30.Magnetic bearings are used in applications where noise and vibration are important
considerations or where lubricants are not acceptable. Like the hydrostatic bearings they
do not require shaft rotation to generate bearing support forces. The rotor is floated in the
space and levitated by magnetic forces, which are generated within the bearing by
magnets. Therefore,
(A)the air is necessary to be used as the lubricant to provide the film pressure for magnetic
bearings.
(B)the air is necessary to be used as the lubricant to reduce the noise and vibration for
magnetic bearings.
(C)the shaft rotation is important for generating the supporting forces for the magnetic
bearings.
(D)the magnetic forces are generated in the magnetic bearing to support the load of
bearing.
31.Turbocharging tends to reduce fuel consumption because the friction losses of the
turbocharged engine do not increase as fast as the increase in power output, and because
the improved charging results in better combustion conditions. Based on this description,
which is the correct statement?
(A)The friction losses of the turbocharged engine are beneficial for reducing fuel
consumption.
(B)The better combustion conditions resulted from the improved charging are beneficial for
reducing fuel consumption.
(C)The friction losses of the turbocharged engine are beneficial for better combustion
conditions.
(D)The increased friction losses of the turbocharged engine are beneficial for better
combustion condition.
32.Which is the equipment in a ship that often uses the heat recovered from the jacket water
of a main diesel engine?
(A)Superheater of boiler
(B)Freshwater generating plant
(C)Exhaust-gas boiler
(D)Turbo-generator
33.Misalignment in shafting systems can produce very significant bending loads and this factor
is probably responsible for the majority of inboard shafting failures. Therefore,
(A)the avoidance of misalignment is mainly for the minimization of outboard shafting failure.
(B)the misalignment has no influence on the loads applied on the outboard shafting.
(C)most of the inboard shafting failures could be attributed to the misalignment in shafting
systems .
(D)the misalignment should be artificially introduced during the sea trial.
34.For a seawater cooled condenser in a steam turbine power plant, which is the correct
statement regarding the seawater temperature and the performances of condenser?
(A)Low seawater temperature permits high vacuum of condenser.
(B)Low seawater temperature permits high steam saturated temperature in condenser.
(C)Low seawater temperature permits high steam dryness in condenser.
(D)High seawater temperature permits high moisture rate of steam in condenser.
35.The principal reason for turbocharging is to increase the power output of an engine of given
size and speed, by enabling the cylinders to be charged with air at an elevated pressure and, therefore, at a higher density than air at atmospheric pressure. What is the main
purpose to use a turbocharger?
(A)To elevate the density of air in order to decrease the pressure in cylinder.
(B)To elevate the pressure of air in order to decrease the density in cylinder.
(C)To improve the power output of an engine of given size and speed by increasing the
compressed air intake temperature.
(D)To improve the power output of an engine of given size and speed by increasing the
density of charged air.
36.The main function of the intercooler of a multistage air compressor is .
(A)to increase the enthalpy of working fluids
(B)to increase the entropy of working fluids
(C)to reduce the specific volume of working fluids
(D)to increase the internal energy of working fluids
38.Fuel oils vary widely in quality and often contain significant amounts of sulfur. Please select
a following procedure that can form aquatic sulfuric acid in the exhaust gas path.
(A)Vaporization
(B)Sublimation
(C)Melting
(D)Condensation
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