Liquid Fuels

1. Liquid Fuels

2. Crude Oil
 Found in rock formations that were
ocean floors.
 Organic matter from seas became
trapped by sediments at ocean floor.
 Cracking of the molecules and
elimination of oxygen turned organic
matter into petroleum.

3. Crude Oil
 Petroleum is made of 86% carbon
and 14% hydrogen.
 Hydrocarbon molecules are
accompanied by dirt, water, sulfur
and other impurities.
 Crude oil must be refined to
produce suitable engine fuels.

5. Fig. 5.1: Molecular Structures of Some
Hydrocarbon Fuel Families

10. Fuel Properties
 Standards Organizations
 SAE – Society of Automotive Engineers
 ASTM – American Society for the
Testing of Materials
 API – American Petroleum Institute

11. Specific Gravity
 A measure of the density of liquid fuels at
15.6 C as compared with water at the
same temperature.
 API devised the following scale,
 where SG is the specific gravity.
 A hydrometer, calibrated in API
o
, is used
to measure the specific gravity.
5
.
131
5
.
141


SG
API o

12. Fuel hydrometer.

15. Characterization factor

16. Characterization factor
Watson characterization factor

17. Characterization factor
Correlation Index CI

18. Ideal Combustion
 All of the H in fuel is converted to
H20.
 All of the C in fuel is converted to
CO2.
 Air is 21% O and 79% N by volume.

19. Combustion of Gasoline

20. Stoichiometric Air/Fuel Mixture
 For gasoline…
  1
:
1
.
15
1
54
.
11
51
.
3
/ 


F
A

21. Table 5.2: Representative Fuel Molecules

22. Diesel Air/Fuel Ratios
 Stoichiometric air/fuel mixture for
CI engines 14.9:1.
 However, most CI engines are
operated with a leaner air/fuel
ratios and therefore free oxygen is
often found in the exhaust.