Filter
Top Products
TRG-TRC013-EN 25
period one
Fan Performance
notes
Unlike the previous fan performance curves, those of the VPVA fan are plotted
on the basis of airflow, at various blade pitches, versus total pressure (static
pressure plus velocity pressure). This type of fan generates high air velocities
and, therefore, high velocity pressures. To fully evaluate its performance, total
pressure is used to demonstrate both the static and velocity pressure
components.
The dashed line defines the upper limit of airflow and total pressure, above
which a surge, or turbulent, condition is encountered. In addition, curves are
plotted that define fan total efficiency at various airflows, total pressures, and
blade positions.
Fan total efficiency expresses the percentage of input power that is realized
as useful work in terms of total pressure. It is calculated by substituting total
pressure for static pressure in the static efficiency equation.
airflow
airflow
total pressure
total pressure
bl
ade
p
i
t
c
h
(
a
ngl
e)
bl
ade
pi
t
c
h
(
an
gl
e)
50%
50%
70%
70%
80%
80%
85%
85%
50º
50º
40º
40º
35º
35º
30º
30º
20º
20º
15º
15º
55º
55º
45º
45º
25º
25º
i
n
p
u
t
p
o
we
r
i
n
p
u
t
p
o
we
r
surge region
surge region
Figure 36
Total Efficiency (%)
Airflow Total Pressure×
Constant Input Power×
-------------------------------------------------------------------
=