ATOMIZATION AT ULTRA-LOW LIQUID FLOW RATE USING NOVEL INJECTOR

( Mohammed Asad ),( Hrishikesh Gadgil ),( Sudarshan Kumar ) 한국액체미립화학회 2017 한국액체미립화학회 학술강연회 논문집 Vol.2017 No.-

Efficient atomization and evaporation at ultra-low flow rates is an additional challenge for small-scale combustion application since the atomization efficiency deteriorates with decreasing liquid flow rate. Experimental study at ultra-low liquid flow rate (5 - 150 mlph) unveiled the three distinct atomization regimes while air flow rate increases from 0.5 to 5 slpm. For a given ultra-low liquid flow rate, significant shift in injector characteristic was observed with increase in air flow rate; from bubble bursting to weak spray and finally at high air to liquid ratio, recirculation of atomizing air into a liquid tube gives fully developed spray. Injector is designed such that it allows co-flow air to flow back into a liquid tube. Internal flow analysis on Plexiglas injector replica shows that atomization regimes exist due to distinct two phase flow interaction inside the injector. Current study shows that critical air to liquid ratio at which air back flow triggers, decreases as liquid flow rate increases from 5 to 150 mlph. In weak spray regime, atomization occurs through prompt mode of atomization. While two phase slug flow formation inside the liquid tube leads to fine atomization in fully developed spray regime. Shadowgraphy experimental results validate the larger droplet in weak spray regime and fine atomization in fully developed spray regime due to formation of two phase slug flow. A proposed theoretical correlation shows that droplet size (SMD) is only function Reynolds number, Weber number, air to liquid ratio and injector design.

중수로 원전 핵연료 교체 보조기구 개발

이선기(S. K. Lee),이상국(S. G. Lee),박성근(S. K. Park),노영진(Y. J. Rho) 한국동력기계공학회 2008 한국동력기계공학회 학술대회 논문집 Vol.2008 No.11

The CANDU type reactors require on power refuelling by the two remotely controlled fuelling machines. The refuelling operation is carried out along the coolant direction by the drag force of fuel bundles for most channels. However, for about 30% of channels the coolant flow is not sufficiently high enough to carry fuel bundles to the downstream. Therefore, a device, FARE (Flow Assist Ram Extension) device, is used to create an additional drag force to push the fuel bundles along the coolant flow. The FARE device has been causing the channel flow low phenomena of channels due to more than excessive blockage of coolant flow. The flow rate change for the channels is monitored on line for the coolant flow blockage of the channels. This has initiated the investigation of the FAKE device behavior and the cause and remedy for the problem. The analysis revealed that the channel flow low occurs as the insertion of the FARE device into the active core flow and disappears as the removal of the FARE device from it. In order to eliminate the channel flow low phenomena, flow resistance by the FARE device should be reduced. The analysis has revealed that a too much relaxation of flow resistance would make the FARE device unable to push the fuel bundle string, and a too little relaxation would make the FARE device unable to eliminate the channel flow low phenomena. Suggested design changes include more flow holes in the tube.

Discharge characteristics at the control point for rainfall runoff model application

Hwang, Man H.,Maeng, Seung J.,Lee, Sang J.,Lee, Bae S.,Koh, Ick H. John Wiley Sons, Ltd. 2009 IRRIGATION AND DRAINAGE - Vol.58 No.4

<P>To manage and distribute water resources efficiently, a rainfall runoff model must be selected and established. To determine the appropriations for this rainfall runoff model, however, accurate flow data must first be obtained. Thus, in this study, the simulated flow of Korea's Geum River was compared with the observed flow at Gongju point, a main control point, using the Streamflow Synthesis and Reservoir Regulation (SSARR) model. The results obtained showed a huge difference between the simulated and observed flows during the low flow period. To determine what caused this difference, a confidence analysis of the formula of the stage discharge curve at Gongju point, developed by the Ministry of Construction and Transportation's Geum River Flood Control Office, was conducted. The flow during the low flow period (between 2003 and 2005) was also measured, and the value obtained was compared with the simulated flow. The long-term flow as low flow was also calculated, through runoff component analysis, to determine the hydraulic characteristics of the control point and to examine the runoff characteristics during the low flow water utilization seasons.</P><P>The study results show that during the low flow period (between 2003 and 2005), the simulated flow (based on the SSARR model) approximated the long-term flow (based on the runoff component analysis).</P><P>The results, however, also show that the observed flow, according to the stage discharge curve formula developed by the Geum River Flood Control Office, was overestimated by about 10% up to 20% both during the normal water level and drought seasons, due to hydraulic factors caused by the spatial characteristics of Gongju point, a main control point. The results of the study reveal that the estimation of the flow must be corrected, and that such flow must be continuously monitored. Copyright © 2008 John Wiley & Sons, Ltd.</P>

일시적 혈류 제한과 함께 수행한 저강도 운동 후 알파운동신경원의 변화

김종순 ( Jong Soon Kim ) 대한물리의학회 2015 대한물리의학회지 Vol.10 No.1

PURPOSE: Low-intensity exercise with transient restriction of blood flow to muscle could be an alternative rehabilitation method which avoids the problems associated with conventional high-intensity exercise. However, the mechanism of low-intensity exercise with transient restriction of blood flow is not clearly known. Thus, the purpose of this study was to investigate the mechanism of improvement of muscular function after low-intensity exercise with transient restriction of blood flow using H-reflex analysis. METHODS: Twenty one healthy young adults with no medical history of neurological or musculoskeletal disorder voluntarily participated in this study. The α-motor neuron excitability of the triceps surae was assessed using the H-reflex. The amplitude of the M-wave and H-reflex were measured across three conditions: rest, after low-intensity exercise without restriction of blood flow and after low-intensity exercise with restriction of blood flow. The subjects performed low-intensity ankle plantar flexion exercise at their own pace for one minute without or with transient restriction of blood flow achieved by a sphygmomanometer cuff on popliteal fossa at a pressure of 120㎜of mercury(120 ㎜Hg). RESULTS: No significant changes of the excitability of the α-motor neuron were obtained across three different conditions. CONCLUSION: This study found that low-intensity exercise with transient restriction of blood flow did not influence to α-motor neuron excitability of the triceps surae. From the results, I could come to the conclusion that further study will be required.

천연가스의 계절별 변동유량을 고려한 이중터보팽창기 감압시스템을 이용한 전기에너지회수에 관한 연구

박철우,유한빛,김효 한국가스학회 2019 한국가스학회지 Vol.23 No.2

천연가스 운송기지에서 전기에너지를 회수하기위하여 팽창 터빈시스템을 사용하는 것은 잘 알려진 기술이다. 터보팽창기의 효율은 천연가스의 유량과 터보팽창기 설계유량의 비에 따라 달라진다. 그러나 감압기지에서 계절적 공급패턴, 즉 여름에는 낮은 유량으로 반면에 겨울에는 높은 유량으로 공급되기 때문에, 단일 터보팽창기로는낮은 유량의 천연가스로부터 감압에너지를 충분히 회수하기가 비효율적이다. 따라서 본 연구에서는 대용량과 소용량의 이중 터보팽창기의 새로운 개념을 제안하게 되었다. 본 연구에서는 저압 정압기지에서 팽창밸브의 평균 입구, 출구 압력조건인 18.5 bar에서 7.5 bar로 감압될 때 입구의 온도, 유량조건에 따라서 생산 가능한 전력을 이론적배경을 통해 계산하였다. 최저 설계 효율 0.72에서 회수 가능한 전력생산량은 단일 터보팽창기로 운전될 때에는12.4 MW이었으나, 여기서 제안한 이중터보팽창기에서는 16.1 MW로 약 30% 증가한 결과를 얻게 되었다. Expansion turbine system to recover the electricity energy from natural gas transmission stations is a well-known technique. The turbo-expander efficiency depends on the ratio of the natural gas flow rates to the design flow rate of the turbo-expander. However, if there is a big difference of the natural gas flow rate through the pressure letdown station because of seasonal supply pattern, that is, high flow rate in winter while low flow rate in summer, single turbo-expander system is not so efficient as to recover the pressurized energy from the low flow-rate natural gas. Therefore, we have proposed a new concept of double turbo-expander system: one is a big capacity and the other a small capacity. Here we have theoretically computed the electric powers at the pressure reduction from 18.5 bar to 7.5 bar depending on the inlet conditions of temperature and flow rate. The calculated electricity generation has been increased by 30% from 12.4 MW in a single turbo expander to 16.1 MW in the proposed double turbo-expander system when a minimal design efficiency of 0.72 is applied.

Effect of taper on fundamental aeroelastic behaviors of super-tall buildings

Kim, Yong Chul,Tamura, Yukio,Yoon, Sung-Won Techno-Press 2015 Wind and Structures, An International Journal (WAS Vol.20 No.4

Aeroelastic wind tunnel experiments were conducted for conventional and tapered super-tall building models to investigate the effect of taper on fundamental aeroelastic behaviors in various incident flows. Three incident flows were simulated: a turbulent boundary-layer flow representing urban area; a low-turbulent flow; and a grid-generated flow. Results were summarized focusing on the effect of taper and the effect of incident flows. The suppression of responses by introducing taper was profound in the low-turbulence flow and boundary-layer flow, but in the grid-generated flow, the response becomes larger than that of the square model when the wind is applied normal to the surface. The effects of taper and incident flows were clearly shown on the normalized responses, power spectra, stability diagrams and probability functions.

Effect of taper on fundamental aeroelastic behaviors of super-tall buildings

김용철,Yukio Tamura,윤성원 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.20 No.4

Aeroelastic wind tunnel experiments were conducted for conventional and tapered supertallbuilding models to investigate the effect of taper on fundamental aeroelastic behaviors in variousincident flows. Three incident flows were simulated: a turbulent boundary-layer flow representingurban area; a low-turbulent flow; and a grid-generated flow. Results were summarized focusing on theeffect of taper and the effect of incident flows. The suppression of responses by introducing taper wasprofound in the low-turbulence flow and boundary-layer flow, but in the grid-generated flow, theresponse becomes larger than that of the square model when the wind is applied normal to the surface. The effects of taper and incident flows were clearly shown on the normalized responses, power spectra,stability diagrams and probability functions.

호흡계질환이 동반된 척추골절로 인해 장기간 침상 안정을 유지한 고령의 환자에게 저유량 비강 캐뉼라 산소요법과 병행한 저강도 운동치료가 보행 향상에 미치는 영향

류흥호(Hung-Ho Ryou) 대한심장호흡물리치료학회 2021 대한심장호흡물리치료학회지 Vol.9 No.1

Purpose: In this case study, we aimed to examine the effects of low-flow nasal oxygen therapy during a low-intensity exercise intervention on the gait improvement of a patient with thoracic vertebral fracture and respiratory disease. Methods: An old patient with thoracic vertebral fracture and respiratory disease received low-flow nasal oxygen therapy during low-intensity (Borg scale, 3-4) exercises (e.g., tilting table, walker standing, and walker gait) for 4 weeks. Results: We found that the patient could breathe on her own in room air during independent gait with a walker. Conclusion: Low-flow nasal cannula oxygen therapy during a low-intensity exercise intervention improved general weakness and strengthened respiratory muscles as well as shortened the period of oxygen therapy.

시계열 항공사진의 정밀 기하보정에 의한 저수로 변화 모니터링

엄대용 韓國交通大學校 2013 한국교통대학교 논문집 Vol.48 No.-

This study would like to verify the utilization possibility of the time-series-analysis method on aerial images in order to efficiently analyze the changes of low-flow in the river in progressing over the long term. For this purpose, acquisited time-series aerial images for study river area and performed the precise geometric correction for each image. The low-flow and river boundaries were extracted by edge detection method from images that precise geometric correction is completed by year. And, the extracted boundaries were vectorized and three-dimensional coordinates were obtained for low-flow and river boundary by overlapping with cross-sectional data. Then, analyzed the change of low-flow using these coordinates. As a result, could effectively analyze the change of low-flow that it has been in progress for a long period of time through the time-series analysis of aerial images.

회귀모형을 이용한 전북지역 미계측 유역의 저유량 해석

조기태,박영기,이장춘 한국환경과학회 2000 한국환경과학회지 Vol.9 No.1

The purpose of this study is to estimate the low-flow statistics at the mountainous watershed. The formulation for the estimation of the design low-flow statistics was obtained by means of a hydraulic approach applied to a simple conceptual model for a mountainous watershed. Three of the independent variables associated with the low-flow statistics is watershed area(A), average basin slope(S) and the base flow recession constant(K); Watershed area was measured from topographic maps and average basin slope is approximated in this study using Strahler's slope determining method. And base flow recession constant computed using Vogel and Kroll's method. Unfortunately, this method is usually unavailable at ungaged sites. In this study, recession constant at ungaged sites is estimated using graphical regression method used by Giese and Mason. The model for estimating low-flow statistics were applied to all 61 catchments in the Sumjin, Mankyung basin.