Experiments were conducted to evaluate the performance of two stroke single cylinder, spark ignition (SI) engine, with alcohol blended gasoline (80% gasoline, 20% methanol, by volume) having copper coated engine [CCE, copper-(thickness, 300 μ) coated on piston crown] and compared with
conventional SI engine (CE) with pure gasoline operation. Performance parameters (brake thermal efficiency, exhaust gas temperature and volumetric efficiency) were determined with different values of brake mean effective pressure of the engine Copper coated engine (CCE) with methanol blended
gasoline considerably improved the performance in comparison with CE with pure gasoline operation. CCE with methanol blended gasoline increased the brake thermal efficiency, decreased the exhaust gas temperature and
increased the volumetric efficiency.
THERMAL ANALYSIS OF MODIFIED COMBUSTION CHAMBER OF SPARK IGNITION ENGINEIAEME Publication
Ähnlich wie COMPARATIVE STUDIES ON PERFORMANCE PARAMETERS OF TWO STROKE SPARK IGNITION ENGINE WITH COPPER COATED PISTON WITH METHANOL BLENDED GASOLINE (20)
2. Dr. K. Kishor
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The individual transport which consumes petrol heavily and the fact of fast
depletion of fossil fuels, the alternate fuel research has assumed importance. Because
of their compatible properties to gasoline fuels, alcohols are considered to be the
suitable substitutes for use in SI engines. No major engine design modification is
needed, if small quantities of alcohols are blended with gasoline. The change in fuel
composition like blending of petrol with methanol is one of the methods adopted to
improve the performance of the engine.
Sane et al. [1] carried out the investigations on Bajaj 150cc scooter engine using
various blends of ethyl alcohol and methyl alcohol with petrol and also pure alcohol.
They reported that there was an overall improvement in engine performance.
However, some modifications were required to be incorporated to run the engine with
pure alcohol. Being a good conductor of heat that promotes combustion, copper
coating on piston crown [2] increased combustion stabilization and improved the
performance of the engine. Maji et al. [3] conducted an experiment and found that,
methanol blended gasoline (90% methanol +10% gasoline) when used as a fuel in a
two-stroke si engine gave rise to abnormal combustion even at a low compression
ratio. Pankhaniya et al. [4] conducted an experiment to study the effect of methyl
alcohol blend when being used as fuel in an SI engine. These performance tests were
conducted at an engine speed of 2000 rpm and variable load condition, using various
blends of M0 to M20 fuels and reported improved performance. Murali Krishna et al.
[5] evaluated the performance of four-stroke, single cylinder SI engine. With methyl
alcohol blend in various configurations of the engine, BTE was found to be higher. In
comparison with base engine the performance of catalytically activated engine was
found to be improved with experimental fuels in different versions of the engine.
However these investigations were carried out on four stroke SI engine.
The present paper evaluated the performance of two stroke CCE with methanol
blended gasoline (gasoline-80%, methanol- 20% by volume), which includes
determining performance parameters at various values of BMEP and compared with
CE with pure gasoline operation. An increase of 22% in BTE, a decrease of 32% in
EGT and an increase of 4% in VE were observed with the use of alcohol gasoline
blend in CCE over CE with pure gasoline operation.
2. MATERIALS AND METHODS
This section deals with fabrication of copper coated engine, description of
experimental set up and definition of used values.
In the copper coated engine, by flame spraying technique, a high thermal
conductive catalytic material like copper was coated on the top surface of piston
crown. For 100µ thickness, nickel-cobalt-chromium bond coating was sprayed. On
this coating, for another 300µ thickness, an alloy of copper (89.5%), aluminium
(9.5%) and iron (1%) was coated with a METCO (Trade name of the company) flame
spray gun. The bond strength of the coating was so high that it does not wear off even
after operating it for 50 hrs continuously [2], [6].
3. Comparative Studies on Performance Parameters of Two Stroke Spark Ignition Engine with
Copper Coated Piston with Methanol Blended Gasoline
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Plate.1 shows the photographic view of copper coated piston.
Plate 1 Photographic view of copper coated piston
Figure 1 shows the schematic diagram of the experimental set up that was
employed to evaluate the performance parameters.
1. Engine, 2.Electrical swinging field dynamometer, 3. Loading arrangement, 4.
Fuel tank, 5.Torque indicator/controller sensor, 6. Fuel rate indicator sensor, 7. Hot
wire gas flow indicator, 8. Multi- channel temperature indicator, 9. Speed indicator,
10. Air flow indicator, 11. Exhaust gas temperature indicator, 12. Mains ON 13.
Engine ON/OFF switch, 14. Mains OFF, 15. Motor/Generator option switch, 16.
Heater controller, 17. Speed indicator, 18. Directional valve, 19. Air compressor, 20.
Rotometer, 21. Heater, 22. Air chamber, 23. Catalytic chamber, 24. CO/HC analyzer,
25. Filter, 26. Round bottom flasks containing DNPH solution,
Figure 1 Schematic diagram of the experimental set up
An air-cooled single-cylinder 2.2 kW BP two-stroke SI engine with a rated speed
of 3000 rpm was provided with an electrical swinging field dynamometer for the
measurement of brake power (BP). The fuel consumption, speed, torque, air flow rate
and exhaust gas temperature were measured with digital electronic sensors. A
pressure-feed system provides the engine oil.
Performance parameters of brake thermal efficiency (BTE), exhaust gas
temperature (EGT) and volumetric efficiency (VE) are evaluated at different values of
brake mean effective pressure (BMEP) of the engine. Brake specific energy
consumption was determined at full load operation of the engine. Experiments were
carried out on CE with pure gasoline and copper coated engine (CCE) with methanol
blended gasoline (gasoline-80%, methanol-20% by volume].
4. Dr. K. Kishor
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2.1. Definitions of used values
Brake mean effective pressure: It is defined as specific torque of the engine. Its unit is
bar.
(1)
BP =Brake power of the engine in kW;
BMEP= Brake mean effective pressure of the engine in bar
L= Stroke of the piston in m, A= Area of the piston = (πD2
)/4 Where D= Bore of
the cylinder in m, n= Effective number of power cycles= N, where N=Speed of the
engine = 3000 rpm, k = no. of cylinders = 1
Brake thermal efficiency (BTE); It is the ratio of brake power of the engine to the
energy supplied to the engine. Brake power was measured with dynamometer. Energy
supplied to the engine is the product of rate of fuel consumed (mf) and calorific value
(cv) of the fuel. Higher the efficiency betters the performance of the engine is.
(2)
Brake specific energy consumption (BSEC): It is measured at full load operation
of the engine. Lesser the value, the better the performance of the engine is. It is
defined as energy consumed by the engine in producing 1 kW brake power. When
different fuels having different properties are tested in engine, brake specific fuel
consumption is not the criteria to evaluate the performance of the engine. Peak BTE
and BSEC at full load are important parameters to be considered to evaluate the
performance of the engine.
(3)
Volumetric efficiency: It is the ratio of the volume of air drawn into a cylinder to
the piston displacement.
Calculation of actual discharge of air: By means of water tube manometer and an
orifice flow meter, head of air (ha) can be calculated. Velocity of air (Va) can be
calculated using the formula
(4) ;
(5) Actual discharge of air = , where a= area of an orifice flow meter, cd =
Coefficient of discharge.
3. RESULTS AND DISCUSSION
This section deals with i) variation of brake thermal efficiency, exhaust gas
temperature, volumetric efficiency with brake mean effective pressure with test fuels
with different versions of the engine, ii) variation of brake specific energy
consumption at full load operation with test fuels with CE and CCE, iii). Variation of
EGT with brake mean effective pressure (BMEP) of the engine, and IV) variation of
VE with brake mean effective pressure (BMEP) determined at full load operation of
the engine.
5. Comparative Studies on Performance Parameters of Two Stroke Spark Ignition Engine with
Copper Coated Piston with Methanol Blended Gasoline
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3.1. Performance Parameters
Figure.2 shows the variation of brake thermal efficiency (BTE) with brake mean
effective pressure (BMEP) in CE with pure gasoline and CCE with methanol blended
gasoline at a compression ratio of 7.5:1 and speed of 3000 rpm.
Figure 2 Variation of BTE with BMEP in CE and CCE with test fuels
From the Fig.2 it was noticed that, BTE increased up to 80% of peak load. Beyond
that load, with increase of BMEP, the efficiency was decreased for both
configurations of the engine with test fuels, because of increase of fuel conversion
efficiency up to 80% of peak load and beyond that load, performance deteriorated
with increase of friction power. With methanol blend, higher BTE was noticed over
pure gasoline at all loads due to lower stoichiometric air requirement of methanol
blended gasoline over pure gasoline operation.
Similar trends were observed by Murali Krishna [7].
Figure.3 presents bar charts showing the variation of brake specific energy
consumption (BSEC) at full load operation of CE with pure gasoline and CCE with
methanol blended gasoline operation.
Figure 3 Bar chart showing the variation of BSEC with test fuels in CE and CCE
Brake specific energy consumption (BSEC) was defined as the energy consumed
by the engine in producing 1 kW brake power. It was evident from the Figure-3 that,
BSEC was lower at full load operation of copper coated engine with methanol blend
in comparison with the CE. When compared with pure gasoline, the mass flow rate of
burning of methyl alcohol was lower. Therefore methyl alcohol blend consumes less
energy when compared with pure gasoline, as the consumption of energy depends on
the consumption of mass of fuel and heating value of the fuel.
Figure.4 shows the variation of exhaust gas temperature (EGT) with BMEP in
different versions of the engine with test fuels at a speed of 3000 rpm and
6. Dr. K. Kishor
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compression ratio of 7.5:1, which indicated that EGT increased with an increase of
BMEP. This was due to increase of fuel consumption with load.
EGT was found to be less with methanol blend in comparison with the pure
gasoline at different operational loads of the CE and CCE. This was due to extended
compression stroke which leads to a decrease in the value of EGT. Indirectly there
was more transfer of work from the piston to the gases. Since methyl alcohol has high
latent heat of evaporation, it absorbs more amount of heat from combustion reactions
causing reduction of EGT when compared with CE. The heat thus produced was
diverted in increasing BTE for CCE causing reduction in EGT in comparison with the
base engine. Hence CCE was more suitable for methyl alcohol blend.
Figure 4 Variation of EGT with BMEP in CE and CCE with experimental fuels
Fig.5 shows the variation of volumetric efficiency (VE) with BMEP with test
fuels at a speed of 3000 rpm and a compression ratio of 7.5:1, which indicated that
VE decreased with increase of BMEP due to increase of gas temperature [7].
Figure 5 Variation of VE with BMEP in CE and CCE with experimental fuels
From the Fig.5 it was noticed that, as BMEP increases VE reduces with different
configurations of the engine with experimental fuels at all loads. This was due to
increase of temperature with the increase of fuel consumption. When compared with
the base engine and both experimental fuels, catalytic coated engine exhibited higher
VE due to the decrease of residual charge and deposits in its combustion chamber.
The variations in the volumetric efficiencies are very small. However, they are to be
calculated to determine the utility of air in improving thermal efficiency. Similar
trends were reported by Dhandapani [6]. Methyl alcohol blend increased VE in
comparison with the base fuel in both the configurations of the engine, as temperature
of air was decreased with high latent heat of methyl alcohol leading to an increase in
the mass of air.
4. CONCLUSIONS
1. Brake Thermal efficiency (BTE) increased by 22% with alcohol blended gasoline
operation in CCE over pure gasoline operation in CE.
7. Comparative Studies on Performance Parameters of Two Stroke Spark Ignition Engine with
Copper Coated Piston with Methanol Blended Gasoline
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2. Exhaust gas temperature decreased by 32% with alcohol blended gasoline operation
in CCCC over pure gasoline operation in CE.
3. Volumetric efficiency increased by 4% with alcohol blended gasoline operation in
CCCC over pure gasoline operation in CE.
4. CCE with alcohol blended gasoline showed lower value of BSEC in comparison to
CE with pure gasoline operation.
4.1. Research findings and future scope of work
Investigations on evaluation of performance parameters with copper coating on top
surface of piston were systematically investigated. Copper coating can be done on
inner surface of cylinder head to improve the performance further.
ACKNOWLEDGEMENTS
Authors thank authorities of Chaitanya Bharathi Institute of Technology, Hyderabad
for facilities provided. Financial assistance from Andhra Pradesh Council of Science
and Technology (APCOST), Hyderabad, is greatly acknowledged. Authors sincerely
thank authorities of M/S Sai Surface Coating (P) Limited, Patancheru, Hyderabad, for
extending the cooperation in coating the components of the SI engine.
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