Environmental Engineering Reference
In-Depth Information
Several typologies of blowers or compressors are potentially suitable for fuel
cell application. In Fig.
4.4
a flow diagram of all compressor types is reported,
distinguishing two main classes (dynamic and positive displacement) and different
typologies for each (reciprocating and rotary as positive displacement devices, and
centrifugal and axial as dynamic machines).
Among dynamic machines a centrifugal compressor results more efficient and
cheaper than axial compressors in the power range useful for vehicular applica-
tions. Motor-driven compressor/blowers for air feeding in small medium-size
FCSs are based on centrifugal type impellers [
4
]. In a side channel blower
(Fig.
4.5
) the energy coming from the motor is transferred to the air which is
accelerated radially and circumferentially. The fluid is forced into the side chan-
nels, determining a pressure and kinetic energy increase. Thus, the air is again
accelerated and transported along a spiral path through the impeller and the side
channels until it is discharged. The balanced rotating impeller represents the
unique moving part of the compressor. A further advantage of this device is that
there is no contact between the impeller and the housing, eliminating abrasion
phenomena and generally material consumption, thus improving its reliability and
durability. Finally the side channel blower is completely oil-free and produces low
noise levels.
The blowers operate in a limited pressure range, but they are able to satisfy the
overall pressure drop through stacks operating at low pressure (lower than 0.5
relative bar) [
12
,
13
].
Fig. 4.4 A basic scheme of
compressor classification
Compressors
Compressors
Dynamic
Dynamic
Positive displacement
Positive displacement
Axial
Axial
Centrifugal
Centrifugal
Rotating
Rotating
Alternative
Alternative
Fig. 4.5 Side channel
blower for fuel cell applica-
tions. A/B air inlet/outlet,
C side channels
C
C
C
C
C
C
A
B
