피치각 수정에 따른 축류식 터보팬 성능 변화에 관한 연구

강석윤,이태구,류인근,이재헌 대한설비공학회 2005 설비공학 논문집 Vol.17 No.3

The aim of this paper is to suggest one efficient method for the various requirements of performance during the process designing and producing an impeller. The study considers that the revisions of a pitch angle of an impeller at an axial turbo fan affect an air flow rates and a static pressure rise. The axial turbo fan specified with the 250 Pa maximum static pressure and 1300 CMH fan air flow rates was tested and analyzed by CFD. The Numerical results show that the air flow rates are calculated to 1,175 CMH, 1,223 CMH, 1,270 CMH, 1,340 CMH and 800 CMH in cases that the pitch angles are 44 , 49 , 54 , 59 and 64 respectively. Also the static pressure rises are shown to 108 Pa, 122Pa, 141 Pa, 188 Pa and 63 Pa at the same cases. The air flow rate is increased linearly according to the changes of the pitch angle from 44 to 59 and the maximum air flow rate passing the impeller is increased to 13% over at the case of 59 pitch angle compared with the reference case of 54 pitch angle. The static pressure rise is increased linearly according to the changes of the pitch angle from 44 to 54 , too. The static pressure rise at the 59 pitch angle is increased to 33% over compared with the 54 pitch angle. The result shows that the revisions of pitch angle make the static pressure rise increase widely. However the air flow rates and the static pressure rise at the 64 pitch angle are suddenly decreased because of over-changed pitch angle.

피치각과 날개 길이에 따른 축류팬의 성능

전성택(Sung-Taek Jeon),조진표(Jin-Pyo Cho) 대한설비공학회 2013 설비공학 논문집 Vol.25 No.1

In this study, the performance of an impeller according to blade length and pitch angle was studied experimentally by building a variable pitch impeller while changing blade length to review the effect of blade length and pitch angle on a fan’s performance. The pitch angle was changed in six steps from 20°~45° at intervals of 5° while the blade lengths were changed to 90 mm, 100 mm, 110 mm and 120 mm with an identical airfoil shape while carrying out the experiment. The results are summarized as follows: The air flow per static pressure of axial fans increased linearly with increase of pitch angle, but the high static pressure showed a decrease at a pitch angle of 35°. The shaft power increased proportionally to the pitch angle at all blade lengths; the larger the pitch angle, the larger the measured increase of shaft power. This is because the drag at the fan’s front increases with the pitch angle. In the axial fans considered in this research, the flow and increase of static pressure amount increased up to a pitch angle of 30° but decreased rapidly above 35°.

피치각과 날개 길이 변화에 따른 축류팬의 성능 및 소음 특성에 관한 실험적 연구

전성택(Sung-Teck Jeon),김내현(Nae-Hyun Kim),조진표(Jin-Pyo Cho),음현진(Hyun-Jin Eum),김도균(Do-Kyun Kim) 대한기계학회 2011 대한기계학회 춘추학술대회 Vol.2011 No.10

In this study, the blade and hub are separate blades can adjust the pitch angle is constructed. Variation of pitch axial flow fan performance was confirmed by experiments investigated the effect of the length of the blade. Pitch angle of 5° to 20°~45° at intervals of 6 set were measured by varying the fan blade airfoil in the form of the same length five steps(80mm, 90mm, 100mm, 110mm, 120mm) axial flow fans by changing the performance. According to the same pitch angle, air flow from the static pressure has a similar slope. Same pitch angle, power consumption, depending on the value of airflow and gentle slopes that have a longer blade length, pitch angle change was difficult to find a relationship in which each pitch, each of surging point is judged to be due to the impact of the change. Due to changes in the length of the fan blade pitch angle, which shows the noise characteristics by pitch angle increases, the noise also increases the value and the same pitch angle.

한국 정상 젊은 남성에서의 거골-제 1 중족골간 각과 거골 수평각 및 종골 경사각

이영구,임수재,이상혁,박찬호,이상헌,Lee, Young-Koo,Yim, Soo-Jae,Lee, Sang-Hyok,Park, Chan-Ho,Lee, Sang-Hun 대한족부족관절학회 2010 대한족부족관절학회지 Vol.14 No.2

Purpose: The purpose of this study is to find out the normal angles of the talus-1st metatarsal angle, the talo-horizontal angle and calcaneal pitch angle for diagnosis of foot deformity in Korea. This would be helpful as it would provide a basic angular measurement of flat and cavus foot that indicates the need for operation. Materials and Methods: Within a period of four months from January 2007 to April 2007, We have established 600 feet of 300 males without trauma history of foot. The source to image distance is 40 inches and erect weight bearing radiographs are obtained in anteroposterior and lateral projections. The significant angular measurements that define flat or cavus foot are the talus-1st metatarsal angle, the talo-horizontal angle and calcaneal pitch angle. Results: The mean age was 21 years (19-22 years) old. The mean talus-1st metatarsal angle was $0{\pm}6.9{^{\circ}}$, the mean talo-horizontal angle was $25.8{\pm}4.5{^{\circ}}$ and the mean calcaneal pitch angle was $23.9{\pm}5.1{^{\circ}}$. Conclusion: We can consider that mean talus-1st metatarsal angle, talo-horizontal angle and calcaneal pitch angle are $0{\pm}6.9{^{\circ}}$, $25.8{\pm}4.5{^{\circ}}$ and $23.9{\pm}5.1{^{\circ}}$ as an normal angle limit of young age in Korea.

람다 날개 형상의 옆미끄럼각 효과에 대한 실험적 연구

심호준(HoJoon Shim),박승오(Seung-O Park),오세윤(Se-Yoon Oh) 한국항공우주학회 2015 韓國航空宇宙學會誌 Vol.43 No.3

람다 날개 형상의 공력 계수에 대한 실험적 연구를 국방과학연구소의 중형아음속 풍동에서 수행하였다. 본 연구의 주목적은 옆미끄럼각의 변화에 따라 다양한 공력 계수가 어떻게 변화하는지를 조사하는 것이다. 옆미끄럼각이 0°인 경우, 피칭 모멘트가 급격히 불안정해지는 현상을 확인하였으며, 옆미끄럼각이 증가함에 따라 pitch break 현상이 더 높은 받음각에서 발생하는 것을 확인하였다. 롤링 모멘트는 옆미끄럼각이 있는 경우 pitch break와 유사한 특성을 보여준다. 이런 경향은 옆미끄럼각이 증가할수록 더 심하게 나타났다. 요잉 모멘트는 높은 받음각에서 옆미끄럼각에 따라 기울기가 크게 변화하였고 불안정한 방향 안정성이 뚜렷이 나타났다. 모멘트의 이런 특성들은 비행 제어를 위해서는 보다 효과적인 조종성 증가 장치가 필수적이란 것을 의미하고 있다. An experimental study on aerodynamic coefficients of a lambda wing configuration was performed at the low speed wind tunnel of Agency for Defense Development. The main purpose of this study was to investigate the effects of sideslip angle on various aerodynamic coefficients. In the case of 0° sideslip angle, nose-up pitching moment rapidly increases at a specific angle of attack. This unstable pitching moment characteristic is referred to as pitch break or pitch up. As the sideslip angle increases, the pitch break is found to be generated at a higher angle of attack. Rolling moment is found to show similar behavior pattern to ‘pitch break’ style with angle of attack at non-zero sideslip angles. This trend gets severer at greater sideslip angles. Yawing moment also shows substantial variation of the slope and the unstable directional stability with sideslip angles at higher angles of attack. These characteristics of the three moments clearly implies the difficulty of the flight control which requires efficient control augmentation system.

Effects of the pitch angle control on a Gurney flap-equipped vertical axis wind turbine

한예인,Sahuck Oh 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.8

In the current study, effects of a Gurney flap and pitch angle on the aerodynamic performance of a vertical-axis wind turbine are investigated by comparing CFD results of the standard and flap-equipped wind turbines at various pitch angles. Both wind turbines show better performance at the negative pitch angles and the flap-equipped wind turbine shows higher performance than the standard one at most of the pitch angles. The best flap-equipped wind turbine obtained a 7.5 % higher power coefficient than the best standard wind turbine by varying the pitch angle. Flow analysis reveals that wind turbine’s pitch angle control and small device attachment should be implemented to make its blades remain in the pre-stall region. For the high-performance wind turbine, positive flow characteristics in terms of no formation of the vortex around the trailing edge and weak traces of the vortex have been identified.

유니버설 로터 허브 시스템이 장착된 휠타워의 로터 블레이드 피치각 변화에 대한 유동해석

김수연,김덕관,정기훈 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.11

훨타워에 장착된 유니버설 로터 허브 시스템은 다양한 기종의 로터 블레이드 회전시험이 가능하고 3-블레이드 형상으로 기존 4-블레이드 허브 시스템보다 상대적으로 로터 블레이드간 공기역학적 간섭이 적은 장점이 있다. 본 논문에서는 유니버설 로터 허브 시스템이 장착된 훨타워 주위 유동과 주변 구조물의 영향성을 분석하였다. 또한 훨타워 운용조건에 따라 저피치각과 고피치각에 대해 각각 유동해석을 비교하였다. 유동해석 결과 저피치각의 경우 로터 블레이드 회전면 위로 와류가 생성되어 벽면효과는 거의 나타나지 않았다. 고피치각의 경우 로터 블레이드 회전면 아래로 와류가 발생하고 벽면효과가 나타났다. 따라서 본 연구 결과는 고피치각에서 벽면효과를 최소화 할 수 있는 방안 수립시 참고자료로 활용될 것으로 사료된다. 또한 훨타워 로터 시스템의 피치각 변화에 따른 운용에 대해 사용될 수 있다. The universal rotor hub system on whirl tower has three blade configuration and adapter device to adjust different types of blades. So, it has advantages such as low aerodynamic interferences between blades. This paper analyze flow around whirl tower with universal rotor hub system and influence of surrounding structure such as control building and moving shelter. The flow analysis around rotor blades was shown at each low and high pitch angle in accordance blade dynamic balancing condition. Through flow analysis, vortex was generated at upper zone of rotor rotating plane at low pitch angle. So, it did not make wall effect on the blade. But vortex generated at high pitch angle was located in lower zone of rotor rotating plane and this made wall effect on rotor blade. Therefore this analysis can be used to find out how to minimize wall effect on rotor blade at high pitch angle. This paper can also be used to analyze flow around the rotor blade at each pitch angle change.

Comparison of screw-in effect of three NiTi file systems used by undergraduates

Oh, Seung-Hei,Park, Jeong-Kil,Hur, Bock,Kim, Hyeon-Cheon 대한치과보존학회 2006 Restorative Dentistry & Endodontics Vol.31 No.6

학생들이 사용한 세 가지 NiTi file systems (ProFile^(®) Hero Shaper^(®), K3™)을 사용하여 성형한 모형 근관 apical terminus width를 비교하여 flute angle 및 pitch 혹은 radial land가 screw-in effect에 미치는 효과를 알아보고자 하다. NiTi fle의 사용 경험이 없는 부산대학교 치과대학 4학 학생 50명이 세 종류의 NiTi fle systems-Pro File^(®)(Dentsply Maillefer, Ballaigues, Switzerland), K3™ (SybronEndo, Clendora, France), Hero Shaper^(®)(Micromega, Besancon,France)-을 사용하여 각 system으로 하나의 근관씩, 모두 150 개의 레진 블락 근관모형 (Endo Training Bloc ; Dentsply Maillefer, Ballaigues, Switzerland)을 16 : 1 감속 handpiece를 장착한 electric motor (Tecnika ATR, Pistola, Italy)를 사용하여 300rpm의 속도에서 torque30 (Tecnika motor setting value)으로 성형하였다. 스캐너로 근관 성형 전 후 이미지를 채득하여 중첩한 후 근단부의 최종 폭경을 측정 하였다. 통계분석은 one-way ANOVA와 95% 신뢰도의 Scheffe's multiple range test로 사후 검증하였다. ProFile^(®)의 근관 성형 후 근단의 폭이 Hero Shaper^(®) and K3™에 비해 통계학적으로 유의하게 작았다. 본 연구의 결과에서 근단부의 과도한 확대가 variable pitch와 helical angle를 가진active file에 비해 constant pitch와 helical ange을 가짐에도 불구고 radial land를 가진passive file에서 적게 나타났다. 이 결과로 추정해 볼 때 , variable pitch와 helical angle보다는 근본적으로 radial land가 screw-in effect의 예방에 더 큰 역할을 하는 것으로 추정될 수 있다. 따라서 NiTi file의 사용 경험이 없는 초심자의 경우 근단부 폭경의 유지능력이 좋은 Profile^(®)의 사용이 추천된다. The purposes of this study were to compare the apical terminus width of simulated curved root canal prepared with three NiTi file systems used by undergraduates for evaluation the effects of flute angle and pitch or radial land on reducing screw-in effect and to determine more safe NiTi file system for inexperienced operators. Fifty inexperienced undergraduate students prepared 150 simulated curved root canals in resin blocks with three NiTi file systems: ProFile^(®), Hero Shaper^(®), K3™. The electric motor set at a speed of 300 rpm and torque of 30 in a 16 : 1 reduction handpiece was used. The simulated root canal was prepared to ISO #25 sizes with each file system. The scanned images of pre- and post-instrument canal of resin block were superimposed. To evaluate the screw-in effect of three NiTi file systems, apical terminus width of root canal was measured from superimposed images and statistical analysis was performed. There were significant differences in three NiTi file systems. ProFile^(®) had significantly smaller width than Hero Shaper^(®) and K3™ (P < 0.05) but no significant difference was observed between K3™ and Hero Shaper^(®). Under the condition of this study, active file system (Hero Shaper^(®) K3™) with variable pitch and helical angle had more screw-in effect than passive file system (ProFile^(®)) with constant pitch and helical angle. It seems that the radial lands play more important role in reducing screw-in effect.

Vehicle roll and pitch angle estimation using a cost-effective six-dimensional inertial measurement unit

Oh, Jiwon,Choi, Seibum B SAGE Publications 2013 Proceedings of the Institution of Mechanical Engin Vol.227 No.4

<P>The purpose of this paper is to estimate accurately the vehicle attitudes, i.e. the vehicle roll and pitch angles. It is assumed that a set of data obtained from a low-price six-dimensional inertial measurement unit is available. This includes the linear acceleration of the vehicle and the angular rates of all axes. In addition, the observer exploits the data from the wheel speed sensors, and the steering-wheel angle, which are already available for recent production cars. Using the above, based on the combination of the velocity kinematics and pseudointegration of the angle kinematics, a novel scheme for reference angle selection dependent on the cornering-stiffness adaptation is adopted to observe the angles. The stability of each component of the proposed observer is investigated, and a set of assessments to confirm the performance of the entire system is arranged via experiments using a real production sport utility vehicle.</P>

판형 열교환기의 피치 및 세브론각이 열에너지 성능에 미치는 영향

강병하,한상규 한국수소및신에너지학회 2004 한국수소 및 신에너지학회논문집 Vol.15 No.3

Thermal energy performance of a brazed plate heat exchanger has been evaluated experimentally. The effects of plate pitch as well as chevron angle of a plate heat exchanger on the heat transfer rate and pressure drop have been investigated in the wide range as mass flow rates in detail. This problem is of particular interest in the design of a plate heat exchanger. The results obtained indicate that both heat transfer rate and pressure drop are increased as mass flow rate is increased, as expected. It is also found that the heat transfer rate is increased with a decrease in the plate pitch while the heat transfer is decreased with a decrease in the chevron angle. Friction factor correlations are suggested based on the measured pressure drop and effectiveness of plate heat exchangers are also compared.