“Mircea cel Batran” Naval Academy Scientific Bulletin, Volume XIX – 2016 – Issue 1 Published by “Mircea cel Batran” Naval Academy Press, Constanta, Romania // The journal is indexed in: PROQUEST / DOAJ / DRJI / JOURNAL INDEX / I2OR / SCIENCE LIBRARY INDEX / Google Scholar / Crossref / Academic Keys / ROAD Open Access / OAJI / Academic Resources / Scientific Indexing Services / SCIPIO 202 DOI: 10.21279/1454-864X-16-I1-035 © 2015. This work is licensed under the Creative Commons Attribution-Noncommercial-Share Alike 4.0 License. THE QUALITY FACTOR OF THE NAVAL M.H.D PROPULSION SYSTEM Vasile DOBREF 1 Paul BURLACU 2 Petrică POPOV 3 Florenţiu DELIU 4 Mitruț C. CARAIVAN 5 1 Professor PhD eng. Naval Academy “Mircea cel Batran”, Constanța, vasile.dobref@anmb.ro 2 Lecturer PhD eng. Naval Academy “Mircea cel Batran”, Constanța, paul.burlacu@anmb.ro 3 Lecturer PhD Naval Academy “Mircea cel Batran”, Constanța, petrica.popov@anmb.ro 4 Lecturer PhD eng. Naval Academy “Mircea cel Batran”, Constanța, florentiu.deliu@anmb.ro 5 PhD eng., Naval Academy “Mircea cel Batran”, Constanța, caraivanmitrut@gmail.com Abstract: A naval propulsion magnetohydrodynamic (M.H.D.) induction is actually a linear induction machine that uses seawater as induced. In seawater occurs an interaction between a magnetic field induced by the progressive currents, resulting an electromagnetic force. This force causes the movement of water, which is discharged from the vessel through a nozzle, thus creating a reactive propellant. Such a propulsion system eliminates the propeller and its annexes reducing energy losses associated with the rotation of water, noise and cavitation. Keywords: magnetohydrodinamic; propulsion system; magnetic force 1. Introduction A soundless navigation is essential for a submarine patrol in the maritime area. MHD ship propeller being a linear induction machine, characterized by the size of its effectiveness is called ’’the quality factor’’ Q, defined of Laithwaite as the ratio magnetizing reactance and the resistance of the armature: 2 2 R L Q ω = (1) This definition follows the relationship h Δ ρ π f μ τ 2 Q 0 p = (2) Where: p τ is the polar step; 0 μ -the vacuum permeability; f - sequence power, resistivity; ρ, Δ - armature thickness and size of the air gap h. If an induction machine with the induced seawater, applying relation (1) becomes quite difficult for obvious reasons; therefore, assume a redefinition of energy quality factor considerations. The machine absorbs from the energy source which dissipates in the form of active power and some stores as reactive energy accumulated in the air gap magnetic field. If we denote j W , Joule energy dissipation and m W magnetic field energy in air gap, this report is written as m j W W R = (3) We believe that the electrical machine will be all the more efficiency as muh the ratio of the dissipation and accumulated energy will be higher and we propose to characterize the size MHD thruster naval by so called "energy report" R. We further demonstrate that the ratio of energy quality factor Q and R expresses the same physical reality. For this, we calculate the energies j W , respectively m W . Polyphase windings of the inductor will generate a magnetic field in the airgap, having the character of wave intensity expressed by the ) sin( ) , ( p m x t H t x H τ π ω − = (4) This field is moving at synchronous speed: f v p s τ 2 = (5) to a designated location. If the armature is moving at speed v, the relative velocity to the induced magnetic field will be: 0 v v v s r − = (6) The field gradually travels a distance equal to one polar step during: