Internal Combustion Engines – A review of Theory and Performance

Internal Combustion Engines – A review of Theory and Performance with Alternate
Fuels
Introduction
With the advent of technological revolution, the demand for power generation has been
steadily increasing. To this effect, Internal Combustion(IC) engines have positioned
themselves as the most widely used power generation devices with applications ranging from
automobiles, standalone power-generators and marine applications. A lot of research has
gone underway to improve their performance over the years. Further, with greater emphasis
being laid on environmental sustainability, the need for regulation of emissions from IC
engines has increased too. Thus exploration of alternative fuels has also gained thrust. In the
present study, we have described the working of IC engines. We then present a critical review
of the work done on alternate fuels by Efemwenkiekie et al [1]. They performed experimental
analysis of ethanol-gasoline blend on the performance of a 4-stroke spark ignited(SI) engine.
The results of their study encourage the use of ethanol as alternate fuel.
Internal Combustion Engines
Internal Combustion (IC) Engines are a type of Heat engines. They are devices which
convert the thermal energy into mechanical energy or useful work. Heat engines are broadly
classified into two categories i) External Combustion Engines and ii) Internal Combustion
Engines.
External Combustion Engines are the engines in which combustion of fuel takes place outside
engine or the chamber. One example is the steam engine. On the other hand, Internal
Combustion engines are those in which the combustion of fuel takes place inside the
combustion chamber. The use of internal combustion(IC) engines has become more prevalent
than external combustion (EC) engines on account of several advantages they offer over the
latter. Two key factors influencing their widespread utility are drivability and
durability[2].Other advantages IC engines offer over EC engines include higher power output
per unit weight, higher brake thermal efficiency, requirements of lesser space and
compactness. IC engines can be further classified depending upon various criteria. These are
summarised as follows:
a) According to the engine design
i) Reciprocating engine ii) Rotary gas turbines
b) Reciprocating are further classified according to the method of ignition
i) Spark Ignition ii) Compression ignition
c) According to the cycle of operation
i) Two stroke cycle engine ii) Four stroke cycle engine
d) According to the thermodynamic cycle
i) Otto cycle or constant volume ii) Diesel cycle or constant pressure

The most common types of IC engines used are the Reciprocating Engines. They are
primarily used in automobile applications. The two types of reciprocating engines used are
spark ignited (SI) and combustion ignited (CI) engines. In the subsequent sections we discuss
the design and operating principles of the SI and CI engines.
Parts of internal combustion engines
Figure 1 gives an illustration of the different parts of the engine. The main parts of IC engines
are:
i) Cylinder ii) Cylinder Head/Cylinder cover
iii) Piston iv) Piston Rings
v) Connection Rod vi) Crank
vii) Crank Shaft viii) Fly wheel
ix) Crank case
Figure 1. IC Engine Parts (SI) [3]
Operating cycles
The reciprocating engines operate on either Four-stroke cycles or the Two-stroke cycles.
Majorly four-stroke cycles are used for reciprocating engines. Four-stroke cycles consist of
2