Experiments were carried out to study exhaust emissions of diesel engine with low heat rejection (LHR) combustion chamber with ceramic coated cylinder head [ceramic coating of thickness 500 microns was done on inside portion of cylinder head] with different operating conditions [normal temperature and pre–heated temperature] of waste fried vegetable oil based biodiesel with varied injector opening pressure and injection timing. Conventional engine (CE) showed deteriorated performance, while engine with LHR combustion chamber showed improved performance with biodiesel operation at manufacturer’s recommended injection timing of 27o bTDC (before top dead center) and injector opening pressure of 190 bar. The optimum injection timing was 31o bTDC for CE while it was 30o bTDC with engine with LHR combustion chamber with biodiesel operation. Smoke levels decreased, while nitrogen oxide levels increased with engine with LHR combustion chamber its optimized injection timing in comparison with pure diesel operation on CE.

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IJMET
© I A E M E
STUDIES ON EXHAUST EMISSIONS FROM CERAMIC COATED DIESEL
ENGINE WITH WASTE FRIED VEGETABLE OIL BASED BIODIESEL
R.P. Chowdary1, M.V.S. Murali Krishna2*, T. Kishen Kumar Reddy3
1, 2Mechanical Engineering Department, Chaitanya Bharathi Institute of Technology,
Gandipet, Hyderabad-500 075, Telangana, India
3Mechanical Engineering Department, College of Engineering, J.N.T. University,
Hyderabad -500 085, Telangana, India
27
ABSTRACT
Experiments were carried out to study exhaust emissions of diesel engine with low heat
rejection (LHR) combustion chamber with ceramic coated cylinder head [ceramic coating of
thickness 500 microns was done on inside portion of cylinder head] with different operating
conditions [normal temperature and pre–heated temperature] of waste fried vegetable oil based
biodiesel with varied injector opening pressure and injection timing. Conventional engine (CE)
showed deteriorated performance, while engine with LHR combustion chamber showed improved
performance with biodiesel operation at manufacturer’s recommended injection timing of 27o bTDC
(before top dead center) and injector opening pressure of 190 bar. The optimum injection timing was
31o bTDC for CE while it was 30o bTDC with engine with LHR combustion chamber with biodiesel
operation. Smoke levels decreased, while nitrogen oxide levels increased with engine with LHR
combustion chamber its optimized injection timing in comparison with pure diesel operation on CE.
Keywords: Biodiesel, Conventional Engine, Engine with Low Heat Rejection Combustion Chamber,
Exhaust Emissions.
1. INTRODUCTION
The rapid depletion of petroleum fuels and their ever increasing costs have lead to an
intensive search for alternate fuels. The most promising substitutes for petroleum fuels are alcohols
and vegetable oils. However, alcohols have low cetane number and hence engine modification is
necessary if they are to be used as fuels in diesel engines. That too, most of the alcohol produced in
India is diverted for Petro–Chemical industries. On the other hand, vegetable oils have high cetane

2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 27-35 © IAEME
number, comparable to diesel fuel. When Rudolf Diesel first invented the diesel engine, about a
century ago, he demonstrated the principle by employing peanut oil and hinted that vegetable oil
would be the future fuel in diesel engine. [1].However, U.S. Department of Energy has stated that,
“Raw or refined vegetable oil, or recycled greases that have not been processed into biodiesel, are
not biodiesel and should be avoided, as they cause problems in a number of areas: (i) piston ring
sticking; (ii) injector and combustion chamber deposits; (iii) fuel system deposits; (iv) reduced
power; (v) reduced fuel economy and(vi) increased exhaust emissions [2]. The above problem could
be solved once crude vegetable oil was converted chemically (esterified) into biodiesel.
Investigations were carried out on CE with biodiesel and reported that the performance was
comparable, decreased smoke levels and increased marginally nitrogen oxide (NOx) levels [3–7].
The drawbacks of the biodiesel call for hot combustion chamber provided by engine with low heat
rejection (LHR) combustion chamber.
These prospects of improving the design and performance have generated impetus to active
research on adiabatic or more appropriately, low heat rejection (LHR) or insulated engines. The
concept of engine with LHR combustion chamber is to prevent the heat flow to the coolant by
providing thermal insulation in the path of the heat flow to the coolant. Engine with LHR
combustion chambers were classified depending on degree of insulation as low grade, medium grade
and high grade insulated engines. Low grade insulated engines provide thermal resistance by means
of coatings with low thermal conductivity materials like ceramics on piston, liner, cylinder head and
other engine components, while medium LHR combustion chambers consisted of air gap insulated
piston with low thermal conductivity material superni (an alloy of nickel) crown and air gap
insulated liner with superni insert and high grade engine with LHR combustion chambers was the
combination of low grade combustion chamber and medium grade combustion chamber.
Investigations were carried out on low grade LHR combustion chamber with biodiesel and
concluded that performance improved and exhaust emissions of smoke decreased with biodiesel
operation on Engine with LHR combustion chamber, however, they increased NOx emissions. [8–9]
The present paper attempted to evaluate the performance of biodiesel with engine with LHR
combustion chamber, which contained ceramic coated cylinder head with different operating
conditions of biodiesel with varying engine parameters of change of injector opening pressure and
injection timing and compared with CE with pure diesel operation at recommended injection timing
and injector opening pressure.
28
2. MATERIAL AND METHOD
The chemical conversion of esterification reduced viscosity four fold. Palm oil based waste
fried vegetable oil contains up to 20 % (wt.) free fatty acids [10] The methyl ester was produced by
chemically reacting the crude vegetable oil with an alcohol (methyl), in the presence of a catalyst
(KOH). A two-stage process was used for the esterification [11–12] of the waste fried vegetable oil.
The first stage (acid-catalyzed) of the process is to reduce the free fatty acids (FFA) content in waste
fried vegetable oil by esterification with methanol (99% pure) and acid catalyst (sulfuric acid-98%
pure) in one hour time of reaction at 55° C. In the second stage (alkali-catalyzed), the triglyceride
portion of the waste fried vegetable oil reacts with methanol and base catalyst (sodium hydroxide-
99% pure), in one hour time of reaction at 65°C, to form methyl ester and glycerol, to remove un-reacted
methoxide present in raw methyl ester. It is purified by the process of water washing with
air-bubbling. The methyl ester (or biodiesel) produced from waste fried vegetable oil was known as
waste fried vegetable oil based biodiesel (BD). The esters were used in present study. Esterified
vegetable oil or biodiesel was heated to a temperature (PT, 90o C) where its viscosity was made equal
to that of diesel fuel. The properties of the test fuels used in this work were presented in Table-1.

3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 27-35 © IAEME
Table 1: Properties of test fuels
Partially stabilized zirconium (PSZ) of thickness 500 microns was coated on inside portion of
cylinder head with spray coating. The schematic sketch of the experimental setup used for the
investigations of engine with LHR combustion chamber with biodiesel is shown in Fig.1.
1. Engine, 2. Electical Dynamo meter, 3. Load Box, 4. Orifice meter, 5. U-tube water
manometer, 6. Air box, 7. Fuel tank, 8, Pre-heater, 9. Burette, 10. Exhaust gas temperature
indicator, 11. AVL Smoke meter, 12. Netel Chromatograph NOx Analyzer, 13. Outlet jacket
water temperature indicator, 14. Outlet-jacket water flow meter.
Figure 1: Experimental Set-up
CE had an aluminum alloy piston with a bore of 80 mm and a stroke of 110mm. The rated
output of the engine was 3.68 kW at a rate speed of 1500 rpm. The compression ratio was 16:1 and
manufacturer’s recommended injection timing and injection pressures were 27o bTDC and 190 bar
.The fuel injector had 3-holes of size 0.25-mm. The combustion chamber consisted of a direct
injection type with no special arrangement for swirling motion of air. The engine was connected to
electric dynamometer for measuring its brake power. Burette method was used for finding fuel
consumption of the engine. Air-consumption of the engine was measured by air-box method. The
naturally aspirated engine was provided with water-cooling system in which inlet temperature of
water was maintained at 80o C by adjusting the water flow rate. Engine oil was provided with a
pressure feed system. No temperature control was incorporated, for measuring the lube oil
temperature. Copper shims of suitable size were provided in between the pump body and the engine
frame, to vary the injection timing and its effect on the performance of the engine was studied, along
with the change of injection pressures from 190 bar to 270 bar (in steps of 40 bar) using nozzle
29
Test Fuel Viscosity at
25oC
(Centi-poise)
Specific
gravity at
25 oC
Cetane
number
Calorific
value
(kJ/kg)
Diesel 12.5 0.84 55 42000
Biodiesel (BD) 48 0.86 55 35500
ASTM Standard ASTM D 445 ASTM D
4809
ASTM D
613
ASTM D
4809

4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 27-35 © IAEME
testing device. The maximum injector opening pressure was restricted to 270 bar due to practical
difficulties involved. Exhaust gas temperature (EGT) was measured with thermocouples made of
iron and iron-constantan attached to exhaust gas temperature indictor. Exhaust emissions of smoke
and nitrogen oxide (NOx were recorded by AVL smoke meter and Netel Chromatograph NOx
analyzer at various values of brake mean effective pressure (BMEP). The accuracy of the
instrumentation was 1%. The test fuels used in the experimentation were pure diesel and biodiesel.
The different operating conditions of the biodiesel were normal temperature and preheated
temperature. The various configuration used in the investigations were conventional engine (CE) and
engine with LHR combustion chamber.
30
3. RESULTS AND DISCUSSIONS
3.1 Performance Parameters
Curves from Fig. 2 indicate that brake thermal efficiency (BTE) increased up to 80% of the
peak load operation due to increase in fuel efficiency and beyond this load it decreased due to
decrease of air-fuel ratio and volumetric efficiency with test fuels. At recommended injection timing,
conventional engine (CE) with biodiesel showed the comparable performance for entire load range
when compared with the pure diesel operation on CE. This may be due to the difference of viscosity
between the diesel and biodiesel. BTE increased with the advanced injection timing with CE with the
biodiesel at all loads, when compared with CE at the recommended injection timing and pressure.
This was due to initiation of combustion at earlier period and efficient combustion with increase of
air entrainment in fuel spray giving higher BTE. BTE increased at all loads when the injection timing
was advanced to 31o bTDC in the CE at the normal temperature of biodiesel. This could be attributed
to its longer ignition delay and combustion duration. BTE increased at all loads when the injection
timing was advanced to 31o bTDC in CE, at the preheated temperature of biodiesel also. That, too,
the performance improved further with CE with the preheated biodiesel for entire load range when
compared with normal biodiesel. Preheating of the biodiesel reduced the viscosity, which improved
the spray characteristics of the oil and reduced the impingement of the fuel spray on combustion
chamber walls, causing efficient combustion thus improving BTE
Fig.2: Variation of brake thermal efficiency (BTE) with brake mean effective pressure (BMEP)
in conventional engine (CE) at different injection timings with biodiesel (BD) operation
.

5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 27-35 © IAEME
Curves in Fig. 3 indicate that engine with LHR combustion chamber with biodiesel showed
the improvement in the performance for entire load range compared with CE with pure diesel
operation. High cylinder temperatures helped in better evaporation and faster combustion of the fuel
injected into the combustion chamber.

6. Fig 3: Variation of brake thermal efficiency (BTE) with brake mean effective pressure (BMEP)
in engine with LHR combustion chamber at different injection timings with biodiesel
(BD) operation
Reduction of ignition delay of the biodiesel in the hot environment of the Engine with LHR
combustion chamber improved heat release rates and efficient energy utilization. Preheating of
biodiesel improved performance further in LHR version of the engine. The optimum injection timing
was found to be 30o bTDC with Engine with LHR combustion chamber with normal biodiesel as
well as preheated biodiesel. Since the hot combustion chamber of engine with LHR combustion
chamber reduced ignition delay and combustion duration and hence the optimum injection timing
was obtained earlier with engine with LHR combustion chamber when compared with CE with the
biodiesel operation.
Injector opening pressure was varied from 190 bar to 270 bar to improve the spray
characteristics and atomization of the biodiesel and injection timing was advanced from 27 to 31o
bTDC for CE and engine with LHR combustion chamber.
31
3.2 Exhaust Emissions
From Fig.4, it is observed that lower levels of smoke was observed with both versions of the
combustion chamber with test fuels up to 80% of the full load operation, an beyond that it they
increased drastically. During the first part, the smoke level was more or less constant, as there was
always excess air present.

7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 27-35 © IAEME
Fig.4: Variation of smoke intensity in Hartridge Smoke Unit (HSU) with brake mean effective
pressure (BMEP) in conventional engine (CE) and engine with LHR combustion chamber
at recommend injection timing and optimized injection timings with biodiesel (BD)
operation
However, in the higher load range there was an abrupt rise in smoke levels due to less
available oxygen, causing the decrease of air–fuel ratio, leading to incomplete combustion,
producing more soot density.
The variation of smoke levels with brake mean effective pressure typically showed inverted
‘L’ shaped behavior due to the pre-dominance of hydrocarbons in their composition at light load and
of carbon at high load. It is observed from the Figure, drastic increase of smoke levels was observed
at the full load operation in CE at different operating conditions of the biodiesel, compared with pure
diesel operation on CE. This was due to the higher value of the ratio of C/H of biodiesel (0.6) when
compared with pure diesel (0.45). The increase of smoke levels was also due to decrease of air-fuel
ratios and VE with biodiesel compared with pure diesel operation. Smoke levels were related to the
density of the fuel. Since biodiesel has higher density compared to diesel fuels, smoke levels were
higher with biodiesel. However, engine with LHR combustion chamber marginally reduced smoke
levels due to efficient combustion and less amount of fuel accumulation on the hot combustion
chamber walls of the engine with LHR combustion chamber at different operating conditions of the
biodiesel compared with the CE. Density influences the fuel injection system. Decreasing the fuel
density tends to increase spray dispersion and spray penetration. Preheating of the biodiesel reduced
smoke levels in both versions of the engine, when compared with normal temperature of the
biodiesel. This was due to i) the reduction of density of the biodiesel, as density was directly
proportional to smoke levels, ii) the reduction of the diffusion combustion proportion in CE with the
preheated biodiesel, iii) the reduction of the viscosity of the biodiesel, with which the fuel spray does
not impinge on the combustion chamber walls of lower temperatures rather than it directed into the
combustion chamber.
From Table.2, it is noticed that smoke levels decreased with increase of injection timings and
with increase of injection pressure, in both versions of the combustion chamber, with different
operating conditions of the biodiesel. This was due to improvement in the fuel spray characteristics
at higher injector opening pressure and increase of air entrainment, at the advanced injection timings,
causing lower smoke levels.
32

8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 27-35 © IAEME
Table.2: Data of Smoke levels in Hartridge smoke unit (HSU) at full load operation
33
IT
Test
Fuel
Smoke Levels (HSU)
Conventional Engine (CE)
Engine with LHR combustion
chamber
Injector opening pressure(Bar) Injector opening pressure(Bar)
190 230 270 190 230 270
NT PT NT PT NT PT NT PT NT PT NT PT
27
DF 48 -- 38 -- 34 -- 60 -- 55 -- 50 --
BD 60 55 55 50 50 45 55 50 50 45 45 40
30 BD 55 50 50 45 45 40 40 35 35 30 30 25
31 BD 50 45 55 45 60 55 -- -- -- -- -- --
(IT= Injection timing (o bTDC), NT=Normal temperature, PT=Preheated temperature)
From Fig.5, it is evident that nitrogen oxide levels (NOx) levels were lower in CE while they
were higher in engine with LHR combustion chamber with biodiesel at all loads when compared
with diesel operation on CE. This was due to lower heat release rate because of high duration of
combustion causing lower gas temperatures with the biodiesel on CE, which reduced NOx levels.
Increase of combustion temperatures with the faster combustion and improved heat release rates in
Engine with LHR combustion chamber caused higher NOx levels.
From Table.3, it is noticed that NOx levels increased with the advancing of the injection
timing in CE with different operating conditions of biodiesel. Residence time and availability of
oxygen had increased, when the injection timing was advanced with the biodiesel operation, which
caused higher NOx levels in CE. However, NOx levels decreased with increase of injector opening
pressure in CE. With the increase of injection pressure, fuel droplets penetrate and find oxygen
counterpart easily. Turbulence of the fuel spray increased the spread of the droplets which caused
decrease of gas temperatures marginally thus leading to decrease in NOx levels.
Fig.5: Variation of NOx levels with BMEP in conventional engine (CE) and engine with LHR
combustion chamber at recommend injection timing and optimized injection timings with
biodiesel operation

9. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 27-35 © IAEME
Marginal decrease of NOx levels was observed in engine with LHR combustion chamber
with biodiesel, due to decrease of combustion temperatures, which was evident from the fact that
thermal efficiency increased in engine with LHR combustion chamber due to the reason sensible gas
energy was converted into actual work in engine with LHR combustion chamber, when the injection
timing was advanced and with increase of injector opening pressure.
Table.3: Data of NOx levels at full load operation
34
IT
Test
Fuel
NOx levels (ppm)
Conventional Engine (CE) Engine with LHR combustion chamber
Injector opening pressure(Bar) Injector opening pressure(Bar)
190 230 270 190 230 270
NT PT NT PT NT PT NT PT NT PT NT PT
27
DF 850 ---- 810 ---- 770 --- 1200 -- 1150 -- 1100 ---
BD 800 750 850 800 900 850 1250 1200 1200 1150 1150 1100
30 BD - - - - - - 1200 1150 1150 1100 1100 1050
31 BD 1000 950 1050 1000 1100 1050 -- -- -- -- - --
However, increase of injector opening pressure with CE, increased NOx emissions. This was
due to increase of gas temperatures. As expected, preheating of the biodiesel decreased NOx levels
in both versions of the combustion chamber when compared with the normal biodiesel. This was due
to improved air fuel ratios and decrease of combustion temperatures leading to decrease NOx
emissions in the CE and decrease of combustion temperatures in the engine with LHR combustion
chamber with the improvement in air-fuel ratios leading to decrease NOx levels in Engine with LHR
combustion chamber.
4. SUMMARY
CE with biodiesel operation showed the optimum injection timing at 31o bTDC, while it was
30o bTDC with Engine with LHR combustion chamber at an injector opening pressure of 190 bar. At
recommended injection timing, smoke levels increased by 25% with CE and 15% with engine with
LHR combustion chamber, while at optimum injection timing, smoke levels were comparable with
CE and decreased by 17% with engine with LHR combustion chamber with biodiesel operation
when compared with CE at recommended injection timing. NOx levels decreased by 5% with CE and
increased by 47% with engine with LHR combustion chamber, while at optimum injection timing,
NOx levels increased by 18% with CE and 41% with engine with LHR combustion chamber with
biodiesel operation when compared with CE with pure diesel operation at recommended injection
timing. Increase of injector opening pressure decreased pollution levels with engine with LHR
combustion chamber.
4.1 Future Scope of Work
As engine with LHR combustion chamber increased NOx emissions, they can be reduced
with selective catalytic reduction technique, using lanthanum ion exchanged zeolite (catalyst-A) and
urea infused lanthanum ion exchanged zeolite (catalyst-B) with different versions of the engine at
peak load operation of the engine.[13]

10. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print),
ISSN 0976 – 6359(Online), Volume 5, Issue 7, July (2014), pp. 27-35 © IAEME
35
ACKNOWLEDGMENTS
Authors thank authorities of Chaitanya Bharathi Institute of Technology, Hyderabad for
providing facilities for carrying out research work. Financial assistance provided by All India
Council for Technical Education (AICTE), New Delhi was greatly acknowledged.
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