Combustion report.pdCombustion in Automotive Engines Gardner Compression Ignitions Engine RME

8/14/2019 Combustion report.pdCombustion in Automotive Engines Gardner Compression Ignitions Engine RME

http://slidepdf.com/reader/full/combustion-reportpdcombustion-in-automotive-engines-gardner-compression-ignitions 1/18

Combustion in Automotive Engines

Gardner Compression Ignitions Engine

RME



Introduction

One of the most important energy sources are fuels being used primarily in road vehicles and power

plants where high efficiencies is required. Using fuel, mainly fossil fuel, comes with the drawback of

emitting greenhouse gases to a large extent carbon dioxide which contributes to global warming due

to the trapped gases in the atmosphere making the planet absorb infrared radiation by the Sun and

not reflecting back. Reducing fuel consumption and emissions are the main target to be fulfilled by

today's manufactures to help the environment.

R/P ratio are defined based on the annual production either in barrels per year or cubic feet per year

depending on fuel type, as the ratio to reserves of crude oil or natural gas again in barrels or cubic

feet. These ratio currently give a steady interpretation so that there is enough for the next 40-50

years, but the problem as times goes on and the reserves do deplete, prices will increase sharply.

To prevent the use up of fossil fuel to quickly it is been suggested to look for alternative ways of

energy sources. One of the solutions are Biodiesel (RME). They have lower emissions as mentionedabove, carbon dioxide has to be reduced so biodiesels have lower greenhouse gases lowering global

warming. The most important fact is that biodiesel is renewable based on organic materials and in

theory there is an infinite amount available. Biodiesel are made of grown organic material when

grown, they will absorb carbon dioxide, hence there won't be a total net production of carbon

dioxide. There are two major drawbacks in using bio fuels, one is the increased energy requirement

of producing bio fuels compared with other fuels and, second the mass production of crops which

requires farming for only produce bio fuel taking up the space, reducing considerably other type of

farming for such as food.

PROCEDURE

The engine was ignited and then it was made to run at 1500 revolutions per minute. The shaft of the

engine was connected to the dynamometer, and then the brake load on the engine was 4kg, 8kg,

12kg, 16kg and 18kg but the last load could not be done because the engine cannot handle it so load

18kg has been discarded . Each time changing the load, the following readings have been taken:

a) air temperature near the inlet to damping vessel, (θa)

b) manometer level, (h)

c) time to the engine to consume 50 ml of fuel, (t)

d) engine speed, (N)

e) net brake load, (L)

f) exhaust temperature near the exhaust valve, (Tex)

g) mole fractions of the exhaust gas species (O2, CO, CO2, NOx)



Method to obtain the individual readings:-

Air temperature near the inlet to damping vessel, (θa)

The temperature of air was measured from the thermometer which was located at the throat of the

air box. The air box is the box which is used to damp down the pressure fluctuations and the air flowin the air box before it comes into the engine.

Manometer level, (h)

The manometer is connected to the throat of the air box, and it gives the pressure difference

between the atmosphere and inside the air box. The obtained pressure difference is then used to

calculate the mass flow rate of air going in the engine.

Time to the engine to consume 50 ml of fuel, (t)

The fuel was flowing from the fuel tank into the fuel flow meter, where the tube was calibrated into50 ml gaps. The tube was filled in through a valve, then the time was noted for the drop in fuel level

in one gap. This gave the time for the engine to consume 50 ml of fuel, to obtain the mass flow rate.

Engine speed, (N)

The engine speed was set to 1500 revolution per minutes which has not been changed.

Net brake load, (L)

It is the applied load on the engine which can be adjusted and shown on a big dial.

Exhaust temperature near the exhaust valve, (Tex)

On different brake load when the crank angle and pressure was recorded the exhaust temperature

was then also recorded.

Mole fractions of the exhaust gas species (O2, CO, CO2, NOx)

The mole fractions of the exhaust gases were measured from the computer giving the specific

readings.



My observed values

Brake Load

(kg)

4 8 12 16

θa (oC) 14 14 14 15

h(mm H2O) 56 54 52 44t (s) 54 38 30 24

Tex (oC) 216.24 272.36 332.42 425.95

O2 (%) 15.05 12.76 10.16 6.28

CO (%) 0.08 0.08 0.07 0.08

CO2 (%) 4.44 6.29 8.41 11.45

NOx (ppm) 347 604 820 720

HC (ppm) 480 460 510 630



Pressure - Crank Angle

0

1

2

3

4

5

6

-800 -600 -400 -200 0 200 400 600

Pressure - Crank Angle 4Kg

0

1

2

3

4

5

6

-800 -600 -400 -200 0 200 400 600


0

1

2

3

4

5

6

-800 -600 -400 -200 0 200 400 600




A more closer view:

0

1

2

3

4

5

6

-800 -600 -400 -200 0 200 400 600


0

1

2

3

4

5

6

-200 -150 -100 -50 0 50 100 150 200


0

1

2

3

4

5

6

-200 -150 -100 -50 0 50 100 150 200




It can be observed that increasing the net break load increase the pressure in firing cycles. A

constant maximum pressure can be observe slightly after the top-dead centre throughout

all Pressure - Crank Angle graphs.

0

1

2

3

4

5

6

-200 -150 -100 -50 0 50 100 150 200


0

1

2

3

4

5

6

-200 -150 -100 -50 0 50 100 150 200




P-V Diagrams

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0E+00 2.0E-04 4.0E-04 6.0E-04 8.0E-04 1.0E-03 1.2E-03 1.4E-03 1.6E-03

C y l i n d e r P r e s s u r e / M P a

Volume /m^3

Pressure - Volume 4Kg

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0.0E+00 2.0E-04 4.0E-04 6.0E-04 8.0E-04 1.0E-03 1.2E-03 1.4E-03 1.6E-03

C y l i n d e r P r e s s u r e / M P a

Volume /m^3




Pressure - Volume graphs are constant for the first two break load but increasing for the

other higher break loads. Pressure increased for the last two higher load due the more workso more fuel consumption, increasing the fuel air ratio.

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

0.0E+00 2.0E-04 4.0E-04 6.0E-04 8.0E-04 1.0E-03 1.2E-03 1.4E-03 1.6E-03 C y l i n d e r P r e s s u r e

/ M P a

Volume /m^3


-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

5.0

0.0E+00 2.0E-04 4.0E-04 6.0E-04 8.0E-04 1.0E-03 1.2E-03 1.4E-03 1.6E-03 C y l i n d

e r P r e s s u r e / M P a

Volume /m^3




CALCULATIONS

1. Brake Power (mass load of 4kg)

The brake power () was calculated from:

Where,

L = Weight of brake load = ( 4 kg × 9.81 m/s2 ) = 39.24 N

N = Speed of Engine = 1500 rpm =

= 25 rev/s

α = 0.447 m-1

(constant and was already given)

Brake mean effective pressure (bmep)

This was calculated from the following equation:

Where,

n = Number of revolutions per cycle = 2

Vs = Volume which is swept in one cycle of the engine = 1394.8 × 10-6

m3

σ = Number of cylinders = 1

Mass flow rate of the fuel (mf )

The mass flow rate of the fuel was calculated using:-

Where,

ε = Mass of fuel of 50ml = 0.0178 kg

t = time for engine to consume 50 ml of fuel = 54 s



Mass flow rate of air (ma)

The following equation was used to calculate:-

Where,

Cd = discharge coefficient ( constant) = 0.6

A = Area of orifice of the air box = 6.424*10-4

m2

ρa = density of air = 1.2 kg/m3

ΔP = pressure drop across orifice = 549.36 Pa

Volumetric Efficiency (ηv)

The volumetric efficiency was calculated using the following formula :-

Mechanical efficinecy ()

Specific fuel consumption (kg/MJ)

Thermal efficiency (ηth):

where ΔHL = specific enthalpy of reaction = 38.6 MJ/kg



Equivalence ratio ( )

Where,

F/A = specific fuel/air ratio = 0.02302

(F/A) stoich = stoichiometric fuel/air ratio = 0.08417

My calculated values - Results

Brake Load/kg 4 8 12 16

Brake power/W 2193.959732 4387.919 6581.879 8775.839 Ws

bmep/kPa 125.9087364 251.8175 377.7262 503.6349 bmep

Fuel Mass Flow Rate /kg/s 0.000325556 0.000463 0.000586 0.000733 mf

Air Mass Flow Rate /kg/s 0.014141151 0.013886 0.013627 0.012535 ma

Volumetric efficiency 0.662484744 0.650547 0.638386 0.58723 ηv

Mechanical efficiency 0.022207211 0.036834 0.05437 0.074176 ηmech

Specific Fuel Consumption /kg/MJ 1.48387E-07 1.05E-07 8.9E-08 8.35E-08 sfc

Thermal Efficiency 0.174588742 0.245717 0.290981 0.31038 ηth

Equivalence Ratio 0.273499662 0.395789 0.510883 0.694236 φ



Based on my calculated values and of Group 5 the following graphs have been drawn:

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0 0.0002 0.0004 0.0006 0.0008

W

kg/s

Brake Power/Fuel mass flow rate

Group 8

Group 5

0

100

200

300

400

500

600

0 5E-08 0.0000001 1.5E-07 0.0000002

K P a

kg/MJ

bmep/sfc

Group 8

Group 5



0

0.002

0.004

0.006

0.008

0.01

0.012

0.014

0.016

0 100 200 300 400 500 600

k g / s

KPa

Fuel mass flow rate/bmep

Group 8

Group 5

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 100 200 300 400 500 600

KPa

(F/A)/bmep

Group 8

Group 5

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 100 200 300 400 500 600

KPa

Volumetric efficiency/bmep

Group 8

Group 5



0

50

100

150

200

250

300

350

400

450

0 100 200 300 400 500 600

D e g r e e s

KPa

Exhaust Temperatur/bmep

Group 8

Group 5

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 100 200 300 400 500 600

Equivalence Ratio/bmep

Group 8

Group 5

0

2

4

6

8

10

12

14

16

18

0 0.2 0.4 0.6 0.8

O x y g n e %

Oxygen/Equivalence Ratio

Group 8

Group 5



0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0 0.2 0.4 0.6 0.8

C O %

CO/Equivalence Ratio

Group 8

Group 5

0

2

4

6

8

10

12

14

0 0.2 0.4 0.6 0.8

C O 2 %

CO2/Equivalence Ratio

Group 8

Group 5

0

200

400

600

800

1000

1200

0 0.2 0.4 0.6 0.8

N O x / p p m

NOx/Equivalence Ratio

Group 8

Group 5



0

200

400

600

800

1000

1200

0 0.2 0.4 0.6 0.8

N O x / p p m

NOx/Equivalence Ratio

Group 8

Group 5

0

100

200

300

400

500

600

700

0 0.2 0.4 0.6 0.8

H y d r o c a r b o n / p p m

Hydrocarbon/Equivalence Ratio

Group 8

Group 5



Discussion

From the graph (Brake power/ Fuel mass flow rate) and from the results table it can be seen

that increasing the break load increases the brake power which much more for group 8 than

5. The same trend can be seen with all graphs including the bmep value on the x-axis forboth group at a predicable rate but for group 8 higher values than for group 5 due to the

higher engine speed.

From the oxygen/equivalence ratio graph it can be observed that both groups are using the

nearly same amount of oxygen a bit higher for group 5. This shows that group 8 F/A was

much higher than of group 5. Interesting observation can be made of CO realise, that group

5 is much higher at beginning then dropping very quickly. For group 8 CO levels were pretty

much constant at nearly the same level. CO2 is as expected much higher for group 8 than

group 5 due to the higher engine speed because of higher fuel consumption. Nox was

released a higher rate from group 5 than group 8 were it actually has dropped a higher

break load. Hydrocarbon were released at very low levels for group 5, comparing the very

high increasing emission of group 8 meaning a lot of unburned fuel leading to low efficiency.

The stoichiometric equation for RME burning in air is given below:

2222222821 N52.101OH14CO21)N76.3O(27OHC

Comparing these values to general diesel specifications, specially air/fuel ratio it can be seen

that RME requires more fuel due to the lower energy density. RME produces loweremissions of CO, Nox and Co2 compared conventional petroleum diesel.

Conclusion

It can be conclude that running the engine at lower speed will result in higher efficiencies

and less emissions.

Documents

Combustion report.pdCombustion in Automotive Engines Gardner Compression Ignitions Engine RME