Experimental investigation of mullite coated diesel engine

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International Journal of Mechanical Engineering and Technology (IJMET)
Volume 6, Issue 11, Nov 2015, pp. 132-144, Article ID: IJMET_06_11_016
Available online at
http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=6&IType=11
ISSN Print: 0976-6340 and ISSN Online: 0976-6359
© IAEME Publication
AN EXPERIMENTAL INVESTIGATION ON
ENGINE PERFORMANCE OF A LOW HEAT
REJECTION (MULLITE COATED) SINGLE
CYLINDER DIESEL ENGINE WITH AND
WITHOUT TURBOCHARGER
Parvezalam Shaikh and S.P. Yeole
Department of Mechanical Engineering,
P.R Pote (Patil) Group of Educational Institutions, Amravati, India
ABSTRACT
In Present Investigation at the first stage, experiments were conducted on
baseline (Conventional) engine and hence combustion and emission
Parameters were recorded. At second stage Mullite, which is a compound of
SiO2 and Al2O3 with composition 3Al2O3.2SiO2 (Aluminium oxide 60% and
Silicon dioxide 40%), was used as a (TBC) thermal barrier coating material.
The piston crown, cylinder valves and cylinder head of diesel engine were
coated with a 0.5 mm thickness of 3Al2O3.2SiO2 (mullite) over a 150-µm
thickness of Nickel Chrome Aluminium Yttrium (NiCrAlY) bond coat using
plasma spray technique to achieve less heat loss and combustion and emission
Parameters were recorded for LHR engine. The operational parameters i.e.
air-fuel ratio and engine speed conditions were maintained constant for both
conventional as well as Low Heat rejection engines. In Third stage, the
experiments were conducted on turbocharged low heat rejection (LHR) single
cylinder diesel engine with advanced injection timing. The main objective of
the study was to evaluate combustion parameters and overall engine
performance of these engines. The experiments were carried out for various
loads via. 0%, 25%, 50%, 75% and maximum loads, then the results were
compared. The evaluation of experimental data showed that the brake thermal
efficiency and brake power values of Low heat rejection (LHR) engine were
slightly higher than that of conventional diesel engine. It was also found that
heat lost to coolant is reduced and there is increase in energy of exhaust gases
for Low heat rejection (LHR) engine when compared with the conventional
single cylinder diesel engine. Emission characteristics such as NOx are
increased and there is decrease in HC and CO in case of LHR Engine when
compared with conventional engine. Whereas Low heat rejection (LHR)
engine with turbocharger showed deterioration in the engine performance
when compared with Low heat rejection (LHR) diesel engine without
turbocharger.

http://www.iaeme.com/IJMET.asp 133 editor@iaeme.com
Keywords: Baseline Engine, LHR, Mullite, TBC, Turbocharger.
Cite this Article: Parvezalam Shaikh and S.P. Yeole. An Experimental
Investigation on Engine Performance of A Low Heat Rejection (Mullite
Coated) Single Cylinder Diesel Engine with and without Turbocharger,
International Journal of Mechanical Engineering and Technology, 6(11),
2015, pp. 132-144.
http://www.iaeme.com/currentissue.asp?JType=IJMET&VType=6&IType=11
1. INTRODUCTION
Because of increasing requirements of governments and customers, car manufacturers
and researchers are always trying to reduce fuel consumption while maintaining the
best engine performance. The insulation of the combustion chamber surfaces strongly
influences the performance and exhaust emissions of direct injection diesel engines.
Thermal barrier coatings (TBCs) have been a topic of great scientific interest
worldwide for several decades. They have been used for engine components, in
turbines and aircraft engines in order to achieve improved engine performance and
fuel efficiency by increasing the actual temperature of engine operation.
In the present investigation, Mullite, which is a compound of SiO2 and Al2O3 with
composition 3Al2O3.2SiO2 (Al2O3= 60%, SiO2= 40%), is used as a thermal barrier
coating material for single cylinder diesel engine. Mullite is an important ceramic
material because of its low density, high thermal stability, stability in severe chemical
environments, low thermal conductivity and favorable strength and creep behavior. It
is a compound of SiO2 and Al2O3 with composition 3Al2O3.2SiO2. Compared with
YSZ, mullite has a much lower thermal expansion coefficient and higher thermal
conductivity, and is much more oxygen-resistant than YSZ. Yttria-stabilized zirconia
(YSZ) has emerged as the preferred TBC material due to its low thermal conductivity
(~1 W/mK) over a range of temperatures. The ceramic, mullite, though, has the
advantage of having reduced thermally activated time-dependent behavior compared
to YSZ [1]
. Diesel engine rig tests performed in the past have demonstrated that
mullite coatings on pistons experienced decreased surface cracking and increased life
compared to YSZ coatings on pistons [2]
. For the applications such as diesel engines
where the surface temperatures are lower than those encountered in gas turbines and
where the temperature variations across the coating are large, mullite is an excellent
alternative to zirconia as a TBC material. Life of Mullite coating is more than the
zirconia coating tested under same condition. Mullite is most promising coating
material for the SiC substrate because their thermal expansion coefficients are similar.
The objective of this investigation have been also to evaluate the effect of thin
mullite coating on engine exhaust emissions for both the LHR and conventionally
cooled diesel engines.
In the present research work, the concept of an adiabatic turbo compound diesel
engine has been introduced. The pulse turbocharger (suits to the specification of given
diesel engine), which utilized the kinetic energy of exhaust gases of low heat rejection
(LHR) diesel engine, has been used for experimentation. The objective of this
investigation has been to study the effect of pulse turbocharger on the engine
performance parameters of low heat rejection (LHR) diesel engine. The thermal
barrier coatings (TBCs) enable to lower temperature (Fig.2.1) (at approx. 170°C) of
operating elements, exposed to creeping, in a hot section of gas turbine (e. g.
combustion chambers and directing and rotating blades) to a range, which enables to
operate for a long time in conditions of high temperature influence and prolongs

An Experimental Investigation on Engine Performance of A Low Heat Rejection (Mullite
Coated) Single Cylinder Diesel Engine with and without Turbocharger
operation of them even three or four times, simultaneously reducing consumption of
fuel [3]
.
In an experimental study performed by A. Gilbert et al [4]
, the thermal shock
behavior of three coating architectures, (i) monolithic YSZ, (ii) monolithic mullite
and (iii) a YSZ–mullite composite with 40% YSZ and 60% mullite by volume, was
compared. All three coatings had a nominal thickness of 1 mm. It was found that at
similar surface temperatures, the YSZ coatings developed the longest surface and
horizontal cracks while the mullite coatings developed the shortest cracks.
A major breakthrough in diesel engine technology has been achieved by the
pioneering work done by Kamo and Bryzik [5-6]
. As a result of their pioneering efforts
in the area of adiabatic engine technology, many governments, industries and
academic sources worldwide have begun to work in this area. An improvement of 7%
in the performance was observed [6]
.
Hejwowski and Weronski [7]
showed that brake specific fuel consumption (BSFC)
was 15–20 per cent lower in the LHR engine. A significant improvement in engine
performance was found at high engine speeds, power was increased by 8 per cent and
brake torque by 6 per cent. Exhaust gas temperature was found to be 200 K higher
than in an engine with metal pistons.
The investigation undertaken by R.H. Thring [8]
using ceramic coated single-
cylinder DI diesel engine reported improvement in fuel economy of about 7 % in
Turbocharged (TC) engine and about 15 % in Turbocompounded (TCO) engine. It
also reported 80% reduction of smoke and 50% reduction of HC and CO emissions,
but NOx emissions increased by 15%.
2. EXPERIMENTAL SETUP
A four stroke, direct injected, water-cooled, single cylinder, naturally aspirated diesel
engine was used for investigation. Details of the engine specifications are given in
Table 1.
Table 1 Engine specifications
Engine type Kirloskar AV1, DI
Stroke number 4
Cylinder number 1
Stroke (mm) 110
Compression ratio 16.5:1
Maximum engine power (KW) 3.7
Maximum engine speed (rpm) 1500
Specific fuel consumption (g/Kwh) 245

Figure 1 Experimental Set up
The first stage tests were performed at different engine loads for conventional
engine. The experiments were conducted at five load levels, viz. 0, 25, 50, 75% of full
load and full load. The required engine load percentage was adjusted by using the
eddy current dynamometer. At each of these loads, engine performance and
combustion characteristics were recorded.
The second stage tests were conducted on engine when combustion chamber
insulation was applied. A piston crown, cylinder head and valves were coated with
ceramic material over super alloy bond coating (NiCrAlY). The bond coat was first
applied to these engine components to avoid mismatch in thermal expansion between
substrate and ceramic material. A piston crown, cylinder head and valves were coated
with 0.5 mm coating of Mullite is commonly denoted as 3Al2O3 .2SiO2 (i.e. 60
mol% Al2O3). The ceramic material was coated by using plasma-spray technique.
The engine was insulated and tested at baseline conditions to see the effect of
insulated surfaces on engine performance and combustion characteristics.
In Third stage, after conducting experiments on LHR (mullite coated) diesel
engine with supercharger, the experiments were conducted on LHR (mullite coated)
diesel engine with turbocharger. The turbocharger was used to utilize the energy of
exhaust gases (which was increased due to mullite coating) of LHR (mullite coated)
diesel engine and to evaluate its effect on the performance of diesel engine. In order to
utilize the exhaust energy (increased due to mullite insulation) of LHR engine, a pulse
turbocharger was installed. For LHR engine with turbocharger, the fuel consumption
was increased by advancing injection timing to 320
bTDC. The experiments were
carried out on a single cylinder, four stroke, direct injection, low heat rejection (LHR)
diesel engine with and without turbocharger to investigate overall engine
performance.

Figure 1 Photographic view of Mullite coated Engine components.
Figure 3 Photographic view of Pulse Turbocharger
3. RESULTS AND DISCUSSIONS
After conducting long-term experimental investigations on a single cylinder, four
stroke, direct injection, conventional (without coating) and LHR (Low Heat rejection
mullite coated) diesel engines, the engine performance and combustion characteristics
such as brake power, brake thermal efficiency, brake specific fuel consumption,
exhaust gas temperature, NOx, HC, CO for both the Conventional and LHR engines
are evaluated. The engine performance and combustion characteristics are evaluated
for 0%, 25, 50, 75% of full engine load and full engine load condition for both
conventional and LHR diesel engines.

3.1 Comparison of experimental results such as combustion parameters and overall
engine performance characteristics of the conventional (without coating) and LHR
(mullite coated) diesel engines under identical conditions
Fig.4 Engine Load vs. Heat Lost To Coolant
Fig. 4 Shows the comparison of heat lost to the coolant as a function of engine
load for conventional and LHR (mullite coated) diesel engines. It is found that,
mullite coated combustion chamber reduces heat transfer to the coolant. LHR engine
resulted 8.1, 11.3,14.2 and 16% reduction in heat transfer to the coolant for 25, 50,
75% of full engine load and full engine load condition respectively compared to
conventional (without coating) diesel engine. This is due to fact that mullite material
has lower thermal conductivity than metals so that the Heat flow to the coolant will be
reduced which results in higher combustion temperature.
Figure 5 Engine Load vs Brake Power
Fig. 5 Shows the comparison of brake power as a function of engine load for
conventional and LHR (mullite coated) diesel engines. It is found that, the values of
brake power are slightly higher for LHR (mullite coated) engine as compared to
conventional engine. This is due to fact that effect of insulation; the heat free flow is
restricted, which results in reduction in heat transfer in case of LHR engine. The
2
2.5
3
3.5
4
4.5
No Load 1/4 Load 1/2 Load 3/4 Load Full Load
HeattoCoolant(Kw)
Load (Kg)
Load Vs Heat Lost to Coolant
Conventional
Engine
LHR Engine
0
0.5
1
1.5
2
2.5
3
3.5
4
BrakePower(Kw)
Load (Kg)
Load Vs Brake Power
Conventional
Engine

reduction in heat transfer leads to increase in combustion temperature, which results
in better combustion. The higher combustion temperature will lead to more expansion
work. The increase of combustion temperature causes the brake power to increase up
to 8.68 % with LHR engine at full engine load condition compared to conventional
engine.
Figure 6 Engine Load vs Brake Specific Fuel Consumption
A comparison of BSFC for conventional and LHR engine at various loads is as
shown in fig.6 Because of higher surface temperature of combustion chamber of LHR
engine as compared to conventional engine, the BSFC values of LHR engine is less
than those of conventional engine. The improvement in fuel economy observed in
LHR engine may be due to: higher premixed combustion, reduced heat transfer loss,
lower diffused combustion and higher rate of heat release in the main portion of
combustion chamber. It is found that BSFC value is decreased by 7.52 % for LHR
(mullite coated) engine as compared to conventional engine at full engine load.
Figure 7 Engine Load vs. Brake Thermal Efficiency
It is observed from fig. 7 that, the amount of increase in thermal efficiency for
LHR engine is 2.06 % compared to conventional engine at full engine load while at
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
BSFC(Kg/Kwhr)
Load (Kg)
Load Vs BSFC
Conventional Engine
LHR Engine
0
5
10
15
20
25
30
35
B.TH.EFF.(Ŋ%)
Load (Kg)
Load Vs B.TH. EFF
Conventional Engine
LHR Engine

low and medium loads thermal efficiency shows less variation for LHR engine when
compared to the conventional engine. This is because that heat recovered by
insulation which is generally lost to the cooling, is converted into useful work
(indicated work). But all the heat recovered by the insulation may or may not be able
to get converted into some useful work. Therefore, the rate of increasing thermal
efficiency for LHR engine is minor compared to conventional engine.
3.2 Comparisons of experimental results such as engine exhaust emissions of the
conventional (without coating) and LHR (mullite coated) diesel engines under
identical conditions
After conducting long-term experimental investigations on a single cylinder, four
stroke, direct injection, conventional (without coating) and LHR (mullite coated)
diesel engines, the engine exhaust emissions such as carbon monoxide (CO),
Nitrogen-oxides (NOx), Unburned hydrocarbons (UHC), and exhaust gas temperature
all as a function of load for both the Conventional and LHR engines are calculated.
The engine exhaust emissions are found for 25%, 50%, 75% of full engine load and
full engine load condition for both conventional and LHR diesel engines.
Fig.8 shows the comparison of NOx variations as a function of engine load for
conventional and LHR engine. It is found that the NOx emission for LHR engine is
more as compared to conventional engine. The NOx emission for LHR engine at full
engine load is 20.19 % higher than conventional engine. The increase of NOx
emission for in the LHR engine may be due increase in after-combustion temperature
due to the mullite coating. This is due to higher combustion temperature and having
longer combustion duration.
Figure 8 Engine Load vs. Nitrogen Oxide (NOx)
Fig.9 shows the comparison of HC emission variations as a function of engine
load for conventional and LHR engines. Hydrocarbon emission is 24.36 % lower in
the Low Heat rejection engine compared to conventional engine. The decrease in
Hydrocarbon emission in the Low Heat rejection (LHR) engine may be due to an
increase in after-combustion temperature as a result of the decrease in heat losses
going to cooling and also outside due to the ceramic coating, creating more unburned
Hydrocarbon (HC) to be added to the combustion. The result clearly shows that the
ceramic coating improves local conditions such as cylinder gas pressure, cylinder gas
temperature, and makes the combustion continuous in diesel engines. The higher
0
1
2
3
4
5
6
7
8
NitrogenOxide(g/Kwhr)
Load (Kg)
Engine Load vs Nitrogen Oxide
Conventional Engine
LHR Engine

temperatures in the gases and at the combustion chamber walls of the LHR engine
allows the oxidation reactions to close to completion results in decreasing the
Hydrocarbon (HC) emissions.
Figure 9 Engine Load vs. Unburnt Hydrocarbon
Figure 10 Engine Load vs Carbon Monoxide
Fig.10 shows the comparison of CO emissions variations as a function of engine
load for conventional and LHR engines. Carbon monoxide (CO) emission is 29.41 %
lower in the LHR engine compared with the conventional engine. This is due to the
fact that, because of ceramic coating which bears the thermal barrier property, which
results in increase in combustion temperature for LHR engine. The decrease in the
amount of heat rejected to the cooling water system which results in an increase in
combustion temperature. Increase in combustion temperature increases the time for
CO oxidation, which results in decreasing CO emission for LHR engine.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
UnburntHydrocarbon(g/Kwhr)
Load (Kg)
Engine Load vs Unburnt Hydrocarbon
Conventional Engine
LHR Engine
0
1
2
3
4
5
6
7
CarbonMonoxide(g/Kwhr)
Load (Kg)
Engine Load vs Carbon Monoxide
Conventional Engine
LHR Engine

Figure 11 Engine Load vs Exhaust Gas Temperature
Fig. 11 shows variations of exhaust gas temperature against the load of the
conventional and LHR engines. As observed in Fig. Exhaust gas temperature
increases as the load on engine increases for both the engines. This is due fact that the
amount of fuel consumption per unit time increases as the engine load increases, and
Hence, more heat is produced. As a result it leads to increase in exhaust gas
temperature. The increase in exhaust gas temperature in the LHR engine, compared
with the conventional engine is 18.03% higher at full engine load. The increase in
exhaust gas temperature for the LHR engine as compared to the conventional engine
may be due to the decreased heat losses going into the cooling water system and
outside the cylinder due to the coating and hence the transfer of this heat to the
exhaust gas.
3.3 Comparison of experimental results such as overall engine Performance
Characteristics of the LHR engine (mullite coated) with and without turbocharger
Figure 12 Engine Load vs. Brake Specific Fuel Consumption
Fig.12 shows variations of brake specific consumption with load of the LHR
engine with and without turbocharger. It is observed that, brake specific consumption
for LHR engine with Turbocharger increases for low and medium engine loads as
0
50
100
150
200
250
300
350
400
450
500
ExhaustgasTemperature(()C)
Load (Kg)
Engine Load vs Exhaust gas Temperature
Conventional Engine
LHR Engine
0.2
0.3
0.4
0.5
0.6
0.7
BSFC(Kg/Kwhr)
Load (Kg)
Engine Load vs BSFC
LHR Engine without
Turbocharger
LHR Engine With
Turbocharger

compared with the LHR engine without turbocharger. The increase in brake specific
consumption at low engine load is 2.89 % while the increase in brake specific
consumption at full engine load is 2.10 % for LHR engine with turbocharger
compared with the LHR engine without turbocharger. This is due to fact that the
increase of back pressure on the engine due to turbocharger. As the back pressure
goes on increasing, the engine must work harder to pump the gases out of the cylinder
against the higher pressure. The pressure ratios across the turbocharger compressor
and turbine decrease, reducing the mass flow of air through these components and
thus the air available to the engine. At the same time, the fuel flow to the engine
increases so as to provide the extra power required to overcome the increased
pumping losses while maintaining a brake power output constant. As a result the
brake thermal efficiency decreases and brake specific fuel consumption increases
above that for a LHR engine without Turbocharger. Also it is observed that at low and
medium loads the brake thermal efficiency decreases due to the effect of "turbo lag".
At low and medium engine loads of the engine, the "turbo lag" occurs in exhaust gas
turbocharger because the mechanical power transmitted from the turbine wheel to the
compressor rotor of the exhaust gas turbocharger is at all no longer sufficient for the
engine to increase the pressure in the intake tract of the engine due to the low exhaust
gas volume flow.
Figure 13 Engine Load vs. Heat Lost to Exhaust Gas.
Fig.13 shows variations of exhaust gas energy with load of the Low Heat
Rejection engine with and without turbocharger. The increase in exhaust gas energy is
more at low and medium load levels for LHR engine with Turbocharger as compared
with LHR engine without Turbocharger. The increase in exhaust gas energy is 17.33
% at low engine load while at full engine load the increase in exhaust gas energy is
4.03 % for LHR engine with turbocharger compared with the LHR engine without
turbocharger. This is due to the increase in exhaust gas temperature at low and
medium load levels for LHR engine with Turbocharger. The exhaust gas temperature
at low and medium load levels increases significantly with increasing back pressure
due to the increased power required (to overcome the additional pumping work) and
the reduced air flow.
0
0.5
1
1.5
2
2.5
3
3.5
4
Heatlosttoexhaustgases(Kw)
Load (Kg)
Engine Load vs Heat Lost to Exhaust gases
LHR Engine without
Turbocharger
LHR Engine With
Turbocharger

4. CONCLUSION
The main conclusions of these experimental investigations are summarized as
follows.
 In case of LHR engine with 0.5 mm of mullite (3Al2O3.2SiO2) insulation coating on
piston crown, cylinder head and valves of diesel engine, observed reduction in heat
transfer to the coolant at all engine load levels compared to conventional diesel
engine.
 The amount of heat energy carried with exhaust gases are considerably increased at
all load levels in case of LHR engine with 0.5 mm of mullite (3Al2O3.2SiO2)
insulation coating compared with conventional diesel engine.
 LHR engine with 0.5 mm of mullite (3Al2O3.2SiO2) insulation coating on
piston crown, cylinder head and valves of diesel engine exhibits lower brake
specific consumption than the conventional diesel engine.
 LHR engine with 0.5 mm of mullite (3Al2O3.2SiO2) insulation coating on
piston crown, cylinder head and valves of diesel engine gives marginal rise in
brake thermal efficiency when compared with conventional diesel engine.
 The NOx emission for LHR engines with 0.5 mm coating of mullite thermal
insulation on combustion chamber is more than conventional engine. It is
observed that the NOx emission for LHR engine at full engine load is higher
than conventional engine.
 The HC emission is lower than in the LHR engine compared with the
conventional engine. It is observed that the HC emission for LHR engine at
full engine load is 24.35 % lower than conventional engine.
 The CO emission is lower than in the LHR engine compared with the
conventional engine. It is observed that the CO emission for LHR engine at
full engine load is 29.41 % lower than conventional engine.
 Exhaust gas temperature increases as the engine load increases for both conventional
and LHR engines. The increase in exhaust gas temperature in the LHR engine,
compared with the conventional engine is 22 % at full load condition
 LHR engine with turbocharger exhibits degradation of performance when
compared with LHR engine without turbocharger. LHR engine with
turbocharger exhibits lower brake thermally efficiency while increases brake
specific consumption at all engine load levels than the LHR engine without
turbocharger.
5. REFERENCES
[1] Brunauer G., Frey F., Boysen H. and Schneider H., “High temperature thermal
Expansion of mullite: an in-situ neutron diffraction study up to 1600 o
C”, J. Eur.
Ceram. Soc., Vol. 21, pp 2563–2567, 2001.
[2] Vassen R., Cao X.Q., Tietz F., Basu D., and Stover D. “Zirconates as new
Materials for thermal barrier coatings”, Journal of the American Ceramic Society,
Vol. 83, pp 2023-2028, 2000.
[3] Meier S.M., Gupta D.K., “The evolution of thermal barrier coatings in gas turbine
Applications”, Journal of Engineering for Gas Turbines and Power, Vol.116, pp
250–257, 1994.
[4] Gilbert A., Kokini K., Sankarasubramanian S., Surf. Coating Technol., Vol.202
pp 2152, 2008.

[5] Kamo R., and Bryzik W., “Adiabatic turbocompound engine performance
Prediction”, SAE Paper No. 780068, 1978.
[6] Kamo R., and Bryzik W., “Ceramics in heat engines”, SAE Paper No. 790645,
1979.
[7] Hejwowski T. and Weronski A., “The effect of thermal barrier coatings on diesel
engine performance”, Surf. Engng, Surface Instrum. and Vacuum
Technol.,Vol.65, pp 427–432, 2002.
[8] Thring R.H., “Low Heat Rejection Engines”, SAE Paper No.860314.
[9] Dr. V. Naga Prasad Naidu and Prof. V. Pandu Rangadu. Performance Evaluation
of A Low Heat Rejection Diesel Engine with Cotton Seed Biodiesel,
International Journal of Mechanical Engineering and Technology, 5(2), 2014,
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[10] T. Ratna Reddy and M.V.S. Murali Krishna. Studies on Performance Parameters
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Experimental investigation of mullite coated diesel engine

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