Thesis (Ph. D.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographical references.

Revisa os métodos para cálculo de desempenho e ruído de hélices. Apresenta um método para determinação de desempenho de hélices com mínima perda de energia usando a teoria dos vórtices. Faz uso das tabelas de Goldstein que criam automaticamente a geometria da hélice através do acesso a um banco de dados aerodinâmico. Avalia o ruído harmônico com o método no domínio da freqüência, utilizando os valores de desempenho e geometria previamente calculados. Valida o método de desempenho e ruído através da comparação com dados experimentais. Apresenta um estudo de caso para desempenho e ruído de hélices aplicados a ultraleves e aviação geral e compara as diferentes configurações e seus efeitos no desempenho e ruído. Conclui que a simplicidade de implantação do método o torna indicado para o projeto preliminar e permite que seja integrado com modelos de otimização. / This paper reviews the methods of propeller performance and noise calculation. It presents a prediction method for propellers performance with minimum energy loss. The method uses the vortex theory, using the Goldstein circulation function tables for performance determination, linked with an aerodynamic database for propeller geometry generation. The results are used for a quick evaluation of propeller harmonic noise through the frequency domain method. The method is validated by comparison with experimental data. It presents a case study of propeller designed for a very light aircraft, comparing different configurations and its effects on performance and noise. The method is recommended in the framework of preliminary design and for integration with optimization algorithms.

The goal of this design process was to achieve the most efficient propulsive system for the candidate autonomous underwater vehicle (AUV) as possible. A mathematical approach, using fundamental motor equations and derived quantities, was used to characterize and select an efficient brushless electric motor for the propulsion system. A program developed at MIT, Massachusetts Institute of Technology, called OpenProp versions 1 and 2.3 was utilized to design a custom propeller that maximizes the efficiency of the system. A brushless electric motor was selected for the candidate AUV based on a survey of available off the shelf motors and a mathematical characterization process. In parallel with the motor characterization a propeller design was optimized using OpenProp v1 to perform a parametric analysis. OpenProp v2.3 was then used to design a unique propeller for the selected motor. The propeller design resulted in a final propeller with an efficiency of 79.93%. The motor characterization process resulted in two candidate motors being selected, the NeuMotor 1925-3Y and NeuMotor 1521-10.5Y, for in house testing and evaluation. A total propulsive system efficiency of between 44% and 46% was achieved depending on which motor is selected for the final design. / Master of Science

One of the largest design considerations for autonomous underwater vehicles (AUV's) that have specific mission scenarios is the propulsive efficiency. The propulsive efficiency affects the amount of power storage required to achieve a specific mission. As the efficiency increases the volume of energy being stored decreases. The decrease in volume allows for a smaller vehicle, which results in a vehicle that requires less thrust to attain a specific speed. The process of selecting an efficient propulsive system becomes an iterative process between motor, propeller, and battery storage. Optimized propulsion systems for mission specific AUV's require costly motor and propeller fabrication which may not be available to the designer. Recent advancements in commercially available electric motors and propellers allows for cost effective propulsion systems. The design space selection of motors and propellers has recently increased due to component demand of remote control airplane and boats. The issue with such systems is how to predict small propeller and small motor performance interactions since remote control motor and propeller designers usually don't provide enough information about the performance of their product. The mission statement is to design a propeller and motor combination that will allow an autonomous underwater vehicle to travel large distances while maintaining good efficiency. The vehicle will require 12 N of thrust with a forward velocity of 2 m/s. The propeller needs to be larger than 2.5â due to inflow velocity interaction and smaller than 4â due to loss of thrust when in surface transit due to suction. / Master of Science

Reverse thrust operations of a model scale Contra-Rotating Open Rotor design were numerically modelled to produce individual rotor thrust and torque results comparable to experimental measurements. The aims of this research were to develop an understanding of the performance and aerodynamics of open rotors during thrust reversal operations and to establish whether numerical modelling with a CFD code can be used as a prediction tool given the highly complex flowfield. A methodology was developed from single rotor simulations initially before building a 3D‘frozen rotor’ steady-state approach to model contra-rotating blade rows in reverse thrust settings. Two different blade pitch combinations were investigated (β1,2 =+30°,- 10° and β1,2 =-10°,-20°). Thrust and torque results compared well to the experimental data and the effects of varying operating parameters, such as rpm and Mach number, were reproduced and in good agreement with the observed experimental behaviour. The main flow feature seen in all the reverse thrust cases modelled, both single rotor and CROR, is a large area of recirculation immediately downstream of the negative pitch rotor(s).This is a result of a large relative pressure drop region generated by the suction surfaces of the negative pitch blades. An initial 3D unsteady sliding-mesh calculation was performed for one CROR reverse thrust case. The thrust and torque values were in poor agreement with experimental values and the disadvantages relating to time costs and required computational resources for this technique were illustrated. However, the results did yield a nominal unsteady variation of thrust and torque due to rotor phase position. Overall the work shows that it may be possible to develop a CROR reverse thrust prediction tool of beneficial quality using CFD models. The research also shows that the frozen rotor approach can be adopted without undermining the fidelity of the results.

A fundamental aerodynamic analysis technique for a single straight fixed wing has been expounded upon and turned into a modern technique that can analyze multiple wings of more realistic shapes common on aircraft. This modern technique is extended further to apply towards propellers. A method to overcome propeller analysis problems at low airspeeds is presented. This method is compared to more traditional propeller analysis techniques.

A three dimensional viscous/inviscid interactive boundary layer method for predicting the effects of fluid viscosity on the performance of fully wetted propellers is presented. This method is developed by coupling a three dimensional low-order potential based panel method and a two dimensional integral boundary layer analysis method. To simplify the solution procedures, this method applies a reasonable assumption that the effects of the boundary layer along the span wise direction (radially outward for propeller blades) could be negligible compared with those along the stream wise direction (constant radius for propeller blades). One significant development of this method, compared with previous work, is to completely consider the effects of the added sources on the whole blades and wakes rather than evaluate the boundary layer effects along each strip, without interaction among strips. This method is applied to Propeller DTMB4119, Propeller NSRDC4381 and DTMB Duct II for validation. The results show good correlation with experimental measurements or RANS (ANSYS/FLUENT) results. The method is further used to develop a viscous image model for the cases of three dimensional wing blades between two parallel slip walls. An improved method for hydrofoils and propeller blades with non-zero thickness or open trailing edges is presented as well. The method in this thesis follows the idea of Pan (2009, 2011), but applies a new extension scheme, which uses second order polynomials to describe the extension edges. A improved simplified search scheme is also used to find the correct shape of the extension automatically to ensure the two conditions are satisfied. / text

This thesis addresses the optimization and design of turbine and propeller blades through the use of a lifting line model. An existing turbine optimization methodology has been modified to include viscous terms, non-linear terms, and a hub model. The method is also adapted to the optimization of propellers. Two types of trailing wake geometries are considered: one based on helical wakes which are aligned at the blade (using the so-called "moderately loaded propeller'' assumption), and a second one based on a full wake alignment model in order to represent more accurately the wake geometry and its effect on the efficiency of the rotor. A comparison of the efficiencies and the loading distributions obtained through the present methods is presented, as well as convergence and numerical accuracy studies, and comparisons with existing analytical results. In the case of turbines, various types of constraints are imposed in the optimization method in order to avoid abrupt changes in the designed blade shape. The effect of the constraints on the efficiency of the turbines is studied. Once the optimum loading has been determined, the blade geometry is generated for given chord, thickness and camber distributions. Finally, a low-order potential-based boundary element method and a vortex-lattice method are used to verify the efficiency of the designed turbines. / text

A two-dimensional viscous-inviscid interactive boundary layer method is applied to three dimensional problems of flow around ducts and ducted propellers. The idea is to predict the effects of fluid viscosity on three dimensional geometries, like ducts, using a two-dimensional boundary layer solver to avoid solving the fully three dimensional boundary layer equations, assuming that the flow is two-dimensional on individual sections of the geometry. The viscous-inviscid interactive method couples a perturbation potential based inviscid panel method with a two-dimensional viscous boundary layer solver using the wall transpiration model. The boundary layer solver used in the study solves for the integral boundary layer characteristics given the edge velocity distribution on the geometry. The viscous-inviscid coupling is applied in a stripwise manner but by including the interaction e ffects from other strips. An important development in this thesis is the consideration of eff ects of other strips in a more rational and accurate manner, leading to improved results in the cases examined when compared to the results of a previous method. In particular, the effects of potentials due to other strips arising out of the three dimensional formulation are considered in this thesis. The validity of assuming two-dimensional flow along individual sections for application of viscous-inviscid coupling is investigated for the case of an open propeller by calculating the boundary layer characteristics in the direction normal to the assumed direction of two-dimensional flow from data obtained by RANS simulations. Also, a previous method which models the flow around the trailing edge of blunt hydrofoils has been improved and extended to three dimensional axisymmetric ducts. This method is applied to ducts with blunt and sharp trailing edges and to a ducted propeller. Correlations of results with experiments and simulations from RANS are shown. / text

Ulm, Univ., Diplomarbeit, 2008.