MDE Unit 1 four strokes Quiz

MDE 1 Q1 Intake stroke

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4. Air-Fuel Mixture in Intake Stroke

Question: What is drawn into the cylinder during the intake stroke in a marine diesel engine?

A) A mixture of air and fuel

D) Exhaust gases

B) Pure fuel

C) Pure air

Correct Answer: C) Pure air
Explanation: In a diesel engine, only pure air is drawn into the cylinder during the intake stroke. The fuel is injected directly into the compressed air at a later stage, during the power stroke. This is different from gasoline engines, where a mixture of air and fuel is drawn in during the intake stroke.

Correct Answer: C) Pure air
Explanation: In a diesel engine, only pure air is drawn into the cylinder during the intake stroke. The fuel is injected directly into the compressed air at a later stage, during the power stroke. This is different from gasoline engines, where a mixture of air and fuel is drawn in during the intake stroke.

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5. Timing of the Intake Stroke

Question: When does the intake stroke begin in the four-stroke cycle of a marine diesel engine?

C) Immediately after the exhaust stroke

A) Immediately after the compression stroke

B) Immediately after the power stroke

D) Immediately after the intake valve closes

Correct Answer: C) Immediately after the exhaust stroke
Explanation: The intake stroke begins right after the exhaust stroke. As the exhaust valve closes, the intake valve opens, allowing fresh air to be drawn into the cylinder as the piston moves down. This prepares the cylinder for the next cycle of compression and combustion.

Correct Answer: C) Immediately after the exhaust stroke
Explanation: The intake stroke begins right after the exhaust stroke. As the exhaust valve closes, the intake valve opens, allowing fresh air to be drawn into the cylinder as the piston moves down. This prepares the cylinder for the next cycle of compression and combustion.

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3. Piston Movement in Intake Stroke

Question: In which direction does the piston move during the intake stroke of a four-stroke marine diesel engine?

B) Downward away from the cylinder head

A) Upward toward the cylinder head

C) Remains stationary

D) Moves sideways within the cylinder

Correct Answer: B) Downward away from the cylinder head
Explanation: The piston moves downward during the intake stroke, increasing the volume inside the cylinder and reducing the pressure. This creates a partial vacuum that helps draw air into the cylinder through the open intake valve.

Correct Answer: B) Downward away from the cylinder head
Explanation: The piston moves downward during the intake stroke, increasing the volume inside the cylinder and reducing the pressure. This creates a partial vacuum that helps draw air into the cylinder through the open intake valve.

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6. Pressure in the Cylinder During Intake

Question: What happens to the pressure inside the cylinder during the intake stroke of a four-stroke marine diesel engine?

B) It decreases slightly

A) It increases significantly

C) It remains constant

D) It becomes higher than the atmospheric pressure

Correct Answer: B) It decreases slightly
Explanation: As the piston moves downward during the intake stroke, the volume of the cylinder increases, causing a slight decrease in pressure. This reduced pressure helps in drawing air into the cylinder through the open intake valve.

Correct Answer: B) It decreases slightly
Explanation: As the piston moves downward during the intake stroke, the volume of the cylinder increases, causing a slight decrease in pressure. This reduced pressure helps in drawing air into the cylinder through the open intake valve.

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7. Significance of the Intake Stroke

Question: Why is the intake stroke crucial for the operation of a four-stroke marine diesel engine?

D) It determines the engine’s fuel efficiency

C) It controls the engine speed

A) It initiates the ignition process

B) It ensures the cylinder is filled with a fresh charge of air for combustion

Correct Answer: B) It ensures the cylinder is filled with a fresh charge of air for combustion
Explanation: The intake stroke is vital because it fills the cylinder with fresh air, which is necessary for the combustion process. Without sufficient air, the fuel cannot burn efficiently, leading to poor engine performance and increased emissions.

Correct Answer: B) It ensures the cylinder is filled with a fresh charge of air for combustion
Explanation: The intake stroke is vital because it fills the cylinder with fresh air, which is necessary for the combustion process. Without sufficient air, the fuel cannot burn efficiently, leading to poor engine performance and increased emissions.

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2. Valve Operation During Intake Stroke

Question: During the intake stroke of a four-stroke marine diesel engine, which valve is open?

C) Both intake and exhaust valves

A) Exhaust valve

B) Intake valve

D) Neither intake nor exhaust valve

Correct Answer: B) Intake valve
Explanation: The intake valve opens during the intake stroke to allow fresh air to enter the cylinder. The exhaust valve remains closed to prevent the escape of the air being drawn in. This ensures that the cylinder is filled with the maximum amount of air needed for efficient combustion.

Correct Answer: B) Intake valve
Explanation: The intake valve opens during the intake stroke to allow fresh air to enter the cylinder. The exhaust valve remains closed to prevent the escape of the air being drawn in. This ensures that the cylinder is filled with the maximum amount of air needed for efficient combustion.

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1. Purpose of the Intake Stroke

Question: What is the primary purpose of the intake stroke in a four-stroke marine diesel engine?

D) To expel exhaust gases from the cylinder

A) To compress the air-fuel mixture

B) To ignite the air-fuel mixture

C) To draw fresh air into the cylinder

Correct Answer: C) To draw fresh air into the cylinder
Explanation: During the intake stroke, the intake valve opens, and the piston moves downward, creating a vacuum that draws fresh air into the cylinder. This fresh air is essential for the subsequent combustion process when fuel is injected into the cylinder and ignited.

Correct Answer: C) To draw fresh air into the cylinder
Explanation: During the intake stroke, the intake valve opens, and the piston moves downward, creating a vacuum that draws fresh air into the cylinder. This fresh air is essential for the subsequent combustion process when fuel is injected into the cylinder and ignited.

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8. Intake Stroke in Diesel vs. Gasoline Engines

Question: How does the intake stroke in a marine diesel engine differ from that in a gasoline engine?

A) Diesel engines intake pure air, while gasoline engines intake an air-fuel mixture

B) Diesel engines intake an air-fuel mixture, while gasoline engines intake pure air

C) Both engines intake an air-fuel mixture

D) Both engines intake pure air

Correct Answer: A) Diesel engines intake pure air, while gasoline engines intake an air-fuel mixture
Explanation: In diesel engines, the intake stroke draws in only air, which is then compressed and heated before fuel is injected. In contrast, gasoline engines mix air with fuel before it enters the cylinder during the intake stroke. This difference is a key characteristic that distinguishes the operation of diesel and gasoline engines.

Correct Answer: A) Diesel engines intake pure air, while gasoline engines intake an air-fuel mixture
Explanation: In diesel engines, the intake stroke draws in only air, which is then compressed and heated before fuel is injected. In contrast, gasoline engines mix air with fuel before it enters the cylinder during the intake stroke. This difference is a key characteristic that distinguishes the operation of diesel and gasoline engines.

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MDE 1 Q1 Compression Stroke

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6. Compression Ratio in Diesel Engines

Question: Why is the compression ratio typically higher in diesel engines compared to gasoline engines?

B) To improve fuel atomization

D) To reduce engine noise

A) To increase engine speed

C) To ensure the air is hot enough to ignite the fuel

Answer: C) To ensure the air is hot enough to ignite the fuel
Explanation: Diesel engines require a higher compression ratio to achieve the necessary air temperature for spontaneous ignition of the injected fuel. The higher compression ratio leads to a more efficient combustion process, which is a key characteristic of diesel engines.

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5. Timing of Fuel Injection

Question: When is fuel typically injected into the cylinder of a marine diesel engine?

D) During the exhaust stroke

C) At the end of the compression stroke

B) At the beginning of the compression stroke

A) During the intake stroke

Answer: C) At the end of the compression stroke
Explanation: Fuel is injected at the end of the compression stroke when the air inside the cylinder is at its highest pressure and temperature. This timing ensures that the fuel ignites efficiently, leading to a powerful combustion process during the power stroke.

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1. Purpose of the Compression Stroke

Question: What is the primary purpose of the compression stroke in a four-stroke marine diesel engine?

B) To ignite the air-fuel mixture

D) To draw fresh air into the cylinder

C) To compress the air in the cylinder

A) To expel exhaust gases from the cylinder

Answer: C) To compress the air in the cylinder
Explanation: During the compression stroke, the piston moves upward, compressing the air inside the cylinder. This compression increases the air temperature, making it hot enough to ignite the fuel when it is injected during the power stroke.

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2. Valve Operation During Compression Stroke

Question: During the compression stroke of a four-stroke marine diesel engine, which valves are closed?

A) Both intake and exhaust valves

B) Intake valve only

D) Both intake and exhaust valves are open

C) Exhaust valve only

Answer: A) Both intake and exhaust valves
Explanation: Both the intake and exhaust valves remain closed during the compression stroke to ensure that the air inside the cylinder is fully compressed. This helps in achieving the high pressure and temperature needed for efficient combustion.

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3. Piston Movement in Compression Stroke

Question: In which direction does the piston move during the compression stroke of a four-stroke marine diesel engine?

D) Moves sideways within the cylinder

B) Upward toward the cylinder head

A) Downward away from the cylinder head

C) Remains stationary

Answer: B) Upward toward the cylinder head
Explanation: The piston moves upward during the compression stroke, reducing the volume inside the cylinder and increasing the pressure and temperature of the air. This compression is essential for the efficient ignition of the fuel.

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8. Common Issues During Compression Stroke

Question: What could be a possible cause of reduced compression in a marine diesel engine?

B) Clogged air filters

C) Worn piston rings or cylinder liner

A) Faulty fuel injectors

D) Low coolant level

Answer: C) Worn piston rings or cylinder liner
Explanation: Worn piston rings or a damaged cylinder liner can lead to a loss of compression, as they allow air to escape from the cylinder during the compression stroke. This reduces the pressure and temperature of the compressed air, leading to inefficient combustion and lower engine performance.

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1. Purpose of the Compression Stroke

Question: What is the primary purpose of the compression stroke in a four-stroke marine diesel engine?

A) To expel exhaust gases from the cylinder

D) To draw fresh air into the cylinder

C) To compress the air in the cylinder

B) To ignite the air-fuel mixture

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6. Compression Ratio in Diesel Engines

Question: Why is the compression ratio typically higher in diesel engines compared to gasoline engines?

C) To ensure the air is hot enough to ignite the fuel

D) To reduce engine noise

A) To increase engine speed

B) To improve fuel atomization

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4. Effect on Air Temperature During Compression Stroke

Question: What happens to the temperature of the air inside the cylinder during the compression stroke in a marine diesel engine?

A) It decreases

B) It remains the same

D) It fluctuates

C) It increases

Answer: C) It increases
Explanation: As the air is compressed during the compression stroke, its temperature increases significantly. This rise in temperature is crucial because it allows the fuel to ignite spontaneously when injected into the compressed air.

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4. Effect on Air Temperature During Compression Stroke

Question: What happens to the temperature of the air inside the cylinder during the compression stroke in a marine diesel engine?

B) It remains the same

D) It fluctuates

C) It increases

A) It decreases

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2. Valve Operation During Compression Stroke

Question: During the compression stroke of a four-stroke marine diesel engine, which valves are closed?

D) Both intake and exhaust valves are open

C) Exhaust valve only

A) Both intake and exhaust valves

B) Intake valve only

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5. Timing of Fuel Injection

Question: When is fuel typically injected into the cylinder of a marine diesel engine?

D) During the exhaust stroke

C) At the end of the compression stroke

A) During the intake stroke

B) At the beginning of the compression stroke

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8. Common Issues During Compression Stroke

Question: What could be a possible cause of reduced compression in a marine diesel engine?

D) Low coolant level

B) Clogged air filters

A) Faulty fuel injectors

C) Worn piston rings or cylinder liner

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7. Role of the Compression Stroke in Power Output

Question: How does the compression stroke affect the power output of a marine diesel engine?

C) It prepares the air for combustion, indirectly contributing to power output

A) It directly increases the power output by compressing the fuel

D) It has no effect on power output

B) It reduces power output by increasing engine resistance

Answer: C) It prepares the air for combustion, indirectly contributing to power output
Explanation: The compression stroke doesn’t directly produce power, but by compressing the air, it prepares the cylinder for efficient combustion. The high-pressure, high-temperature air ensures that the fuel burns more completely, leading to higher power output during the power stroke.

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3. Piston Movement in Compression Stroke

Question: In which direction does the piston move during the compression stroke of a four-stroke marine diesel engine?

D) Moves sideways within the cylinder

A) Downward away from the cylinder head

B) Upward toward the cylinder head

C) Remains stationary

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7. Role of the Compression Stroke in Power Output

Question: How does the compression stroke affect the power output of a marine diesel engine?

B) It reduces power output by increasing engine resistance

D) It has no effect on power output

C) It prepares the air for combustion, indirectly contributing to power output

A) It directly increases the power output by compressing the fuel

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MDE 1 Power Stroke

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5. Energy Conversion During Power Stroke

Question: What type of energy is primarily converted into mechanical work during the power stroke of a marine diesel engine?

C) Kinetic energy from the moving piston

A) Chemical energy from the fuel

B) Electrical energy from the battery

D) Potential energy from the crankshaft

Answer: A) Chemical energy from the fuel
Explanation: The chemical energy stored in the fuel is converted into heat energy through combustion. This heat energy increases the pressure in the cylinder, which is then converted into mechanical work as it forces the piston downward during the power stroke.

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1. Purpose of the Power Stroke

Question: What is the primary purpose of the power stroke in a four-stroke marine diesel engine?

C) To convert the energy from combustion into mechanical work

A) To compress the air-fuel mixture

B) To draw fresh air into the cylinder

D) To expel exhaust gases from the cylinder

Answer: C) To convert the energy from combustion into mechanical work
Explanation: The power stroke is the phase in the engine cycle where the combustion of fuel generates high pressure, forcing the piston downward. This movement converts the energy from the combustion into mechanical work, which drives the engine and propels the vessel.

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3. Valve Operation During Power Stroke

Question: Which valves are open during the power stroke of a four-stroke marine diesel engine?

C) Only the exhaust valve

A) Both intake and exhaust valves

D) Both valves are closed

B) Only the intake valve

Answer: D) Both valves are closed
Explanation: During the power stroke, both the intake and exhaust valves are closed. This ensures that the force from the combustion is fully applied to the piston, driving it downward without any loss of pressure or energy through the valves.

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4. Combustion Process in Power Stroke

Question: What initiates the power stroke in a four-stroke marine diesel engine?

A) Compression of the air-fuel mixture

C) Spontaneous ignition of the fuel due to high pressure and temperature

D) Opening of the intake valve

B) Ignition of the fuel by a spark plug

Answer: C) Spontaneous ignition of the fuel due to high pressure and temperature
Explanation: In a diesel engine, the fuel spontaneously ignites due to the high pressure and temperature created during the compression stroke. This ignition causes the rapid expansion of gases, initiating the power stroke and pushing the piston downward.

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7. Role of the Power Stroke in Engine Operation

Question: Why is the power stroke considered the most critical stroke in the operation of a four-stroke marine diesel engine?

A) It removes exhaust gases from the cylinder

C) It generates the force needed to produce mechanical work

D) It compresses the air-fuel mixture for combustion

B) It introduces fresh air into the cylinder

Answer: C) It generates the force needed to produce mechanical work
Explanation: The power stroke is crucial because it is the only stroke that generates the force needed to produce mechanical work. This work is what ultimately powers the engine and allows it to drive the vessel.

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8. Temperature Changes During Power Stroke

Question: What happens to the temperature inside the cylinder during the power stroke of a four-stroke marine diesel engine?

B) It remains constant

C) It increases slightly

A) It decreases significantly

D) It starts high and decreases as the piston moves downward

Answer: D) It starts high and decreases as the piston moves downward
Explanation: The temperature inside the cylinder is highest at the beginning of the power stroke due to the combustion of the fuel. As the piston moves downward and the gases expand, the temperature decreases slightly, but it remains much higher than the initial intake temperature.

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6. Timing of the Power Stroke

Question: When does the power stroke occur in the four-stroke cycle of a marine diesel engine?

A) Immediately after the intake stroke

B) Immediately after the exhaust stroke

D) Immediately after the power stroke

C) Immediately after the compression stroke

Answer: C) Immediately after the compression stroke
Explanation: The power stroke occurs right after the compression stroke, where the air-fuel mixture has been fully compressed. At this point, the fuel ignites, causing the power stroke that drives the piston downward.

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2. Piston Movement During Power Stroke

Question: In which direction does the piston move during the power stroke of a four-stroke marine diesel engine?

C) Remains stationary

D) Moves sideways within the cylinder

A) Upward toward the cylinder head

B) Downward away from the cylinder head

Answer: B) Downward away from the cylinder head
Explanation: During the power stroke, the combustion of the fuel-air mixture generates high pressure, pushing the piston downward. This downward movement is crucial as it translates the force from the combustion into rotational energy that powers the engine.

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MDE 1 Q1 Exhuast Stroke

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4. Timing of the Exhaust Stroke

Question: When does the exhaust stroke occur in the four-stroke cycle of a marine diesel engine?

D) Immediately after the exhaust stroke

C) Immediately after the compression stroke

B) Immediately after the power stroke

A) Immediately after the intake stroke

Answer: B) Immediately after the power stroke
Explanation: The exhaust stroke follows the power stroke. After the fuel has been burned and the power stroke has pushed the piston downward, the exhaust stroke occurs to expel the remaining combustion gases from the cylinder.

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8. Exhaust System in Diesel Engines

Question: What is the role of the exhaust system connected to the cylinder during the exhaust stroke?

D) It injects fuel into the cylinder

B) It filters the air entering the cylinder

C) It channels the exhaust gases out of the engine

A) It cools down the intake air

Answer: C) It channels the exhaust gases out of the engine
Explanation: The exhaust system is responsible for channeling the exhaust gases expelled during the exhaust stroke out of the engine. This system typically includes components like the exhaust manifold, muffler, and exhaust pipe, which work together to manage and direct the flow of exhaust gases away from the engine and the vessel.

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3. Piston Movement During Exhaust Stroke

Question: In which direction does the piston move during the exhaust stroke of a four-stroke marine diesel engine?

B) Downward away from the cylinder head

D) Moves sideways within the cylinder

C) Remains stationary

A) Upward toward the cylinder head

Answer: A) Upward toward the cylinder head
Explanation: During the exhaust stroke, the piston moves upward toward the cylinder head, pushing the spent combustion gases out of the cylinder through the open exhaust valve. This upward movement helps to efficiently clear the cylinder of exhaust gases.

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5. Pressure Changes During Exhaust Stroke

Question: What happens to the pressure inside the cylinder during the exhaust stroke of a four-stroke marine diesel engine?

A) It increases significantly

C) It decreases as the piston moves upward

D) It fluctuates randomly

B) It remains constant

Answer: C) It decreases as the piston moves upward
Explanation: As the piston moves upward during the exhaust stroke, the volume of the cylinder decreases, forcing the exhaust gases out through the open exhaust valve. This movement causes a reduction in pressure inside the cylinder as the gases are expelled.

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7. Potential Issues During Exhaust Stroke

Question: What could happen if the exhaust valve fails to open properly during the exhaust stroke of a marine diesel engine?

B) The engine will produce more power

A) The cylinder will overfill with fresh air

C) The combustion gases will remain in the cylinder, causing poor performance

D) The fuel will not ignite during the power stroke

Answer: C) The combustion gases will remain in the cylinder, causing poor performance
Explanation: If the exhaust valve fails to open, the combustion gases will not be expelled from the cylinder. This can lead to poor engine performance, as the remaining exhaust gases will reduce the amount of fresh air that can enter during the next intake stroke, leading to inefficient combustion.

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6. Exhaust Stroke and Engine Efficiency

Question: How does the exhaust stroke impact the overall efficiency of a marine diesel engine?

D) It maintains efficiency by ensuring complete removal of exhaust gases

A) It has no impact on engine efficiency

C) It reduces efficiency by wasting energy

B) It increases efficiency by compressing the air-fuel mixture

Answer: D) It maintains efficiency by ensuring complete removal of exhaust gases
Explanation: The exhaust stroke is crucial for maintaining engine efficiency because it clears the cylinder of exhaust gases. If exhaust gases are not fully expelled, they can dilute the fresh air intake, reducing the efficiency of combustion in the next cycle. Properly expelling the gases ensures that the engine operates efficiently.

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1. Purpose of the Exhaust Stroke

Question: What is the primary purpose of the exhaust stroke in a four-stroke marine diesel engine?

C) To expel combustion gases from the cylinder

D) To ignite the air-fuel mixture

A) To draw fresh air into the cylinder

B) To compress the air-fuel mixture

Answer: C) To expel combustion gases from the cylinder
Explanation: The exhaust stroke is responsible for removing the combustion gases that remain in the cylinder after the power stroke. This expulsion ensures that the cylinder is cleared of exhaust gases, making room for a fresh charge of air during the next intake stroke.

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2. Valve Operation During Exhaust Stroke

Question: During the exhaust stroke of a four-stroke marine diesel engine, which valve is open?

C) Both intake and exhaust valves

D) Neither valve

B) Exhaust valve

A) Intake valve

Answer: B) Exhaust valve
Explanation: The exhaust valve opens during the exhaust stroke to allow the combustion gases to exit the cylinder and be expelled out of the engine through the exhaust system. The intake valve remains closed to prevent any backflow of gases.

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MDE 1 Q2,3

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Factors Influencing Atomization

Question: Which of the following factors influence the atomization of fuel in a marine diesel engine?

A) Fuel temperature and injection pressure

C) Fuel viscosity and piston speed

D) Combustion chamber design and exhaust temperature

B) Engine speed and air-fuel ratio

Answer: A) Fuel temperature and injection pressure
Explanation: Atomization of fuel is primarily influenced by factors such as fuel temperature and injection pressure. Higher injection pressures and optimal fuel temperatures help in breaking the fuel into fine droplets, which improves mixing with air and enhances combustion efficiency.

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Atomization in Fuel Combustion

Question: What is meant by the term "atomization" in the context of fuel combustion in a marine diesel engine?

B) The conversion of fuel into fine droplets to enhance combustion efficiency

A) The process of mixing fuel with air to create a combustible mixture

D) The cooling of fuel before it enters the combustion chamber

C) The compression of fuel to increase its energy density

Answer: B) The conversion of fuel into fine droplets to enhance combustion efficiency
Explanation: Atomization refers to the process of breaking down liquid fuel into fine droplets as it is injected into the combustion chamber. This increases the surface area of the fuel, allowing it to mix more effectively with air and burn more completely, which enhances combustion efficiency and reduces emissions.

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Factors Influencing Penetration

Question: Which of the following factors primarily influence the penetration of fuel in the combustion chamber of a marine diesel engine?

C) Fuel density and exhaust pressure

D) Compression ratio and turbocharger boost

A) Fuel temperature and injector nozzle design

B) Engine speed and intake air temperature

Answer: A) Fuel temperature and injector nozzle design
Explanation: The penetration of fuel into the combustion chamber is mainly influenced by fuel temperature and the design of the injector nozzle. Higher fuel temperatures and optimized nozzle design can improve the penetration of fuel droplets, ensuring better mixing with air and more effective combustion.

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Transfer of Gas Force from Piston Crown to Crankshaft

Question: How is the force generated by the combustion gases transferred from the piston crown to the crankshaft in a four-stroke diesel engine?

B) Directly through the piston rings which transfer force to the crankshaft

A) Through the connecting rod which converts the linear motion of the piston into rotational motion

C) Via the camshaft which then drives the crankshaft

D) Through the exhaust valves which push the crankshaft

Answer: A) Through the connecting rod which converts the linear motion of the piston into rotational motion
Explanation: The force generated by the combustion gases acts on the piston crown and pushes the piston downward. This linear motion of the piston is transferred to the crankshaft through the connecting rod. The connecting rod converts this linear motion into rotational motion, which drives the crankshaft and ultimately powers the engine.

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Compression Ratio in Fuel Combustion

Question: What does the term "compression ratio" refer to in the context of fuel combustion in a marine diesel engine?

B) The ratio of the engine's power output to the fuel consumption rate

D) The ratio of the amount of fuel injected to the amount of air compressed

A) The ratio of the volume of fuel to the volume of air in the combustion chamber

C) The ratio of the maximum to the minimum volume of the combustion chamber during the engine cycle

Answer: C) The ratio of the maximum to the minimum volume of the combustion chamber during the engine cycle
Explanation: The compression ratio is defined as the ratio of the cylinder's volume when the piston is at the bottom of its stroke (maximum volume) to the volume when the piston is at the top of its stroke (minimum volume). A higher compression ratio indicates that the air-fuel mixture is compressed more, leading to higher engine efficiency and power output due to more complete combustion.

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Penetration in Fuel Combustion

Question: What does the term "penetration" refer to in the context of fuel combustion in a marine diesel engine?

C) The process of breaking down fuel into smaller droplets for better combustion

D) The amount of fuel that evaporates before reaching the combustion chamber

B) The distance fuel droplets travel into the combustion chamber before igniting

A) The ability of the fuel to mix with air before combustion

Answer: B) The distance fuel droplets travel into the combustion chamber before igniting
Explanation: Penetration refers to the distance that fuel droplets travel into the combustion chamber after being injected but before they ignite. Proper penetration is essential for ensuring that the fuel mixes well with air and spreads throughout the combustion chamber, allowing for efficient and complete combustion.

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Factors Influencing Compression Ratio

Question: Which of the following factors primarily influence the compression ratio in a marine diesel engine?

A) Cylinder volume and piston design

C) Engine speed and fuel injection timing

D) Air temperature and exhaust manifold design

B) Fuel type and turbocharger pressure

Answer: A) Cylinder volume and piston design
Explanation: The compression ratio in an engine is determined by the ratio of the maximum cylinder volume (when the piston is at the bottom of its stroke) to the minimum cylinder volume (when the piston is at the top of its stroke). This is influenced by factors such as the design of the cylinder and piston, which define the total volume available for compression.

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Components in a Cross-Section of a Four-Stroke Diesel Engine Piston

Question: In a cross-section view of a four-stroke diesel engine piston, which of the following components are typically visible?

B) Camshaft, crankshaft, and connecting rod

A) Piston crown, piston rings, and piston skirt

C) Fuel injector, turbocharger, and intake valve

D) Exhaust valve, rocker arm, and valve spring

Answer: A) Piston crown, piston rings, and piston skirt
Explanation: In a cross-sectional view of a piston, you can typically see the piston crown (the top surface of the piston), the piston rings (which seal the combustion chamber and control oil consumption), and the piston skirt (the lower part of the piston that maintains alignment within the cylinder). Other components such as the camshaft or turbocharger are not visible in a cross-section of the piston itself.

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