Reduction of NOx emission on NiCrAl-Titanium Oxide coated directinjection diesel engine fuelled with radish (Raphanus sativus) biodieselV. Ravikumar and D. Senthilkumar Citation: J. Renewable Sustainable Energy 5, 063121 (2013); doi: 10.1063/1.4843915 View online: http://dx.doi.org/10.1063/1.4843915 View Table of Contents: http://jrse.aip.org/resource/1/JRSEBH/v5/i6 Published by the AIP Publishing LLC. Additional information on J. Renewable Sustainable EnergyJournal Homepage: http://jrse.aip.org/ Journal Information: http://jrse.aip.org/about/about_the_journal Top downloads: http://jrse.aip.org/features/most_downloaded Information for Authors: http://jrse.aip.org/authors

Reduction of NOx emission on NiCrAl-Titanium Oxidecoated direct injection diesel engine fuelled with radish(Raphanus sativus) biodiesel

V. Ravikumar1,a) and D. Senthilkumar21Department of Mechanical Engineering, Dhirajlal Gandhi College of Technology,Salem 636309, Tamil Nadu, India2Department of Mechanical Engineering, Sona College of Technology, Salem 636005,Tamil Nadu, India

(Received 18 March 2013; accepted 28 October 2013; published online 9 December 2013)

The main aim of this study is the experimental investigation of single cylinder DI

diesel engine with and without coating. Diesel and radish (Raphanus sativus) oil

Methyl Ester are used as fuels and the results are compared to find the effect of

biodiesel in a thermal barrier coating engine. For this purpose, engine cylinder

head, valves, and piston crown are coated with 100 lm of nickel-chrome-

aluminium bond coat and 450 lm of TiO2 by the plasma spray method. Radish oil

methyl ester is produced by the transesterification process method. From the

experimental investigation, slight increase in specific fuel consumption in thermal

barrier coating engine is observed when compared with the uncoated engine,

whereas NOx, HC, Smoke, and CO emissions decreased with coated engine for all

test fuels used in the coated engine when compared with that of the uncoated

engine. VC 2013 AIP Publishing LLC. [http://dx.doi.org/10.1063/1.4843915]

I. INTRODUCTION

Researchers of internal combustion engine group have always focused towards engine

emission control and its performance in economical and renewable aspects. Diesel engine which

is being used in various sectors like transportation, railways, and agriculture has high thermal

efficiency, durability, and reliability of usage and are major contributors for the economic

growth of the country. In the forthcoming years, the eco-friendly, renewable, and vegetable

based fuels will serve as a supplement to conventional petroleum fuel which is depleting at a

faster rate. Basha et al.1 have reviewed that vegetable oil would serve as a suitable alternative

fuel for compression ignition engine in its pure form or blended with petroleum diesel.

Moreover, biodiesel is comparatively better than diesel based on some of its physical properties

like sulfur content, flash point, aerometric content, and biodegradability. Ramadhas et al.2

reviewed the various production methods of biodiesel from the pure vegetable oil and stated

that methyl esters of vegetable oil have good performance and low emissions characteristics

when compared with petroleum diesel. Transesterification is the process which reduces the vis-

cosity of the vegetable oils and animal fats. This process consists of three steps in which tri-

glycerides are converted into diglycrides and monoglycrides which is finally converted into

glycerol in the presence of alkali catalyst. Patil and Deng3 optimized the corn oil biodiesel pro-

duction via. a single step transesterification process using 2% alkali catalyst with methanol to

oil ratio of 9:1 at a temperature of 80 �C which gave around 96% of biodiesel. Yusuf et al.4

have reviewed production of biodiesel, and possibility of its utilization. Malhotra and Raje5 of

Indian Oil Corporation have done experimental works to study suitability of biodiesel for trans-

portation and agriculture purposes. Murugesan et al.6 have conducted tests on a single cylinder

diesel engine fuelled with methyl-ethyl esters of Pongamia and neem oils blended with diesel,

a)Electronic mail: deevravi@gmail.com

1941-7012/2013/5(6)/063121/11/$30.00 VC 2013 AIP Publishing LLC5, 063121-1

JOURNAL OF RENEWABLE AND SUSTAINABLE ENERGY 5, 063121 (2013)

up to B40 the blends gives similar brake thermal efficiency. Saravanan et al.7 have done experi-

mental investigation on DI diesel engine fuelled with Maduca Indica methyl ester has given the

performance and emissions as almost similar to that of engine fuelled with petroleum diesel.

Devan and Mahalakshmi8 made experimental investigation on DI diesel engine fuelled with poon

oil methyl ester and found that 2.13% increase in brake thermal efficiency and considerable

amount of reduction in emissions like HC and smoke. Many authors have studied the perform-

ance and emission characteristics of processed vegetable oils, however few studies on raw vegeta-

ble oils were also carried out. The performance and emission experiment was carried out using

neat orange oil by Purushothaman and Nagarajan9 and found to have considerable hike in heat

release rate, thermal efficiency and NOx than that of fossil diesel. The comparison of performance

and emission characteristics of sunflower oil methyl ester-diesel with cotton seed oil methyl

ester-diesel blends were carried out by Rakopoulos et al.10 and observed better performance and

emissions from cotton seed oil methyl ester-diesel blend. Better thermal efficiency, slightly lower

Specific Fuel Consumption (SFC) were achieved by Jindal et al.11 at 18� before Top Dead Centre

(bTDC) of ignition timing and 250 bar of injection pressure using jatropha biodiesel as fuel.

Jaichandar and Tamilporai12 have reviewed that on a diesel engine, one third of the heat energy

is converted into useful work and one third is wasted through exhaust gas and the remaining is

wasted through heat which is carried out to the coolant. As per second law of thermodynamics,

thermal efficiency could be increased by reducing heat rejection to the coolant. In this effort, to

achieve low heat rejection of the engine, the combustion chamber walls are insulated by ceramic

coatings. Wong13 has reported that coating thickness for better thermal efficiency will be in the

range of 250 lm–500 lm. Assanis et al.14 have conducted tests on a supercharged DI diesel engine

with Partially Stabilized Zirconia (PSZ) coating thickness of 500 lm–1000 lm by use of plasma

spraying machine and compared the results with standard engine and in their study insulating the

piston crown with a thin (500 lm) coating engine gave better engine performance and reduced

emissions. Kamo et al.15 reported that thin thermal barrier coatings of engine combustion chamber

would increase the volumetric efficiency of the engine. Biodiesel can be used as a more efficient

fuel in the thermal barrier coating engines, because of the high temperature of the thermal barrier

coated combustion chamber. Buyukkaya et al.16 have studied the performance and emissions char-

acteristics of multi cylinder turbocharged diesel engine, coated at different location with MgZrO3,

CaZrO3. Corn oil methyl ester was utilized by Hazar and Ozturk17 as a fuel in an Al2O3-TiO2

coated engine. The performance was compared to that of uncoated diesel engine and found to

decrease in CO and SFC along with an increase of 11.3% in exhaust gas temperature for all biodie-

sel blends in coated engine. Hasimoglu et al.18 found the performance parameter enhancement of

turbocharged diesel engine coated with yttria stabilized zirconia (Y2O3ZrO2) and NiCrAl using

sunflower oil methyl ester. Sundarraj et al.20 carried out an analysis of 1,4-dioxine-ethanol-diesel

blends on diesel engines with and without thermal barrier coating. They concluded that 70% diesel,

20% ethanol, and 10% dioxane blend would give better performance and lower emissions.

From the above literature review, it is clear that many researchers have been focusing on

transesterification processes on different types of vegetable oils (Jatropha, Cottonseed,

Sunflower, Pongamia, Corn, Madhuca Indica, etc.) for production of biodiesel and tested using

standard and coated diesel engine. However, few researchers used vegetable oils as a sole fuel

for diesel engine. None used Radish biodiesel as a fuel for TiO2 as a coating material for diesel

engine. The main focus of the present work is to produce biodiesel from Radish seed oil by

transesterification process as fuel. Also to evaluate the performance and emission characteristics

of Radish biodiesel blends with diesel (B25) in a standard and TiO2 coated single cylinder die-

sel engine and to compare with neat diesel fuel.

II. MATERIALS AND METHODS

A. Potential and characterization of radish oil

Radish plant is botanically known as Raphanus sativus. The word radish is derived from

the Latin word “Radix” which means “root.” Radish plants belonging to the family of Mustard

crops. Generally, the root is the common edible part of the plant. The leaves, flowers, and

063121-2 V. Ravikumar and D. Senthilkumar J. Renewable Sustainable Energy 5, 063121 (2013)

young pods of the plant are also eaten. The Radish plant is being grown all over the world. This

is one of the oldest vegetable, and its nativity is believed to be China. Radish finds wide applica-

tion. In the composition of medicines used for cough and cold, Radish juice is a main ingredient.

The harvesting time for Radish seed is approximately 120 to 150 days. The roots are available in

variety of colours and Shapes are about 30 to 45 cm long. Life cycle of radish include different

stages. The time of full formation of root is referred as harvesting period. If the growth is past

their normal harvesting period, flowering follows and then “pods” grow in which seeds are

formed. Seeds yield of about 6 to 8 quintals per hectare is obtained from Radish crop. The oil

content in the Radish seed is around 50%. The oil is used as an illuminant and lubricant.

B. Production of radish biodiesel

Figure 1 shows the photographic view of Radish seed. From this seed, oil is extracted by

means of mechanical extraction and biodiesel is produced. It can be produced by transesterifica-

tion process. It is a method which is used to produce biodiesel from radish oil using methanol

as reagent and potassium hydroxide (KOH) as catalyst. 20% of methanol mixed with 1.48% of

KOH by volume is prepared as base solvent. This is mixed thoroughly and added to 1000 ml of

raw Radish oil at 65 �C with stirring rate of 300 rpm for 10 to 15 min for separating the resi-

dues of the biodiesel. Final solution can be separated from the glycerol by separating funnel.

This final solution may have some soap content. This may be removed by using bubble wash-

ing by adding 50% of water with final solution which is derived from base reaction process.

This solution may be heated up to 100 �C for removing water content from the final solution.

The biodiesel (mixture of alkyl ester) is the end product of the process. After washing the bio-

diesel the excess methanol, if any, is evaporated by heating it to about 70 �C (boiling point of

the methanol) for few minutes. This process is called as De-methanolisation.

C. Thermo-physical properties of radish biodiesel and its diesel blends

Using standard test facilities, the thermo-physical properties of Radish Oil Methyl Ester

(ROME) and its blend with pure diesel have been evaluated. Table I reports the values of pure

diesel (B0) and a blend of 25% radish seed biodiesel with pure diesel by volume (B25). From

Table I, it is clear that specific gravity, acidity, kinematic viscosity, flash point, fire point, and

cloud point increase as the methyl ester content in the biodiesel-diesel blends increases.

Especially, the significant increase in the fire point shows that the volatility of the mixture hav-

ing increased biodiesel content will decrease. It is also observed that the flash point and fire

FIG. 1. Photographic view of Radish seeds.

063121-3 V. Ravikumar and D. Senthilkumar J. Renewable Sustainable Energy 5, 063121 (2013)

point of biodiesel blend in various volumetric proportions increase. Therefore the blends of fuel

are very easy to store and safe for transportation as compared with B0 (pure diesel). The gross

calorific value decreases as the biodiesel in the mixture increases. This is due to the oxygen

content in the fuel and it requires more fuel to be burnt for a given heat release.

D. Atmospheric plasma spraying machine (APS)

The coating can be done in three phases. In the first phase, the engine component like pis-

ton crown, valves, and cylinder head are grit-blasted for creating the roughness for the bonding

purpose. The grit-blasted surfaces are ultrasonically cleaned using anhydrous ethylene alcohol

and dried in cold air prior to coating deposition. In the second phase, the NiCrAl bond coatings

of about 100 lm in thickness are air plasma sprayed on to the components for effective bond-

ing. The bond coat particle size ranges from 35 to 65 lm. In the third phase, ceramic compos-

ite, TiO2 of 450 lm thickness is coated to engine components by Atmosphere Plasma Spray

coating technique which is shown in Figure 2 and the photographic view of coated piston

TABLE I. Properties of diesel (B0) and B25.

S. No. Name of the properties ASTM code B0 (diesel) B25

1 Kinematic viscosity at 40 �C in cSt D2217 2.6 3.42

2 Gross calorific value in kJ/kg D4809 45596 44013

3 Flash point in �C … 65 76

4 Fire point in �C … 70 81

5 Cloud point in �C … �15 3

6 Specific gravity in dl D445 0.82 0.841

7 Acidity in dl … 0.065 0.041

8 Cetane number in dl … 46 51.8

9 Pour point in �C … �5 2

FIG. 2. Atmospheric plasma spraying machine.

063121-4 V. Ravikumar and D. Senthilkumar J. Renewable Sustainable Energy 5, 063121 (2013)

crown, valves and cylinder head is shown in Figure 3. The limits of plasma spray machine pa-

rameters are given in Table II.

E. Experimental procedure

Experiments have been conducted on a 4 stroke, Kirloskar, TV 1 direct injection diesel

engine developing a power output of 5.2 kW at a constant speed of 1500 rpm connected

with water cooled eddy current dynamometer. The schematic of the engine setup is shown in

Figure 4 and specifications of the engine are presented in Table III. Standard static injection

timing of 23� bTDC and nozzle opening pressure of 220 bar are used for the entire experiments

at different brake power of the engine. AVL 444 digital di-gas analyzer is used for the mea-

surement of exhaust emissions of HC, CO, and NOx. Smoke level is measured using standard

AVL 437 smoke meter. All the experimental readings were taken at different brake power for

TiO2 coated and standard engine fuelled with pure diesel and B25 (25% of Radish oil methyl

ester þ 75% of pure diesel) at steady state condition of the engine.

III. RESULTS AND DISCUSSION

A. Specific fuel consumption

Figure 5 shows the variation of specific fuel consumption with brake power in diesel and

B25 for TiO2 coated and uncoated diesel engine at rated engine speed. From the graph it is

clear that SFC increases with the increase in brake power and biodiesel. Compared to standard

engine, coated engine shows slight increase in SFC and this is because of TiO2 coated combus-

tion chamber. The coating material absorbs some amount of heat; therefore to get the same

FIG. 3. Photographic view of 450 lm TiO2 coated piston, valves, and cylinder head.

TABLE II. Limits of plasma spray process parameters.

Operating parameter Range

Power (kW) 40

Current (A) 350–700

Voltage (V) 30–40

Primary plasma gas (argon) flow rate (l/min) 20

Secondary gas (nitrogen) flow rate (l/min) 2

Torch to base distance (mm) 130

Powder feed rate (g/min) 65

Powder carrier gas (argon) flow rate (l/min) 6

063121-5 V. Ravikumar and D. Senthilkumar J. Renewable Sustainable Energy 5, 063121 (2013)

power output, more amount of fuel will be burnt inside the combustion chamber. Percentage

increase in SFC for coated diesel at different brake power is in the range of 5.8% to 12.2%

compared to standard diesel engine operation and the comparison to coated B25 test fuel condi-

tion shows 8.6% to 14.35% increase in SFC which is due to lower calorific value and higher

viscosity of biodiesel.8

B. Brake thermal efficiency

Thermal efficiency is the true indication of efficiency. It is the ratio of brake power to the heat

supplied which converts chemical energy into useful mechanical work. Diesel and B25 as test fuel

at varying brake power for both coated and standard engine at rated speed is shown in Figure 6.

From the test results, it was observed that there was significant increase in brake thermal efficiency

with increase in brake power. When compared to Standard Engine (SE), Coated Engine (CE)

FIG. 4. Schematic of the engine setup.

TABLE III. Specification details of the diesel engine.

Name of the description Details/value

Make Kirloskar TV–I

Type Vertical single cylinder, DI diesel engine

Bore� stroke 87.5 mm� 110 mm

Compression ratio 17.5:1

Speed 1500 rpm

Rated brake power 5.2 kW

Cooling system Water cooled

Nozzle opening pressure 220 bar (rated)

Static injection timing 23� bTDC (rated) at full load

Bonding material Nickel chrome aluminium

Thickness 100 lm

Coating material TiO2

Thickness 450 lm

063121-6 V. Ravikumar and D. Senthilkumar J. Renewable Sustainable Energy 5, 063121 (2013)

shows a decreasing trend in Brake Thermal Efficiency (BTE) when diesel is used as fuel. The per-

centage reduction in BTE with brake power varies from 3.97% to 0.714%. When B25 is used as a

fuel in a coated engine almost equal amount of BTE is obtained when compared to standard diesel

engine. At full load condition, coated B25 result is 0.38% increase in brake thermal efficiency than

that of standard diesel engine. Thermal efficiency reduces with insulation, because of increase in

the convective heat transfer, higher heat flux (increase in in-cylinder heat transfer) and deteriorated

combustion.21 The thermal resistance on the wall will allow the heat energy to the coolant as the

high oxidization properties of TiO2 absorbs some amount of heat. This could be the reason for the

decrease in brake thermal efficiency of TiO2coated combustion chamber.

C. Oxides of nitrogen

Figure 7 shows the variation of oxides of nitrogen as a function of brake power for coated

and standard engine for B25 and pure diesel. NOx comes mostly from the nitrogen present in

air coming into the engine and is generated partly due to the high combustion temperatures and

partly due to the shorter combustion durations in the coated engine.16 NOx emissions for stand-

ard engine fuelled with B25 operation is less compared to diesel at different brake power.

FIG. 5. Specific fuel consumption vs brake power.

FIG. 6. Brake thermal efficiency vs brake power.

063121-7 V. Ravikumar and D. Senthilkumar J. Renewable Sustainable Energy 5, 063121 (2013)

Comparing standard engine with coated engine using diesel as a testing fuel, the percentage

reduction in NOx emission is in the range of 13.8% to 34.91% for coated engine at different

brake power. From the figure it could be observed that NOx emission increases with increase in

brake power. Coated B25 gives less NOx emission compared to standard diesel engine. For

lower load condition 44.96% and full load condition 38.84% of NOx are reduced in B25 coated

engine. Coated B25 mode of test condition emits quite lower NOx of 257 ppm. In diesel engine,

NOx emissions are sensitive to oxygen content, adiabatic flame temperature, and spray charac-

teristics. It is well known that sulfur, aromatics, and nitrogen content of vegetable based fuels

are very small. The spray properties depend on droplet size, droplet momentum, and degree of

mixing with air and penetration rate, evaporation rate, and radiant heat transfer rate. The change

in any of those properties may change the NOx production.25 For B25, NOx emission is lower

than diesel as the above factors would have influenced the results. In general, NOx emission is

higher for coated engine because its adiabatic combustion chamber is quite higher in inside

temperature,22 whereas TiO2 coated combustion chamber, some amount of heat is absorbed by

the coating material and also the high oxidation property of TiO2 results reduced in cylinder

temperature and at the same time NOx emissions are reduced. To reduce NOx, the temperature

in the cylinder should be reduced.

D. Smoke density

Figure 8 shows variation in smoke density with respect to brake power for coated and uncoated

engine for B25 and B0 at 1500 rpm speed of the engine. Higher smoke density value of 77.7 HSU

at full load was obtained for B25. This can be attributed to poor mixture formation due to high vis-

cosity, short ignition delay and poor volatility of B25 in SE. The percentage reduction in smoke

density of coated engine for diesel at different brake power is in the range of 8.6% to 21.28% com-

pared to standard diesel engine. The highest percentage reduction of 29.74% is obtained for the

coated diesel engine compared to SE-B25 operation at lowest brake power. Equal amount of smoke

density results are obtained for CE-B25 and SE-diesel operation and the reduction percentage dif-

ference is only in the range of 1.3% to 4.06% at different brake power for coated engine. Thermal

barrier coating engines would produce less smoke and particulates than standard engine as the tem-

perature of the combustion chamber wall and the gas are high.19 Investigation of Alkidas24 shows

reduced level of smoke from thermal barrier coating engine.

E. Carbon monoxide

Carbon monoxide emission depends on many parameters such as air/fuel ratio and the

engine temperature. CO is formed by the incomplete combustion of fuel. The variation of CO

FIG. 7. NOx vs brake power.

063121-8 V. Ravikumar and D. Senthilkumar J. Renewable Sustainable Energy 5, 063121 (2013)

emission with brake power in standard and coated engine for diesel and B25 at rated engine

speed is shown in Figure 9. Compared to diesel, biodiesel emits lower CO in both the SE and

CE. This may be due to the fact that the oxygen amount in the biodiesel is higher than that of

diesel.18 Compared to standard diesel, coated diesel engine shows 42.8% reduction in CO emis-

sion and at maximum load the reduction is 13.5%. From the comparison made between stand-

ard B25 to coated B25, the results show that 45% reduction in CO emission at part load for

coated B25 and at the same time 6.25% reduction in CO emission for full load. Coated engine

gives decreasing trend in CO emission when compared to that of standard engine for all test

fuels at different brake power. Thus the results clearly indicate that the ceramics coating

decreases CO emission and radish oil methyl ester and diesel blend (B25) is the other cause for

significantly lower CO emission compared with the diesel reference fuel in both standard and

coated engine.

F. Hydrocarbon

Figure 10 shows variation in hydrocarbon with respect to different brake power for coated

and standard engine for diesel and B25. The difference in percentage reduction in hydrocarbon

of standard, coated engine for B25 is in the range of 25.9%–28.3% and 5.8%–12.8%, respec-

tively, as compared to standard diesel engine at different brake power. Compared to standard

engine coated engine gives lower emission of HC for all test fuels. From these findings, it could

FIG. 8. Smoke density vs brake power.

FIG. 9. Carbon monoxide vs brake power.

063121-9 V. Ravikumar and D. Senthilkumar J. Renewable Sustainable Energy 5, 063121 (2013)

be seen that B25 gives low amount of hydrocarbon. This may be due to higher cetane number

of B25, which is given in Table I. The high compression temperature resulting from the

insulted chamber walls extends the lean flammability limit, thus reducing HC emission

Jaichandar and Tamilporai.12 Similar findings are found by other researchers23 while the diesel

engine was operated with coated engine using ethanol as fuel. From these results it could be

observed that coated engine with B25 mode of operation gives lower HC emission compared to

coated diesel and standard diesel operation.

IV. CONCLUSIONS

In this experimental study, the piston crown surface, valves, and cylinder head of a diesel

engine are coated with a ceramic material-TiO2 by atmospheric plasma spray coating method.

Biodiesel mixture of diesel B25 and diesel fuel are used in both coated and standard engines.

The application of TiO2 coating slightly increases SFC and slightly decreases brake thermal

efficiency and also emissions of CO, Smoke density, HC, and NOx were improved. The follow-

ing conclusions may be drawn from this experimental work:

1. The percentage reduction in Brake thermal efficiency in coated engine varies from 3.97% to

0.714% compared to standard engine. At full load condition, coated B25 result shows 0.38%

increases in brake thermal efficiency compared to standard diesel engine operation.

2. Coated B25 emits almost less NOx emission compared to standard diesel engine for low load

condition 44.96% and for full load condition 38.84% of NOx are reduced, respectively. Coated

B25 mode of test condition gives lower NOx and a value 257 ppm is obtained.

3. Higher smoke density value of 77.7 HSU at full load is obtained for B25.Equal amount of

smoke density results are obtained for CE-B25 and SE-diesel operation and the difference in

reduction percentage is only in the range of 1.3% to 4.06% at different brake power.

4. The difference in percentage reduction in hydrocarbon emission of standard, coated engine for

B25 is in the range of 25.9%–28.3% and 5.8%–12.8%, respectively, as compared to standard

diesel engine at different brake power.

From the above experimental results, it is inferred that B25 with TiO2-coated mode of

engine operation gives better performance and lower emission characteristics including NOx,

without requiring any major modification of engine.

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