Note: Descriptions are shown in the official language in which they were submitted.
- `
SPE(: IFIC~rr ON
Turbs)-jet~ turbo-fan jet, bypass jet and turboshaft engines are used
to power aircraft~ and turboshaft engines and are used in vehicular and
stationary applications. These types ~f engines are generically referred
to as gas turbine engines~ and include a compressor, a combust~r and
turbine sections. ~n order to prevent air leakage from rotating sur~aces
of the engine to the oil sump, some type of air seal is employed, usually
a lip type and/or labyrinth seal. The seal is externall5~ pressurized by
turbine bleed air and since all seals leak some air~ the oil sump must be
vented to limit the pressure rise. The airS which causes foaming and
frothing when intermixed with oil through the gearing~ is vented to the -
atmosphere, with oil vapor and aeros~ls ~ entrained Dil droplets.
Such oil droplets may be deposited on the ground, and if they
are, can pose a serious problem in the vicinity of airfields~ where there
is heavy tr~fic, and also along highways traversed by vehicles equipped
with gas turbine engines, or in the vicinit~ ~f stationary gas turbine
equipment. The resulting oil deposits gather dust and other particles
of material from the air, and besides being difficult to remove~such
deposits may pose safety and ecological hazards if they accumulate in
the atmosphere or on airport runways, highway surfaces, and interior
and exterior building surfaces. With the increased use of gas turbine
engines, and the present emphasis on avoiding pollution OI the atmosphere,
it ha~ become imperative to design a system which is capable of efEi-
ciently and more or less completely removing such entrained oil, whether `
entrained as an aerosol, or as larger oil droplets, while imposing a low
~ystem bacl~ pressure ~
38'~
The amount of oil lost in this manner has a substantial economic
impact on cost of operating the turbine; furthermore7 frequent monitoring
cf oil levels and frequent refilling oE oil sumps is very undesirable.
Normal practice is to vent ~he sump to the engine exhaust; this
contributes significantly to pollution of the atmosphere.
Al~hough it is known that the exhaust gases frorn gas turbine
engines are responsible for carrying oil to the atmosphere, it has been
;
impractical heretofore to strip the oil before it leaves the engine? because
relative to the volume and velocit~r o~ flow, the amount OI oil is very
small. For example~ conventional methods ~f spraying the vapors with
water or of cond0nsing the oil and derivative vapors in the exhaust gases, ;~
and then dernisting the aerosols; are impractical, because they cannot
cope with ~he volumes and flows of ga~es in~ol~ed, in order to remove
~he very small amounts of oil present. ~ ;
Gas turbine lubricating oils vary considerably with respect to
oil operating temperatures, and various lubricants are used. When the
, . .
oil temperatures are comparatively low and where low Yapor pressure
lubricants are used, the amount of vapor entrained in the air effluent '!'.
";' ,~ ',
from the sump is negligibly small. In turbines in which the tempera- - -
ture~ are high, or in which high vapor pressure oils are used, oil carry-
:
over in vapor form can be ~ignificant. In such installations, a heat e~-
changer in which the cooling agent can be ambient air, can be used to
, . . . ..
reduce the ~ffluent air temperature such that nearly all the oil vapor
condenses to a mist or smoke, consisting of fine droplets, usually in
the range 0 lto 1 micron in diameter and predominantly 0.2 to 0.5
mlcron in diameter. Such a mist is very difficult to condense, and - -
3~
would for example, pass freely ~Irough any type of centrifugal or impact
separator ~
In accordance with the invention, a demister assembly is provided
which is capable of removing, and optionally also of reclaiming, liquid~
entrained in gases, and especially of removing substantially all of the oil
entrained a~ droplets in gases such as air with a low back pressure res- ;
hiction, usually substantially less than one-half p~und per squar~
inc~ .
The demister assembly of the invention is placed not in the ex- ;~
;10 hau~t gas line of the engine but in the oil sump ve~t line from the lubri-
cant supply reservoir. The demisted oil is reclaimed by providing a
return drain line to the oil sump, thus providing a significant saving in
oil consumption.
The demister assembly comprises afirst stage coalescer7 in -~ ~
which the entrained liquid droplets are coalesced ~to droplets sufficiently ~ :
large to be affected by gravity, and in which a proportion of the thus con-
densed oil drops to the bottom of the coalescer, and a second stage
coalescer, in which most of the remaining portion of thé partially
condensed droplets are further coalesced and draLn to the bottom of the
coalesced element.
The liquid collected at the demister is drained off, and in the case
of lubricating oil may for example be returnecl to the oil sump. The gas
from the demister although freed from oil droplets may contain oil vapor,
and can be recycled to the cornpressor inlet of the engine, so ~at the
oil vapor can also be consumed, ~efore the gas is vented to the atmos-
phere as exhaust~
~3i~7~
The demister of th~ invention is thus particularly applicable to
a gas turbine engine, where it can be placed in the gas vent line from
the oil sump. All gas learing the sllmp consequently is compelled to ~;
pass through the demister o the invention. This ensures that oil dr~p-
lets entrained in such gas are remo~ed. The gas thus stripped of liquid
oil but which may contain oil vapor is recycled to the compressor and the
com~ustor. The result is that all gas flow which may possibly contain
liquid oil droplets is passed through the demister, and oil vapor remain-
ing therein is burned, so that oil-~ree exhaust gas passing from the com- :
pressor, burner, and turbirle, is vented. Thus, su~stantially no gases
capable of depositing oil can enter the atmosphereO ~ ` -As an optional adjunct, t~e demister assembly of the invention
can include additional elements to increase the sound-attenuating qualities.
To obta-in the silencer flmction in addition to the demister function, addi~
tional coalescing and stripper layers are added, which are capable also
of sound attenuation, in addition to their coalescing and/or stripping
funcl:ion. When the gas is caused to pass through such sound absorption `~
or sound attenuating mate~ial, the noise level is also reduced.
- The coalescer in accordance with the invention is a nonwo~en
fibrous mat of relatively low dénsity, and a relatively high porosity;
porosity being defined as the percentage of voids. In this respect, ~e
coalescer of the invention differs from coalescers used in liquid-to-
liquidcoalesc~nce. AsnotedinU.S. patentNo. ~,26~,442, issued
August 23, 1966 to Pall, Krakauer, Seibert, Verrando and Keedwell,
liquids suspended in liquids in which they are wholly or partially
immiscible are removed by coalescing the droplets by ~orcing them
through a small passage whose diameter is substantially less than the
diarrleter of the suspendecl dropletsO The passage can be of any con- -
~Q38~78
figuration, for example, a single s~raight-through conduit, or a tortuous
many-forked passage formed by the interconnected interstices in a m~ss
o fibres. The configuration and length of the passage are not important,
but the diameter relative to the diarreter of the droplets is critical.
PreEerably, the passage is less than 2/3 down to about 1/10 the diameter
o the smallest droplets susp0nded in ~e fluid being treated, and in any
event less than 4/5 ~he average diameter of ~e suspended droplets. The
passage can have a greater diameter over part of its length provided it
at some point has such a minimum diameter . Preferably, the minimum
diameter of the passage is at the entrance thereto, or adjacent the en-
trance. Such a coalescer when in the form of a nonwoven mat has a high
density and a relatively low porosity.
In contrast~ when coalescing lic~id droplets enh~ained in a gas,
the diameter of the passages can be considerably greater than ~he cliameter ~ ~ -
1~ of ~he droplets. The coalescence appears to result llot from droplets
squeezing through the passage but from the large surface area of the
fibers, and the multiple changes in direction which the gas must make
in flowing through the mat. The gas dashes the larger diameter droplets
against the fibers by inertia, and they subsequently cling to the fibers.
2~ The smaller diameter particles randomly move by Brownian motion and
over a large surface area have a statistically greater opportunity to con-
tact a surface and cling to it; in addition, they collide with each other and
coalesce to form larger droplets which are remoYed by inertia. Thus, the
diameter of the passage is much less important than the surface of the fibers
and a low density nonwoven mat of high porosity, ~i. e. high percentage of
voids, or high voids volume) and high surface area may indeed offer more
. .' ',
3~37~8
oppor~nîtie~ ~or eollision and coale~cence of oil droplets than a low
p~ro~ity st:ructur~ with ~mall0r opening~, but wlth les~ surface axea.
A.ny fibrous material inert to oil c~rl be used ir. the rlorlwolren
fibrous mat. Suit~ble fibrous mat0rials include glass, ~artz, ceramic, ~ ~ :
titanium. dioxide, alumlllaJ pol~vinyl chlo~ide, polyelthylene, polypro-
wlene, pol~acr~lonitrile, polye~ter, polyvlIIylideIle chl3rideJ regener~
ated cel~ulose7 asbesto~, cellulose acetate, resin-impr~gna~ed cot~on,
and pol~te~ailuoroe~ylene. - :;
The fiber~ are ~iciently long ~o ~at ~ey are capable o~ ~orm~
~g a coherent n~woYen mAt. Neither ~eir leng~ nor ff~e diameter i~ - -
critical, but for ef~icient coale~cing action it i~ importan~ tha~ ~e non- :
woven mat ~fer a high sur~ace area and den~ity and for thi~ purpo~e ~ ~ ~
fine fiber~ are better than coa;rse fibers. Ordinarily, the fiber diameters - -
are within the range Erom about 0. 25 ~ about 30 microns. .
~e den3it;~ onwoYen ma~ i~ cc3n~;rolied by co~ining.~e mat
between rigid facing sheets. Tl~e ~igidity OI ~e sheet~ musi; be adeq~a~
to retai~ the Ilonwoven mat u~lder ~e di:Ei eI~ent~al ga8 pres~ures that may
be encountel ed acro~ the layer wi~hout apprecL~ble distortion o~ ruptwFe . .
I~e density o~ ~e la~er should in general be ~thin ~e range from ab~ut
.
0. 05 to about 0. 5 g/cc~ and ~referabl~ from about 0 . 2 to about 0. 4 g/cc . -~
As the ~acing ~h~ets, :sintered metal particle sheet~; woven plastlc ~r metal
wire me~h, rolled and compressed and al~o sinter-bonded, if desired; .
perforate metal and pla~tic sh0ets; and resin-impregnated foraminolls ;~
Iibrous sheet~ can be u~ed,
~ince the fibrous coalescer l~yer is con:fined between iacing
sheets, it is not necessary ~at the fibers of the l~yer be bo~ded together.
,
~.~338 tt78
In fact, in a long fibered mediun~, if no binder is present, the porosity
of the layer may be greater7 and consequently, the pressure drop across
the layer is less. It is clesirable in order to maintain a high efficiency
of separation of ~e entrained oil droplets to hold ~e pressure drop across
the coalescer layer to as low a value as possible.
However, if short fibers are used impro~Ted iber r etention and
reduced compressibility can be obtained by bonding the fibers wîth a
synthetic resin. Phenol-formaldehyde resins, urea-ormaldehyde resins,
melamine- tormaldehyde resins, epoxy resins and o~hers are quite satis-
factory bonding agents. Ihe bonding technique is conventional, and need
notbe further described, except, of course~ to note that the amount of
- resin is less than will reduce unduly the porosity of ~e mat. Just enough ~ ~ ;
~ ,
- resin should be used to coat the fibers and ensure bonding at ~eir points
of contact. The amount lS readily ascertained by simple calculation of
the surface area of single fibers of any given diameter and length. From
3~c ~o 50C/c res~n by weight is usually adeq!late for 0.1 to 2 micron dia-
meter fiber s .
A preferred method o m~ing mats of the type which can be em-
ployed as coalescers in ~he invention is to lay down a slurry of the fibers
suspended in water of controlled pEI on a cloth supported on the mesh of
a Fourdrinier or paper ,making machine. A vacuum can be applied to
condense the fibers to a mat on a cloth backing, which is then removed
from the mesh screen support. The fibers can be similarly deposited
from a suspen~ion in air.
The stri~per is of a porous sheet material which is coarser than
the primary cvalescer, but which is of a pore size such that the coalas-
ced oil droplets are incapable of passing through the pores or interstices
thereof, while the gas passes through freely. As the stripper, sheet a
~3~37
porous open-cell polyurethane f~am can be used, having a porosity
within the range frorrl about 50 to ahout 150 pores per square inch~ and
having an average pore diameter within the range from about 0.005 to
a~out 0.02 inch, and a voids volume preferably in excess of 80O~C. Any
other material, for example a coarse glass fiber mat, or a mat of
synthetic or natural organic fibers~ may be used as a stripper, pro~ided . ~ :
its pore size and voids volume is in a similar range.
M3st of the oil mist incident on the primary coalescer is con- .:
densed to larger droplets, which flow by gravity to ~he bottom of the
coalescer, and thence into the sump; however, a small proportion,
usually between about 2 and about 15~/c~ is instead entrained in the air
lea~ing the coalescer, in the form of relatively large (eg. 0.2 inch
diameter or. larger) droplets.. These ~ollect on the stripper. lf ~e ~ : -
stripper is placed at an angle to ~he horizontal, the coslesced oil runs
~ 15 down the stripper by graYity, to collect at the base, drains off" and .
; ~ returns to the oil reservoir or sump.
The polyurethane foam can be mlade of cmy polyurethane resin
which is not deteriorated b~ contact with the oil. Any polymer o~ a diiso-
cyanate and a glycol can be used, includmg aliphatic diisocyanates and
. 20 aliphatic glycols, aromatic diisocyanates and aliphatic glycols, aliphatic
dlisocyanates and aromatic glycols, aromatic diisocyanates and aromatic - ;
glycols, cycloaliphatic diisocyanates and aliphatic glycols, aliphatic
diisocyanates and cycloaliphatic glycols, and any mixtures thereof, in
any desired proportions.
~5 It is ~requently convenient to arrange the coalescer and stripper
elements concent~ically, each being in the form of a cylinder or other
~3~77~
closed configuration, one within the other. To provide for a greater
sur~ace area wi~hin a confined Space7 ~he coalescer element can be
foldecl in an undulating or corrugated configuration. The coalescer can
b~ the outer of two elements~ in such a concentric arrangement, 10w
being from outside in, with the gas and oil being collected at the center,
and the oil being collected from the surface stripper element, draining ~; -
by gravity down and the air discharge up. However~ it is usually pre-
erable to use the reverse arrangement, wi~ flow from inside to out,
as the velocity of the air leaving the stripper is lower, leading to a lower
tendency toentrairi droplets from the stripper. Jf the demister assemblyist ~ ~ ~
include increased silencer capability, in order to obtain greater surface ~ --
area and ~olume in the silencer assembly, Eor greater sound attenuation,
it may be desirable to arrange the coalescer and stripper elements so
tha;t the coalescer element is the innermost and the stripper ~lement
the outermost. ~ this event, flow is rom inside out, ~rough the
demister assemblyO -
A concentric arrangement is not essential, however, al~ough
it is convenient for many uses. The coalescer and stripper elements
can also be arranged as flat or corrugated sheets, with flow proceeding
from one side to the other of the composite, which is arranged in-lineO
Increased sound attenuatioll is obtained by including additional
layers of the coalescer and s~ipper components in the demister assemblyO
These layer~ can be inkerposed before or after the coalescer unit, before
or after the stripper unit, or coincident with the coalescer and ~tripper
material, providing an increment of sound attenuation with each stage
of additional coalescer and stripper material~ It will be appreciated, of
~i,'~
~3~77~
COUr9R, that the mate:rial~ composing thQ coalesc~r and the
~tripp~r are capahle of incremental ~olmd ab~orption or sound
attenuation. ~ many ca~e,~, they ar~" however, ~ot capable o~
providing suficl~nlt 90U~ld ~te~ ~ion~ and additional la~r~r~ are
n~cessary for the functio~, eve~ though th~y may llot be r~quir~d
for the coal~sci~g or ~tri~ping ~nction. The coale~cing element
additions increase the ~ epara~g efiicienc~. Whil~ it,may be
difficult in the complete cornbination to a~,~ign e2~clu~ilvel~ a ~,ound ~ .
ab~orb~g or coale~cing and ~ound ab,~orbing or ~ftripping func~on :.
to a~y gi~en layer, where it i9 capable of ser~r~gboth funcl:ic,ns,~ it
may be as~umed that a given 1~7er is pre~ent primarily ~or ~und . - -~
ab~rption or attenuation purposes wher~ it is not required for
coalescence or strippi~g~ the de~vice fwlclti~ning in this respect
.j , . . , - ~ ~
:1~ even ill the absellce of such a L~yer~ ~ :
!,' 15 : A~ the sound absor~ing or attenuatin~ materia1, $here ~ ;-
can be u5ed, paper porous foam materia'l such a~ polyuretha~e foam~,
or nonwoven fibrolls mats, such as gla9~ fiber ~. As many l~yers
- as m~y be required ca~ b~ added for this purpose. If the layers are
of ~u~icien~ poro~ity, so that pr~ drop i~ kept to a minim~m,
20 th~re i~ no upper limit upon the number of such la~ers which can be
present.
The den~ f the ~ound attenuatirlg or sound absorblng
laye~ not crltical, but .ln general the greater the density, the
better ths so~md attenuation, zu1d the higher the coale~cing efficiency,
a~ pre~umably because a larger surface area of material may then be
contirled within a given volllme, solmd attenuation belng primarily a
' .
,
'' 10
7~
func~iorl d su:rface area, along ~th coalesc3n~ efficiency~ although
volume i3 al~o ~ significaIIce~
While por~si~y is not critical" it will be apprec~ated
that the porQsill~ f a solmd attenuatillg or absorbing layer down~
~tream o~ the stripper element call lbe greater than tba~; o~ a B~milar
la~er upstream of the coalescer~ becaus~ the ai3;~ down~tream o~ the
~tripper i~ free from oil. .
The den~i~ o~ the coalescel sound attenuatiDg la~ers
call be within the raIIge from about 0.1 to ab~ut 0. 5 g/cc. and the
fiber diame~er shoul~ be within the rang~ from ab~ut 1 to ab~u~
10 microns, ~ the p~ro~ity ~ the stripper ~olLnd attenu~ g layers
i
can be within the range from about ~ to about 150 poreg per square .
inch, with the~e layers having an average~ density within t~e range
from~ about 1 to about 3 lbs~ /cu. ft.
- PrefeITed embodiment~ of the invent~on axe æh~
. ~nthedrawin~, ~nwhich:
~E~i~ a 1~7ngltudinal section through a!demister
a~embly iIL accordance with the inventi~n, designed for use ~ h a
ga~ turbine e2lglne.
. ~is a cro~s-sectioqlal view taken alon~ the
line 2-2 ~vilth partial interior section o~ the demister assembly of .- ~ :Fi~ure 1.
Fl~re 3 is a diag:ramatic view of a gas turbine
engirle sy~tem in which a clemi~ter a~embly of the in~vention i9
~5 interposed in the air vellt line from the oil ~ump, for removal of oil
entrained in ~uch air.
.
~i~33~
The demister and silencer asse~bly sho~m in
Figures 1 and 2 is in cylindrical form, witllin a housing 15, with the
coalescer C~ and stripper ST comp~nents bein~ arranged concentrically
within a housing 15, the several concentric cylinders thereof con
fined between and bonded to end caps 1, 2. The layers are supported
upon an inner perforated convoluted metal core 3, such as aluminum
mesh sheet formed in a cylinder and having a plurality of relatively
large apertures 4. The end cap 1 is blind~ but the end cap 2 has a
central aperture 5, serving as an inlet for oil~laden air into the
central space 6 of the assembly, within the metal core 3. - ~ .
The coalescer C is innermost~ supported upon the
core 3, and c~nfined under compression between the core 3 and outer
sheath 7. Both core 3 and sheath 7 are 18 x 14 square wea~e wire
m~esh screens made of aluminum wire~ and having pore openings
0~ 009 inch in diameter~ formed in a corrugated or undulating con~
,
figuration. The coalescer material is a n~r~w~ven fibrous mat 9
of glass fibers 10 approximately 0. 00()11 inch in diameter. The
m~t 9 is approximately 1/8 inch thick, in a single wrap between
screens 3, 7, and has a density of approximately 1. 5 lbs/cubic foot.
The stripper ST comprises two wraps of 1/8 lnch
thick layers of foamed p~lyurethane sheet 11, 12 having a porosity
of 100 pores per square inch, and a voids volume in excess of 90%.
Since each layer is approxîmately 1/8 inch thick, the total stripper
con~e~uently is 1/4 inch thick. The polyurethane foam is in close
juxtaposition to the outer sheath 7 of the coalescer C in order to
obtain as compact an assembly as possible.
12
77~
The ~sambly is prot~cted by an out~r sleeve oî
perLforated metal 22, ~d a sleeve of open polypropyle~e ex~uded :
me~h 30 is interpo3ed to permit fre~ flow of air i~rom the outer
surface of the ur~thane foam to the hole~ ~f the p~rforated ~l~ave.
Each OI the concentric cylindrical layer~ is bonded
to the end cap~ 1, 2 at each ~nd by the pottng compou~d 24 ill a leak- -
tight seal, thu~ en~uring ~hat all flow entering t}le center 6 of the
assembly through the inlet 5 c~f end cap 2 mu~t pa~39 t~l~r)ugh th~
several L~yer~, in order to emerge through th~ ~utermosl: layer 22.
In operation, oil-laden air ent~ra the assembly through ``
the inlet 5 o~ bnd cap 2. It then proceeds through the core screen 3,
thuæ entering the coale~cer C, ar~d passeg3 through ma~ 9. I~ the
course of pas~ing through the coalescer m~t 9~ the entrailled o~
droplets are coale~ced to form larger droplets~ which grow in ~ize ~ : -
until the balls of the influe~t oil ~ettle to the b~ttom of the el~me~t ~-~
by gravit:y. A small proportion o~ the oi]. Is e~ltrained a~ rdatively
eoarse drop~.. Becau~e of their rela~i~ely harge sizet the~e dropleb
al~e collst:ted wlthin the po~yurethane foam3, coalescing into ~till
.. . . . . .
larger drop~, which flow dow~. by gr~ r to the bottom ~the~el~ment~ and
thence Plow over the lip 21 and through th~ porta 23 ~n the end cap 2 in- . -
- to the oil sump 25~ at the base o~ the hou~ing.
The hou~ing 15 is pro~rided with an oil outlet 26 which
leads to the oil line 27t so that the oil collecting in the annular space 8
an~ oil ~ump 25 can be ~tb~rawn through the outlet 26 via the oil line 27.
The air passe~ through the polyurethane foam layers
11, 12, now ~ub~tanti7,11y f.ree from oil droplets, but containing oil
in vapor form. Thi~ air then e~cape~ through the outer slee~res 21
~: 13
-
77~
and 30, ancl then through outlet 2~ of the housing, whence it may be
conducted via the air line 29 to the engine intake, so that the oil
vapor can be burned. For example, in a gas turbine engine (n~
shown) the air can be fed to the compressor, and then to the burner.
It will he appreciated that khe end caps 1, 2 can be
provided with any xequired fittings, so that they can be inserted in
the air line leading from the oil sump of an engine. Such line
connecti~ns are kno~m, and form no part of khe instant invention.
In addi-ltion to use in this manner, the demister
assembly of the inventi~ can also be used to remove oil mist from
air exhausted from air cylinders. Eghau~t air from air cylinders
normally carries of f a mist of lubricating oil, as well a~ a con-
siderable amount of noise. The oil mist can be removed~ and the
noise level reduced by 30 dbA or more, using the demister of
the inver~tion.
It will of course be appreciated that a demister
assembly with additional silencer components can ea~ily be obtained
by conversion of the device shown in Figures 1 and 2. ~11 that need
, - .
be done is introduce additional sound attenuating layers, such a ~;
20 nylon paper layers, another glass fiber mat, a paper layer,
additi~nal layers of polyurethane sheet7 and a fabric layer.
The deviee is al~ useful with mist type lubricating
systems7 in which finely divided air~borne oil is carried to the
bearings for lubrication. The effluent air from this lubricating
a~ system can be cleansed of oil mist, prior to being vented to the
atmosphere, without danger of pollution. The collected oil can be
returned to the mist generator for reuse.
, .
1~
3~77~ ~ :
The demister device can be built using materiaLs
n~ su~ceptible to attask by corro~ive fluid~, and can t~en al~ be used
to remove corrosî~e acid droplet~ entrai~ed in air, ~uch as the
hydrogen chlor~e mi~t~ o~ained in chlorine manu~acture, ths sulfuric
acid mist~ encauntered in ~uliuric acid ma~ufacture~ and th~ 3ike. ~;
The demi~ter i~ particula*ly use~ul in gas turbin~
eng;i~e3, where ît~ low operating di~er~nt3al pres~ure permit~ it .
to be placed in clo~e proximil~ to tha englne. ~ ~ ~
Th0 gas turbine engine ~hown diagramaticall~ în . ~ :
.
Fi~re 3 employ~ a demisteP a~sembly il:l accordallce with the i~-
verl~ion in the air line lead~g Irom the oll sump. The source o~
tgli~ air i8 engîn~ bleed air which leaks t~ough the oil ~eals, alld
wh~ch picks up oil mi~t and vapor as it passes ~hrough the sump. .
By Interpo~ng the demi~ter o~ thi~ invention hl the alr line from the
1~ oil ~ump, the oil mist can be removed ~om the air. .
The ~emi~ter remo~e~ 90 to ~9. 9~ of the oil pre~
sent in liq~id form, and the rema~nder, 1:ogether with any oil pre^
~ent a~ vapor9 ca~ be delivered to the engine inta~e, wher~ the -
remaining oil ~ burned. It may alte~at~:ve~y be vented to the
20 atmo~phere . I~ the latter alternat~re l~ elected, it may be.de~irable-
to cool the air prior to reachulg th~ demi3ter, to reduce lts content
o~ o~l vapor7 ~P hot air containing oil vapor is deliYered to
atmo~phere, the vapor conden~es to a den~e smol~e on cooling.
/
The gas turbine engine 30 ~hown ha~ an air inlet 31
pr~vided with an ~ray 32 of vortex separators 33 ~erving a~ an inlet
, . . .
~5
~ t3~77~3 :
air cleaners. The air then passes through the compressor 3D~ tv the
burners 35 arLlexpands througll the turbine 36, whence the exhaust
gases pass to the e~haust gas ~utlet 37.
The engine inclu~es an oil sump 38 serving as the
5 source of lubricant such as lllbricating oil which is fed under pressure
to the moving parts of the engine, including the compressor bearings
(not shown). Provision must be made to vent the air which leaks
through the main bearing seals, and this is accomplished by the ~ir
vent line 39 leading from the sump. In this air vent line is interposed,
10 in series, a demister 41 in accordance with the in~ention, which re- ~-
m~es the liquid oil frorn this air, although not the oil vapor. The
liquid oil thus removed is collected~ and returned vi~ line 42 to
the oil sump 38.
Xt is necessary that the vertical elevation of the -
15 base of the demister relative to that oE the surface of t~e fluid in the ~ ~
sump be such that a bead of oil of this height exceeds the differen:~ial : ~ -
pressure developed across the demister. If, for example, the
differential pressure across the demister under the worst condi~ions
of operation (saturated with oil) is 0. 5 psi, a~d the density of the oil
20 is 0. 85 g/ml, then the minimum elevation must be 16 inches. In
many installations, it is inconvenient, expenslve, or impossible to
pro~ide higher elevations than 16 to 24 inches, ~hence the importance
of low pressure drop through the demisters.
The line 43 carries the air containing oil vapor from
25 the demister 41 to the cvmpressor 34 of the engine, whence it is fed
to the burner 35, so that the oil vapor is burned. The result is
16
,~
, ,
~ 33~
that this source s)f oil escapilIg t~ the altmospllere is effectively cl~secI
o~f, and nea:rly all tlle oil in such air is r ecovered for reuse, either as
lubricating oil or as fuel. H~wever, i~ desired, an air exhaust vent
line 44 can be provided in lieu of line 43, ~r in additi~n t~ (as shown).
.. . . - :
If desired~ a heat exchanger can be interp~sed (as
shown) in the return line 43 to exchange heat with influent air from the
air cleaner array 32, an~i co~l and condense the oil vapor, and return -
it to the liquid phass for recoveryj to prevent oil l~ss in vapor state ~;
.
- from the oil supply.
The demister of the invention can be used in similar
manner in the oil line from compressed air drills~ air discharge
: - . - -
cylinders, pneumatic air cylinders, or other compressed air supplytanks, in which the system is lubricated) and in which lubricating oil
can enter the air used in operating the device. The demîster in this
" ~ :
15 case is put in series in the discharge line frorn the air cylinder, to
remove tha oil entrained in the air. ,
~ '' ' .- ,
"~
