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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)
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
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