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Патент USA US2113979

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April 12, 1938.
‘ I
A__. B‘o'kEM'ULLER
2,113,979‘
, SCAVENGING OF TWO-STROKE INTERNAL COMBUSTION ENGINES
Filed Nov. 29, 1955
"
'2 Shee-ts-Sheet 1
April 12, 1938.
A. BOKEMUFLER
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2,113,919 '
SCAVENGING'YOF TWO-STROKE INTERNAL COMBUSTION ENGINES
Filed Novv. 29, 1955
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, 2 Sheets-Sheet 2
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21:11am mg-v
Patented Apr. 12, 1938
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2,113,919
umrao STATES PATENT OFFICE
SCAVENGING or 'rwo-s'raoxn INTERNAL
cormus'rron ENGINES
Alh'ed Bokemiiller, Gaggenan, Germany, assign
or, by mesne assignments, to Sir W. G. Arm
strong Whitworth & C0. (Engineers) Limited,
_ Newcastle-npon-Tyne, England
Application November 29, 1935, Serial No. 52,723‘!
I
In Germany December 1, 1934
v
11 Claims. -(01. 123-65)
This invention relates to two-stroke internal
combustion engines of the kind in which the
scavenging is e?ected -by means of a main
scavenging stream and an additional scavenging
stream which is admitted to the-cylinder at the
end of the exhaust period towards the end of or
after the termination of the flow of the main
‘
scavenging stream.
_
.
The object of the present invention is to ren
m der the scavenging of the cylinder as complete
as possible by eliminating blind spots and eddying
masses of -hot combustion gases, which would
prevent the fresh charge fromreaching all parts
of the‘ cylinder and leave a certain portion‘ of the
‘is useful volume ?lled'with the residual gases which,
by giving off heat-to the fresh charge, detri
mentally reduce the weight of the charge and
thereby reduce the effective pressure during the
main. and additional scavenging ports respec
tively,
'
~-
7
Fig. 9 is an arrangement in which the suction
effect of the exhaust gases escaping as a mass
co-operates to assist the in?ow of scavenging air 5
and including 'an'electrical blower drive which is
regulated in dependence on the speed of the
engine, and
Fig. 10 is a fragmentary diagram showing an
upwardly inclined arrangement of the main scav- 10
enging ports.
.
>
In the various ?gures of the drawings like ref
erences are used for like parts.
In Figures 1 and 5 of vthe drawings a. is the
working space of the cylinder, b the power piston 15
shown in. the lower dead-centre position, 0 the
exhaust ports, the exhaust pipe being suitably so '
constructed and dimensioned that at the oper
next power. stroke. With this object in view, the , ative speed of revolution a particularly strong
present invention consists in this that the inlet
openings for the additional scavenging air are
located in the neighbourhood of the lower dead
centre of the piston'and are directed towardsthe
peripheral edge of the cylinder head so that the
additional scavenging stream ?ows without rota
tion about the cylinder axis towards the pe
ripheral comer of the cylinder space at the cylin
der head so as to sweep out the residual exhaust
suction e?ect is produced by the exhaust gases 20
escaping as a mass, d the main scavenging ports,
e1, e11 the auxiliary scavenging ports and f a dis
tributor or rotary valve, through-which the scav
enging air ?ows centrally and through openings
ea, 821 in which is conveyed at a de?nite‘ moment 25 >
to the scavenging ports 21, e11. In the cylinder
head there may be provided at g an. injection
nozzle, a precombustion chamber, a sparking plug
or the like, according to whether the engine is a
,
‘30
According to a further feature of the invention Diesel engine or a mixture compressing engine.
the exhaust openings and the inlet openings for ' 1 The main scavenging stream S1 enters the
the main scavenging stream are located in the cylinder at d radially or tangentially (see Figure
neighbourhood of the lower dead centre of the 5), with or without an upward inclination (see
Figure 10) and is conveyed along a curved path,
piston and the inlet openings for the main scav
_ 35 enging stream are directed towards the cylinder the direction of ?ow being. for instance reversed 35 }
head; so that the main scavenging stream ?ows prior to ?owing towards the exhaust ports c. It
towards the cylinder head and its direction of is however hardly possible to prevent the forma
tion of pockets W containing bodies of eddying
?ow is reversed before ?owing towards the ex
combustion gases, which cannot or can only in-'
gases located at the said peripheral corner.
30
haust openings.
4D.
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I
In the accompanying drawings the invention is
illustrated by preferred examples.
>
Fig. 1 is an axial section through the engine on
the line 1-1 of Fig; 5,
' Fig. 2 is a control diagram,
line.
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1
Fig. 6 is an axial section similar to Figure 1 but
'
w
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_
V
, inclination towards the peripheral corner of the
showing an alternative arrangement,
Fig. ‘I isa cross-section on the line VII-VII
>
.
For removing this exhaust gas residue the scav-‘ 45
enging ports e1, all are directed at an upward
Fig. 5 is a cross-section on the line IL-II in
of Figure 6,
approximately the space bounded by the broken
' '
a _ Fig.3 is‘ an elevation of the engine,
Fig. 4 is a section through a blower,
Figure 1,
sufficiently .be scavenged by the main scavenging 40 ' '
stream. This exhaust, gas residue which is not
reached by the scavenging stream S1 will occupy
-
Fig. 8 is a, section of a blower having a plural
"? ‘(by of stages‘for supvlyme air separately to the
cylinder space at the cylinder head, so that the
eddying bodies of combustion gases are divided
up (loosened or-broken up) by the additional 80 '
scavenging stream S2, 821. The admission of the
auxiliary scavenging streams must be caused to
take place‘ at such a moment that the intermixed
vor layered exhaust gas residues can escape
through the exhaust ports which are still open. I‘
2
2,113,979
For obtaining the best scavenging result and the
ing-ainto the main and the additional scavenging
maximum eiiective power, the most suitable du
ration of opening, that is to say commencement
and termination of opening, height and cross
section of the ports and the pressure of the ad
ditional scavenging air have a de?nite relation
stream.“ .\
-Both scavenging streams might, however, be‘
produced independently of one another by diiier
ent scavenging medium supplying means. In the 5
constructional form shown in Figure 8 the blower
is provided with a‘ common rotor m having two
to one another, which itself depends on the di
mensions of the engine, its speed of revolution,
the dimensions of the exhaust pipe and the de
10 sired mean e?ective pressure.
rows of blades m and m, the, one row n1 deliver
ing 'air to the pipe 01 and the other to the pipe
02. The air pressure in the pipe 01 is lower than 10
vthat in the pipe m and leads to the scavenging
ports‘ d while the pipe 02 leads to the rotary
valve f. Instead of a single compound blower.
'
In Fig. 2 a control diagram for the engine is
shown. an between A1 and A: is the opening
angle of the exhaust ports c, as between E1 and
E2 the opening angle for the main scavenging
15 stream Si and m1 between E11 and E21 the open
ing angle for the additional scavenging stream
S2, S21. Whereas the openings 11 for the main
scavenging stream are controlled only by the to
and fro motion" of the piston, the ‘control of the
20 inlet ports e1,- e11 for the additional scavenging
stream is effected on the one hand by the pis
ton and onthe other hand by the rotary valve '1‘.
The drive for the latter is made such that it will
uncover the admission of the scavenging air to
25 the inlet ports e1, all ‘through the openings e2,
e21 only at the. end of the scavenging period of
the main “scavenging'stream. the inlet period of
the additional scavenging stream, as shown in
Fig. 2, overlapping that of the main scavenging
30 stream by a certain. angle. The angle can! is
suitably about 30 to 60°. The ports for the addi
tional scavenging stream may be closed simulta—
'neously with, before or after the exhaust ports.
When the in?ow oi.’ the additional scavenging
stream ceases later than the closing of the ex
- haust. supercharging is thereby obtained, which
may be of advantage in certain circumstances.
The additional openings may also be disposed
in the vicinity oi’ the cylinder head at the periph~
as shown in Figure 8 a separate blower may be
provided for each pipe 01 and 02, each blower 15
having a single row of blades.
I
The scavenging
_
may, for example, be carried out in such a man
ner that the main scavenging stream is intro
duced into the cylinder by utilizing the depres
‘
sion left in the latter by the mass exit of the 20
burnt gases.
Such a constructional form is
shown in Figure 9. It isknown that by suitably
proporti'oning the exhaust ports C and the ex
haust pipe 01 and by producing a su?lciently ,
rapid opening of the exhaust ports the action 25
can be obtained that the burnt gases in the cyl- inder a will leave ballistically as a mass P and
produce in the cylinder a a vacuumwhich may
be utilized for the introduction of the scaveng
ing air, while the return of the burnt gases into
the'cylinder will be prevented or hindered by
the fresh charge introduced therein. This phe
nomenon contributes considerably to the reduc
tion of the load imposed on the blower shown in
Figure 3 and Figure 9. Owing to this, on the
one hand, a smaller blower can be employed and
as"
onvthe other hand the scavenging and charging
can be improved, the output being increased in
either case.
In Figure 9, p is an electric cou- 4
ery oi.’ the cylinder space as shown in Figure 6, pling to- which current is supplied through a
in which case they will do away with the eddy ' conductor q from a battery 1' which is charged
ing bodies of combustion gases W, for instance by an electric generator s driven by the engine.
by entering the cylinder space tangentially as The current supply to the coupling can be regu
shown in Figure 7.
'
,
pressor h for the scavenging air, thus enabling
'
to
lated either by hand, by means of a switch t
As will be seen from Fig. 3 the rotary control or automatically in dependence on the speed of
valve 1 may be disposed co-axially with the com- ‘ the-engine. For this puI'POSe a variable resist
45
_
the two parts to be jointly'driven in a simple
Between the valve 1‘ and the com
pressor h a coupling may be provided (which
manner.
may be capable of being disconnected).
ance w is interposed in a shunt circuit 12' which
is bridged by the resistance u, the said variable
resistance being under the control of a governor
a: on the engine. On the-speed increasing,'the 60'
, resistance in theconductor q increases and con
Fig. 4 shows a particularly suitable way-oi . sequently the current ?owing to the coupling 1:
delivering the scavenging air for the main and
the additional scavenging stream. In this case
55 the blower h is constructed as a rotary piston
compressor, the air entering at i into the casing
of the compressor and being withdrawn at k for
the main scavenging stream and’ at l for the
additional scavengingstream." As will be seen‘
60 the scavenging air vwithdrawn at l is compressed
to a considerably higher pressure than‘ the main
scavenging air withdrawn at k, which is 01' spe
cial advantage for the removal of the eddying
65
bodies oi’ combustion gases'in the cylinder space.
Suitably about two-thirds to three-quarters-of
the‘ total quantity of scavenging air is used for
the’ main‘scavenging stream and only the rela
ftiv‘ely small remainder i'or the?additional scav
' ranging.‘ The. additional scavenging air with
."drawn at l is‘ conveyed. to the rotary valve f
before‘ it enters thevcylinder space._ With this
Iafrrangementiit‘ is;_,_possible' ‘with a single blower
is weakened, whereby the blower h is released by
the coupling p from its driving member 'on the
engine. In this 'manner the blower output can
be regulated in such a manner that it only comes
into action within a predetermined lower speed
range, while above this the scavenging is taken
over wholly or, in part by the withdrawal action
of the out?owing exhaust gases which becomes
more» effective as the speed'rises.
.
-
Further, two stroke engines in which a mix
ture is compressed may be provided with a double
compressor in a similar manner to the arrange-"
ment shown in Figure 8, the‘ one row of blades
compressing scavenging air and the other row
compressing mixture. In this case the scaveng-‘
ing air enters the cylinder through the main
inlet' ports while the
enters through the
additional scavenging‘ ports during the last; 30‘ 70'
to 60" of the exhaust period.
''
In. this case the mixture must of course be
made ‘richer than would normally be ‘the case
i6 ‘swan dl?étam ~1-8cavehs1ns Pressures and‘ a . iand€provision mustzbe made tor'thorough'inter
v‘suitable distribution 01' the quantities of scaveng
mixing.
advantage'oi thisarrangement is.
3
2,1 18,979
that the scavenging can be made particularly as to direct the incoming charge through said
effective, as mixture losses need not be taken into ports towards the peripheral corners of the cyl
account and consequently a good mean pressure
is obtained. Furthermore, by this Separation the
fuel consumption is reduced.
, What-I claim is:-
,
a
I 1.‘The method in operating internal combus
tion engines, which consists inintroducing into
the cylinder an initial scavenging stream, direct
ed so as to ?ow across‘ the cylinder, before the
end of the power strokebut substantially after
the beginning of the exhaust when the pressure
in the ‘cylinder has been materially reduced, in
troducing near the end of the exhaust an addi
tional scavenging stream, directed to flow at an
inder space at the cylinder head and across or
overlapping the incoming charge through the
other portsv and means co-operating with said
second-mentioned ports including a vvalve,
whereby‘ said second-mentioned ports.are opened
shortly before the ?rst-mentioned ports are
closed and remain open during the [continuance
of the exhaust.
10
6. An internal combustion engine cylinderas
set forth in claim 5, in which the ports which
extend towards the cylinder head at an inclina
tion thereto extend towards the cylinder head
beyond the exhaust ports so as toremain open
'after the exhaust ports are closed.
7. The method in operating internal combus
cylinder so as to cross or overlap the initial scav- enging stream and give an additional impulse tion engines, which consists in introducing into
to the scavenging action towards the end of the the cylinder an initial scavenging stream, direct
ed so as to flow upwardly and across the cylinder, 20
scavenging'period, interrupting the initial scav
enging stream shortly after the introduction of before the end of the power stroke but substan—
the additional scavenging stream and continuing tially after the beginning of the exhaust when
the additional stream during the continuance of the pressure in the cylinder has been. materially
reduced, introducing near the end of the exhaust
the exhaust.
'
'
>
>
an additional scavenging stream, directed to flow 25
2. The method in operating internal combus
tion engines,_which consists. in introducing'into without rotation and at an inclination with re
spect to the cylinder axis towards the peripheral
the cylinder an initial scavenging stream, direct
ed so as to ?ow across the cylinder,‘ beforethe corners of the cylinder at the cylinder head so
end of the power stroke but substantially after as to intersect the initiaiscavenging stream, in 80
inclination towards the peripheral corners of the
the beginning of the exhaust when ‘the pressure
in the cylinder has been materially reduced, intro
ducing near the end of the exhaust an additional
scavenging stream, directed to flow at an incli~
nation towards the peripheral corners of the cyl
inder so as to cross or overlap the initial scav- _
enging stream and give an additionalimpulse to
the scavenging. action towards the end of the
scavenging period, interrupting the initial scav
enging stream shortly after the introduction of
the additional scavenging stream and continuing ‘
the additional stream during the continuance of
the ‘exhaust and ions. short time after the ter
mination of the exhaust.
terrupting the initial scavenging stream shortly
after the introduction of the additional‘ scaveng
ing stream and-continuing the additional scav
enging stream during the continuance of the ex
haust.
_
8. The method in operating internal combus 85
tion engines, which consists in introducing into
the cylinder an initial scavenging stream, direct
ed so as .to ?ow upwardly and across the cylin
der, before the end of the power stroke but sub- -
stantially after the beginning, of the exhaust 40
when the pressure in the cylinder has been ma
terially reduced, introducing near the end of the
exhaust an additional scavenging stream at a
3. The method as set forth in claim 1, in which ' higher pressure than the initial scavenging
the ‘main scavenging stream is introduced into stream, directed to ?ow without rotation and at 45
the cylinder with the aid of. the suction effect an inclination with respect to‘ the cylinder axis
of the exhaust gases escaping as a mass.
'
4. The method in operating internal combus
tion engines, which consists in introducing into
the cylinder an initial scavenging stream, direct
ed. so as to ?ow across the cylinder, before the
I towards the peripheral corners of the cylinder
at the cylinder head so as to intersect the initial
scavenging stream, interrupting the initial scav
enging stream shortly after the introduction of 50
‘the additional scavenging stream and continuing
end of the power stroke but substantially after the additional scavenging stream during the con
the beginning of the exhaust when the pressure tinuance of the exhaust.
in the‘ cylinder has been materially reduced, in ' 9. The method in operating internal combus
tion engines, which consists in introducing into
troducing near the end of the exhaust an addi
"the
cylinder an initial scavenging stream, direct-.
tional scavenging stream mixed with fuel, direct
ed so as to‘ ?ow across the cylinder, before the
ed to flow at an inclination towards the periph
end of the power stroke but substantially after
eral corners of the cylinder so as to cross or
the beginning of the exhaust when the pressure
overlap the initial scavenging stream and give in
the cylinder has been materially reduced, in
an additional impulse to the scavenging action
troducing near the end of the exhaust an addi
towards the end of the ‘scavengingperiod, inter
tional scavenging stream, directed to ?ow at an
rupting the initial ‘scavenging stream shortly inclination
towards the peripheral corners of the
after the introduction of the additional scaveng
cylinder so as to cross or overlap the initial scav
ing stream and continuing the additional stream engingv stream and give an additional impulse to
during the continuance of the. exhaust.
the scavenging action‘ towards the end of the
' 5. An internal combustion engine cylinder pro‘
scavenging period,v interrupting the initial scav
vided with a plurality of admission ports ar-. enging stream upon the introduction of the addiranged to open after the beginning of the exhaust tional scavenging stream and continuing the addi
but before the end of the power stroke, some ,
of said ports being arranged. so as to direct the tional‘stream during the continuance of the ex
incoming charge across the cylinder and to close
10. An internal combustion engine cylinder pro.
substantially before the end. of the exhaust and vided with a plurality of admission ports arranged
other of said portsextending towards the cylin
to open after the beginning of the exhaust but
der head beyond the ?rst-mentioned ports and before
the end of the power stroke, some of said
i at an inclination towards the cylinder head sov
haust.
,
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'
55
60
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65
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75
4
2,118,970
ports being arranged so as to direct the incom
ing charge across the cylinder and to close sub
stantially before the end of the exhaust and other
of said ports extending towards the cylinder
head beyond the ?rst-mentioned ports and at an
inclination towards the cylinder head so as to
’
I
incoming charge towards the cylinder head, so
that the charge ?ows towards the cylinder head
and its direction of ?ow is reversed before ?ow
ing towards" the exhaust ports, and to close sub
stantially before the end of the exhaust, addi
1
1
tional admission ports located in the cylinder
direct the incoming charge throwh said ports wall in the neighbourhood of the lower dead cen
without rotation about the cylinder axis towards ' tre oi’ the piston but extending towards the cyl
the peripheral corners of the cylinder space at the , inder head beyond the ?rst mentioned ports
cylinder head and across or overlapping the in
coming charge through the other ports, and
and at an inclination towards the cylinder head 1
‘so as to direct the incoming charge through said‘
means co-‘operating with said second-mentioned ' ports} without rotation about the cylinder axis
ports including a valve, whereby said second-men
tioned ports are opened shortly before the ?rst
is
mentioned ports are closed and remain open dur
ing the continuance of the exhaust.
11. An internal combustion engine cylinder
provided with exhaust ports and admission ports
located in the cylinder wall in the neighbourhood
of the lower dead centre of the piston, said ad
mission ports being arranged so as to direct the
towards the peripheral corner of the cylinder head
and across or overlapping the incoming charge
through the other ports, and means co-operating
with said second-mentioned ports including a
valve, whereby said second-mentioned ports are
opened shortly before the ?rst-mentioned ports
are closed and remain open during the continu
ance of the exhaust.
v
24
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