Theoretical and Experimental Investigation of Magneto Hydrodynamic Propulsion for Ocean Vehicles
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The concept of Magneto-Hydrodynamic (MHD) propulsion can be used to implement a propeller-less propulsion system for marine vehicles. The basic principle behind MHD is to use the (Lorentz) force produced by the interaction of electric and magnetic fields to generate thrust on a conducting fluid in motion. Electrodes are lined up along the walls of the duct which act as the source of the electric field. Seawater acts as the conducting medium for the current when it passes through the duct. This medium is then subjected to a strong magnetic field within the duct, thereby producing an axial force, i.e., an axial thrust. Propulsion systems based on MHD require virtually no mechanical components, therefore a good application would be to design a propulsor which produces very little noise for small underwater vehicles. Results of a preliminary feasibility study on this application are presented in this thesis. An approximate, consistent MHD propulsion theoretical model to assess the performance of a MHD propulsor for small underwater vehicles is introduced and analyzed. The model is generalized from the hydrodynamic point of view to consider inlet and outlet diffusers. The general model is applied systematically varying the main design parameters with respect to a given autonomous underwater vehicle (AUV) size. The results show that larger magnetic fields, longer propulsor lengths and smaller inlet flow speeds are preferred to get the highest propulsion efficiency and thrust. To check the consistency of the theoretical model, experiments are conducted. The results of these experiments show an approximate relation between the theoretical equations and the actual phenomenon.
General Audience Abstract
In recent years, there has been an increase in the usage of small autonomous (unmanned) underwater vehicles (AUV) for various purposes such as exploration, mining and military applications. Most of these AUVs use the conventional system of a motor and propeller to drive the vehicle. This thesis proposes a different method of propulsion, one without any mechanical moving parts such as a rotor or a motor, for certain applications of these AUVs. The proposed system uses the concept of Magneto-Hydrodynamics (MHD) to propel the vehicle using an interaction between the applied magnetic and electric fields inside the propulsion channel. These applied fields produce a force (Lorentz) on the fluid that is present in the channel, thereby creating thrust to propel the vehicle. In the present case, the fluid is the electrically conducting seawater. Since, propulsion systems based on MHD require no mechanical components, they produce very little noise and are ideal for applications that require stealth. A feasibility study on this application is introduced, analyzed and presented in this thesis. Parameters such as applied fields, propeller configurations, and propeller shape and size are varied with respect to a given AUV size, to understand how each variable effects the system. The results show that larger magnetic fields, longer propulsor lengths and smaller inlet flow speeds are preferred to get the highest propulsion efficiency and thrust. To check the consistency of the theoretical model, experiments are conducted. The results of these experiments show an approximate relation between the theoretical equations and the actual phenomenon.
- Masters Theses