ABSTRACT
In the present paper, efforts have
been made to highlight the concept of an “INTELLIGENT
COOLING SYSTEM”. The basic principle behind this is to control the flow
rate of coolant by regulating the valve by implementing FUZZY LOGIC.
In
conventional process the flow rate is constant over the entire engine jacket.
Which induces thermal stresses & reduction in efficiency.
The “INTELLIGENT COOLING SYSTEM” i.e implementation of fuzzy logic will
overcome the above stated drawbacks in any crisp situation. The flow rate of
coolant will be controlled by control unit & intelligent sensors.
INTRODUCTION
The
name “INTELLIGENT COOLING SYSTEM”
represents the improved function of cooling systems. We have given this name
because in this system the sensor will sense the cylinder temperature as
similar as thermostat and will control the opening and closing of water passage
in the piston cylinder arrangement. The mass flow rate of water will be
controlled by a valve arrangement.
For regulating flow rate, a separate
programming can be done. In this programming, the piston will be considered as
an object and a relation of “temperature = water” can be used for the above
purpose.
Our system will work on the same
principle of an “INTELLIGENT CARBURETOR”
In which its aim is to supply the correct O/P i.e. air fuel mixture by sensing
the I/P i.e. operating conditions.
But, the system which attracted the
most is the “IDLE SPEED CONTROLLER” which is used to control the idle speed of
SI engine.
Conventional
Cooling system
The
following are the two main characteristics desired of an efficient cooling system
1)
It should be capable of removing
about 30% of heat generated in the combustion chamber while maintaining the
optimum temperature of the engine under all operating conditions of the
engines.
2)
It should remove heat at a faster rate when
engine is hot. However, during starting of the engine cooling should be
minimum, so that the working parts of the engine reach their operating
temperature in a short time.
a) Liquid Cooled Systems
In
this system mainly water is used and made to circulate through the jacket
provided around the cylinder, cylinder-head, valve ports and seats where it
extracts most of the heat. The diagrammatic sketch of water circulating passage
is shown in
b) Variation of
gas temperature
There
is an appreciable variation in the temperature of the gases inside the engine
cylinder during different processes of the cycle. Temperature inside the engine
cylinder is almost the lowest at the end of suction stroke. During combustion
there is a rapid rise in temperature to a peak value which again drops during
the expansion. This variation of gas temperature is illustrated in fig (2). for
various processes in the cycle.
The cooling
system comprises of the following parts namely:
·
Radiator,
·
Thermostat,
·
Water pump &
·
Piston-cylinder assembly.
EFFECT
OF OVERHEATING :
·
Evaporation of lubricating oil that
lubricates the piston and cylinder wall. This will result in metal to metal
contact of the piston and the cylinder wall leading to piston scuffing and
piston seizure.
·
Setting up of the thermal stresses
in the cylinder, cylinder head and piston. This may lead to cracking of them.
·
Burning of the piston crown.
·
Sticking of piston rings in the
ring grooves, due to carbonization of the oil. Ring sticking will result in
inefficient sealing of the cylinder increased blow by of gases and loss of
thermal efficiency.
·
Reduction in volumetric efficiency
i.e. reduced weight of charge retained in the cylinder.
EFFECT
OF EXCESSIVE COOLING :
·
Reduction in thermal efficiency
·
Increased corrosion of engine
parts.
·
Reduced mechanical efficiency.
·
Improper vaporization of the fuel.
Also due to the inadequate supply of
the coolant the machine parts get overheated and this may lead to two effects:
·
Generation of excessive heat which
results in the break down of the engine.
·
Evaporation of the coolant (water)
may results in SCALE formation.
Effect
of high temperature on lubricating oil consumption :
High
speed produces high temperature this in turn, lowers the viscosity of the oil.
Now it can more readily work past the piston rings into the combustion chamber,
where it is burnt. Due to more temperature more oil gets into the combustion
chamber, where it burns and fouls spark-plugs, valves, rings and pistons.
Carbon formation worsens the condition since it further reduces the
effectiveness of the oil rings. The burning of oil in the combustion chamber
usually produces blue smoke from the tail pipe.
It should be remembered that abstraction of heat from the working medium by way of cooling
the engine components is a direct thermodynamic loss.
IMPLEMENTATION OF FUZZY LOGIC
To control the idle speed of spark ignition engine,
there are two possibilities. The first one is spark advancer and the second is
volumetric control of air.
In spark advancer if revolution
decreases then an advance spark increases the torque and vice versa.
In
second method if there is reduction in number of revolution, the auxiliary air
regulator increases the by-pass cross-section which increases the air flow and
vice versa.
Fuzzy in
cooling system :
Consider
the engine jacket as shown in figure 5
above which shows the sensors, valve, cylinder & an intermediate jacket, in
which sensors and valve are connected to control unit.
This control unit will not work
unless the temperature of the engine reaches to 700 C. When it
reaches to 700C or beyond it the flow will start. It begins with
maximum at middle two cylinder and less at first and last cylinders. This
change in flow rate will minimize the temperature difference between the middle
and the end cylinders. Due to this the thermal stresses get reduce and the
optimum temperature will be maintained wear will not take place.
If the temperature of the engine
cylinders increases, the sensor will sense the temperature and the signal is
given to the control unit and it controls the valve opening resulting in increase
in the flow rate. Similarly when the engine retards the temperature of the
cylinder decreases which will be sensed by the sensor and will operate the
valve.
ADVANTAGES OF INTELLIGENT COOLING SYSTEM
1) It will try to maintain the cylinder temperature
within the certain limit so that lubricating oil should not evaporate and hence
will prevent metal to metal contact.
2) It
will help to reduce the thermal stresses and hence cracking of piston cylinder.
3) Thermal
efficiency will improve.
4) It
will prevent the carbonization of oil since dealing with the optimum
temperature.
5) It
will prevent the corrosion of engine parts.
6) Mechanical
efficiency will improve.
7) Proper
vaporization of fuel will take place.
8) Excessive
cooling results in increased viscosity of lubricant oil and hence more friction
and will consume more fuel to overcome
the friction and hence results in decrease thermal efficiency. So, our system
will prevent the above factors.
9) During
starting, the engine takes some time to reach it's operating temperature and
hence it requires less or no coolant to be circulated around if so that it can
reach operating temperature easily.
10) Although
initial cost will be more but running cost will be less.
11) Less
maintenance will require.
Conclusion
We
have proposed an approach to implement fuzzy logic in an "Intelligent
Cooling System". Possible implementation
of the system and an approach is discussed along with its possible
advantages. The use of such system will solve the problems of technology
acceptance in India
Scope for
future work would concentrate on type of sensor's, valve opening mechanisms and
different coolants.
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