This document provides an overview of fuels and combustion. It defines fuels as either natural/primary sources (solid, liquid, gas) or manufactured sources (solid, liquid, gas). Good fuels are characterized by high calorific value, moderate ignition temperature, low moisture/ash content, and being low cost and easy to store/transport. Calorific value measures the total heat released from combusting a unit of fuel, and can be expressed in various units for solids, liquids and gases. Higher calorific value refers to heat released when products cool to room temperature, while lower calorific value excludes heat of vaporization of water formed. Calorific value is determined experimentally by combusting a known fuel amount and

1. Unit-4: Fuels & Combustion
Mr. Santosh Damkondwar
Monday, January 20, 2014

2. Introduction
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Fuels
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Non-renewable Conventional Sources
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In Mechanical, Electrical & Chemical operations.

3. Characteristics of Good Fuels:
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High Calorific Values
Moderate Ignition Temperature
Low Moisture Content
Low Ash Content
Moderate Velocity of Combustion
Should not produce harmful products
Low Cost
Easy Storage & Transportation
Easily Controllable

4. Classification
•
Natural or Primary Fuels
Solid
e.g.
Wood, Peat,
Lignite,
Bituminous
Coal, Dung
Liquid
e.g.
Crude Oil,
Vegetable Oil
Gaseous
e.g.
Natural Gas

5. Classification
Solid
e.g.
Coke,
Charcoal,
Liquid
e.g.
Tar,
Kerosene,
Diesel,
Petrol,
Gaseous
e.g.
Coal Gas,
Water Gas,
Bio-Gas

6. Calorific Values:
•
Calorific Value of fuel is the total quantity of heat
liberated by complete combustion of a unit mass
(or volume) of the fuel.
• It can be expressed for Solid Fuels in terms of :
Cal/gm (CGS Unit)
Kcal/Kg (MKS Unit)
J/Kg (SI Unit)
B.Th.U. / lb (British Thermal Unit)

7. Calorific Values

8. Calorific Values:
•
Calorific Value of fuel is the total quantity of heat
liberated by complete combustion of a unit mass
(or volume) of the fuel.
• It can be expressed for Gaseous Fuels in terms of :
Cal/lit (CGS Unit)
Kcal/m3 (MKS Unit)
J/m3 (SI Unit)
B.Th.U. / Ft3 (British Thermal Unit)

9. Calorific Values

10. Calorific Values

11. Calorific Values

12. Higher Calorific Values:
•
It is the total amount of heat liberated, when unit
mass / volume of the fuel is burnt completely and
the products of combustion have been cooled to
room temperature (i.e. 15oC).

13. Lower Calorific Values:
•
It is the net amount of heat liberated, when unit
mass / volume of the fuel is burnt completely and
the products of combustion are allowed to escape.

14. Relation between GCV & LCV:
•
These can be related as:
NCV = GCV – Latent heat of water vapor formed
or
= GCV – (Mass of Hydrogen × Latent heat of steam)
= GCV – [(9 × Mass of hydrogen) × Latent heat of
steam]
If mass of hydrogen is expressed as % of H, then
NCV = GCV – [9× H/100 × 587] cal/gm

15. Determination of Calorific Value:
•
Calorific Value of the fuel is determined by
heating known amount of fuel, in presence of
oxygen in calorimeter.
•
Principle
o
Total heat liberated by complete combustion of
known amount of fuel is absorbed by the known
mass of water in calorimeter. From the rise in
temperature of water, the calorific value of fuel is
determined.