Thermal Engineering - I

Thermal Engineering - I - Objective Questions

• Renewable Energy Sources: Petrol, forest (wood), sunlight, water, wind, tidal energy, geothermal energy, biomass, and forests are renewable energy sources. Coal, natural gas, and petroleum are not.
• Highest Calorific Value Fuel: Methane has the highest calorific value compared to petrol, LPG, and hydrogen.
• Biogas Main Component: Methane is the main component of biogas, along with carbon dioxide.
• Non-renewable Energy Source: Petroleum is a non-renewable energy source. Examples include coal and natural gas.
• First Atomic Station: The first atomic power station was started in Kalpakkam.
• Nuclear Fuel: Uranium-235 is the most common nuclear fuel used globally.
• Fossil Fuels: Coal, oil, and natural gas are fossil fuels.
• Unit of Energy: The SI unit of energy is the Joule.
• Renewable vs. Non-renewable Energy Sources: Solar energy, hydropower, and biomass energy are renewable sources; whereas, geothermal energy is sometimes considered non-renewable depending on the rate of replenishment.
• Non-renewable Resources: Coal is a non-renewable resource.
• Biogas Production Conditions: Biogas is produced in the presence of anaerobic microorganisms.
• Solar Energy Source: Solar energy is produced through a chemical reaction (not combustion).
• Non-renewable Resource: Coal is a non-renewable resource.
• Renewable Resources: Examples of renewable resources are wind energy. solar energy, and hydro-electricity.
• Non-Renewable Resources: Natural gas and coal are non-renewable resources.
• Conditions for Biogas Production: Biogas production needs anaerobic microorganisms and the absence of oxygen.
• Solar Energy Process: Solar energy creation happens through nuclear fusion reactions (not combustion).
• Non-renewable Energy Source: Fossil fuels such as coal, oil, and natural gas are non-renewable sources.
• Conventional Energy Generation: A conventional method of generating electrical energy is thermal power.
• Nuclear Reactor Material: Heavy water (D₂O) in a nuclear reactor acts as a moderator.

Four-Stroke Engine Working Cycle

• Working Cycle Duration: A four-stroke engine's working cycle is completed in four revolutions of the crankshaft.
• Thermodynamic Cycle for Petrol Engine: The petrol engine operates on the Otto cycle.
• Diesel Engine Compression Ratio: Diesel engines generally have compression ratios ranging from 15 to 22.
• Diesel Engine Valves: A diesel engine usually has two valves (inlet and outlet).
• Two-Stroke Engine Thermal Efficiency: The thermal efficiency of a two-stroke engine is less than that of a four-stroke engine.

Two-Stroke Engine

• Power Stroke Ratio: The two-stroke engine delivers power twice for every revolution of the crankshaft.
• Engine Efficiency vs. Petrol Use: Using petrol in a diesel engine reduces power and efficiency, and increases the chances of knocking.

Petrol Engine Operation

• Petrol Engine Cycle: A petrol engine operates on a constant volume cycle.

Carburetor Function

• Carburetor Components: A carburetor supplies petrol, air, and lubricating oil to the engine.
• Carburetor Purpose: The carburetor delivers petrol and air in the correct ratio, required by the engine.

Diesel Engine Suction

• Diesel Engine Intake: In a diesel engine, the suction contains only air, not fuel.

Knocking

• Knocking Cause: Increased compression ratio and wall temperature can cause knocking, a hammering sound coming from the engine. The speed of the engine can also cause it, along with decreased compression.

Octane Number

• Octane Number Measurement: Octane number measures the knocking tendency of petrol.
• Petrol Engine Component: The ignition coil in a vehicle transforms the ac currents to high-voltage dc currents.

Magneto Ignition System

• Components: A magneto ignition system includes components such as a battery, induction coil, and condenser.
• Governing Method: The diesel engine speed is maintained by controlling its fuel supply in response to changing loads.

Air Compressor Types

• Rotary Compressor Use: Rotary compressors are better suited for applications needing smaller amounts of air at higher pressure rather than larger volumes at lower pressures.
• Rotary Compressor Use Cases: Air compressors are best used for applications requiring higher pressures or smaller quantities, or low pressures for larger quantities.
• Reciprocating Compressor Operation: A reciprocating air compressor employs pistons to compress the air.

Refrigeration Unit

• Refrigeration Capacity: One ton of refrigeration is equivalent to 210 kJ/min of cooling (melting ice).
• Refrigeration Cycle: Cooling is best achieved by converting water into ice in 24 hours.

Air Standard Cycle

• Otto and Diesel Cycles: The Otto and Diesel cycles, used as theoretical models for combustion engines, involve compression, combustion, and expansion stages.

Thermal Efficiency

• Compression Ratio Effect: Thermal efficiency of Otto cycle and Diesel cycle increases proportionally with increase in compression ratio. This principle is applicable when heat addition is kept constant.

Test your knowledge on renewable and non-renewable energy sources, including their characteristics, uses, and calorific values. This quiz covers essential concepts in thermal engineering and nuclear energy, helping you understand the differences between various energy types.