• Title, Summary, Keyword: Speed Ratio

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A Study On the Structure and Mechanical Properties of PP filament at Different Spinning speed and Draw ratio (방사속도 및 연신비 변화에 따른 Polypropylene filament의 구조와 물성에 관한 연구)

  • Lee, Eun-Woo;Cho, Kyu-Min;Cho, In-Sul
    • Journal of the Korean Society of Industry Convergence
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    • v.2 no.1
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    • pp.27-33
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    • 1999
  • Effects of spinning speed and draw ratio on structure and mechanical properties of PP filament. A The crystalline structure and mechanical properties of uniaxially deformed polypropylene filament has been examined by XRD, birefringence, UTM and density method. Uniaxially deformed PP filament was prepared of various spinning speeds (300, 600, 900m/min.) and draw ratio(x2, x3, x4). From the results of these studies, it found the following facts. Firstly, it was found that the crystallinity and crystallite size (110plane) of the samples were increased with increasing of spinning speed and draw ratio, especially, it was rapidly increased between as spun yarn and 2 times draw ratio. Secondly, birefringence value was increased with increasing of spinning speed and draw ratio. The mechanical properties of initial modulus, tensile strength were increased with increasing of spinning speed and draw ratio also, but the degree of elongation decreased as spinning speed and draw ratio.

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A Study on the Characteristics of Flows around Building Groups Using a CFD Model (CFD 모델을 이용한 건물군 주변의 흐름 특성 연구)

  • Lee, Hankyung;Kim, Jae-Jin;Lee, Young-Gon
    • Atmosphere
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    • v.25 no.3
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    • pp.501-510
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    • 2015
  • In this study, the characteristics of flows around building groups are investigated using a computational fluid dynamics (CFD) model. For this, building groups with different volumetric ratios in a fixed area are considered. As the volumetric ratio of the building group increases, the region affected by the building group is widened. However, the wind-speed reduced area rather decreases with the volumetric ratio near the ground bottom (z ${\lesssim}$ 0.7H, here, H is the height of the building group) and, above 0.7H, it increases. As the volumetric ratio decreases (that is, space between buildings was widened), the size of recirculation region decreases but flow recovery is delayed, resulting in the wider wind-speed reduced area. The increase in the volumetric ratio results in larger drag force on the flow above the roof level, consequently reducing wind speed above the roof level. However, above z ${\gtrsim}$ 1.7H, wind speed increases with the volumetric ratio for satisfying mass conservation, resultantly increasing turbulent kinetic energy there. Inside the building groups, wind speed decreased with the volumetric ratio and averaged wind speed is parameterized in terms of the volumetric ratio and background flow speed. The parameterization method is applied to producing averaged wind speed for 80 urban areas in 7 cities in Korea, showing relatively good performance.

A Study on the Control of Ship Maneuvering by the Simulation of Anchor Dredging (닻 운용 시뮬레이션에 의한 선체운동 제어에 관한 연구)

  • 윤순동
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.8 no.2
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    • pp.9-15
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    • 2002
  • Ship operators use anchor dredging for the collision avoidance or safety of ship handling in a harbour or narrow channel. This paper clarifies the technique of the anchor dredging known as a common sense for. the seafarers A mathematical model at low speed range is established for the estimation of ship motion under the assumed environment, simulate the advance speed , and turning ability under the anchor dredging or not. The results shows good agreement with the conventional seamanship and their experiences as follows. Ahead speed used the anchor dredging is slower(speed reduction ratio:40%) than the normal ahead speed and the stopping distance is shorter (distance reduction ratio:40%)than the normal ahead distance without the anchor dredging.. Turning speed used anchor dredging is slower(speed reduction ratio:72%)than the normal ahead speed and the tactical diameter is shorter(distance reduction ratio:24%)than the diameter by the normal turning without the anchor dredging.

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A Study on the Control of Ship Motion using the Anchor Dredging (닻을 운용한 선체운동 제어)

  • 윤순동
    • Proceedings of KOSOMES biannual meeting
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    • pp.127-134
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    • 2002
  • Ship operators are used to dredge anchor for the collision avoidance or safety of ship handling in a harbour or narrow channel. This paper clarifies the technique using tile anchor dredging known as a common sense for the seafarers. A mathematical model at low speed range has been established for the estimation of ship motion under the assumed environment , simulate the advance speed , and turning ability under the anchor dredging or not. The results shows good agreement with the conventional seamanship and their experiences as follows. Ahead speed used the anchor dredging is slower(speed reduction ratio:40%) than the normal ahead speed and the stopping distance is shorter (distance reduction ratio:40%)than the normal ahead distance without the anchor dredging. Turning speed used anchor dredging is slower(speed reduction ratio:72%)than the normal ahead speed and the tactical diameter is shorter(distance reduction ratio:24%)than the diameter by the normal turning without the anchor dredging.

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Experimental Investigation and Performance Test of Heavy Duty Torque Converter (중부하 토크 컨버터의 실험적 성능분석)

  • Lee, Hae-Jong;kim, Se-Hyun;Lee, Chung-Seub;Lee, Sang-Chul;Jeong, Hyo-Min;Chung, Han-Shik
    • Proceedings of the KSME Conference
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    • pp.690-695
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    • 2004
  • The present study is an investigation on the characteristics of heavy load toque converter by experimental process. To get the dynamic performance, the dynamometer was used with a parameters of speed, torque, oil pressure and oil flux, etc. The torque converter was tested for various input speed, output oil pressure and input oil flow rate. All experiments were investigated in case that the speed ratio is increased. The torque ratio and capacity factor was in inverse proportion to speed. Engine revolution had a more effects at region of low speed ratio. But, the opposite phenomena were represented increase of efficiency. In result of this experiments, the characteristics of torque converter were not influenced by oil pressure and oil flux.

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A Study on Damping Value of Bridge in High-speed Railway (고속전철 교량 감쇠 연구)

  • 최은석;진원종;곽종원;박성용;강재윤;김영진;김병석
    • Journal of the Korean Society for Railway
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    • v.4 no.1
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    • pp.23-30
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    • 2001
  • The dynamic characteristics such as natural frequency, mode shape and damping ratio are most important parameters in the high-speed railway bridges rather than general roadway bridges. Also, the need to know the dynamic behavior of bridges greatly increased in recent years. In the early of 1990s, to design the high-speed railway bridges, damping ratio recommended in general code was 2.5~7.5%. However, these values were not applied in all cases. Therefore, obtaining the damping value of specific structures is important to get the correct variable for design of high-speed railway bridges. The purpose of this study is mainly to obtain the damping ratio of high-speed railway bridges. The average damping ratio of high-speed railway bridges evaluated from a field test is about 2.4%.

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Transfer Function Derivation and LQG/LTR Speed Ratio Control for a Metal Belt CVT (금속벨트 CVT의 전달함수 도출과 변속비 LQG/LTR 제어)

  • 김종준;송한림;김현수
    • Transactions of the Korean Society of Automotive Engineers
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    • v.5 no.1
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    • pp.49-58
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    • 1997
  • In this paper, a transfer function was obtained for a PWM high speed solenoid valve controlled metal belt CVT system. The transfer function was defined as the ratio of speed ratio to PWM duty ratio and derived in time domain by linear regression analysis from the experimental results. The transfer function obtained showed different dynamic characteristics for the up and down shift. Also, LQG/LTR controller was designed for the CVT system using the transfer function. It is seen from the experimental results that LQG/LTR control showed good performance for the speed ratio tracking and disturbance rejection. The phase difference and relatively slow response are considered due to the inaccuracy os the transfer functions, which resulted from the inherent nonlinearities of the transmission characteristics of the metal belt CVT.

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Physical Properties of Nylon Textured Yarn according to False Twist Texturing Parameters (I) - Effect of Speed and Draw Ratio - (가연조건에 따른 나일론 섬유의 물성 (I) - 가연속도와 연신비의 영향 -)

  • Hu, Jong-Tea
    • Textile Coloration and Finishing
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    • v.20 no.1
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    • pp.28-35
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    • 2008
  • Texturing is the process of including a characteristic of a natural fiber in a synthetic fiber. The most common method of it the false twist texturing. Nylon textured yarn is primarily manufactured by the disk type. The major process parameters or the disk type false twist machine ratio, disk/yarn, and heater temperature. This study therefore investigated the effects of false twist texturing, especially speed and draw ratio, on the physical properties of nylon textured yarn. The increase of speed was proportional to the increase of unwinding tension, which could reduce the production efficiency by elevating the tension affecting to fiber during the process. In addition, the increase of speed was inversely proportional to the increase of crimp rigidity of nylon textured yarn. Draw ratio was proportionally increased with the increase of tenacity and the reductions of fineness and elongation, showing the influence or draw ratio to the ultimate physical properties of textured yarn.

Evaluation of Combustion Stability of Idling Speed State (LBT연소를 통한 Idling 운전시의 연소안정성 평가)

  • 이중순;이종승;김진영;정성식;하종률
    • Transactions of the Korean Society of Automotive Engineers
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    • v.7 no.5
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    • pp.66-72
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    • 1999
  • It is necessary to discuss lightening engine parts and reducing the friction of sliding parts to improve fuel consumption and combustion stability at idling condition. Lean best torque combustion which produce maximum power at a lean air-fuel ratio is effective for the reduction of exhaust gas emission and the improvement of fuel consumption. Accordingly, this study deals with the expansion of lean combustible limitation, the combustion stability and the reduction of idle speed through the analysis of combustion characteristics on the base of the control technique of precise air-fuel ratio because it does not need to maximum power at idling condition. The idle speed is increased proportional to ISC(Idle Speed Control) duty ratio. On the other hand the idle speed decreased by lean air-fuel ratio. The COV in engine speed is stable within maximum two percent up to 17.6 mixture ratio by the control of ISC duty ratio.

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Gear Train Design of 8-Speed Automatic Transmission for Tractor (트랙터 8단 자동변속기 기어 열 설계)

  • Jung, G.H.
    • Journal of Drive and Control
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    • v.10 no.2
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    • pp.30-36
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    • 2013
  • Tractor is a farm vehicle that is designed to provide a high tractive effort at low speed. It is used for versatile agricultural tasks such as hauling a trailer, tillage, mowing and construction work. Most older tractors use a manual transmission. However, as the intensity of work increases, tractors equipped with automatic transmission become popular due to the work convenience. In order to give the operator a large degree of control in field work, 24 gears with automatic 8-speed and manual 3-speed are arranged in transmission. This paper deals with the gear train that is designed for 8-speed automatic transmission by the engagement of multi-disk clutches. The gear ratio for each speed as well as power transmission mechanism is analyzed through velocity analysis. In addition, constraints of mesh gear ratio are derived by investigating the power flow path in velocity diagram for the given 8-speed gear ratio.