• Title/Summary/Keyword: Reaction Front

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Structural Analysis of Excavator Arm and its Connection Pins (굴착기 암가 연결핀의 구조해석)

  • Han, Moon-Sik;Cho, Jae-Ung
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.20 no.1
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    • pp.7-12
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    • 2011
  • Hydraulic excavator in digging at the construction machinery is a widely used mechanical device. Excavator attachments are taken with structural load and fatigue during digging under applied reaction. Fatigue analysis is done at joint pin between bucket and arm of front attachment at excavator under the force of hydraulic cylinder in operation. It is analyzed how load can be supported at the lower driving body applied on the bucket. In this study, the deformation of arm and the fatigue result are examined when reaction force is applied on the attachment of excavator.

The Movement of Foot and the Shift of Ground Reaction Force in Batters according to the Ball Speed Increase (투구 속도 증가에 따른 타자의 발 움직임과 지면 반력의 변화)

  • Lee, Young-Suk;Eun, Seon-Deok
    • Korean Journal of Applied Biomechanics
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    • v.14 no.3
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    • pp.191-202
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    • 2004
  • The batting performance in baseball is a repetitive movement. In order to make the stabilization of posture and the efficient shift of body weight, both the range of stance and stride are important. The previous studies explained that the consistent stride which included the amount of time, stance, and direction were needed. However, the batting performance is frequently changed according to the several speed of ball. Therefore, this study was to analyze the reaction time, the range of stance, the change of stride, and the change of GRF during the batting movement in three kinds of ball speed (120km/h, 130km/h, & 140km/h). Seven elite players are participated in this study. 1. The reaction time of the stride phase was short whereas the time of the swing phase was long according to the increasing ball speed. 2. The range of the stance was wide and the mediolateral direction of the stride was decreased according to the increasing ball speed. 3. In the three kinds of ball speed, the change of body weight was transferred to the center, the rear foot, and the front foot directions. The ball speed of 130km/h showed the high frequency of the suitable batting. At this ball speed, the movement of the body weight was shifted smoothly and the value of the Ground Reaction Force was large enough.

NOx and CO Emission Characteristics of Porous Inert Medium Burner (다공물질 연소기의 NOx 및 CO 배출 특성)

  • 임인권
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.2
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    • pp.559-567
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    • 1995
  • The combustion process within a porous inert medium (PIM) burner is numerical studied. A detailed chemical reaction scheme including thermal and prompt NO$_{x}$ reactions is used to predict the formation and destruction of pollutants such as NO$_{x}$ and CO. The reaction paths for NO$_{x}$ formation are divided to quantify the amount of NO$_{x}$ formed through thermal NO$_{x}$ reaction or through prompt NO$_{x}$ reaction. Emission index is calculated to compare the actual mass of NO$_{x}$ or CO produced through the combustion of unit mass of fuel. It is found NO formation in PIM burner is confined in flame zone and formation is suppressed due to heat loss at down-stream of the flame. Higher production of NO through prompt NO reaction path is observed due to the higher concentration of fuel derivative species and its higher diffusion at flame front. For all equivalence ratios, CO emission within PIM burner is lower than that from the one-dimensional freely-propagating flame. PIM burner flame has better NO$_{x}$ emission index from .psi. = 0.75 to .psi. = 1.1. to .psi. = 1.1.

Numerical Investigation on Initiation Process of Spherical Detonation by Direct Initiation with Various Ignition Energy

  • Nirasawa, Takayuki;Matsuo, Akiko
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2008.03a
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    • pp.45-52
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    • 2008
  • In order to investigate the initiation and propagation processes of a spherical detonation wave induced by direct initiation, numerical simulations were carried out using two-dimensional compressible Euler equations with an axisymmetric assumption and a one-step reaction model based on Arrhenius kinetics with various levels of ignition energy. By varying the amount of ignition energy, three typical initiation behaviors, which were subcritical, supercritical and critical regimes, were observed. Then, the ignition energy of more than $137.5{\times}10^6$ in non-dimensional value was required for initiating a spherical detonation wave, and the minimum ignition energy(i.e., critical energy) was less than that of the one-dimensional simulation reported by a previous numerical work. When the ignition energy was less than the critical energy, the blast wave generated from an ignition source continued to attenuate due to the separation of the blast wave and a reaction front. Therefore, detonation was not initiated in the subcrtical regime. When the ignition energy was more than the minimum initiation energy, the blast wave developed into a multiheaded detonation wave propagating spherically at CJ velocity, and then a cellular pattern radiated regularly out from the ignition center in the supercritical regime. The influence on ignition energy was observed in the cell width near the ignition center, but the cell width on the fully developed detonation remained constant during the expanding of detonation wave due to the consecutive formation of new triple points, regardless of ignition energy. When the ignition energy was equal to the critical energy, the decoupling of the blast wave and a reaction front appeared, as occurred in the subcrtical regime. After that, the detonation bubble induced by the local explosion behind the blast wave expanded and developed into the multiheaded detonation wave in the critical regime. Although few triple points were observed in the vicinity of the ignition core, the regularly located cellular pattern was generated after the onset of the multiheaded detonation. Then, the average cell width on the fully developed detonation was almost to that in the supercritical regime. These numerical results qualitatively agreed with previous experimental works regarding the initiation and propagation processes.

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Performance Evaluation of PTFE Oil-seal for Automotive Engine Front Part (자동차 엔진 프론트부의 PTFE 오일씰의 성능평가)

  • Choi, Hyun-Jin;Park, Chul-Woo;Lee, Jong-Cheol;Kim, Jong-Gab;Choi, Seong-Dae
    • Transactions of the Korean Society of Automotive Engineers
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    • v.19 no.2
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    • pp.66-71
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    • 2011
  • This study analyzed the mechanical characteristics and evaluated their subsequent performance for two types of seals which reinforced characteristics with lower friction and anti-wear functions among the foremost important features in the automotive engine seals; one with the addition of glass fiber to PTFE(Polytetrafluoro ethylene); the other with the addition of self-lubricant molybdenumin addition to the glass fiber. Based on the configuration design of seal installed to the front part in the automotive engine, this study carried out interpretations on the stress and reaction for those two types of oil seals to compare the maximum stress and contact load generated from the seal steel, rubber and PTFE lip. This study also verified the stress concentration and anti-wear performance through the coefficient of friction, torque and durability test by producing two types of PTFE seals actually.

Predicting Extreme-Thickness of Phase Fronts in HMX- and Hydrocarbon-based Propellants (로켓 추진제의 익스트림-스케일 상면 두께 예측)

  • Yoh, Jai-Ick
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.37 no.1
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    • pp.82-88
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    • 2009
  • The structure of steady wave system is considered which is admitted by the continuum equations for materials that undergo phase transformations with exothermic chemical reaction. With its theoretical basis in one-dimensional continuum shock structure analysis, the present approach estimates the micro-width of waves associated with phase transformation phenomena, n-heptane is selected as the hydrocarbon fuel for evaporation and condensation analysis while HMX is used for melting and freezing analysis of solid rocket propellant. The estimated thickness of evaporation - condensation front of n-heptane is on the order of $10^{-2}$ micron while the HMX melting - freezing front thickness is estimated at 1 micron.

Reflections of shocks in nonequilibrium flow of air

  • Park, Tae-Hoon
    • Communications of the Korean Mathematical Society
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    • v.10 no.3
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    • pp.767-781
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    • 1995
  • In this paper we present computation of a reflected shock in the hypersonic flow of air with chemical reactions. We consider two dimensional steady inviscid hypersonic flow of air around bodies including chemical reaction effects. At a high Mach number, a strong shock is formed in front of the body when a wedge is placed against the flow. In front of the shock, temperature and pressure increase greatly and the flow is in nonequilibrium state. If the shock hits a wall, then a reflected shock is formed in the nonequilibrium flow region. Behind this reflected shock, the temperature and pressure are very high. We carry out the computation of the reflected shock and the flow behind it. The jump conditions at the reflected shock are presented. A technique combining smooth transforms of domain and implicit difference methods is used to overcome numerical difficulties associated with the lack of resolution behind the shock and near the body.

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Experimental Investigation of Scalar Dissipation Rates in Lean Hydrocarbon/Air Premixed Flames

  • Chen, Yung-Cheng;Bilger, Robert W.
    • Journal of the Korean Society of Combustion
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    • v.6 no.2
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    • pp.43-49
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    • 2001
  • Instantaneous, three-dimensional scalar dissipation rates of the reaction progress variable are measured in turbulent premixed Bunsen flames of lean hydrocarbon/air mixtures with the two-sheet, two-dimensional Rayleigh scattering technique. The flames investigated are located in the turbulent flame-front regime on a newly proposed combustion diagram for premixed flames. The conditionally-averaged mean scalar dissipation rates, $N_{\zeta}$ are found to be lower than the calculated laminar values, indicating a locally broadened flame front. In agreement with previous measurements, the maximum of $N_{\zeta}$, decreases strongly with increasing Karlovitz numbers. The conditional probability density functions are close to a log-normal distribution for scalar dissipation rates conditioned at the progress variable value where the scalar dissipation is maximum in unstretched laminar flame calculations. The time scale for the Favre-averaged mean scalar dissipation rate decreases in general across the turbulent flame brush from the unburnt to burnt side.

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Measuring Nano-Width of Wave Fronts in Combustion: a Numerical Approach (연소시 발생하는 파면의 나노 사이즈 두께 측정: 수치적 접근)

  • Yoh, Jai-Ick
    • 한국연소학회:학술대회논문집
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    • 2005.10a
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    • pp.20-27
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    • 2005
  • I consider the structure of steady wave system which is admitted by the continuum equations for materials that undergo phase transformations with exothermic chemical reaction. In particular, the dynamic phase front structures between liquid and gas phases, and solid and liquid phases are computationally investigated. Based on the one-dimensional continuum shock structure analysis, the present approach can estimate the nano-width of waves that are present in combustion. For illustration purpose, n-heptane is used in the evaporation and condensation analysis and HMX is used in the melting and freezing analysis of energetic materials of interest. On-going effort includes extension of this idea to include broad range of liquid and solid fuels, such as rocket propellants.

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Analysis of the Ground Reaction Forces by the Dancesport Rumba Backward Walk Step (댄스스포츠 라틴댄스 룸바 Backward Walk 동작시 지면반력 변인 분석)

  • Yoo, Hye-Suk;In, Hee-Kyo;Choi, In-Ae
    • Korean Journal of Applied Biomechanics
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    • v.18 no.1
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    • pp.129-135
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    • 2008
  • This research was examined the effect of Backward Walk on ground reaction force and we achieved it by using ground reaction force machine during the Backward Walk activity with Latin and Rumba dance. We find that it was significant difference of vertical(Fz) ground reaction force of right foot in touchdown and toe-off and vertical(Fz), horizontal(Fx), front-rear(Fy) ground reaction force of left foot. There was not significant differences in vertical ground reaction force between superior athlete and unskilled athlete, but there was a significant difference in left foot. Through this, we know that the sports capability of left foot which has been developed through the training is better in superior athlete group. Therefore understanding of difference in ground reaction force and repeated training can help the unskilled athlete and beginner to accomplish the accurate movement.