Experimental Analysis of Additively Manufactured Latticework Coupons

Abstract

The capabilities and the precision of additive manufacturing processes have been tremendously increased in the last years, and this trend is not expected to be close to an end. Researchers, in the gas turbine industry, are focusing on the technology implementation on cooling systems. The aim of the present work is to investigate the performances of eight different geometries in order to exploit the cooling potential of some challenging latticework schemes with respect to traditional ones such as smooth channel, dimples, and pin fins. Test coupons consisting of those cooling structures embedded inside a rectangular cooling channel with dimensions of 56 mm width, 5 mm height, and 68 mm length were fabricated by means of direct metal laser melting technique. Since an aim of the present work is to evaluate the shape deformation associated with this additive process, the results of the CT scan imaging technique are presented. The performances are characterized both in terms of averaged heat transfer and friction factor values inside the test coupons by means of steady-state technique with a constant wall temperature boundary condition. The investigated flow Reynolds numbers range from 18, 000 to 40, 000. These values allow the authors to provide a deeper understanding of the latticework structures performances at Reynolds numbers beyond the range typically investigated in the literature. An efficiency index is employed to compare the performances of each geometry. Although the obtained results reveal that none of the tested geometries outperforms the other ones, the latticework arrangements show a heat transfer enhancement with respect to a porosity decrease. In addition, the good capability in terms of heat transfer of the lattice structures measured in the present work suggests the use of such technologies for twofold optimization process based on mechanical resistance and heat transfer characteristics.