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In a centrifugal compressor, the diffuser vanes work to:

A - Accelerate the flow of gas into the eye of the impeller B - Increase gas pressure between the impeller outlet and the volute casing C - Increase gas pressure just before it leaves the volute casing of the compressor D - Reverse the direction of flow as the gas leaves the impeller, reducing the pressure Correct Answer(s): B Question 10: Elevating the output pressures of centrifugal compressors by multi-staging means that:

A - The diffuser vanes are placed at both the inlet and outlet of an impeller B - The gas is compressed in steps as it passes progressively through several impellers mounted on a common shaft C - A low-pressure compressor discharges into the suction of a high-pressure compressor D - Several sets of diffusers are placed at the outlet of a single impeller Correct Answer(s): B Question 1:

In an axial compressor, when the gas passes through the fixed blades, its pressure is further increased by conversion of:

A - Velocity B - Suction C - Discharge rate D - Volume Correct Answer(s): A Question 2:

In an axial compressor, a stage consists of a/an:

A - Set of intake and a discharge valves B - Pair of moving and fixed blade rows C - Seal and a fixed blade row D - Impeller shaft and a stator Correct Answer(s): B Question 3:

The two types of thrust bearings used in axial compressors are designed to:

A - Absorb the axial thrust that is directed toward the inlet end of the rotor B - Absorb the axial thrust that is directed toward the discharge end of the rotor C - Align the stator with the impellers D - Reduce corrosion of the compressor blades Correct Answer(s): A Question 4: Centrifugal compressors do not require internal lubrication.

A - True B - False Correct Answer(s): A Question 5:

By definition, a dynamic compressor involves:

A - The continuous flow of a gas into and out of a reciprocating cylinder B - An intermittent flow of a gas from a low velocity to a high-pressure area C - The continuous flow of a gas with the conversion of velocity energy into pressure energy D - Trapping a set volume of a gas inside a space and then forcing it out at a higher pressure Correct Answer(s): C Question 6: In an axial compressor, the longest blades on the stator are located at the:

A - Middle B - Outlet end C - Casing D - Inlet end Correct Answer(s): D

Question 7: Centrifugal compressors have the disadvantage of:

A - Requiring internal lubrication B - Being mechanically complex C - Having lower efficiencies compared to positive displacement compressors D - Being subject to corrosion and erosion to a greater extent than axial compressors Correct Answer(s): C Question 8:

Centrifugal compressors have the disadvantage of:

A - Not being well suited for low capacity work B - Requiring internal lubrication C - Being mechanically complex D - Having high maintenance requirements Correct Answer(s): A Question 9:

Labyrinths and carbon rings are devices commonly used on centrifugal compressors and provide the same function as:

A - Inlet guide vanes B - Stator blade adjusters C - Mechanical seals D - Thrust bearings Correct Answer(s): C Question 10:

The thrust that is produced on the rotor of an axial compressor:

A - Can be overcome by installing a dummy piston on the compressor shaft B - Is an insignificant factor in compressor design C - Is balanced by the shape of the blades D - Results in a force that tends to push the rotor toward the discharge end Correct Answer(s): A Question 1: The impeller of a centrifugal compressor can be equipped with vanes at the eye shaped in such a way:

A - That allows for the control of the capacity of the unit B - That the operating characteristics of the compressor can be adjusted C - That the axial thrust which is directed toward the inlet end of the impeller is absorbed D - To provide shockless entry to the impeller Correct Answer(s): D Question 2:

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