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다양한 양생조건에서 지반주입 그라우트의 경화특성에 대한 연구
허형석(Hyungseok Heo),박인준(Innjoon Park) 한국지반환경공학회 2020 한국지반환경공학회논문집 Vol.21 No.11
연약지반 차수 및 보강용 그라우트에 대하여 다양한 양생조건에서 초기 및 장기재령에 걸쳐 내구성에 대한 검토를 수행하였다. 그라우트는 물유리계, 급결광물계 및 아크릴고분자계를 대상으로 하였으며, 양생조건은 수도수(청수) 양생, 인공해수 양생 및 대기 양생으로 하고, 시험은 재령별 일축압축강도와 길이변화량 및 중량변화량에 대하여 수행하였다. 인공해수는 MgCl₂와 MgSO₄ 수용액을 각각 제조하여 사용하였다. 급결광물계와 아크릴고분자계는 수도수와 인공해수에서는 내구성에 큰 변화가 없이 안정적으로 양생되는 반면 물유리의 경우 수도수에 비해 인공해수조건에서 매우 급격한 내구성 저하가 발생되었다. 대기 양생조건에서는 모든 경우에서 수도수 양생에 비해 내구성이 저하되는데, 특히 급결광물계와 물유리계에서 중량감소가 각각 약 62% 및 60%로 큰 내구성 저하가 발생되었다. For water barrier and reinforcing grout in soft ground, the verification of durability was conducted over the initial and long-term ages under various curing conditions. The grout was made of water glass system, fast-hardening mineral (FHM) system, and acrylic polymer system. There were three types of curing conditions that were tab water curing, artificial seawater curing, and atmospheric curing. And the various tests were performed for each sample by age, uniaxial compressive strength, length change, and weight change. As artificial seawater, MgCl₂ and MgSO₄ aqueous solutions were prepared and used, respectively. As the test results, the fast-hardening mineral system and acrylic polymer system were cured stably without significant change in durability in tap water and artificial sea water, whereas water glass system showed a very rapid drop in durability under artificial sea water conditions compared to tap water. In atmospheric curing conditions, durability is lowered compared to water curing in all cases, and in particular, the weight loss in the FHM system and water glass system is about 62% and 60%, respectively, resulting in a significant decrease in durability.
오벌형 자동차 촉매 컨버터의 고온 열적 거동 예측에 관한 연구
허형석(Hyungseok Heo),원종필(Jongphil Won),이규현(Kyuhyun Lee) 한국자동차공학회 2002 한국 자동차공학회논문집 Vol.10 No.5
Considering the high temperature durability, the most important issue is to accurately predict the maximum operating temperature of the shell, mat and substrate. This temperature prediction then defines the material selections for the mat, shell and cones, and allows an assessment to be made as to the necessity of heat shielding. In this papers, The commercial code FLUENT was utilized to simulate automotive oval type catalytic converters, with the objective of predicting thermal behavior under steady-state, high-load conditions. Specialized computational models are used to account for eftects of heat and mass transfer in the monolith, conjugate heat transfer in the various converter materials, and radiation heat transfer.<br/>
Spiral 구조 EGR Cooler의 열유동 특성 평가
허형석(Hyungseok Heo),원종필(Jongphil Won),박경석(Kyoungsuk Park) 한국자동차공학회 2003 한국 자동차공학회논문집 Vol.11 No.6
Cooled EGR is an effective method for the reduction of NOx from a diesel engine and an EGR Cooler is the key component of the system. High efficiency, low pressure loss and compactness are required for the EGR Cooler. To meet these requirements, new geometric tube must be developed. In this paper, a full size EGR cooler test bench has been developed to validate the CFD flow and heat transfer models. Fluid temperature and pressure drop measurements are provided. Inlet temperature is 200℃ and 300℃, and flow rates vary from 0.008 ㎏/sec to 0.019 ㎏/sec. The gas flow and heat transfer in a single tube cooler have been studied using computational fluid dynamics(CFD). Analysis has been carried out in a single tube with a plain tube and six spirally enhanced tubes of varying pitch to depth ratio(p/e).<br/>
자동차용 양토출 단흡입 워터펌프의 성능 예측에 관한 연구
허형석(Hyungseok Heo),박경석(Kyoungsuk Park),이기수(Geesoo Lee),원종필(Jongphil Won) 한국자동차공학회 2004 한국 자동차공학회논문집 Vol.12 No.3
A Numerical analysis has been used to predict the performance in the automotive water pump with double discharge single suction. The influence of parameters such as coolant flow rate, rotational speed, ratio of blade height and clearance has been investigated. Also, the prediction of hydraulic performances such as static pressure rise, shaft power, hydraulic power and pump efficiency is carried out on the water pump including an impeller and a volute casing. A full size water pump test bench has been developed to validate the CFD flow model. Discharge flow rate, suction pressure, discharge pressure, rotational speed and torque measurements are provided. Coolant temperature is 80°C, water tank pressure is 1 kgf/cm² and now rates vary.
PIV 유동 계측을 통한 자동차 프런트 엔드 쿨링 팩 시스템의 외부 유동특성 평가
허형석(Hyungseok Heo),한창평(Changpyung Han),박경석(Kyoungsuk Park),이기수(Geesoo Lee),배석정(Sukjung Bae),원종필(Jongphil Won) 한국자동차공학회 2004 한국 자동차공학회논문집 Vol.12 No.6
The major trend in global automotive market is changing drastically in the way that a vehicle FECPS (Front End Cooling Pack System) is designed and manufactured as an assembly part. The system can encompass many functions, be assembled into a vehicle as a module, and reduce the production cost as well as time. The FECPS consists of an impact beam, an aluminum condenser and a radiator, a carrier and a cooling fan with a BLDC motor. In order to predict the performance of a FECPS accurately, it is essential to properly model the air flow field through various heat exchangers, such as a condenser or a radiator. In this study, the flow field of the system is measured by a PIV (Particle Image Velocimetry) system. The result is compared with that measured with multi-channel anemometer.
PIV 유동 계측을 통한 자동차 프런트 엔드 쿨링 팩 시스템의 외부 유동 특성 평가
허형석(Hyungseok Heo),이기수(Geesoo Lee),배석정(Sukjung Bae),원종필(Jongphil Won),박경석(Kyoungsuk Park),이인섭(Inseop Lee) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
A major trend in global automotive market will drastically change the way that a vehicle FECPS(Front End Cooling Pack System) is designed and manufactured as an assembly part. The system can encompass many functions, be assembled into a vehicle as a module, and reduce the production cost as well as time, The FECPS consists of an impact beam, an aluminum condenser and a radiator, a carrier and a cooling fan with a BLOC motor. In order to predict the performance of a FECPS accurately, it is essential that the air flow field through various heat exchangers, such as a condenser or a radiator, is modeled properly. In this study, the flow field of the system was measured by a PIV(Particle Image Velocimetry) system. The result is verified by comparison with the measurement through a multi-channel anemometer.
엔진 냉각수 폐열 회수를 위한 랭킨 스팀 사이클용 보일러의 성능 설계
허형석(Hyungseok Heo),배석정(Sukjung Bae),황재순(Jaesoon Hwang),이헌균(Heonkyun Lee),이동혁(Donghyuk Lee),박정상(Jeongsang Park),이홍열(Hongyeol Lee) 한국자동차공학회 2011 한국 자동차공학회논문집 Vol.19 No.5
A 2-loop waste heat recovery system with Rankine steam cycles for the improvement of fuel efficiency of gasoline vehicles has been investigated. A high temperature loop(HT loop) is a system to recover the waste heat from the exhaust gas, a low temperature loop(LT loop) is for heat recovery from the engine coolant cold relatively. This paper has dealt with a layout of a LT loop system, the review of the working fluids, and the design of the cycle. The design point and the target heat recovery of the LT boiler, a core part of a LT loop, has been presented and analytically investigated. Considering the characteristics of the cycle, the basic concept of the LT boiler has been determined as a shell-and tube type counterflow heat exchanger, the performance characteristics for various design parameters were investigated.
자동차 밀폐형 워터펌프의 토출구 형상이 수력성능에 미치는 영향
허형석(Hyungseok Heo),이기수(Geesoo Lee),배석정(Sukjung Bae) 한국자동차공학회 2006 한국 자동차공학회논문집 Vol.14 No.1
Recent trend in pursuit of high performance and effectiveness for automotive cooling system has changed the application of material for impeller of automotive water pump from metal to high ability engineering resin, which can achieve optimization of design of impeller geometry and realize lightweight high efficiency water pump. Closed type water pump improves hydraulic loss of fluid through the clearance between volute casing and impeller compared with that of the existing open type water pump(Although closed type is heavier than open type for the same size and same material, adoption of plastics can solve the problem.). In the present study, the characteristics of hydraulic performance of closed type water pump were investigated with respect to the angle between shroud and hub of impeller and the shape of discharge port of volute casing. Performance tests were carried out for 4 cases, that is, for 2 impellers and 2 casings. The modification of shape of only discharge port can enhance the hydraulic performance by 10 percent and the pump efficiency by 4 - 6 percent.
EGR 가스 폐열회수에 의한 디젤엔진의 연비에 미치는 ATF 워밍업의 영향
허형석(Hyungseok Heo),이동혁(Donghyuk Lee),강태구(Taegu Kang),이헌균(Heonkyun Lee),김태진(Taejin Kim) 한국자동차공학회 2012 한국 자동차공학회논문집 Vol.20 No.4
Cold start driving cycles exhibit an increases in friction losses due to the low temperatures of metal components and media compared to the normal operating engine conditions. These friction losses are adversely affected to fuel economy. Therefore, in recent years, various techniques for the improvement of fuel economy at cold start driving cycles have been introduced. The main techniques are the upward control of coolant temperature and the fast warm-up techniques. In particular, the fast warm-up techniques are implemented with the coolant flow-controlled water pump and the WHRS (waste heat recovery system). This paper deals with an effect of fast ATF (automatic transmission fluid) warm-up on fuel economy using a recovery system of EGR gas waste heat in a diesel engine. On a conventional diesel engine, two ATF coolers have been connected in series, i.e., an air-cooled ATF cooler is placed in front of the condenser of air conditioning system and a water-cooled one is embedded into the radiator header. However, the new system consists of only a water-cooled heat exchanger that has been changed into the integrated structure with an EGR cooler to have the engine coolant directly from the EGR cooler. The ATF cooler becomes the ATF warmer and cooler, i.e., it plays a role of an ATF warmer if the temperature of ATF is lower than that of coolant, and plays a role of an ATF cooler otherwise. Chassis dynamometer experiments demonstrated the fuel economy improvement of over 2.5% with rapid increase in the ATF temperature.