Energy Science Unit IV Quiz
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Questions and Answers

What is defined as the amount of heat liberated when unit mass of fuel is burnt completely?

  • Energy Yield
  • Combustion Rate
  • Heat Efficiency
  • Calorific Value (correct)

    • Which of the following fuels is classified as a solid fuel?

  • Natural gas
  • Charcoal (correct)
  • Crude oil
  • Kerosene

    • What type of calorific value includes the heat of condensation of combustion products?

  • Net Energy Value
  • Higher Calorific Value (correct)
  • Lower Calorific Value
  • Specific Heat Capacity

    • Which of the following is considered an artificial or secondary fuel?

    <p>Coke</p> Signup and view all the answers

    Which classification of fuel occurs naturally in the environment?

    <p>Natural fuel</p> Signup and view all the answers

    Which of the following fuels is classified as a liquid fuel?

    <p>Gasoline</p> Signup and view all the answers

    What is the main difference between Higher Calorific Value and Lower Calorific Value?

    <p>HCV includes the heat of condensation, while LCV does not</p> Signup and view all the answers

    Which of the following describes gaseous fuels?

    <p>They are in a gaseous state</p> Signup and view all the answers

    What is the cetane number of a fuel that has the same ignition delay as a mixture of 40% cetane and 60% methyl naphthalene?

    <p>40</p> Signup and view all the answers

    Which of the following statements about cetane number is true?

    <p>A higher cetane number indicates shorter ignition delay.</p> Signup and view all the answers

    What cetane number is generally required for high-speed diesel engines?

    <p>50</p> Signup and view all the answers

    Which of the following is NOT an additive used to improve cetane number?

    <p>Methyl naphthalene</p> Signup and view all the answers

    In cetane number testing, what component is compared with cetane to assess ignition delay?

    <p>Methyl naphthalene</p> Signup and view all the answers

    What causes knocking in an internal combustion engine?

    <p>Spontaneous ignition of the last unburnt portion of charge</p> Signup and view all the answers

    Which order represents the knocking tendency based on gasoline constituents?

    <p>Straight chain paraffins &gt; branched chain paraffins &gt; olefins &gt; aromatics</p> Signup and view all the answers

    What is the purpose of an antiknocking agent added to fuels?

    <p>To mitigate knocking characteristics</p> Signup and view all the answers

    What is the octane number of iso-octane?

    <p>100</p> Signup and view all the answers

    What characteristic is associated with a high cetane number in diesel fuel?

    <p>Quicker ignition of fuel</p> Signup and view all the answers

    Which compound is used to improve the octane number by reducing knocking?

    <p>Tetraethyl lead (TEL)</p> Signup and view all the answers

    What happens if the combustion of diesel fuel does not start quickly enough in a compression ignition engine?

    <p>The injected diesel will all burn at once causing knocking</p> Signup and view all the answers

    What does the compression ratio in an engine indicate?

    <p>The relationship between V1 and V2</p> Signup and view all the answers

    Which of the following is true about straight chain paraffins?

    <p>They have poor antiknock properties.</p> Signup and view all the answers

    What is the primary factor that influences the knocking tendency of a fuel?

    <p>The temperature and compression ratio</p> Signup and view all the answers

    Which characteristic does NOT belong to a good quality fuel?

    <p>High moisture content</p> Signup and view all the answers

    What is the primary purpose of cracking in petroleum processing?

    <p>To convert high molecular weight hydrocarbons into lower ones</p> Signup and view all the answers

    Which type of thermal cracking is conducted at a higher temperature?

    <p>Vapour phase thermal cracking</p> Signup and view all the answers

    What is a significant advantage of catalytic cracking over thermal cracking?

    <p>Better yield of high-quality gasoline</p> Signup and view all the answers

    What does 'knocking' refer to in internal combustion engines?

    <p>Fuel igniting before the spark</p> Signup and view all the answers

    Which process requires a catalyst to improve gasoline production?

    <p>Catalytic cracking</p> Signup and view all the answers

    In which internal combustion engine does petrol serve as the fuel?

    <p>Spark ignition engine</p> Signup and view all the answers

    Which characteristic of a good fuel relates to its usability and transport?

    <p>Easy availability and low cost</p> Signup and view all the answers

    What type of catalyst is commonly used in catalytic cracking?

    <p>Alumina</p> Signup and view all the answers

    What is a key disadvantage of straight run gasoline?

    <p>Poor engine performance</p> Signup and view all the answers

    What is the formula for calculating the Lower Calorific Value (LCV) of a fuel?

    <p>LCV = GCV - 9 x H/100 x 587</p> Signup and view all the answers

    Which of the following is a method used to determine the moisture content in coal?

    <p>Weighing a sample before and after heating in a hot air oven</p> Signup and view all the answers

    What is the significance of determining the volatile matter in coal?

    <p>Lower volatile matter correlates with higher calorific value</p> Signup and view all the answers

    Which statement correctly describes fixed carbon in coal?

    <p>Higher fixed carbon percentages correlate with greater calorific value</p> Signup and view all the answers

    How is the percentage of nitrogen in coal determined?

    <p>By heating a sample with concentrated H2SO4</p> Signup and view all the answers

    What effect does high oxygen content have on coal's calorific value?

    <p>It decreases the calorific value by about 1.7% for each percentage increase</p> Signup and view all the answers

    Which testing method is employed for ultimate analysis of coal?

    <p>Combustion in an oxygen current</p> Signup and view all the answers

    Why is the presence of sulfur in coal considered undesirable?

    <p>It leads to the production of harmful gases during combustion</p> Signup and view all the answers

    What is the main purpose of proximate analysis of coal?

    <p>To assess the quality and combustion characteristics of coal</p> Signup and view all the answers

    How is the percentage of ash in coal determined?

    <p>By heating the coal sample without a lid in a muffle furnace</p> Signup and view all the answers

    Which type of fuel is characterized as being in solid state?

    <p>Wood</p> Signup and view all the answers

    What term is used for fuels that are manufactured from primary fuels?

    <p>Synthetic fuels</p> Signup and view all the answers

    Which type of calorific value accounts for the heat of condensation of combustion products?

    <p>Higher Calorific Value</p> Signup and view all the answers

    What describes a fuel primarily found in the gaseous state?

    <p>LPG</p> Signup and view all the answers

    What is the definition of calorific value?

    <p>The heat liberated during fuel combustion</p> Signup and view all the answers

    Which of the following is a primary fuel?

    <p>Coal</p> Signup and view all the answers

    What characterizes the Lower Calorific Value (LCV) of a fuel?

    <p>Permits heat escape during measuring</p> Signup and view all the answers

    Which of these fuels can be classified as a liquid fuel?

    <p>Kerosene</p> Signup and view all the answers

    What is the effect of knocking in an internal combustion engine?

    <p>Reduces fuel efficiency</p> Signup and view all the answers

    Which fuel structure has the highest knocking tendency?

    <p>Straight chain paraffins</p> Signup and view all the answers

    What is the octane number of iso-octane used as a standard of comparison?

    <p>100</p> Signup and view all the answers

    What primary factor contributes to the increase in knocking tendency?

    <p>Advancing the ignition</p> Signup and view all the answers

    What is the primary role of antiknocking agents in fuels?

    <p>Decrease knocking characteristics</p> Signup and view all the answers

    Which compound is commonly used to improve octane number in fuels?

    <p>Tetraethyl lead (TEL)</p> Signup and view all the answers

    Which characteristic is described by a higher cetane number in diesel fuel?

    <p>Quick ignition without delay</p> Signup and view all the answers

    What happens when the entire quantity of diesel is injected before combustion starts in a diesel engine?

    <p>Knocking noise is produced</p> Signup and view all the answers

    Which type of hydrocarbons are known to produce less knocking in internal combustion engines?

    <p>Alkanes</p> Signup and view all the answers

    What effect does temperature have on the rate of oxidation of hydrocarbon molecules?

    <p>It increases oxidation rates</p> Signup and view all the answers

    What does a cetane number of 40 indicate about a diesel fuel's ignition delay?

    <p>It has the same ignition delay as a mixture of 40% cetane and 60% methyl naphthalene.</p> Signup and view all the answers

    Which of the following is necessary to improve the cetane number of diesel oil?

    <p>Adding acetylene or ethyl nitrate as an additive</p> Signup and view all the answers

    Which type of engine requires diesel fuel with a cetane number of 25?

    <p>Low speed engine</p> Signup and view all the answers

    What is the cetane number assigned to methyl naphthalene?

    <p>0</p> Signup and view all the answers

    Which statement correctly describes why cetane number is important?

    <p>It influences the ignition delay of diesel fuel.</p> Signup and view all the answers

    What effect does moisture have on the effective calorific value of coal?

    <p>Decreases calorific value</p> Signup and view all the answers

    Which analysis method involves determining the percentage of carbon in coal?

    <p>Ultimate analysis</p> Signup and view all the answers

    How is ash content in coal generally viewed in terms of fuel quality?

    <p>Undesirable as it reduces calorific value</p> Signup and view all the answers

    What happens to the calorific value with an increase in oxygen content in coal?

    <p>Calorific value decreases</p> Signup and view all the answers

    Which of the following statements is true regarding the significance of volatile matter in coal?

    <p>Higher volatile matter can produce more smoke</p> Signup and view all the answers

    What method is used to determine the nitrogen content in coal?

    <p>Heating with sulfuric acid and back titration</p> Signup and view all the answers

    How is the percentage of fixed carbon in coal calculated?

    <p>100 - (% moisture + % volatile matter + % ash)</p> Signup and view all the answers

    In ultimate analysis, how is the percentage of sulfur determined?

    <p>From the washing after calorific value determination</p> Signup and view all the answers

    Why is the presence of nitrogen in coal considered undesirable?

    <p>Has no calorific value</p> Signup and view all the answers

    What is the key significance of determining the hydrogen content in coal?

    <p>Higher hydrogen content improves calorific value</p> Signup and view all the answers

    What characteristic helps improve the calorific value of a fuel?

    <p>Low oxygen percentage</p> Signup and view all the answers

    What is an important aspect of a good fuel regarding its combustion?

    <p>It should avoid explosive combustion</p> Signup and view all the answers

    Which method of cracking operates at higher temperatures?

    <p>Vapour phase thermal cracking</p> Signup and view all the answers

    What type of internal combustion engine uses petrol as fuel?

    <p>Spark ignition engine</p> Signup and view all the answers

    What is a key benefit of catalytic cracking compared to thermal cracking?

    <p>It does not need an external fuel</p> Signup and view all the answers

    What factor can improve the antiknocking properties of petrol?

    <p>Employing suitable catalysts</p> Signup and view all the answers

    What undesirable effect can be caused by high sulfur content in fuel?

    <p>Production of poisonous gases</p> Signup and view all the answers

    What happens to the catalyst during fixed bed catalytic cracking?

    <p>It can be reactivated after use</p> Signup and view all the answers

    What does 'knocking' in an internal combustion engine refer to?

    <p>Spontaneous and explosive combustion</p> Signup and view all the answers

    What is one characteristic of a good quality fuel related to its handling?

    <p>It should be easy to handle</p> Signup and view all the answers

    Study Notes

    Introduction to Chemical Fuels

    • Fuel is an essential material for industrial, domestic, and vehicular applications.
    • Limited natural fuel sources have prompted the rise of synthetic fuel manufacturing.
    • Fuel combustion involves the rapid combination of carbon and hydrogen with oxygen, releasing significant heat.

    Classification of Fuels

    • By Physical State:

      • Solid Fuels: Examples include wood, coal, and dung.
      • Liquid Fuels: Examples include petrol, kerosene, and diesel.
      • Gaseous Fuels: Examples include natural gas and LPG.

    • By Occurrence:

      • Natural Fuels: Fuels found in nature without human intervention.
      • Artificial Fuels: Manufactured from natural fuels.

    Calorific Value

    • Defined as the heat released when a unit mass of fuel completely burns.

    • Types of Calorific Value:

      • Higher Calorific Value (HCV): Total heat produced, including condensation of combustion products.
      • Lower Calorific Value (LCV): Heat produced when combustion products can escape, excluding heat of condensation.

    • Relation Between GCV and LCV:

      • LCV = GCV - Heat of condensation

    • Units of Measurement:

      • Solid and liquid fuels: calories per gram (cal/g), kilocalories per kilogram (kcal/kg).
      • Gaseous fuels: kilocalories per cubic meter (kcal/m³).

    Analysis of Coal

    • Proximate Analysis: Assesses coal quality by evaluating:

      • Moisture: Affects heat liberation; high moisture reduces calorific value.
      • Volatile Matter: Determines the burning characteristics; lower values indicate better coal quality.
      • Ash: Non-combustible matter that lowers calorific value.
      • Fixed Carbon: Calculated by 100 - (% moisture + % volatile matter + % ash).

    • Ultimate Analysis: Determines specific elements in coal:

      • Carbon and Hydrogen: High percentages indicate better quality.
      • Nitrogen: Undesirable as it contributes no calorific value.
      • Sulphur: Reduces quality and causes pollution.
      • Oxygen: High levels decrease calorific value.

    Characteristics of Good Fuel

    • Availability and economic cost.
    • Low moisture content to enhance calorific value.
    • Moderate ignition temperature and low ash residue.
    • Safe handling, non-explosive combustion, and no toxic emissions.

    Cracking of Petroleum Fractions

    • Decomposes high molecular weight hydrocarbons into lighter ones.

    • Essential due to high gasoline demand exceeding direct distillation yields.

    • Methods of Cracking:

      • Thermal Cracking: Uses heat and pressure to produce gasoline.
        • Liquid Phase: Cracks oil at 475-530°C.
        • Vapour Phase: Cracks vaporized oil at 600-650°C.
      • Catalytic Cracking: Improves yield/quality using catalysts such as alumina.
        • Processes include fixed bed and moving bed catalytic cracking with varying pressures.

    Internal Combustion (IC) Engine

    • Combustion of fuel-air mixture occurs internally.

    • Types of engines:

      • SI Engine: Utilizes petrol with spark ignition.
      • CI Engine: Uses diesel with compression ignition.

    • Knocking:

      • Uncontrolled combustion causing metallic noise and loss of efficiency.
      • Influenced by fuel type, engine design, and operational conditions.

    Octane and Cetane Numbers

    • Octane Number: Measures fuel's knocking resistance in SI engines.

      • Iso-octane = 100, n-heptane = 0; octane number defines a fuel's quality.

    • Cetane Number: Indicates knocking characteristics of diesel fuel.

      • Higher cetane numbers signify easier ignition and combustion efficiency.

    Antiknocking Agents

    • Substances added to increase octane ratings and reduce knocking, e.g., TEL and MTBE.
    • TEL forms harmful lead oxide; safer alternatives are sought to minimize environmental impacts.

    Diesel Knocking

    • Abnormal combustion in CI engines can lead to excessive pressure and sound.
    • Knocking depends on the properties of diesel and engine design.

    Summary

    • Understanding fuel types, properties, and analysis methods is crucial for efficient energy use and development of cleaner alternatives.### Fuel Ignition in Compression Ignition Engines
    • Quick ignition of fuel is crucial upon injection into a compression ignition engine cylinder.
    • The time from fuel injection start to combustion onset is known as the ignition delay period.

    Cetane and Ignition Quality

    • Cetane (C16H34) is a saturated hydrocarbon that ignites rapidly, assigned a cetane number of 100.
    • Methyl naphthalene, being an aromatic hydrocarbon, has a long ignition delay and a cetane number of zero.
    • Cetane number indicates a fuel's ignition quality, defined as the volume percentage of cetane in a mixture with methyl naphthalene that matches the ignition delay of the fuel being tested.

    Comparison and Examples

    • A diesel fuel with a cetane number of 40 has an ignition delay equal to a mixture of 40% cetane and 60% methyl naphthalene.
    • Different diesel engines necessitate fuels with varying cetane numbers:
      • High-speed engines require cetane number of 50.
      • Medium-speed engines require cetane number of 45.
      • Low-speed engines require cetane number of 25.

    Improving Cetane Number

    • Cetane number of diesel can be enhanced by using additives such as:
      • Acetylene
      • Ethyl nitrile
      • Ethyl nitrate
      • Acetone

    Introduction to Chemical Fuels

    • Fuel is an essential material for industrial, domestic, and vehicular applications.
    • Limited natural fuel sources have prompted the rise of synthetic fuel manufacturing.
    • Fuel combustion involves the rapid combination of carbon and hydrogen with oxygen, releasing significant heat.

    Classification of Fuels

    • By Physical State:

      • Solid Fuels: Examples include wood, coal, and dung.
      • Liquid Fuels: Examples include petrol, kerosene, and diesel.
      • Gaseous Fuels: Examples include natural gas and LPG.

    • By Occurrence:

      • Natural Fuels: Fuels found in nature without human intervention.
      • Artificial Fuels: Manufactured from natural fuels.

    Calorific Value

    • Defined as the heat released when a unit mass of fuel completely burns.

    • Types of Calorific Value:

      • Higher Calorific Value (HCV): Total heat produced, including condensation of combustion products.
      • Lower Calorific Value (LCV): Heat produced when combustion products can escape, excluding heat of condensation.

    • Relation Between GCV and LCV:

      • LCV = GCV - Heat of condensation

    • Units of Measurement:

      • Solid and liquid fuels: calories per gram (cal/g), kilocalories per kilogram (kcal/kg).
      • Gaseous fuels: kilocalories per cubic meter (kcal/m³).

    Analysis of Coal

    • Proximate Analysis: Assesses coal quality by evaluating:

      • Moisture: Affects heat liberation; high moisture reduces calorific value.
      • Volatile Matter: Determines the burning characteristics; lower values indicate better coal quality.
      • Ash: Non-combustible matter that lowers calorific value.
      • Fixed Carbon: Calculated by 100 - (% moisture + % volatile matter + % ash).

    • Ultimate Analysis: Determines specific elements in coal:

      • Carbon and Hydrogen: High percentages indicate better quality.
      • Nitrogen: Undesirable as it contributes no calorific value.
      • Sulphur: Reduces quality and causes pollution.
      • Oxygen: High levels decrease calorific value.

    Characteristics of Good Fuel

    • Availability and economic cost.
    • Low moisture content to enhance calorific value.
    • Moderate ignition temperature and low ash residue.
    • Safe handling, non-explosive combustion, and no toxic emissions.

    Cracking of Petroleum Fractions

    • Decomposes high molecular weight hydrocarbons into lighter ones.

    • Essential due to high gasoline demand exceeding direct distillation yields.

    • Methods of Cracking:

      • Thermal Cracking: Uses heat and pressure to produce gasoline.
        • Liquid Phase: Cracks oil at 475-530°C.
        • Vapour Phase: Cracks vaporized oil at 600-650°C.
      • Catalytic Cracking: Improves yield/quality using catalysts such as alumina.
        • Processes include fixed bed and moving bed catalytic cracking with varying pressures.

    Internal Combustion (IC) Engine

    • Combustion of fuel-air mixture occurs internally.

    • Types of engines:

      • SI Engine: Utilizes petrol with spark ignition.
      • CI Engine: Uses diesel with compression ignition.

    • Knocking:

      • Uncontrolled combustion causing metallic noise and loss of efficiency.
      • Influenced by fuel type, engine design, and operational conditions.

    Octane and Cetane Numbers

    • Octane Number: Measures fuel's knocking resistance in SI engines.

      • Iso-octane = 100, n-heptane = 0; octane number defines a fuel's quality.

    • Cetane Number: Indicates knocking characteristics of diesel fuel.

      • Higher cetane numbers signify easier ignition and combustion efficiency.

    Antiknocking Agents

    • Substances added to increase octane ratings and reduce knocking, e.g., TEL and MTBE.
    • TEL forms harmful lead oxide; safer alternatives are sought to minimize environmental impacts.

    Diesel Knocking

    • Abnormal combustion in CI engines can lead to excessive pressure and sound.
    • Knocking depends on the properties of diesel and engine design.

    Summary

    • Understanding fuel types, properties, and analysis methods is crucial for efficient energy use and development of cleaner alternatives.### Fuel Ignition in Compression Ignition Engines
    • Quick ignition of fuel is crucial upon injection into a compression ignition engine cylinder.
    • The time from fuel injection start to combustion onset is known as the ignition delay period.

    Cetane and Ignition Quality

    • Cetane (C16H34) is a saturated hydrocarbon that ignites rapidly, assigned a cetane number of 100.
    • Methyl naphthalene, being an aromatic hydrocarbon, has a long ignition delay and a cetane number of zero.
    • Cetane number indicates a fuel's ignition quality, defined as the volume percentage of cetane in a mixture with methyl naphthalene that matches the ignition delay of the fuel being tested.

    Comparison and Examples

    • A diesel fuel with a cetane number of 40 has an ignition delay equal to a mixture of 40% cetane and 60% methyl naphthalene.
    • Different diesel engines necessitate fuels with varying cetane numbers:
      • High-speed engines require cetane number of 50.
      • Medium-speed engines require cetane number of 45.
      • Low-speed engines require cetane number of 25.

    Improving Cetane Number

    • Cetane number of diesel can be enhanced by using additives such as:
      • Acetylene
      • Ethyl nitrile
      • Ethyl nitrate
      • Acetone

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    Description

    This quiz focuses on the introduction of chemical fuel, exploring its significance in industrial, domestic, and vehicular applications. It discusses the limitations of natural fuel sources and the importance of synthetic fuel manufacturing processes. Test your knowledge on the composition, structure, and utility of various fuels.

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