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No description available.

No description available.

The main objective of this research work is to develop a simulation procedure for modeling the soil-tool interaction for a blade of arbitrary shape. The primary motivation for this study is developing agricultural robots with limited power and pulling force to help farmers in crop production. In this thesis, a finite element (FE) investigation of soil-blade interaction is presented. The soil is considered as an elastic-plastic material with the non-associated Drucker-Prager constitutive law. A separation procedure to model the cutting of soil and a method of calculating the forces acting on the blade are proposed and discussed in detail. The procedure uses a separation criterion that becomes active at consecutive nodes on the predefined separation surfaces. In order to mimic soil-blade sliding and soil-soil cutting phenomena contact elements with different properties are applied. To verify correctness of the FE model developed and the procedures used, the FE results are first compared with analytical results available for straight rectangular blades from classical soil mechanics theories; and then the FE results are compared with the experimental ones. Also the effects of blade width, depth and rake angle on blade’s draft force were studied by simulating soil-blade interaction with different blade’s dimensions. After the analytical and experimental validation of the results for straight rectangular blade, the rectangular curved shape blade was modeled in order to investigate the effects of changing the blade’s radius of curvature on the blade’s draft force. The soil interaction with straight triangular blade in different rake angles was simulated next. Since the analytical solutions are limited to rectangular blades, calculated draft forces for triangular blade were verified only experimentally. The triangular and rectangular blades with the same width and depth of interaction were also investigated. The results showed that triangular blade draft force is around half of the amount of force acting on the rectangular blade with the same rake angle. Also the effect of triangular blade’s sharpness and changing the blade’s radius of curvature on draft force was discussed. By changing the blade’s sharpness, the draft forces of triangular blade were calculated in two conditions of constant blade’s width and constant blade’s contact length. The approach presented in this thesis can be used to investigate the soil-tool interactions for real and more complex blade geometries and soil conditions, and ultimately for improving design of blades to be used in tillage operations.

Gas turbine blades are subject to harsh operating conditions that require innovative cooling techniques to insure reliable operation of parts. Film-cooling and internal cooling techniques can prolong blade life and allow for higher engine temperatures. This study examines several unique methods of cooling the turbine blade tip. The first method employs holes placed directly in the tip which inject coolant onto the blade tip. The second and third methods used holes placed on the pressure side of a blade near the tip representative of two different manufacturing techniques. The fourth method is a novel cooling technique called a microcircuit, which combines internal convection and injection from the pressure side near a turbine blade tip. Wind tunnel tests are used to observe how effectively these designs cool the tip through adiabatic effectiveness measurements and convective heat transfer measurements. Tip gap size and blowing ratio are varied for the different tip cooling configurations. Results from these studies show that coolant injection from either the tip surface or from the pressure side near the tip are viable cooling methods. All of these studies showed better cooling could be achieved at small tip gaps than large tip gaps. The results in which the two different manufacturing techniques were compared indicated that the technique producing more of a diffused hole provided better cooling on the tip. When comparing the thermal performance of all the cooling schemes investigated, the added benefit of the internal convective cooling shows that the microcircuit outperforms the other designs. / Master of Science

In recent years, the demand for wind energy has dramatically increased as well as the number and size of commercial wind turbines. These large turbines are loud and can cause annoyance to nearby communities. Therefore, the prediction of large wind turbine noise over long distances is critical. The wind turbine noise prediction is a very complex problem since it has to account for atmospheric conditions (wind and temperature), ground absorption, un-even terrain, turbine wake, and blade deformation. In these large turbines, the blade deflection is significant and it can potentially influence the noise emissions. However, the effects of blade flexibility on turbine noise predictions have not been addressed yet, i.e. all previous research efforts have assumed rigid blades. To address this shortcoming, the present work merges a wind turbine aeroelastic code, FAST (Fatigue, Aerodynamics, Structures, and Turbulence) to a wind turbine noise code, WTNoise, to compute turbine noise accounting for blade aeroelasticity. Using the newly developed simulation tool, the effects flexible blades on wind turbine noise are investigated, as well as the effects of turbine parameters, e.g. wind conditions, rotor size, tilt, yaw, and pre-cone angles. The acoustic results are shown as long term average overall sound power level distribution over the rotor, ground noise map over a large flat terrain, and noise spectrum at selected locations downwind. To this end, two large wind turbines are modeled. The first one is the NREL 5MW turbine that has a rotor diameter of 126 m. The second wind turbine, the Sandia 13.2MW, has a rotor diameter of 206 m. The results show that the wind condition has strong effects on the noise propagation over long distances, primarily in the upwind direction. In general, the turbine parameters have no significant effects on the average noise level. However, the turbine yaw impacts significantly the turbine noise footprint by affecting the noise propagation paths. The rotor size is also a dominating factor in the turbine noise level. Finally, the blade aeroelasticity has minor effects on the turbine noise. In summary, a comprehensive tool for wind turbine noise prediction including blade aeroelasticity was developed and it was used to address its impact on modern large turbine noise emissions. / Master of Science / Large wind turbines provide sustainable renewable energy but create loud noise that causes annoyance to nearby communities. Therefore, the prediction of large wind turbine noise is critical, but a complex problem, especially for the propagation over a long distance. The noise prediction needs to account for the turbine design, atmospheric factors, terrain, and airflow. Furthermore, in these large turbines, the blade deflection is significant and it can potentially influence the noise prediction. The present work addresses the above factors in the wind turbine noise prediction by merging a wind turbine structural code, FAST (Fatigue, Aerodynamics, Structures, and Turbulence) to a wind turbine noise code, WTNoise, to compute turbine noise accounting for blade deflection. Two turbines that have rotor diameter larger than 100 m were modeled and studied under different wind turbine design specifications, wind conditions, and blade deflection assumptions. The results showed that the rotor size is one of the dominating factor of turbine noise level. The blade deflection only has minor effects on the turbine noise. In summary, a comprehensive tool for wind turbine noise prediction including blade deflection was developed and used to address its impact on modern large turbine noise emissions.

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Wind power counts for roughly 3 % of the global electricity production. In the chase to produce greener power, much attention lies on getting more electricity from the wind, extraction of kinetic energy, with help of wind turbines. Wind turbines have been used for electricity production since 1887 and have since then developed into more efficient designs and become significantly bigger and with a higher efficiency. The operational conditions change considerably over the rotor length. Inner sections are typically exposed to more complex operational conditions than the outer sections. However, the outer blade sections have a much larger impact on the power and load generation. Especially here the demand for good aerodynamic performance is large. Airfoils have to be identified and investigated on mid/outer sections of a 7.0 MW rotor with 165 m diameter. Blade performance criteria were determined and investigations like sensitivity analysis were made. With the use of XFLR5 (XFoil) and Qblade, the airfoils were made into a blade and tested with the blade element momentum theory. This simulation gave detailed information regarding performance and operational loads depending on the different airfoils used. These results were then validated in a professional aero-elastic code (Flex5), simulating steady state, turbulent and wind shear conditions. The best airfoils to use from this reports airfoil catalogue are the NACA 63-6XX and NACA 64-6XX. With the implementation of these airfoils, blade design 2 and 3 have a very high performance coefficient compared to large commercial HAWT rotors.

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This report contains the development and construction of a new patented doctor blade. A doctor blade is used when creping soft paper from a large rotating Yankee cylinder. At the current state the doctor blade are in use for four to six hours before it needs to be switch due to wearing, stopping the production of soft paper. The new idea is to have a very long and small blade that will slide into a fixed blade and be continuously pulled when creping paper. The company CS Production had a concept of the fixed blade but wanted to further develop it since the blade was too wide.   Measurements where done with the old blade and with the old testing device to measure the pull force required to pull the blade. New concepts where made by the method of brainstorming and evaluated with an elimination matrix. Rivet joints where selected as the joining technique for the new design. The new concept contains one dominant blade that smaller parts were assembled to form the final blade. The material selected for the dominant blade and the section blade was a cold rolled stainless spring steel strip and for the middle disc the material was aluminum bronze string casted. Test on the pull force required where done with the new doctor blade in the new test rig.  FEM simulation where done on a small part of the blade to see where stresses are occurring in the blade. The FEM result showed that no stresses where on the middle discs, rivets or section blades. This is not reliable results because the small doctor blade is pushing down onto the middle discs and stresses should be occurring on the discs.  Further testing is needed to see if the blade can withstand the forces applied to it.