Arulmigu Meenakshi Amman College of Engineering
Vadamavandal-604410.
Impotant questions and answers
CME390- THERMAL POWER ENGINEERING
Prepared by
V.Umapathy,
Prof. /Mech.
S.No. Questions and answers
Unit-I
FUELS AND COMBUSTION
2 – marks question and answers
1. What is the simple definition of fuel?
Fuel: Fuels are materials that are burnt to produce a large amount of heat energy. Any substance that upon
combustion produces a usable amount of energy is known as fuel. For example wood, coal, biogas, LPG,
petrol, diesel, etc.
2. What is the calorific value of fuel?
Calorific value is defined as the amount of heat energy released during complete combustion of a unit
mass of a fuel. It is expressed in kJ/kg.
3. List the type of fuels?
1. Solid fuels-Natural fuels and artificial fuels.
2. Liquid fuels.
3. Gaseous fuels- Fixe composition gases and composite industrial gases.
4. State requirements of a good fuel?
1. It should have a high calorific value.
2. An ideal fuel should have low ignition temperature.
3. Not produce any harmful gases.
4. Produce less smoke.
, 5. Its moisture content should be low so that its heating value should be high.
6. It should evolve a large amount of heat when it is burnt.
5. Define higher calorific value of fuel.
The amount of heat obtained by the complete combustion of unit mass (or unit volume) of a fuel, when the
products of combustion are cooled down to the temperature of the air (15 0 C) supplied.
6. Define Lower calorific value of fuel.
The amount of heat obtained by the complete combustion of unit mass (or unit volume) of a fuel, when the
heat absorbed by the products of combustion (steam) is not recovered.
7. What are the properties of fuels?
Density, viscosity, heating value, flash point, acid value, pour point, cetane number, etc. are considered as
the most important properties of a fuel for its application in engine. These properties indicate the quality of
the fuel. Engine performance and emission are also directly related to these.
8. What is meant by adiabatic flame temperature?
When a combustion reaction takes place energy is released to the combustion products. If no heat is lost in
this process, the temperature of the combustion products is known as the "Adiabatic Flame Temperature."
9. What is the meaning of enthalpy of formation?
The energy released or absorbed when chemical compound is formed from its element.
10. What is sensible enthalpy?
The enthalpy change of a substance due to temperature change not accompanied by a change of phase.
13 and 15 marks question and answers
11. Determine the stoichiometric air required for the complete combustion of coal whose analysis by
weight is given below:
Carbon- 78%; Hydrogen- 3%; Oxygen-3%; Sulphur- 1%; Ash-10 % and Moisture-5%., and
also find mass of products of combustion per kg of fuel.
,
, 12. A producer gas, used as a fuel, has the following volumetric composition: H 2 = 28% ; CO=12% ;
CH4 = 2%; CO2 = 16% and N2 42% .
Find the volume of air required for complete combustion of 1 m3 of this gas. Air contains 21 %
by volume of oxygen.
Vadamavandal-604410.
Impotant questions and answers
CME390- THERMAL POWER ENGINEERING
Prepared by
V.Umapathy,
Prof. /Mech.
S.No. Questions and answers
Unit-I
FUELS AND COMBUSTION
2 – marks question and answers
1. What is the simple definition of fuel?
Fuel: Fuels are materials that are burnt to produce a large amount of heat energy. Any substance that upon
combustion produces a usable amount of energy is known as fuel. For example wood, coal, biogas, LPG,
petrol, diesel, etc.
2. What is the calorific value of fuel?
Calorific value is defined as the amount of heat energy released during complete combustion of a unit
mass of a fuel. It is expressed in kJ/kg.
3. List the type of fuels?
1. Solid fuels-Natural fuels and artificial fuels.
2. Liquid fuels.
3. Gaseous fuels- Fixe composition gases and composite industrial gases.
4. State requirements of a good fuel?
1. It should have a high calorific value.
2. An ideal fuel should have low ignition temperature.
3. Not produce any harmful gases.
4. Produce less smoke.
, 5. Its moisture content should be low so that its heating value should be high.
6. It should evolve a large amount of heat when it is burnt.
5. Define higher calorific value of fuel.
The amount of heat obtained by the complete combustion of unit mass (or unit volume) of a fuel, when the
products of combustion are cooled down to the temperature of the air (15 0 C) supplied.
6. Define Lower calorific value of fuel.
The amount of heat obtained by the complete combustion of unit mass (or unit volume) of a fuel, when the
heat absorbed by the products of combustion (steam) is not recovered.
7. What are the properties of fuels?
Density, viscosity, heating value, flash point, acid value, pour point, cetane number, etc. are considered as
the most important properties of a fuel for its application in engine. These properties indicate the quality of
the fuel. Engine performance and emission are also directly related to these.
8. What is meant by adiabatic flame temperature?
When a combustion reaction takes place energy is released to the combustion products. If no heat is lost in
this process, the temperature of the combustion products is known as the "Adiabatic Flame Temperature."
9. What is the meaning of enthalpy of formation?
The energy released or absorbed when chemical compound is formed from its element.
10. What is sensible enthalpy?
The enthalpy change of a substance due to temperature change not accompanied by a change of phase.
13 and 15 marks question and answers
11. Determine the stoichiometric air required for the complete combustion of coal whose analysis by
weight is given below:
Carbon- 78%; Hydrogen- 3%; Oxygen-3%; Sulphur- 1%; Ash-10 % and Moisture-5%., and
also find mass of products of combustion per kg of fuel.
,
, 12. A producer gas, used as a fuel, has the following volumetric composition: H 2 = 28% ; CO=12% ;
CH4 = 2%; CO2 = 16% and N2 42% .
Find the volume of air required for complete combustion of 1 m3 of this gas. Air contains 21 %
by volume of oxygen.
