Experimental Study of Biodiesel Combustion Characteristics

Experimental study of Biodiesel

combustion characteristicsBy: Eng. Marwan A. Khalil "El Swaisy"

Under supervision of:

Prof. Dr. T. M. Farag

Dr. A. A. Hanafy

Dr. M. N Anany

1

Arab Academy for Science, Technology, and

Maritime transportDepartment of Mechanical Engineering

Contents1. Introduction

2. Motivation and objectives of study

3. Experimental test rig

4. Experimental procedure

5. Results

6. Conclusions

7. Recommendations

2

Introduction

Background

• Combustion the process

• Importance of combustion

3

Introduction

Combustion Modes

• Combustion is either intermittent as in ICE's or

Continuous like in gas turbines and burners

4

IntroductionContinuous combustion

Continuous combustion features two main types of flames:

1. Premixed flames 2. Diffusion flames

5

Reactants are mixed before entering reaction zone fuel diffuses into the combustion zone

Introduction

• Diffusion flames are the focus of this study due to its

industrial importance

6

Introduction

• Diffusion flames operate optimally when burning

with high air fuel ratios for the following reasons:

1. Ensure a complete combustion process.

2. Reduced environmental impact due to the lower

thermal NOx emitted.

• High air fuel ratios can result in flame instabilities

and blow off.

7

Introduction Flame stabilization

Bluff bodies Swirlers

8

Two common methods used for flame stabilization

Introduction

Fuels for combustion

Fossil Fuel Biofuels

Introduction Fossil fuel dilemma

• Global warming

• Health concerns due to pollutants

• Limited reserves

(Natural gas and liquid petroleum fuels together will last no longer

than 64 years.)

10

Introduction

• Middle East dependency on liquid fuels

Curtsey of BBC news

Biodiesel

• Rudolf diesel

• Trans-esterification

• 1973 oil embargo

12

Introduction

Why biodiesel ?

• Renewable

• Environmental friendly

• Liquid

13

Introduction

Biodiesel blends

Researches concerned with neat Biodiesel have reported major

differences in performance Which, require engine modifications.

Volumetric blends with diesel fuel were suggested to introduce

Biodiesel as commercially ready alternative

14

Introduction

Previous studies with regards to biodiesel

• Biodiesel blends with diesel are now available in gas

stations around the world mainly for use with diesel

engines

15

Introduction

Biodiesel blends in CI engines

• Comparable thermal efficiency in CI engines

• Very good lubricating effect

• CO2 neutral

• Lower SOx

• Higher specific fuel consumption

• Slightly higher NOx

16

In comparison with

commercial Diesel fuel

Introduction

Biodiesel in Continuous Combustion applications

• Lower atomization quality

• Reaction zone of less luminosity

• Palm methyl esters were reported to produce lower soot and NOx

per unit energy compared to Diesel and Jet A1.

• Comparable visual flame length.

17

In comparison with

commercial Diesel fuel

Introduction

1. Introduction




5. Results

6. Conclusions

7. Recommendations

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Motivation and objectives of

study

• Contribute towards environment

• Production of Biodiesel in AASTMT labs from waste

vegetable oils

• Testing of the Biodiesel product

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Objectives of study

• provide a comparative evaluation of the continuous

combustion of Biodiesel blends B20 and B50

against that of Diesel under different operating

conditions. The experimental work divides into two

section:

1. Cold test "Investigating atomization quality"

2. Combustion section "Investigating Flame

characteristics"

20

Evaluate the atomization quality of:

B20, B50, and commercial Diesel

With reference to the spray cone angle

21

Cold test section

Image courtesy of Hago nozzles

Objectives of study

Combustion section investigates:

Flame structure, visual flame length, and mean combustion temperature.

Of

B20, B50, and commercial Diesel

Operating on

A/F= 20 and A/F= 30

Stabilized by swirlers of swirl numbers:

S= 0.5, S=0.87, and S= 1.5

22

Image courtesy of Babcock and Wilcox

Objectives of study

1. Introduction

2. Motivation and Objectives of study



5. Results

6. Conclusions

7. Recommendations

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1- Air blower. 2- Control valve. 3- Air duct. 4- U-tube Manometer. 5- Orifice disc. 6- Fuel tank. 7- Tank valve. 8- Oil filter. 9-

Gear pump. 10- Fuel line. 11- Pressure gauge. 12- Burner body. 13- Cooling water inlet. 14- Cooling jacket 15- Flame

pipe 16- Measurement taping 17- Cooling water outlet 18- Combustor body

Experimental test rigWater-cooled swirl stabilized combustor

1 2 3

4 5

6

7

8

9

10

12

13

14

18

16

15

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Experimental test rig

A

A

1

2

3

4

1-Swirler. 2- Pressure swirl atomizer. 3- Atomizer holder 4- fuel line

Burner assembly

Design considerations

1. Thermal output ranging between 5 to 10 kW.

2. Aspect ratio L/D = 5.

3. Swirlers were designed according to Beer and Chigier swirl no.

Equation

26

Where Ri is the inner swirler diameter, Ro is the outer swirler diameter, and

Alpha is the vane angle.



• This design facilitates:

1. Measurements and control of air/fuel mass flow rates.

2. Axial and Radial temperature measurements.

3. Axial and Radial species concentration measurements.

4. Operation with variable swirl numbers.

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Pictures through out the fabrication processes


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1. Introduction




5. Results

6. Conclusions

7. Recommendations

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Experimental procedureCalibrations

Air calibrations were done by the means of a mini-vane anemometer,

orifice disc, and a U-tube manometer.

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Air mass flow rate Vs. dH

Experimental procedureCalibrations

Fuel flow rate was calibrated against injection pressure.

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Fuel mass flow rate Vs. Injection pressure

Cold test "Spray cone angles"

Pictures of each fuel blend spray were taken for pressure range 1-4bar. Cone angles were

measured of the pictures

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Injection pressure

(bar) / Fuel typeDiesel B20 B50

1

2

3

4

Experimental procedure

Combustion section:

Flame structure, visual flame length, and mean combustion

temperature.

Through axial and radial temperature measurements

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39

A/F=20 A/F=30

Swirl number /

Fuel typeDiesel B20 B50 Diesel B20 B50

S= 0.5

S= 0.87

S= 1.5

Each of the investigated combustion parameters will have 18 values resulting from 18

experiments structured like the following table


1. Introduction

2. Motivation and objective of study



5. Results

6. Conclusions

7. Recommendations

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1- Spray cone angles

Spray cone angles are direct indication for atomization quality. The wider the

angle the better the atomization.

42

Results

43

Spray Configuration

Results

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Spray cone angles

Results

2- Flame structure

• In this experimental work flame structure is expressed in the form of temperature maps.

• The temperature maps were drawn upon measurements at 11 radial positions starting at combustor wall

ending at combustor center with an incremental step of 10mm. Radial measurements were repeated for 19

axial positions with a center to center distance of 50 mm to form a matrix of 11x19 measurements.

• Assuming Axis-symmetric process.

• Axial positions on the temperature maps are expressed with a dimensionless value x/D, where x is the axial

position and D is the combustor diameter.

• Radial positions on the temperature maps are expressed with a dimensionless value r/R where r is the radial

position and R is the combustor radius

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Results

• Temperature maps provide crucial information for

designers about:

1. High temperature regions locations.

2. Show the effect of fuel type, swirl number, and air

fuel ratio on radial and axial temperature distributions.

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Results

47

Group of S= 0.5

Results

Rad

ial d

ista

nce

r/R

Rad

ial d

ista

nce

r/R

Rad

ial d

ista

nce

r/R

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Group of S= 0.87

Results

Rad

ial d

ista

nce

r/R

Rad

ial d

ista

nce

r/R

Rad

ial d

ista

nce

r/R

49

Group of S= 1.5

Results

Rad

ial d

ista

nce

r/R

Rad

ial d

ista

nce

r/R

Rad

ial d

ista

nce

r/R

50

Group of diesel fuel

Results

Rad

ial d

ista

nce

r/R

Rad

ial d

ista

nce

r/R

Rad

ial d

ista

nce

r/R

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Group of B20 fuelResults

Rad

ial d

ista

nce

r/R

Rad

ial d

ista

nce

r/R

Rad

ial d

ista

nce

r/R

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Group of B50 fuel

Results

Rad

ial d

ista

nce

r/R

Rad

ial d

ista

nce

r/R

Rad

ial d

ista

nce

r/R

3- Mean Combustion Temperature MCT

Mean Combustion Temperature MCT is the mean value of all temperature measurements

inside the combustor.

MCT is an indication for mixing and diffusion rates within the same fuel type under different

swirl numbers and air fuel ratios.

MCT is indicative to the extracted thermal energy

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Results

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MCT at A/F= 20 MCT at A/F= 30

Results

Showing the effect of fuel type, A/F ratio and Swirl no. On MCT

1060

1080

1100

1120

1140

1160

1180

1200

1220

1240

0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6M

ean

Co

mb

ust

ion

Tem

per

atu

re i

n K

elv

inSwirl no.

Diesel

B20

B50

1140

1160

1180

1200

1220

1240

1260

1280

0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6

Mea

n C

om

bu

stio

n T

emp

era

ture

in

Kel

vin

Swirl no.

Diesel

B20

B50

4- Visual flame length

Records of visual visual flame length have been recorded for each

run in terms of dimensionless ratio x/D.

Flame length is a decisive design parameter for continuos

combustion application.

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Results

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Dimensionless visual flame length at A/F= 20 Dimensionless visual flame length at A/F= 30

Results

0

0.25

0.5

0.75

1

1.25

1.5

1.75

0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6

Fla

me

len

gth

x/D

Swirl number

Diesel

B20

B50

0

0.25

0.5

0.75

1

0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5 1.6

Fla

m len

gth

x/D

Swirl no.

Diesel

B20

B50

1. Introduction

2. Objectives of study



5. Results

6. Conclusions

7. Recommendations

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Conclusions1. B20 showed very comparable overall performance to diesel

2. Biodiesel blends B20 and B50 have lower spray cone angles than that of diesel indicating

lower atomization quality. The higher biodiesel content in the fuel mixture, the lower the

spray cone angle.

3. The higher injection pressure applied, the wider the spray angle was obtained. However,

the relative difference in spray cone angle with respect to that of diesel was reduced with the

increase in injection pressure. The relative reduction in spray cone angle was observed to

reduce from 25% at 2 bar injection pressure to 20% at 4 bar for B50.

4. The increase of air swirl numbers increased the mean combustion temperatures for all

studied cases except for B50 which experienced decrease in MCT for both air fuel ratios

investigated when the swirl number was changed from S=0.87 to S=1.5. An approximate

reduction of 6% was observed for A/F=20. On the other hand, higher percentages of

biodiesel in the fuel mixtures yielded lower mean combustion temperatures.

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4- The increase of either the air swirl number or the air fuel ratio decreases the visual flame

length. At A/F=30 the visual flame length was observed to be independent of the biodiesel content

in the fuel mixture.

5- The increase of air swirl number shifts the high temperature regions in the flame upstream.

However, the biodiesel content played insignificant role on shifting the location of the high

temperature regions. A similar trend was also observed when increasing the air fuel ratio from

A/F=20 to A/F=30.

6- The air fuel ratio reduces the overall mean combustion temperature. Moreover, the increase

in air fuel ratio affects the mean combustion temperature of biodiesel with higher rates than that of

diesel.

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Conclusions

1. Introduction




5. Results

6. Conclusions

7. Recommendations

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Recommendations

• Study the emissions of biodiesel blends per unit

energy

• Study the effect of nozzle diameter on biodiesel

blends atomization and combustion

• Study the effect of preheating on biodiesel blends

atomization and combustion

• Study the combustion of biodiesel blends higher than 20

using twin jet atomizer

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1. Introduction




5. Results

6. Conclusions

7. Recommendations

62

Done

Any questions?

Thank you.

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