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허형석(Hyungseok Heo),배석정(Sukjung Bae) 한국자동차공학회 2016 한국자동차공학회 부문종합 학술대회 Vol.2016 No.5
Although fuel cost has been the largest portion of annual cost of a construction equipment, it is possible to save the energy and cost by use of fuel economy enhancement technology. In this study, an organic Rankine cycle is applied to an excavator in order to recover the waste heat, reproduce it into electrical energy, and consequently reduce the fuel consumption by 10%. A design process has been carried to develop an exhaust gas superheater recovering the waste heat from exhaust gas through the composite-dimensional thermal flow analysis in the operation conditions set by the previous cycle design. A one-dimensional code has been developed to perform a size design of the exhaust gas superheater. The ranges for the major design parameters have been determined to satisfy the target of the heat recovery, as well as the pressure drop at both fluid sides by use of the code. The pressure drop of exhaust gas showed an obvious tendency to increase according with increase in the number of the tubes, and the waste heat recovery showed a broadly increasing trend with increasing design parameters such as the core length and the housing outer diameter. The heat recovery amount of the heat exchanger with spiral tubes has been found to be significantly increased compared to the one with plain tubes through the one-dimensional design code results, which is used to a comparison with the three-dimensional CFD analysis. By utilizing a 3D commercial code, the arrangement of the exhaust gas tubes has been selected and the working fluid pressure drop has been reduced through detailed layout design, e.g., the modification of the height of the baffles and the geometries of working fluid inlet and outlet have reduced the pressure drop of working fluid up to 25%.
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.
허형석(Hyungseok Heo),이기수(Keesoo Lee),원종필(Jongphil Won),박경석(youngsuk Park) 한국자동차공학회 2004 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
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℃, 300℃ and flow rates vary from 0.008 kg/sec to 0.019 kg/sec. The gas flow and heat transfer in a single tube cooler have been studied using computational fluid dynamics (DFD). 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)
허형석(Hyungseok Heo),이규현(Kyuhyun Lee) 한국자동차공학회 2002 한국자동차공학회 춘 추계 학술대회 논문집 Vol.2002 No.5_1
It is well known that the oval shaped converter has a number of advantages in the constructional durability, the production cost and the quality control than the conventional clam shell type converter. The thermal flow analytical study on the oval shape construction converter was carried out in the paper for the purpose of getting better converting efficiency as well as the durability of the converter. In the study the distribution profile of temperature and flow pattern, very important design factor determining the durability plus the quality, within the oval shape converter flow field by using CFD modelling. The prediction of flow and temperature within the converter were made possible by using the developed method in the study. Also the predictions of the maximum temperature of the shell, mat and substrate, which are affecting the life expectancy of the converter seriously, were made to known. The effect of shell thickness and mid-bed construction were evaluated through application of the developed CFD analytical model.
Fuel Rail의 설계 인자별 압력맥동 특성에 관한 연구
허형석(Hyungseok Heo),배석정(Sukjung Bae),이헌균(Heonkyun Lee),송경석(Kyungsuk Song),박시우(Seewoo Park),김보겸(Bokyoum Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In general, pulsation damper is installed in fuel rail for conventional MPI engine to decrease undesirable cabin noise. However, pulsation damper is so expensive that there are prevailing studies to reduce fuel pressure pulsations with integrated damping effect. This paper is one of basic studies for development of fuel rail to abate pulsations with self-damping effect. Primarily, the pressure pulsation characteristics was investigated with aspect ratio of cross section, wall thickness, and materials of fuel rail. A high aspect ratio or thin wall was found to absorb the pressure pulsations effectively. But volume effects on the fuel pressure pulsation reductions were not especially significant than cross section effects because volume increment rate is larger than pressure pulsation reduction rate. The fuel rail made of aluminum is effective for reduction of pressure pulsation than that of low-carbon steel. Pressure change period increases on the basis of same lengths of supply line and fuel rail as the volume is enlarged and/or the thickness of wall is thinned.
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.