quiz1_sol - Massachusetts Institute of Technology...

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Massachusetts Institute of Technology DEPARTMENT OF MECHANICAL ENGINEERING Center of Ocean Engineering 2.611 SHIP POWER and PROPULSION Fall 2006, Quiz 1 - Solutions 1) (20 pts) a) Discuss how Controllable Reversible Pitch (CRP) propellers can help prevent engine overloading. Consider your answer in terms of Torque (Q), angle of attack ( α ), Lift, Drag, Velocity of Advance (J), Pitch, and shaft speed. (The use of all terms is not necessary as long as a logical sound argument is made.) (10pts) A number of factors such as heavy seas, towing evolutions, and / or excessive loading conditions may cause J to decrease. Generally, with CRP propellers operating above 12 knots, the speed of the shaft is programmed to remain constant. To compensate for the decrease in relative water velocity the angle of attack should increase. This will result in an increase in lift and thus require additional torque from the main engines. To bring the engine torque back to its original designed value the pitch is reduced by controlling the angle of attack. This allows the engine to operate at designed torque and prevent overloading b) Discuss the cause of u a and u t . V A ω r+V T V * u a * -u t * V o B i B G The vortex produced by the propeller action affects the flow field over the propeller. These effect velocity in the
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This note was uploaded on 02/24/2012 for the course MECHANICAL 2.611 taught by Professor Davidburke during the Fall '06 term at MIT.

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quiz1_sol - Massachusetts Institute of Technology...

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