Engineering Chemistry

Fuels and Combustion Viva Questions

Fuels and Combustion Viva Questions

Fuels and Combustion Viva Questions, Viva Questions on Fuels and Combustion, Short Answer Questions on Fuels and Combustion, Engineering Chemistry Viva Questions, Engineering Viva Questions

Polymer Viva Questions

Short Answer Questions

Q.1. Define fuel and give some examples.

Ans. Fuel is a combustible substance containing carbon as the major constituent which on proper burning gives a large amount of heat that can be used economically for domestic and industrial purposes.

Examples are coal, petrol, diesel, etc.

Q.2. Write the classification of fuels according to the occurrence.

Ans. According to the occurrence, the fuels are classified into natural (primary) and secondary (derived) fuels.

Q.3. What are the units of heat and their inter-conversions?

Ans. Units of heat are calorie, kilocalorie, British thermal unit, and centigrade heat unit.

1 kcal = 1000 cal = 3.968 BTU = 2.2 CHU

Q.4. Define calorific value and give the relation between higher and lower calorific values.

Ans. Calorific value is the total quantity of heat liberated by the complete combustion of one unit mass/volume of fuel in oxygen.

LCV = HCV – latent heat of water vapor formed

Q.5. What kinds of calorimeters are used for determining the calorific value of solid, liquid, and gaseous fuels?

Ans. The Bomb calorimeter is used for determining the calorific value of solid and liquid fuels.

Junker’s calorimeter is used for determining the calorific value of gaseous fuels.

Q.6. What are the characteristics of a good fuel?

Ans. High calorific value, moderate ignition temperature, low moisture content, low non-combustible matter content, etc.

Q.7. Write the name of some of the petroleum products.

Ans. Name some of the petroleum products are Liquified petroleum gas, gasoline, petrol, kerosene, diesel oil, heavy oil, etc.

Q.8. What are the ovens used for the preparation of metallurgical coke?

Ans. Beehive oven and Otto Hoffman’s oven are the ovens used for the preparation of metallurgical coke.

Q.9. Explain cracking with a suitable example.

Ans. The process of breakdown of high molecular weight hydrocarbons of high boiling points into simple, lower molecular weight hydrocarbons of low boiling points is known as cracking.

Q.10. What is meant by flue gas?

Ans. The mixture of gases like CO2, CO, and O2 exhaust of the combustion chamber is called flue gas.

Q.11. What is the importance of the analysis of flue gas?

Ans. The analysis of flue gas either from a furnace or from an engine’s exhaust would give an idea about the efficiency of the combustion process. If the flue gas contains a considerable amount of CO, it indicates that incomplete combustion is occurring and it also indicates the short supply of O2 for combustion, and this will lead to wastage of fuel.

Q.12. What happens if the flue gas contains a considerable amount of O2?

Ans. It indicates that the O2 supply is very much in excess, and it results in loss of heat.

Q.13. Which apparatus is used in the analysis of flue gas?

Ans. Orsat’s apparatus is used in the analysis of flue gas.

Q.14. In Orsat’s apparatus, which gases are absorbed by which solutions?

Ans. In Orsat’s apparatus, the following gases are absorbed by the solutions:

  • Potassium hydroxide solution – only CO2
  • Alkaline pyrogallic acid – CO2 and O2
  • Ammonical cuprous chloride – CO, O2 and CO2

Q.15. What is Knocking?

Ans: Knocking is the metallic sound produced by a spark-ignition petrol engine under certain conditions.

Q.16. What are the Characteristics of Good Fuel?

Ans: The Characteristics of Good Fuel are:

  • HCV: The amount of heat released is dependent on high calorific value, hence fuel should possess more HCV.
  • Low moisture content: Moisture content of fuel reduces the calorific value, hence fuel should possess low moisture content.
  • Moderate ignition temperature: Minimum required temperature to preheat the fuel and starts burning is the ignition temperature. Fuel must have moderate ignition temperature, because low ignition temperature is dangerous for storage and transport due to fire hazard and for starting a fire, high ignition temperature is not suitable.
  • Moderate velocity of combustion: For continuous supply of heat, fuel must burn with a moderate velocity.
  • Low non-combustion matter and ash content: After combustion, non-combustible matter produces high ash content and also reduces the heating value. With this more heat loss, and loss of money for over storage, handling, disposal of ash, etc.
  • Low cost: Good fuel should be available easily in bulk at low cost.
  • High pyrometric effect: Pyrometric effect is the highest temperature obtained with the fuel, hence fuel should have high pyrometric effect.
  • Less pollutants/environmental friendly: By-products of combustion like CO, SO2, NO2, etc. pollute the environment, so a good fuel should release less pollutants and should be environment friendly.
  • Storage cost: Storage cost of a fuel in bulk should be low.
  • Easy transportation: Fuel should be easy to transport with low cost.
  • Uniform particle size: In case of solid fuels, for easy combustion, the particle size should be uniform.

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