Most of the energy consumed in today's mobility industry is
derived from fossil fuels. The demand for clean, renewable and
affordable alternative energy is forcing the automotive industry to
look beyond the conventional fossil fuels. Fuels options like
liquefied petroleum gas (LPG), compressed natural gas (CNG) and
ethanol blends are quickly finding widespread acceptance as
alternative sources.
This paper presents the results of experimental studies
conducted on a 1.2-liter MPI engine with three different alternate
fuels. The fuels considered for the evaluation (apart from base
gasoline) are 10% ethanol-blended fuel (E10), LPG (gaseous propane:
butane mix) and CNG (gaseous methane). Experiments were conducted
to compare their effect on engine performance and emissions.
The test results show that E10 has the lowest power drop whereas
CNG has the highest power drop (12%) as compared to gasoline. The
maximum power drop in LPG is 4%, which is close to the theoretical
predictions. Compared to gasoline, there is no major deterioration
in low end and maximum torque with E10 and LPG. The usage of E10
required minimum engine hardware changes (restricted to fuel
lines).
The carbon dioxide (CO₂) emission in LPG mode was found to
decrease by 11% compared to 23% in CNG. The amount of carbon
monoxide (CO) and hydrocarbon (HC) emissions in LPG and CNG modes
were found to be a function of the gasoline to gas transition
temperature (with gasoline as the starting fuel). Compared to
gasoline, both the gaseous fuels resulted in higher nitrogen oxide
(NOx) emissions.
Emission tests with neat gasoline and E10 blend shows a net
decrease in diluted CO and HC emissions by 13% and 19% respectively
with E10 blends. On the other hand, NOx emissions increased by 16%.
There is a net reduction in CO₂ by 2% compared to neat
gasoline.