MTBE 가솔린기관의 배기가스 특성에 관한 연구

노병준(Byungjoon Rho),이삼구(Samgoo Lee),김규철(Kyuchul Kim) 한국추진공학회 2001 한국추진공학회지 Vol.5 No.2

밸브 디스크 차단비 변화가 버터플라이밸브의 손실계수에 미치는 영향에 관한 실험적 연구

노병준(Byungjoon Rho),이지근(Jeekeun Lee),최희주(Heejoo Choi) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.1

The loss coefficient of the butterfly valve which allows partial opening of the valve at closed position and is applicable to the small-sized pipe system with the diameter of 1 inch was measured for the variation of the valve disk blockage ratio. Two different types of the valve disk configuration to adjust the blockage ratio were considered. One was the solid type valve disk of which the diameter was changed into the smaller size rather than the pipe diameter, and the other was the perforate type valve disk on which some holes were perforated. The results from two types of valve disk were compared to identify their characteristics in the loss coefficient distributions. The loss coefficient and the controllable angle of the valve disk were decreased exponentially with the decrease of the blockage ratio. In addition, the perforate valve disk had the effect on the higher loss coefficient rather than the solid type valve disk.

Two-Tracer LIF-PIV Technique for Quantitative Estimation of Droplets-Entrained Ambient Air Relative Velocity in D.I. Gasoline Spray

Jeekeun LEE,Byungjoon RHO,Kyukeun SONG,Jaeyoun JUNG,Keiya NISHIDA 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.10

The spray and ambient air motions produced by a swirl-type D.I. gasoline injector were simultaneously measured by combining the laser induced fluorescence and the particle image velocimetry (LIF-PIV) techniques. For the simultaneous measurement of the fuel spray and the ambient air velocities, the succeeding two image pairs of the spray and the ambient air tracer particle were captured by using two high-resolution CCD cameras. The images acquired were analyzed by the double frame cross-correlation PIV technique, and the droplets and ambient air velocity distributions were obtained. Furthermore, distributions of relative velocities between the droplets and ambient air in the spray were analyzed.

Atomization Characteristics of Intermittent Multi-Hole Diesel Spray Using Time-Resolved PDPA Data

Jeekuen Lee,Shinjae Kang,Byungjoon Rho 대한기계학회 2003 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.17 No.5

The intermittent spray characteristics of a multi-hole diesel nozzle with a 2-spring nozzle holder were investigated experimentally. Without changing the total orifice exit area, the hole number of the multi-hole nozzle varied from 3 (dn=O.42 mm) to 5 (dn=O.32 mm). The timeresolved droplet diameters of the spray including the SMD (Sauter mean diameter) and the AMD (arithmetic mean diameter), injected intermittently from the multi-hole nozzles into still ambient air, were measured by using a 2-D PDP A (phase Doppler particle analyzer). The 5hole nozzle spray shows the smaller spray cone angle, the decreased SMD distributions and the small difference between the SMD and the AMD, compared with that of the 3-hole nozzle spray. From the SMD distributions with the radial distance, the spray structure can be classified into the three regions: (a) the inner region showing the high SMD distribution; (b) the mixing flow region where the shear flow structure would be constructed; and (c) the outer region formed through the disintegration processes of the spray inner region and composed of fine droplets. Through the SMD distributions along the spray centerline, it reveals that the SMD decreases rapidly after showing the maximum value in the vicinity of the nozzle tip. The SMD remains the constant value near the Z/dn= 166 and 156.3 for the 3-hole and 5-hole nozzles, which illustrate that the disintegration processes of the 5-hole nozzle spray proceed more rapidly than that of the 3-hole nozzle spray.

Intermittent Atomization Characteristics of Multi-Hole and Single-Hole Diesel Nozzle

Jeekuen Lee,Shinjae Kang,Byungjoon Rho 대한기계학회 2002 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.16 No.12

The intermittent spray characteristics of a multi-hole and a single-hole diesel nozzle were experimentally investigated. The hole number of the multi-hole nozzle was 5, and the hole diameter of the 5-hole and the single-hole nozzle was the same as dn=0.32 mm with the constant hole length to diameter ratio (l_n/d_n=2.81). The droplet diameters of the spray, including the time-resolved droplet diameter, SMD (Sauter mean diameter) and AMD (arithmetic mean diameter), injected intermittently from the two nozzles into the still ambient were measured by using a 2-D PDPA (phase Doppler particle analyzer). Through the time-resolved evolutions of the droplet diameter, it was found that the structure of the multi-hole and the single-hole nozzle spray consisted of the three main parts : (a) the leading edge affected by surrounding air and composed of small droplets ; (b) the central part surrounded by the leading edge and mixing flow region and scarcely affected by the resistance of air; (c) the trailing edge formed by the passage of the central part. The SMD decreases gradually with the increase in the radial distance, and the constant value is obtained at the outer region of the radial distance (normalized by hole diameter) of 7-8 and 6 for the 5-hole and single-hole nozzle, respectively. The SMD along the centerline of the spray decrease shapely with the increase in the axial distance after showing the maximum value near the nozzle tip. The SMD remains the constant value near the axial distance (normalized by hole diameter) of 150 and 180 for the 5-hole and the single-hole nozzle, respectively.

밸브 닫힘각 변화에 따른 버터플라이밸브의 손실계수 평가

이지근(Jeekeun Lee),노병준(Byungjoon Rho),최희주(Heejoo Choi) 한국항공우주학회 2008 韓國航空宇宙學會誌 Vol.36 No.1

밸브 디스크 직경이 25.4 ㎜ 인 소형 버터플라이밸브의 유동특성이 다양한 밸브 닫힘각에 대해 실험적으로 연구되었다. 밸브 디스크각이 작은 경우 유량조절특성을 향상시키기 위해 주어지는 밸브 닫힘각을 0°, 5°, 10°, 20°, 30°로 변화시켜 밸브 디스크각에 따른 손실계수를 측정하였다. 또한 밸브선단 형상이 손실계수 변화에 미치는 영향을 조사하였다. 밸브 닫힘각이 증가함에 따라 최대손실계수는 감소하며, 밸브 닫힘각 0°~5°에서 가장 큰 감소를 나타냄을 알 수 있었다. 밸브 디스크 형상에 따른 손실계수는 밸브 닫힘각이 0°인 경우 날카로운 모서리를 갖는 디스크가 더 큰 손실계수를 나타낸 반면, 닫힘각 10°의 경우 날카로운 모서리를 갖는 디스크의 경우가 더 낮은 손실계수를 나타냄을 알 수 있었다. In this study, flow characteristics of a small-sized butterfly valve with the valve disk diameter of 25.4 ㎜ have been investigated experimentally for the valve closed angles. In order to examine the flow characteristics of the butterfly valve, loss coefficient (K<SUB>v</SUB>) was obtained at the valve closed angles of 0°, 5°, 10°, 20° and 30°. In addition, the effects of the valve disk edge shape were examined. As the result of the experiment, the maximum loss coefficient (K<SUB>vmax</SUB>) was decreased with the increase of the valve closed angle, and it had the maximum decrease ratio at the valve disk angles of 0°~5°. The valve disk edge shape have an effect on the loss coefficient of the valve around the small valve closed angle.

DEA 방법론을 이용한 온라인 판매자 추천 시스템의 구축

안정남(Jungnam An),노상규(Sangkyu Rho),유병준(Byungjoon Yoo) 한국전자거래학회 2011 한국전자거래학회지 Vol.16 No.3

구매자와 판매자의 판매과정에서 ‘구매가치’는 구매자의 구매의사결정에 있어서 매우 중요한 가격대비 질의 중요한 측정치이다. 본 논문의 목적은 온라인 구매자들이 동일한 물건을 파는 판매자들 중에 최적 판매자를 선택하는 데 도움이 되는 방법론을 제안함에 있다. 이 방법론 수립을 위하여 DEA(data envelopment analysis) 방법론의 적용모형의 하나인 FDH(free disposal hull) 모형을 사용하고, 이 모형의 실효성을 실제 가격비교 사이트로부터 획득한 데이터를 이용하여 검증하였다. 모형 검증과정에서는 가격, 브랜드, 배달 기간 등 거래 조건에 대하여 구매자들이 어떻게 반응하는지를 우선 분석하고, 이를 바탕으로 구매자의 구매 의사결정을 돕는 판매자 추천 시스템을 구축하였다. 본 연구를 통하여 검증된 FDH 모형은, 구매자 측면에서 최적조건, 최저가로 좋은 제품과 서비스를 원하는 구매자에게 유용한 정보를 제공하고, 나아가 자동화된 소규모 거래에도 활용될 수 있을 것으로 기대된다. 판매자 측면에서는, 구매자의 선호도를 더욱 자세히 파악함으로써 타판매자 대비 경쟁력을 가지는 벤치마킹 전략을 수립하는 데에도 유용하게 이용될 수 있을 것으로 기대된다. In a buyer-seller transaction process, ‘value for money,’ a measure of quality-priceratio, is one of the most important criteria for buyers’ purchasing decisions. The purpose of this paper is to suggest a method which helps online shoppers choose the best of several sellers offering homogeneous goods. We suggest FDH (free disposal hull) model, an applied model of data envelopment analysis (DEA), for online buyer-seller transactions and verify it with the data from an Internet comparison shopping site. For this purpose, we analyze consumer choice behaviors by examining how consumers respond to different sale conditions such as price, brand, or delivery time. Then, we implement a seller recommendation system to support buyers’ purchasing decisions. We expect our FDH model to provide valuable information for rational buyers who want to pay the least price for high quality products/services and to be used in implementing automated evaluation processes in micro transactions. Moreover, we expect that our results can be utilized for sellers’ benchmarking strategies which help sellers be more competitive by showing them how to attract buyers.

이중 공기공급 이유체 선회노즐의 유량비 변화에 따른 미립화 특성에 관한 실험적 연구

강신명(Shinmyoung Kang),이지근(Jeekeun Lee),노병준(Byungjoon Rho) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10

The regulations to reduce the exhaust emissions from vehicles are becoming increasingly stringent and encompassing more types of vehicles. In the case of heavy duty diesel engines, the Urea-SCR system is currently considered to reduce the NOx emission as a proved technology, and it is widely studied to get the high performance and durability. In the Urea-SCR system, urea-water solution is injected into the exhaust pipe using the specially designed nozzle with high precision dosing unit. However, the injection nozzles occur some problems, including nozzle clogging, deposition of urea-water solution on the inner wall of exhaust pipe. In this study, the atomization characteristics of the dual air supplying twin-fluid swirl nozzle were investigated experimentally using PIV and PDA systems. The effect of assist air flowrate supplying from the dual air port was investigated. The mean velocity, turbulent intensity and SMD distributions of the sprays were measured along the centerline and radial direction. As the experimental results, the higher axial velocity is observed in the central part of the spray, and the SMD decreased with the increase of ALR.

환기용 축류팬의 가이드핀 블레이드 형상변화에 따른 유동특성에 관한 연구

박홍광(Hongkwang Park),이지근(Jeekeun Lee),노병준(Byungjoon Rho) 대한설비공학회 2007 설비공학 논문집 Vol.19 No.12

The effects of a guide fin blade on the flow characteristics in a ventilating axial fan were investigated experimentally. The guide fins were setup onto the pressure surface of the blade, and their effects on the flowrate were evaluated. Two types of the guide fin blade were designed. One is the stem fin blade, and the other is the radial fin blade. The stem fin is designed normal to the circumference of a circle, and the radial fin is designed along the circumference of a circle. The results from the guide fin blade fans are compared with that of the blade without guide fins. The position and the geometry of the radial fin setting up on the blade have an effect on the increase of flowrate with the minor sacrifice of rotational speed of the blades. The radial fin positioning at 0.84 times blade diameter shows highest performance in the flowrate. The increase of the blade weight resulting from applying the guide fins shows minor effect on the variation of rotational speed of the blades.

흡입공기분류를 가로지르는 가솔린 분무의 유동특성 연구

김원태(Wontae Kim),강신재(Shinjae Kang),노병준(Byungjoon Rho) 한국자동차공학회 1999 한국 자동차공학회논문집 Vol.7 No.9

When a fuel was injected with opening the intake valve of a port fuel injection engine, the spray atomization and flow characteristics in the intake port have a strong influence on the mixture formation of a combustion chamber. Thus, this study was to clarify the spray flow characteristics of the air-assist gasoline spray with fine droplets across the suction air stream in model intake port. For the simulated opening intake valve in port, suction air stream was varied to 10 m/s ~ 30 m/s. And fuel pressure was fixed to 300 kPa, but air assist pressure was varied to 0 ~ 25 kPa for a variable spray conditions. Spray flow trajectory was investigated by means of laser sheet visualization and the measurements of droplet sizes and velocities were made by PDPA system. Measured droplets within the spray flow field were subdivided into five size groups and then, the flow characteristics of droplet size groups were investigated to the spray across a suction air stream.