• International Journal of Fluid Machinery and Systems
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• 제9권1호
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• pp.85-94
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• 2016

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.

• 한국전산유체공학회지
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• 제20권3호
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• pp.1-7
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• 2015

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.

• Journal of the Korean Wood Science and Technology
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• 제42권6호
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• pp.700-707
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• 2014

본 연구에서는 고온증기 및 오존처리 전처리 후, 습식 고전단 해섬하여 국내산 잣나무로부터 리그노셀룰로오스 나노섬유를 제조하였다. 고온증기 및 오존 전처리에 의해 헤미셀룰로오스 및 리그닌 성분은 각각 약 40%, 42%의 감소효과를 보였으며, 무처리 목분에 비교하여 습식 고전단 해섬처리 시간이 증가함에 따라 섬유의 직경이 더욱 크게 감소하였으며, 좁은 치수분포를 나타냈다. 두 전처리 후 얻어진 리그노셀룰로오스 나노섬유는 평균직경이 각각 19 nm 및 12 nm로 매우 가느다란 것으로 관찰되었다. 얻어진 리그노셀룰로오스 나노섬유를 폴리우레탄 폴리머의 강화필러로 첨가한 결과, 첨가량 및 해섬처리 시간이 증가함에 따라 복합재료의 인장강도와 탄성율이 증가하였다. 특히, 두 전처리 후 얻어진 리그노셀룰로오스 나노섬유의 경우가 전처리하지 않은 경우에 비해 복합재료의 인장강도 특성을 더 향상시키는 것을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3252-3258
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• 2010

In this study, the effects of the various parameters of spinning and drawing processes on the properties of polyester full drawn yarn (FDY) prepared by steam processing during high-speed spinning were investigated using several techniques. The wet shrinkage ratio of the FDY was able to be manipulated by controlling the temperature and draw ratio. The FDY made using the steam high speed spinning technique exhibited identical properties (such as tenacity, elongation, and wet shrinkage ratio) to that of regular FDY, made using the spin-draw process. FDY prepared using the steam process during high-speed spinning showed excellent dyeability. The dye pick-up of the polyester yarn spun at high-speed spinning was found to be improved when dyed under an atmospheric pressure of $100^{\circ}C$. This result was the same as regular FDY dyed under a high pressure of $130^{\circ}C$.

• Nuclear Engineering and Technology
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• 제45권7호
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• pp.895-910
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• 2013

The reflood test data from the rod bundle heat transfer (RBHT) test facility showed that the grids in the upper portion of the rod bundle could become wet well before the arrival of the quench front and that the sizes of liquid droplets downstream of a wet grid could not be predicted by the droplet breakup models for a dry grid. To investigate the water droplet generation from a wet grid spacer, a viscous linear temporal instability model of the water sheet issuing from the trailing edge of the grid with the surrounding steam up-flow is developed in this study. The Orr-Sommerfeld equations along with appropriate boundary conditions for the flow are solved using Chebyshev series expansions and the Tau-Galerkin projection method. The effects of several physical parameters on the water sheet oscillation are studied by determining the variation of the temporal growth rate with the wavenumber. It is found that a larger relative steam velocity to water velocity has a tendency to destabilize the water sheet with increased dynamic pressure. On the other hand, a larger ratio of steam boundary layer to the half water sheet thickness has a stabilizing effect on the water sheet oscillation. Droplet diameters downstream of the spacer grid predicted by the present model are found to compare reasonably well with the data obtained at the RBHT test facility as well as with other data recently reported in the literature.

• 한국조리학회지
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• 제12권2호
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• pp.206-221
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• 2006

To establish an optimum formula for processing wet noodles with steam-dried Hizikia fusiformis flour(SHF), it was incorporated into wheat flour by the ratio of 0, 1, 3, 5, 10 and 20% based on a flour weight. Application of 2% mehthylcelluose(MC) to improve the texture of noodles mixed with SHF was also attempted. Evaluation was performed on the dough rheology and wet noodle quality, such as cooking characteristics, mechanical texture properties, sensory value and shelf-life. Water absorption rate of the composite flour increased linearly as the content of SHF increased from 1% to 10%, and noodle sheet-formation was also acceptable in the same content level. The weight and volume of cooked noodles were decreased, and turbidity of soup was, if exceeding more than 5% of SHF, increased constantly. However, these problems could be remarkably resolved in SHF plus 2% MC. Texture profile analysis of cooked noodles showed an increase of hardness, gumminess, and chewiness up to 5% SHF. The results of sensory evaluation showed that cooked noodles containing 5% SDF were acceptable as much as wheat four noodles in terms of color, texture, taste and flavor. Based on cooking properties, rheological and sensory evaluation, addition of 5% SHF plus 2% MC was suggested to be suitable for making wet noodles, of which the shelf-life was estimated to be 8 days at $5^{\circ}C$.

• 전기학회논문지
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• 제59권11호
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• pp.2006-2011
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• 2010

The superheater in the thermal power plant makes the wet steam into the dry steam with high temperature and high pressure by using the boiler heat. The dry steam pressure rotates the turbine-generator system. The efficiency and life time of the boiler heavily depends on the steam temperature regulation. The steam temperature can be deviated from the reference by the MW demand of the power plant. It is therefore required that the PI(proportional-integral) controller should be robust against the disturbance such as the MW demand. In this paper, the PI controller with the integral state predictor is proposed and applied to regulate the steam temperature of the superheater, and it is compared with the conventional PI controller operated in the thermal power plant in view of control performance.

• 한국수소및신에너지학회논문집
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• 제28권2호
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• pp.129-136
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• 2017

Characteristics of $ZrO_2$ felt supported Cu/Zn catalysts have been investigated for the production of hydrogen via methanol steam reforming. Cu and Zn in different weight percent were loaded using wet impregnation over $ZrO_2$ felt support. The catalysts were characterized with BET and FE-SEM. The performance of these synthesized catalysts were investigated at SCR=1.5, $GHSV=2000h^{-1}$, temperature=$300{\sim}400^{\circ}C$, and pressure=2.5~19.5 barA. The results showed that the $Cu^{32.5}Zn^{7.5}ZrO_2$ catalyst was most active in terms of methanol conversion and hydrogen production. The methanol conversion in steam reforming of methanol was 84.6% at 19.5 barA and furnace $400^{\circ}C$ over $Cu^{32.5}Zn^{7.5}ZrO_2$ catalyst. The catalysts prepared using $ZrO_2$ felt show higher reactor temperature than the pellet type catalyst at same furnace temperature.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2008년도 추계학술발표대회 논문집
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• pp.280-287
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• 2008

In case of low pressure steam turbine used in power plant, it was operated in wet steam and high stress condition. Therefore, it is possible that the corrosion damage of low pressure was induced by this condition. According to previous study, about 30% of total blade failure correspond to corrosion fatigue or SCC(stress corrosion cracking) in low pressure turbine. Especially, LSB(last stage bucket) of low pressure turbine has a higher hardness to prevent erosion damage due to water droplet however, generally this is more dangerous for SCC damage. Therefore, to improve reliability of turbine blade. various methods for SCC evaluation has been developed. In this study, the crack found in LSB during in-service inspection was evaluated using microstructure analysis and stress analysis. From the stress analysis, the optimum size of fillet to remove the crack was proposed. And also, the reliability was evaluated for modified LSB using GOODMAN diagram.

• Journal of Mechanical Science and Technology
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• 제17권1호
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• pp.114-121
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• 2003

Water droplet erosion is one of major concerns in the design of modern large fossil steam turbines because it causes serious operational problems such as performance degradation and reduction of service life. A new erosion model has been developed in the present study for the prediction of water droplet erosion of rotor blades operated in wet steam conditions. The major four erosion parameter : impact velocity, impacting droplet flow rate, droplet size and hardness of target are involved in the model so that it can also be used for engineering purpose at the design stage of rotor blades. Comparison of the predicted erosion rate with the measured data obtained from the practical steam turbine operated for more than 90,000 hours shows good agreement.