반고형제제의 유동특성에 관한 연구 (제2보) : 바셀린의 온도의존성 유동거동

김정화(Jeong Hwa Kim),송기원(Ki Won Song),장갑식(Gap Shik Chang),이장우(Jang Oo Lee),이치호(Chi Ho Lee) 대한약학회 1997 약학회지 Vol.41 No.1

Using a concentric cylinder type, rheometer. the steady shear flow properties of vaseline were measured over the temperature range of 20~70oC. In this paper, the shear rate and temperature dependencies of its flow behavior were investigated and the validity of some flow models was examined. In addition, the flow characteristics over a wide temperature range were quantitatively evaluated by calculating the various material parameters. Main findings obtained from this study can be summarized as follows: (1) At relatively lower temperature range, vaseline is a plastic fluid with a yield stress and its flow behavior shows shear-thinning characteristics. (2) As the temperature increases, the value of a yield stress and the degree of shear-thinning become smaller, consequently, the Newtonian flow behavior occurs at a lower shear rate range. (3) At temperature range lower than 45oC, the flow behavior shows much stronger temperature dependence, and a larger activation energy is needed for flow. (4) The Herschel-Bulkley model is the most effective one g3 to predict the flow behavior of vaseline having a yield stress. The validity of the Bingham and Casson models becomes more available with increasing temperature. The flow behavior of vaseline at temperature range higher than 45oC can be perfectly described by the Newton model.

Flow characteristics and rheological properties of propane hydrate slurry

Ryosuke Uchida,Takashi Morimoto,Hiroyuki Kumano 대한설비공학회 2018 대한설비공학회 학술발표대회논문집 Vol.2018 No.6

Numerical result of complex quick time behavior of viscoelastic fluids in flow domains with traction boundaries

권영돈 한국유변학회 2007 Korea-Australia rheology journal Vol.19 No.4

Here we demonstrate complex transient behavior of viscoelastic liquid described numerically with theLeonov model in straight and contraction channel flow domains. Finite element and implicit Euler time inte-gration methods are employed for spatial discretization and time marching. In order to stabilize the com-putational procedure, the tensor-logarithmic formulation of the constitutive equation with SUPG andDEVSS algorithms is implemented. For completeness of numerical formulation, the so called tractiondirection with stress free condition is allocated whereas the traction free boundary is assigned at the outlet.The numerical result has illustrated severe forward-backward fluctuations of overall flow rate in inertialstraight channel flow ultimately followed by steady state of forward flow. When the flow reversal occurs,the flow patterns exhibit quite complicated time variation of streamlines. In the inertialess flow, it takesmuch more time to reach the steady state in the contraction flow than in the straight pipe flow. Even in thehave been observed such as appearing and vanishing of lip vortices, coexistence of multiple vortices at thecontraction corner and their merging into one.

수치해석에 의한 플러그 밸브의 유량계수 산출 방법 평가 검증 및 유량특성 평가

김민경(MinKyung Kim),정준환(JunHwan Jung),김성재(SeongJae Kim),이재훈(JaeHoon Lee) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4

일반적으로 밸브 성능 검증을 위해 실험적인 방법을 통해 유량계수(Cv)를 측정하고 있으나, 시험설비의 한계로 인해 시험 가능한 밸브가 제한적이고 다양한 케이스에 대한 시험비용의 증가에 대한 문제도 발생한다. 특히 플러그 밸브의 경우 개폐 정도에 따른 유량계수의 측정이 필요하나 시간적, 비용적 한계로 인해 성능 검증 시험을 수행하기에 많은 어려움이 발생한다. 이에 대한 대안으로 많은 밸브 제조기업에서 수치해석을 활용하여 실험값을 대체하고 개발에 참고하고 있다. 국내 밸브업체의 경우 대부분 국제규격 측면에서 제품을 설계, 생산하고 있으며 내압강도와 기밀시험과 같이 구조적인 문제를 해결하는데 개발의 초점을 두고 있다. 반면, 유동특성과 유량계수의 산출과 같이 시스템 내부의 설계인자를 복합적으로 고려한 성능검증 절차의 경우 구조적 특성에 비해 소극적으로 개발 및 검증하고 있다. 또한, 역설계 제품의 경우 시간적, 비용적 문제로 인해 별도의 실험을 진행하여 검증을 하지 않는 것이 현실이다. 산업용 밸브의 경우 운전 특성과 작동 환경에 따라 유량과 압력 등이 달라지므로 밸브 자체에 대한 특성파악이 개발에 있어 중요한 요소 중 하나이다. 본 연구는 산업적으로 많이 사용되고 있는 플러그밸브에 대한 유량계수를 수치해석의 방법으로 산출하고 Full Open 상태에서의 유량계수 실험값과 결과를 비교하여 수치해석적 방법을 통한 산출방법에 대한 신뢰성을 확보한다. 그 후 밸브의 개폐 정도에 따른 유량계수를 산출하고 유동특성을 분석하고자 한다. In general, the flow coefficient (Cv) is measured through an experimental method to verify the valve performance, but due to the limitations of the test facility, the type of valves that can be tested is limited, and the problem of increasing the test cost for various cases also arises. In the case of a plug valve, it is necessary to measure the flow coefficient according to the degree of opening and closing, but it is difficult to perform a performance verification test due to time and cost limitations. As an alternative to this, many valve manufacturers use numerical analysis to replace experimental values and refer to them for development. Most of the domestic valve companies design and manufacture products in terms of international standards, and their development focuses on solving structural problems such as pressure resistance and leak tests. On the other hand, in the case of a performance verification procedure that complexly considers the design factors inside the system, such as calculation of flow characteristics and flow coefficients, it is passively developed and verified compared to structural characteristics. Also, in the case of reverse engineered products, due to time and cost issues, tests are not conducted and verified. In the case of industrial valves, since the flow rate and pressure vary depending on the operating characteristics, understanding the characteristics of the valve itself is one of the important factors in the development. In this study, the flow coefficient of the plug valve, which is widely used industrially, is calculated by the method of numerical analysis, and the reliability of the calculation method through the numerical analysis method is secured by comparing the experimental value and the result of the flow coefficient in the full open state. After that, the flow coefficient according to the degree of opening and closing of the valve is calculated and the flow characteristics are analyzed.

미분기의 미분탄관 오리피스의 유동특성에 관한 연구

최웅걸(Woongkirl Choi),전광호(Kwangho Chun),이은상(Eunsang Lee),조항덕(Hyangduck Cho),신시명(Simyeong Shin) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11

Boiler for thermal power generation are generally supplied air and fuel with air supply systems. And these air supply systems need flow contorl orifices to control air and fuel transfer path. The orifice plate is usually used to adjust the flow rate of air and fuel in thermal power generation. However, the orifice plate is difficult to control the air and fuel flow. Therefore, the orifice valve which can control the air and fuel flow is developed. It is widespread nowadays for thermal power generation, but the coal particles leak into the valve unit and gap which lead to a flow control failure. Spherical orifice which can overcome the shortcomings of orifice plate and orifice valve is designed and developed. In this study, computational fluid dynamics (CFD) analysis was carried out to clarify the flow characteristics of different types thermal power generation orifices with different opening and flow rates . Finally, we confirmed the spherical orifices advantages and usability relative to orifice plate and orifice valve.

Two-Fluid Urea-SCR 분무노즐의 유동특성 및 분무구조에 관한 실험적 연구

강신명(Shinmyoung Kang),김의수(Euisoo Kim),박설혜(Sulhye Park),이지근(Jeekeun Lee) 한국자동차공학회 2007 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-

Diesel engines are widely used in the modern industrial fields. However, the government regulations for environments are becoming increasingly stringent and encompassing more types of vehicles, such as diesel engines. The after-treatment system is a effective method to reduce the exhaust emission with keeping high efficiency of engine. The Urea-SCR system is the effective solution to reduce NOx among them. The injected urea-solution is converted into ammonia by heating the exhaust gas, then the ammonia is mixed with an exhaust gas. NOx is reduced by chemical reaction of the mixture. However, the non-reacted ammonia passes through the SCR system without chemical reaction so that the ammonia slip takes place. Therefore the precise control of urea-solution injecting from the nozzle is major factor of the Urea-SCR system. The spatial concentration and distributions of the spray, which determines the performance of the nozzle, are major factor in the Urea-SCR system. In this work, the flow and spray characteristics of the two-fluid Urea-SCR spray nozzle were measured with an air and liquid ratio(ALR). The variation of injection quantities is dependent upon a duty ratio, supplying liquid pressure and air flow-rate. Particularly, the flow-rate of carrier air is very important factor to determine the injection quantities. In addition, the spray structure;spray angle, penetration were measured using a PIV system.

노즐 팁 유로의 형상변화에 따른 분무의 거동특성에 관한 연구

고동국 대한기계학회 2024 大韓機械學會論文集B Vol.48 No.9

본 논문은 고속 살포 방제기(SS)에 사용되는 노즐의 국산화와 기술적 자립화를 확보하고 노즐의 교체주기를 효과적으로 개선하기 위해 방제노즐의 유로 형상이 분무의 거동에 미치는 영향을 해석적 방법을 통해 분석한 것이다. 해석변수는 노즐 팁의 유로 각도와 유로 수이다. 유로 각도가 60°이고 유로 수가 3개인 경우 분무의 형상은 중공형 액막을 형성하고 분무의 거동은 불규칙하였다. 유로 각도가 80°이고 유로 수가 3개인 경우에는 분무가 반경방향으로 넓고 고르게 확산되어 미립화 성능은 개선되었다. 유로 각도가 80°이고 유로 수가 6개인 경우 분무는 축방향으로 길게 토출되었다. This paper analyzes the effect of flow-path shape on the spray behavior of a speed-sprayer nozzle to secure the technological independence of nozzles and improve the nozzle-replacement cycle. The analysis variables were the flow-path angle and number of the nozzle tip. The shape of spray formed a hollow liquid film and the spray behavior was irregular when the flow-path angle and number were 60° and 3, respectively. The spray dispersed widely and uniformly in the radial direction when the flow-path angle and number were 80° and 3, respectively. Consequently, the atomization performance improved. The spray was ejected long in the axial direction when the flow-path angle and number were 80° and 6, respectively.

Investigation of the effect of adaptive characteristics on non-cavitating noise for flexible propeller in non-uniform flow via the fluid-structure interaction model

최요셉,홍석윤,송지훈 대한조선학회 2023 International Journal of Naval Architecture and Oc Vol.15 No.-

When constructing a low-noise submarine, it is crucial to consider the non-cavitating noise from the propeller. Non-cavitating noise reduction is crucial for submarine stealth and survivability. Recently, several studies have been conducted on the use of flexible propellers as a means of reducing noncavitating noise. However, there are no studies on the use of flexible propellers with adaptive characteristics to reduce noise inwake fields. Thus, this study investigated the noise reduction effect of adaptive characteristics on non-cavitating noise for the flexible propeller in the wake field. Numerical investigations on the main propeller variables were conducted based on the proposed procedure using fluid-structure interaction and acoustic analysis models. The results were compared with those of rigid propellers to determine the possible reasons for noise reduction. Finally, the acoustic analysis results of the flexible propeller were compared with those of the rigid propeller to reveal the effectiveness of the adaptive characteristics.

Numerical Investigation of the Effects of Primary Nozzle Diverging Portion on Performance of the Supersonic Ejector of an Ejector Refrigeration Cycle

Shaban Alyari Shourehdeli,Kamran Mobini,Ali Asakereh 대한설비공학회 2019 International Journal of Air-Conditioning and Refr Vol.27 No.3

A supersonic ejector with desirable performance characteristics reduces the energy consumption rate of an ejector refrigeration system and increases its coefficient of performance (COP). In this paper, the effects of using different primary nozzles on the performance of a supersonic ejector of an ejector refrigeration system have been numerically studied, while the working fluid is steam. To this end, conical, Rao and parallel-flow primary nozzles with identical converging portions and equal exit area to throat area ratios have been tested. The diverging portion curves for the parallel-flow and Rao nozzles were derived using the method of characteristics. Using the Rao nozzle, the critical entrainment ratio and the critical back pressure were increased compared to the conical nozzle by 6.3% and 2.08%, respectively. It was also found that the physics of the internal flow of the ejector was changed by changing the diverging curve of the primary nozzle.

Inverse design optimization of central outlet cap in land-based flow-through aquaculture system

Jongjae Lee(이종재),Inyeong Kwon(권인영),Taeho Kim(김태호),Sanghoon Kim(김상훈) 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.11