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타원형 노즐을 이용한 횡단류 유동에서 액체제트 특성 연구
송윤호(Yoonho Song),황동현(Donghyun Hwang),안규복(Kyubok Ahn) 한국추진공학회 2017 한국추진공학회 학술대회논문집 Vol.2017 No.5
아음속 공기유동으로 수직분사하는 액체제트에 대하여 오리피스 형상이 달라질 경우, 분무특성에 어떠한 영향을 미치는지 실험적으로 연구하였다. 서로 다른 오리피스 길이 대 직경비와 타원형 노즐의 종횡비를 갖는 분사기들을 제작하여 수직분사 실험을 진행하였다. 원형노즐과 타원형 노즐에서의 분열길이를 비교하였으며, 타원형 노즐에서의 분열길이는 모든 실험조건에서 원형노즐에 비해 줄어들었다. 캐비테이션과 수력튀김 현상이 분사기 내부에 발달되는 분무차압 조건의 경우, 두 노즐 모두 분열길이가 감소하였다. 액주궤적의 경우, 장축으로부터 분무되는 액체제트가 횡방향 공기유동에 수직으로 부딪혀 나가는 경우가 액주의 궤적이 단축에 비해 더 휘어지며, 침투높이가 낮아진다. Effect of elliptical orifice on the spray characteristics of liquid jet ejecting into subsonic crossflows were experimentally studied. Circular/elliptical plain-orifice injectors, which had different ratios of the orifice length to diameter and major axis to minor axis, were used for transverse injection. Compared with the previous research, breakup lengths of elliptical nozzles are shorter than circular nozzles at all experimental condition. Cavitation/hydraulic flip are considered as a reduction in the breakup length at all circular/elliptical nozzle. In the case of liquid column trajectories, major axis which was placed to the crossflows, increases the frontal area of the liquid column exposed to the crossflows. Hence, the aerodynamic force exerted on the jet is increased and the penetration depth is reduced.
송윤호(Yoonho Song),황동현(Donghyun Hwang),왕가흠(Kexin Wang),안규복(Kyubok Ahn) 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.12
본 연구는 횡방향으로 유입되는 공기유동에 음향가진을 주었을 때, 액체 제트의 액적 분열과 액주 궤적에 어떠한 영향을 미치는지 파악하고자 하였다. 이를 위해서 단공 노즐을 이용하여 동일 횡단류 공기유동 속도와 서로 다른 액체 분사압력에 따라 실험을 진행하였다. 실험에 사용된 가진 주파수는 320 Hz로써, 주파수 기준 12개의 위상각에서 이미지를 얻기 위해 고속카메라의 trigger rate를 3,840 Hz로 설정하였다. 액주의 궤적과 분열길이는 분사기와 연소기를 설계하는데 있어 가장 중요한 요소이기 때문에, 앞서 얻은 분무 이미지를 바탕으로 궤적과 분열길이를 분석하였다. 횡방향에서의 공기유동에 가진 할 경우, 가진 하지 않았을 때 보다 전체적으로 x, y 방향에서의 액적 분열을 촉진 시키는 결과를 볼 수 있었다. 동일한 분사압력에서 위상각에 따른 분열길이를 보면, 각각의 위상각에서 주기적인 형태의 분열길이는 확인되지 않았지만 전체적으로 분열길이가 감소한 것을 볼 수 있었다. Effects of acoustic forcing on the spray characteristics of liquid jet in subsonic crossflow were experimentally studied. By changing injection pressure at a fixed velocity of subsonic crossflow, liquid column breakup lengths/trajectories, which were believed to be important for designing injector and combustor, were measured using a high-speed digital camera. The test section is excited by an acoustic frequency of 320 Hz. To obtain images at 12 phase angles, the trigger rate of the high-speed camera was set to 3,840 Hz. The experiments in non-excited condition showed similar results with previous research data which had approximately 8 of the breakup length to diameter. However, breakup length decreased in the case of exciting air crossflow in the test section.
횡단류 유동에서 오리피스 형상에 따른 액체제트의 분무특성
송윤호 ( Yoonho Song ),안규복 ( Kyubok Ahn ) 한국액체미립화학회 2016 한국액체미립화학회 학술강연회 논문집 Vol.2016 No.-
Effects of orifice geometry on the spray characteristics of liquid jet ejecting into subsonic crossflow were experimentally studied. Two circular and four elliptical plain orifices with various ratios of the orifice length to the orifice diameter were used. The diameter of circular orifices and the minor axis of elliptical orifices is 0.5 mm. The ratios of the major axis to the minor axis in elliptical orifices are 2 and 3, respectively. The velocity of subsonic crossflows was approximately 50 m/s. By changing injection pressure from 1 bar to 6 bar, liquid column breakup lengths and liquid column trajectories, which were believed to be important for designing injector and combustor, were measured using a high-speed digital camera (Vision Research, Phantom v9.1). The experiments in circular orifices showed similar results with previous research data which had approximately 8 of the breakup length to the orifice diameter. Regardless of both major axis and minor axis, the experiments in elliptical orifices showed that liquid column trajectories in non-cavitation flow and cavitation flows had a nearly similar trend but liquid column trajectories in hydraulic flip flows had different results. It is thought to be that the surface of the liquid jet in hydraulic flip flows was detached form the inner wall of the orifice exit. When cavitation developed inside the sharp-edged orifice, the liquid jet became more unsteady and turbulent so that hydraulic flip flow and cavitation flow caused the breakup lengths to decrease in both circle and elliptical orifices. However, there was no difference between major axis and minor axis breakup lengths in elliptical orifices because the elliptical liquid jet emerging from the orifice exit tended to become circular. Although the liquid jet cross-sectional shape of the elliptical orifice by the direction of major axis or minor axis to the crossflows was different in the vicinity of the orifice exit, the liquid jet downstream of the exit was considered to have been not significantly affected by the direction of the elliptical orifice.
송윤호 ( Yoonho Song ),안규복 ( Kyubok Ahn ) 한국액체미립화학회 2018 한국액체미립화학회지 Vol.23 No.1
Breakup lengths of circular and elliptical liquid jets in a subsonic crossflow were experimentally studied. Two circularshaped and four elliptical-shaped plain-orifice injectors, which had different aspect ratios and orifice length to diameter ratios, were used to provide various liquid jet conditions such as steady, cavitation, and hydraulic flip. By varying the injection pressure drop from 1 bar to 6 bar, spray images were taken using a shadowgraph technique. Breakup lengths were measured and analyzed. As the aspect ratio in orifices increased, liquid column breakup lengths normalized by the equivalent diameter were reduced irrespectively of the switching of the major or minor axis to the crossflow. It was also found that when hydraulic flip developed inside the orifice, x-directional breakup lengths more decreased for both circular and elliptical liquid jets.
송윤호(Song, Yoonho),이태종(Lee, Tae-Jong),김형찬(Kim, Hyoung-Chan) 한국신재생에너지학회 2005 한국신재생에너지학회 학술대회논문집 Vol.2005 No.06
KIGAM (Korea Institute of Geoscience and Mineral Resources) launched a new project to develop the low-temperature geothermal water in the area showing high geothermal anomaly, north of Pohang city, for large-scale space heating. Surface geologic and geophysical surveys including Landsat 1M image analysis, gravity, magnetic, Magnetotelluric (MT) and controlled-source audio-frequency MT (CSAMT), and self-potential (SP) methods have been conducted and the possible fracture zone was found that would serve as deeply connected geothermal water conduit. In 2004, two test wells of 1.1km and 1.5km depths have been drilled and various kinds of borehole survey including geophysical logging, pumping test, SP monitoring, core logging and sample analysis have followed. Temperature of geothermal water at the bottom of 1.5km borehole reached over 70?C and the pumping test showed that the reservoir contained huge amount of geothermal water. Drilling for the production well of 2 km depth is on going. After test utilization and the feasibility study, geothermal water developed from the production well is going to be provided to nearby apartments.
우리나라 지열발전 pilot plant 프로젝트의 발전량 추정
송윤호(Song, Yoonho),이태종(Lee, Tae Jong),윤운상(Yoon, Woon Sang) 한국신재생에너지학회 2011 한국신재생에너지학회 학술대회논문집 Vol.2011 No.05
Target generation capacity of geothermal power generation pilot plant project through the Enhanced Geothermal Systems (EGS) with a doublet system down to 5 km depth was estimated. Production and re-injection temperatures of geothermal fluid were assumed 160?C and 60?C, respectively, based on reservoir temperature of 180?C calculated from the geothermal gradient of 33?C in Pohang area. In this temperature range, 0.11 of thermal efficiency of the binary generation cycle is a practical choice. Assuming flow rates of 40 kg/sec, which is possible in current EGS technology, gross power generation capacity is estimated to reach 1.848 MW. Net generation considering auxiliary power including pumping power for geothermal fluid and condensing (cooling) energy of working fluid can be 1.5 MW.
Assessment of Geothermal Power Generation Potential According to EGS Potential Protocol
송윤호(Song, Yoonho),백승균(Baek, Seung-Gyun),김형찬(Kim, Hyoung Chan),이태종(Lee, Tae Jong) 한국신재생에너지학회 2011 한국신재생에너지학회 학술대회논문집 Vol.2011 No.11
We have estimated power generation potential in Korea following the recently announced EGS protocol. According to the protocol, we calculated the theoretical potential first, which assumes 30 year operation, minimum temperature being surface temperature+80?C, depth range being from 3 km to 10 km. In this new assessment the in-land area was digitized by 1' by 1' blocks, which is much finer than suggestion of the protocol (5'by 5'). Thus estimated theoretical potential reaches 6,975 GWe which is 92 times of the total power generation capacity in 2010. In the estimation of technical potential, we limited the depth range down to 6.5 km, assumed recovery factor as 0.14 and also counted for temperature drawdown factor of 10?C following the protocol. Accessible in-land area excluding steep mountains, residence and industrial region, wet area and others covers 40.7% of total area. Finally, we could come up with 19.6 GWe for technical potential, which would be 56 GWe if we do not account for the temperature drawdown factor. These are important results in that we made the first potential assessment for geothermal power generation.