1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME
20
EXPERIMENTAL INVESTIGATIONS ON THE PERFORMANCE AND
EMISSOIN CHARACTERISTICS OF A MULLITE COATED DI
DIESEL ENGINE
1
Vinay Kumar Domakonda*
, 2
Ravi Kumar Puli, 3
Santhosh Kumari
1,2
Department of Mechanical Engineering, National Institute of Technology, Warangal,India
3
Christu Jyothi Institute of Technology and Scienc, Jangoen, Warangal, India
ABSTRACT
Mullite (3Al2O3-2SiO2) ceramic powder has been used as a thermal barrier coating material to
study its effect on the performance and exhaust emissions of a single cylinder diesel engine operated
using diesel fuel. Mullite thermal barrier coatings have been proved to be an efficient thermal barrier
coating material besides the conventional YSZ TBCs with lower thermal conductivity, high sintering
resistance, low oxygen permeability. The study has shown that the performance of the engine is
improved significantly on the account of brake thermal efficiency and specific fuel consumption.
Emissions, on the other hand are also found to be reduced considerably, especially the smoke opacity
which is significantly low at all Low Heat Rejection (LHR) operations.
Key Words: Low Heat Rejection Diesel Engine, Mullite, Thermal Barrier Coatings.
1. INTRODUCTION
Plasma-sprayed ceramic thermal barrier coatings (TBCs) are being extensively perused area
of interest from the recent past for the improved efficiency and reduced emissions especially in diesel
engines. Yttria stabilized zirconia, also called partially stabilized zirconia(Y-PSZ) material is believed
to be a reliable TBC until now but the failure of the coating at elevated temperatures under continuous
thermal shocks as in diesel engines lead to the investigation of new materials for TBC applications.
PSZ is limited due to phase transitions and increased sintering of the porous TBC layer above 1200
°C, which leads to catastrophic delamination of the coating. The failure of the PSZ coatings is also
attributed to the high concentration of oxygen vacancies which permeates the oxygen through it,
leading to the oxidation of the bond coat and sintering of the coating at higher temperatures, which
leads to a decrease in porosity and an increase of Young’s modulus and, hence, to higher thermally
induced stresses [ HYPERLINK l "Yul10" 1 ].
In order to overcome the disadvantages of PSZ and to meet the requirements of an ideal TBC,
it is needed to develop a new candidate material with even lower thermal conductivity, capability to
withstand higher operating temperatures, higher sintering-resistance and phase stability at even higher
temperature2]}. Among the interesting candidates for TBCs, rare earth zirconates have been
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2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME
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investigated, and they have been proved to be significant for the top coating materials [19]. Among
these materials,, Mullite shows promising thermo-physical properties and has attracted great attention
as candidate material for thermal barrier applications [ HYPERLINK l "Hen03" 3 ]. To this purpose,
mullite (3Al2O3–2SiO2) coatings are particularly promising due to their high thermal stability, low
thermal conductivity, high resistance in highly oxidative and corrosive environments, high resistance
to crack propagation and high thermal shock resistance [1–6]. Previous works have demonstrated that
mullite coated diesel engine components exhibited decreased surface cracking when compared to
zirconia coated ones [7]. In addition, mullite coatings are suitable for environmental protection of
ceramic matrix composites (CMC),i.e. SiC-based ceramics, against corrosion from molten salts and
water vapour in combustion environments, due to their good density, chemical compatibility and
thermal expansion coeffi-cient very close to that of the substrate [8,9].
2. EXPERIMENTAL SETUP AND PROCEDURE
The experimental setup consists of a Kirloskar made single cylinder direct injection diesel
engine whose specifications are given below in Table.2 is a widely used engine for agricultural
activities and water pumping in India. The set up also consists of a Kistler made pressure transduser
type 7001, flush mounted on the cylinder head for the measurement of in-cylinder pressure,an optical
TDC marker, a charge amplifier of type 5007 made by Kistler and an NI USB 6008 DAQ card for the
conversion of pressure sensor and TDC marker analog signals into digital signal and for data
acquisition. A labview based software has been used to monitor pressure and TDC signal data.
Exhaust gas emissions are measured using a NETEL Made five gas analyzer model NPM-MGA-2 and
smoke opacity is measured using NETEL smoke meter model no.NPM-SM-111B (Table.3). Fuel
consumption is measured using a calibrated burette and volume flow rate of air is measured using an
air box and U-tube manometer. The engine components viz. piston, cylinder head and valves are
coated with Lanthanum zirconate and have been shown in Fig.2.
Figure.1 Schematic diagram of the experimental setup
Figure.2 Mullite coated engine components

3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME
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No. of cylinders One
Bore, mm 80
Stroke, mm 110
Cubic capacity, CC 553
Rated output, kW (HP) 3.68 (5)
Compression Ratio 16.5:1
Type of Injection Direct
STD Inj. Timing, o
BTDC 23
STD.Inj.opening pr.,kg/cm2
200
Type of cooling water
Rated speed, RPM 1500
Table.2. Specifications of the test engine.
Thermocouples are arranged at different locations to measure the temperatures at different engine
parts viz. engine coolant outlet temperature, exhaust gas temperatures etc. .
Experiments were conducted initially on the standard engine i.e. without applying coating to
the engine parts at standard, manufacturer specified injection timing of 230
BTDC and at an injector
opening pressure of 200 kg/cm2
using diesel fuel. Then the mullite coated parts are assembled to the
engine thus making it low heat rejection engine(LHRE). Experiments are repeated same as above at
standard engine operating conditions .
NPM-MGA-2 Five Gas Analyzer
Gases measured Method Measurement
Range
Resolution Accuracy
HC NDIR 0-20,000 ppm 1 ppm +/- 10ppm abs
CO NDIR 0-9.99 % 0.01 % +/- 0.03% abs
CO2 NDIR 0-20.00 % 0.10 % +/- 0.04% abs
O2 Electrochemical 0-25 % 0.01 % +/- 0.1% abs
NOx Electrochemical 0-10,000 1 ppm +/- 25ppm abs
NPM-SM-111B Smoke meter
Type of smoke meter Partial flow
Display indication Light absorption coefficient (K) and percentage opacity
Display Range 0-9.99 m-1
Linearity 0.1 m-1
Repeatability 0.1 m-1

4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME
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Table.3. Technical Specifications of five gas analyzer and smoke meter
Table.4. Plasma spraying parameters (Severin Seifert et al)
RESULTS AND DISCUSSIONS
Generally, the concentrations of pollutants in internal combustion engine exhaust differ from
values calculated assuming chemical equilibrium. Thus the detailed chemical mechanisms by which
these pollutants form and the kinetics of these processes are important for determining emission
levels. For some pollutant species, e.g., carbon monoxide, organic compounds, and particulates, the
formation and destruction reactions are intimately coupled with the primary fuel combustion process.
In the diesel engine, the fuel is injected into the cylinder just before combustion starts, so throughout
most of the critical parts of the cycle the fuel independent of the fuel distribution and how that
distribution changes with time due to mixing.
Fig.3 Variation of BSFC with brake power with and without coating
Fig.4 Variation of brake thermal efficiency with brake power with and without coating using different
fuels

5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN
0976 – 6480(Print), ISSN 0976 – 6499(Online) Volume 4, Issue 3, April (2013), © IAEME
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Fig.4 shows the variation of brake thermal efficiency with brake power for the standard and
mullite coated LHR engine at standard operation conditions. Mullite LHR engine when run with
standard diesel has shown 5.78% improvement in the brake thermal efficiency compared to the
standard diesel operation. Reduced heat transfer to the cooling system in the case of LHR engine is
believed to have helped in increasing the brake thermal efficiency of the engine.
CONCLUSIONS
1. Mullite has been used as candidate material for TBC and a series of experiments have been
conducted on a single cylinder direct injection diesel engine.
2. Experimental observations showed that the mullite has ensured in improved engine performance
with reduced emissions at all engine load conditions.
3. The BSFC has been found to be 5.46% low with LHRE compared to that of standard engine
operation at full load condition
4. Brake thermal efficiency of the LHR engine is improved significantly compared to that of standard
engine operation resulting in over 5.78% improvement.
5. CO emissions are reduced with LHR operation significantly. Higher CO emissions from standard
engine using diesel fuel are attributed to the non-favorable conditions for the oxidation of CO into
CO2 especially at no load and full load conditions. This problems has been overcome using TBCs
because of which rise in in-cylinder temperatures helped to oxidize the CO emissions formed
within the cylinder.
6. Rise in in-cylinder temperatures because of the insulation has resulted in increased gas
temperatures and thus NOx emissions. The insulation has resulted in around 4%,higher at full load.
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