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QUESTION 6: ENGINES (SPECIFIC) 6.1 Proper balancing of all moving engine parts is essential at a high engine speed - NSC Mechanical Technology Automotive - Question 6 - 2019 - Paper 1
Question 6
QUESTION 6: ENGINES (SPECIFIC) 6.1 Proper balancing of all moving engine parts is essential at a high engine speed. Answer the questions that follow. 6.1.1 State T... show full transcript
Worked Solution & Example Answer:QUESTION 6: ENGINES (SPECIFIC) 6.1 Proper balancing of all moving engine parts is essential at a high engine speed - NSC Mechanical Technology Automotive - Question 6 - 2019 - Paper 1
Step 1
6.1.1 State TWO methods to balance the engine crankshaft.
Answer
To balance the engine crankshaft, the following two methods are commonly used:
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Static Balance: This method involves ensuring that the crankshaft is balanced by adding mass pieces to specific areas of the crank and flywheel.
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Dynamic Balance: This method reduces vibration by removing metal from certain parts of the crank webs, distributing weight evenly.
Step 2
6.1.2 Briefly explain how the balancing is done using EACH of the methods in QUESTION 6.1.1.
Answer
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Static Balancing: The balancing is achieved by attaching additional weight to the crankshaft or removing metal. The goal is to center the weight distribution so that it rotates evenly without creating excess force.
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Dynamic Balancing: This involves measuring vibration during operation and adjusting the crankshaft by removing or repositioning mass on the crankwebs so that vibrations are minimized, ensuring smoother engine operation.
Step 3
6.1.3 State TWO factors that cause vibration in an internal combustion engine.
Answer
Factors that contribute to vibration in an internal combustion engine include:
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Mechanical Unbalance: This occurs when moving parts are not properly balanced, leading to erratic motion.
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Power Unbalance: Uneven pressure on the pistons during combustion can lead to vibrations due to differing forces being exerted on the crankshaft.
Step 4
6.2 State TWO factors that will determine the firing order in an internal combustion engine.
Answer
The firing order in an internal combustion engine can be determined by:
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The Position of the Cranks on the Crankshaft: The arrangement determines the sequence of cylinder firing.
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The Number of Cylinders: The total number of cylinders influences the firing sequence to maintain smooth running.
Step 5
6.3 Explain the function of a vibration damper in an internal combustion engine.
Answer
A vibration damper is a mass fitted to the crankshaft, located opposite the flywheel to counteract the torsional vibrations of the crankshaft. It absorbs and reduces the energy of vibrations caused by the engine’s operation, thereby enhancing the smoothness and longevity of the engine.
Step 6
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Step 8
6.5 State TWO advantages of a motor vehicle fitted with a supercharger.
Answer
Advantages of having a supercharger fitted in a motor vehicle include:
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Increased Power Output: More power is developed compared to vehicles without a supercharger, enhancing performance.
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Enhanced Efficiency: An engine with a supercharger is typically more economical, providing greater energy output for each kilowatt consumed.
Step 9
6.6 Explain how a turbocharger on an internal combustion engine operates.
Answer
The operation of a turbocharger involves routing exhaust gases from the engine to a turbine wheel, which spins at a high speed. As the turbine spins, it turns a common shaft that drives the compressor wheel, pulling in air through the intake. The compressed air is then delivered to the combustion chamber, increasing the engine's efficiency and power.
Step 10
6.7 State TWO disadvantages of turbochargers when compared with superchargers.
Answer
Disadvantages of turbochargers include:
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Lag in Performance: Turbochargers may experience 'turbo lag', where there is a delay in power delivery as the turbo builds pressure.
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Complex Installation and Maintenance: Turbochargers require intricate installation and are often more complex to maintain compared to superchargers.
Step 11
6.8 Explain the effect of high altitude on the performance of an internal combustion engine.
Answer
At high altitudes, the availability of oxygen decreases, which can lead to reduced engine performance. The lower air density results in less oxygen being available for combustion, causing the engine to operate less efficiently, thus limiting its power output compared to sea level conditions.