US2131958A - Two-stroke cycle internal combustion engine - Google Patents

Description

Oct. 4, 193

' M. KDENACY wo-sraox CYCLE INTERNL COMBUSTION ENGIN 4 SheetsSheet 1' I Oct. 4', 1938, -M. KADNACY TWO-STRORE CYCLE INTERNL COMBUSTION ENGIN '4 Sheets-Sheef 2 lfiled June- 2. 1936 Oct. 4, 1938; M. KADENACY I 2,131,953

' TWO-STROKE CYLE INTRNAL, COMBSTION ENGINE Filed Juna 2, 1936 .4 SheetsShet 3 Oct. M. ZKAI5ENACY June 2. 1936 4 Sheets-Sheet 4 Filed 9&A

Patenteol ct. 138

UNE' Smrn TWO- STROKE Bfichefi' Kadenacy; Paris, France Application d'une 2, i936, Serial No. 83,120 lin Great Britain .nly 3, 1935 8 Cia.

This invention relates to two-stroke cycle internal combustion engines wherein at least a substantial portion of the burnt gases-leaves the cylinder at a speed much higher than that obtaining when an adiabatic fiow oniy is involved, and in such a short interval of time that it is discharged as a mass leaving a depressionbehnd it which is utilized in introducing a fresh charge into the cylinder by opening the inJet orifice with the required deiay aftenthe opening of the exhaust orifice to ensure that the burnt gases are then moving outwardly through the exhaust orifice or duct and that a suction efiect is exerted at the iniet orifice as a consequence of the exit of the said mess.

An interna] combustion angine of this type is described in the inventors prior U. S.- A. specification No. 2,102,559

In such angines when the exhaust orifice flrst commences to open there is a period of delay during which the gases do not emerge from the cylinder, and after this delay has elapsed the burnt gases issue as a mass, at high velocity, and by passing through the exhaust orifice form a column moving rapidly in the direction of exhaust. "Ihereaiter this outward movement is reversed in direction and 8. return or the gases towards the cylinder takes place;

If records of pressure variations in the exhaust system are taken during the exhaust period by means which are also capable of indicating the 7 direction of movement of the gases'and which can respond to wide variations of pressure in short intervals of time, it can be determined whenthis outflowing column of burnt gases has been formed, and it can also be determined when the mass of burnt gases commences to engage With the gascons medium in the exhaust system and when the reversal in direction of movement gases traveis away frofi1 tige cylinder, v However if the reversal in di1ecti0n'of movement of the gases in the exhaust system occurs ou 'c yiinder. V

In this conneCtiO n itshould b ex piifined that 55 if the moment or rvezSal 111" direction o"mn before the xhaust closes, the in let being sti li' open, some of the charg'e may be forcd out of the yiinder and fou} gases ,ma atente: the

v ment of the gases at the 'exhaust orifice of the cylinder occurs when fresh gases have passed through the cyiinder and have followed the burnt gases into the exhaust system thereby furnishing' a valuable cooling efiect which assists the engine to operate at high outputs, the first efiect of this reverse] in direction wi1i be to cause freshgases to be 'forced back. into the cylinder' and this may be advantageous for the cha.rging. These returning fresh gases wiil be followed by burnt gases, and it is the subsequent re-entry of these burnt gases that will tend to fou] the charge.

Further, if the reversal in direction of the gases coeurs after a relatively long interval, expressed in terms of -crank angle, and the exhaust closes before this reverse] coeurs, then at the moment of closure of exhaust a depression wi1l exist in the exhauSt pipe close ,to the cylinder and consequently in the cylinder itsel1.

The object of the invention is avoid these two objections. The invention consists in closing the exhaust oriflce' of the cylinder before the return of the burnt gasesinto the cylinder occurs.

According to the invention the exhaust orifice of the cylinder may be closed before the reversai in direction of the gases in the exhaust system adjacent theexhaust orifice occurs and the charging may be completed theretter in any' suitable manner. i

Now the inventor has found that the time period elapsing betvveen the mass exit of the burnt gases and the reversal in direction of movement of these gases is substantially constant, and that as a rionsequence it extends over a larger crank angle et high engine speeds than at low engine speeds. Consequenfly at low speeds the chargihg of the engine is more fiable to be afiected adversely by the return of the burnt gases to the cylinder Which fo llows this reversal in direction and athigher speeds by a prolonged suction in.- V

the exhaust pipe. V

According to the invention this objection may be overcome in a variablespeed engin by closing exhaust before the earl iest return of the.burnt gases to the cylindrQccuis over the working V range of speeds of .the engineywhereby at low..

speeds the burnt gases are preVerited fr0m rprolonger: sucti'on existing in the exhaust system,

' direction ofthe gase'soccurs If it is desired to charge the engine by atmospheric pressure, it is evident that inlet must be opened not sooner than the moment the burnt gases commence to flow out as a mass and cause a suction to be exerted at the inlet orifice; and at varying speeds this moment 01 outfiow will vary. as stated ab0ve.

Therefore according to the invention inlet should be opened not sooner than the moment (crank angle), when the latest outfiow of the burnt gases commences, over a desired speed range.

The invention will be more fully described hereinafter witn reference to the accompanying drawings, in which:

Figure 1 shows curves of pressures existing in the exhaust pipe during the exhaust period of an engine to which the present invention has not been applied.

Figure 2 shows curves similar to those in Figure 1 taken on another engine to which the present invention has not been applied.

Figure ,3 is a suitable timing diagram for applying the present invention to such engines.

Figure 4 illustrates an embodiment of an en- 1gine suitable for carring the invention into efect.

Figure 5 shows a pressure indicating device;

Figure 6 shows one example oi. means for delaying the return of the burnt gases;

Figure 7 shows another example of means capable of delaying the return of the burnt ases.

The curves shown in Figures 1 and 2 were obtained by mounting on the exhaust dnct an arrangement such as that shown in Figure 5 which comprises a device such as that described in United States application Serial No. 82,958 fiied 1st June, 1936, and comprising a rotary ported sleeve 9 communicating through a port I0 with the interior of the duct Il and surrounded by a fixed sleeve l2 having a port I3 corresponding with that in the rotary sleeve and connected to a manometer l4 suitable to permit pressures above and below atmospheric to be indicated.

If the rotary-sleeve is rotated by the crank shaft of the engine, the ports in the fixed sleeve will coincide with those in the rotary sleeve for a given angular position'of the crank shaft, whereby a pressure indication may be obtained. By making the fixed sleeve angularly adjustable, such readings may be taken at any desired intervais over the whole 360.

Figure 1 shows a series 01 such curves taken at varying speeds on the exhaust pipe of a single cylinder opposed piston two-stroke engine having a capacity of 700 ces. The observations were made at about 18 inches from the cylinder, and over 360. In each case it will be noted that aiter a varying period of delay, the pressure in-the exhaust pipe rises rapidly to a. peak P and then falls suddenly to a maximum depression D after which the pressure again rises above atmospheflc to a second peak PI.

The first peak may be considered to be the point at which the burnt gases break down the external resistance. and commence to leave the ylinderasamassandthiswflilenfmeflioss the moment of mass exit 0! the burnt cases from the cylinder. The.point 0! maximum depression following this peak repsents pproximaly the moment at which the direction of movement of the outfiowing column is reversed. The return of the burnt anses tollowing this revenu! 01 fiow maybeeonsidedtobemflfleaflhetofid peak I 1 of the curve after the depression has been destroyed.

The exact moment when the direction of movethe exhaust orifice, for example by utilizing the means described above and replacing the manometer by a gas receiver.

Il; should be observed-that if the record is taken close to the cylinder the first peak P will approach nerer to the angular position at which exhaust opens and the peak PI will move further away, since the gases will then have to travel a shorter distance outwards before reachin g the point at which the record is taken and further to return to this point.

The point at which the curve descends below atmospheric pressure after the peak P does not necessarily indicate the exact cran]: angle at which the depression commences to form in the cylinder. It should be borne in mind that the gases are travelling outwards as a mass at a very high speed at this moment, as indicated by the 'analysis of the gases in the exhaust system, at

small crank angle included between these two' points of the curve, and that once the external path should inlet be then opened. The peak P may be considered to be the point at which such outflow occurs and in considering the crahk angle at which this peak occurs the distance at which the record is taken from the exhaust port should be taken into consideration.

In order to assist in determining the moment at which a suction commences to be exerted on the cylinder by the issuing gases, similar curves may be taken on the inlet duct.

The valve timing of the engine in question is shown in the figure, and it will -be seen that at 900 R. P. M. (full line curve) and 1300 R. P. M. (dotted line curve) the return of the burnt gases into the cylinder occurs before exhaust closes and whil inlet is also still open; whereas at 1500 R. P. M. (chain dotted curve) and at higher' the exhaust port. In this case the records were obtained at 1200 (full line curve), 1500 (dotted line curve) and 1800 (chain dotted curve) R. P. M., and it will be seen that at all these speeds the return into the cylinder occurs before exhaust closes and that at 1200 and 1500 R. P. M.,

the return occurs considerably before inlet closes.

It will therefore be seen that in order to avoid the touling of the charge by returning burnt gases in the engines in question. it will be necessary to alter the timing so that at the particular working speed desired. the exhaust orifice or the cylinder is closed before the return of the burnt gases occurs the inlet orifice of the cylinder may remain open for the charme tu be compktefl.

sary to close the exhaust orifice of the cylinder before the earliest returnof the burnt gases to the cylinder or the earliest reversal in direction of motion of the gases in the exhaust system, and in both the examples shown in Figures 1 and 2, it will be seen that if the exhaust oriflce is closed at bottom dead centre, the desired Operation may be obtained at an speeds above the minimum speed represented by such timing. A

In establishinga suitabie closure of exhaust in the manner-indicated above it should be borne in mind that it will not be profitable to attempt -to close the exhaust immediately after the inlet has opened as this will prevent any utilization of the volume of the depression or void left in the exhaust system. It will, on the contrary be adwiantageous to maintain the exhaust open still further, as in this way the volume of the depression or void left in the exhaust system adds its action to that left in the cylinder and assists in the charging.

In order to enable the timing of inlet opening to remain suitable over a range of speeds of the engine, it will be necessary to ensure that at all these speeds inlet opens when the burnt gases are moving outwrdly through the exhaust orifiee or duct as a consequence of their mass exit from the cylinder and cause a suction eiect to be exerted at the inlet. 4

By referring to Figure 1, it will be seen that as the speed of the engine increases, the angle that will eiapse between the moment the exhaust orifice commences to open-and the moment when a suction commences to be exerted in the cylinder as a consequence of the mass exit of the burnt gases will increase, although the variation in this angle for the range of speeds considered will not be so gr eat as in the case of the retum-of the gases.

In order to ensure that the opening of inlet will remain suitable ove the speed range considered it will therefcre be necessary to estabiish the timing of inlet opening in such a way that the opening of inlet is suitable at the highest engine speed, thereb ensuring that 'it will also be suitable at ail lower engine speeds.

More generaily the inlet. should be timed to open not sooner then the latest moment (crank angle) at which the mass exit of the burnt gases coeurs over the speed range considered.

For the purpose of determining. at any 'speed when the mass exit of the burnt gases commences it will be sufliCient to determine the shortest iead of exhaust opening relative to' inlet opening which will ensure that when inlet opens the exhaust gases will still issue through the exhaust duct and will exert a suction on the inlet duct.

If it is desired to delay the return of the burnt gases ai; 10W speeds in order to permit a later clOsure of exhaust, this may be eflected, for ex-' ample; by providing in the exhaust duct. sufliciently close to the cylinder, a chamber' having ecting surfaces therein se arranged as to imrt to the mass of issuing gases a gratofy motion whereby the action of these gases on the external static gases and the duration et out- Ward motion of the said gases are prolonged.

said chamber and l6 reflecting surfaces adapted to impart helical motion to the gases about their axis of motion.

Or for the same purpose a by-pass chamber may be arrangd on the exhaust duct close to the cylinder, this chamber being so' rranged that Figure 6 shows such an arrangement l being the the mass of burnt gases during its outward motion v 15 directed past this chamber but so that the returning gases tend to enter this chamber. Figure 7 shows an angine cylinder provided With such an arrangement, il being the cylinder, l8 the inlet ports, l9 the exhaust ports communicating through a short neck 20 with the exhaust pipe 2l, and22 the by-pass chamber open to the pipe 2l at the free end of the neck 20. An exhaust pipe of suitabie iength and shape will also assist in delaying the return of the burnt gases. For example the exhaust pipe should pref erabiy be outwardly flared and be of suflicient length that the returri always coeurs from a point within the exhaust pipe. If silencing means are provided these should not be placed nearer to the cylinder than the point of return.

Further it will-be of interest to restrict the variations in the crank angles at which the exhaust gases leave the cylinder to a minimum.

This may be done by facilitating the exit of the gases by suitable port design and by reducing the ificti0nal and other resistances to outflow in the exhaust duct to a minimum.

11 at high speeds exhaust opens*at a moment when the depression left by the preceding discharge still exists in the exhaust duct, the consequent reduction in the resistance to outflow will cause the burnt gases to issue sooner.

In a variable speed multi-cylinder engine this result may be obtained at relativelxf high speeds by a suitable arrangement of the exhaust ducts of the individual cylinders, and by suitably grouping thecylinders.

The eiect of such an arrangement is shown in Figure 2 in which it will be seen that at 1800 R. P. M.,- exhaust opens at a moment when a depression existe in the exhaust duct, and the gases leave the cylinder earlier then at 1500 R. P. M.

An example of a suitable timing which will ensure that inlet opening and exhaust closure Wiil occur in the desired manner over a wide range of speeds may be derived from the curves shown in Figures 1 and2 and is represented in Figure 3. 4

In this figure it will be seen that exhaust opens at E0 in the usual manner and inlet opens about 20 later at A0, whereby over the range of speeds indicated in the curve, inlet. will always open at a moment when a suction is exerted upon the inlet by the depression Ieft by the issning exhaust gases.

Exhaust and inlet then remain open together for a period of time durig which charging may A be efiected, if desired by atmospheric. pressure.

A little before bttom dead centre, exhaust is closed at EC and theadmission continues for recharging the cylinder up to a point AC established in a normal manner.

- such a timing gives an engine in which over a wide range of speeds above a predetermitied minimum exhaust closes before the return of the burnt gases to the cylinder and in which inlet opens after the depression has commenced tb exist at theinlot ports;

It should be noted that this timing is established from the curves shown in Figures 1 and 2 and that it may vary from one enne to another, according to the characteristics of the engine.

In eonsidering the return oi the gases, it shouid be noted that it is the action ci this return on the contents of the cyfinder that it is desired to avoid. For practical purposes it Wii1 be easy to seiect a moment for the ciosuxe cf e:fi1aust which wiii ensure that an objectionable action due to the return of the gases wiii be avoided, and ii; may be considered that this retum may commence to be objeotionable when the direction of outward movement of the gases in the exhaust system has been reversed and the burnt gases have reached the exhaust orifice of the cylinder.

For the purpose of completing the charging it may be of advantage to open a suppiemehtary outiet at or about the closure cf exhaust and before the closure cf inlet.

If the engine is charged by atmospherc pros sure ibis suppiementary outlet mat open to the atmosphere, whereby the inertia of the entering air may be empioyed to pass more air through the cyiinder. Or the supplementary outlet ma? communicate with means whereby a suction is exerted on the cylinder in order to assist in draw ing air through the latter.

The said supplementary outlet may for ex= ample open at SO a little after the cosure cf exhaust and close at SC 3. littie before the. 010- sure of inlet.

If the charglng isefiected by atmospheric pressure and it is desired to apply a supplementary compressed charge, this suppiementary charge will commence at G0, a little before the closure of the additional outlet, or a little before the -cl osure of the main inlet, and will terminat et CC a little after the closure of the main inlet.

It shbuld be noted that with a timing of iniet opening such as that indicated abovethe charge may be introduced by atmospheric pressure, but it is evident that if it is desired to introduce the charge under compression, this may be donc Without on that account going outside the scope of the invention. V

One example of an engine suitable for canwing the invention into effect is illustrated diagrammatically in Figure 4, which shows a c'ylinder I in which moves a piston 2 controllinginiet ports 3 and exhaust ports 4 situated at the saine end 61 the cylinder. Fuel is introduced into the cylin- ;fier by the injecter 5 situatd at the head ofthe cylinder. With such4n engine the desired clo sure of exhaust may be obtained by controlling the passage through the exhaust duct by means for exemple 01' a rotary valve 6, which will be a0tuated in such a way that it iiVill be open when the piston opens the exhaust ports 4 but willclose beiore the piston on its return stroke has closed the ports 4. A suitable timing of inlet relative'to exhaust in accordance with the invarition may then be obtained by arranging for the exhaust port opening to lead the inlet port opening by the required amount. 4 A supplementary port 1 is provided at the opposite end of the cylinder to the ports 1 and l. This supplementary port is controlled by a valve 8 which may be operated by any suitable means in order to.open as an additional outlet asindicated in Figure 3, or to serve for the introduction of a supplementatw compressed charge, as herin before described.

1. In a two-stroke cycle internal combustion angine of the kind described. a ylindr,,a piston,

an iniet port at one end of the cyiinder, an exhaust system, an exhaust port leading to the exhaust system, an additionai outiet orifice situated at the opposite end of the cylinder to the iniet port, means for closing the exhaust port cefore the return of theburnt gases to the cylinder, means for subsequently closing the inlet port, and means for opening the additionai out- 1et orifice about the time of ciosure cf exhaust and for ciosing the said orifice about the time 02'. closure of inlet.

2. in a two-stroke cycle internal combustion angine of the kind described, a. cylinder, a piston, an iniet port at one end of the cylinder, an exhaust syscem, an exhaust port leading to the exhaut system, an additional outiet orifice sit,

uated at the opposite emfi of the cylinder to the iniet port, means for ciosing the exhaust port beiore the return of the bumt gases to the cylindez, means for subsequently closing the inlet port, and means for opening the additionai outiet orifice a iittie before the closure of exhaust and for ciosing the said orifice a iittie before the ciosure cf inlet.

3. In a two-stroke cycle interna! combustion angine of the kind described, a cylinder, a piston, an inlet port at one end of the cyiinder, and communicating to atmosphere, an exhaust system, an exhaust port leading to the exhaust system, an additional outlet orifice situated at the opposite and of the cyiinder to the inlet port, means for closing the exhaust port before the return of the burnt gases to the cylinder, means for subsequently closing the inlet port, means for opening the additiona] outlet orifice about the time of closure of exhaust and for closing the said orifice about the time of closure of inlet, and means for supplying a supplementarg compressed charge to the cylinder from a little before the closure 01 the additional outlet until a little after the closure Of the atmospbefic inlet.

4. A two stroke cycle-internal combustion engine having a cyiinder, exhaust and inlet orifices in the cylinder, an exhaust conduit on the cylinder, means for 50 controlling the exhaust orifice during the firing stroke as to ensure the issuance of the burnt gases as a mass, whereby the said mass moves outwards and thereafter retums Irom a point which may be within the said conduit, means for so controlling the inlet orifice as to -ensure that it will be opened -while the exhaust orifice is still open and when the said issuance of the burnt gases is in full progress and produces a suction eifect in the cylinder, the said conduit providing a permanent free passage for the burnt gases to the limit of travel of said gasas, means for closing the said' exhaust orifice after the fresh charge has occupied the cylinder and'befor9 the instant when the pressure of the retuming"gases becomes effective within the cyiinder.

'5. A two stroke cycle interna] combustion engine having a cylinder, exhaust and inlet orifices A a in the cylinder, an exhaust conduit on the cylindex, means' for so controlling the exhaust orifice during the firing stroke as to ensure the issuance of the burnt gases as a mass, whereby the said mass moves outwards and thereafter returns tram a point which may be within the said conduit, means for so controlling the inlet orifice as to ensure that it will be opened while the exhaust orifice is still open and when the said I issuance of theburnt gases is in full progress and produces a suction effect in the cylinder, the said conduit providing a permanent free Passage for the burnt gases to the limit of travel of said gases, means for closing'the said exhaust orifice after the fresh charge has occuped the cylinder and before the instant when the pressure of the returning g ses becoines effectivewithln the cylinder, mea for closing the inlet orifice subsequent to the closure of the exhaust orifice.

6. A method of controlling two strokecycle interna] combustion engines which comprises establishing communication between the cylinder and exhaust system during the flring stroke, providing for the issuance of the burnt gases as a mass, whereby the said mass moves outward and thereafter retur ns Irom a point which may be within the said system, providiug a permanent ree passage for the burnt gases to the iimit of outward travel of said gases, preventing the entrance of fresh charging air into the cylinder until the said issuance of the burnt gases is in full progress, admiting fresh charging air into the cylinder when the said issuance of the burnt gases is in full progress and-causes a suction effect to be exerted in the cylinder while the exhaust port is still open, providing for said fresh charge to occupy the cylinder in the interval elapsing between the mass exit of the burnt gases and the interval when the pressure of tire retuming gases becomes effective within the cylinder, shutting oi the said communication between the cyiinder and the said exhaust system, after the said fresh h charge has occupied the cylinder and before the instant when the pressure of the returning gase becomes efiective within the cylinder.

7. A method of controfling two stroke cycle interna! combustion engines which comprises estabIishing communication between the clinder and exhaust system during the flring stroke, providing for the issance of the burnt gases, as a mass, whereby the said mass moves outward and thereafter returns from a point which may be within the said system. providing a permanent free passage for the burnt gases to the limlt of outward travel of said gases, preventing the entrance of fresh charging air into the cyiinder until the said issuance of the burnt gases is'in full progre, admitting tresh.charging air into after the said fresh charge has occupied the cylinder and before the instant when the pressure of the returning gases becomes eflective within the cylinder, terminating the-admission oiiresh chargng air after the said communication be-' tween the cylinder and the exhaust system has been shut off.

8. A method of controlllng two stroke cycle internal combustion engines which comprises establishing communication between the cyiinder and the exhaust system during the firing stroke,

-providing for the issuance of the burnt gases as a mass, whereby the said mass moves outward and thereafter returns from a point which may 'be within the said system, providing a permanent free passage for the burnt gases to the limit of outward travel of said gases, preventing the en' trance of .fresh chargng air into the cylinder until the said issuance of the burnt gases is in full progress, admitting fresh charging air into the cylinder when the said issuance of the burnt gases is in full progress and causes a suction eflect to be exerted in the cylinder, while the exhaust port is still open, providing for the-said charge to occupy the cylinder and a portion of the -exhaust system in the interval elapsing between the mass exit of the burnt gases and the instant when the pressure of the returnlng gaseshe comes effective within the cylinder, shutting ofl the said communication between the cyiinder and the exhaust system after the fresh charge has occupied the byiindcr and 9. portion 01 the exhaust system and beiore the instant when the pressure or the returning gases becomes effective within the cylinder;

MICHEL KADENAOY.

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