Three-dimensional Shape Design Research Articles

폐열회수 발전용 초임계 ORC 터빈 개발

In this study, a turbine applicable to a supercritical ORC power generation system with higher power generation efficiency than the typical ORC power generation system was developed. This paper describes the turbine design, fabrication and performance tests for developing a 100kW class power generation turbine. R-1234ze(E) was selected as the working fluid in consideration of Global Warming Potential. The overall turbine expansion ratio was 9, and the turbine consisted of a two-stage centrifugal turbine. The magnetic bearings were installed, and the turbine and generator were assembled into a single casing. The rotation speed was selected as 36,000rpm through the specific speed and the specific diameter analysis. Based on these analysis results, one-dimensional design, three-dimensional shape design, and three-dimensional performance analysis were conducted. Turbine components were fabricated based on CAD drawings and three-dimensional modeling. The assembled turbine was installed in a supercritical ORC power generation system. The cooling tubes were additionally installed to maintain a stable temperature inside the turbine. Through the performance test, it was confirmed that the developed turbine generated electric power of 100kW. In this paper, important matters to be considered when developing turbines for supercritical ORC power generation system were specifically mentioned.

An inverse shape design problem in determining the optimal snowflake-shaped fins

A three-dimensional shape design problem is considered to determine the optimal snowflake-shaped fins (SSF), based on the minimization of maximum domain temperature of fin. The Levenberg-Marquardt method (LMM) and software package CFD-ACE+ are used as the design tools. The SSF can be obtained by modifying the helm-shaped fins (HSF), the fine surfaces of HSF can be increased by splitting central part of the extended bodies from the center line outward and perforations can therefore be formed. The validity of CFD-ACE+ is first performed to verify the accuracy of the numerical solutions, and two categories of test cases are examined in the present study. The estimated optimal SSF are then compared with the HSF. Results indicate that the optimal SSF can achieve lower maximum fin temperature than HSF since (i) for single IHS problems, the decrease percentages of dimensionless maximum thermal resistance (DMTR) of SSF vary from 0.182% to 11.553% for various fin heights when compared with the values of HSF, and (ii) For multiple IHS problems, the decrease percentages of DMTR can be as large as 14.358% and 17.631% for two and four IHSs, respectively, as convective heat transfer coefficient a = 0.1.

An inverse design method with aerodynamic design optimization for wing glove with hybrid laminar flow control

The design of the hybrid laminar flow control (HLFC) system involves the comprehensive design of the suction control and the profile, and it has become an urgent problem for a three-dimensional shape design with the consideration of HLFC technology, especially in condition of the high Reynolds number with the large sweep angle. In order to deal with this issue, this paper conducts an inverse design method combining a design optimization oriented by pressure distribution. This methodology prescribes a target pressure distribution and then uses the optimization method to pursue the corresponding shape that matches the target pressure distribution. The optimization framework is mainly based on the particle swarm optimization algorithm and the Kriging surrogate model. The studied model is a wing glove, and the results show that the desired robust wing glove that meets the engineering requirements can be efficiently obtained. The optimized wing glove has a long enough laminar zone with the help of suction control, and it shows good robustness with the variation of sideslip angles and angles of attack.

A three-dimensional shape design problem in determining the boundary geometry to yield isotherms

A three-dimensional shape design problem is studied in this work. The objective is to estimate the optimal boundary geometry of a conductive body for producing boundary isotherms and the technology can be utilized in designing the shape of heating probe for thermostatic bath. The combination of CFD-ACE + package and Levenberg–Marquardt method (LMM) are used to build the optimization algorithm for the present shape design problem. The general as well as axially symmetric type of boundary geometries are both considered in this work and the validity of the design algorithm is verified through numerical experiments. Results show that the desired boundary temperatures can be assigned arbitrarily and the corresponding optimal boundary surfaces can be estimated with reasonable iteration numbers when constraint of domain volume is not considered. When the constraint of domain volume is considered, the optimal boundary surfaces can be obtained with very few iteration numbers.

A three-dimensional shape design problem to determine the filler geometry for optimal system thermal conductivity

A three-dimensional shape design problem is considered in this work, based on the desired thermal conductivity ratio and filler volume, to determine the optimal shape of filler between two conductive bodies in a three-dimensional composite material. The Levenberg–Marquardt method (LMM), commercial software CFD-ACE + and B-spline surface generation technique are adopted in the present shape design algorithm. The design analysis is examined using the numerical experiments and different filler volume and thermal conductivity are considered in the numerical test cases to justify the validity of this study. The estimated results obtained with optimal filler are then compared with those using original filler shapes and it is found that (i) the optimal filler shapes are found as a family of “hourglass” shape with a smooth nozzle-diffuser shape in the central parts of filler and (ii) the radiuses of the top and bottom surfaces of filler play the most significant role on the effective thermal conductivity. Besides, by fixing the filler thermal conductivity, the effective thermal conductivities using optimal fillers can be increased from 15.3% to 47.6% depending on different filler volumes and by fixing the filler volume, the effective thermal conductivities using optimal fillers can be increased from 5.5% to 57.4% depending on different filler conductivities.

A shape design problem in determining the interfacial surface of two bodies based on the desired system heat flux

A shape design problem (or inverse geometry problem) in determining the geometry of interfacial surface between two conductive bodies in a three-dimensional multiple region domains, based on the desired system heat flux and domain volume, is examined in this study. The design algorithm utilized the Levenberg–Marquardt method (LMM), B-spline surface generation and the commercial software CFD-ACE+. The validity of this shape design analysis is examined using the numerical experiments. Different desired system heat fluxes are considered in the numerical test cases to justify the validity of the present algorithm in solving the three-dimensional shape design problems. Finally, the results show that for the two different cases considered in this work, the maximum increasing in the system heat flux is obtained as 11.3% and 14.1%, respectively. It is also concluded that when the boundary control points of interfacial surface are free to move, maximum system heat flux can be obtained by the present algorithm since it has more degree of freedom in describing the interfacial surface.

2103 三次元効果を考慮した最適化手法による高速鉄道車両のトンネル微気圧波低減(高速化の技術,OS2 交通・物流システムの高速化・利便性・快適性の向上)

2103 三次元効果を考慮した最適化手法による高速鉄道車両のトンネル微気圧波低減(高速化の技術,OS2 交通・物流システムの高速化・利便性・快適性の向上)

Three-dimensional shape design optimization of holes and cavities using the boundary element method

Three-dimensional shape design optimization of holes and cavities under linear elastostatic conditions is presented. The shape optimization technique used is the normal movement approach, whose use has previously been confined to two dimensions, and the technique of stress analysis employed is the boundary element method (BEM) using quadratic surface elements. The normal movement approach is founded on the idea that the optimum boundary shape can be determined by moving points that define the boundary in directions that lie along the local normals to the boundary surface at the points concerned. The amount of movement at each iteration of the process is determined by the local level of stress in the surface. The main advantage of the approach is that no design sensitivity analysis is required, which is computationally more efficient, and many more design variables defining the geometry can be used. The BEM for stress analysis is particularly appropriate because it simplifies the mesh regeneration that is generally required during the optimization process. The quality of this re-meshing is crucial to the success of the technique. The overall method is applied to problems of holes and cavities in engineering components and structures.

Three-dimensional design optimization using the boundary integral equation method

Three-dimensional shape design optimization is demonstrated using the boundary integral equation method. Design sensitivities are obtained directly by differentiating the boundary integral equations with respect to normals to the surfaces at the design variable points. Coon's patches are employed in order to represent continuously changing design surfaces. The Broyden-Fletcher-Goldfarb-Shanno (BFGS) method which requires first-order derivative information has been adopted for the optimization part of the problems. Two examples, a perforated plate under biaxial stresses and a cantilever beam with end shear loading, are demonstrated for the smoothing of stress peaks and stress levelling.

Shape optimization of three-dimensional continuum structures via force approximation techniques

The existing need to develop methods whereby the shape design efficiency can be improved through the use of high-quality approximation methods is addressed. An efficient approximation method for stress constraints in three-dimensional shape design problems is proposed, based on expanding the nodal forces in Taylor series with respect to shape variations. The significance of this new method is shown through elementary beam theory calculations and via numerical computations using three-dimensional solid finite elements. Numerical examples, including the classical cantilever beam structure and realistic automotive parts like the engine connecting rod, are designed for optimum shape using the proposed method. The numerical results obtained from these methods are compared with other published results to assess the efficiency and the convergence rate of the proposed method. It is concluded that, by taking advantage of this high-quality approximation, the total number of finite-element analyses required for structural shape optimization can be reduced significantly, resulting in the same level of efficiency achieved previously in sizing problems.