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Questions and Answers
What type of lube oil pump is typically used in small marine engines?
What type of lube oil pump is typically used in small marine engines?
- Positive displacement type (correct)
- Centrifugal type
- Diaphragm type
- Electrically driven
What is the purpose of telescopic pipes in a large slow-speed main propulsion diesel engine?
What is the purpose of telescopic pipes in a large slow-speed main propulsion diesel engine?
- Prevent lube oil contamination of the cooling water
- Cool the lube oil
- Prevent water contamination of the lube oil (correct)
- Reduce crankcase pressure
What is a potential consequence of excessive axial thickness in a piston ring?
What is a potential consequence of excessive axial thickness in a piston ring?
- Difficulty in forming a proper oil wedge (correct)
- Twisting of the ring in its groove
- Excessive oil scraping from the cylinder liner
- Increased wear on the cylinder liner
Which type of wear on a cylinder liner is considered adhesive wear?
Which type of wear on a cylinder liner is considered adhesive wear?
What is the primary function of relief valves on cylinder heads of marine diesel engines?
What is the primary function of relief valves on cylinder heads of marine diesel engines?
What factor does the operation of a pulse pressure turbocharger rely on?
What factor does the operation of a pulse pressure turbocharger rely on?
Which of these factors contribute to the penetration of fuel droplets during injection?
Which of these factors contribute to the penetration of fuel droplets during injection?
How does increasing the storage temperature affect catalytic fines?
How does increasing the storage temperature affect catalytic fines?
Which of the following directly contributes to the cracking of a piston crown?
Which of the following directly contributes to the cracking of a piston crown?
What is the primary function of the overlay layer in a thin shell bearing?
What is the primary function of the overlay layer in a thin shell bearing?
What does the NLGI number of grease primarily indicate?
What does the NLGI number of grease primarily indicate?
Why are precision insert bearings widely used in modern diesel engines for main and connecting rod bearings?
Why are precision insert bearings widely used in modern diesel engines for main and connecting rod bearings?
What is the primary function of load sensing devices in diesel engines driving alternators?
What is the primary function of load sensing devices in diesel engines driving alternators?
Which of the following statements about cylinder oil consumption is FALSE?
Which of the following statements about cylinder oil consumption is FALSE?
Which of the following bearing types is MOST commonly used for main and connecting rod bearings in modern diesel engines?
Which of the following bearing types is MOST commonly used for main and connecting rod bearings in modern diesel engines?
In a uniflow scavenged marine 2-stroke diesel engine, how are the scavenge ports in the cylinder liner machined?
In a uniflow scavenged marine 2-stroke diesel engine, how are the scavenge ports in the cylinder liner machined?
What is the purpose of cooling supercharged air in an engine?
What is the purpose of cooling supercharged air in an engine?
Which material is commonly used for intake valves in diesel engines?
Which material is commonly used for intake valves in diesel engines?
Why must turbocharger bearings be renewed periodically?
Why must turbocharger bearings be renewed periodically?
What type of compressor is typically used in modern marine turbochargers?
What type of compressor is typically used in modern marine turbochargers?
What is a significant disadvantage of using water as a cooling medium for pistons?
What is a significant disadvantage of using water as a cooling medium for pistons?
What is the primary function of thrust bearings in an engine?
What is the primary function of thrust bearings in an engine?
In comparison to exhaust valves, which characteristic makes intake valves less susceptible to wear?
In comparison to exhaust valves, which characteristic makes intake valves less susceptible to wear?
Which design feature contributes to the complexity of piston designs compared to using water as a cooling medium?
Which design feature contributes to the complexity of piston designs compared to using water as a cooling medium?
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.
