Effects of Relative Position between a Stator and a Rotor on Steam Condensing Flow in Rotating Machinery

Kim, Changhyun,Park, JaeHyeon,Baek, Jehyun Korean Society for Fluid machinery 2018 International journal of fluid machinery and syste Vol.11 No.1

Flow of steam is different from other gas flows and involves droplet generation in the flow field. This phase-transition affects not only flow aspects, but also machine performance in a negative way. These days, CFD is widely used in machine design and optimization processes, so phase-transition phenomena in steam flows should be considered in CFD to predict the internal flows precisely. In the past, non-equilibrium wet-steam model was implemented on in house code T-Flow and it was applied to steady calculations of a steam turbine model with changing stator/rotor interface. The results showed that mixing plane method is not appropriate to simulate steam condensing flow and frozen rotor method can be affected by relative position between a stator and a rotor. Therefore, steady wet-steam flows with non-equilibrium phase-transition were simulated for a steam turbine model in this study with 4 different stator-rotor positions and their effects on the wet-steam flow fields were investigated in detail.

Effects of Relative Position between a Stator and a Rotor on Steam Condensing Flow in Rotating Machinery

Changhyun Kim,JaeHyeon Park,Jehyun Baek 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.1

Flow of steam is different from other gas flows and involves droplet generation in the flow field. This phase-transition affects not only flow aspects, but also machine performance in a negative way. These days, CFD is widely used in machine design and optimization processes, so phase-transition phenomena in steam flows should be considered in CFD to predict the internal flows precisely. In the past, non-equilibrium wet-steam model was implemented on in house code T-Flow and it was applied to steady calculations of a steam turbine model with changing stator/rotor interface. The results showed that mixing plane method is not appropriate to simulate steam condensing flow and frozen rotor method can be affected by relative position between a stator and a rotor. Therefore, steady wet-steam flows with non-equilibrium phase-transition were simulated for a steam turbine model in this study with 4 different stator-rotor positions and their effects on the wet-steam flow fields were investigated in detail.

Effects of Relative Position between a Stator and a Rotor on Steam Condensing Flow in Rotating Machinery

김창현,박재현,백제현 한국유체기계학회 2018 International journal of fluid machinery and syste Vol.11 No.1

Flow of steam is different from other gas flows and involves droplet generation in the flow field. This phase-transition affects not only flow aspects, but also machine performance in a negative way. These days, CFD is widely used in machine design and optimization processes, so phase-transition phenomena in steam flows should be considered in CFD to predict the internal flows precisely. In the past, non-equilibrium wet-steam model was implemented on in house code T-Flow and it was applied to steady calculations of a steam turbine model with changing stator/rotor interface. The results showed that mixing plane method is not appropriate to simulate steam condensing flow and frozen rotor method can be affected by relative position between a stator and a rotor. Therefore, steady wet-steam flows with non-equilibrium phase-transition were simulated for a steam turbine model in this study with 4 different stator-rotor positions and their effects on the wet-steam flow fields were investigated in detail.

Numerical study of wet-steam flow in Moore nozzles

Santhosh Senguttuvan,이장창 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.10

Wet-steam flow is a two-phase mixture of vapor and tiny liquid droplets that occurs in the final stages of low pressure (LP) steam turbine process. These liquid droplets are formed by the non-equilibrium condensation of steam. This condensation of steam releases a significant amount of latent heat to the flow. As a result, the flow velocity is reduced and it affects the efficiency of the steam turbine. Since it is extremely difficult to perform numerical studies with the non-equilibrium condensation for turbines, they are usually done in convergent-divergent nozzles. In this paper, the effect of area ratio of the well-known Moore nozzles on the non-equilibrium condensation of steam is investigated numerically. The mathematical model for the non-equilibrium condensation is based on the classical homogeneous nucleation theory corrected with non-isothermal effects and Hill’s droplet growth law. The numerical results are successfully validated with the experimental data for Moore nozzle B. The numerical results represent that with increasing area ratio, the intensity of condensation decreases and the residue amount of liquid mass fraction in the flow field increases. Therefore, while designing the area ratio of the nozzle, the influences of both the condensation intensity and liquid mass fraction should be considered.

비평형 습증기 모델을 적용한 증기 응축 유동 해석

김창현(C.H. Kim),박재현(J.H. Park),고동건(D.G. Ko),김동일(D.I. Kim),김영상(Y.S. Kim),백제현(J.H. Baek) 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.3

When the steam is used as working fluid in fluid machinery, different from other gases as air, phase transition (steam condensation) can occur and it affects not only the flow fields, but also machine performance & efficiency. Therefore, considering phase transition phenomena in CFD calculation is required to achieve accurate prediction of steam flow and non-equilibrium wet-steam model is needed to simulate realistic steam condensing flow. In this research, non-equilibrium wet-steam model is implemented on in-house code(T-Flow), the flow fields including phase transition phenomena in convergent-divergent nozzle are studied and compared to results of advance researches.

습식 미분과 증미로 제조한 쌀조청의 특성

이정은,최윤희,조문경,박신영,김은미 한국식품영양학회 2012 한국식품영양학회지 Vol.25 No.3

This study was performed to increase the utilization of rice and improve the productivity of jochung, traditional food in Korea. Two kinds of jochung products were prepared from steamed rice(SR) and wet-milled rice flour(WRF) by rice cultivated from 2006 to 2010. It is common to add a liquefying enzyme for rice liquefaction(4 ㎖/1,000 g rice, at 90~95℃, 3 h) and saccharogenic enzyme with malt(45 g/1,000 g rice, at 55~57℃, 6 h). In order to evaluate the quality characteristics of jochung, producing rate, pH, solidity, reducing sugar, dextrose equivalence(D.E.), viscosity, total phenolic compound, color value and sensory evaluation were carried out. In terms of the producing rate of jochung, WRF jochung was produced about 7.4% much more than SR jochung. There was no difference in producing rate between the jochung cultivated from 2006 to 2010 rice. The pH varied from 4.86~5.66, solidity was 79.48~82.28%. Color L value was 25.82~27.92, a value of 1.28~2.81, b value were 2.98~4.33. The results of sensory evaluation for jochung, as a whole, received higher score than for the commercial product(Daesang Co., Ltd, Seoul, Korea), overall acceptability score was the highest in the 2008SR. Reducing sugar, dextrose equivalence(D.E.) and total phenolic compounds were determined to be higher WRF jochung than SR jochung, while viscosity was lower WRF jochung than SR jochung. These results are thought to be due to increased surface area of rice by milling. SR jochung manufacturd by wet-milled rice flour will increase the producing rate for jochung, thereby saving manufacturing time and costs. 본 연구에서는 쌀의 이용성 증진과 우리나라 전통식품인조청의 생산성 및 품질을 향상시키기 위해 수침한 쌀을 증자또는 분쇄하여 제조한 조청의 품질특성(생산량, pH, 당고형분, 환원당, 포도당 당량, 점도, 총 폴리페놀, 색도, 관능평가)을 측정하고자 하였다. 쌀은 2006~2010년 쌀을 이용하였으며, 생산량을 측정한 결과 유의적 차이가 나타나지 않았다. WRF 조청의 생산량이 SR 조청의 생산량보다 약 7.4% 증가하였다. pH는 4.86~5.66으로 다양하게 나타났고, 당 고형분은 79.48~82.28%로 나타났다. 색도 측정 결과, L(lightness)값은 25.82~27.92로 측정되었으며, 황색도를 나타내는 b값에서 SR 조청과 WRF 조청은 2009년 쌀로 제조한 조청을 제외하고 유의적차이가 있었으며, 2006, 2007, 2008년 생산된 쌀로 제조한 SR 조청과 WRF 조청 간에는 유의적 차이가 나타나지 않았다. 관능평가결과, 시중 제품보다 전체적으로 높은 평가를 받았으며, 전반적 기호도에서 2008년 생산된 쌀을 이용하여 제조한SR 조청이 가장 높은 점수를 받았다. 환원당, 포도당 당량, 총폴리페놀 함량은 년도별 쌀 이용에 따라 차이가 나타나지 않았으며, WRF 조청이 SR 조청보다 더 높게 측정되었다. 점도는 WRF 조청이 SR 조청보다 더 낮게 측정되었다. 이러한 결과는 수침쌀을 분쇄함에 따라 쌀의 표면적 증가에 의한 결과라고 사료되며, 쌀을 분쇄하여 조청을 제조하면 시간 절약에따라 생산비 절감 효과를 얻을 수 있을 뿐 아니라, 생산량도증가하여 조청의 품질 향상에 영향을 줄 것으로 사료된다.

Comparative study of homogeneous nucleation rate models for wet steam condensing flows

Xu Han,Zhonghe Han,Hengfan Li,Peng Li 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.12

To accurately describe the homogeneous nucleation process in a wet-steam dual-phase flow and to improve the reliability of computations of the condensing steam flow, classical homogeneous nucleation theories were derived and summarized based on the molecular agglomerate thermodynamic free energies. To obtain more accurate homogeneous nucleation rates, various modified homogeneous nucleation rate models were described. Experimental data were used in a comparative study of these models to select a nucleation rate model to provide calculated values for engineering projects. This study indicates that the main difference between different nucleation theories lies in the difference in the influence of temperature on the nucleation rate.

복합화력발전 내 배열회수 보일러용 소재(탄소강 계열 및 듀플렉스 스테인리스강(UNS S32205))의 황산농도에 따른 부식거동 비교 연구

Yu Sung Jang,Jin Sung Park,Seung Gab Hong,Sung Jin Kim 대한금속·재료학회 2023 대한금속·재료학회지 Vol.61 No.11

This study examined the effects of sulfuric acid concentrations on the corrosion behaviors of three types of commercial steels, conventional carbon steel (SA192), sulfuric acid dew resistant steel (S-TEN), and duplex stainless steel (S32205), considered to be potential materials for the heat recovery steam generator (HRSG) in combined cycle power plants. Based on the results of electrochemical polarization, immersion and wet-dry cycle tests, when exposed to a high sulfuric acid concentration (50%), SA192 and S-TEN exhibited higher corrosion resistance than S32205, which was due to the formation of a stable FeSO4 scale on the carbon steel materials. With prolonged exposure, S-TEN with slightly higher concentrations of Cu and Sb showed lower weight loss than SA192. Conversely, when subjected to low sulfuric acid concentrations (5 and 10%), S32205 exhibited passivation behavior, and showed significantly superior corrosion resistance (i.e., much smaller weight loss) than the other two steel samples. The examination of localized corrosion damages through cross-section observation using a scanning electron microscope revealed also that S32205 suffered less damages from the wet-dry cycling. The long-term superior corrosion resistance of duplex stainless steel in low sulfuric acid concentrations, compared to carbon steel and sulfuric acid due resistant steel, make it a promising candidate material for the HRSG in combined cycle power plants.

Unsteady Wet Steam Flow Measurements in a Low-Pressure Test Steam Turbine

Duan, Chongfei,Ishibashi, Koji,Senoo, Shigeki,Bosdas, Ilias,Mansour, Michel,Kalfas, Anestis I.,Abhari, Reza S. Korean Society for Fluid machinery 2016 International journal of fluid machinery and syste Vol.9 No.1

An experimental study is conducted for unsteady wet steam flow in a four-stage low-pressure test steam turbine. The measurements are carried out at outlets of the last two stages by using a newly developed fast response aerodynamic probe. This FRAP-HTH probe (Fast Response Aerodynamic Probe - High Temperature Heated) has a miniature high-power cartridge heater with an active control system to heat the probe tip, allowing it to be applied to wet steam measurements. The phase-locked average results obtained with a sampling frequency of 200 kHz clarify the flow characteristics, such as the blade wakes and secondary vortexes, downstream from the individual rotational blades in the wet steam environment.

Unsteady Wet Steam Flow Measurements in a Low-Pressure Test Steam Turbine

Chongfei Duan,Koji Ishibashi,Shigeki Senoo,Ilias Bosdas,Michel Mansour,Anestis I. Kalfas,Reza S. Abhari 한국유체기계학회 2016 International journal of fluid machinery and syste Vol.9 No.1

An experimental study is conducted for unsteady wet steam flow in a four-stage low-pressure test steam turbine. The measurements are carried out at outlets of the last two stages by using a newly developed fast response aerodynamic probe. This FRAP-HTH probe (Fast Response Aerodynamic Probe - High Temperature Heated) has a miniature high-power cartridge heater with an active control system to heat the probe tip, allowing it to be applied to wet steam measurements. The phase-locked average results obtained with a sampling frequency of 200 kHz clarify the flow characteristics, such as the blade wakes and secondary vortexes, downstream from the individual rotational blades in the wet steam environment.