Aeronautical Engineering: A special bibliography with indexes, supplement 55

This bibliography lists 260 reports, articles, and other documents introduced into the NASA scientific and technical information system in February 1975

Computational and Experimental Study on Innovative Horizontal-Axis Wind Turbine Blade Designs

This study was made to explore three novel blade geometries with intent to increase power production of a horizontal axes, three blade arrangement wind turbine. This was done by designing the blades using computer aided design (CAD) modeling software, followed by a rigorous testing phase, utilizing a computational fluid dynamics software (CFD). The blades then went into a cycle of iterative design to achieve the best parameters that will positively impact the overall power generation efficiency. These steps were followed by printing the blades utilizing 3D Printing technology, testing them for the power generation, and finally, tabulating these findings to validate the numerical results gathered using CFD software. The blade designs under investigation here are the slotted blade (blade with slot shaped cavity on leading edge extending to lower surface), A blade resembling the tubercles (local inflation or bulges on surface) found on a humpback whale and the winglet blade, which was compared to the baseline traditional straight blade. The slotted, tubercle and straight blade were experimentally investigated, while the winglet blade underwent a CFD study only and compared to the other designs. It was found experimentally that the slotted blade generates 26.1% more power on average than the straight blade, and was found very ideal for low wind vacancies, while the tubercle was found of less effectiveness than the straight, though it possesses superior characteristics in suppressing the resultant noise, which is a common wind turbine problem. The winglet showed very similar in results to the straight blade, where its addition would come very fruitful at higher wind velocities, due to the fact that the inertial forces needed to start the operation is a higher order of magnitude than the straight blade

Optimization of 5-Axis milling processes based on the process models with application to airfoil machining

5-axis milling is widely used in machining of complex surfaces such as airfoils. Improper selection of machining parameters may cause low productivity and undesired results during machining. There are several constraints such as available power and torque, chatter stability, tool breakage etc. In order to respect such constraints proper machining parameters should be determined. In this paper, methodologies for improving 5-axis milling processes are presented. Selection of machining parameters is performed using process simulations. The developed methodologies are presented on an example airfoil

Rapid manufacturing technique used in the development of a regenerative pump impeller

This paper presents a method of rapid manufacture used in the development of a regenerative pump impeller. Rapid manufacturing technology was used to create complex impeller blade profiles for testing as part of a regenerative pump optimisation process. Regenerative pumps are the subject of increased interest in industry. Ten modified impeller blade profiles, from the standard radial configuration, were evaluated with the use of computational fluid dynamics and experimental testing. Prototype impellers were needed for experimental validation of the CFD results. The manufacture of the complex blade profiles using conventional milling techniques is a considerable challenge for skilled machinists. The complexity of the modified blade profiles would normally necessitate the use of expensive CNC machining with 5 axis capability. With an impeller less than 75 mm in diameter and a maximum blade thickness of 1.3mm, a rapid manufacturing technique enabled production of complex blade profiles that were dimensionally accurate and structurally robust enough for testing. As more advanced rapid prototyping machines become available in the study in the future, e.g. 3D photopolymer jetting machine, the quality of the parts particularly in terms of surface finish will improve and the amount of post processing operations will reduce. This technique offers the possibility to produce components of increased complexity whilst ensuring quality, strength, performance and speed of manufacture. The ability to manufacture complex blade profiles that are robust enough for testing, in a rapid and cost effective manner is proving essential in the overall design optimisation process for the pump

Aeronautical Engineering. A continuing bibliography with indexes, supplement 156

This bibliography lists 288 reports, articles and other documents introduced into the NASA scientific and technical information system in December 1982

Development of a regenerative pump impeller using rapid manufacturing techniques

This paper presents a method of rapid manufacture used in the development of a regenerative pump impeller. Rapid manufacturing technology was used to create complex impeller blade profiles for testing as part of a regenerative pump optimisation process. Regenerative pumps are the subject of increased interest in industry. Ten modified impeller blade profiles, relative to the standard radial configuration, were evaluated with the use of computational fluid dynamics and experimental testing. Prototype impellers were needed for experimental validation of the CFD results. The manufacture of the complex blade profiles, using conventional milling techniques, is a considerable challenge for skilled machinists. The complexity of the modified blade profiles would normally necessitate the use of expensive CNC machining with 5 asis capability. With an impeller less than 75mm in diameter and a maximum blade thickness of 1.3mm, a rapid manufacturing technique enabled production of complex blade profiles that were dimensionally accurate and structurally robust enough for testing. As more advanced rapid prototyping machines become available in the study in the future, e.g. 3D photopolymer jetting machine, the quality of the parts, particularly in terms of surface finish, will improve and the amount of post processing operations will reduce. This technique offers the possibility to produce components of increased complexity whilst ensuring quality, strength, performance and speed of manufacture. The ability to manufacture complex blade profiles that are robust enough for testing, in a rapid and cost effective manner is proving essential in the overall design optimisation process for the pump

Simulation of a finishing operation : milling of a turbine blade and influence of damping

Milling is used to create very complex geometries and thin parts, such as turbine blades. Irreversible geometric defects may appear during finishing operations when a high surface quality is expected. Relative vibrations between the tool and the workpiece must be as small as possible, while tool/workpiece interactions can be highly non-linear. A general virtual machining approach is presented and illustrated. It takes into account the relative motion and vibrations of the tool and the workpiece. Both deformations of the tool and the workpiece are taken into account. This allows predictive simulations in the time domain. As an example the effect of damping on the behavior during machining of one of the 56 blades of a turbine disk is analysed in order to illustrate the approach potential

Simulation of a finishing operation : milling of a turbine blade and influence of damping

Milling is used to create very complex geometries and thin parts, such as turbine blades. Irreversible geometric defects may appear during finishing operations when a high surface quality is expected. Relative vibrations between the tool and the workpiece must be as small as possible, while tool/workpiece interactions can be highly non-linear. A general virtual machining approach is presented and illustrated. It takes into account the relative motion and vibrations of the tool and the workpiece. Both deformations of the tool and the workpiece are taken into account. This allows predictive simulations in the time domain. As an example the effect of damping on the behavior during machining of one of the 56 blades of a turbine disk is analysed in order to illustrate the approach potential

Aeronautical engineering: A continuing bibliography, supplement 122

This bibliography lists 303 reports, articles, and other documents introduced into the NASA scientific and technical information system in April 1980

Measurements and computational analysis of heat transfer and flow in a simulated turbine blade internal cooling passage

Visual and quantitative information was obtained on heat transfer and flow in a branched-duct test section that had several significant features of an internal cooling passage of a turbine blade. The objective of this study was to generate a set of experimental data that could be used to validate computer codes for internal cooling systems. Surface heat transfer coefficients and entrance flow conditions were measured at entrance Reynolds numbers of 45,000, 335,000, and 726,000. The heat transfer data were obtained using an Inconel heater sheet attached to the surface and coated with liquid crystals. Visual and quantitative flow field results using particle image velocimetry were also obtained for a plane at mid channel height for a Reynolds number of 45,000. The flow was seeded with polystyrene particles and illuminated by a laser light sheet. Computational results were determined for the same configurations and at matching Reynolds numbers; these surface heat transfer coefficients and flow velocities were computed with a commercially available code. The experimental and computational results were compared. Although some general trends did agree, there were inconsistencies in the temperature patterns as well as in the numerical results. These inconsistencies strongly suggest the need for further computational studies on complicated geometries such as the one studied