• 대한기계학회논문집B
• /
• 제39권5호
• /
• pp.435-441
• /
• 2015

본 연구에서는 원심압축기 임펠러와 디퓨져 블레이드 형상을 반응표면법과 다목적 유전알고리즘 기법을 사용하여 최적설계 연구를 수행하였다. 임펠러와 디퓨져의 블레이드 선단과 후단의 각도와 두께를 3 구간으로 나누어 설계변수로 적용하였으며 수치해석은 상용코드인 ANSYS CFX 를 사용하였다. 실험계획법 중 많이 사용되는 중심합성계획을 이용하여 총 45 개의 설계점에 대한 값을 계산하였다. 계산된 결과를 바탕으로 반응표면을 생성하였으며 반응표면은 최적형상의 임펠러와 디퓨져를 선정하는데 이용하였다. 최적설계의 전 과정은 ANSYS DX 를 사용하였으며, 최적화의 결과로 원심압축기의 주요 성능변수인 등엔트로피 효율과 압력회복계수가 각각 0.3%, 5% 향상된 임펠러와 디퓨져 블레이드 형상을 제시하였다.

• 한국추진공학회지
• /
• 제21권1호
• /
• pp.26-35
• /
• 2017

원심압축기 운전 중에 발생하는 고주기 피로균열이나 공진 등은 임펠러 파손의 주된 원인이다. 이러한 파손을 회피하기 위해 공진영역 운전에서도 견딜 수 있는 충분한 강도의 임펠러를 설계하거나, 공진이 발생하지 않도록 임펠러를 튜닝 한다. 이러한 회피설계는 임펠러 내부유동 및 성능특성 변화를 야기하게 된다. 본 연구에서는 밀폐형 임펠러에 대해 블레이드 두께를 증가시킨 모델과 스켈럽을 적용한 모델에 대한 유동 및 성능특성을 파악하기 위해 전산해석을 수행하였다. 전산해석 결과, 블레이드 두께 증가 모델 경우는 기본모델 대비 압력계수가 0.5% 감소하였으며, 전효율은 0.1% 감소하였다. 스켈럽 적용모델은 압력계수가 0.4% 증가하였으며, 전효율은 1.6% 감소하였다.

• 한국의류산업학회지
• /
• 제20권6호
• /
• pp.713-721
• /
• 2018

This study aimed to develop a draping manual for the basic bodice to be available in colleges and industries. For this, draping methods mentioned in six different textbooks were comparatively analyzed. As for the research method, draping methods were compared by using training textbook, and basic bodices designed with muslin were assessed using the 5-point Likert scale. First, the draping methods of basic bodices were comparatively analyzed. The main baselines were set as the center front line, the center back line, the bust line, and the shoulder blade line. The position of dart was suggested based on the princess line, in both the front and the back. The value of dart was classified as a fixed size with any associated excess. The length of dart was set based on the bust point and shoulder blade point or a fixed size. The amount of ease was randomly set based on the fixed size, bust circumference, waist circumference, interscye length, armholes and shoulder lines, or the worker's intuition. Second, according to the appearance evaluation of the patterns, the following patterns obtained the highest scores: A pattern 2.5cm away from the B.P point of the waist dart and shoulder dart in the frontal appearance, a pattern of 0.6~0.7cm ease for the front armhole, a pattern with an ease of 1.2cm in the bust and 0.6cm in the waist. As for back appearance, the pattern in which the point of waist dart is 2~3cm from the bust line received the highest score.

• 한국해양공학회지
• /
• 제30권2호
• /
• pp.125-133
• /
• 2016

In this paper, we propose a vertical axis water turbine with dual blades. A parametric study was conducted using numerical analyses. First, a two-dimensional finite-volume analysis with a commercial code was used to find the pitch angle of the main blade under different tip speed ratio conditions. Second, we developed a potential-based panel method to find the best configuration of the inner blades. Experimental tests were conducted at the circulating water channel of Chungnam National University. Various configurations of the dual blades were considered, and their performances were comparatively investigated. The results showed that the turbine with movable dual blades produces a constant torque and tip speed ratio at various flow rates.

• Wind and Structures
• /
• 제18권2호
• /
• pp.103-116
• /
• 2014

Aeroelasticity is the main source of instability in structures which are subjected to aerodynamic forces. One of the major reasons of instability is the coupling of bending and torsional vibration of the flexible bodies, which is known as flutter. The presented investigation aims to study the aeroelastic stability of composite blades of wind turbine. Geometry, layup, and loading of the turbine blades made of laminated composites were calculated and evaluated. To study the flutter phenomenon of the blades, two numerical and analytical methods were selected. The finite element method (FEM), and JAR-23 standard were used to perform the numerical studies. In the analytical method, two degree freedom flutter and Lagrange's equations were employed to study the flutter phenomena analytically and estimate the flutter speed.

• 대한기계학회논문집B
• /
• 제30권7호
• /
• pp.603-611
• /
• 2006

This paper presents the response surface optimization method using three-dimensional Wavier-Stokes analysis to optimize the blade shape of an axial flow fan. Reynolds-averaged Wavier-Stokes equations with $k-{\epsilon}$ turbulence model are discretized with finite volume approximations using the unstructured grid. Regression analysis is used for generating response surface, and it is validated by ANOVA and t-statistics. Four geometric variables, i.e., sweep and lean angles at mean and tip respectively were employed to improve the efficiency. The computational results are compared with experimental data and the comparisons show generally good agreements. As a main result of the optimization, the total efficiency was successfully improved. Also, detailed effects of sweep and lean on the axial flow fan are discussed.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2009년 추계학술대회논문집
• /
• pp.19-26
• /
• 2009

The objective of this study is to investigate aerodynamic characteristics of a Horizontal-axis wind turbines(HAWT), using CFD method with a commercial code STAR-CCM+ version 3.06. To verify the reliability of the computations, the CFD results are compared with the experimental ones of the National Renewable Energy Laboratory(NREL) Phase Ⅵ HAWT. For the comparison and examination of aerodynamic characteristics, the existent shape with a predesigned twist angle was replaced by the one with one-dimensional linear twist angle. In this study, the pressure contour and stream line around the blade were analyzed as main focus. Through this study the more efficient shape of airfoil is suggested with consideration of manufacturing cost.

• International Journal of Fluid Machinery and Systems
• /
• 제8권3호
• /
• pp.209-219
• /
• 2015

A robust multi-fidelity optimization methodology has been developed, focusing on efficiently handling industrial runner design of hydraulic Francis turbines. The computational task is split between low- and high-fidelity phases in order to properly balance the CFD cost and required accuracy in different design stages. In the low-fidelity phase, a physics-based surrogate optimization loop manages a large number of iterative optimization evaluations. Two derivative-free optimization methods use an inviscid flow solver as a physics-based surrogate to obtain the main characteristics of a good design in a relatively fast iterative process. The case study of a runner design for a low-head Francis turbine indicates advantages of integrating two derivative-free optimization algorithms with different local- and global search capabilities.

• 한국항공운항학회지
• /
• 제14권1호
• /
• pp.9-14
• /
• 2006

Averaged heat transfer coefficients in the trailing edge model of a turbine blade with double impingements were measured using transient liquid crystals technique and conventional copper plate-thermocouple technique. The detailed distributions of heat transfer coefficients by transient liquid crystals technique were also presented. Results showed that increased heat transfer coefficient due to the inpingements and the averaged heat transfer coefficients increased as Reynolds number increased. Results by transient liquid crystals technique showed that the heat transfer coefficient strongly depended on the main stream temperature used in heat transfer coefficient calculation. The averaged heat transfer coefficients measured by different methods showed similar trend as Reynolds number changed, but the value varied up to 40% depending on the measurement technique.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.365-368
• /
• 2003

전북 부안군에 설치된 30kW급 Dual-rotor 풍력발전기의 Main rotor blade를 대상으로 공기역학적 모델링을 수행한 후 각종 바람 상황과 풍속에 따라 변화하는 RPM 상황을 고려하여 전산모의 실험을 수행하였다. 또한 출력성능을 향상시키기 위하여 최대 출력을 계산하고 이를 추종하도록 하는 직접 출력 제어 알고리즘을 제안하였다.