Questions and Answers
What type of lube oil pump is typically used in small marine engines?
What is the purpose of telescopic pipes in a large slow-speed main propulsion diesel engine?
What is a potential consequence of excessive axial thickness in a piston ring?
Which type of wear on a cylinder liner is considered adhesive wear?
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What is the primary function of relief valves on cylinder heads of marine diesel engines?
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What factor does the operation of a pulse pressure turbocharger rely on?
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Which of these factors contribute to the penetration of fuel droplets during injection?
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How does increasing the storage temperature affect catalytic fines?
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Which of the following directly contributes to the cracking of a piston crown?
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What is the primary function of the overlay layer in a thin shell bearing?
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What does the NLGI number of grease primarily indicate?
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Why are precision insert bearings widely used in modern diesel engines for main and connecting rod bearings?
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What is the primary function of load sensing devices in diesel engines driving alternators?
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Which of the following statements about cylinder oil consumption is FALSE?
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Which of the following bearing types is MOST commonly used for main and connecting rod bearings in modern diesel engines?
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In a uniflow scavenged marine 2-stroke diesel engine, how are the scavenge ports in the cylinder liner machined?
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What is the purpose of cooling supercharged air in an engine?
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Which material is commonly used for intake valves in diesel engines?
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Why must turbocharger bearings be renewed periodically?
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What type of compressor is typically used in modern marine turbochargers?
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What is a significant disadvantage of using water as a cooling medium for pistons?
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What is the primary function of thrust bearings in an engine?
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In comparison to exhaust valves, which characteristic makes intake valves less susceptible to wear?
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Which design feature contributes to the complexity of piston designs compared to using water as a cooling medium?
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Study Notes
Turbocharging
- Supercharged air is cooled to increase its density and keep peak temperature and exhaust gas temperature within limits.
- This cooling prevents moisture from entering the engine.
Bearings
- Piston pin bushing is an example of a solid bearing.
- Turbocharger bearings must be renewed after a preset number of hours, regardless of condition, due to cyclic loading and metal fatigue.
Valves
- Intake valves in diesel engines can be made from low-alloy steels because they are less affected by corrosive exhaust gases.
- Exhaust valves are more prone to wear and require more durable materials.
Turbochargers
- Modern marine turbochargers use radial flow compressors.
Cooling Systems
- Water as a cooling medium for pistons has disadvantages, including chemical treatment requirements, higher thermal stresses, and more complicated piston design.
Fuel Injection
- Factors affecting penetration of fuel droplets during injection include quality of atomization, injection temperature, and scavenge air pressure.
Lube Oil Systems
- Lube oil pumps in small marine engines are usually positive displacement type.
- Telescopic pipes to the piston are designed to prevent contamination of lube oil by water.
- Excessive axial thickness of a piston ring can lead to difficulty in forming an oil wedge.
Cylinder Liners
- Scuffing is an adhesive type wear of a cylinder liner.
- Cylinder heads are provided with relief valves to relieve excessive pressure within the combustion chamber.
Turbocharger Operation
- Pulse pressure turbochargers work by creating pressure pulses in the exhaust system.
Piston Crowns
- Cracking of piston crowns can be caused by deposits in cooling spaces, impingement of fuel due to faulty injection, or insufficient piston cooling oil flow.
Grease
- The NLGI number of grease indicates its consistency, i.e., how fluid or non-fluid it is.
Bearings (continued)
- The overlay of a thin shell bearing gives it its fatigue strength.
- Precision insert bearings are widely used for main and connecting rod bearings of modern diesel engines.
Cylinder Oils
- Fuel oil sulfur level is an important criterion for choosing the TBN level of cylinder oil.
- Excessive cylinder oil feed can lead to harmful deposits in piston top land area.
Speed Control
- Load sensing devices ensure prompt correction of speed of diesel engines driving alternators without massive fluctuations.
Scavenging
- In uniflow scavenged marine 2-stroke diesel engines, scavenge ports in a cylinder liner are machined only for a part of the circumference, at an angle almost tangential to the circumference of the liner.
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Description
This quiz covers turbocharging, bearings, and valves in diesel engines, including their functions and maintenance.