• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.11a
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• pp.208-214
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• 2000

Reduction of structure-borne noise of the compartment in a car is an important task in automotive engineering. Transfer path analysis using vibroacoustic reciprocity technique or multiple path decomposition method has generally been used for structure-borne noise path analysis. These methods are useful in solving particular problem but do not quantify the effectiveness of vibration isolation of each isolator of a vehicle. To quantify the effectiveness of vibration isolation, the vibrational power flow has been used for a simple isolation system or a laboratory based isolation system. It is often difficult to apply the vibrational power flow technique to the complex isolation system like a car. In this paper, a simple equation is derived for calculation of the vibrational power flow of an isolation system with multiple isolators such as a car. It is successfully applied to not only quantifying the relative contributions of eighteen isolators but also reducing structure-borne noise of a passenger car. According to the results, the main contributor of eighteen isolators is the rear roll mount of an engine. The reduced structure-borne noise level is about 5dBA.

• International Journal of Highway Engineering
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• v.14 no.6
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• pp.131-138
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• 2012

PURPOSES : Two-lane highways have one lane in each direction, and lane changing and passing maneuvers take place in the opposing lane depending on the availability of passing sight distance. 2001 Korea Highway Capacity Manual (KHCM) is classified into two classes of two-lane highways (Type I, II), and average travel speed and time-delayed rate are used as measures of effectiveness (MOEs). However, since existing two-lane highways have both uninterrupted and interrupted traffic flow-system elements, a variety of free-flow speeds exhibits in two-lane highways. In addition, it is necessary to check if the linear-relationship between volumes and time-delayed rate is appropriate. Then, this study is to reestablish the relationship between average travel speed, time-delayed rate, and flow. METHODS : TWOPAS model was selected to conduct this study, and the free-flow speeds of passenger cars and the percentage of following vehicles observed in two-lane highways were applied to the model as the input. The revised relationships were developed from the computer simulation. RESULTS : In the revised average travel speed vs. flow relationship, the free-flow speed of 90km/h and 70km/h were added. It shows that the relationship between time delayed-rate and flow appeared to be appropriate with the log-function form and that there was no difference in time-delayed rate between the free flow speeds. In addition to revise the relationships, the speed prediction model and the time-delayed rate prediction model were also developed. CONCLUSIONS : The revised relationships between average travel speed, time-delayed rate, and flow would be useful in estimating the Level of Service(LOS) of a two-lane highway.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.263-270
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• 2010

In this study, an air cleaner is considered to improve comfort, safety, and health of automobile passengers. The performance and installation conditions of the air cleaner have been studied to investigate their effects on the air quality in the cabin room using numerical analysis. A five-passenger sedan and a seven-passenger minivan that have comparatively large indoor volume have been considered. The distributions of the local mean age and the volume averaged age of indoor air are calculated according to the variation of the placement and the air flow of the air cleaner. In addition, a decrease of contamination concentration, especially VOCs(volatile organic compounds), by the air cleaner is numerically analyzed with time-accurate unsteady calculation to quantify the effect of the air cleaner on the indoor air quality. As a result, the effective installation and operation conditions of the air cleaner for the automobile cabin room could be suggested.

• Fire Science and Engineering
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• v.16 no.3
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• pp.71-76
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• 2002

The real scale tunnel fire tests are carried out for the first time in domestic range to assess the extent of risk in the tunnel fire. The tunnel dimension is 465 m in length, 9.2 m in width and 6.5 m in height. Gasoline pools with 0.25 MW∼2.5 MW size and a 1500CC passenger car are used as fire sources. Six jet fans are used to change the flow velocity inside the tunnel. Temperatures at total 86 points in the tunnel are measured to find the temperature distribution and smoke behavior in the real tunnel fire. In the experiment, it is examined that the important parameters to assess the extent of risk in tunnel fire such as back layering of smoke front, descending of smoke layer and the fire size of a real passenger car.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.557-561
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• 2014

In this work, Altair Engineering's vibroacoustic modeling approach is used to simulate the acoustic signature of a simplified automobile in a wind tunnel. The modeling approach relies on a two step procedure involving simulation and extraction of acoustic sources using a high fidelity Computational Fluid Dynamics (CFD) simulation followed by propagation of the acoustic energy within the structure and passenger compartment using a structural dynamics solver. The tools necessary to complete this process are contained within Altair's HyperWorks CAE software suite. The CFD simulations are performed using AcuSolve and the structural simulations are performed using OptiStruct. This vibroacoustics simulation methodology relies on calculation of the acoustic sources from the flow solution computed by AcuSolve. The sources are based on Lighthill's analogy and are sampled directly on the acoustic mesh. Once the acoustic sources have been computed, they are transformed into the frequency domain using a Fast Fourier Transform (FFT) with advanced sampling and are subsequently used in the structural acoustics model. Although this approach does require the CFD solver to have knowledge of the acoustic simulation domain a priori, it avoids modeling errors introduced by evaluation of the acoustic source terms using dissimilar meshes and numerical methods. The aforementioned modeling approach is demonstrated on the Hyundai Simplified Model (HSM) geometry in this work. This geometry contains flow features that are representative of the dominant noise sources in a typical automobile design; namely vortex shedding from the passenger compartment A-pillar and bluff body shedding from the side view mirrors. The geometry also contains a thick poroelastic material on the interior that acts to reduce the acoustic noise. This material is modeled using a Biot material formulation during the structural acoustic simulation. Successful prediction of the acoustic noise within the HSM geometry serves to validate the vibroacoustic modeling approach for automotive applications.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1875-1880
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• 2003

Measurements of wind flow and pressure fluctuations induced by train passing on station platform have been conducted. Test conventional trains have a different nose shapes - bluff nose and wedged nose. The bluff nose train influence peak value of pressure fluctuations on station platform three times more than the wedged nose train for train speed of 108 km/h. Also, air flow induced by the bluff nose train passing is three times more than the wedged nose train passing. Current study shows that the gust induced by the bluff nose conventional train may threaten a passenger's safety on station platform in proximity to train passage.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.1
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• pp.8-15
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• 2004

Since the vehicle is regarded as the third living space, the comfortable conditions are required in the passenger compartment. For this reason, customers are concerned about the filtering performances and the importance of filter media has been greatly placed. Therefore the dust holding capacity, the efficiency of these filter media (dry paper, wet paper, non-woven) and the configuration of air filter for vehicle were measured in this study. The following results were obtained on the basis of air filter test. It shows that the thickness and poresize of filter media should be lower for the higher efficiency. The measurement result shows that the performance of round shape filters are higher than the square shape filters. The dust holding capacity of the wet paper and the non-woven paper is higher than the dry paper. As a result, this research can provide an important design parameter and product guidance of the intake air filter for vehicular engine.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.569-569
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• 2014

The interior vehicle noise due to the exterior aerodynamic field is an important topic in the acoustic design of a car. The air flow detached from the A-pillar and impacting the side windows are of particular interest as they are located close to the driver / passenger and provides a lower insulation index than the trimmed car body parts. This paper presents a numerical analysis method for a simplified vehicle model. The internal air cavity including trim component are included in the simulation. The car body includes the windshield and two side windows. The body is made of aluminum and trimmed with porous layers. The methodology proposed in this paper relies on two steps: the first step involves the computation of the exterior flow and turbulence induced non-linear acoustic field using CFD Code. The second step consists in the computation of the vibro-acoustic transmission through the window using the finite element vibro-acoustic solver Actran.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.3
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• pp.171-171
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• 1997

Sound intensity distributions and energy flow in the near field of dipole source system and flat plate were investigated. First, the effectiveness of complex acoustic intensity was proved by using mathmatical and experimental methods in order to indentify noise sources and transmission paths of dipole field which is effected by the presence of neighbouring coherent sources. Next, analytical complex acoustic intensity method was discussed and the characteristics and energy flow of sound induced from the plate are clarified. The velocity of plate obtained from Finite Element Method was used for calculation of complex acoustic intensity in the near field. Finally experimental complex acoustic intensity method was applied to a passenger car. It can be seen that complex acoustic intensity method using both of active and reactive intensity is vital in devising a strategy for the identification and the reduction of vibration and noise.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.2
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• pp.108-113
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• 2019

Due to the special structure of the car seat, the heating and cooling module must be installed in a limited area resulting in difficulty in regards to achieving optimal cooling and heating efficiency. In order to solve these problems, this paper establishes a new structure for heating and cooling modules, verifies the structural feasibility of the thermoelectric module for cooling and heating the seat through fluid simulations, and verifies the proper design of the mechanical components of the thermoelectric module.