• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.5
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• pp.129-137
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• 2000

The powertrain is an important factor for the interior and exterior noise behavior of the vehicle Thus, the noise vibration and harshness(NVH) behavior of an engine is becoming a major target of the powertrain development. This paper describes the analyses with the aim to reduce the vibration and noise of an advanced inline 4-cylinder diesel engine block by use of CAE methods. The characteristics of an engine block as a main excitation source of car interior noise is studied. Particularly, The effect of balance shaft to reduce the 2nd order engine excitation force is calculated by forced vibration and radiated noise analysis. The engine exitation forces are obtained under real operating conditions. It is shown that the reduction of vibration and noise level by adapting blancing shaft is well predicted and rediated noise is directly related to the surface velocity of engine block.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.12-18
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• 2004

Transient natures of diesel sprays are often characterized with spray visualization, since it is a non-intrusive and straightforward technique to be applied. However, as injection pressure is increased higher than a thousand bar in a modern direct injection diesel engine, very fine temporal and spatial resolutions in the spray visualization are required while sprays become optically denser. Discussed in this paper are macroscopic and microscopic spray visualization techniques and an example of image processing process for efficient and consistent measurement of spray parameters. The injection rate measurement method based on hydraulic pulse principle was suggested as a way of estimating injection velocity for transient diesel sprays. The spray visualization and injection rate measurement techniques were applied to analyze transient diesel sprays from a common-rail injection system and found to be practically effective.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.4
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• pp.402-409
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• 2015

In this study a quasi-dimensional model is developed to predict the combustion process and emissions of a GDI engine under ultra-lean conditions. Combustion of a GDI engine condition is modeled as two simultaneous processes to consider significant fuel stratification. The first process is premixed flame propagation described as burning in a hemispherically propagating flame. The second is diffusion-controlled combustion modeled as mixing of multiple spray zones in the burned gas region. Mixing is an important factor in ultra-lean conditions leaving stratified mixture of developing sprays behind the propagating premixed flame. Sheet breakup and Hiroyasu models are applied to predict the velocity of a hollow cone spray. Validation is performed against measured pressures and NOx and CO emissions at different load and rpm conditions in the test engine.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.5
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• pp.145-150
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• 2013

Recently, many vehicles have applied electric parts for saving fuel consumption and reducing levels of environmental pollution. ISG (integrated starter & generator) is one of main electric parts and can improve fuel efficiency by using idle stop & go function and regenerative braking system. However, if ISG driving inverter works under the continuously high load condition, it will make the performance and durability of the inverter decreased with rising temperature. In this study, we carried out the analysis on the fluid flow and thermal characteristics of the inverter. As a result, we found the MOSFET of the air cooled inverter was increased up to $116^{\circ}C$ over the limit temperature. On the other hand, the liquid cooled type inverter's MOSFET was decreased by about $17^{\circ}C$ compared to that of the air cooled inverter. Therefore, we verified the feasibility of the liquid cooled type using the present cooling structure.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.2
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• pp.78-83
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• 2016

The development of an exclusive 8-axis multi-tasking machine to finish multiple cutting processes by a single piece of power equipment for securing the high-precision machining and high productivity of the series of shafts (a core part of the automotive powertrain that delivers engine power) is needed. The rigidity of the structure must be improved and the weight of the structure must be reduced to develop a multi-tasking machine with high precision and high productivity. In this paper, we perform a static structural analysis of the initial design of the multi-tasking machines and compare the results of the multi-tasking machines improved by the reinforced design and the results of the initial one. According to the results of the structural analysis, the rigidity of the reinforced machine was increased and the overall weight was decreased. Therefore, the productivity was increased.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.16-22
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• 2007

Fuel efficiency is one of the major issues in regard to energy and environment. As customers desire more comfortable vehicles, increase of accessory traction force is necessary. Air conditioning system (ACS) consumes the biggest traction force among accessories, especially during summer. This means ACS is the primary object deteriorating fuel economy among accessories. Since direct measurement of traction force and fuel consumption in practical vehicle is difficult, comparison analysis is taken between vehicle with and without ACS working. For this comparison, real time measurements are carried out to know ACS traction force and fuel consumption. As a result of the comparison, a vehicle without ACS operation was 15.92% superior to a vehicle with ACS operating. It could be used as a fundamental material for improvement ACS for better fuel efficiency.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.7
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• pp.135-143
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• 2014

Electrified vehicles can be classified with hybrid electric vehicles, battery electric vehicles and fuel cell electric vehicles. These vehicles have two more than energy converters which are the part of a powertrain. It is particularly difficult to estimate the power of hybrid electric vehicles due to two different energy converters with different power characteristics. Therefore, a new power concept for these vehicles is needed. The vehicle power as the new concept for solving this problem was defined in this study. The test method and the procedure were made a development in this study. Four electrified vehicles with different electric fraction were used to validate the method. Two percentage of COV was suggested as a criterion for the maximum vehicles power based on the previous studies. The repeatability of this method was within ${\pm}2$ per cent for the maximum vehicle power and within ${\pm}5$ per cent for the vehicle speed at maximum vehicle power.

• Journal of Institute of Convergence Technology
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• v.7 no.2
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• pp.13-16
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• 2017

The design of sealing mechanisms of a manual pressure valve was analyzed with FE analysis for a hydrogen fuels charge and discharge system of FCEV. The damage prediction of the O-ring with respect to the material models of rubbers was calculated by the gap analysis of the backup ring and O-ring according to the internal pressure. Two kinds of the rubber material characteristic models were adopted to the O-ring. One was the linear elastic and the other was hyperelastic of Ogden $3^{rd}$ order model. The experimental data of urethane of Shore hardness 90 was utilized to the curve fitting of hyperelastic properties. It was found that the contact pattern of the backup ring was different in two models and the sealing mechanism was better in the case of the hyperelastic characteristic model.

• Progress in Superconductivity and Cryogenics
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• v.24 no.2
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• pp.27-38
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• 2022

Urban air mobility (UAM) has recently attracted lots of attention as a solution to urban centralization and global warming. Electric vertical take-off and landing (eVTOL) is a concept that emerges as one of the promising and clean technologies for UAM. There are two difficult challenges for eVTOL aircraft to solve. One is how to improve the weight efficiency of aircraft, and the other is how to complete long-range missions for UAM's flight scenarios. To approach these challenges, we propose a consolidated concept design of battery-fuel cell hybrid tiltrotor aircraft with a liquid hydrogen (LH₂) fuel tank. The efficiency of a battery-fuel cell hybrid powertrain system on the designed eVTOL aircraft is compared to that of a battery-only powertrain system. This paper shows how much payload can increase and the flight scenario can be improved by hybridizing the battery and fuel cell and presenting a detailed concept of a cryogenic storage tank for LH₂.

• Journal of the Korean Electrochemical Society
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• v.4 no.2
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• pp.53-57
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• 2001

When an EV is parked for a long period time, the battery capacity naturally decreases due to selfdischarge. Therefore, this effect must be considered for the accurate measurement of the state of charge of EV battery. Battery selfdischarge simulations using the design of experiments among computer simulation methods are compared with experimental data for Ni/MH batteries for electric vehicles. The motivation is to predict the selfdischarge rate of the battery for electric vehicle at all temperature conditions and standing time when electric vehicle could be operated. We developed a general equation representing the seudischarge rate of the electric vehicle battery using design of experiments, and the equation is determined by temperature and standing time of the battery. We selected Ni/MH battery, 12 V-95 Ah, for pure electric vehicle for this study. ID develop the equation using design of experiments we selected temperature range of $-20^{\circ}~30^{\circ}C$ and standing time of 1 day$\~15$ days. We conducted several selfdischarge tests of Ni/MH battery to verify the integrity of the equation. The results showed that the computation values were in good agreement with experimental data.