엔진모사 실험을 위한 급속 압축팽창기 개발

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.

DME 체적탄성계수의 측정 및 계산

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.

싱글 사이클 엔진을 이용한 희박 연소 한계의 측정

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.

LPLI연료시스템의 열역학적 모델링

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.

DME의 내화학성 측정 및 평가에 관한 연구

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/>

DME 엔진에서 효율향상을 위한 피스톤 형상의 연구

조승환(Cho Seunghwan),곽용환(Kwak Younghwan),이상헌(Lee Sanghun),이대엽(Lee Daeyup) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

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).

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.

초공동 무기체계 현황 및 개발동향

임설(Seol Lim),조승환(Seunghwan Cho),김윤곤(Yoongon Kim) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12

초공동 현상은 수중운동체의 빠른 주행속도로 몸체 전체가 기포에 싸이게 하는 현상을 말하는데, 이는 수중운동체가 기포에 감싸이므로 몸체에 미치는 항력이 크게 감소되기 때문이다. 이 초공동화 기술을 적용하면 기존 동류의 수중운동체에 비해 그리 크지 않은 에너지로도 큰 속도를 낼 수 있으며, 여러 수중 무기체계에 적용 시 획기적인 성능향상을 가져올 수 있다. 본 논문에서는 세계 각국에서 초공동화 기술을 적용하여 개발하고 있는 다양한 무기체계들에 대해 개략적으로 기술하였다. Supercavitation is an extreme cavitation which can be used to make an underwater vehicle like a torpedo be encompassed by a gas bubble and travel so fast that any enemy object detected can not escape from the chasing vehicle. The gas bubble around the vehicle can greatly reduce the skin friction drag and the supercavitating vehicle can fly in the bubble at surprisingly high speeds compared to any similar conventional vehicle, using not much energy to achieve such high speeds. The supercavitation technologies will enable great advancements to underwater weapon systems. In this study, Overview and development trends of various supercavitating weapon systems in the world are described.

2차 전지용 다공체 전극과 나노 유체의 상관 관계

김정명(Jungmyung Kim),조승환(Seunghwan Cho),김두수(Dusu Kim),박희성(Heesung Park) 대한기계학회 2021 大韓機械學會論文集B Vol.45 No.9

바나듐 산화/환원 유동 전지의 시스템 효율 향상을 위한 나노 유체 전해액의 동점도, 차압 및 전기화학적 특성 정량화에 관한 연구를 수행하였다. 네 가지 나노 입자와 세 가지 유체에 대한 동점도 측정은 이론식과 비교되었으며, 친수성 특성을 가지는 나노 입자의 경우 상대적으로 낮은 함량비에서 기존 유체 대비 동점도 특성이 개선되었다. VRFB 활성 영역으로 사용된 다공체 탄소 펠트에 대한 나노유체의 차압 특성은 나노 입자 함량의 증가에 비례하는 결과를 보였다. 나노 유체 전해액의 전기화학적 성능 측정은 MWCNT 나노 입자에 대하여 수행되었으며, 산화/환원 피크 전류의 경우 양극/음극 전해액 모두에서 입자 함량에 비례하여 증가하였다. 음극 전해액의 경우 나노 입자 함량에 비례하는 가역성을 확인하였다. A study was conducted on the quantification of kinematic viscosity, differential pressure, and electrochemical properties of nanofluid electrolytes to improve the efficiency of the vanadium redox flow cell system. The kinematic viscosity measurements for four nanoparticles and three fluids were compared with the theoretical equations, and the kinematic viscosity characteristics of nanoparticles with hydrophilic properties improved compared to conventional fluids at a relatively low content. The differential pressure characteristics of the nanofluid with respect to the porous carbon felt used as the VRFB active region showed a result proportional to the increase in the nanoparticle content. The electrochemical performance measurement of the nanofluidic electrolyte was performed on MWCNT nanoparticles, and the oxidation/reduction peak current increased in proportion to the particle content in both the anode/cathode electrolyte. In the case of the negative electrolyte, the reversibility was confirmed in proportion to the nanoparticle content.