Page 428 - Advances in Eco-Fuels for a Sustainable Environment

Engine modification for alternative fuels usage in diesel engine 381

that the NO emission is increased with an increase in alcohol percentage in
biodiesel-diesel blends. This is due to the oxygen availability in the biodiesel-diesel-
alcohol blends which enhanced the combustion process resulted in more NO
emission formation. More amount of biodiesel-diesel-alcohol blend was burned
at premixed combustion phase which increments in-cylinder pressure and temper-
ature, leads to the formation of more NO emission. The minimum NO emission
of 546ppm was obtained for B90-D5-H5 blend at NOP of 200bar and FIT of 19°
CA bTDC. Higher latent heat evaporation of biodiesel-hexanol blends suppressed
the combustion temperature and resulted in lower NO emission. The NO emission
was extremely high at higher NOP and advanced FIT for all tested fuels; this was
because of better atomization, evaporation, homogeneous mixing, and more ID
period. The minimum NO emission was produced at retarded FIT rather than
advanced FIT. This was because of poor air-fuel mixtures due to a lower ID period
resulting in incomplete combustion. Thus, it reduced the cylinder peak pressure
(CGPP) and temperature caused minimum NO emission. The maximum NO
emission of 2106 and 1946ppm was obtained in diesel and B85-D5-P10 blend at
NOP of 600bar and FIT of 27°CA bTDC. B100 has the minimum NO emission
as compared to all tested fuels due to lesser iodine value.
The variation of smoke with respect to different NOP and FIT for biodiesel-diesel-
alcohol blend is illustrated in Fig. 13.11. The smoke is an indication of incomplete
combustion. The smoke emission generally depends on volatility of fuel, air-fuel ratio,
fuel composition, latent heat of evaporation, mixing distribution, ignition delay
period, and fuel burning velocity [48, 49]. Fig. 13.11, it can be seen that increase
in NOP and FIT reduced the smoke emission. The maximum smoke was obtained
at lower NOP and retarded FIT for all tested biodiesel-diesel-alcohol blends. This
was due to poor atomization and lesser ignition delay period, and led to the partial
combustion resulting in higher smoke emission. Fig. 13.11 stated that the increase
in alcohol percentage in biodiesel-diesel blends decreased the smoke emission. This
was due to oxygen availability in biodiesel-diesel-alcohol fuels, which improved the
combustion efficiency and resulted in lower smoke emission. The B85-D5-P10 blend
obtained the minimum smoke of 1.52 FSN at NOP of 500bar and FIT of 27° bTDC.
The maximum smoke of 3.02 FSN was obtained in the B90-D5-H5 blend at NOP of
200bar and FIT of 19° bTDC. The diesel has the maximum smoke emission of 4.46
FSN at NOP of 200bar and FIT of 19° bTDC.
Cylinder gas peak pressure (CGPP) of biodiesel-diesel-alcohol blends at different
FIT and NOP is illustrated in Fig. 13.12. The maximum amount of fuel burnt fraction
at premixed phase combustion caused more CGPP in the engine. Fig. 13.12 states
that the CGPP is increased with an increase in NOP and FIT for biodiesel-diesel-
alcohol blends. This was due to higher NOP reducing the diameter of the droplet
and enhancing the evaporation rate of the fuel. Advanced FIT timing increases
the ignition delay period and enhances the air-fuel mixture process, resulting in more
premixed phase combustion that led to higher CGPP and temperature. The maxi-
mum and minimum CGPP of 64.68 and 60.56bar were obtained in B90-D5-H5
blendB100atNOP of 600bar,27°CA bTDC and 200bar, 19°CA bTDC respec-
tively. Diesel fuel has the maximum CGPP of 65.71bar at 500bar and 27°CA bTDC.