• Title/Summary/Keyword: rotors

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Study on the Improvement of Strength for 12% Chromium Steel Rotor (12% Cr 로터강의 강도 개선에 관한 연구)

  • Jang, Yun-Seok;O, Se-Uk
    • Journal of Ocean Engineering and Technology
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    • v.3 no.2
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    • pp.125-137
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    • 1989
  • To check technical improvement in the soundness and strength of 12% Cr steel rotor, a 25 tons of rotor with 65 tons of ingot was made in real size and was cut to pieces to take test samples, and the various mechanical tests such as impact, tensile, creep, and fatigue were carried out. The strengths are compared with those of 1% Cr-Mo-V rotor of same size. Microstructures of the samples are examined and reviewed. The results can be summarized as follows. 1) Fracture appearance transition temperatures are 80.deg. C at the center part and 60.deg. C near surface of 12% Cr rotor, and 8.deg. C near surface of 1% Cr-Mo-V rotor. 2) Comparative rapid softening occurs at higher temperatures above 600.deg. C for 12% Cr steel and 550.deg. C for 1% Cr-Mo-V steel in tension tests. 3) Fatigue crack propagation rate of 12% Cr steel is almost same as that of 1% Cr-Mo-V steel at the same corresponding surface part of the rotors. The crack growth rate of center part of 12% Cr rotor is faster than near surface part of the rotor, and the crack growth rate at the load condition of R=0.04 is slower than that of the load condition of R=0.5 for both 12% Cr steel and 1% Cr-Mo-V steel. 4) Crack growth rate of radial direction near surface of 12% Cr rotor is faster than that of transverse direction at the same part because of the difference in residual stresses. 5) Both creep and fatigue strengths of 12% Cr steel are superior to those of 1% Cr-Mo-V steel and the difference is thought the effect of climb and glide controlled creep by solid solution of alloying elements and dispersion of carbides.

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Study on the Improvement of Strength for 12% Chromium Steel Rotor (12% Cr 로터강의 강도 개선에 관한 연구)

  • Jang, Yun-Seok;O, Se-Uk
    • Journal of Ocean Engineering and Technology
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    • v.3 no.2
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    • pp.625-625
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    • 1989
  • To check technical improvement in the soundness and strength of 12% Cr steel rotor, a 25 tons of rotor with 65 tons of ingot was made in real size and was cut to pieces to take test samples, and the various mechanical tests such as impact, tensile, creep, and fatigue were carried out. The strengths are compared with those of 1% Cr-Mo-V rotor of same size. Microstructures of the samples are examined and reviewed. The results can be summarized as follows. 1) Fracture appearance transition temperatures are 80.deg. C at the center part and 60.deg. C near surface of 12% Cr rotor, and 8.deg. C near surface of 1% Cr-Mo-V rotor. 2) Comparative rapid softening occurs at higher temperatures above 600.deg. C for 12% Cr steel and 550.deg. C for 1% Cr-Mo-V steel in tension tests. 3) Fatigue crack propagation rate of 12% Cr steel is almost same as that of 1% Cr-Mo-V steel at the same corresponding surface part of the rotors. The crack growth rate of center part of 12% Cr rotor is faster than near surface part of the rotor, and the crack growth rate at the load condition of R=0.04 is slower than that of the load condition of R=0.5 for both 12% Cr steel and 1% Cr-Mo-V steel. 4) Crack growth rate of radial direction near surface of 12% Cr rotor is faster than that of transverse direction at the same part because of the difference in residual stresses. 5) Both creep and fatigue strengths of 12% Cr steel are superior to those of 1% Cr-Mo-V steel and the difference is thought the effect of climb and glide controlled creep by solid solution of alloying elements and dispersion of carbides.

A Rotordynamic Analysis of a Industrial Centrifuge for Vibration Reduction (산업용 원심분리기의 진동저감을 위한 로터다이나믹 해석)

  • Kim, Byung-Ok;Lee, An-Sung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.18 no.8
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    • pp.879-885
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    • 2008
  • A rotordynamic analysis was performed with a decant-type centrifuge, which is a kind of industrial centrifuge. The system is composed of screw rotor, bowl rotor, driving motors, gear box, and support rolling element bearings. These rotors have a rated speed of 4300 rpm, and were modeled utilizing a rotordynamic FE method for analysis, which was verified through 3-D FE analysis. Design goals are to achieve wide separation margins of lateral critical speeds, and favorable unbalance responses of the rotor in the operating range. Then, a complex analysis rotordynamic analysis of the system was carried out to evaluate its forward synchronous critical speeds and mode shapes, whirl natural frequencies, and unbalance responses under various balance grade. As a result of analysis, the rotordynamic analysis performed by separating a screw rotor and bowl rotor may cause an error in predicting critical speed of entire system. Therefore, the rotordynamic analysis of a coupled rotor combining a screw and bowl rotor must be performed in order to more accurately estimate dynamic characteristics of the decanter-type centrifuge as presented in this paper. Also, rolling element bearings with suitable stiffness should be selected to keep enough separation margin. In addition, in establishing balance grade of a screw and bowl rotor, ISO G2.5 balance grade is more recommended than ISO G6.3, in particular balancing correction of a screw rotor based on ISO G2.5 grade is strongly recommended.

Conceptual design of cooling anchor for current lead on HTS field coils

  • Hyeon, C.J.;Kim, J.H.;Quach, H.L.;Chae, S.H.;Yoon, Y.S.;Lee, J.;Han, S.H.;Jeon, H.;Choi, Y.H.;Lee, H.G.;Kim, H.M.
    • Progress in Superconductivity and Cryogenics
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    • v.19 no.2
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    • pp.38-43
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    • 2017
  • The role of current lead in high-temperature superconducting synchronous machine (HTSSM) is to function as a power supply by connecting the power supply unit at room temperature with the HTS field coils at cryogenic temperature. Such physical and electrical connection causes conduction and Joule-heating losses, which are major thermal losses of HTSSM rotors. To ensure definite stability and economic feasibility of HTS field coils, quickly and smoothly cooling down the current lead is a key design technology. Therefore, in this paper, we introduce a novel concept of a cooling anchor to enhance the cooling performance of a metal current lead. The technical concept of this technology is the simultaneously chilling and supporting the current lead. First, the structure of the current lead and cooling anchor were conceptually designed for field coils for a 1.5 MW-class HTSSM. Then, the effect of this installation on the thermal characteristics of HTS coils was investigated by 3D finite element analysis.

Performance and Internal Flow Condition of Mini Centrifugal Pump with Splitter Blades

  • Shigemitsu, Toru;Fukutomi, Junichiro;Kaji, Kensuke;Wada, Takashi
    • International Journal of Fluid Machinery and Systems
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    • v.6 no.1
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    • pp.11-17
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    • 2013
  • Mini centrifugal pumps having a diameter smaller than 100mm are employed in many fields. But the design method for the mini centrifugal pump is not established because the internal flow condition for these small-sized fluid machines is not clarified and conventional theory is not suitable for small-sized pumps. Therefore, mini centrifugal pumps with simple structure were investigated by this research. Splitter blades were adopted in this research to improve the performance and the internal flow condition of mini centrifugal pump which had large blade outlet angle. The original impeller without the splitter blades and the impeller with the splitter blades were prepared for an experiment. The performance tests are conducted with these rotors in order to investigate the effect of the splitter blades on performance and internal flow condition of mini centrifugal pump. On the other hand, a three dimensional steady numerical flow analysis is conducted with the commercial code (ANSYS-CFX) to investigate the internal flow condition in detail. It is clarified from experimental results that the performance of the mini centrifugal pump is improved by the effect of the splitter blades. Blade-to-blade low velocity regions are suppressed in the case with the splitter blades and total pressure loss regions are decreased. The effects of the splitter blades on the performance and the internal flow condition are discussed in this paper.

The Characteristics of Fashion Design as a Playing through a Doll (인형 놀이에 나타난 패션 디자인의 특성)

  • Lee, Ji-Hyun;Kim, Young-In
    • Journal of the Korean Society of Costume
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    • v.57 no.2 s.111
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    • pp.86-99
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    • 2007
  • In this study, the concept of play as an entertainment is redefined and applicable method of fashion design as a play are suggested by analyzing the feature of doll's costume design based on the play pattern. In literary study, the role of playing doll Is described and has been examined by the analysis of scholars' opinions. In positive study, the pattern and costume design of sample costume dolls are analyzed using 624 samples of the representative images collected from the literatures and real figures, and they are classified as collection dolls or fashion dolls in order to analyze the feature of fashion design in playing dolls. As a result of the analysis of doll's costumes based on its use, the costumers are divided into a real world costume which is similar to what human wear in daily life and a virtual costume which is used in the movie or play and the costumes only worn by the dolls. The examination of the type of costume worn by dolls, dress is principally dominant costume in collection doll, whereas in fashion doll, dress is still mainly worn but shirt blouse & pants, shirt blouse k skirt, jacket, coat, bathing suit. etc. are shown dispersedly as well. In the costume silhouette of dolls, collection doll uses mostly A line silhouette meanwhile fit and flare is mostly used in the fashion doll but other silhouettes are also relatively shown a lot. In the means of the color of the costume worn by dolls, collection doll is more similar to those in actual fashion design. On the contrary, the color of the costume that fashion doll is put on is more free and more various because the trendy rotors such as green, yellow, purple, etc are used.

New Balancing Method of a Flexible Rotor Without Trial Weights (彈性回轉體의 평형잡이에 관한 연구)

  • 양보석;암호탁삼
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.3
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    • pp.409-418
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    • 1988
  • Steam turbines, gas turbines, multistage centrifugal compressors are operated over the range of the first critical speed. In these rotors flexible rotor balancing technique is necessary. In such balancing, influence coefficients are measured by rotating a rotor with trial weight. But for the large rotor, the measurement of influence coefficient takes much time and it reduces the cost efficiency. In this paper the new influence coefficient with rotation of rotor is proposed. First the theoretical background of the method is presented and it is applied to the simple flexible rotor model. Then the experiments are performed and the results of presented method are compared with those of analytical method. By using the obtained influence coefficient, balancing of the flexible rotor is performed.

A study on how to discriminate the polarities of stator windings for 3 phase induction motors by using induced voltages based on residual magnetism (잔류자기 유도 기전력을 이용한 3상유도전동기 권선의 극성 판별법에 관한 연구)

  • Choi, Soon-Man
    • Journal of Advanced Marine Engineering and Technology
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    • v.38 no.9
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    • pp.1146-1149
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    • 2014
  • To discriminate polarities of stator windings for 3 phase induction motors terminal tags of which are not readable, it is possible to utilize the residual magnetic flux present at their rotors as well as to use the way based on external exciting current. The induced voltages are basically decided by parameters such as the quantity of residual flux, the rotator speed by hand force and the phase properties between stator windings. To adopt induced voltages by residual flux for polarity discrimination at sites, the measured voltages by multi-testers need to be readable in magnitude enough to discriminate winding condition with reasonable phase characteristics. This study focuses on the analysis of various connection cases in the expectation that the summing voltages induced by residual flux shall show zero in case of normal connections while the sum becomes greater indication if the connection is in wrong condition. The proposed method is applied to actual motors to disclose how effective it is for polarity discrimination at sites through comparison of output signals between normal and fault connections.

Investigating the Power-Performance Prediction on an H- and Helical-type Tidal Current Turbine Using CFD Method (CFD에 의한 H 및 Helical 타입 조류발전용 터빈의 출력성능예측에 관한 연구)

  • Kim, Bum Suk
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.8
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    • pp.653-660
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    • 2015
  • In this study, we conduct power performance and load analyses of two different types of vertical-axis tidal-current turbines using the computational fluid dynamics (CFD) method. To analyze the power output and loads, we perform transient CFD simulations considering the cavitation model using ANSYS CFX. The averaged power output of an H-type rotor was 7.47 kW and 67.6 kW in normal and extreme operating conditions, respectively, which did not satisfy the initial design conditions. However, in the case of the helical-type rotor, the power output under normal and extreme conditions were close to the expected values. The cavitation, which may cause instantaneous power fluctuation, occurred repeatedly at the suction side of the rotors. In order to guarantee a more stable power supply and to prevent fatigue failure, we require a design that minimizes cavitation.

A Study on Experimental Test of a Small Scale Hingeless Rotor (축소형 무힌지 로터 시험에 관한 연구)

  • Kim, Joune-Ho;Song, Keun-Woong;Joo, Gene;Suk, Jin-Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.12
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    • pp.1599-1606
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    • 2011
  • It is possible to study the load characteristics of full-scale hingeless rotor with the changing of physical smallscaled configurations such as rectangular and paddle blades, and metal and composite hubs. In this study, a static test, and a ground and wind-tunnel test were carried out using small-scale rotor models. The static test was carried out to confirm structural stiffness, characteristics of inertia, natural frequency, and damping ratio of rotors, and the ground and wind-tunnel test was carried out to confirm the stability and aerodynamic characteristics under hovering and forward flight conditions. According to the test results, the vertical load in the case of a combination of a small composite hub with paddle blades was higher than that in the case of a metal hub with paddle blades at same condition. Further, it was confirmed that the restraint of the combination of composite hub can be more flexible than the metal hub for the motion of paddle blades.