• Journal of Mechanical Science and Technology
• /
• 제17권7호
• /
• pp.966-977
• /
• 2003

This paper investigates how intentional mistuning of bladed disks reduces their sensitivity to unintentional random mistuning. The class of intentionally mistuned disks considered here is limited, for cost reasons, to arrangements of two types of blades (A and B, say). A two-step procedure is then described to optimize the arrangement of these blades around the disk to reduce the effects of unintentional random mistuning. First, a pure optimization effort is undertaken to obtain the pattern (s) of the A and B blades that yields small/the smallest value of the largest amplitude of response to a given excitation in the absence of unintentional random mistuning using Genetic Algorithm. Then, in the second step, a qualitative/quantitative estimate of the sensitivity for the optimized intentionally mistuned bladed disks with respect to unintentional random mistuning is performed by analyzing their amplification factor, probability density function and passband/stopband structures. Examples of application with simple bladed disk models demonstrate the significant benefits of using this class of intentionally mistuned disks.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2002년도 추계학술대회논문초록집
• /
• pp.318.2-318
• /
• 2002

Axial fans are widely used in heavy machines due to their ability to produce high flow rate fur cooling of engines. At the same time, the noise generated by these fans causes one of the most serious problems. This work is concerned with the low noise technique of discrete frequency noise. To calculate the unsteady resultant force over the fan blade in an unsymmetric engine room, Time-Marching Free-Wake Method is used. From the calculations of unsteady force on fan blades, noise signal of an engine cooling fan is calculated by using an acoustic similarity law. (omitted)

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제2권4호
• /
• pp.211-216
• /
• 2010

Recently a Wide Chord Tip (WCT) propeller has been developed and applied to a commercial ship by STX Offshore & Shipbuilding. It is reported that the WCT propeller significantly reduces pressure fluctuations and also ship's noise and vibration. On the sea trial, vibration magnitude in the accommodations at NCR was measured at 0.9mm/sec which is only 10% of international allowable magnitude of vibration (9mm/sec). In this paper, a design method for increasing performance of the marine propellers including the WCT propeller is suggested. It is described to maximize the performance of the propeller by adjusting expanded areas of the propeller blade. Results show that efficiency can be increased up to over 2% through the suggested design method.

• 설비공학논문집
• /
• 제12권7호
• /
• pp.674-679
• /
• 2000

The Sirocco fan performance and its three-dimensional flow characteristics were numerically predicted by STAR-CD software. Turbulent flow computations were performed using approximately 500,000 mesh points, and the performance results of two computational methods, transient analysis and quasi-static analysis were compared with experimental data. At present, our attention was focused on localizing the three-dimensional flow characteristics of the Sirocco fin, especially the structure of the secondary flow in the scroll and the through-flow characteristics of the Sirocco fan blades. Also, for an optimization, the scroll passage was tilted with 10 degrees to change the flow characteristics and improve the performance of the Sirocco fan.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2009년도 추계학술대회 논문집
• /
• pp.427-430
• /
• 2009

풍력 터빈 블레이드용 익형의 경우 운용 조건에서 높은 양항비를 가지도록 설계되나 풍속, 풍향의 변동에 의해 운용조건에 변화가 발생할 경우 성능의 저하가 발생할 수 있다. 따라서 운용조건의 변동이 발생하더라도 공력 성능이 크게 변하지 않는 익형이 요구된다. 본 연구에서는 이러한 운용조건의 불확실성을 고려하여 풍력 터빈 블레이드용 익형의 신뢰성 기반 강건 최적 설계를 수행하였다. 익형 설계를 위해서 여러 익형 형상 변수들을 고려할 수 있는 익형 모델링 함수를 정의하였고 기저형상으로는 NREL에서 개발한 S809 익형을 사용하였다.

• Water Engineering Research
• /
• 제4권1호
• /
• pp.1-17
• /
• 2003

A mathematical model was developed to simulate the performance of a prototype wind-powered reverse osmosis desalination system. The model consists of two sub-models operated in a series. The first sub-model is the wind-energy conversion sub-model, which has wind energy and feed water as its input and pressurized feed water as its output. The second sub-model is a reverse osmosis (RO) process sub-model, with pressurized feed water as its input and the flow and salinity of the product water or permeate as its output. Model coefficients were determined based on field experiments of a prototype wind powered RO desalination system of the University of Hawaii, from June to December 2001. The mathematical model developed by this study predicts the performance of wind-powered RO desalination systems under different design conditions. The system optimization is achieved using a linear programming approach. Based on the results of system optimization, a design guide is prepared, which can be used by both manufacturer and end-user of the wind-driven reverse osmosis system.

• 한국항공우주학회지
• /
• 제36권8호
• /
• pp.797-806
• /
• 2008

본 연구에서는 선형 캐스케이드 실험장치의 유로를 캐스케이드 피치의 두배 넓이로 설정하고 두 개의 블레이드만을 설치하였다. 따라서 동일한 실험장치에서 다수개의 블레이드를 설치하는 경우에 비하여 큰 블레이드에서 실험이 가능하도록 하였다. 아울러 두 개의 블레이드 설치에 따른 주기조건의 어려움을 해소하기 위하여 실험장치 내의 작동유체의 배출이나 꼬리판의 조정을 하지 않아도 주기조건이 되도록 하는 실험장치의 벽면을 설계하였다. 이를 위하여 주기조건에서 얻어진 블레이드 표면에서의 마하수와 동일한 결과가 얻어지도록 목적함수를 설정하였으며, 설계변수로는 벽면의 형상변경과 관련이 있는 12개의 변수를 사용하였다. 벽면의 설계는 기울기 기반의 최적화법을 사용하였으며, 내부유동장의 계산은 상용코드인 CFX-11을 사용하였다. 두 결과의 비교에서 벽면의 조정만으로도 동일한 유동특성이 얻어질 수 있음을 확인하였다.

• 대한기계학회논문집A
• /
• 제41권3호
• /
• pp.165-172
• /
• 2017

본 논문에서는 가정용 냉장고의 내부 냉기순환용 원심팬의 고성능/저소음 최적설계를 수행하였다. 최적설계를 위해 여러 독립변수들이 어떠한 종속변수에 영향을 줄 때 용이하게 적용할 수 있는 반응표면법을 사용하였으며, 블레이드의 입구각, 출구각, 내경을 독립변수로 선정하였다. 먼저 이를 통해 팬 블레이드의 유량을 최대화하였으며, 3-D 프린터를 이용해 샘플을 제작하였고, 만들어진 팬의 P-Q곡선을 측정하여 개선된 팬이 유량의 증가를 보임을 확인하였다. 또한 기존 팬과 동일한 유량을 가지도록 새로운 팬의 회전속도를 저감시킬 경우, 1.7 dBA의 소음 저감 효과가 있음을 확인할 수 있었다.

• 한국유체기계학회 논문집
• /
• 제7권3호
• /
• pp.32-38
• /
• 2004

Shape of a multi-blades centrifugal fan is optimized by response surface method based on three-dimensional Navier-Stokes analysis. For numerical analysis, Reynolds-averaged Navier-Stokes equations with standard $k-{epsilon}$ turbulence model are transformed into non-orthogonal curvilinear coordinate system, and are discretized with finite volume approximations. Due to the large number of blades in this centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models for economic calculations. Optimizations with and without constraints are carried out. Design variables, location of cur off, radius of cut off, expansion angle of scroll and width of impeller were selected to optimize the shapes of scroll and blades. Data points for response evaluations were selected by D-optimal design, and linear programming method was used for the optimization on the response surface. As a main result of the optimization, the efficiency was successfully improved. The correlation of efficiency with relative size of inactive zone at the exit of impeller is discussed as well as with average momentum fluxes in the scroll.

• 유체기계공업학회:학술대회논문집
• /
• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
• /
• pp.385-390
• /
• 2003

Shape of a multi-blades centrifugal fan is optimized by response surface method based on three-dimensional Navier-Stokes analysis. For numerical analysis, Reynolds-averaged Wavier-Stokes equations with standard $k-{\varepsilon}$ turbulence model are transformed into non-orthogonal curvilinear coordinate system, and are discretized with finite volume approximations. Due to the large number of blades in this centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models for economic calculations. Optimizations with and without constraints are carried out. Design variables, location of cur off, radius of cut off, expansion angle of scroll and width of impeller were selected to optimize the shapes of scroll and blades. Data points for response evaluations were selected by D-optimal design, and linear programming method was used for the optimization on the response surface. As a main result of the optimization, the efficiency was successfully improved. The correlation of efficiency with relative size of inactive zone at the exit of impeller is discussed as well as with average momentum fluxes in the scroll.