Shape optimization of staggered ribs in a rotating equilateral triangular cooling channel

Abstract

A rotating equilateral triangular cooling channel with staggered square ribs inside the leading edge of a turbine blade has been optimized in this work based on surrogate modeling. The fluid flow and heat transfer in the channel have been analyzed using three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations under uniform heat flux condition. Shear stress transport turbulence model has been used as a turbulence closure. Computational results for area-averaged Nusselt number have been validated compared to the experimental data. The objectives related to the heat transfer rate and pressure drop has been linearly combined with a weighting factor to define the objective function. The angle of the rib, the rib pitch-to-hydraulic diameter ratio, and the rib width-tohydraulic diameter ratio have been selected as the design variables. Twenty-two design points have been generated by Latin Hypercube sampling, and the values of the objective function have been calculated by the RANS analysis at these points. The surrogate model for the objective function has been constructed using the radial basis neural network method. Through the optimization, the objective function value has been improved by 21.5 % compared to that of the reference geometry.

Exergetic analysis for optimization of a rotating equilateral triangular cooling channel with staggered square ribs

“…Geometry of the cooling channel considered in this work is shown in Fig. 2 which was presented in the previous study [11]. The hydraulic diameter (D h ) of the reference channel is 18.3mm, which is same as that used by Liu et al [9].…”

“…The ribs are installed obliquely to the mainstream flow and the angle of attack (α) is 45° as shown in Fig. 2, same as in the experimental study of Liu et al [9] and the reference study of Park et al [11]. The smooth surface where the ribs are not installed is denoted as the bottom surface.…”

“…Thus, the heat transfer and exergy loss are interrelated from a thermodynamical point of view. In the previous works [10,11] for optimizations of heat transfer augmentation devices, the objective functions related to the heat transfer and friction loss were linearly combined with a weighting factor to constitute a mono-objective function. In that case, the weighting factor should be determined by the designer considering energy economy of the system to be designed.…”

“…Kim and Moon [10] performed the numerical optimization of stepped circular arrays using Kriging method [19] to enhance the heat transfer performance. [11] In the present work, exergy analysis was introduced in optimization of a triangular channel with staggered square ribs, which is located at the leading part of a turbine blade where heavy heat load occurs, to maximize the net exergy gain in the channel using three-dimensional Reynolds-averaged Navier-Stokes (RANS) equations. Design points with three design variables were selected using Latin hypercube sampling (LHS) [17].…”

Multi-objective optimization of asymmetric v-shaped ribs in a cooling channel using CFD, artificial neural networks and genetic algorithms

“…The obtained results of two methods were completely consistent. Moon et al [15] optimized staggered ribs in a rotating equilateral triangular channel. They noted that the most cooling ducts which are located at leading edge have triangular cross section and proper cooling in this area is very important and by this idea they optimized the ducts.…”