Non-Conventional IC Engines

Introduction: (Part-I)

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.