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3B2 POWER ENGINEER EXAM PRACTICE EXAM WITH
COMPLETE SOLUTIONS!!
The disadvantages of a gas turbine are:
- High cost of manufacture
- High levels of noise pollution are produced
- Low thermal efficiency
- Requires many auxiliaries to be efficient
A. 1, 2, 3 B. 1, 3, 4 C. 2, 3, 4 D. 1, 2, 4 E. 1, 2, 3, 4 - ANSWER E
The most common process method of refrigeration is: Select one: A. Absorption B. Lithium bromide C. Water vapor D. Vapor compression or mechanical E. Ammonia compression system - ANSWER D
To facilitate the removal of moisture and oil from the compressed air, a/an _____ is installed. Select one:
A. Intercooler B. Oil separator C. Unloader D. Expansion tank E. Aftercooler - ANSWER E
In a two-stage refrigeration system, the 1st stage compressor is also known as a _____ compressor. Select one: A. Booster B. Standby C. Low volume D. Extraction E. Refrigerant - ANSWER A
In the rotary vane compressor: Select one: A. Vanes close to the central hub by centrifugal force B. There is a rotor in the exact center of the casing C. Refrigerant is trapped between the roller and the decreasing volume of the eccentric casing D. The rotor oscillates E. The vanes move in the rotor - ANSWER E
In a gas turbine, there are fewer turbine stages than compressor stages because: Select one: A. Energy can be extracted more efficiently in the turbine B. Turbine blades are bigger so require fewer
Besides reducing NOx, water injection systems Select one: a. stabilize the combustion process, thereby increasing the life of hot section components b. help keep the compressor blading clean c. reduce the gas turbine's thermal efficiency d. decrease the power output - ANSWER C
The pressure at the outlet from the moving blades is the same as the pressure at the inlet to the moving blades in a/an __________ turbine. Select one: A. Topping B. Reaction C. Back pressure D. Impulse E. Extraction - ANSWER D
A condenser shell may be fitted with an expansion joint if the: Select one: A. Expected temperature differentials will be greater than 20°C B. Condenser tubes are U-shaped C. Condenser is of welded construction D. Condenser tubes are expanded into the tube sheets E. Tube sheets are made of Admiralty brass - ANSWER D
Adjustable inlet diffuser vanes on centrifugal air compressors are implemented to: Select one:
A. Change the operating characteristics of the compressor B. Change the direction of the air flow to remove moisture C. Remove foreign particles from the air D. Only reduce the amount of air entering the compressor E. Prevent back or reverse flow of air - ANSWER A
Positive displacement compressor types include:
- Sliding vane
- Axial flow
- Internal gear
- Volute casing
- Rotary screw
- Multi lobe Select one: A. 1, 3, 4, 6 B. 2, 4, 5, 6 C. 1, 3, 5, 6 D. 1, 2, 4, 5 E. 2, 3, 4, 6 - ANSWER C
Reciprocating Compressor valves are usually automatic and open and close by: Select one: A. Action of a poppet valve B. Movement of the piston covering or uncovering ports C. Operation of an air solenoid valve D. A pressure difference E. A camshaft - ANSWER D
evaporator and also by: Select one: A. Increasing the brine concentration B. Regulating the output of the compressor C. Removing refrigerant from the system D. Increasing the level of the receiver E. Regulating the level of the condenser - ANSWER B
The hyperbolic cooling tower has the advantages of:
- Low initial cost
- Low power consumption
- Dependability
- Minimum maintenance Select one: A. 1, 2, 3 B. 2, 3, 4 C. 1, 3, 4 D. 1, 2, 4 E. 1, 2, 3, 4 - ANSWER B
The design of the HRSG in a cogeneration system depends on:
- Thermal requirements
- Mechanical requirements
- Electrical requirements
- Volumetric requirements Select one: A. 1, 2
B. 1, 3
C. 1, 4
D. 2. 3
E. 2, 4 - ANSWER B
In a rotary lobe compressor one lobe is directly driven by the driving mechanism while the other lobe is driven by: Select one: A. Intermeshing with the driven lobe B. A reduction gear C. Means of timing gears D. Speed increasing gears E. A belt - ANSWER C
Small turbines, used to drive auxiliary equipment, are usually lubricated by: Select one: A. Grease nipples B. Oil impregnated bushings C. Ring-oiled bearings D. Self-lubricated sealed bearings E. Hand - ANSWER C
Slugs of liquid carried over from the evaporator in the absorption system cause: Select one: A. Considerable trouble B. No damage C. More damage than in a compression system
B. De-superheated steam C. Low pressure steam D. Hot water E. Turbine exhaust steam - ANSWER E
One disadvantage of a low-side float control is: Select one: A. Liquid slugs could be carried over to the compressor B. The level gets too high in the receiver C. The level in the receiver becomes very difficult to control D. It makes it difficult to install a charging valve E. Unstable regulation - ANSWER E
How does air enter a condenser?
- Air pumps
- Gland leaks
- Carried in with steam
- Leaky flanges Select one: A. 1, 2 B. 3, 4 C. 1, 2, 3 D. 2, 3, 4 E. 1, 2, 3, 4 - ANSWER D
Which of the statements given is not true of liquid receivers: Select one:
A. Liquid receivers compensate for varying volumes or refrigerant circulation at different loads B. The receiver helps keep the condenser drained C. The receiver reduces the amount of effective condenser surface required D. The receiver provides a space to store refrigerant if the expansion valve is closed for draw down E. The receiver is primarily a heat exchange device - ANSWER E
The difference in enthalpy of ammonia as a fluid at saturation conditions at 1165.8 kPa abs and 236.2 kPa abs is found in the: Select one: A. hf column and is 208.9 kJ/kg B. hf and hg columns and is 1311.6 kJ/kg C. hf column and is 114.905 kJ/kg D. hf column and is 0.508788 kJ/kg E. hg column and is 658.519 kJ/kg - ANSWER A
The advantages of gas turbines are:
- Remote operation capability
- Simple compact design
- Quick start time
- High thermal efficiency Select one: A. 1, 2, 3 B. 1, 3, 4 C. 2, 3, 4 D. 1, 2, 4 E. 1, 2, 3, 4 - ANSWER A
E. 1, 2, 3, 4 - ANSWER A
In a package industrial screw compressor, a silicone-based fluid is necessary to cool, lubricate and seal the rotors. This fluid is then removed in a: Select one: A. Air/fluid separator B. Fluid cooler/air cooler C. Moisture separator D. Water/oil separator E. Air filter - ANSWER A
In order to counter the corrosive nature of the condensate produced from burning fuel with high sulphur content, a _____ heat exchanger is installed in the condensing heat recovery systems. Select one: A. Plastic lined B. Mild steel C. High carbon steel D. High alloy steel E. Stainless steel - ANSWER E
Which of the below are true of the Fixed Tube Sheet shell and tube exchanger?
- Has a tube pattern that can fill the shell
- Has tube sheets welded to the shell
- Tube sheets can extend past the shell for bolting up
- The design allows for differences in thermal expansion between the shell and tube bundle
- Allows brush cleaning Select one:
A. 1, 2, 3, 4
B. 2, 3, 4, 5
C. 1, 2, 3, 5
D. 1, 2, 4, 5
E. 1, 2, 3, 4, 5 - ANSWER C
The governor in a diesel engine controls the: Select one: A. Supercharger B. Fuel entering the cylinders C. Scavenging air D. Air/fuel mixture to the cylinder E. Air to the cylinder - ANSWER B
Effective intercooling will reduce weakening of parts due to high temperatures, and reduce possibility of: Select one: A. Compressor explosions B. Water hammer C. Compressor implosions D. Compressor leaks E. Corrosion - ANSWER B
A good method of removing moisture from air before it goes into the air receiver is to: Select one: A. Heat it B. Pressurize it
In a multi stage, reciprocating compressor the highest, pressure stages may be: Select one: A. Remote controlled B. Poppet valve regulated C. Double lobe D. Single acting E. Free piston - ANSWER D
The stop and start system is best employed where: Select one: A. The air demand is constant B. The air demand is low and infrequently demanded C. A large AC motor is used as the driver D. A diesel engine is used as the driver E. Variable speed is used - ANSWER B
Reciprocating compressor connecting rods are constructed of: Select one: A. Cast iron B. Stainless steel C. Forged steel D. Black iron E. Brass - ANSWER C
Water cooled surface condensers may be classified as:
- Radial flow
- Cross flow
- Central flow
- Down flow Select one: A. 1, 2 B. 2, 4 C. 1, 2, 3 D. 1, 3, 4 E. 2, 3, 4 - ANSWER D
The advantages of a dual shaft gas turbine arrangement are:
- Greater flexibility
- It is cheaper
- Smaller starting motors may be used
- High pressures and temperatures may be obtained Select one: A. 1, 2. B. 1, 3. C. 2, 3. D. 2, 4. E. 1, 4. - ANSWER B
The _____ control method can be used when a compressor is driven by a steam engine, a turbine, or an internal combustion engine. Select one: A. Constant speed B. Start and stop
E. 0.577, convergent or convergent-divergent - ANSWER B
Which one of the following cogeneration systems does the following description best describe? "The compressor driven by the gas turbine supplies pressurized combustion air to mix with fuel and burned in the boiler. The steam produced by the boiler is used to drive a steam turbine that is connected to an electrical generator. The exhaust gases from the boiler are then fed to the gas turbine which is connected to a second electrical generator." Select one: A. Back Pressure Turbine B. Waste Heat C. Gas Turbine D. Combined-cycle Steam/Gas Turbine E. Combined-cycle Gas/Steam Turbine - ANSWER D
The purpose of a thrust bearing on a large reaction steam turbine is to:
- Absorb radial thrust on the shaft.
- Keep the rotor in an exact position in the casing.
- Prevent any steam from escaping.
- Absorb any axial thrust on the rotor.
- Support the dummy piston. Select one: A. 1, 2, 3 B. 2, 4, 5 C. 2, 4 D. 3, 5 E. 1, 4 - ANSWER C
Concentric pipe heat exchangers:
Select one: A. Typically use concurrent flows B. Always use a smooth bore annulus C. Are bulky D. Always use consecutive flows E. Are used for low heat duties - ANSWER E
On startup of a large condensing turbine, the cooling water to the oil cooler is turned on: Select one: A. Before the jacking oil pump B. At the same time as the lubricating oil pump C. When the oil reaches normal operating temperatures D. When the jacking oil pump is shut down E. When it is convenient - ANSWER C
On an extraction turbine the extraction pressure is:
a. Not critical b. Varied according to turbine load c. Maintained constant regardless of turbine load d. Proportional to the turbine load e. Reduced if load increases - ANSWER C
Reaction turbine blades (moving):
- Convert the kinetic energy of the steam into mechanical energy
- Convert heat energy into kinetic energy
- Are nozzle shaped
