US2440310A

US2440310A - Uniflow scavenging for engines

Info

Publication number: US2440310A
Application number: US586920A
Authority: US
Inventors: Thege Edvin Ossian Parcival
Original assignee: Atlas Diesel AB
Current assignee: Atlas Copco AB
Priority date: 1944-04-06
Filing date: 1945-04-06
Publication date: 1948-04-27
Anticipated expiration: 1965-04-27

Description

April 7, 1948. 'E. o. P. THEGE 2,440,310

UNIFLOW SCAVENGING FOR ENGINES Filed April 6,- 1945 5 Sheets-Sheet 1 FIGJ April 27, 1948. E. o. P. THEGE 2,440;3

UNIFLOW SCAVENGING FOR ENGINES Filed April 6, 1945 5 Sheets-Sheet 2 FIG.4 H65 April 27, 1948.

E. o. P. THEGE 2,440,310

UN IFLOW SCAVENGING FQR ENGINES Filed April 6, 1945 5 Sheets-Sheet s April 27, 1948. E. o. THEGE 2,440,310

UNIFLOW-SCAVENGING FOR mamas Filed April 6, 194g 5 Sheets-Sheet 4 April 1948. E. o.- P. THEGE I 2,440,310

UNIFLOW SCAVENGING FOR ENGINES Filed April 6, 1945 Sheets-Sheet 5 FIG/I3 FIG.14

79 83 82 Si 93 87 88/89 J7 as a5a494 909192 Patented Apr. 27, 1948 UNIFLOW SCAVENGING FOR ENGINES Edvln Ossian Percival There, Stockholm, Sweden, assignor to Aktiebolaget Atlas Diesel, Sickla, near Stockholm, Sweden, a corporation of Sweden Application April 6, 1945, Serial No. 586,920

In Sweden April 6, 1944 1 18 Claims.

This invention relates to two stroke cycle internal combustion engines with uniflow scavenging. The invention may be employed in single or double acting engines having a single working piston in each cylinder or opposed pistons, and the invention may also be employed in tree piston engines as well as engines having crank shafts at one or both ends of the working cylinder. The invention may, furthermore, be employed in engines with solid fuel injection or in engines supplied with a mixture of fuel and air. The inven-. tion may be used in engines with-compression ignition or other ignition systems.

One object of the invention is to provide a simple, reliable and concentrated design of internal combustion engines particularly suitable for light and fast. running engines. However, my invention may also be employed in connection with conventional engines running at moderate or low speed. A further object of the invention is to provide means for scavenging and charging fluid admission to the cylinder from two opposite sides of the cylinder in such manner that rotation of the scavenging fluid in the cylinder during the scavenging period is counteracted and so that the scavenging fluid and the combustion gases are mixed as little as possible during the scavenging period and an efficient scavenging of the cylinder with low pressure losses is obtained. A further object of the invention is to provide a scavenging system causing each cylinder half to be filled up with scavenging fluid unto the central portion of the periphery of said cylinder half so that peripheral combustion gas whirls are avoided as far as possible. A still further object of the invention is to provide a design in which the efllcient scavenging system is obtained with means causing a strong whirling motion in the combustion chamber 01' the engine during the fuel injection so that favourable combustion con,- ditions are obtained which, in two stroke cycle engines, is of outstanding importance for obtaining an efllcient working process and a high mean pressure.

For these and other purposes I provide a two stroke cycle internal combustion engine with uniflow scavenging having a combustion cylinder, a plurality of substantially parallel passages leading into said cylinder at one end of the cylinder and directed substantially perpendicularly towards an axial centre plane of the cylinder and disposed on each side of said axial centre plane and distributed over the whole length of a cylinder diameter included in the centre plane, means for supplying scavenging fluid to said passages, and anoutlet at I one of the cylinders of an opposed piston engine according to the invention. Fig. 2 is a. cross section of a cylinder of said engine on line II-II in v Fig. 1. Fig. 3 is a partial section illustrating the piston position in the engine according to Fig. l at the end of the compression stroke. Fig. 4 is a transverse vertical section of an opposed piston engine according to a slightly modified embodiment of the invention, and Fig. 5 illustrates the positions of the pistons of this engine at the endof' the compression stroke. Figs. 6 and 7 are similar views of a further modification of an opposed piston engine according to the invention. Figs. 8 and 9 illustrate similar views of the engine cylinder and the piston of an engine having piston controlled scavenging openings at one end of the cylinder and an exhaust valve means at the other end of the cylinder. Fig. 10 is a section on line X-X in Figs. 6 and 8. Fig. 11 is a transverse vertical section of an engine accord- Fig. 12 is a cross section of a cylinder of said engine on line XIIXII in Fig. 11. Figs. 13 and 14 are cross sections of cylinders according to still further embodiments of engines according to the invention.

The opposed piston engine according to Figs. 1-3 consists of any number of cylinders l, a lower crank case 2 and an upper crank case 3 in which

crank shafts

6 and 5 are mounted in suitable bearings. The crank shafts may be connected with each other over a toothed gear transmission at one end of the engine or in any other way commonly used in connection with opposed piston engines. A connecting rod 6 connects the upper crank shaft 5 with an upper piston I which controls the scavenging openings of the cylinder, and a connecting rod 8 connects the lower crank shaft 4 with a lower piston 9 controlling the exhaust openings of the cylinder. scavenging consequently' takes places in a direction towards the may be provided with cooling means, or. if both pistons are cooled, with cooling means of greater cooling capacity than the cooling means of the upper piston.

Each engine cylinder is provided with two diametrically opposed supply conduits III directed perpendicularly to the longitudinal centre plane of the engine for supplying charging and scaven ing air from a not illustrated source of compressed air of any conventional design known in the art. The air flowing through the supply conduits I is admitted to the combustion cylinder through two galleries forming a number of substantially parallel scavenging air passages H, l2, l3 disposed in pairs on each side of the axial longitudinal centre plane of the engine, As obvious from Fig. 2 this arrangement results in a completely symmetrical arrangement of the scavenging air passages and the scavenging air supply conduits with reference to the axial longitudinal centre plane of the engine as well as to a plane through the cylinder axis perpendicular to said plane, and the scavenging air is distributed in a very uniform manner over the cylinder halves on each side of said axial longitudinal centre plane. The illustrated arrangement of the scavenging air supply conduits and the scavenging air passages offers a possibility to reduce the distance between adjacent cylinders in multiple cylinder engines so that the total length of the engine is reduced and crank shafts and other parts of the engine become lighter. The scavenging air passages ll disposed at the extreme sides of each scavenging air supply conduit ID are confined at the outside by walls l4 making a sharp turn of almost 90 just before the opening into the cylinder and forming guide surfaces l5 directed substantially towards the centre of the cylinder. Said guide surfaces I5 counteract the tendency of the air streams through the scavenging air passages H to continue within the cylinder in a peripheral direction and to produce a rotation of the scavenging air around the cylinder axis. The top of the piston l controlling the scavenging openings is shaped in a manner contributing to the counteraction of the rotation of the scavenging air around the cylinder axis during the scavenging period. For this purpose and in order to provide a compression chamber shape suitable for the combustion process the top of the piston I is provided with a ridge it having a flatend surface and side surfaces confined by curved surfaces Il. As obvious from Fig. 2, said curved surfaces I! are symmetrical with reference to the axial longitudinal centre plane of the engine and the portions of the surfaces ll situated near the piston periphery form guide surfaces cooperating with the scavenging air passages i2 of the scavenging air stream entering through the passages l2- towards the cylinder axis thus counteracting the formation of peripheral streams from said passages having a tendency to cause rotation of the scavenging air in the cylinder during the scavenging period. The guide surfaces I'I also assist in deflecting a portion of the scavenging air axially before it reaches the centre of the cylinder 50 that a congestion of scavenging air in the central portion of the cylinder is counteracted. The described simple and symmetrical piston shape is also advantageous with regard to the strength of the piston and from the manufacturing standpoint.

. The engine illustrated in Figs. 1-3 is a Diesel engine with solid injection at two points of each engine cylinder I opposite each other. Fuel injection devices It are provided one on each side of the axial longitudinal centre plane of the engine. The lower piston 9 has a ridge l9 formed on the top of the piston and shaped with a flat end surface substantially similar to the end surface of the ridge ii of the piston I. The piston 9 controls the exhaust openings 20 of the engine through which the conbustion gases are expelled during the scavenging period into two symmetrically opposlte exhaust gas conduits 2|. When the pistons are in compression position the ridges l6 and I9 divide the combustion chamber of the engine in two separate spaces which are confined laterally by the wall of the engine cylinder and the curved surfaces ll of thepiston I and the corresponding curved surfaces 22 of the piston 9 and axially by the end surface of the pistons. With respect to said spaces the fuel in- Jection devices 18 are disposed near the centre of the curved surfaces ll so that the fuel jets expelled in fan shape from the fuel injection devices have substantially the same distance to travel before they reach the surfaces [1 and 22.

In the inner end position of the pistons a narrow slit or gap 23 is formed between the and surfaces of the ridges l6 and I9 from which slit or gap air is expelled at the end of the compression stroke forming air jets in the combustion chamber substantially as indicated by the arrows 24 in Fig. 3. Said air jets produce a strong whirling motion in the combustion chamber of the engine so that a uniform distribution and a satisfactory mixture of fuel and air is obtained. The

fuel injection devices may be carried out in such a. manner that they produce fan shaped

jet bundles

25 and 26 directed towards the pistons and contributing to the whirling motion as indicated by the arrows in Fig. 3.

The above described engine according to the invention substantially operates in such a manner that very little whirling and consequently the least possible mixture of the scavenging air and the combustion gases takes place during the scavenging and charging of the cylinder whereas a strong whirling motion is obtained in the combustion chamber of the engine at the end of the compression stroke favouring the combustion process and. causing a good mixture of the fuel and the air.

In the modifications and further embodiments of the invention illustrated in Figs. 4-14 parts corresponding to equivalent parts in Figs. 1-3 have been designated with the same reference numerals and in the following portions of the specification the differing parts only are described in detail.

In the modification of the engine according to Figs. 1-3 illustrated in Figs. 4 and 5 the upper piston 1 is provided with a high ridge 2'] and the lower piston 9 with a lower ridge 28. In the innermost position of the pistons a narrow slit or gap 29 is formed between the

ridges

21 and 28 and said gap i situated nearer the lower piston in the combustion chamber than the upper piston. Consequently the air jetsforces out of the gap 29 move over the surface of the lower piston, as indicated by the arrows 30, and force the fuel jets towards the upper piston, as indicated by the arrows 3| in Fig. 5. A further advantage of the high ridge 2'! and the low ridge 2B in this modification is that an increased guide action on the scavenging air by the ridge 2! is obtained.

In the modification of the engine according to Figs. 1-3 illustrated in Figs. 6, 7 and 10 the upper piston i only is provided with a ridge 32 running straight across the top ofthe piston'in the direction of the longitudinal centre plane of the engine. The peripheral portions of the side surfaces of the ridge 32 coact with the guide surfaces II to counteract the formation of peripheral air streams in the cylinder from the sidemost passages ll leading from the two air supply conduits to the interior oi. the cylinder. At the end of the compression strokethe ridge 32 together with the flat end surface of the piston 8 forms a narrow slit or gap 33 from which air is expelled so that a whirling action is obtained in the combustion chamber at the end of the compresnection with the embodiments according to Figs.

. 1 and 10 or in any other suitable way.

, sides or the longitudinal centre plane of the engine through

supply conduits

55 and 58. The air supplied through the conduit 55 flows during the scavenging period through the scavenging passages 51. I8, 53 and the substantially opposed sion stroke. as indicated by the arrows 34 and 35in F18. 7.

Figs. 8, 9 and 10 illustrate the employment of the invention in connection with an engine having a single working piston 38 operating in cylinder 31 and controlling scavenging openings 38 in said cylinder to which scavenging air is supplied from two directions as obvious from Fig. 10. The cylinder 31 is provided with an outlet valve means such as a mushroom valve 89 in the end of the cylinder opposite the scavenging openings but may naturally be provided with a piston valve of the same or less diameter than the cylinder diameter. Furthermore, the cylinder is provided with fuel injection valves or ignition means or the like 40. The piston 36 is provided with a ridge ti the side surfaces of which help to guide the scavenging air in the same way as the ridge 32 according to Figs. 6, 7 and 10. At the end of thecompression stroke a narrow slit or gap 44 is formed between the end surface of the ridge iii and the cylinder head 43 and the valve 39. Air jets 45 expelled from said gap produce together with fuel jets 46 a whirling action at the end of the compression stroke.

In the embodiment of the invention illustrated in Figs. 11 and i2 scavenging air is supplied to the engine cylinder through two scavenging air supply conduits 41 directed towards each other and inclined away from the piston i controlling the scavenging openings. Said piston may preferably have a bevelled portion as indicated at 48. oppositely directed scavenging air streams enter the cylinder through the

passages

49, 50, 5| from both sides of the axial longitudinal centre plane of the engine. The passages 49, 5D and 5i are inclined downwards towards the lower piston so that the scavenging air at the entrance into the cylinder already has an axial component movement. In order to counteract the tendency of forming scavenging air streams in the. cylinder tending to rotate the scavenging air the outer walls 52 of the sidemost scavenging air passages is leading from the supplyconduits 41 to the cylinder just before the opening into the cylinder make a sharp turn of almost 90. The guide surfaces 53 deflect the air towards the cylinder axis and counteract the formation of peripheral scav-- enging air streams in the cylinder. In similar manner the outer walls 54 of the passages 50 just before the openings into the cylinder make a turn towards the cylinder axis in order to prevent that scavenging air entering through said passages shall get a chance to cause rotation of the scavenging air in the cylinder during the scavenging period. In the embodiments accord ing to Figs. 11 and 12 the upper piston! and the lower piston 9 have both substantially fiat end surfaces but naturally the pistons may be formed in similar manner as the pistons described in con.-

scavenging passages 80. BI, 62 of the one cylinder half 83 whereas scavenging air supplied through the conduit 58 and the scavenging passages "-33 enters the cylinder and fllls up the other cylinder half 10. Guide surfaces ii, 12, 13, 14 then assist in counteracting the formation of peripheral scavenging air streams in the cylinder during the scavenging period. At least the piston controlling the scavenging openings may be provided with a, ridge I! as indicated by the chain dotted lines in Fig. 13 and/or with a ridge 18 which is also indicated by chain dotted lines. In the latter case and generally in engines with very large cylinder diameters fuel injection valves or ignition means may be provided in axial planes indicated by the

lines

11 and 18.

Fig. 14 is a cross section through the scavenging opening zone of a cylinder ofan engine with unifiow scavenging which may otherwise be carried out for instance as illustrated in Figs. 1, 4, 6, 8 and 11 or in any other suitable way. The two scavenging air conduits 1s and 30 communicate with a number of parallel and opposed scavenging passages "-86 and 81-92, respectively, through which scavenging air is admitted into the cylinder. The scavenging air streams through the passages 8|-83 and 81-89 meet in the cylinder and fill one half of the cylinder unto the central peripheral portion 93 of said cylinder half and are then deflected axially for driving the combusion gases towards the combustion gas outlet. In the same way the scavenging air streams entering the cylinder through the passages 8486 and 90-32 fill up the other half of the cylinder unto the peripheral portion 94.

The embodiments above described and illustrated in the drawings should only be considered as examples and-the invention may be modified and the diflerent elements combined in several difierent ways within the scope of the claims. 4

For instance, in engines supplied with a mixture of fuel and air through the supply conduits i0, 41, 55, 58, I3, the fuel injection valves l8 may be replaced by spark plug 1 What I claim is: v

1. In a two stroke cycle internal oombustion engine with uniflow scavenging, a combustion cylinder, a plurality of substantially parallel passages leading into said cylinder at one end of the cylinder and directed substantially perpendicularly towards an axial centre plane of the cylinder and disposedfon each side of said axial centre plane and distributed over the whole length of a cylinder diameter included in the axial centre plane, means for supplying scavenging fluid to said passages, and an outlet at the opposite end of the cylinder.

2. In a two stroke cycle internal combustion engine with uniflow scavengin ,v a combustion cylinder, a reciprocating working piston in said 7 the cylinder and directed substantially perpendicularly towards an axial centre plane oi the cylinder and disposed on each side of said axial centre plane and distributed over the whole length of a cylinder diameter included in the axial centre plane, two opposed scavenging fluid supply conduits disposed one on each side or an axial ing fluid supply conduit is divided in two branches leading to groups of parallel passages.

4. In a two stroke cycle internal combustion engine with uniflow scavenging, a combustion cylinder, scavenging openings in said cylinder at one end or the cylinder, a plurality of substantially parallel passages leading to said scavenging openings and directed substantially perpendicularly towards an axial centre plane of the cylinder and disposed on each side of said axial centre plane and distributed over the whole length of a cylinder diameter included in the axial centre plane, a reciprocating working piston in the cylinder controlling the admission through the scavenging openings, a ridge extending substantially diameterically over the top of said piston, means for supplying scavenging fluid to said pas- 'sages, and an outlet at the opposite end of the cylinder.

5. In a two stroke cycle internal combustion engine with uniflow scavenging, a combustion cylinder, a reciprocating working piston in said cylinder, a plurality of substantially parallel passages leading into said cylinder at one end of the cylinder and directed substantially perpendicularly towards an axial centre plane of the cylinder and disposed on each side of said axial centre. plane and distributed over the whole length of a cylinder diameter included in the axial centre plane, a ridge extending substantially diametrically over the top of said piston perpendicularly to said passages, guide surfaces on each side of said ridge for axially deflecting a portion of the fluid entering the cylinder through the passages, means for supplying scavenging fluid to said passages, and an outlet at the opposite end of the cylinder.

6. In a two stroke cycle internal combustion engine with uniflow scavenging, a combustion cylinder, a reciprocating working piston in said cylinder, scavenging openings in the cylinder at one end of the cylinder, a plurality of substantially parallel passages leading to said scavenging openings and directed substantially perpendicularly towards an axial centre plane of the cylinder and disposed on each side of said axial centre plane and distributed over the whole length of a cylinder diameter included in the axial centre plane, a ridge extending substantially diametrically over the top of said piston perpendicularly to said passages, guide surfaces on each side of said ridge co-operating at the peripheral portions of the piston with walls confining said passages for deflecting a portion of the fluid entering the cylinder through the scavenging openings tangentially towards the centre of the cylinder, means for supplying scavenging fluid to the passages, and an outlet at the opposite end of the cylinder.

7. In a two stroke cycle internal combustion engine with uniflow scavenging, a combustion cylinder, a plurality of substantially parallel passages leading into said cylinder at one end of the cylinder and directed substantially perpendicularly towards an axial centre plane oi! the cylinder and disposed on each side of said axial centre plane and distributed over the whole length of the cylinder diameter included in the axial centre plane, walls confining the outside 01 said sidemost passages making a sharp almost turn towards the cylinder centre just before the inlet into the cylinder and forming guide surfaces for counteracting the formation for tangential fluid streams in the cylinder during the scavenging period, means for supplying scavenging fluid to the passages, and an outlet at the opposite end of the cylinder.

8. A two stroke cycle internal combustion engine according to claim 7 in which the second sidemost passages are confined by walls of which the most tangentially disposed makes a sharp turn just before reaching the opening into the cylinder for preventing the formation of tangential fluid streams in the cylinder.

9. In a two stroke cycle internal combustion engine with uniflow scavenging, a combustion cylinder, a plurality of substantially parallel passages leading to scavenging openings in said cylinder at one end of the cylinder and directed substantially perpendicularly towards an axial centre plane of the cylinder and disposed on each side of said axial centre plane and distributed over the whole length of a cylinder diameter included in the axial centre plane, a reciprocating working piston in the cylinder controlling the admission through the scavenging openings, a ridge extending substantially diametrically over the top of said piston and having an end surface which at the end of the compression stroke of the engine forms a narrow slit or gap with adjacent portions of the engine dividing the combustion chamber at that moment in two spaces and setting up fluid jets projecting from said slit or gap, means for supplying scavenging fluid to said passages, and an outlet at the opposite and of the cylinder.

10. A two stroke cycle internal combustion engine according to claim 9 in which the ridge is broader towards the periphery of the piston.

11. A two stroke cycle internal combustion engine according to claim 9 in which means for initiating combustion are provided in the cylinder for each space.

12. A two stroke cycle internal combustion engine according to claim 9 in which fuel injection means are provided in the cylinder for each space.

13. A two stroke cycle internal combustion engine according to claim 9 in which the ridge is confined laterally by two arcuate surfaces having their centre near the cylinder wall, and fuel injection means are provided in the cylinder for each space near said centres.

14. In a two stroke cycle internal combustion engine with uniflow scavenging, a combustion cylinder, a plurality of substantially parallel passages leading to scavenging openings in said cylinder at one end of the cylinder and directed substantially perpendicularly towards an axial centre plane of the cylinder and distributed over the wholev length of the cylinder diameter included in the axial centre plane, opposed working pistons in the cylinder one of which controls the admission through the scavenging openings, a ridge extending in the same way substantially diametrically over the top of each one or said scavenging fluid to said passages, and an outlet at the opposite end 01' the cylinder.

15. A two stroke cycle internal combustion engine according to claim 14 in which the ridges on the opposed pistons are of equal height. a

16. A two stroke cycle internal combustion engine according to claim 14 in which the ridge on the piston controlling the scavenging openings is higher than the cam or ridge on the other piston.

17. In a two stroke cycle internal combustion engine with unifiow scavengin a combustion cylinder, a plurality of substantially parallel passages leading to scavenging openings in said cylinder at one end of the cylinder and directed substantially perpendicularly towards an axial centre plane of the cylinder and distributed over the whole length of the cylinder diameter included in the axial centre plane, opposed working pistons in the cylinder, a. ridge extending substantially diametrically over the top of one of said pistons and having an end surface which at the end 01 the compression stroke of the engine forms a narrow slit or gap with adjacent portions of the engine dividing the combustion chamber in separate spaces, a fuel inlection device having nozzles directing fuel Jets in fan shape towards said piston, means for supp y ng scavenging fluid to the passages. and an outlet at the g opposite end of the cylinder.

in the upper end oi said cylinder and directed substantially perpendicularly towards an axial centre plane of the cylinder and disposed on each side of said axial centre plane and distributed over the whole length of a cylinder diameter included in the axial centre plane, opposed working pistons in the cylinder, means for supplying scavenging fluid to the passages, and an outlet at the lower end of the cylinder.

EDVIN OSSIAN PARCIVAL THEGE.

' REFERENCES CITED The following references are of record'in the file oi this patent:

STATES PATENTS Number Name Date 2,281,821 Balmer May 5, 1942 1,485,988 Michel Mar. 4, 1924 1,486,583 Huskisson Mar. 11, 1924 1,353,100 Wales Sept, '14, 1920 1,693,506 Hemmingsen Nov. 27, 1928 2,228,832 Lieberherr Jan. 14, 1941 FOREIGN PATENTS Number Country Date 369,769 England 1932 272,978 Germany 1914 1 320,839 England 1929 372,191 England 1932 engine with uniilow scavenging, a vertical com- V bustion cylinder, a plurality of substantially parallel passages leading to scavenging openings