Proper balancing of all moving engine parts is essential at a high engine speed - English General - NSC Mechanical Technology: Automotive - Question 6 - 2019 - Paper 1
Question 6
Proper balancing of all moving engine parts is essential at a high engine speed. Answer the questions that follow.
6.1.1 State TWO methods to balance the engine cran... show full transcript
Worked Solution & Example Answer:Proper balancing of all moving engine parts is essential at a high engine speed - English General - NSC Mechanical Technology: Automotive - Question 6 - 2019 - Paper 1
Step 1
State TWO methods to balance the engine crankshaft.
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Answer
Static balance: Achieved by fitting balance mass pieces to the crank webs or by removing metal from the crank.
Dynamic balance: Involves removing metal from certain parts of the crank webs.
Step 2
Briefly explain how the balancing is done using EACH of the methods in QUESTION 6.1.1.
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Answer
In static balancing, balance masses are added to or subtracted from areas where unbalance exists until the assembly remains at rest when placed on a horizontal surface. This ensures that the weight is evenly distributed.
In dynamic balancing, the crankshaft is rotated at various speeds to identify the points of unbalance. Adjustments are made by adding or removing material from specific locations, thus maintaining equilibrium during motion.
Step 3
State TWO factors that cause vibration in an internal combustion engine.
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Answer
Mechanical unbalance: Caused by unbalanced moving parts.
Power unbalance: Resulting from uneven pressure on the pistons and crankshaft.
Step 4
State TWO factors that will determine the firing order in an internal combustion engine.
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Answer
The position of the cranks on the crankshaft.
The arrangement of the cams on the camshaft.
Step 5
Explain the function of a vibration damper in an internal combustion engine.
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Answer
A vibration damper is a mass fitted to the crankshaft opposite to the flywheel, designed to counteract torsional vibrations of the crankshaft. This helps to enhance the engine's stability and prolongs component life by reducing the amplitude of the vibrations.
Step 6
Identify the type of supercharger shown in FIGURE 6.4.
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Answer
The type of supercharger shown in FIGURE 6.4 is a centrifugal type.
Step 7
Label parts A-D of the supercharger above.
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Answer
A: Air inlet port
B: Air outlet port
C: Rotor (impeller)
D: Vane (fins)
Step 8
State TWO advantages of a motor vehicle fitted with a supercharger.
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Answer
More power: More power is developed compared to a similar engine without a supercharger.
Economical output: An engine with a supercharger is generally more economical per given kilowatt output.
Step 9
Explain how a turbocharger on an internal combustion engine operates.
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Answer
The turbocharger operates by routing exhaust gases from the engine to the turbine wheel, enabling it to spin at high speeds. The turbine wheel is connected to a compressor wheel that draws in ambient air and compresses it before sending it into the engine. This results in a denser air charge, ultimately increasing the engine's efficiency and performance.
Step 10
State TWO disadvantages of turbochargers when compared with superchargers.
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Answer
Lag issues: Turbochargers can suffer from lag due to the time it takes to spool up to an effective speed.
Lubrication requirement: Turbochargers require adequate lubrication and may suffer from reduced air density as altitude increases.
Step 11
Explain the effect of high altitude on the performance of an internal combustion engine.
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Answer
At high altitudes, the air density decreases, resulting in reduced oxygen availability for combustion. This can lead to a decrease in engine power output and efficiency, as the engine is unable to draw in sufficient air to mix with fuel for optimal combustion.
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