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조승환(Seunghwan Cho),이범호(Beomho Lee),이대엽(Daeyup Lee) 한국자동차공학회 2010 한국자동차공학회 학술대회 및 전시회 Vol.2010 No.11
In order to study the combustion characteristics of engine with various fuels, rapid compression machines have been developed and used as shown in many previous literatures. In this study, a device that could be used as rapid compression and expansion machine and single cycle engine as well as rapid compression machine was developed and validated by testing its performance. By replacing the cam that drives piston and using a cylinder head, the displacement and performance of an engine can be simulated. Motoring tests to compare the driving characteristics of RCM and RCEM were also carried out. A SCE that could simulate the Intake-compression-exhaust processes was also tested to understand the combustion of LPG lean burn engine, where lean limits were measured according to the injection either toward tumble port or swirl port.
Graphics Memory Bandwidth 증가에 따른 GPGPU 성능 향상 분석
조승환(Seunghwan Cho),유승주(Sungjoo Yoo) 대한전자공학회 2015 대한전자공학회 학술대회 Vol.2015 No.6
Graphic Processing Unit (GPU) has been highly hailed as a general-purpose (GP) high-performance computing unit in a wide variety of domains due to its high-computational capability and energy efficiency in comparison with CPU. Introducing High Bandwidth Memory (HBM), which will overcome the memory bandwidth wall within the context of GDDR5, to GPU is scheduled to take place soon. However, actual study on the impact of increased memory bandwidth on the performance of GPU with real GPGPU workloads is still lacking. We used a cycle accurate GPU simulator, GPGPU-Sim, to analyze the memory bandwidth sensitivity on 18 workloads from GPGPU benchmarks such as NVIDIA CUDA SDK, Rodina, and Parboil, and GPGPU-sim. Our results show most of GPU workloads from aforementioned benchmarks has low memory bandwidth sensitivity (x 1.16@ x 2BW, x 1.25@ x 4BW), yet several workloads have significant speedup with increased memory bandwidth. In addition, it is found that correlation between memory bandwidth sensitivity and memory intensiveness across the workloads used in the experiment is small (r=0.0817).
조승환(Seunghwan Cho),이범호(Beomho Lee),이대엽(Daeyup Lee) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.11
DME(Di-methyl Ether) has been expected to be one of the promising alternative fuels for compression ignition engines due to its low emission characteristics for particulate matter. However, its physical properties such as density, bulk modulus and viscosity are not comparable to those of conventional diesel fuel. Especially, problems caused by low lubricity and high compressibility need to be understood more thoroughly, when a DME fuel is used for compression ignition engine, especially with mechanical fuel supply system. In this study, measurement and calculation of DME's bulk modulus were carried out over the range of temperatures from -3℃ to 53℃, and pressures from 50 bar to 250 bar using an experimental apparatus built in this work. The results show that DME is prone to be compressed more easily compared to diesel fuel. A comparison of bulk modulus with butane and propane were also made in this work.
조승환(Seunghwan Cho),이범호(Beomho Lee),이대엽(Daeyup Lee),고상철(Sangchul Ko) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In medium and heavy duty engines for vehicles heavier than 3.5 tons(GVW), an implementation of lean burn technology is very important to lower thermal load and enhance fuel economy. To meet EURO-5 emission regulations, the optimized emission characteristics are also important design factors. In this work, with lean burn technology, a swirl enhancing valve was used in the intake port to improve combustion. Also, the injection position was varied to see its effect on stratification of air fuel mixture, which thus may enhance lean burn characteristics. This work concluded that, with swirl enhancing valve, although torque was decreased, there exist conditions where NOx and THC emissions were reduced at the same level of torque compared with the baseline case. Whereas by varying injection positions with tumble port injection, the combustion characteristics was not satisfactory in terms of torque and emissions.
조승환(Seunghwan Cho),성범모(Beommo Seong),이범호(Beomho Lee),이대엽(Daeyup Lee) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In order to further reduce the exhaust emissions and improve performance, develop of an LPG fuel supply system with liquid injection technology has been drawn an attention. Since an LPG fuel is compressed and expanded with change of its phase, a thermodynamic understanding of an LPLI(liquid phase LPG injection) fuel supply system is very important for its optimal design, In this work, a thermodynamic model was developed to analyze and understand the phase change of an LPG fuel and possible occurrence of vapor-lock phenomenon.
조승환(Seunghwan Cho),성범모(Beommo Seong),이대엽(Daeyup Lee),이범호(Beomho Lee) 한국자동차공학회 2003 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
An investigation of chemical durability with DME(Di-Methyl Ether) for rubber parts, such as O-rings and diaphragms used widely in vehicles, is very important, because DME reacts with rubber materials. Also, since it is expected that DME can be used with the existing fuel infrastructure such as for LPG. a study to evaluate the chemical durability with DME for the widely used rubber materials is strongly required.<br/> In this study, NBR. EPDM, Fluoro and Silicone rubbers were tested with DME to measure the changes of the basic characteristics such as tensile strength-strain, volumetric change (expansion), and surface hardness.<br/> This study concludes that EPDM showed a superior durability with DME, while the fluoro rubber may not be able to use with DME even for a short period.<br/>
IPMSM 속도 제어를 위한 비선형 백스텝핑 제어기 설계
정승환(Seunghwan Jung),서석환(Suhkhoon Suh),조승환(Seunghwan Cho) 한국추진공학회 2015 한국추진공학회 학술대회논문집 Vol.2015 No.11
본 논문에서는 IPMSM(Interior Permanent Magnetic Synchronous Motor)에서 적용할 수 있는 비선형 백스텝핑 제어 방법을 제안한다. 기존 방법으로 설계한 백스텝핑 제어기는 수식이 매우 복잡하여 수식을 도출하는데 쉽지 않은 반면에, 제안한 설계 방법은 dq축 전류에 관한 수식을 간단히 하였기 때문에 보다 쉽게 설계할 수 있다. 설계한 제어기는 시뮬레이션을 통해 PI 제어기와 비교하여 검증하였다. In this paper, a nonlinear back-stepping control technique is proposed for a speed control of IPMSM(Interior Permanent Magnet Synchronous Motor). A back-stepping controller with conventional method is designed with complex formulas. But, the proposed method is easier to design, because of simplifying the formulas of the dq-axis current. Proposed controller is proved by the simulation comparing with PI controller.
이범호(Beomho Lee),조승환(Seunghwan Cho),최지호(Jiho Choi),이대엽(Daeyup Lee),정태형(Taehyung Jeong),이은청(Euncheong Lee),최윤재(Yoonjae Choi) 한국자동차공학회 2005 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2005 No.11_1
A gaseous LPG injection system for SI engines enhances the performance and reduces the emissions compared to the conventional mixer type fuel supply system. Volumetric efficiency of the gaseous LPG injection system has been typically regarded lower than liquefied LPG injection system. In this work, measurements of volumetric efficiency were carried out to investigate the performance of gaseous LPG injection system compared with liquefied injection system. When the length of an intake pipe, injection timing, air/fuel ratio were optimized, the volumetric efficiency with gaseous injection showed little (within experimental error) difference from that of liquefied injection. This demonstrates that a gaseous LPG injection system has an edge over the liquefied injection system in terms of durability and cost reduction.