Air Conditioning Compressors - Delphi

Th e h i g h e ff i c i e n c y o f m o d e r n e n g ines can
l e a d t o t h e s i tu a t i o n i n which i n s u ff icient re-
j e c t e d h e a t i s ava i l a b l e fo r comfo r t heating .
Th i s fa c t h a s p r o m p t e d t h e s u g g estion that
t h e a i r c onditioning s ys tem b e o p erated in
r eve r s e a s a h e a t p u m p t o s u p p l e ment the
e n g i n e h e a t a n d t h e v i a b i lit y o f the concept
h a s b e e n d e m o n s t r a t e d o n a n u m b er of plat-
fo r m s . Th e i m p l i c a t i o n s fo r t h e c o mpressor
a r e t h a t t h e r e q u i r e d o perating life can be
n e a r l y d o u b l e d a n d t h e c ompressor ambient
s a fe o p e r a t i n g t e m p e r a tu r e r a n g e must be
ex t e n d e d d ow nwa r d s t o minus 20°C.
D e l p h i ve h i c l e w i t h H e a t Pu m p s u p p l e m e n t a r y h e a t i n g
R e f r i g e r a n t I s s u e s
Th e a u t o m o t i ve a i r c o n ditioning industr y
r e s p o n d e d p r o - a c t i ve l y t o t h e d emands of
t h e 19 8 7 M o n t r e a l Pr o tocol a n d by 1994,
2 ye a r s e a r l y, t h e ch a n g e ove r f r o m R12 to
R 13 4 a wa s c o m p l e t e fo r a ll ve h icle produc-
t i o n l i n e s i n t h e d eve l oped wo rld. It soon
b e c a m e a p p a r e n t t h a t t h is m ay n ot be the
e n d o f t h e s t o r y a n d w i th i ncreasing pene-
t r a t i o n o f a i r c o n d i t i o n i n g i n t h e European
m a r ke t t ogether w i t h t he d e mands of the
Kyo t o Pr o t o c o l p r e s s u r e has b u ilt to make
ch a n g e s t o s t i l l f u r t h e r r e d uce the potential
c o n t r i b u t i o n o f a i r c o nditioning systems
t o g l o b a l wa r m i n g . A n ew D i r ective has
r e c e n t l y c o m p l e t e d i t s p r o g r ess t h r ough the
E u r o p e a n l e g i s l a t i ve p r o cess. I t r e q uires the
e l i m i n a t i o n o f R 13 4 a f r om a ll n ew models
f r o m 2 011 a n d f r o m a l l n ew ve h icles by 2017.
Th e c u rrently c o n s i d e r ed alternatives are
R 15 2 a w i th a g l o b a l wa rming p o t e ntial less
t h a n 10 % o f t h a t o f R 13 4 a, o r t h e so-called
‘ n a tu r a l ’ r e f r i g e r a n t R 744 ( carbon dioxide).
R 15 2 a h a s t h e r m o d y n amic characteristics
ve r y s i m i l a r t o t h o s e o f R 13 4a a nd will be
d i r e c t l y u s a b l e w i t h current c ompressor
t e ch n o l o g y. I t s p o t e n t i a l d r aw back is a
d e g r e e o f f l a m m a b i l i t y that h as made the
i n d u s t r y reluct a n t t o c onsider i t. More re-
c e n t l y o t h e r l a r g e ch e m i c al c o m panies have
a n n o u n c e d t h e p o t e n t i a l ava ilabilit y of new
a l t e r n a t i ve s . L i tt l e i s k n ow n a b o u t them at
t h i s s t a g e b u t i t i s a s s u m e d t hat they too
wo u l d f u n c t i o n w i t h c u rrent c ompressor
t e ch n o l o g y. Th e r e m u s t b e a q u estion as to
w h e t h e r t h e n e c e s s a r y d eve l o pment and
testing and then implement ation of the
necessar y manufacturing capacit y can be
completed in time to meet the requirements
of the European legislation. If R744 becomes
the chosen route the implications for com-
pressor technology are ver y far-reaching . Air
conditioning systems with R744 need com-
pressors with displacement of only a fifth
of that required for R134a but operating at
much higher pressures. Discharge pressures
of 120 bar are normal compared with a t ypi-
cal 18 bar for an R134a system. As can be
imagined, these factors have big implications
for the compressor layout and structural
strength requirements and also represent a
particularly severe shaft seal challenge.
Pressure - MPa
100
10
1
100
-40°C
0°C
200
40°C
80°C 120°C 160°C 200°C
0°C
40°C
300 400
Enthalpy - kJ/kg
500
I d e a l i ze d p r e s s u r e e n t h a l py d i a g r a m o f C O 2 c yc l e
C o m p r e s s o r
Te c h n o l o g i e s
Air conditioning began to become available
for vehicles in the early 1950s. From the
beginning a number of different compressor
technologies have been used. The earliest
systems used piston compressors in various
configurations. The Frigidaire F5, a five pis-
ton wobble plate configuration, used in the
earliest GM vehicles with air conditioning
was first produced in 1956 – it weighed in at
18kg! The R4 compressor with a scotch yoke
mechanism was first produced by Harrison
(now Delphi) in 1974 and remained in pro-
duction until 1995. It was 190mm in overall
diameter and weighed 9kg .
A n e a r l y
c o m p r e s s o r,
t h e D e l p h i R 4
80°C
120°C
600
160°C
200°C
700