficient EMS.This paper focuses on the experimental evaluation of the energetic…
This content contains downloadable datasets
Annotation ability available
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Biogenous Ethanol: CO2 Savings and Operation in a Dual-Fuel Designed Diesel Engine

Vienna University of Technology-Aleksandar Aleksandrov Damyanov, Peter Hofmann
  • Technical Paper
  • 2019-24-0040
Published 2019-09-09 by SAE International in United States
The usage of ethanol and two different mixtures of ethanol and gasoline (E85 and E65) wаs investigated on a modified diesel engine designed to work in a dual-fuel combustion mode with intake manifold alcohol injection. The maximum ratio of alcohol to diesel fuel was limited by irregular combustion phenomena like degrading combustion quality and poor process controllability at low load and knock as well as auto-ignition at high load. With rising alcohol amount, a significant reduction of soot mass and particle number was observed. At some testing points, substituting diesel with ethanol, E65 or E85 led to a reduction of NOx emissions; however, the real benefit concerning the nitrogen oxides was introduced by the mitigation of the soot-NOx trade-off. The indicated engine efficiency in dual-fuel mode showed an extended tolerance against high EGR rates. It was significantly improved with enhanced substitution ratios at high loads, whereas it dropped at low loads. A simulation model was built for the test engine and selected operation points of the engine test bed measurements were implemented into the model…
This content contains downloadable datasets
Annotation ability available
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Efficiency Prediction for Optimal Load Point Determination of Internal Combustion Engines in Hybrid Drives

Vienna University of Technology-Bastian Beyfuss, Peter Hofmann, Bernhard Geringer
Published 2019-09-09 by SAE International in United States
The efficiency of a Hybrid Electric Vehicle (HEV) strongly depends on its implemented Energy Management Strategy (EMS) that splits the driver’s torque request onto the Internal Combustion Engine (ICE) and Electric Motor (EM). For calibrating these EMS, usually, steady-state efficiency maps of the power converters are used. These charts are mainly derived from measurements under optimal conditions.However, the efficiency of ICEs fluctuates strongly under different conditions. Among others, these fluctuations can be induced by charge air temperature, engine oil temperature or the fuel’s knock resistance.This paper proposes a new approach for predicting the impact of any external influence onto the ICE efficiency. This is done by computing the actual deviation from the optimal reference ignition timing and adjusting the result by actual oil temperature and target air-to-fuel ratio.For calibration, only a fuel consumption map, measured under random conditions, and some warm-up measurements are required. The efficiency prediction is evaluated by measurements from the engine test bench.Due to the real time capability of this method, the integration into any HEV EMS is possible. By considering this…
This content contains downloadable datasets
Annotation ability available
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Experimental PEM-Fuel Cell Range Extender System Operation and Parameter Influence Analysis

Vienna University of Technology-Johannes Höflinger, Peter Hofmann, Bernhard Geringer
Published 2019-04-02 by SAE International in United States
Fuel cells as alternative propulsion systems in vehicles can achieve higher driving ranges and shorter refueling times compared to pure battery-electric vehicles, while maintaining the local zero-emission status. However, to take advantage of pure battery electric driving, an externally rechargeable battery can be combined with a fuel cell range extender. As part of a research project, an efficient air supply system for a fuel cell range extender was developed. To this end, a 25 kW PEM fuel cell system test bench was set up. The different parameter influences of the test bench, in particular of the air supply system, were analyzed and evaluated in terms of stack/system efficiency and functionality. The control software of the test bench was specifically developed for the flexible operating parameter variation. All adjustable variables of the system (air ratio, stack temperature, pressure, etc.) were varied and evaluated at steady-state operating points. Likewise, the system was analyzed during dynamic operation and fault cases in adverse operating conditions (water condensation, oxygen deficiency) were identified. The system's warm-up process was also evaluated in…
This content contains downloadable datasets
Annotation ability available
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Computational Aeroacoustics Based on a Helmholtz-Hodge Decomposition

Vienna University of Technology-Manfred Kaltenbacher, Stefan Schoder
Published 2018-06-13 by SAE International in United States
Using existing aeroacoustic wave equations, we propose a general hybrid aeroacoustic method, based on compressible flow data. By applying the Helmholtz-Hodge decomposition on arbitrary domains, we extract the incompressible projection (non-radiating base flow) of the compressible flow velocity by solving the vector valued curl-curl equation with the vorticity as forcing term. The resulting vortical flow part is used for computing the acoustic source term. This method maintains the favorable properties of the hybrid aeroacoustic method, while still considering acoustic feedback on the flow field.
This content contains downloadable datasets
Annotation ability available
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Numerical Aeroacoustic Noise Prediction for Complex HVAC Systems

Vienna University of Technology-Manfred Kaltenbacher
University of Erlangen-Nürnberg-Matthias Tautz, Stefan Becker
Published 2018-06-13 by SAE International in United States
Reliable tools for the prediction of aeroacoustic noise are of major interest for the car industry and also for the vendors of heating, ventilation and air conditioning (HVAC) systems whose aim is to reduce the negative impact of HVAC noise onto passengers. In this work a hybrid approach based on the acoustic perturbation equations is tested for this purpose. In a first step, the incompressible flow field is computed by means of a commercial finite volume solver. A large eddy simulation turbulence model is used to obtain time resolved flow data, which is required to accurately predict acoustic phenomena. Subsequently, the aeroacoustic sources are computed and conservatively interpolated to a finite element grid, which is used to calculate the sound radiation. This procedure is tested for an HVAC unit, a radial blower and finally for a complete system, which combines these two components. Measurements of the aeroacoustic noise excited by these components are performed in a semi-anechoic chamber. The comparison of spectra obtained from the simulations and the experiments reveals a good agreement up to…
Annotation ability available
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Application and Simulation of Micro-Perforated Panels in HVAC Systems

Vienna University of Technology-Sebastian Floss, Manfred Kaltenbacher
Liebherr-Transportation Systems GmbH-Gerhard Karlowatz
Published 2018-06-13 by SAE International in United States
To reduce noise in a HVAC system for railway application the usage of micro-perforated panels (MPP) is proposed. MPPs offer some favorable characteristics, like robustness and durability in harsh environments and the possibility to optimize absorption in desired frequency bands. The underlying acoustic mechanism can be modelled via an equivalent fluid in accordance with the Johnson-Champoux-Allard (JCA) approach, treating the MPPs as a porous material with rigid frame. This allows to conduct the necessary acoustic pre-evaluation in complex HVAC application scenarios in order for the MPPs to substitute the commonly used foam and fibrous absorber materials.
Annotation ability available
   This content is not included in your SAE MOBILUS subscription, or you are not logged in.

Efficient Prediction of Flow-Induced Sound Sources and Emission from a HVAC Blower

Vienna University of Technology-Manfred Kaltenbacher
SIMetris GmbH-Jens Grabinger
Published 2018-06-13 by SAE International in United States
A shortcoming of widely-used integral methods for prediction of flow-induced sound emission of rotating systems is that the rotation of the impeller can be included in the calculation, but not reflections of sound from the housing, rotor blades and attached ducts. This paper introduces a finite element method that correctly maps both the sound sources rotating with the impeller and the reflections of the sound from the rigid surfaces of the components of the blower. For the prediction of flow-induced sound a hybrid approach is employed using separate CFD and acoustic simulations. It is based on a decomposition of flow (incompressible part) and acoustic (compressible part) quantities and is applicable to high-Reynolds-number and low-Mach-number flows. It features only a scalar unknown (i.e. the acoustic velocity potential), thus reducing the computational effort significantly. In order to compute the sound propagation in the rotating and stationary reference systems simultaneously, a domain decomposition is performed on the numerical model. The rotation of the impeller is introduced through a moving mesh, where the blades act as rigid surfaces. For…
Annotation ability available