Page 402 - Advances in Eco-Fuels for a Sustainable Environment

356 Advances in Eco-Fuels for a Sustainable Environment

modification, the parameters such as fuel injection timing (FIT), nozzle opening pres-
sure (NOP), compression ratio, swirl ratio, injection duration, and fuel injection quan-
tity are varied [22]. Rajesh Kumar et al. [23] reported the difficulties of using lower
alcohol fuels in diesel engines because these have a lower calorific value and cetane
number. However, lower alcohols have poor mixing, partial blending with diesel, and
phase separation at low atmospheric temperatures. Moreau et al. [24] reported that
higher alcohols are the prominent alternative resources for diesel engines due to their
favorable thermodynamic and physical properties. The higher alcohols blended with
diesel and biodiesel have improved the low temperature properties. Higher alcohols
have overcome the disadvantage of lower alcohols due to better miscibility with diesel
fuel and a higher cetane number, as noticed by Sivalakshmi and Balusamy [25].
N-butanol is produced from biomass feedstock through the alcoholic fermentation
process and it has renewable additives. N-butanol has less hydrophilic tendency when
compared to ethanol and a higher cetane number and higher miscibility with diesel, as
suggested by Hansen et al. [26]. Long-chain alcohols have better miscibility with die-
sel, higher stability, no phase separation at lower temperature, high cetane number,
and latent heat. Higher alcohols overcome the drawbacks of small-chain alcohols.
Biodiesel-diesel-pentaol and biodiesel-diesel-hexanol blends are promising alterna-
tive fuels for diesel engines compared to lower alcohol fuels [5]. Atmanli et al.
[27] observed that the diesel-n-butanol-cotton oil ternary blend was a promising
next-generation fuel for diesel engines. Higher proportions of alcohol blends
enhanced the emissions characteristics. Ileri et al. [28] found that the carbon monoxide
and hydrocarbon emissions were reduced in butanol-diesel-edible oil blends. Further
addition of more butanol in biodiesel-diesel blends increased the nitric oxide (NO)
emissions.
Enhancement of fuel economy and a drop in engine emissions can be achieved by
varying FIT, NOP, and injection duration [22]. Agarwal et al. [29] stated that combus-
tion duration was significantly diminished with an increase in NOP due to better atom-
ization. Higher NOP was preferred for higher viscosity fuel to obtain better
atomization. Gumus et al. [30] found that the maximum NO emission occurred at
higher NOP due to better atomization and evaporation. At higher NOP, the droplet
size is very small, which results in faster combustion. Agarwal et al. [31] reported that
PM was reduced at higher NOP and advanced FIT. More delay periods and better air-
fuel mixtures lead to complete combustion. Rajesh Kumar et al. [23] noticed that the
maximum BTE and minimum BSFC were obtained at higher NOP. Hwang et al. [32]
noticed that UBHC and CO emissions were decreased whereas NO emission was
increased for biodiesel blends at higher NOP and advanced FIT. Sayin et al. [33]
examined the effects of NOP on CI diesel engine combustion characteristics. Results
showed that the higher NOP increased the in-cylinder temperature and pressure. The
higher NOP enhances the atomization process and reduces the fuel droplet size which
makes complete combustion and resulted in higher in-cylinder pressure and temper-
ature. Ryu [34] observed the effect of nozzle opening pressure on engine combustion
and emissions characteristics. At the lower load, NOP has a major effect on UBHC and
CO emissions. At the lower load, the CO and UBHC emissions are decreased when the
NOP increases; an increase in NOP decreased the UBHC and CO emissions at the