1. “GENERATION OF EMF FROM EXHAUST
HEAT”
PRESENTED BY
AUTHOR : P.KRISHNAKANTH
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2. ABSTRACT
We have developed a solution for using the exhaust
heat from the internal combustion engine (4 stroke ) to
charge the battery through a fundamental phenomenon
namely seebeck effect using thermo pile.
Here we use the exhaust manifold material of engine
(silencer) as hot junction whose temperature is nearly
2500C.
Due to this temperature difference of the thermo couple
thermo emf is produced by see beck effect.
This thermo emf is further amplified by means of a
primary and secondary coil arrangement and this
amplified voltage is given to the battery to get charged.
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3. INTRODUCTION
At present the heat energy, that is the temperature of the
engine exhaust gas has been wasted. But through our paper we are
adopting a basic thermoelectric process named as seebeck effect
where the temperature difference is equivalently converted into
electrical voltage.
OBJECTIVE
The objective of our paper is to provide a new idea of
producing electrical voltage from EGT (exhaust gas temperature)
Thus, the produced electrical voltage is used to charge the
battery. This is somewhat different from the present way in
which the voltage is produced. This is very cheap from the
economical point of view and reduces the exhaust gas
temperature.
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4. PRINCIPLE
Current flows in an electric circuit
made of two different conductors,
when the two junctions in the circuit
were kept at two different
temperatures.
This means that an emf is produced
across two junctions in the circuit
causing the flow of current. The two
junction circuit is called a thermo
couple and the emf produced is called
thermo electric emf or setback emf.
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5. The following is a selection from Seebeck 's series: bismuth (Bi),
nickel (Ni), cobalt (Co), palladium (Pd), platinum (Pt), copper (Cu),
manganese (Mn), mercury (Hg), lead (Pb), tin (Sn), gold (Au), silver
(Ag), zinc (Zn), cadmium (Cd), iron (Fe), antimony (Sb), tellurium (Te).
AUXILLARY COMPONENTS ADDED TO
ENGINE
•Induction coil.
•Constantan
•Lead
•Ceramic
5. Copper.
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7. WORKING
Here we are considering the four stroke petrol engines but the
same can be applied for the four stroke and also for the diesel
engines.
Normal exhaust temperature for four stroke engine is 250 C.
This is considered to be the hot junction.
The atmospheric temperature which is about to be 25 C is
considered as cold junction.
Hence the temperature difference between the 2 ends of the
thermo couple is about 225 C.
The hot and cold junctions are separated by means of an
insulating(ceramic )material.
This temperature difference between hot and cold junction is
been converted into voltage through seebeck effect.
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8. INVERSION
The voltage so obtained from a thermo couple is a direct
current voltage (dc voltage). In order to amplify it , we send it
through an induction coil.
But for the usage in an induction coil , we need to convert it
into an alternating current voltage (ac voltage).
For this process , we use a inverter through which the dc
voltage is converted to its equivalent ac voltage.
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9. INDUCTION COIL
Induction coil is used to check back flow of voltage from
battery to thermo pile
Hence through this we convert the wasted engine gas
temperature to some useful work.
With the help of the primary and secondary coil arrangement,
we can amplify the voltage obtained through the step-up
transformer action.
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10. CALCULATIONS
Here we considered the junction between the constantan and lead
and selecting the copper (CU) as the base material. Thus the
junction for the thermocouple has been achieved.
Some experimentally tested values:
Vseebeck = Vcopper-pb = 0.181mv
Vcopper-constantan = 4.436mv
Then the voltage produced is given by a standard equation,
VAB = αθ + (1/2 βθ^2).
Where,
A, B – Some two different metals.
θ – Temperature difference between hot and cold junction.
α, β – Thermo electric coefficients (material parameters for
constantan).
α = -38.1µv/ºc β = -0.089µv/ (ºc) ² for temperature range 200K and
400K.
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11. Here,
Let A be 60% of copper.
Let B be 50% of copper.
On substituting in above equation,
VAB = ((-38.1) ×106×200 )+ (.5×-.089×2002×10-6)
VAB = -9.4×10-3 volts.
If we use “n” number of couples in series,
V= n× (-9.4×10-3) volts.
If we use 50 series of couples means voltage can be increased by,
V= 50× (-9.4×10-3) volts
Vnet = - 0.47 volts.
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12. Power :
We know that the resistance offered by
one thermo-couple = 49 µ Ω
Resistance for a set of 50 thermo
couples = 50 × 49 µ Ω = 2.45 m Ω
R = 2.45 m Ω
V = -0.47 V
Power (P) = V²/R
P= ( -0.47)²/ (2.45 ×10-3 )
P = 90.16 Watts .
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15. To generate 6 volts we need to make 639 thermo couples
Insulation paint BLACK VELVET 738 Rs / l
Cost of copper 142m(1mm)=450 Rs(1775 pieces)
Cost of iron 190m(.5mm)=100 Rs(2375 pieces)
Length of one couple 8 cm
Cost of copper in thermo pile Rs162.25
Cost of iron in thermo pile Rs 26.95
Total cost for generating 6 volts =Rs189.2
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16. ADVANTAGES
Here the exhaust temperature is effectively used.
Serves as an alternate purpose of producing electric voltage.
Compatible in size so requires less provision.
Easy to operate.
Controls the regular charging of batteries.
CONCLUSION
Thus by our paper we have adapted a different way of utilizing the engine exhaust
gas temperature into some useful work without wasting it unnecessarily.
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