The internal combustion engines diversification
technology and fuel research for the future: a review
Rosli Abu Bakar, Semin, Abdul Rahim Ismail
Automotive Focus Group, Faculty of Mechanical Engineering
University of Malaysia Pahang
Locked Bag 12, Bandar MEC Gambang, 25000 Kuantan Pahang MALAYSIA
ABSTARCT
The internal combustion engine (ICE) is already
100 years old, no better prime mover for vehicle has so
far been invented for common use. The continuously
rising prices of hydrocarbon fuels and the needs of
environmental protection have determined the
development trends of combustion systems and account
for the preference for the compression-ignition engine
over the conventional spark-ignition engine for driving
vehicles. Intense research is now in progress on the use
of gaseous fuels and methanol, but this would
necessitate certain adaptive charges in the combustion
systems of the engines operated so far. There exist
numerous and diversified designs of combustion
systems but all are based on the same principles. In the
century that has elapsed since it was first introduced,
the internal combustion engine in its various forms
has come to dominate the transport field has conferred
on mankind a degree of individual mobility never
previously known. The depletion of oil reserves, and
rising prices for hydrocarbon fuels, inevitably pose
important questions concerning the future of this source
of motive power. This article reviews the general future
of such engines and the way in which they are being
adapted to changing circumstances.
Keywords : Internal combustion engine,
development rends, diversified design.
revolutionized the world. After ten years (1886) an ICE
was installed in a motorcar, and after twenty seven years
(1903) was installed in an aircraft. In 1974 some 35 million
motor vehicles driven by engines based on the Otto cycle
were produced. In 1893, Rudolf Diesel constructed an
experimental compression-ignition engine and patented the
relevant cycle in 1892 (Patent DRP N0,67207, 1892). Four
years later, a working version of the engine had an
efficiency of 26% at a power output of approximately
14.7kW (20 hp). This although the engine was not
originally applied for driving a vehicle, was the second
fundamental invention in the history of the automobile. In
1976, the total output by the West European countries only
was 5,200,000 compression-ignition engines. Although the
gas turbine was invented by John Barber in 1791, it was
not until 1939 that is became a fully efficient driving
engine. Its subsequent rapid development was due to its
being applied in air-craft engineering.
Other heat engines invented later then internal
combustion reciprocating engine were not suitable for wide
and common use in vehicles or aircraft. The regular
development of ICE changes direction in answer to
changing requirement. In the 1970, the two most important
problems determining the development trends of engines
technology, and in particular, their combustion systems.
They were environmental protection against emission and
noise, and shortage of hydrocarbon fuels. The brief
comparison of a variety of engine undertaken in what
follows principally concerns specific fuel consumption,
toxic properties of emissions, and other technical and
economic parameters.
1 INTRODUCTION
2 THE INTERNAL COMBUSTION ENGINES
In 2006, a hundred and thirty years had passed
since Nicolas August Otto constructed a four-stroke
gas-fuelled internal combustion engine and patented its
cycle in 1876 (Patent DRP No.532,1876). In spite of the
fact that the power output of the engine was only
approximately 2.2kW (3 hp) and ignition was started by
hot gases, it was a precursor of modern Internal
Combustion Engine (ICE) because the mixture was
compressed and burned in a single cylinder, the
machine also had other interesting design features. It
can be said without exaggeration that this invention
The internal combustion engines is a heat engine in
which the burning of a fuel occurs in a confined space
called a combustion chamber. This exothermic reaction of
a fuel with an oxidizer creates gases of high temperature
and pressure, which are permitted to expand. An internal
combustion engine is that useful work is performed by the
expanding hot gases acting directly to cause movement, for
example by acting on pistons, rotors, or even by pressing
on and moving the entire engine itself.
Fig.1 The ICE and this components [8]
The term of Internal Combustion Engine (ICE) is
almost always used to refer specifically to reciprocating
engines, Wankel engines and similar designs in which
combustion is intermittent. However, continuous
combustion engines, such as jet engines, most rockets
and many gas turbines are also internal combustion
engines. The most common fuels in use today are made
up of hydrocarbons and are derived from petroleum.
These include the fuels known as diesel, gasoline and
liquified petroleum gas. Most internal combustion
engines designed for gasoline can run on natural gas or
liquified petroleum gases without modifications except
for the fuel delivery components. Liquid and gaseous
biofuels, such as Ethanol can also be used. Some can
run on Hydrogen; however, this can be dangerous.
Hydrogen burns with a colorless flame, and
modifications to the cylinder block, cylinder head, and
head gasket are required to seal in the flame front.
Experimentation at Southwest Research Institute
showed that without such modifications flame leaks
from the exhaust manifolds were common. Since the
flame was colorless, it was not visible to the naked eye.
An invisible flame is more dangerous than a visible
flame, since one cannot take into account what cannot
be seen, and operator injury was regarded as a definite
danger. However BMW has recently designed a 12cylinder Hydrogen powered car, and the company has
stated that it plans to market the vehicle. All internal
combustion engines must have a means of ignition to
promote combustion. Most engines use either an
electrical or a compression heating ignition system.
Electrical ignition systems generally rely on a lead-acid
battery and an induction coil to provide a high voltage
electrical spark to ignite the air-fuel mix in the engine's
cylinders. This battery can be recharged during
operation using an alternator driven by the engine.
Compression heating ignition systems, such as diesel
engines and HCCI engines, rely on the heat created in
the air by compression in the engine's cylinders to
ignite the fuel. Once successfully ignited and burnt, the
combustion products, hot gases, have more available
energy than the original compressed fuel/air mixture
(which had higher chemical energy). The available energy
is manifested as high temperature and pressure which can
be translated into work by the engine. In a reciprocating
engine, the high pressure product gases inside the cylinders
drive the engine's pistons. Once the available energy has
been removed the remaining hot gases are vented (often by
opening a valve or exposing the exhaust outlet) and this
allows the piston to return to its previous position (Top
Dead Center - TDC). The piston can then proceed to the
next phase of its cycle, which varies between engines. Any
heat not translated into work is a waste product and is
removed from the engine either by an air or liquid cooling
system. The parts of an engine vary depending on the
engine's type. For a four-stroke engine, key parts of the
engine include the crankshaft, one or more camshafts and
valves. For a two-stroke engine, there may simply be an
exhaust outlet and fuel inlet instead of a valve system. In
both types of engines, there are one or more cylinders and
for each cylinder there is a spark plug , a piston and a
crank. A single sweep of the cylinder by the piston in an
upward or downward motion is known as a stroke and the
downward stroke that occurs directly after the air-fuel mix
in the cylinder is ignited is known as a power stroke. A
Wankel engine has a triangular rotor that orbits in an
epitrochoidal chamber around an eccentric shaft. The four
phases of operation (intake, compression, power, exhaust)
take place in separate locations, instead of one single
location as in a reciprocating engine. A Bourke Engine uses
a pair of pistons integrated to a Scotch Yoke that transmits
reciprocating force through a specially designed bearing
assembly to turn a crank mechanism. Intake, compression,
power, and exhaust all occur in each stroke of this yoke.
Fig.3 Four-stroke operating cycle of ICE [8]
2.1 Petrol engines
The term gasoline engine / spark-ignition engine is
normally used to refer to internal combustion engines
where the fuel-air mixture is ignited with a spark. Sparkignition engines can be either two-stroke or four-stroke,
and are commonly referred to as "gasoline engines" in
US English and "petrol engines" in British English.
However, these terms are not preferred, since sparkignition engines can (and increasingly are) run on fuels
other than gasoline, such as methanol, ethanol, CNG,
hydrogen, and nitromethane. A four-stroke sparkignition engine is an Otto cycle engine, Hardenberg [6].
The cycle begins at top dead centre (TDC), when the
piston is furthest away from the crankshaft. On the first
stroke (intake) of the piston, a mixture of fuel and air is
drawn into the cylinder through the intake (inlet) port.
The intake (inlet) valve (or valves) then close(s) and the
following stroke (compression) compresses the fuel-air
mixture.
fuel filter and fuel lines. Other engines utilize small electric
heaters called glow plugs inside the cylinder to warm the
cylinders prior to starting. A small number use resistive
grid heaters in the intake manifold to warm the inlet air
until the engine reaches operating temperature. Engine
block heaters (electric resistive heaters in the engine block)
plugged into the utility grid are often used when an engine
is shut down for extended periods (more than an hour) in
cold weather to reduce startup time and engine wear.
Fig.5 Diesel engine
Fig.4 Petrol engine
The air-fuel mixture is then ignited, usually by a
spark plug for a gasoline or Otto cycle engine or by the
heat and pressure of compression for a Diesel cycle of
compression ignition engine, at approximately the top
of the compression stroke. The resulting expansion of
burning gases then forces the piston downward for the
third stroke (power) and the fourth and final stroke
(exhaust) evacuates the spent exhaust gases from the
cylinder past the then-open exhaust valve or valves,
through the exhaust port.
2.2 Diesel engines
The diesel engines is a type of internal combustion
engine; more specifically, it is a compression ignition
engine, in which the fuel is ignited solely by the high
temperature created by compression of the air-fuel
mixture, rather than by a separate source of ignition,
such as a spark plug, as is the case in the gasoline
engine. The engine operates using the diesel cycle. In
very cold weather, diesel fuel thickens and increases in
viscosity and forms wax crystals or a gel. This can
make it difficult for the fuel injector to get fuel into the
cylinder in an effective manner, making cold weather
starts difficult at times, though recent advances in diesel
fuel technology have made these difficulties rare. A
commonly applied advance is to electrically heat the
A vital component of older diesel engine systems was the
governor, which limited the speed of the engine by
controlling the rate of fuel delivery. Unlike a petrol
(gasoline) engine, the incoming air is not throttled, so the
engine would overspeed if this was not done. Older
injection systems were driven by a gear system from the
engine (and thus supplied fuel only linearly with engine
speed).
2.3 Wankel rotary engines
Wankel was invented by German engineer Felix
Wankel. Wankel first conceived his rotary engine in 1954
(DKM 54) and the KKM 57 (the Wankel rotary engine) in
the year 1957. Considerable effort went into designing
rotary engines in the 1950s and 1960s. They were of
particular interest because they were smooth and very quiet
running, and because of the reliability resulting from their
simplicity. The Wankel rotary engine is a type of internal
combustion engine, which uses a rotor instead of
reciprocating pistons. The internal combustion engine is a
heat engine in which the burning of a fuel occurs in a
confined space called a combustion chamber. This
exothermic reaction of a fuel with an oxidizer creates gases
of high temperature and pressure, which are permitted to
expand. The defining feature of an internal combustion
engine is that useful work is performed by the expanding
hot gases acting directly to cause movement, for example
by acting on pistons, rotors, or even by pressing on and
moving the entire engine itself. This design promises
smooth high-rpm power from a compact, lightweight
engine; however, Wankel engines are criticized for poor
fuel efficiency and exhaust emissions. Since its
introduction in the NSU Motorenwerke AG (NSU) and
Mazda cars of the 1960s, the engine has been
commonly referred to as the rotary engine, a name
which has also been applied to several completely
different engine designs.
Fig.6 Wankel engine operating cycle
2.4 Gas turbine
A gas turbine, also called a combustion turbine, is a
rotary engine that extracts energy from a flow of
combustion gas. It has an upstream compressor coupled
to a downstream turbine, and a combustion chamber inbetween. (Gas turbine may also refer to just the turbine
element.) Energy is released when air is mixed with
fuel and ignited in the combustor. The resulting gasses
are directed over the turbine's blades, spinning the
turbine and powering the compressor, and finally is
passed through a nozzle, generating additional thrust by
accelerating the hot exhaust gases by expansion back to
atmospheric pressure. Energy is extracted in the form of
shaft power, compressed air and thrust, in any
combination, and used to power aircraft, trains, ships,
generators, and even tanks. Industrial gas turbines range
in size from truck-mounted mobile plants to enormous,
complex systems. The power turbines in the largest
industrial gas turbines operate at 3,000 or 3,600 rpm to
match the AC power grid frequency and to avoid the
need for a reduction gearbox. Such engines require a
dedicated building. They can be particularly efficient —
up to 60% — when waste heat from the gas turbine is
recovered by a conventional steam turbine in a
combined cycle configuration. They can also be run in a
cogeneration configuration: the exhaust is used for
space or water heating, or drives an absorption chiller
for cooling or refrigeration; cogeneration can be over
90% efficient. Simple cycle gas turbines in the power
industry require smaller capital investment than
combined cycle gas, coal or nuclear plants and can be
designed to generate small or large amounts of power.
Also, the actual construction process can take as little as
several weeks to a few months, compared to years for
baseload plants. Their other main advantage is the
ability to be turned on and off within minutes,
supplying power during peak demand. Large simple
cycle gas turbines may produce several hundred
megawatts of power and approach 40% thermal
efficiency.
3 ICE DIVERSIFICATION TECHNOLOGY
Kowalewicz [1] wrote that the Otto cycle is less
efficient than the Diesel, since the spark-ignition engine
consumes more fuel than the compression-ignition engine.
The former is characterized by higher weight and
volumetric power factors, but is very sensitive to fuel
properties and requires higher octane numbers. The Otto
cycle engine has developed in two directions. The
traditional carburetor fuel supply system is replaced by an
injection system to obtain higher acceleration. Higher
permissible instantaneous overloading, higher economic
factors of performance and lower emissions. The
conventional ignition system is replaced by electronic
circuits. The other trend of development is oriented toward
reducing emission toxicity by applying the principle of
stratified chage. This principle can be implemented in
various ways. Stratified charge engines will be more and
more widely used, so that in 1985 it will presumably
replace conventional engines equipped with after-burning
catalytic reactor.
The stratific-charge engine will in the future be very
competitive with the diesel engine. Inherent in the standard
spark-ignition carburetor engine are certain very
disadvantageous features such as high fuel consumption
and high emission toxicity. For this reason, it will be
replaced in self-propelled vehicles by the diesel high-speed
engine which is less expensive in operation and less toxic.
For the same reasons, two-stroke engines have very narrow
applications. An interesting forecasting analysis concerning
selection of an engine for passenger cars was carried out.
The choice lays mainly between the four stroke carburetor
and compression engine. It was found that, mounted on an
automobile of given weight, a compression ignition engine
consumes from 25 to 30% less fuel than carburetor engine.
It follow from this experiment that not only is the diesel
engine less costly in use but also that is emits less toxic
pollutants per kilometer. The development of four stroke
compression-ignition engines has been stimulated by
economic and environmental protection requirement and
has taken the following directions.
Fig.7 Two multifuel stratified-charge engines
Diesel engines of low and medium power output are
applied mainly for propelling vehicles (passenger vehicles,
short distance pick-ups and similar types) and tend to meet
the requirements of environmental protection (low
emission toxicity and slight noise) event at the expense of
greater fuel consumption, of importance here is the
tendency to high power factors per engine volume but
without supercharging. In these engines, the
combustion system is equipped with a divided chamber.
On the other hand, as regard high power out engines
designed for intercity coaches and heavy trucks, the
demand is for the lowest possible running costs, that is,
low fuel consumption and long operational life. These
engines are mostly fitted with direct fuel injection and
as compared with those used in the 1950-1960, their
combustion systems have been modernized. Very often
they are supercharged. At least in European built
engines, the problem of emission toxicity is not very
important. The farm and industrial engines (with the
exception of those employed in mines and interiors)
should meet similar requirements. Attemps are being
mode to economize fuel by reducing power, particularly
in passenger cars (American-built cars have
considerable surplus power output). Legal regulations
covering permissible toxic emission from diesel engines
were introduced in 1973 in U.S.A and in 1975 in Japan.
In Western in Europe the legal regulations introduced in
1971 covered only spark-ignition engines limits on CO
and HC but they are to be extended also to diesel
engines. Clearly,
economic
and
environmental
protection reasons are insignificant in certain
applications. These are engines used in racing and
sports motor-cycles and cars and propelling aircraft. In
this applications, the most vital are power factors for
engine volume and weight. Spark-ignition engines,
achieving volumetric power factors higher than 100
kW/dm3, have no competition in this field. Two-stroke
engines have even greater power factors and are still
use on racing motor cycles, but in aircraft engineering
they are virtually inapplicable because they consume
more fuel which thus imposes additional fligt load.
The Wankel petrol engine operating in the Otto
cycle, has advantages such as high weight power factor,
smooth running and the possibility of using fuels of low
octane number. However, its development has come to
a standstill as a result of its consuming more fuel than
other types of engines and its emission being highly
toxic of hydrocarbons and carbon oxide. The Wankel
engine is also more costly since only little experience
has so far been acquired in relevant production
processes.
Wankel
automobile
engines
was
manufactured by the Mazda and NSA companies but
only on small scale. Citroen ceased production of them
in 1974. Because the Wankel engine with a Diesel cycle
is difficult in design and production processes,
prospects for its future development are break.
The gas turbine used for driving vehicles which are
no competitive with the piston engine is in the range of
low and medium power because its cyclic efficiency is
poorer and consequently its specific fuel consumption
is high. However, increasing demand for high driving
power in heavy vehicles of 6 to 7.5 kW/t (8 to 10 hp/t)
may. Within the range of power above 300 kW (400 hp)
where gas turbine and compression ignition engines
become comparable, lead to confrontation. At partial
loading, the turbine consumes more fuel than spark and
compression ignition engines, this being a major
disadvantage regarding the weight power factor at ouput
higher than 75kW (100 hp), the gas turbine is considerably
advantageous and thus is much more suitable for special
vehicles requiring a light-weight driving unit and high
acceleration. In high speed aircraft also, the piston engine
has been replaced by the gas turbine mainly due to its
weight and volumetric power factors and small dimensions.
But aircraft used for training and agricultural purpose are
still propelled by piston (spark ignition) engines since they
are more economic. Emission from the gas turbine are less
toxic than those from the spark-ignition piston engine, the
excess make them comparable with those of the diesel
engine. Combustion in the gas turbine is owing to the
existing conditions (continuous process, low pressure),
almost perfect and complete (consequently low
concentrations of CO and HC). But since the temperature
and oxygen excess are high, the concentration of nitric
oxide (NO) is relatively high and comparable to that of the
diesel engine. Taking into account economic factors
(production costs, greater fuel consumption) and the
comparable toxicity of emission, it may be said in
conclusion that the gas turbine cannot complete with the
piston engine for power output smaller than 260 to 300 kW
(350 to 400 hp).
Fig. 8 Concept for NOx and PM reduction [4]
Fig. 7 Schematic diagram of swirl chamber (multi)
Fig. 8 Schematic diagram of swirl chamber (single)
4 ICE DIVERSIFICATION FUEL
The future of internal combustion engines will be
influenced by two factors, there are the future cost and
the availability of suitable fuels. The use of nonconventional fuels in ICE is one of the development
trends in view of today’s imperative demands regarding
engines, such unconventional fuels may be methanol
(liquid) and the following gases : methane, propane,
natural gas containing methane, as well as hydrogen.
Tabel 1 Fuel properties at 250C and 1 atm
particular, with excessive air supply and consequently,
lower emission toxicity. Since the hydrocarbon gases have
poorer self-ignition properties than diesel oil, gases are
applicable mainly in spark-ignition engines. Kowalewicz
[1] said that the gas spark-ignition engine has a lower
efficiency and a higher fuel consumption than the
compression-ignition engine but at the same time, the
concentration of its combined toxic constituents is lower.
Since these engines present difficulties in operation
because frequent exchange of gas-filled tank, explosion
hazard-especially in the case of hydrogen, large size of the
tank, etc. They are likely to be used on urban buses and
short distance pick-ups.
5 CONCLUSION
The most efficient conversion of the energy of fuel
into work so as to obtain the highest possible power output
of the engine, the lowest possible emission of toxic
compounds into the atmosphere and the longest operational
life of the prime mover. Combustion systems can be
optimized according to three basic criteria, maximum
economy in operation, maximum obtainable power output
and minimum toxicity of emissions. The design of a
combustion system in ICE is based on the optimal choice
of the sub systems, so that they may meet the defined
criteria or conditions of optimization. The number of
common factors that can be optimally chosen as regards
combustion processes is limited, but they can be combined
in numerous ways.
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Fig. 9 NOx emission of hydrogen[3]
Fig. 10 Thermal efficiency of hydrogen [3]
The spark-ignition methanol engine feature an
indicated efficiency higher than the petrol engine, in
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