• Journal of Mechanical Science and Technology
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• 제16권3호
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• pp.386-394
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• 2002

The present work is aimed at investigating an unusual variation in flow and performance characteristics of a small propeller fan at low flow rates. A performance test of the fan showed dual performance characteristics, i.e., radial type characteristics at low flow rates and axial type at high flow rates. Dual performance characteristics of the fan are numerically investigated using viscous flow calculations. The Finite Volume Method is used to solve the continuity and Navier-Stokes equations in the flow domain around a fan. The performance parameters and the circumferentially averaged velocity components obtained from the calculations are compared with the experimental results. Numerical values of the performance parameters show good agreement with the measured values. The calculation simulates the steep variations of performance parameters at low flow rates and shows the difference in the flow structure between high and low flow rates. At a low flow coefficient of $\Phi$=0.2, the flow enters the fan in an axial direction and is discharged radially outward at its tip, which is much like the flow characteristics of a centrifugal fan. The centrifugal effect at low flow rates makes a significant difference in performance characteristics of the fan. As the inlet flow rate increases, flow around the fan changes into the mixed type at $\Phi$=0.24 and the axial discharge at $\Phi$=0.4.

• 대한기계학회논문집B
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• 제24권1호
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• pp.75-84
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• 2000

Performance and flow characteristics of a small forward swept propeller fan for home refrigerators are studied experimentally. An unusual discontinuity is observed in the performance curve of the fan. Mean flow fields measured with as-hole Pitot probe reveal that the flow is axial at the high flow rate and radial at the low flow rate. The flow structure changes abruptly across the discontinuity. Unsteady flow measurements with a set of hot-wire probes indicate that near the discontinuity a single-cell stall rotates at 40% speed of the fan speed, while away from the discontinuity the flow shows periodic variation corresponding to the blade passage frequency. Phase-lock averaged flow fields measured with a triple-sensor hot-wire probe show that there appears radially inward flow over the pressure side of the blade and the outward passage flow over the tip.

• 한국정밀공학회지
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• 제13권2호
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• pp.146-158
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• 1996

This paper develops a robot arm for propeller blade grinding. The grinding work requires a high stiffness robot arm to reduce deformation and vibration which are generated during machining operation. Conventional articulated robots have serial connecting links from the base to the gripper. Thus, they have very weak structure to the stiffness for grinding operation. Stewart Platform is a typical parallel robotic mechanism with very high stiffness but it has small work space and large installation space. This research proposes a new grinding robot arm by combining parallel mechanism with serial mechanism. Therefore, the robot has large range of work space as well as high stiffness. This paper introduces the automatic system for propeller grinding utilizing the robot and the design of proposed robot arm.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2007년도 제28회 춘계학술대회논문집
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• pp.217-221
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• 2007

본 연구에서는 대상체인 소형 위그선의 주날개 구조를 엔진 및 프로펠러의 기진에 의한 강제진동 해석을 수행하였다. 대상 위그선은 2행정의 왕복엔진을 날개의 좌 우에 각각 장착하여 프로펠러에 의한 추력으로 비행하며, 미는 형식(Pusher Type)의 엔진 배열을 취하고 있다. 엔진의 주요 진동 특성인 H-mode 와 X-mode 를 특정 가진 주파수로 하여 주파수 응답 해석을 수행하였고, 엔진의 횡방향 진동 모드인 L-mode를 프로펠러에 회전에 의해 진동을 수반하는 기진 추력으로 가정하여 과도응답 해석을 수행하였다.

• 대한조선학회지
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• 제4권1호
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• pp.59-65
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• 1967

Since the screw propellers were adopted as ship propulsion devices, the replacement of propeller shaft due to damage was mostly of fatigue failure due to the alternative stresses [1],[2]. To prevent such a failure, hence, it is suggested that careful attention should be paid to account of the alternative stresses on the design stage of the propeller shafts. In connection with this fact the Ship Classification Societies' Rules are regarded simply as guidance for preliminary determination of the shaft diameter. In this paper, limiting the topic to the small and medium-sized motor ships, an evaluation of the Rules formulae to a theoretical based on Soderberg's correlation [5] between the factor of safety and the resultant stresses obtained by application of the maximum shear theory is done. For this purpose eleven (11) ships built recently in Korea were taken as a species(refer to table 2. in text). In the end the following conclusions are made: (1) In general the Rules formulae give considerably larger size of the propeller shaft diameter than that derived from theoretical calculation, that is, about 7% more in AB and BV Rules, and about 20% more in LR and KR-NK Rules. (2) LR Rule gives the largest size of all, and AB Rule is mostly closed value to the theoretical. (3) The formular of the AB Rule is considered to be of the simplest in utilization and of the reasonable.

• 대한두개안면성형외과학회지
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• 제22권6호
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• pp.341-344
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• 2021

Reconstruction of submental defects is a challenge that needs to be approached carefully, since many important anatomical structures are located in this small space. Both aesthetic and functional outcomes should be considered during reconstruction. In this report, we describe a case where a superficial branch of the transverse cervical artery (STCA) perforator propeller flap was applied for coverage of the submental area. An 85-year-old woman presented with a 3-cm ovoid mass on her submental area. We covered the large submental defect with a STCA rotational flap in a 180° propeller pattern. The flap survived well without any complications at 1 year of followup. A STCA propeller flap is a useful surgical option in reconstruction for defect coverage of the submental area.

• 한국유체기계학회 논문집
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• 제17권2호
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• pp.5-11
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• 2014

Small hydro power, among other renewable energy resources, has been evaluated to have enough development value because it is a clean, renewable and abundant energy resource. In addition, small hydro power has the advantage of low cost development by using existing facilities like sewage treatment plants, water works and similar resources. But in the case of small hydro power systems, there are problems with degraded operation efficiency of turbine due to changes in flow rates. In order to overcome this, variable speed control can be achieved by using the power rectifier and permanent magnetic synchronous generator(PMSG) as a possible method to respond to the changes in flow rates. In this study, a commercial ANSYS CFD code was used to analyze the performance of 10kW class propeller hydro turbine and to also investigate flow characteristics at variable flow rates and runner vane.

• 해양환경안전학회지
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• 제30권2호
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• pp.226-232
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• 2024

우리나라의 스쿠버다이빙 중 입·출수시 선박의 스크류에 신체를 부딪쳐 사망하는 사고가 매년 반복적으로 발생하고 있다. 이에 우리나라는 관련 사고 저감과 안전관리방안 마련에 대한 필요성이 대두됨에 따라 스크류망의 설치와 관리에 관한 규정을 마련하였으나, 국내 법규상 명확한 제작 규정이 없어 설치기준이 모호하고, 점검항목이 외관·고정상태에 국한되어 있어 다이버의 스크류 사고의 안전이 담보되지 않은 상황이다. 이에 따라 본 연구는 현재 스크류망의 설치 및 점검에 대한 법적 요건을 구체화하기 위한 연구를 진행하였다. 이를 위하여 국내·외 스크류망의 현황과 안전기준과 관련된 실태와 법적 요소를 검토를 통해 문제점을 진단하였고, 이를 바탕으로 그에 대한 구체적인 개선점을 발굴하여 설치와 점검을 위한 제도개선(안)을 제시하였다. 스크류망의 설치기준은 크기와 재질에 관한 내용을 명확히 제시하였으며, 점검기준은 외관, 고정상태, 재질상태 등을 제안하였고, 이를 판단하기 위한 명확한 지표 등을 제안하였다.

• 한국항공우주학회지
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• 제44권5호
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• pp.431-438
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• 2016

본 논문은 자가발전형 쿼드콥터를 설계하고 제작한 내용을 다룬다. 본 논문에서 제안하는 자가발전형 쿼드콥터는 전자기유도원리를 이용해 설계된 두 가지 발전장치를 통해 추가 전력을 얻는다. 첫 번째 발전장치는 상용 BLDC모터와 프로펠러를 결합해 함께 회전시켜, BLDC모터를 발전기처럼 활용해 전력을 생산하는 장치이다. 두 번째 발전장치는 프로펠러의 회전축에 작은 자석들을 포함한 프레임을 결합해 함께 회전시켜 코일이 감긴 보호링에서 전력을 생산하는 장치이다. 본 발전장치들은 상용 쿼드콥터 프로펠러 하단에 장착되어 실용적인 발전을 할 수 있으리라 기대된다.

• 한국정밀공학회지
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• 제33권9호
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• pp.707-714
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• 2016

This paper describes analysis results of vibration characteristics and modal test for a small-scale quad-rotor drone. The rotor arm has a slender body with a propeller and motor at its tip. Rotor system generates excitation for an unbalanced mass. Therefore, the drone platform is involved in the possibility of resonance. For advance identification of the possibility of resonance, confirmation of eigen-mode being closest to the propeller operation range is necessary. Material properties of CFRP tubes used for the rotor arm were acquired by finding the natural frequency based on Rayleigh method. A simplified quad-rotor FE model consisting of rotor arm assembly with tip mass was built to perform numerical analysis, and a free-free boundary condition was applied to provide flight status. Modal tests for the actual platform with impact hammer instrument were performed to verify analysis results. Separation margin from hazardous eigen-mode was checked on the propeller operation range.