DESIGN AND FABRICATION OF POWERPOLE MARINE PROPULSION UNIT

ABSTRACT

The design gives details on how the materials are selected, the techniques used, production drawing and the components in electric propulsion drive. The principle of operation of electric propulsion was used and how the electric power voltage (220V) current (5.1A) with power factors (cosФ) 8900.67 was converted to mechanical power output of 0.75KW (1HP) by applying P = V1I1cosФ where P is the output power to drive the shaft to produce effective power of 0.51KW to propel a vessel. The forces, output powers (Ps , PD and calculated; PS is shaft power, PD is the power delivered and PE is the Effective power. Calculated by PD = Ps ×ƞS where ƞS is the efficient of the shaft. PE = PD × ƞD. PE is the effective power while the ƞD is the efficient of the propeller. The speed of electric motor (1HP) n is 310 revolutions per minutes while other speeds at a given delivered power were determined by applying propeller law that says PD ∝ n 3 .The result shows that the voltage varies from 220 – 240V as shaft power and effective power ranges from 0.75 – 0.82kw and 0.496 – 0.545kw respectively.

INTRODUCTION

Mechanism used to move a ship or boat across water. Most modern ships are propelled by mechanical system consisting of motors or engines which are propelled by turning a propeller (Rourke, 2000). A propeller is a type of a fan that transmits power by converting rotational motion into thrust, pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, air or water is accelerated behind the blade. (Shraddha., 2012). In Electric propulsion system, induction motor is used to drive the marine propeller. The control is affected by ocean surface waves, ocean currents, wind, weather and also ship motion. The speed of induction motor is controlled using flux comparator(Shraddha ,2012). The use of electric plant has been increasing in recent years, particularly in areas such as deep-water drilling units, shuttle tankers, offshore supply vessels and other ships which require significant power for propulsion service. Today, the energy sector has available mature electric systems which are robust and have high availability (Peter, 2009). Ships propulsion electrification offers significant anticipated benefits toward ships in terms of reducing ship life cycle cost, increasing ship stealthiness, payload, survivability and power available for non-propulsion-uses, and taking advantage of a strong electrical technological and industrial base. Potential disadvantages include higher near-term costs, increased technical risk, increased system complexity, and less efficiency in full power operations. (Angelos, 2013). A marine propulsion system includes following main parts: main engine, driving device, marine shaft and propeller (Zhou, 2005). The main engine is the impulsion machine engine of the marine propulsion system. The function of the driving device is connecting or parting the energy that the main engine transfers to the marine shaft and the propeller. The marine shaft plays an important role in transferring the energy to the propeller. The propeller promotes the ship to sail. (Conglin, 2013).