• Title/Summary/Keyword: 텀블

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Characteristics of In-cylinder Steady Flow using PIV for Different Intake Port Geometries in a 4-valve Gasoline Engine (PIV에 의한 4밸브 가솔린기관의 흡기포트 형상에 따른 정상유동 해석)

  • 조규백;전충환;장영준;강건용
    • Transactions of the Korean Society of Automotive Engineers
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    • v.5 no.5
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    • pp.188-196
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    • 1997
  • Many researchers have developed the measurement technique of in-cylinder flow characteristics and found the effect of intake port geometries on engine performance. The flow characteristics of four-valve cylinder head were examined in a steady flow rig for different intake ports. Tumble intensity of intake configurations with different entry angles were quantified with a tumble meter. The velocity and angular momentum distributions in the tumble adaptor were measured under steady conditions with PIV(Particle Image Velocimetry). We have obtained the results that flow structure becomes complicated by valve interference at low valve lift. As the valve interferences were reducing and the flow pattern changed to large vortex structure with tumble direction, intake ports with different entry angles have different tumble centers. Tumble eccentricity of intake port with low entry angle was large, so that the port had relatively much angular momentum compared to others which was expected to improve combustion performance.

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Numerical Study on the Formation of Tumble Motion in Engine Cylinder (엔진내부 텀블 유동 형성에 대한 수치해석적 연구)

  • Lee, Byoung-Seo;Lee, Joon-Sik;Yoo, Jung-Yul
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.2233-2238
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    • 2003
  • It is well known that organized vortex rotations swirl and tumble greatly affect the mixing, the combustion and heat transfer processes in engine cylinder. We have developed 3 dimensional numerical simulation codes whose predictions make good agreement with the experimental data. Large eddy simulation based on Smagorinsky subgrid scale model was adopted to describe the turbulence of in-cylinder flows. The tumble motions generated by different inclination angles between valve-port and cylinder head have been calculated. The results show that the angles between direction of induced flow and cylinder walls which the flow collides with play a great role in the formation and generation of tumble motions. Therefore, it is inferred that seat angle and inclination angle are important factors of engine design. In addition, the numerical results of different engine speed -1000 rpm and 3000 rpm are very similar in the flow structure.

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The behavior of swirl and tumble ratio in the combustion chamber of 4-valve engine with valve positions (밸브위치에 따른 4밸브 엔진 연소실 내부의 스월비와 텀블비의 거동)

  • Kim, Sung-Joon;Lee, Chon-Sik;Chun, Bong-Jun;Lee, Yong-Il
    • Journal of Industrial Technology
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    • v.19
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    • pp.51-57
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    • 1999
  • This research has an object to find out how the position of inlet valve influence swirling and tumbling of turbulence inside the combustion chamber of 4 valve engine. The computational analysis of three dimensional complicated turbulence flow in the cylinder is done by the KIVA-3V program to carry out this object. One use 6 valve positions with the bowl type of piston cavity. The swirl ration and the tumbling ratio of flow filed are evaluated quantitatively to find out how each valve position influence flow phenomena in the combustion chamber during the intake and compression processes.

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Analysis of Stumble of Manual Transmission Vehicle during Standing Start (수동변속기 차량의 발진 스텀블 해석)

  • Kang, Jae-Hoon;Kim, Tak-Soo;Park, Kyung-Suk;Han, Tae-Sik
    • Transactions of the Korean Society of Automotive Engineers
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    • v.17 no.3
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    • pp.102-109
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    • 2009
  • The stumble (abrupt and big acceleration decrease) occurring in manual transmission vehicle while standing start is analyzed by simulation model. This model was verified by comparing to test results. Mechanism of the stumble is clarified by analyzing simulation results and the key mechanism of the stumble is angular vibration of powertrain including wheel and tires. As a result, several method that can reduce the stumble is proposed by carrying out parametric study, increasing low end torque of engine, increase gear ratio etc.

Turbulence Enhancement Characteristics Analysis of Inclined-Tumbles for Various SCV Configurations (SCV형상별 경사텀블유동의 난류증가 특성 해석)

  • Lee, J.W.;Kang, K.Y.;Choi, S.H.;Park, S.C
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.6
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    • pp.234-242
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    • 1998
  • It has been demonstrated that the in-cylinder turbulence is enhanced by inclined swirl with a SCV(swirl control valve). The inclined-tumble flow measurement and analysis were performed for various types of intake systems that generated several different combinations of swirl ratio and tumble ratio in the cylinder. Experiments were conducted in a 4-valve optically accessed transparent research engine using a backward-scatter LDV mode under motoring condition at 1,000rpm. The influence of swirl/tumble levels on the characteristics of turbulence was analysed. This study presents experimental results of the inclined-tumble flow structure, including the flow motion phenomena, angular momentum and turbulence intensity.

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Rapid Initial Detumbling Strategy for Micro/Nanosatellite with Pitch Bias Momentum System (피치 바이어스 모멘텀 방식을 사용하는 초소형 위성의 초기 자세획득 방안 연구)

  • Lee, Byeong-Hun;Choe, Jeong-Won;Jang, Yeong-Geun;Yun, Mi-Yeon
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.34 no.5
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    • pp.65-73
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    • 2006
  • When a satellite separates from the launch vehicle, an initial high angular rate or a tip-off rate is generated. B-dot logic is generally used for controlling the initial tip-off rate. However, it has the disadvantage of taking a relatively long time to control the initial tip-off rate. To solve this problem, this paper suggests a new detumbling control method to be able to adapt to micro/nanosatellite with the pitch bias momentum system. Proposed detumbling method was able to control the angular rate within 20 minutes which is significantly reduced compared to conventional methods. Since the previous wheel start-up method cannot be used if the detumbling controller proposed by this paper is used, a method is also proposed for bringing up the momentum wheel speed to nominal rpm while maintaining stability in this paper. The performance of the method is compared and verified through simulation. The overall result shows much faster control time compared to the conventional methods, and achievement of the nominal wheel speed and 3-axes stabilization while maintaining stability.

Correlations among Different Tumble Measuring Methods and Significance of Tumble Ratios from Steady Flow Rig on SI Engine Combustion (엔진대상시험을 통한 텀블측정방식의 상관성 및 유의성에 관한 연구)

  • Lee, Si-Hun;Kim, Myoung-Jin
    • Transactions of the Korean Society of Automotive Engineers
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    • v.14 no.6
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    • pp.43-49
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    • 2006
  • Optimizing in-cylinder flow such as tumble or swirl is one of the key factors to develop better internal combustion engines. Especially, the tumble, which is more dominant flow in current high performance gasoline engines, has significant effects on the fuel consumptions and exhaust emissions under part load conditions. The first step for the tumble optimization is to find an accurate but cost-effective way to measure the tumble ratio. From this point of view, tumble ratios from three different measuring methods were compared and correlated in this research. Steady flow rig, water rig, and PIV were utilized for that purpose. Engine dynamometer test was also performed to find out the effect of the tumble. The results show that the tumble ratios from those methods are well correlated and that the steady flow rig is the effective method to measure the tumble despite its limitations.