Environmental Engineering Reference
In-Depth Information
From Table 25.7, it can be seen that the location of peak HRR for MOME occurs at a 360° CA
whereas for ROME it occurs at a 356° CA. It may be stated that the location of peak heat release is
closer to top dead center (TDC) as the percentage of unsaturation increases (i.e., for more unsatu-
rated biodiesel, the location of peak HRR is before TDC and for less unsaturated, it is away from
TDC). As the percentage of unsaturation increases, the peak heat release would shift toward the
left side in the HRR diagram. This may be because as the unsaturation composition increases,
the dynamic injection timing advances, which in turn can effectively bring the peak heat release
before TDC in the HRR diagram. The variation of HRR with percentage of unsaturation is shown
in Figure 25.11.
From Figure 25.12, it can be proposed that a reduction of 0.265 units (J) in peak HRR can occur
for every 1% increase in unsaturation.
25.4.2.4 Peak cylinder Pressure
Peak cylinder pressure is the magnitude of maximum pressure developed due to the combustion of
fuel by which chemical energy is converted into pressure energy. The magnitude and occurrence
of peak pressure affects engine power and emissions. Table 25.11 shows the correlation coefficient
between peak cylinder pressure and percentage of unsaturation. From the table, a high positive
correlation between peak cylinder pressure and peak HRR can be observed. This is obvious because
74
y
= -0.265
x
+ 86.55
r
2
= 0.990
72
70
68
66
64
62
40
50
60
70
80
90
100
% of unsaturation
FIGure 25.11
Variation of peak HRR with percentage of unsaturation.
69
y
= -0.125
x
+ 74.54
r
2
= 0.951
68
67
66
65
64
63
62
40
50
60
70
80
90
100
% of unsaturation
FIGure 25.12
Variation of peak cylinder pressure with percentage of unsaturation.
