developmental considerations on the free-piston stirling power convertor … · 2013-04-10 ·...
TRANSCRIPT
Developmental Considerations on the Free-Piston Stirling Power Convertor for Use in Space
by
Jeffrey Schreiber presented at the 2006 IECEC
Abstract Free-piston Stirling power conversion has been considered a candidate for radioisotope power systems for space for more than a decade. Prior to the free-piston Stirling architecture, systems were designed with kinematic Stirling engines with rotary alternators to convert heat to electricity. These systems were proposed with lightly loaded linkages to achieve the necessary life. When the free-piston configuration was initially proposed, it was thought to be attractive due to the relatively high conversion efficiency, acceptable mass, and the potential for long life and high reliability. These features have consistently been recognized by teams that have studied technology options for radioisotope power systems. Since free-piston Stirling power conversion was first considered for space power applications, there have been major advances in three general areas of development: demonstration of life and reliability, the success achieved by Stirling cryocoolers in flight, and the overall developmental maturity of the technology for both flight and terrestrial applications. Based on these advances, free-piston Stirling convertors are currently being developed for a number of terrestrial applications. They commonly operate with the power, efficiency, life, and reliability as intended, and much of the development now centers on system integration. This paper will summarize the accomplishments of free-piston Stirling power conversion technology over the past decade, review the status, and discuss the challenges that remain.
https://ntrs.nasa.gov/search.jsp?R=20070017910 2020-04-29T21:10:50+00:00Z
Nat
iona
l Aer
onau
tics
and
Spac
e Ad
min
istra
tion
ww
w.n
asa.
gov
Dev
elop
men
tal C
onsi
dera
tions
on
the
Free
-P
isto
n S
tirlin
g P
ower
Con
verto
r for
Use
in
Spa
ce
pres
ente
d at
the
2006
Inte
rnat
iona
l Ene
rgy
Con
vers
ion
Engi
neer
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Con
fere
nce
San
Die
go, C
A
byJe
ff S
chre
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NA
SA
Gle
nn R
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Cle
vela
nd, O
H
1
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This
wor
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OE)
St
irlin
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isot
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Gen
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RG
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pro
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and
thro
ugh
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cien
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pre
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of th
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refle
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of
the
Nat
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l Aer
onau
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and
Spac
e A
dmin
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2
Nat
iona
l Aer
onau
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and
Spac
e Ad
min
istra
tion
ww
w.n
asa.
gov
Dev
elop
men
t of S
tirlin
g
•S
tirlin
g te
chno
logy
dev
elop
men
t can
be
view
ed a
s ha
ving
gon
e th
roug
h 3
gene
ral p
hase
s–
Ear
ly a
ir en
gine
s–
Adv
ance
d ki
nem
atic
engi
nes
–Fr
ee-p
isto
n S
tirlin
g
•Th
e pa
per g
ives
an
over
view
of t
he p
ast
deve
lopm
ent,
and
then
sum
mar
izes
the
curr
ent
stat
us
–P
artic
ular
em
phas
is is
pla
ced
on th
e ad
vanc
es b
etw
een
1999
and
200
5, y
ears
of r
adio
isot
ope
gene
rato
r de
velo
pmen
t
3
Nat
iona
l Aer
onau
tics
and
Spac
e Ad
min
istra
tion
ww
w.n
asa.
gov
Dev
elop
men
t of S
tirlin
g
•S
tirlin
g ai
r eng
ines
wer
e po
pula
r fro
m 1
816
until
abo
ut 1
900
–O
pera
tion
was
with
one
atm
osph
ere
with
air
as th
e w
orki
ng fl
uid
–Th
e co
mpe
ted
wel
l aga
inst
oth
er p
rime
mov
ers,
prim
arily
bec
ause
of h
igh
effic
ienc
y, q
uiet
ope
ratio
n, a
nd s
afet
y–
Effi
cien
cy w
as h
igh
bec
ause
Rob
ert
Stir
ling’
sor
igin
al p
aten
t inc
lude
d th
e ec
onom
izer
, kno
wn
toda
y as
a re
gene
rato
r•
Dev
elop
men
t was
eve
ntua
lly s
urpa
ssed
by
stea
m e
ngin
es, I
C e
ngin
es, a
nd th
e el
ectri
c m
otor
, •
The
first
gen
eral
pha
se o
f Stir
ling
deve
lopm
ent c
ame
to a
n en
d
4
Nat
iona
l Aer
onau
tics
and
Spac
e Ad
min
istra
tion
ww
w.n
asa.
gov
Dev
elop
men
t of S
tirlin
g•
Dev
elop
men
t was
pic
ked
up b
y P
hilip
s La
bora
torie
s,
Ein
hove
n, th
e N
ethe
rland
s st
artin
g in
the
1930
’s–
All
conf
igur
atio
ns a
t tha
t tim
e w
ere
kine
mat
ic–
They
wer
e in
itial
ly a
ir cy
cle
mac
hine
s, w
ith a
com
pres
sor
to in
crea
se m
ean
pres
sure
•A
s P
hilip
s tri
ed to
con
vert
the
heat
eng
ine
into
a
cool
er, t
he w
orki
ng fl
uid
was
cha
nged
to h
eliu
m a
nd
hydr
ogen
–G
reat
impr
ovem
ent i
n pe
rform
ance
resu
lted
–Lo
wer
flow
loss
es, h
ighe
r hea
t tra
nsfe
r coe
ffici
ent
–H
ighe
r effi
cien
cy•
Phi
lips
deve
lope
d an
impr
oved
und
erst
andi
ng o
f the
th
erm
odyn
amic
s–
Reg
ener
ator
rese
arch
–C
ycle
mod
elin
g•
App
licat
ions
wer
e th
ough
t to
be p
orta
ble
gene
rato
rs,
mar
ine
gene
rato
rs, l
ocom
otiv
e an
d au
tom
otiv
e ap
plic
atio
n
5
Nat
iona
l Aer
onau
tics
and
Spac
e Ad
min
istra
tion
ww
w.n
asa.
gov
Dev
elop
men
t of S
tirlin
g•
Dev
elop
men
t for
app
licat
ions
incl
uded
–G
PU
-3 fo
r milit
ary,
qui
et p
orta
ble
pow
er–
Ford
/Phi
lips
4-21
5 fo
r aut
omot
ive
appl
icat
ion
–U
nite
d St
irlin
g of
Sw
eden
P-4
0 le
adin
g to
war
d au
tom
otiv
e•
Kin
emat
icsy
stem
s re
quire
d m
any
auxi
liarie
s–
Oil
pum
p an
d fil
ter
–C
oola
nt p
ump,
radi
ator
and
fan
–C
ompr
esso
r and
hig
h-pr
essu
re ta
nk–
Slid
ing
seal
s–
Mea
n pr
essu
re c
ontro
l sys
tem
–Ki
nem
atic
linka
ge s
yste
m, s
uch
as th
e rh
ombi
c dr
ive
or
cros
shea
ds to
man
age
side
load
s•
For s
pace
pow
er, i
t was
gen
eral
ly v
iew
ed a
s to
o co
mpl
ex,
heav
y, a
nd in
here
ntly
life
-lim
ited
–S
tirlin
g Is
otop
e P
ower
Sys
tem
(SIP
S) w
as d
evel
oped
by
DO
E/G
ener
al E
lect
ric–
Bas
ed o
n rh
ombi
c dr
ive
with
two
rota
ry a
ltern
ator
s•
Adv
ance
d ve
rsio
ns o
f kin
emat
icS
tirlin
g ca
n be
vie
wed
as
the
seco
nd g
ener
al p
hase
of S
tirlin
g de
velo
pmen
t
6
Nat
iona
l Aer
onau
tics
and
Spac
e Ad
min
istra
tion
ww
w.n
asa.
gov
Dev
elop
men
t of S
tirlin
g•
The
third
pha
se o
f dev
elop
men
t beg
an w
ith th
e in
vent
ion
of th
e fre
e-pi
ston
Stir
ling
in th
e 19
60’s
•E
limin
ated
:–
Lubr
icat
ion
syst
em–
Gas
com
pres
sor a
nd g
as m
anag
emen
t sys
tem
–Li
fe li
miti
ng w
ear o
f slid
ing
seal
s•
Cou
ld b
e de
velo
ped
to h
ave:
–H
erm
etic
con
tain
men
t of w
orki
ng fl
uid
–N
on-c
onta
ctin
g op
erat
ion
–C
ontro
l thr
ough
the
load
of a
n ex
tern
al c
ontro
ller
–Lo
ng li
fe•
The
tech
nolo
gy m
atur
ed a
nd s
ucce
ss w
as:
–19
60’s
op
erat
ion
–19
70’s
reac
hing
des
ign
perfo
rman
ce fo
llow
ing
sign
ifica
nt d
evel
opm
ent
–19
80’s
desi
gn p
erfo
rman
ce fo
llow
ing
limite
d de
velo
pmen
t–
1990
’sde
sign
per
form
ance
follo
win
g m
inim
al
deve
lopm
ent
•S
till m
inim
al c
onsi
dera
tion
of s
yste
m in
tegr
atio
n
7
Nat
iona
l Aer
onau
tics
and
Spac
e Ad
min
istra
tion
ww
w.n
asa.
gov
Dev
elop
men
t of S
tirlin
g•
Free
-pis
ton
Stir
ling
conv
erto
r tec
hnol
ogy
for
radi
oiso
tope
app
licat
ions
was
bei
ng d
evel
oped
by
NA
SA
& D
OE
at l
ow le
vels
dur
ing
the
1990
’s•
1997
stu
dy le
d by
DO
E c
oncl
uded
that
Stir
ling
tech
nolo
gy e
xist
ed, a
nd w
as a
vaila
ble
for f
light
de
velo
pmen
t•
1999
Tec
hnol
ogy
Rea
dine
ss A
sses
smen
t was
co
mm
issi
oned
to d
eter
min
ed if
Stir
ling
was
su
ffici
ently
mat
ure
for t
rans
ition
to fl
ight
de
velo
pmen
t•
Team
mem
bers
DO
E, G
RC
, JP
L, L
M, O
SC
•R
eadi
ness
Ass
essm
ent c
onsi
dere
d –
Per
form
ance
map
ping
–E
MI/E
MC
cha
ract
eriz
atio
n–
Laun
ch lo
ad v
ibra
tion
test
–Fa
ult t
oler
ant g
ener
ator
con
figur
atio
n–
Flig
ht w
orth
y co
ntro
ller d
esig
n–
Rad
iatio
n to
lera
nce
–FM
EC
A
8
Nat
iona
l Aer
onau
tics
and
Spac
e Ad
min
istra
tion
ww
w.n
asa.
gov
Dev
elop
men
t of S
tirlin
g•
The
1999
stu
dy fo
und
that
:–
EM
I mea
sure
men
t sho
wed
that
a S
tirlin
g ge
nera
tor
coul
d m
eet t
he re
quire
men
ts o
f mos
t sci
ence
mis
sion
s,
but n
ot th
e m
ost d
eman
ding
–S
tirlin
g co
nver
tor T
DC
#1
surv
ived
12.
3 gr
ms
rand
om
vibr
atio
n te
st–
Gen
erat
or c
once
ptua
l des
igns
exi
sted
from
LM
, OS
C,
and
GR
C, w
ith v
ario
us d
egre
es o
f det
ail a
nd d
iffer
ent
conc
epts
for f
ault
tole
ranc
e–
A fl
ight
con
trolle
r con
cept
ual d
esig
n w
as d
evel
oped
, but
no
t bui
lt or
test
ed–
Ther
e ap
pear
ed to
be
no b
arrie
rs fo
r im
plem
entin
g a
suite
of o
rgan
ics
that
cou
ld s
urvi
ve th
e no
min
al ra
diat
ion
leve
ls–
The
FME
CA
sho
wed
no
show
-sto
pper
s•
1999
Tec
hnol
ogy
Rea
dine
ss A
sses
smen
t det
erm
ined
th
at S
tirlin
g w
as s
uffic
ient
ly m
atur
e fo
r tra
nsiti
on to
fli
ght d
evel
opm
ent
9
Nat
iona
l Aer
onau
tics
and
Spac
e Ad
min
istra
tion
ww
w.n
asa.
gov
Dev
elop
men
t of S
tirlin
g
•LM
was
sel
ecte
d by
DO
E a
s th
e S
yste
m In
tegr
atio
n C
ontra
ctor
for t
he S
RG
110
gene
rato
r•
Flig
ht d
evel
opm
ent c
ontin
ued
at L
M, I
nfin
ia, a
nd G
RC
w
orki
ng in
par
tner
ship
thro
ugh
2005
•G
RC
als
o co
nduc
ted
an a
dvan
ced
tech
nolo
gy e
ffort
to
incr
ease
effi
cien
cy, r
educ
e m
ass,
enh
ance
robu
stne
ss•
Hig
hlig
hts
incl
ude:
–M
etal
lics
•O
ptim
ized
hea
ter h
ead
mat
eria
ls fo
r lon
g lif
e, c
hara
cter
ized
the
mat
eria
ls•
Dev
elop
ed te
chni
ques
to re
pres
ent t
he m
ater
ials
on
a pr
obab
ilistic
bas
is, c
ondu
ct li
fe a
naly
sis
in p
roba
bilis
tic te
rms
•V
alid
ate
heat
er h
ead
life
anal
ysis
thro
ugh
benc
hmar
k te
sts
•O
ptim
ize
rege
nera
tor p
roce
ssin
g to
enh
ance
relia
bilit
y
10
Nat
iona
l Aer
onau
tics
and
Spac
e Ad
min
istra
tion
ww
w.n
asa.
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Dev
elop
men
t of S
tirlin
g–
Org
anic
s•
Cha
ract
eriz
e cu
re k
inet
ics
of c
ritic
al a
dhes
ives
and
opt
imiz
e pr
oces
sing
•C
ondu
ct a
ging
test
s of
the
orga
nics
•In
itial
ass
essm
ent o
f rad
iatio
n to
lera
nce
–M
agne
ts a
nd li
near
alte
rnat
ors
•C
hara
cter
ize
cand
idat
e m
agne
ts•
Dev
elop
sho
rt te
rm a
nd lo
ng te
rm m
agne
t agi
ng te
sts
•D
evel
op te
chni
que
to c
hara
cter
ize
curv
ed m
agne
ts•
Cre
ate
tech
niqu
e fo
r 3-D
line
ar a
ltern
ator
mag
neto
stat
ican
alys
is
•P
redi
ct c
ondi
tions
for d
emag
netiz
atio
n in
a li
near
alte
rnat
or a
nd
valid
ate
with
test
dat
a–
Stru
ctur
al d
ynam
ics
•D
emon
stra
te fu
ll op
erat
ion
of c
onve
rtor u
p to
12.
3 gr
ms,
0.2
g2 /
Hz
•Fu
lly c
hara
cter
ize
mod
al re
spon
se o
f the
Stir
ling
conv
erto
r•
Dev
elop
con
cept
for s
truct
ural
inte
grat
ion
of S
tirlin
g co
nver
tors
into
th
e ge
nera
tor t
o re
duce
laun
ch lo
ads
•D
evel
op s
pace
craf
t ada
pter
that
cou
ld b
e us
ed to
redu
ce la
unch
lo
ads
if ne
eded
•V
alid
ate
stru
ctur
al m
odel
thro
ugh
gene
rato
r sim
ulat
or te
st•
Sho
w a
naly
tical
ly th
at S
RG
-like
gen
erat
or c
ould
sur
vive
up
to 1
5.1
grm
s, 0
.3g2 /H
z
11
Nat
iona
l Aer
onau
tics
and
Spac
e Ad
min
istra
tion
ww
w.n
asa.
gov
Dev
elop
men
t of S
tirlin
g–
EM
I/EM
C•
Tota
l of t
hree
test
s co
nduc
ted
at G
RC
and
JP
L•
It re
mai
ns th
e fin
ding
that
Stir
ling
coul
d m
eet
gene
ral s
cien
ce re
quire
men
ts, b
ut w
ould
nee
d a
mis
sion
kit
for t
he m
ore
dem
andi
ng m
issi
ons
•E
MI r
emai
ns a
sys
tem
leve
l iss
ue, r
equi
ring
com
plet
e ge
nera
tor d
esig
n–
Rel
iabi
lity
•Te
chni
ques
for p
roba
bilis
tic a
naly
sis
have
bee
n ap
plie
d to
all
criti
cal c
ompo
nent
s–
Nee
d to
com
bine
indi
vidu
al a
naly
ses
into
a s
ingl
e S
tirlin
g co
nver
tor a
naly
sis
•D
iffic
ulty
rem
ains
in v
erify
ing
life
and
relia
bilit
y of
a
devi
ce w
ith n
o w
ear m
echa
nism
–Sa
me
prob
lem
face
d by
the
cryo
cool
er in
dust
ry•
Expe
rienc
e fro
m lo
ng li
fe S
tirlin
g co
nver
tors
and
cr
yoco
oler
s is
dire
ctly
app
licab
le•
Muc
h m
ore
oper
atio
nal d
ata
is n
ow a
vaila
ble
–O
ver 8
0,00
0 ho
urs
at G
RC
12
Nat
iona
l Aer
onau
tics
and
Spac
e Ad
min
istra
tion
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w.n
asa.
gov
Dev
elop
men
t of S
tirlin
g–
Con
trolle
r dev
elop
men
t•
Flig
ht c
ontro
ller h
as b
een
parti
ally
des
igne
d•
Har
dwar
e ha
s no
t bee
n te
sted
, con
verto
rs
rem
ain
on te
st w
ith re
sear
ch c
ontro
llers
•N
ew d
irect
ion
is b
eing
pur
sued
in A
ctiv
e P
ower
Fa
ctor
Cor
rect
ion
cont
rolle
rs•
Con
trolle
r rem
ains
unp
rove
n–
Stir
ling
cryo
cool
ers
have
bee
n pl
aced
in fl
ight
•D
ata
is b
eing
acc
umul
ated
on
life
and
relia
bilit
y•
Less
ons
lear
ned
are
bein
g ap
plie
s w
here
ap
prop
riate
•C
riter
ion
for v
alid
atio
n of
life
and
relia
bilit
y ar
e be
ing
stud
ied
for p
ossi
ble
use
in p
ower
co
nver
sion
•Te
rrest
rial d
esig
ns h
ave
been
dep
loye
d,
accu
mul
ated
ove
r 44
milli
on h
ours
, dat
a is
sh
owin
g M
TBF
of o
ver 5
00,0
00 h
ours
–S
yste
m in
tegr
atio
n ha
s ad
vanc
ed to
a m
uch
high
er le
vel o
f det
ail
13
Nat
iona
l Aer
onau
tics
and
Spac
e Ad
min
istra
tion
ww
w.n
asa.
gov
Dev
elop
men
t of S
tirlin
g•
Adv
ance
d te
chno
logy
–Th
is e
ffort
has
resu
lted
in a
6-fo
ld in
crea
se in
spe
cific
po
wer
of t
he S
tirlin
g co
nver
tor
–Tw
o fo
reru
nner
s of
the
Adv
ance
d te
chno
logy
co
nver
tor w
ere
able
to o
pera
te s
ucce
ssfu
lly a
t vi
brat
ion
leve
ls u
p to
24
grm
s, 0
.8 g
2 /Hz
–Th
e ad
vanc
ed te
chno
logy
cou
ld in
crea
se g
ener
ator
sp
ecifi
c po
wer
from
~4
W/k
g to
~8
W/k
g–
AP
FC c
ontro
llers
cou
ld re
duce
con
trolle
r mas
s an
d vo
lum
e•
Hav
e be
en s
ucce
ssfu
lly u
sed
in la
bora
tory
, nee
d to
be
mad
e fu
lly a
uton
omou
s, fl
ight
wor
thy
–M
odel
ing
now
has
tool
s to
redu
ce ti
me
and
risk
of
deve
lopm
ent
•C
FD to
inve
stig
ate
deta
ils o
f ope
ratio
n, a
ppea
rs v
alid
•SD
M to
inve
stig
ate
com
plet
e sy
stem
dyn
amic
in
tera
ctio
n, in
clud
ing
ther
mal
con
ditio
n, c
ontro
ller a
nd
end
user
load
14
Nat
iona
l Aer
onau
tics
and
Spac
e Ad
min
istra
tion
ww
w.n
asa.
gov
Con
clus
ion
•Th
e st
atus
of S
tirlin
g de
velo
pmen
t has
cha
nged
fund
amen
tally
si
nce
1999
with
dat
a at
han
d–
Ove
r 80,
000
hour
s of
ope
ratio
n of
pro
toty
pica
l har
dwar
e–
QA
sys
tem
und
erst
ood
incl
udin
g le
sson
s le
arne
d fro
m lo
ng li
fe
cyro
cool
erin
dust
ry–
Mat
eria
ls w
ell c
hara
cter
ized
for l
ong
life
and
high
relia
bilit
y (m
etal
lics
and
orga
nics
)–
Stru
ctur
al d
ynam
ics
test
s sh
ow s
ucce
ssfu
l ope
ratio
n at
hig
h le
vels
of
vibr
atio
n–
Crit
ical
com
pone
nt a
ging
has
bee
n m
odel
ed a
nd is
bei
ng v
alid
ated
–S
ucce
ss o
f Stir
ling
fligh
t cry
ocoo
lers
(and
long
-life
terr
estri
al u
nits
) pr
ovid
es s
uppo
rting
dat
a in
pow
er c
onve
rtor t
rans
ition
to fl
ight
–G
ener
ator
inte
grat
ion
succ
essf
ul fo
r lau
nch
load
s
•S
ome
area
s re
mai
n to
be
com
plet
ed, s
yste
m in
tegr
atio
n, fl
ight
co
ntro
ller,
exte
nded
ope
ratio
n of
inte
grat
ed g
ener
ator
, etc
•Th
ird g
ener
al p
hase
will
be
conc
lude
d w
ith s
ucce
ssfu
l sys
tem
in
tegr
atio
n of
free
-pis
ton
Stir
ling
into
a s
yste
m