• Title/Summary/Keyword: The Gap Ratio

Search Result 948, Processing Time 0.042 seconds

Analysis of Torque and Force Distribution of Axial-Gap Type Wobble Moto (축방향 공극형 Wobble 모터의 토오크 특성 및 힘 분포 해석)

  • Woo, Sung-Bong;Lee, Eun-Woong;Yun, Seo-Jin;Kim, Sung-Jong;Choi, Jae-Young
    • Proceedings of the KIEE Conference
    • /
    • 1999.11b
    • /
    • pp.9-11
    • /
    • 1999
  • This paper presents the problems of design and theoretical model of electrostatically driven axial-gap type wobble motor. The motor design benefits from large axial rotor-to-stator overlap and large gear ratios, and motor designs with rotor radii of 50 and $100{\mu}m$ are capable of generating torques in the [nNm] range at high electrostatic fields. Because of the large gear ratio, smaller angular steps and lower rotational speed are obtained, compared to radial-gap motor design. Aspects like gear ratio, torque generation, excitation schemes and torque coverage, normal forces, friction are addressed.

  • PDF

A Numerical Study on the Ground Effect of a Circular Cylinder in the Presence of a Moving Wall (이동벽면에 의한 원형 실린더의 지면효과에 관한 전산연구)

  • Jung, Jae-Yoon;Chang, Jo-Won
    • Journal of the Korean Society for Aviation and Aeronautics
    • /
    • v.14 no.4
    • /
    • pp.1-10
    • /
    • 2006
  • A computational study was carried out in order to investigate the ground effect of a circular cylinder in the presence of a moving wall at a Reynolds number of 2.0${\times}$104. The viscous-incompressible Navier-Stokes equations and Spalart-Allmaras turbulent model of the commercial CFD code were adopted for this numerical analysis. The moving wall was set parallel with the freestream, and the speed of motion was equal to the freestream velocity. The gap ratio is defined as the distance ratio between the circular cylinder diameter and the height from the moving wall. The numerical results show that there are the differences among the each of the stages in evidence of the vorticity contours and the polar diagrams of $C_l$ vs. $C_d$. The 4 stages of the gap ratio are defined according to the flow features, whose stages are divided into small, intermediate, large and convergence gap ratios, respectively.

  • PDF

Design of Height Adjustment Mechanism for Flat Panel Display by DFSS (DFSS에 의한 FPD용 높이 조절기구 설계)

  • Cho, Gyu-Yeol;Cheong, Seon-Hwan;Choi, Seong-Dae
    • Transactions of the Korean Society of Machine Tool Engineers
    • /
    • v.16 no.1
    • /
    • pp.92-97
    • /
    • 2007
  • This study was carried out to minimize the lifting force and to design the slim sized frame of a height adjustment mechanism. This unit is designed for the display devices in order to enhance the ergonomics for effective height adjustment as well as to achieve much slimmer frame for the pedestal. A tolerance analysis of 6 sigma was applied to achieve smooth lift at design stage not to change the tolerance specification of gap several times in a roller type of lifting mechanism at mass production stage. The specification of minimum gap and the target of production yield ratio were agreed with a quality team before tooling. A DFSS simulation on drawings had been done with reasonable tolerance and achievable standard deviation(${\sigma}$) several times until the target specification of gap and yield ratio was met. Once tolerance and deviation(${\sigma}$) were fixed tooling start was done successfully. A CAE method was applied to achieve a slim design. Design parameters were frozen when those parameters matched the reference strength data of standard model. Through those tolerance analysis and CAE simulation the number of tool modification was reduced and production yield ratio was raised up without arguing quality specification at production stage in the end.

An Experimental Study on the Two-Phase Flow Pressure Drop Within Horizontal Rectangular Channels with Small Gap Heights (미세 수평 사각유로에서의 2상 유동 압력강하에 관한 실험적 연구)

  • Lee, Han Ju;Lee, Sang Yong
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.23 no.5
    • /
    • pp.637-645
    • /
    • 1999
  • Horizontal two-phase flow pressure drop within rectangular channels with small gap heights have been examined experimentally. The gap heights range from 0.4mm to 4mm corresponding to aspect ratios(the channel height divided by the width) from 0.02 to 0.2. Water and air were used as the test fluids with the superficial velocity ranges being 0.03-2.39m/s and 0.05-18.7m/s, respectively. The experimental results In rectangular channels were compared with the Lockhart-Martinelli correlation, which are widely used for conventional round tube. The Lockhart-Martinelli correlation turned out to be Inappropriate to represent the present experimental data. In this respect, considering the aspect ratio and gap-height effects, an empirical correlation on two-phase flow pressure drop was proposed. The proposed correlation successfully covers the bubbly, plug, slug and annular flow regimes.

Characterization of Segmented Block Copolyurethane Network Based on Glycidyl Azide Polymer and Polycaprolactone

  • Min, Byoung-Sun;Ko, Seung-Won
    • Macromolecular Research
    • /
    • v.15 no.3
    • /
    • pp.225-233
    • /
    • 2007
  • To improve the poor mechanical and low-temperature properties of glycidyl azide polymer (GAP)-based propellants, the addition of binders was investigated using GAP and flexible polymer backbone-structural polycaprolactone (PCP) at various weight(wt) ratios, and varying the ratio of Desmodur N-100 pluriisocyanate (N-100) to isophorone diisocyanate (IPDI). Using Gee's theory, the solubility parameter of the PCP network was determined, in order to elucidate the physical and chemical interaction between GAP and PCP. The structure of the binder networks was characterized by measuring the cross-link densities and molecular weights between cross-links ($M_c$) obtained by a swelling experiment using Flory-Rhener theory. The thermal and mechanical properties of the segmented block copolyurethane (GAP-b-PCP) binders prepared by the incorporation of PCP into the binder recipes were investigated, along with the effect of the different curatives ratios.

An Experimental Study on the Quenching Phenomena of Hemispherical Downward Facing Convex Surfaces with Narrow Gaps (반구형 소형 간극 내에서의 냉각과정에 관한 실험적 연구)

  • Ha, Kwang-Soon;Park, Rae-Joon;Kim, Sang-Baik;Cho, Young-Ro;Kim, Hee-Dong
    • Proceedings of the KSME Conference
    • /
    • 2001.06d
    • /
    • pp.447-452
    • /
    • 2001
  • Quenching phenomena of hemispherical downward facing convex surfaces with narrow gaps have been investigated experimentally. Experiments employed test sections having 1 and 2 mm in gap thickness and 1 atm in system pressure. From interpretations of the temperature and the heat flux history, it was found that the flooding inside the gap was restricted by CCFL phenomena and quenching process was propagated from lower to upper region of the internal copper shell. The ratio of the maximum heat fluxes at 1 mm to 2mm in gap thickness was the almost same that obtained by steady state experiments. The quenching scenario of the hemispherical downward facing surface with narrow gap has been suggested.

  • PDF

Theoretical Study of Compression Performance with gap of linear compressor for Stirling cryocooler (선형압축기 실린더 간극이 압축특성에 미치는 영향에 관한 이론적연구)

  • 홍용주;신완순;박성제;고득용;김효봉;오군섭
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
    • /
    • 2001.02a
    • /
    • pp.149-152
    • /
    • 2001
  • The Linear compressor is widely used in Stirling cryocooler for cooling of infrared sensor. The performance of Stirling cryocooler was mainly depending on how much pressure difference can be generated by compressor. The gap between cylinder and piston should be minimized to get high pressure difference, but too small gap cause failure in the cryocooler. In this study, the leakage rate through gap was investigated by using CFD method and simple thermodynamic relation. The results show compression ratio is decreased and leakage rate increased according to increasing gap.

  • PDF

Evaluation of Multi-legged Roundabout Using Surveyed Critical Gap Acceptance (현장 임계간격을 이용한 다지 회전교차로 분석)

  • Park, Soon-Yong;Kim, Dong-Nyong;Jeong, Jun-Hwa
    • The Journal of the Korea Contents Association
    • /
    • v.13 no.9
    • /
    • pp.400-409
    • /
    • 2013
  • In this paper, considering the characteristics of the driver at roundabouts by investigating the critical gap acceptance on various traffic conditions, multi-legged roundabouts were evaluated. The gap acceptance and rejection of 4-legged, 5-legged, 6-legged, and 7-legged roundabout were surveyed on real fields, and the critical gap acceptance was estimated using Raff's methods. Derived the critical gap acceptance was processed calibration and validation for micro-simulation, and then multi-legged roundabouts under variable conditions such as variations of traffic volume, turning ratio, and size of inscribed circle diameter were evaluated to verify operating conditions of roundabouts. As the results, according to the operating traffic volume and turning ratio, the inscribed circle diameters were proposed at each level of service. These inscribed circle diameters were able to reflect the guideline of geometric design for multi-legged roundabouts.

Experimental Analyses of Flow in a Production Torque Converter Using LDV (LDV를 이용한 토크컨버터 내 유동의 실험적 분석)

  • Yoo, S.C.
    • Journal of the Korean Society of Mechanical Technology
    • /
    • v.20 no.6
    • /
    • pp.757-762
    • /
    • 2018
  • LDV(laser Doppler velocimetry) measurements were conducted on the exit region of the impeller passage and the gap between the impeller and turbine blades under 0.8 speed ratio. The 0.8 speed ratio has an impeller speed of 2000rpm and a turbine speed of 1600rpm. A periodic variation of the mass flow rate is present in many of the measurements made. The frequency of this variation is the same as the frequency of the turbine blades passing the impeller passage exit. It is found that the instantaneous position of the turbine had effect on fluid flow inside the impeller passage and gap region. This study would aid in the construction of higher accuracy CFD models of this complex turbomachinery device.

Effect of Ga, S Additions in CuInSe$_2$ for Solar Cell Applications

  • Kim, Kyoo-Ho
    • Journal of the Korean institute of surface engineering
    • /
    • v.37 no.4
    • /
    • pp.191-195
    • /
    • 2004
  • Gallium or sulphur additions in $CuInSe_2$ were prepared using RF magnetron sputtering and pulsed laser deposition respectively. All of the observed thin films shows a chalcopyrite structure with the S and Ga addition increases the favourable (112) peak. The optical absorption coefficients were slightly decreased. The energy band gap of films could be shifted from 1.04 to 1.68 eV by adjusting the mole ratio of S/(S+Se) and Ga/(In+Ga). It is possible to obtain the optimum energy band gap by adding S or Ga solute at a certain ratio in favour of Se and In respectively. It is also necessary to control the ratio of Ga and S additions and to retain a certain portion of In and Se to provide better properties of thin films.