1. Experimental study on spray characteristics of diesel and
biodiesel (Jatropha oil methyl ester) for various chamber
pressures in a constant volume chamber
Presented by
Dr. N. NALLUSAMY
Professor / Mechanical Engg.
SSN College of Engineering
OMR, Kalavakkam, Chennai

2. Requirement of alternate fuels
 Petroleum products consumption is increasing day-byday as the number of vehicles-on-road increases.
 Consumption of hydrocarbon fuel increases the
environmental pollution also.
 There is a need to solve these twin problems–fuel supply
and environmental pollution.
 Conventional fuels emit more hydrocarbon emissions,
oxides of nitrogen, sulphur and carbon monoxides as
compared to renewable biofuels.

3. Requirement of alternate fuels …
 Various alternative fuels are considered as substitute
fuels for petroleum products.
 Efforts were made to analyze the suitability of the fuel
and its demonstration in the last two decades.
 Renewable fuels have received more attention as
- it reduces the environmental pollution (by completing
carbon cycle) and
- reduces the import of petroleum based fuels.

4. Requirement of alternate fuels …
Hence, researchers and scientific community
worldwide
have focused on
• development of biodiesel
• optimization of the processes to meet the
standards and specifications needed for the fuel
to be used commercially.

5. Biodiesel from vegetable oils
• Among the different renewable fuels considered for the
use, the biodiesel derived from vegetable oils (available
from plant sources) are realistic alternatives to diesel fuel
because they are renewable in nature and
environment-friendly.
BIO-DIESEL:
“A fuel comprised of mono-alkyl esters of long chain fatty
acids derived from vegetable oils or animal fats,
designated B100, and meeting the requirements of
ASTM D 6751”

7. Biodiesel feedstocks
•
•
•
•
•
•
•
•
•
•
Jatropha
Pongamia Pinnata
soybean
sunflower
R
apeseed
Coconut oil
Palm oil
Cotton seed oil
Castor oil
W
aste cooking oil

8. Advantages of Biodiesel
 It is renewable and energy efficient
 It displaces petroleum-derived diesel fuel
 It can be used as a 20% blend in most
diesel equipment with no or only minor
modifications
 It is environment friendly and does not produce
greenhouse effects, because the balance between
the amount of CO2 emissions and the amount of CO2
absorbed by the plants producing vegetable oil is
equal.

9. Advantages of Biodiesel…
 It can reduce tailpipe emissions, including air toxics
 Biodiesel has a higher oxygen content (usually 10 to
12
percent) than petroleum diesel. This should result in
lower
pollution emissions.
 Biodiesel has a higher cetane number than petroleum
diesel
because of its oxygen content.
 The higher the cetane number, the more efficient the
fuel
the engine starts more easily, runs better and burns

10. AVERAGE BIODIESEL EMISSIONS COMPARED TO
CONVENTIONAL DIESEL, ACCORDING TO EPA
• Emission Type
B100
B20
• Unburned Hydrocarbons : - 67% ‐ 20%
• Carbon Monoxide
• Particulate Matter
• Nox
‐ 48%
‐ 12%
‐ 47% ‐ 12%
+ 10%
+ 2%

11. Drawbacks of using biodiesel as fuel in IC
engines
• It is commonly accepted by researchers that
- the use of biodiesel will lead to loss in engine
power mainly due to the lesser calorific value of
biodiesel compared to diesel, (~ 4%)
- but there exists power recovery for biodiesel
engine as the result of an increase in biodiesel fuel
consumption.
• An increase in biodiesel fuel consumption, due to low
heating value and high density and viscosity of biodiesel,
has been found,
• but this trend will be weakened in diesel & biodiesel
blends as the proportion of biodiesel reduces in the
blend.

12. Biodiesel production methods

The liquid fuel produced has almost identical chemical
components to conventional diesel fuel.
4. Transesterification – also called alcoholysis – chemical
reaction of vegetable oil or animal fat with an alcohol
(methanol) in the presence of a catalyst to form
biodiesel (chemically called methyl esters) and glycerol.
Catalyst: NaOH, KOH
Catalyst
Triglycerides +Alcohol
Alkyl ester +Glycerol

14. Spray Characteristics in Diesel Engines
 In Diesel engines the combustion process basically
depends on
- fuel injected into the combustion chamber and its
interaction with the air.
 The characteristics of the diesel spray have affected
certain aspects of engine performance, such as
- the power, fuel consumption, and emissions.
 Therefore, it is essential to investigate the effects of
various injection parameters to optimize the injection
process.

15. Spray Characteristics in Diesel Engines
 Several meaningful factors that have an influence, but the
most important one is the diesel spray, more specifically the
penetration of the liquid length of the spray through the
combustion chamber or piston bowl.
 The analysis of the liquid length penetration is very useful
to determine the geometric design of Diesel engine
combustion chambers with direct injection.

16. Macroscopic Characteristics
The macroscopic description of a diesel spray generally
emphasize the interaction of the latter and the control
volume
where it is injected and mixed, and because of this the
diesel
spray can be defined with the following physical
parameters :
1. Spray tip penetration (spray length)
2. Spray angle
3. Break up length

17. Main integral characteristics of the spray are: breakup
length, tip penetration length and spray cone angle.

18. Spray characteristics
The injection front penetration (S) (Spray tip penetration
length)
is defined as the total distance covered by the spray in a
control
volume.
i.e. Length from the nozzle tip to the tip of the spray

19. Spray characteristics
Cone angle:
• The cone angle is defined as the angle formed by two
straight lines that start from the exit orifice of the nozzle
and tangent to the spray outline (sprays morphology) in
a determined distance. (equivalent to 60 times exit
diameter of the nozzles orifice)
• This angle usually is between 5 and 30 degrees.
• This determines greatly the fuels macroscopic
distribution in the combustion chamber

20. Spray characteristics - Sauters mean diameter
• The macroscopic description is characterized by the
content of droplets of diverse sizes and the changes in
their special kinetics.
• For example, the atomization mechanism is
responsible for distributing the droplets in the injection
process and to a great extent the good distribution of the
droplets in relation to their size depend on it.
• A determined medium diameter represents the
equivalent diameter that characterizes the entire group
of the droplets of the spray.

21. Objective of the experimental study
 The spray characteristics of fuel mainly depend on fuel
injection process, fuel density, fuel viscosity, ambient
pressure and temperature.
 The effect of fuel injection pressure and ambient pressure
are very important parameter directly affecting spray
structure.
 This study investigates the effects of chamber (ambient)
pressure on the spray characteristics such as spray angle and
spray tip penetration in a constant volume chamber under non
evaporating conditions by image processing techniques.

22. Objectives ...
Images of spray under non-evaporative conditions are
captured by a high speed digital camera for various chamber
pressure.
The macroscopic (spray) characteristics such as spray cone
angle and spray penetration are measured experimentally
from the images.
Spray characteristics will be compared with that of diesel
in order to understand the behaviour of biodiesel.

23. SCHEMATIC OF EXPERIMENTAL SETUP

24. EXPERIMENTAL SETUP

25. Steel chamber with heater

26. Properties of diesel, Jatropha vegetable oil
and Jatropha methyl ester (biodiesel)
Property
Diesel
Jatropha oil Raw Jatropha
methyl ester Vegetable Oil
(Biodiesel)
Density(kg/m3)
840
875
917
Viscosity(400C)CP
3.4
4.27
35.58
Flash point(0C)
71
77
229
Fire point(0C)
103
270
300
Cetane number
48-56
51-52
23-41
38.5
39.071
Calorific value (MJ/kg) 45.343

27. Experimental data
Injection parameters:
Injection pressure
- 230 bar
Chamber pressure
- 1,2,3,4& 5 bar
Chamber temperature - 300 K
Fuel & air temperature - 300 K
Nozzle diameter
- 0.231 mm
Injection duration
- 1.2 ms
The spray images were captured using high speed digital
Camera (Nikon D200)

28. SPRAY IMAGES- DIESEL
 Chamber pressure 1 bar
 Chamber pressure 2 bar

29.  Chamber pressure 3 bar
 Chamber pressure 4 bar

30.  Chamber pressure 5 bar

31. SPRAY IMAGES OF BIO DIESEL
 Chamber pressure 1 bar
 Chamber pressure 2 bar

32.  Chamber pressure 3 bar
 Chamber pressure 4 bar

33.  Chamber pressure 5 bar

34. Parameters to studied




Spray tip penetration (spray length)
Spray cone angle
Sauter mean diameter (SMD)
Spray volume

35. Images of diesel spray by varying the chamber pressure (1, 2, 3, 4 and
5 bar), injection pressure 230 bar and ambient temperature 300K
For these images
• an initial spray angle was measured as the angle enclosing the
initial part of the visible spray from the injector tip
• and spray penetration was measured from the nozzle tip to the
tip of the spray.

36. EXPERIMENTAL RESULTS
DIESEL

37. Images of biodiesel spray by varying the chamber pressure (1, 2, 3, 4
and 5 bar), injection pressure 230 bar and ambient temperature 300K

38. EXPERIMENTAL RESULTS
BIODIESEL

39. Variation of spray tip penetration for diesel and
JOME at various chamber pressures.

40. RESULTS & DISCUSSION
SPRAY PENETRATION
LENGTH
• Spray length decreases with increase in chamber pressure for both diesel
and bio diesel.
• As the chamber pressure increases the density of (ambient gas)
nitrogen also increases due to which shear resistance increases
near the spray tip. This results in reduction of droplet velocity
Hence the spray length decreases.
• The spray tip penetration for diesel is found to be the lower for all
chamber pressures, this is because the density and viscosity of
diesel is lower, hence it atomizes more rapidly compared to
biodiesel fuels.

41. Experimental and theoretical values of Spray
tip penetration for JOME
(1)
For jet atomization regime, spray penetration was found to follow the
1
relationship proposed by Dent et al [9].
1
 ∆ 4
P
( td n ) 2
S = 2.95
ρ 
 g 

42. Experimental and theoretical values of Spray tip
penetration for Diesel

43. Experimental values of spray cone angle ( θ )
Chamber
pressure, bar
1
2
Diesel
14.28
14.85 15.25
15.57 15.83
Biodiesel
14.83
15.1
15.93 16.15
(JOME)
3
15.64
4
5

44. SPRAY CONE ANGLE
 When the chamber pressure is low the fuel droplets have higher
initial velocity due to lower shear resistance from ambient
chamber air density hence the fuel droplets travel faster along
the axis than in the radial direction, therefore the cone angle of
the test fuels are lowest at chamber pressure of 1 bar.
 The spray cone angle for diesel is lower than biodiesel because it
travels faster along the axis rather than the radial direction.

45. Sauter mean diameter (SMD)
• The quality of the atomization of a liquid spray can be
estimated on the medium diameter of the droplets.
• A determined medium diameter represents the
equivalent diameter that characterizes the entire group
of droplets of the spray.
• Medium diameter is that which defines the
characteristics of a population of drops presents in a
sample.

46. Sauter mean diameter (SMD)…
• Elkotb [10] suggested a SMD correlation involving
variations in viscosity, density and surface tension.
• Ejim et al [11] suggested that SMD correlation by Elkotb
was also applicable to biodiesel which is given by the
equation
SMD = 6156 ѵ0.385σ0.737ρf0.737ρg0.06∆p-0.54 (µm)
σ - Surface tension, N/m
ѵ - Kinematic viscosity, m2sec
ρf - Density of fuel, Kg/m3
ρg - Density of chamber gas (air), kg/m3
∆P - Difference between injection pressure and chamber pressure (bar)

47. Estimated SMD for JOME and diesel for various
Chamber pressures.

48. SMD variation
• With injection pressure kept constant at 230 bar, JOME
has greater SMD when compared to diesel.
•
When the ambient air pressure in the chamber is
increased from 1,2,3,4 and 5 bar, SMD also increases.
•
The physical properties of liquid fuel that affect its
atomization in the process of combustion are viscosity,
density and surface tension.

49. SMD variation …
• The higher viscosity, surface tension and density are
responsible for larger values of SMD for JOME.
•
The viscosity is regarded to have highest contribution to
the change in SMD.
•
High viscosity suppresses the instabilities required for
the fuel jet to break and thus delays atomization.
•
An increase in fuel density adversely affects atomization
whereas high surface tension opposes the formation of
droplets from liquid fuel.

50. Spray volume
To understand fuel-air mixing, the spray volume is
estimated.
Fuel spray is assumed to consist of a cone and half a
sphere, thus
spray volume is described by the correlation suggested by
Delacourt tet= 1 πS 3 (t ) tan 2 θ (1 + 2 tan(θ / 2))
V ( ) al. [12] which is given by
3
2 (1 + tan(θ / 2)) 3

51. Spray volume …

52. Spray volume …
 With the increase of ambient density, spray volume is
decreased remarkably due to the increased spray angle.
 High ambient density supplies strengthened resistance
to fuel spray
 inhibits spray development in axial direction, which
results in a wide spray angle.
 droplet velocity which was high initially, retards near the
tip of the spray leading to reduction in spray volume.

53. Conclusions
 The experimental setup has been developed to study the
spray characteristics of diesel and bio diesel in a
constant volume chamber.
 From the images - spray angle , spray length and SMD
were calculated.
The experimental results shows that
 as the chamber pressure is increased, the spray cone
angle and Sauter Mean Diameter (SMD) increased for
JOME
 but the spray tip penetration and spray volume
decreased.

54. Conclusions ….
 When
compared to diesel, JOME gives longer spray tip
penetration and larger SMD due to the higher density,
viscosity and surface tension of the fuel.
 From the results we can see that the values obtained for
diesel and bio diesel are not exactly the same but the
values still lie within the permissible limits.
 Therefore diesel can be completely replaced with
biodiesel but it will reduce the performance of the engine.

55. Effect of injection pressure
(180 to 230 bar)
• Spray penetration length increases for biodiesel with
increase in injection pressure.
• Reason: increase in fuel viscosity prevented the breaking
of spray jet, resulting in an increase in the size of the
spray droplets.
• Viscosity and surface tension are higher for biodiesel
• Spray angle increases with increase in injection pressure
for biodiesel.

56. CONCLUSION….
 Overall, biodiesel, especially for the blends with a small
portion of biodiesel, is technically feasible as an
alternative fuel in CI engines with no or minor
modifications to engine.
 For environmental and
economic reasons, their
popularity may soon grow.
 However, more researches
and development in biodiesel
resources and engine design
are needed.

57. THANK YOU