310
290
270
250
230
210
190
170
BSFC (g/kw.h)
LPG only
mw/mf = 0.125
mw/mf = 0.25
mw/mf = 0.33
mw/mf = 0.50
330

150

0
1000
2000
3000
4000
5000

Engine speed (RPM)

214
Alternative Fuels for Transportation
Figure 7.5
BSFC variations with engine speed for variations water/fuel mass ratios of water injection.
(From Ozcan, H., and Soylemez, M. S., Energy Conversion and Management, 47, 570–81, 2006.
Reprinted with permission from Elsevier Publications.)
120
100
80
60
40
20
0
Frequency
Histogram of P max
Methane
Diesel
LPG
37
38
39
40
41
42

P max, bar

Figure 7.6
Histogram of maximum combustion pressure for diesel and dual fuel engine. (From Selim,
M. Y. E., Fuel, 84, 961–71, 2005. Reprinted with permission from Elsevier Publications.)
using LPG gives slightly higher combustion pressure than using CNG
(Selim 2 005).
In dual fuel engines, gaseous fuel is usually inducted with the intake air
through the inlet manifold. They are mixed and compressed as in a conventional diesel engine. A small amount of liquid diesel fuel, called the pilot,