The main purpose of this blog is
to introduce the non-conventional IC engines. In conventional engines, the
common fuels used are diesel and petrol. These fuels are becoming scare and
costly also. In addition to this, there are limited stores of these fuels and
engineers are in constant search to find the fuels which can be used to replace
the conventional fuels. As in multi fuel engines, conventional fuels are used
for starting and then the engine is shifted to unconventional fuels which are
relatively cheap.
In C.I. and S.I engines due to
many reciprocating parts and problems of balancing and vibrations, it is also
seen that the speed of IC engines are limited to 2000 to 5000 RPM. A few rotary
types of engines are developed which can solve the problem of balancing. This
also reduces the size of engines per kW as engine can be designed to run at a
higher speed of 10,000 RPM. The problem of knocking associated with
conventional engines can also be avoided in dual fuel and multi fuel engines
even by using inferior fuels.
The pollution is one of the main
problem faced by the designers with conventional IC engines. This can be partly
reduced by using different non-conventional engines as stirling engines.
In addition to the methods
mentioned above for developing the power using non-conventional engines, a
variable-compression ratio engine is developed and used for research purpose
for conducting the trials using different types of non-conventional fuels and
their effects on the performance of the engine.
Dual
fuel and MultiFuel Engines:
The dual fuel engine was
developed from the diesel engine to take advantage of relatively cheap gases
like- producer gas, biogas and natural gas. The engine uses high compression
ratio and runs with high A:F ratio like diesel engine. The gaseous fuel is
ignited by injecting ‘’pilot oil’’ into the heated mixture as it has high-self ignition temperature
compared with diesel ignition temperature.
The storage of liquid fuels and
large availability of the gaseous fuels led to an increased attention on the
dual-fuel engine. The development of transporting facilities of liquefied gases
has made natural gas available to most part of the world at considerably
cheaper rate than the conventional liquid fuels. In addition to this, biogas
for local uses, sewage gas, and producer gas are finding the partial substitute
for the conventional diesel engines. The large amount of industrial gases can
also be used for running IC engines and enhance the overall economy of the
plant.
The natural gas contains 95% CH4
and has self ignition temperatures of 7300C compared to 4700C
of petrol. Therefore, all gaseous fuels are mainly used with diesel engines.
The dual fuel engine combines the
use of diesel fuel and gaseous fuels such as natural gas, sewage gas and
biogas. The engine can be shifted from dual fuel operation to diesel operation
almost instantaneously in case of emergency.
Advantages
of Dual Fuel Engines:
Following are the major
advantages of dual fuel engines:
1. It
is preferred when cheap natural gas is easily available,
2. The
exhaust of dual fuel engines is clean as it does not contain any residue. The
pollution from the engines is very much reduced,
3. The
wear and tear of engine parts is reduced as well as consumption of lubricating
oil because of clean combustion in the engine,
4. The
engine can run on either of the fuel and the diesel requirement is hardly 5% if
it runs on gas,
5. The
utility of the engine is increased considerably as instantaneously change over
from gas to diesel and vice-versa is possible,
6. These
engines are suitable from the point of using total energy concept. Because, the
exhaust heat of the engine can be used to digest the sludge in a sewage
disposal plant and the sewage gas produced can be used to run the plant,
7. These
engines are best suited for low pressure liquefied gas (LPG) which evaporated
very easily,
8. A
typical use of dual fuel engine is to produce synthetic gas by burning CH4
and simultaneously developing power,
9. Lot
of conventional fuel can be saved if dual fuel engines are used particularly
for irrigation purposes as more than 3 million diesel powered pump sets of 2 to
35 kW capacity are currently.
The diesel engine can be operated
on gaseous fuels with minor modifications and has comparable efficiency and
therefore, it is very attractive power generating system because of its great
flexibility of operation compared with conventional diesel engines.
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