MDE 1 Q1 Intake stroke 37 12345678 MDE 1 Q1 Intake stroke 1 / 8 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? D) Both engines intake pure air C) Both engines intake an air-fuel mixture B) Diesel engines intake an air-fuel mixture, while gasoline engines intake pure air A) Diesel engines intake pure air, while gasoline engines intake an air-fuel mixture 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. 2 / 8 2. Valve Operation During Intake Stroke Question: During the intake stroke of a four-stroke marine diesel engine, which valve is open? D) Neither intake nor exhaust valve A) Exhaust valve B) Intake valve C) Both intake and exhaust valves 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. 3 / 8 4. Air-Fuel Mixture in Intake Stroke Question: What is drawn into the cylinder during the intake stroke in a marine diesel engine? C) Pure air B) Pure fuel D) Exhaust gases A) A mixture of air and fuel 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. 4 / 8 5. Timing of the Intake Stroke Question: When does the intake stroke begin in the four-stroke cycle of a marine diesel engine? D) Immediately after the intake valve closes B) Immediately after the power stroke C) Immediately after the exhaust stroke A) Immediately after the compression stroke 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. 5 / 8 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? D) It becomes higher than the atmospheric pressure B) It decreases slightly C) It remains constant A) It increases significantly 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. 6 / 8 1. Purpose of the Intake Stroke Question: What is the primary purpose of the intake stroke in a four-stroke marine diesel engine? C) To draw fresh air into the cylinder B) To ignite the air-fuel mixture A) To compress the air-fuel mixture D) To expel exhaust gases from 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. 7 / 8 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? C) Remains stationary B) Downward away from the cylinder head D) Moves sideways within the cylinder A) Upward toward the cylinder head 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. 8 / 8 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 B) It ensures the cylinder is filled with a fresh charge of air for combustion A) It initiates the ignition process 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. Your score is LinkedIn Facebook Twitter VKontakte Revision Notes Next Quiz