Environmental Engineering Reference
In-Depth Information
taBle 25.11
Pearson correlation coefficient among Peak cylinder
Pressure, Peak hrr, and Percentage of unsaturation
Pearson correlation
coefficient
x
variable
y
variable
Peak HRR
Peak cylinder pressure
0.975
Percentage of unsaturation
-0.975
13.4
y
= 0.012
x
+ 12.188
r
2
= 0.954
13.2
13.0
12.8
12.6
12.4
12.2
0
10 0 0 0 0 0 0 0 0
100
Percentage of unsaturation
FIGure 25.13
Variation of BSEC with percentage of unsaturation.
the magnitude of peak cylinder pressure must always be proportionate with peak HRR. It could also
be seen from the table that the peak cylinder pressure decreases with an increase in unsaturation
percentage.
The influence of unsaturation percentage on peak cylinder pressure is shown in Figure 25.12.
From the fitted line equation
y
= - 0.125
x
+ 74.54 shown in Figure 25.13, it can be seen that every
1% increase in unsaturation percentage may cause a reduction of 0.125 bar in peak pressure.
25.4.2.5 Brake specific energy consumption
Brake specific energy consumption (BSEC) is defined as the energy required to develop a unit power in
unit time. Brake specific fuel consumption (BSFC) is the quantity of fuel required for developing unit
power in unit time. In the case of BSFC, the effect of fuel density alone is considered. But in BSEC,
both the density and the heating value of a fuel are taken into account. When comparing different fuels
with different densities and heating values, it is essential to discuss BSEC rather than BSFC.
The BSEC can be obtained by multiplying the heating value with BSFC. From Table 25.12, it
can be observed that the BSEC is higher for sunflower biodiesel and lower for coconut biodiesel as
compared with other biodiesel fuels. From the table, it can also be seen that the order of magnitude
of BSEC is exactly matched with the order of magnitude of unsaturation percentage. From the
correlation analysis, it was found that the BSEC was highly positively correlated with density and
percentage of unsaturation. It can be noted that the BSFC increases with a decrease in heating value.
Figure 25.13 depicts the variation of BSEC with percentage of unsaturation.
From the fitted line equation
y
= 0.012
x
+ 12.188, the gradient between BSEC and percentage of
unsaturation can be proposed as 0.0116. Every 1% increase in unsaturation may result in an increase
of 0.0116 units (MJ/kWh) in BSEC.
