• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.201-202
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• 2012

The isothermal flow structure and mixing characteristics of a hybrid/dual swirl jet combustor for micro-gas turbine were numerically investigated. Location of pilot nozzle, angle and direction of swirl vane were varied as main parameters with constant fuel flow rates for each nozzle. As a result, the variation in location of pilot nozzle resulted in significant change in turbulent flow field near burner exit, in particular, center toroidal recirculation zone (CTRZ) as well as turbulent intensity, and thus flame stability and emission characteristics might be significantly changed. The swirl angle of $45^{\circ}$ provided similar recirculating flow patterns in a wide range of equivalence ratio (0.5~1.0). Compared to the co-swirl flow, the counter-swirl flow leaded to the reduction in CTRZ and fuel-air mixing near the burner exit and a weak interaction between the pilot partially premixed flame and the lean premixed flame. With the comparison of experimental results, it was confirmed that the case of co-swirl flow and swirl $angle=45^{\circ}$ would provided an optimized combustor performance in terms of flame stability and pollutant emissions.

• Journal of Advanced Marine Engineering and Technology
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• 제28권3호
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• pp.475-481
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• 2004

Recently it is strongly required on lower fuel consumption. lower exhaust emission, higher engine performance. and social demands in a spark ignition gasoline engine. In this study. the experimental engine used at test. it has been modified the lean burn gasoline engine. and used the programmable engine management system, and connected the controller circuit which is designed for the engine control. At the parametric study of the engine experiment, it has been controlled with fuel injection, ignition timing. swirl mode, equivalence ratio engine dynamometer load and speed as the important factors governing the engine performance adaptively. It has been found the combustion characteristics to overcome the hysteresis phenomena between normal and lean air-fuel mixing ranges. by mean of the look-up table set up the mapping values. at the optimum conditions during the engine operation. As the result, it is found that the strength of the swirl flow with the variation of engine speed and load is effective on combustion characteristics to reduce the bandwidth of the hysteresis regions. The results show that mass fraction burned and heat release rate pattern with crank angle are reduced much rather, and brake specific fuel consumption is also reduced simultaneously.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.420-423
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• 2008

This present work is to find optimum design of a NACA65 axial fan blade with weighted average surrogate model. The numerical analysis by Reynolds-average Navier-Stokes equations with shear stress turbulence(SST) is discretized by finite volume approximations and solved on hexahedral grids for flow analysis. The blade aerodynamic shape is modified by six design variables for the optimization. The blade profile as well as stacking line is modified to enhance blade total efficiency. Six design variables, airfoil maximum camber, maximum camber location, leading edge radius, trailing edge radius, lean angle at 50% span and lean angle at 100% span, are selected for blade profile to enhance the total efficiency. The PBA model which is basically weighted average of the basis surrogates is used to find the optimal design in the design space from the constructed response surface model for the objective function. By the optimization, the total efficiency is increased by 1.4%.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.123-125
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• 2015

A study has been conducted to investigate the effect of swirl angle in low swirl combustor. In this study, the employed swirl angles were $28^{\circ}$, $32^{\circ}$ and $37^{\circ}$. Direct flame photos show that the width of the flame is expanded and the length of the flame is shortened when swirl angle is increased. Also, as the swirl angle was increased, the flame stability region could be widened due to the expansion of lower flammable limit. Between 3 and 7kW, CO emissions was below 10 ppm and NOx emissions was also below 27 ppm at $O_2$ 15% basis over the lean burning range of 0.6 < ${\Phi}$ < 0.9. From this investigation of stability expansion effect and emission performance, it was identified that the swirl angle $37^{\circ}$ is most suitable swirling condition in the low swirl model combustor.

• 대한기계학회논문집B
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• 제33권9호
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• pp.658-665
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• 2009

Lean premixed combustors are used for significant NOx reduction which one of issues in current gas turbine combustor. This study was investigated to estimate the effects of the unmixedness of fuel-air, equivalence ratio on the instability mechanism, NOx emission and combustion oscillation in a lean premixed combustor. The experiments were conducted in a dump combustor at atmospheric pressure conditions using methane as fuel. The swirler angle was $45^{\circ}$, the degrees of fuel-air mixing were 0, 50 and 100 and inlet temperature was 650K. The equivalence ratio was ranging from 0.5 to 0.8. This paper shows that NOx emission was increased when the degree of fuel-air mixing is increased in same equivalence ratio and when equivalence ratio is increased. And the range of the combustion instability was enlarged as a function of increasing of the degree of fuel-air mixing.

• 한국운동역학회지
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• 제15권2호
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• pp.129-138
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• 2005

The purpose of this study was to investigate the techniques used by long jumpers who recorded over 8meters in 2002 Busan Asian Game and 2003 Daegu Universiade. The kinematic characteristics from the last three stride to takeoff at the takeoff board were analyzed such as velocities, heights and angles. The real-life three-dimensional coordinates of 20 body landmarks during each trial were collected using a Direct Linear Transformation procedure. The conclusion were as follows; 1. The height variation who recorded over 8 meters of center of gravity of the jumpers at the last stride was under 8cm. In order to record over 8meters the national long jumpers should have under 10cm height variation. 2. In the approach phase the horizontal velocity of the jumpers should reach to 10.5m/s in last three strides and 9.79m/s in touch down at take off board. 3. The horizontal velocity at take off board must have over 8.51m/s and the vertical velocity must have 3.75m/s simultaneously in order to record 8meters. 4. The forward body lean angle should have over 20degrees with pushing the take off board in forwarding movement. The appropriate body variation range ratio between take off and touch down should be 1.2 vs 1 and the trunk angle at touch down on the board should be close to the erect posture for higher body flight.

• 한국운동역학회지
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• 제14권1호
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• pp.83-98
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• 2004

The purpose of this study was to determine the kinematic variables of the hurdling for a korea record holder (A) and a national hurdle representative (B). after the kinematic variables such the distance and the distance and height of C.G, the velocity and the angle were analyzed about the hurdling. The results were summarized as follows; 1. In terms of the distance and the height of C.G, subject A showed long in horizontal distance from C.G to the take-off phase, but showed short in the landing phase. Subject B showed short in horizontal distance from C.G to the take-off phase, and showed long in the landing phase. 2. In terms of the velocity of C.G, Subject A showed fast C.G velocity in horizontal direction to the braking phase, Subject A and B showed slower C.G velority in the landing phase, but Subject A showed height C.G velocity in vertical direction to the to the take-off, the landing, and propulsion phase 3. In terms of the angle of C.G and lean of C.G to front at the braking and the take-off phase. Subject A kept the less angle in the maximum trunk lean to front at the flight phase as comparison with Subject B. 4. In terms of the velocity of the knee and the ankle joint. Subject A showed fast in the resultant velocity of the left ankle joint the take-off phase, but showed slow in the left knee joint. Subject B showed fast in the resultant velocity of the left knee joint the take-off phase, but showed slow in the right knee and the right ankle joint.

• 한국추진공학회지
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• 제20권4호
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• pp.40-49
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• 2016

본 연구의 목적은 저선회 모델 연소기에서 저선회 연소의 특성을 확인하는 것이다. 이를 위해 선회각도에 따른 화염의 형상 및 안정화 영역, 배기성능에 대한 평가가 실험적으로 수행되었다. 저선회 연소의 큰 특징은 화염이 부상되어 존재하게 되는데, 이러한 부상화염은 확대유동과 예혼합 화염의 전파특성이 절묘하게 결합되어 발생하게 된다. 본 연소기에서 이러한 부상화염의 특징을 속도 유동장을 통하여 확인하였으며 화염을 가시화하여 나타내었다. 가시화된 화염은 열용량과 당량비에 따라 분류하였다. 선회각도의 변화에 따른 연구를 통해 선회각도만으로도 희박 가연한계를 확장시킬 수 있음을 보였다. 또한 선회각도가 증가할수록 혼합이 향상되고 체류시간이 짧아져 NOx와 CO의 배출이 감소되는 것으로 확인되었다.

• 한국지능시스템학회논문지
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• 제25권1호
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• pp.1-6
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• 2015

본 논문에서는 한 바퀴 이동로봇의 균형제어를 위해 퍼지방법을 사용하였다. PD제어를 사용하여 균형을 유지하는 한 바퀴 로봇은 시간이 지남에 따라 플라이휠이 한 방향으로 기울어지게 되고 결국에는 균형이 무너지는 현상이 발생한다. 선행연구에서는 이를 해결하기 위해 게인 스케줄링 방법을 사용하였다. 본 논문에서는 퍼지방법을 사용하여 균형 각도를 보상하므로 균형 제어 성능을 높이고자 하였다. 퍼지제어를 통해 desired offset의 각도를 보상하므로 김벌이 한쪽으로 흘러 넘어지는 현상을 보완하였다. 한 바퀴 구동 이동로봇의 균형제어 실험을 통하여 제안하는 제어방식의 성능을 검증하였다.

• 한국운동역학회지
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• 제15권3호
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• pp.95-104
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• 2005

To know the proper setup posture for the various clubs, changes of setup variables according to the change of golf club length was investigated. Swing motions of three male low handicappers including a professional were taken using two high-speed videocameras. Four clubs iron 7, iron 5, iron 3 and driver (wood 1) were selected for this experiment. Three dimensional motion analysis techniques were used to get the kinematical variables. Mathcad and Kwon3D motion analysis program were used to analyze the position, distance and angle data in three dimensions. The variables divided into three categories 1) position and width of anterior-posterior direction 2) position and width of lateral direction 3) angles and evaluated based on the theories of many good golf teachers. Major findings of this study were as follows. 1.The stance (distance between ankle joints) was increased as the length of the club increased but the increasing width was not large. It ranges from 5cm to 10cm and professional player showed small changes. 2. Forward lean angle of trunk was decreased (more erected) as the length of the club increased. It ranges from 30 degrees for iron7 to 25 degrees for driver. 3. Angle between horizontal and right shoulder were increased as the length of the club increased. It ranges from 10 degrees to 20 degrees and professional player showed small changes. 4. Anterior-posterior position of the shoulders were located in front of the foot for all clubs and the difference between the shoulder and knee position was decreased as the length of the club increased. 5. Anterior-posterior position of grip (hand) was located almost beneath the shoulders (2.5cm front) for iron7, but it increased to 10cm for the driver. This grip adjustment makes the height of the posture increased only 5cm from iron7 to driver. 6. Lateral position of grip located at 5cm left for the face of iron7, but it located at the right side (behind) for the face of driver. 7. Lateral position of the ball located at the 40%(15cm) of stance from left ankle for iron7 and located at the 10% (5cm) of stance for driver. 8. Head always located at the right side of the stance and the midpoint of the eyes located at the 37% of stance from the right ankle for all clubs. This means that the axis of swing always maintained consistently for all clubs. 9. Left foot opened to the target for all subject and clubs. The maximum open angle was 25 degrees. Overall result shows that the changes of the setup variables vary only small ranges from iron7 to driver. Paradoxically it could be concluded that the failure of swing result from the excessive changes of setup not from the incorrect changes. These findings will be useful for evaluating the setup motion of golf swing and helpful to most golfers.