Fluid-thermal topology optimization of gas turbine blade internal cooling ducts

Topology optimization uses a variable permeability approach to manipulate flow geometries. Such a method has been employed in the current work to modify the geometric configuration of internal cooling ducts by manipulating the distribution of material blockage. A modified version of the OpenFOAM solver AdjointshapeoptimizationFOAM has been used to optimize the flow path of a serpentine channel and high aspect ratio rectangular ducts, with increase in heat transfer and reduction in pressure drop as the objective functions. These duct shapes are typically used as internal cooling channels in gas turbine blades for sustaining the blade material at high inlet temperatures. The serpentine channel shape was initially topologically optimized, the fluid path from which was post-processed and re-simulated in STAR-CCM+. The end result had an improvement in thermal performance efficiency by 24%. Separation regions were found to be reduced when compared to the original baseline. The second test geometry was a high aspect ratio rectangular duct. Weight factors were assigned to the objective functions in this multi-objective approach, which were varied to obtain a unique shape for each such combination. The addition of mass penalization to the existing objective function resulted in a complex lattice like structure, which was a different outcome in geometry and shape when compared to the case without any additional penalization. The thermal performance efficiency of this shape was found to be higher by at-least 18% when compared to the CFD results of a few other turbulator shapes from literature.

Average temperature of oil-filled transformer windings with partial cooling ducts

An effective one-dimensional model is presented that describes the temperature profile of a winding of an oil-filled distribution transformer with an arbitrary number of partial cooling ducts. An analytical solution of the model is applied to a specific example — a low voltage winding of a 400 kVA distribution transformer with one or two partial cooling ducts. Starting from the exact solution, a simple and practical formula for the temperature rise of similar windings has been derived that is suitable for transformer designers.

Design and Manufacturing of Conformal Cooling for Hot Stamping Dies Using Hybrid Process of Laser Metal Deposition (LMD) and Milling

Hot stamping dies include cooling channels to treat the formed sheet. The optimum cooling channels of dies & molds should adapt to the shape and surface of the dies, so that a homogeneous temperature distribution and cooling are guaranteed. Nevertheless, cooling ducts are conventionally manufactured by deep drilling, attaining straight channels unable to follow the geometry of the tool. Laser Metal Deposition (LMD) is an additive manufacturing technique capable to fabricate nearly free-form integrated cooling channels and therefore shape the so-called conformal cooling. The present work investigates the design and manufacturing of conformal cooling ducts, which are additively built up on hot work steel and then milled in order to attain the final part. Their mechanical performance and heat transfer capability has been evaluated, both experimentally and by means of thermal simulation. Finally, conformal cooling conduits are evaluated and compared to traditional straight channels. The results show that LMD is a proper technology for the generation of cooling ducts, opening the possibility to produce new geometries on dies & molds and, therefore, new products.

Studying a construction of pistons for the aircraft CI engine

This paper examines the selected constructions of piston for aircraft CI engines and discusses tendencies in a development of piston designs. The paper addresses the question of using new materials and coatings to improve quality of pistons and the study of heat transfer and methods to absorb heat from a piston by means of cooling ducts. The selected materials were examined in terms of their advantages and drawbacks. The paper discusses different shapes of piston heads and their impact on combustion as well as indicates other factors behind parameters of combustion and toxic emission like injector shape types, lubrication types and clearances in the combustion chamber.