Environmental Engineering Reference
In-Depth Information
120
120
ALR = 1
ALR = 1.5
ALR = 2
ALR = 2.5
ALR = 3
ALR = 3.5
ALR = 4
100
100
VO
diesel
80
80
60
60
40
40
20
20
0
0
-15
-10
-5
0
5
10
15
-15
-10
-5
0
5
10
15
radial position [mm]
radial position [mm]
Fig. 10 Fuel impact on SMD at ALR = 2.5, y = 2.0 cm (left); ALR effect on SMD in VO spray at
y = 3.0 cm (right)
spray contains very
fine droplets, all around 10
µ
m. The droplets in the VO spray
are much larger, up to around 90
m at the edge of the spray. The VO spray also
has a greater range of droplet sizes. The sizes of the droplets vary over an 80
µ
m
range for the VO spray, while the droplets in the diesel spray only vary over a few
µ
µ
m. Figure
10
b shows the effect of ALR on SMD in non-reacting VO spray at
Y = 3 cm. The SMD is higher for ALR = 1, 1.5, and 2.5, although the differences
between different ALRs are less pronounced. Results show that for ALR = 3.5 and
higher, the FB injector can produce a very
fine spray of straight VO with droplet
µ
diameters of about 20
m. Note that in a reacting spray, the thermal feedback from
the
flame will help prevaporize the fuel, and thus, droplets with even smaller
diameter distributions can be expected.
To illustrate this point, transverse profiles of the measured SMD in flames of
glycerol co-combusted with methane are presented in Fig.
11
. The percentage of the
total heat release rate from glycerol and methane was varied, with some methane
being injected through the injector together with the atomizing air. For example, G68
and G45 represent 68 and 45 % of the total heat release rate from glycerol,
respectively, with the balance coming from methane. The term G45-29 signi
fl
es that
29 % of the total methane
flow rate is supplied through the atomizer. All mea-
surements were taken at approximately 10 cm from the FB injector exit as this was
the most downstream point of optical access. The G68
fl
fl
flame produces the largest
droplets even though there is signi
cant overlap among all cases. The two G45 cases
produce very similar results with the methane through the swirler case resulting in
slightly smaller droplets. In all sprays, the SMD is generally around 25
m.
These values are smaller than the measured SMD in non-reacting VO sprays in
Fig.
10
, indicating that the present glycerol measurements have bene
40
µ
-
tted from the
thermal feedback from the
flame when making comparisons. Data in Fig.
11
were
used with the corresponding velocity measurements to calculate a
fl
fl
flow-weighted
SMD for the entire spray. It resulted in
fl
flow-weighted SMDs of 40, 35, and 37
µ
m
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