Man-Woong Heo

Parametric Study and Optimization of Staggered Inclined Impinging Jets on a Concave Surface for Heat Transfer Augmentation

The characteristics of the fluid flow and heat transfer of staggered inclined impinging jets on a concave surface have been investigated numerically using three-dimensional Reynolds-averaged Navier-Stokes analysis using the shear stress transport turbulence model. Shape optimization of the impinging jet has been performed with a weighted-average surrogate model. A constant temperature condition has been applied to the concave surface. The inclination angle of the staggered jet nozzles and the distance between the jet nozzles are chosen as the design variables, and their effects on the heat transfer performance have been evaluated. It is found that the overall heat transfer increases with the pitch of vertical jet nozzles, and the staggered inclination of jet nozzles improves the heat transfer on the concave surface. For the optimization of the impinging jet, the area-averaged Nusselt number on the concave surface is set as the objective function. Latin hypercube sampling is used to determine the training points as a design of experiment, and the surrogate model is constructed using the objective function values at the training points. Sequential quadratic programming is used to search for the optimal point from the constructed surrogate model. Through the optimization, the heat transfer performance has been improved by nearly 60% compared to the reference design.

Aerodynamic and aeroacoustic optimization for design of a forward-curved blades centrifugal fan

This paper presents a multidisciplinary optimization procedure for enhancing the aerodynamic and aeroacoustic performance of a forward-curved blade centrifugal fan for residential ventilation. Flow analysis in a forward-curved blade centrifugal fan was conducted by solving three-dimensional steady and unsteady Reynolds-averaged Navier–Stokes equations using the shear stress transport turbulence model. On the basis of the aerodynamic sources extracted from the unsteady flow, aeroacoustic analysis was implemented in a finite/infinite element method by solving the variational formulation of Lighthill’s analogy. Experiments were performed to obtain aerodynamic and aeroacoustic measurements for validation of numerical results. The single- and multi-objective optimizations were performed sequentially. The single-objective optimization was carried out to improve the efficiency of the fan using a radial basis neural network surrogate model with four design variables defining the scroll cut-off angle, scroll diffuser expansion angle, diameter ratio of the impeller, and blade exit angle. Multi-objective optimization based on the single-objective optimization result was carried out to simultaneously improve the efficiency and reduce the sound pressure through a hybrid multi-objective evolutionary algorithm coupled with a response surface approximation surrogate model with two design variables defining the scroll cut-off radius and distance. These objective functions were accessed numerically through three-dimensional aerodynamic and aeroacoustic analyses at the design points sampled by Latin hypercube sampling in the design space. Arbitrary selected optimum designs in the Pareto-optimal solutions yielded significant increases in efficiency and decreases in the sound pressure level compared to the reference design.

Design Optimization of a Centrifugal Fan with Splitter Blades

Abstract Multi-objective optimization of a centrifugal fan with additionally installed splitter blades was performed to simultaneously maximize the efficiency and pressure rise using three-dimensional Reynolds-averaged Navier-Stokes equations and hybrid multi-objective evolutionary algorithm. Two design variables defining the location of splitter, and the height ratio between inlet and outlet of impeller were selected for the optimization. In addition, the aerodynamic characteristics of the centrifugal fan were investigated with the variation of design variables in the design space. Latin hypercube sampling was used to select the training points, and response surface approximation models were constructed as surrogate models of the objective functions. With the optimization, both the efficiency and pressure rise of the centrifugal fan with splitter blades were improved considerably compared to the reference model.

Effect of Intake Vortex Occurrence on the Performance of an Axial Hydraulic Turbine in Sihwa-Lake Tidal Power Plant, Korea

A numerical study to investigate the effect of intake vortex occurrence on the performance of an axial hydraulic turbine for generating tidal power energy in Sihwa-lake tidal power plant, Korea, is performed. Numerical analysis of the flow through an sxial hydraulic turbine is carried out by solving three-dimensional Reynolds-averaged Navier-Stokes dquations with the shear stress transport turbulence model. In the real turbine operation, the vortex flows are occurred in both the side corners around the intake of an axial hydraulic turbine due to the interaction between the inflow angle of water and intake structure. To analyze these vortex phenomena and to evaluate their impacts on the turbine performance, the internal flow fields of the axial hydraulic turbines with the different inflow angles are compared with their performances. As the results of numerical analysis, the vortex flows do not directly affect the turbine performance.

Parametric performance evaluation of a hydraulic centrifugal pump

Parametric study of a hydraulic centrifugal pump with backward curved blades has been performed numerically using three-dimensional Reynolds-averaged Navier-Stokes equations. The shear stress transport turbulence model was used for analysis of turbulence. The finite volume method and an unstructured grid system were used for the numerical solution. The optimal grid system in the computational domain was selected through a grid dependency test. Tested parameters were related to the geometry of the impeller and volute: seven variables defining the hub and shroud contours and the blades angle of impeller, and two variables defining the inlet width and expansion angle of volute. The effects of these parameters on the hydrodynamic performance of the centrifugal pump have been investigated. It was found that the centrifugal water pump with the twisted blades has the enhancing efficiency compared to the straight blades pump.

Aerodynamic Analysis of Automotive HVAC Duct for Enhancement of Cooling/Heating Performance

ABSTRACT:In the present work, numerical analyses of air flow in HVAC duct have been carried out for enhancement of cooling/heating performance. For the analyses, three-dimensional Reynolds-averaged Navier-Stokes equations have been solved with the shear stress transport turbulence model. The numerical results were validated in comparison with the experimental data. Based on the numerical results, the HVAC duct was designed to reduce the pressure loss. The modified duct geometry shows largely reduced pressure drop in comparison with the reference geometry. And, through modified duct shape, the performance of air conditioning has been enhan-ced.Keywords:HVAC duct(공기조화 덕트), RANS analysis(RANS 해석), Vortex(와류), CFD(전산유체역학), Pressure drop(압력손실) †Corresponding author Tel.: +82-32-860-7317; fax: +82-32-868-1716 E-mail address: jjw529@naver.com 기 호 설 명 A ：덕트 단면D ：덕트 입구 수력직경 [m]LC ：좌측 중간 덕트LH ：좌측 덕트RC ：우측 중간 덕트RH ：우측 덕트LH ：좌측 덕트X, Y, Z：좌표 축 1. 서 론 최근 자동차산업에서 차량의 상품성은 주행성능과 더불어 인간의 감성을 위한 쾌적성에 의해서도 평가되고 있는 상황이다. 따라서 최근 생산되는 자동차들에서는 자동차 실내 공기조화를 위한 HVAC (Heating Ventilating Air Conditioning) 시스템의

Aerodynamic and Aeroacoustic Analyses of a Regenerative Blower

This paper presents a parametric study to investigate the aerodynamic and aeroacoustic characteristics of a side channel regenerative blower. Flow analysis in the side channel blower was carried out by solving three-dimensional steady and unsteady Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence closure. Aeroacoustic analysis was conducted by solving the variational formulation of Lighthill’s analogy on the basis of the aerodynamic sources extracted from the unsteady flow analysis. The height and width of the blade and the angle between inlet and outlet ports were selected as three geometric parameters, and their effects on the aerodynamic and aeroacoustic performances of the blower have been investigated. The results showed that the aerodynamic and aeroacoustic performances were enhanced by decreasing height and width of blade. It was found that angle between inlet and outlet ports significantly influences the aerodynamic and aeroacoustic performances of the blower due to the stripper leakage flow.Copyright

AERODYNAMIC INVESTIGATION OF A SINGLE-STAGE AXIAL COMPRESSOR WITH A CASING GROOVE AND TIP INJECTION USING FLUID-STRUCTURE INTERACTION ANALYSIS

In this paper, a fluid-structure interaction (FSI) analysis was performed for a single-stage axial compressor with casing groove and tip injection using three-dimensional ReynoldsAveraged Navier-Stokes equations. The k-e turbulence model and hexahedral grids system were used in the analysis. ANSYS solid 186 elements type was used to analyze the solid characteristic. In order to achieve robust stability of the transonic axial compressor, a casing groove was installed with tip injection on rotor tip region. FSI analysis was carried out to predict the deformation of the blades, and the results were compared to those of non-FSI analysis. Validation of the numerical results performed in comparison with experimental data, showed good agreements with experimental data for the adiabatic efficiency and total pressure ratio. It was found that deformation of blades affects the aerodynamic performance of the compressor to some extent. Stability of the axial compressor was enhanced by installing the casing groove with tip injection.

Parametric Study on Aerodynamic Performance of a Centrifugal Fan With Additionally Installed Splitter Blades

Aerodynamic Performance of a centrifugal fan with additionally installed splitter blades in the impeller has been investigated numerically using three-dimensional Reynolds-averaged Navier-Stokes equations. The shear stress transport turbulence model and hexahedral grids system were used to analyze the flow in the centrifugal fan. From results of the flow analysis, considerable energy loss by flow separation was observed in the blade passages. Splitter blades were applied between the main blades to reduce the loss and enhance fan performance. The chord length ratio of splitter to main blade, the angle between splitter and main blade, and the height ratio of outlet and inlet of impeller were selected as the geometric parameters, and their effects on the aerodynamic performance of the centrifugal fan have been investigated. The performance of the centrifugal fan with added splitter blades was improved conspicuously compared to the centrifugal fan without splitter blades. It was found that the installation of splitter blades in the impeller is effective to improve the aerodynamic performance of a centrifugal fan by reducing the flow separation generated between main blades in the impeller.Copyright