Verification of a chamberless HLFC design with an outer skin of variable porosity

A chamberless HLFC leading edge segment featuring an outer skin with variable porosity has been designed, manufactured and wind tunnel tested under flight Reynolds-number conditions. The aerodynamic design involved the extention of current HLFC design routines to variable pressure loss characteristics of the outer skin. Advanced options for structural design and manufacturing solutions with focus on industrialization, arising from the avoidance of aerodynamically driven chambering, are explored. The leading edge segment has been installed on an existing vertical tail-plane model and tested at the large low-speed wind-tunnel facility DNW-LLF. The design process and some results of the successful verification of the chamberless design are presented herein.

A Robust Multi-Circle Detector Based on Horizontal and Vertical Search Analysis Fitting with Tangent Direction

In this paper, we propose an efficient Multi-Circle detector which follows the fixed search order. The method makes use of horizontal and vertical search to realize circle detection, which is named as HVCD. First, this method computes edge areas in a given image. The edge areas could be divided into some regions by means of region growing. Each of regions could be efficiently searched to achieve not only one-pixel wide edges but edge segments as well. Next, the candidate circles can be extracted from every edge segment. Finally, the circle candidates could be validated with the help of Helmholtz principle. Experimental results demonstrate that HVCD could effectively detect circles on synthetic and natural images on the one hand; on the other hand, HVCD here could solve the weakness in the process of circle Hough transform implementation and EDcircles implementation.

Research on parametric modeling and grinding methods of bottom edge of toroid-shaped end-milling cutter

For a toroid-shaped end-milling cutter to have multi-structure features of tooth offset center and introversion of bottom edge, this article proposes a generalized parametric modeling method of the bottom edge, including a straight edge segment and a circular arc edge segment. And based on the parametric model, this article also deduces the corresponding tool path for grinding of the bottom edge’s rake and flank faces. The parametric modeling method is based on the geometric analytic equations while the grinding method is driven by the proposed parametric model and the parameters of rake and flank faces. The two methods can be applied to a bottom edge of a cutter with multi-structure features to guarantee G1 continuity at the two joints for connecting a circular arc edge with a straight edge and a conical helix edge, respectively. In order to verify the accuracy of proposed methods, experiments were carried out. The modeling and grinding experimental results verified the accuracy and utility of the methods.

Characterization of Laser Additive Manufacturing-Fabricated Porous Superalloys for Turbine Components

The limits of gas turbine technology are heavily influenced by materials and manufacturing capabilities. Lately, incremental performance gains responsible for increasing the allowable turbine inlet temperature (TIT) have been made mainly through innovations in cooling technology, specifically convective cooling schemes. Laser additive manufacturing (LAM) is a promising manufacturing technology that uses lasers to selectively melt powders of metal in a layer-by-layer process to directly manufacture components, paving the way to manufacture designs that are not possible with conventional casting methods. This study investigates manufacturing qualities seen in LAM methods and its ability to successfully produce complex features found in turbine blades. A leading edge segment of a turbine blade, containing both internal and external cooling features, along with an engineered-porous structure is fabricated by laser additive manufacturing of superalloy powders. Through a nondestructive approach, the presented geometry is analyzed against the departure of the design by utilizing X-ray computed tomography (CT). Variance distribution between the design and manufactured leading edge segment are carried out for both internal impingement and external transpiration hole diameters. Flow testing is performed in order to characterize the uniformity of porous regions and flow characteristics across the entire article for various pressure ratios (PR). Discharge coefficients of internal impingement arrays and engineered-porous structures are quantified. The analysis yields quantitative data on the build quality of the LAM process, providing insight as to whether or not it is a viable option for direct manufacture of microfeatures in current turbine blade production.

Characterization of LAM-Fabricated Porous Superalloys for Turbine Components

The limits of gas turbine technology are heavily influenced by materials and manufacturing capabilities. Inconel alloys remain the material of choice for most hot gas path components in gas turbines, however recent increases in turbine inlet temperature (TIT) are associated with the development of advanced convective cooling methods and ceramic thermal barrier coatings (TBC). Increasing cycle efficiency and cycle specific work are the primary drivers for increasing TIT. Lately, incremental performance gains responsible for increasing the allowable TIT have been made mainly through innovations in cooling technology, specifically convective cooling schemes. An emerging manufacturing technology may further facilitate the increase of allowable maximum TIT, thereby impacting cycle efficiency capabilities. Laser Additive Manufacturing (LAM) is a promising manufacturing technology that uses lasers to selectively melt powders of metal in a layer-by-layer process to directly manufacture components, paving the way to manufacture designs that are not possible with conventional casting methods. This study investigates manufacturing qualities seen in LAM methods and its ability to successfully produce complex features found in turbine blades. A leading edge segment of a turbine blade, containing both internal and external cooling features, along with an engineered-porous structure is fabricated by laser additive manufacturing of superalloy powders. Various cooling features were incorporated in the design, consisting of internal impingement cooling, internal lattice structures, and external showerhead or transpiration cooling. The internal structure was designed as a lattice of intersecting cylinders in order to mimic that of a porous material. Variance distribution between the design and manufactured leading edge segment are carried out for both internal impingement and external transpiration hole diameters. Through a non-destructive approach, the presented geometry is further analyzed against the departure of the design by utilizing x-ray computed tomography (CT). Employing this non-destructive evaluation (NDE) method, a more thorough analysis of the quality of manufacture is established by revealing the internal structures of the porous region and internal impingement array. Flow testing was performed in order to characterize the uniformity of porous regions and flow characteristics across the entire article for various pressure ratios (PR). Discharge coefficient of internal impingement arrays and porous structure are quantified. The analysis yields quantitative data on the build quality of the LAM process, providing insight as to whether or not it is a viable option for manufacture of micro-features in current turbine blade production.