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A Generic Testbody for Low-Frequency Aeroacoustic Buffeting Phenomena

BMW Group, Munich, Germany-Rafael Engelmann, Christoph Gabriel
Vienna University of Technology-Stefan Schoder, Manfred Kaltenbacher
  • 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…
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Modelling and Numerical Simulation of the Noise Generated by Automotive Turbocharger Compressor

TU Wien-Manfred Kaltenbacher, Clemens Freidhager, Stefan Schoder
  • Technical Paper
  • 2020-01-1512
To be published on 2020-06-03 by SAE International in United States
An effective technology to reduce emission and fuel-consumption is the use of turbochargers. A turbocharger increases the air pressure at the inlet manifold of the engine by using the waste energy from the exhaust gas to drive a turbine wheel that is linked to the compressor through a shaft. Besides the use in combustion engines, fuel cell systems for vehicle applications also need compressed air to achieve high power densities. Thereby, in fuel cell systems the noise emission of turbochargers is no longer masked by the combustion engine. In operation, the main noise sources are generated by the flow in the compressor and the different noise phenomena need to be understood in order to efficiently reduce the emitted noise and increase comfort. A huge potential in order to achieve this goal is a simulation based investigation to study in detail the flow mechanism, the aeroacoustic sources and its sound propagation. However, the actual physical source mechanism as rotational and pulsation noise as well as hiss / whoosh noise is currently not fully understood. Therefore, the…
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Numerical Investigation of Tonal Noise at Automotive Side Mirrors Due to Aeroacoustic Feedback

Daimler AG-Alexander Schell, Mark Eiselt
  • Technical Paper
  • 2020-01-1514
To be published on 2020-06-03 by SAE International in United States
In addition to the typical broadband noise character of wind noise, tonal noise phenomena can be much more disruptive, regardless of the overall interior noise quality of the vehicle. Whistling sounds usually occur by flow over sharp edges and resonant gaps, but can also be caused by the feedback of sound waves with laminar boundary layers or separation bubbles and the resulting frequency-selective growth of boundary layer instabilities. Such aeroacoustic feedback can e.g. occur at the side mirror of a vehicle and one compellingly needs the coupling of acoustic and flow field. A compressible large eddy simulation (LES) is in principle suitable but one has to take care of any numerical artifacts which can disturb the entire acoustic field. This paper describes the possibility to resolve aeroacoustic feedback with a commercial 2nd/3rd order finite volume CFD code. A zonal RANS/LES approach is used to ensure a realistic flow around the exterior side mirror mounted at a Mercedes-Benz C-Class. The provided compressible LES are using non-reflecting boundary conditions in combination with a sponge zone approach to…
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Iterative study to improve Air flow distribution on ventilation unit duct using CFD analysis

Subros Limited-ANIT SEN
Subros Ltd-SOMNATH SEN, Arunkumar Goel
  • Technical Paper
  • 2020-28-0030
To be published on 2020-04-30 by SAE International in United States
The aim of this paper is to optimize ventilation unit to meet desirable flow distribution on various ports of the ventilation unit. The adapter is modified and simulation is done on the various design changes. CFD analysis is carried out on the ventilation unit with iterative design and achieved the target airflow and distribution. The analysis been carried out on star CCM+ software. The same been validated on the final proto part developed and tested.
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Transient hot shut down, CFD simulation technique for Underhood thermal management

Tata Motors Ltd-Preetam Ghodake
Tata Technologies Ltd-Rajesh Chhotulal Pawar, Ravindra Tupake
  • Technical Paper
  • 2020-28-0032
To be published on 2020-04-30 by SAE International in United States
During design and development stages of vehicles, thermal protection is of prime importance. Numerical simulations play key role in identifying critical thermal issues for different systems. Hot shut down is one such case where thermal soak phenomenon plays vital role from thermal robustness point of view and there is a need to address this phenomenon using Computational Fluid Dynamics (CFD), which in turn will reduce the development time / testing efforts considerably. This condition is of utmost importance especially when vehicle is moving at higher gradients (uphill sections). In these critical conditions, hot engine compartment starves for cooling airflow despite the fact that fan is operating at maximum speed. The sudden stoppage of vehicle after this high thermal load is known as hot shut down. Maximum temperatures on critical components in engine compartment during continuous running condition are lower as compared to temperatures during hot shut down. This rise in temperatures are critical in designing and optimizing critical components in the proximity of engine and exhaust system for peak thermal loads. This paper describes methodology,…
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Simulation Methodology for design and development of Li-ion Cell and Battery Pack

ICAT-Akash Saxena, Gopal Singh Rathore, Adesh Kumar Chauhan, Shubham chawla
  • Technical Paper
  • 2020-28-0009
To be published on 2020-04-30 by SAE International in United States
The thermal management of Li-ion Cell/ battery pack while charging-discharging plays a significant role in the development of Electric Vehicles, as increase in rate of charge-discharge leads to higher heat generation which decrease the life of li-ion cell drastically, it also increases the possibility of hazard. The present paper reports the simulation methodology for optimizing the design of li-ion cell by performing the simulation to study the variation of potential difference, heat generation and temperature distribution across the cell on different charging- discharging cycles. These simulations lead for better cell design with lesser heat generation. The Computational Fluid Dynamics Analysis is performed for the better thermal management of the battery pack so that maximum heat dissipation could take place. It is expected that this simulation methodology gives an edge in the designing of li-ion cell and battery packs and optimising the performance of cell/ battery pack and ensure the safety.
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Simulation of Hybrid Packed Desiccant beds for De-humidification and Drying

Vellore Inst. of Technology, Vellore-Selvaraji Muthu, Sekarapandian N
  • Technical Paper
  • 2020-28-0019
To be published on 2020-04-30 by SAE International in United States
The conventional vapour compression refrigeration cycle based air dryers are used widely for the applications requiring pressure dew point temperature ranging between 2°C to 3°C. However, for the industrial and pneumatic applications, the required pressure dew points are as low as between -10°C to -75°C. This kind of low pressure dew points can be achieved by the adoption of adsorption based packed bed desiccant dryer technology. In this paper the numerical investigation of the performance of a packed bed desiccant dryer containing homogenous mixture of multiple desiccant types along the vertical axial direction using an in-house finite volume based CFD code is presented. The developed code has the capability to model the coupled heat and mass transfer taking place in a packed hybrid bed desiccant dryer during the adsorption and desorption phases. The numerical results obtained for the base model are validated against relevant experimental data for exit air temperature and moisture content available in the literature and found to have good agreement. Subsequently using the validated numerical model, the improvement in moisture removal capacity,…
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Dynamic behavior of in-cylinder pressure causing fatigue failure of reed valves

Subros Ltd.-Ankit Shukla, Paulson Parayil, Arun Kumar Goel, Kamal Sharma
  • Technical Paper
  • 2020-28-0031
To be published on 2020-04-30 by SAE International in United States
For years, researchers have presented numerous studies that consider interaction between working fluid and reed valve motion in displacement compressors. The computing capacities and available CFD and FEA simulation tools have allowed modeling of fully coupled interaction of fluids and moving structures. The present paper describes our experience and results from developing a simplified model of a multi-cylinder reciprocating piston compressor and estimation of pressure surge during sudden acceleration of such compressors. The results show that sudden speed change causes surge in pressures due to formation of pressure waves that reflect back and forth within cylinder. For the chosen geometry and operating conditions, the duration of such waves is much shorter (~ 0.2ms) as compared to longer response time of reed valves (1 ms) that are stiff and highly inelastic. These high pressure waves eventually exceed the fatigue limit of reed valves and cause failures. These pressure waves also influence the performance of reciprocating by causing noise and vibrations which eventually dissipate in to heat thereby lowering the COP of compressor. Simulation results compare well…
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CFD Analysis and Validation of Automotive Windshield De-Fogging Simulation

Mahindra & Mahindra, Ltd.https://www.sae-Gopinath Sathianarayanan
  • Technical Paper
  • 2020-28-0039
To be published on 2020-04-30 by SAE International in United States
Nowadays Climate component system plays a vital role in JD power rating of automotive vehicle. Apart from customer point of view, stringent homologation norms pose challenge in designing climate control system components. At extreme cold climate conditions either mist/ fog forms on the automobile windshield. This makes visibility issue on driver/Co driver side. To overcome this issue efficient demister system is required. Development of Demister system requires thorough knowledge on velocity spread over windscreen and thermal performance of heater (HVAC). This work is aimed for simulating windshield demisting patterns of a vehicle as described by ECC norms. New methodology was developed to simulate the actual behaviour of condensation and evaporation of mist on the windscreen. Transient demisting patterns were simulated with the CFD code and validated with experimental test results.
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CFD investigation of exhaust gas bypass on truck trolley heating

John Deere India Private, Ltd.-Nitin Dewangan
John Deere India Pvt Ltd-Megha anawat
  • Technical Paper
  • 2020-28-0006
To be published on 2020-04-30 by SAE International in United States
Most of the automobile and off-road vehicles leave the 100% exhaust gases to atmosphere. The temperature of the exhaust gas ranges from 200-350 deg C and the exit velocity of the gas is about 40-100 m/s based on the outlet pipe design. Dump trucks are used to transport mud, sticky waste garbage and sometime ice from one place to dump yard. The paper will describe the approach of partially use the exhaust gases for truck trolley by heating the trolley surfaces from the walls. CFD software is used to evaluate the exhaust system pressure drop and bypass exhaust flow rate requirements for effective heating on trolley wall. The simulation also helped to design the appropriate baffle position for optimum pressure drop and recirculation. Conjugate heat transfer CFD analysis is carried out to predict the flow behavior.