Heat Transfer Enhancement by Shape Optimization of Dimpled Channel

Abdus Samad(압두스사마드),Kwang-Yong Kim(김광용) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

Heat transfer enhancement problem of turbine blade cooling passage has been solved numerically in this paper. Basic fluid dynamics equations like mass, momentum and energy equations are solved to enhance turbulent heat transfer. Dimpled channel heat transfer problem is formulated considering three dimensionless design variables. The objective functions are pressure drop and Nusselt number. Dimple on the wall of flow passage increases turbulence and pressure drop. Combining these two objectives, the shape of the dimple channel has been optimized. D-optimal design generated design points are used to design the channels and flow field is solved by RANS analysis. The Nusselt number and pressure drop objective functions are combined using weighting factor method to make final single objective function. Surrogate models like response surface, Kriging, radial basis neural network and weighted average models are used for optimization. Evaluation of surrogate models as well as optimal design of the dimpled channel has been presented in this paper.

Shape Optimization of Compressor Blade Using Surrogate Models

Abdus Samad(압두스사마드),Kwang-Yong Kim(김광용) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11

Shape optimization of transonic axial compressor rotor has been performed using RANS analysis and surrogate models. Variables from lean, skew, sweep of the blade and number of blades on hub have been considered to enhance the adiabatic efficiency of the compressor. D-Optimal design generated design points are used for sampling and at these data points, the flow field is solved using computer code. The weighted average surrogate model, which is derived from the three basic surrogate models like response surface, Kriging and radial basis neural network is used to predict the optimal points of the design variables. Due to optimization, efficiency is enhanced and it is concluded that numerical simulation with statistical optimization methods can be used to design a better preformed turbomachinery.

Effects of Surface Roughness on Turbomachinery Blade Performance

Abdus Samad(사마드압두스),Kwang-Yong Kim(김광용) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-

Deterioration of surface of turbomachinery blades occur in course of time and hence reduce the performance of the machine. In this paper, transonic axial compressor blade surface roughness is studied considering a reference blade and a shape distorted (optimized) blade. Optimal blade is designed considering sweep and lean. Roughened blade by changing Reynolds roughness number and hydraulically smooth blade is numerically formulated and is compared the different parameters like adiabatic efficiency, total temperature ratio, total pressure ratio and Mach number. Baldwin-Lomax turbulence model is used for flow field analysis and Cebeci-Smith roughness model is formulated for roughness modeling. It is found the performance in terms of adiabatic efficiency, total temperature ratio, total pressure ratio is decreased and Mach number is increased. Performance deterioration is more severe in case of distorted blade as compared to reference blade.

단면 형상과 중첩선을 고려한 축류 송풍기 날개의 최적설계

이기상(Ki-Sang Lee),김광용(Kwang-Yong Kim),압두스사마드(Abdus Samad) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10

This work presents a numerical optimization procedure for a low-speed axial flow fan blade with polynomial response surface approximation model. Reynolds-averaged Navier-Stokes equations with shear stress turbulence (SST) model are discretized by finite volume approximations and solved on hexahedral grids for flow analyses. The airfoil shape as well as stacking line is modified to enhance blade total efficiency, i.e., the objective function. The design variables of blade lean, maximum thickness and location of maximum thickness are selected, and a design of experiments technique produces design points where flow analyses are performed to obtain values of the objective function. A gradient-based search algorithm is used to find the optimal design in the design space from the constructed response surface model for the objective function. As a main result, the efficiency is increased effectively by the present optimization procedure. And, it is also shown that the modification of blade lean is more effective to improve the efficiency rather than modifying blade profile.

신경회로망기법을 이용한 축류 송풍기 날개의 최적설계

이기상(Ki-Sang Lee),김광용(Kwang-Yong Kim),압두스사마드(Abdus Samad) 한국유체기계학회 2007 유체기계 연구개발 발표회 논문집 Vol.- No.-

Radial basis neural network (RBNN) has been used in present work to find numerically optimum design of a low speed axial flow fan blade to enhance its efficiency. Reynolds-average Navier-Stokes equations with shear stress turbulence (SST) model for turbulence closure are discretized by finite volume approximations and solved on hexahedral grids. The design variables from airfoil maximum camber, maximum camber location, leading edge radius and trailing edge radius are selected, and total efficiency is considered as objective function which is to be maximized. Thirty designs for four geometric variables are evaluated to get the objective function values of each design. These values are used to train the neural network. Optimum design is found by searching the network through a gradient based search algorithm. By the optimization, the efficiency is increased by 1%.

NSGA-Ⅱ를 통한 송풍기 블레이드의 다중목적함수 최적화

이기상(Ki-Sang Lee),김광용(Kwang-Yong Kim),압두스사마드(Abdus Samad) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5

This work presents numerical optimization for design of a blade stacking line of a low speed axial flow fan with a fast and elitist Non-Dominated Sorting of Genetic Algorithm (NSGA-Ⅱ) of multi-objective optimization using three-dimensional Navier-Stokes analysis. Reynolds-averaged Navier-Stokes (RANS) equations with k-ε turbulence model are discretized with finite volume approximations and solved on unstructured grids. Regression analysis is performed to get second order polynomial response which is used to generate Pareto optimal front with help of NSGA-Ⅱ and local search strategy with weighted sum approach to refine the result obtained by NSGA-Ⅱ to get better Pareto optimal front. Four geometric variables related to spanwise distributions of sweep and lean of blade stacking line are chosen as design variables to find higher performed fan blade. The performance is measured in terms of the objectives; total efficiency, total pressure and torque. Hence the motive of the optimization is to enhance total efficiency and total pressure and to reduce torque.

가중평균대리모델을 사용한 천음속 압축기 블레이드 최적화

압두스 사마드(Abdus Samad),김광용(Kwang-Yong Kim),최재호(Jae-Ho Choi) 대한기계학회 2008 大韓機械學會論文集B Vol.32 No.4

The main purpose of the present study is to perform shape optimizations of transonic compressor blade in order to enhance its performance. In this study, the Latin hypercube sampling of design of experiments and the weighted average surrogate model with the help of a gradient based optimization algorithm are used within design space by the lower and upper limits of each design variable and for finding optimum designs, respectively. 3-D Reynolds-averaged Navier-Stokes solver is used to evaluate the objective functions of adiabatic efficiency and pressure ratio. Six variables from lean and airfoil thickness profile are selected as design variables. The results show that the adiabatic efficiency is nhanced by 1.43% by efficiency optimization while the pressure ratio is increased very small, and pressure ratio is increased by 0.24% by pressure ratio optimization.

Performance of Surrogate Models in Optimizing Heat Transfer Augmentation Devices

Abdus Samad(압두스 사마드),Kwang-Yong Kim(김광용) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-

A three dimensional channel with oblique rib attached on both walls has been optimized to enhance turbulent heat transfer using multiple surrogate models. Objective functions values are evaluated at design points by Reynolds-averaged Navier-Stokes analysis, and surrogates models are constructed for optimization. It is found that the turbulent heat transfer rates increased reasonably by shape optimization and the multiple surrogate methods performed well since these models protect the designer from using any individual basic surrogate poor in prediction. The present approach can help to address the multi-objective designs on a rational basis with quantifiable cost-benefit analysis of system design.

가중평균 대리모델을 이용한 엇갈린 딤플유로의 수치최적설계

이기돈(Ki-Don Lee),압두스 사마드(Abdus Samad),김광용(Kwang-Yong Kim) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.10

This study presents a numerical procedure to optimize the shape of dimple surface to enhance turbulent heat transfer in a rectangular channel. The PBA method is used as an optimization technique with Reynoldsaveraged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport (SST) turbulence model. The dimple depth-to-dimple print diameter ratio, channel height-to-dimple print diameter ratio, and dimple print diameter-to-pitch ratio are chosen as design variables. The objective function is defined as a linear combination of heat transfer related term and friction loss related term with a weighting factor. Full factorial method is used to determine the training points as a mean of design of experiment. The optimum shape shows remarkable performance in comparison with a reference shape.

딤플 유로의 열전달 증진을 위한 최적화모델 비교

신동윤(Dong-Yoon Shin),김광용(Kwang-Yong Kim),압두스 사마드(Abdus Samad) 대한기계학회 2007 대한기계학회 춘추학술대회 Vol.2007 No.5

Shape optimization of an internal cooling passage with staggered dimples on single surface is performed and performances of surrogates are evaluated in this paper. Optimizations are performed so that turbulent heat transfer can be enhanced compromising with pressure loss due to friction. The three-dimensional governing differential equations have been solved to find the overall Nusselt number and friction factor which are related to the objective functions of this problem. Three design variables were selected among the dimensionless geometric variables. Basic surrogate models such as second order polynomial response surface approximation (RSA), Kriging meta-modeling technique, radial basis neural network (RBNN), and derived press based averaged (PBA) surrogate model are constructed. The optimal points are searched from the above constructed surrogates by sequential quadratic programming (SQP). It is shown that use of multiple surrogates can increase the robustness in prediction of better design with minimum computational cost.