• 설비공학논문집
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• 제25권11호
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• pp.612-616
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• 2013

A circular CAV damper has been developed, based on the investigation of the pressure loss, and the flow-resisting moment by the damper blade. When a torsional spring is attached to the damper axle, and the setting angle is adjusted to around $82^{\circ}$, the volume rate across the damper is almost independent of the static pressure. Such a CAV characteristic appears at an opening angle between $40^{\circ}$ and $60^{\circ}$, where the normalized moment decreases linearly with the angle. In addition, by adjusting the setting angle, the volume rate can be controlled to within 10% error, regardless of the pressure loss.

• 로봇학회논문지
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• 제16권1호
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• pp.23-28
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• 2021

The gripper with a soft pneumatic actuator uses a soft material, unlike the gripper that uses a rigid body, so it is safer and lighter to interact with objects without advanced control technology. Among the soft pneumatic actuators that have been studied, PneuNets actuators have bellows shape, which enable quick operation and complete bending with only small material deformation at low pressure. In this study, we suggested improved form of PneuNets actuators to obtain the performance of the soft actuator that a larger bending angle and larger bending force at a small pressure. An experiment was designed and conducted to measure the bending angle and bending force according to the pressure. As a result, it was confirmed through experiments that the improved model has a maximum bending angle at a pressure of 5 kPa lower than that of the previous model, and a maximum bending force of 1.97 times at the same pressure.

• 플랜트 저널
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• 제5권1호
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• pp.45-50
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• 2009

In this study, the experimental study has carried out to select pitch angle on the backward flow in an axial fan that has adjustable pitch blades. With the change of pitch angle of axial fan with adjustable blade, air flow rate, pressure and air flow direction can be changed. Because of this merit, adjustable axial fan can be used in the backward flow. For the selection of the backward flow pitch angle, fan performance test method is selected by KS B 6311. Dynamic pressure, static pressure, electric current and voltage are measured in each pitch angles of axial fan that are $36^{\circ}$, $-16^{\circ}$, $-21^{\circ}$, $-26^{\circ}$, $-31^{\circ}$ and $-36^{\circ}$. In the result of test, fan performance curves at several pitch angle has been investigated. Finally, pitch angle of $-26^{\circ}$ has been selected to get largest flow rate at backward flow situation.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.414-419
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• 2011

Missile am fighter aircraft have been challenged by low restoring nose-down pitching moment at high angle of attach. The consequence of weak nose-down pitching moment can be resulting in a deep stall condition. Especially, the pressure oscillation has a huge effect on noise generation, structure damage, aerodynamic performance and safety, because the flow has strong unsteadiness at high angle of attack. In this paper, the unsteady aerodynamics coefficients were analyzed at high angle of attack up to 60 degrees around two dimensional NACA0012 airfoil. The two dimensional unsteady compressible Navier-Stokes equation with a LES turbulent model was calculated by OHOC (Optimized High-Order Compact) scheme. The flow conditions are Mach number of 0.3 and Reynolds number of $10^5$. The lift, drag, pressure distribution, etc. are analyzed according to the angle of attack. The results at a low angle of attack are compared with other results before a stall condition. From a certain high angle of attack, the strong vortex formed by the leading edge are flowing downstream as like Karman vortex around a circular cylinder. Unsteady velocity field, periodic vortex shedding, the unsteady pressure distribution on the airfoil surface, and the acoustic fields are analyzed. The effects of these unsteady characteristics in the aerodynamic coefficients are analyzed.

• 대한기계학회논문집A
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• 제31권3호
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• pp.322-330
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• 2007

This paper quantifies the effect of a bend angle of a pipe bend on plastic loads, via small strain and large strain FE limit analyses using elastic-perfectly plastic materials. To consider the effect of the attached straight pipe, two limiting cases are considered. One case corresponds to the pipe bend without the attached straight pipe, and the other to that with a sufficiently long attached straight pipe. For the former case, the FE results suggest that the limit load is not affected by the bend angle for both in-plane bending and internal pressure. For the latter case, however, the bend angle affects plastic loads. An interesting finding is that the plastic load smoothly changes from the limit load of the straight pipe when the bend angle approaches zero to the plastic load of the $90^{\circ}$ pipe bend when the bend angle approaches 90 degree. Based on such observations, closed-form plastic load solutions are proposed for the pipe bend with an arbitrary bend angle under in-plane bending and internal pressure.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.145-150
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• 2008

In this study, the experimental study has carried out to select pitch angle on the backward flow in an axial fan that has adjustable pitch blades. With the change of pitch angle of axial fan with adjustable blade, air flow rate, pressure and air flow direction can be changed. Because of this merit, adjustable axial fan can be used in the backward flow. For the selection of the backward flow pitch angle, fan performance test method is selected by KS B 6311. Dynamic pressure, static pressure, electric current and voltage are measured in each pitch angles of axial fan that are $36^{\circ}C$, $-16^{\circ}C$, $-21^{\circ}C$, $-26^{\circ}C$, $-31^{\circ}C$ and $-36^{\circ}C$. In the result of test, fan performance curves at several pitch angle has been investigated. Finally, pitch angle of $-26^{\circ}C$ has been selected to get largest flow rate at backward flow situation.

• 한국자동차공학회논문집
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• 제24권3호
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• pp.338-344
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• 2016

The study is actively being performed to increase fuel injection pressure of common rail system among countermeasures to meet the emission regulation strengthen of the Diesel engine. The common rail fuel injection tube in such ultra high pressure common rail system has the weakest structural characteristics against vibration that is generated by fuel injection pressure and pulsation during engine operation and driving. Thus the extreme durability is required for common rail fuel injection tube, and the drawing process is being magnified as the most important technical fact for strength of seamless pipe that is the raw material of common rail tube. In this respect, we analyzed the characteristic of dimension and stress variation of the ultra high pressure common rail fuel injection tube by variation of Die and Plug angle in drawing process. Based on the analysis, we tried to obtain the raw material strength of common rail fuel injection tube for applying to the ultra high pressure common rail system. As a result, Plug angle is more important than entry angle of Die and we could obtain the target dimension and strength of the ultra high pressure common rail fuel injection tube through optimization of Plug angle.

• 대한인간공학회지
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• 제33권2호
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• pp.143-153
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• 2014

Objective: The aim of this study is to investigate the effects of trunk-forearm supported sitting on trunk flexion angle, trunk extensor fatigue and seat contact pressure. Background: The relationship between sitting posture and musculoskeletal disorders of the trunk extensor fatigue and seat contact pressure has been documented. The trunk-forearm support type ergonomic chair was devised from the fact that trunk-forearm support has been reported to reduce trunk extensor activity and discomfort. Method: Using three different sitting postures, upright ($P_1$), trunk-forearm supported ($P_2$) and normal sitting ($P_3$), six healthy subjects participated in the study. Motion capture system was used to collect head and trunk flexion angle, and surface electromyography (sEMG) was used to collect myoelectric signal of upper trapezius, lower trapezius, erector spinae, multifidus, and pressure mat system was used to measure seat contact pressure. Results: When trunk and forearm were supported by the ergonomic chair, higher head flexion angle showed upright > trunk-forearm supported > normal in order, and muscle fatigue showed less than upright and normal sitting. Mean seat contact pressure decreased 19% than upright sitting. But muscle fatigue was not affected by each condition. Conclusion: Trunk-forearm supported sitting of the ergonomic chair showed positive effect in respect of trunk and head flexion angle, trunk extensor fatigue, seat contact pressure. To acquire comprehensive understanding of the effectiveness of the ergonomic chair, further studies such as anatomical effects from measurement of external applied loading effect to the body from interface pressure analysis are required. Application: The results of the publishing trend analysis might help physiological effects of trunk-forearm support type chair.

• 한국산학기술학회논문지
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• 제12권5호
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• pp.2054-2060
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• 2011

본 연구의 목적은 경제적이고, 친환경적인 가솔린 직접 분사 인젝터의 분무특성을 연구하는 것에 있다. 분무도달거리, 분무각 그리고 혼합기 형성과 같은 인젝터의 특성을 가시화 실험을 통하여 측정하였다. 특히 분무압력과 분위기압력이 분무 침투거리와 분무각에 미치는 영향을 분석하였다. 가시화 실험을 위하여 정적 연소실과 연료 공급장치를 제작하였다. 초고속 카메라와 LED광원을 이용하여 분무형상을 촬영하였고, 촬영된 영상으로 분무 특성을 분석하였다. 연소실내의 분위기압력이 감소하고, 연료의 분무압력이 증가할수록 도달거리는 증가하였다. 분위기압력과 분무압력에 대해 분무각의 변화는 미소하지만, 분위기압력이 분무각에 더 큰 영향을 미치고 있다.

• 대한물리의학회지
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• 제5권1호
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• pp.53-61
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• 2010

Purpose : The purpose of this study is to compare the distribution of foot pressure, knee and ankle joint angle between treadmill walking and ground walking in normal person. Methods : 18 Person of subject has participated this study, let subject to walk in ground and treadmill in order to gain data of foot distribution and knee, ankle joint angle using by parotec system. and Dartfish system. Walking velocity was constrained by 2Km/h and more 10sec. Date analysis was used by paired-t test using SPSS/PC statistical programs for window. Results : Result show that total contact times has shown symmetry between both legs, and more increase of left foot pressure in treadmill walking. Foot pressure of treadmill walking was significantly decreased in right hind foot and fore foot and hallux area. The ankle joint angle of treadmill walking was significantly decreased in initial contact phase. Conclusion : Results of this study show that foot pressure of treadmill walking was more decreased than ground walking in right hind foot and fore foot, hallux area. And the ankle joint angle of treadmill walking was significantly decreased in initial contact phase.