US2778348A - Engine scavenging means - Google Patents

Description

Filed Nov. 25, 1953 Inventor 0R% 1 /%fci1/ai Attorney 2,77s,s4s ENGINE SCAVENGTNG MEANS Worth H. Percival, Birmingham, Mich, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application November 25, 1953, Serial No. 394,241

11 Claims. (Cl. 123-65) This invention relates to two-stroke cycle internal combustion engines generally and more particularly to scavenging means for use within such engines.

In a two-stroke cycle engine there is a limited period of time allowed for the scavenging of exhaust gases and the induction of a fresh charge within the engine cylinders. Both operations must be accomplished in the brief interval during which the inlet ports are uncovered by the reciprocating piston. The scavenging of exhaust gases should be accomplished in a very minimum of time to allow for a longer induction period and to thereby insure a greater combustible charge being introduced within the engine cylinder to provide increased engine performance. Despite the advantages of minimizing the time allowed for scavenging the engine cylinder it is still imperative that effective scavenging be accomplished. Any exhaust residue remaining within the engine cylinder will minimize the amount of fresh charge which may be inducted, pmvide a noncombustible factor, and will consequently actually reduce the efliciency of the engine.

In the past numerous means have been devised for bafiiing and redirecting the incoming air. Such means have generally been employed with two-stroke engines having piston controlled inlet and outlet ports and are principally adapted to cause a loop scavenging effect. While these devices do provide for a more rapid removal of exhaust gases than in those engines which do not employ such means they are still not entirely satisfactory in that they fail to completely remove the spent charge. It has been found that all such baffling means used in the past have invariably caused the creation of cross currents and eddies which entrap the exhaust gases and actually prevent their removal from the engine cylinders. Further, in uniflow scavenging systems using such baffles or deflection means a reverse flow of exhaust gases down the sides of the engine cylinder walls and away from the exhaust ports in opposition to the surge of air centrally through the cylinder has resulted.

It is now proposed to provide a device for effecting a much more satisfactory scavenging of the engine cylinders of two-stroke cycle engines than has ever heretofore been attained. It is an object of this invention to provide a device which may be associated within the inlet port of an engine cylinder for effecting a more rapid and thorough removal of spent gases. It is another object of this invent-ion to provide a device which will not cause the formation of cross currents and eddies known to entrap and hold exhaust gases within the engine cylinder. It is still another object of this invention to provide a device for use within all two-stroke cycle engines which is adapted to direct the scavenging air along the cylinder walls for sweeping them clean of exhaust gases and for preventing the reverse flow so prevalent in uniflow and other scavenging systems.

The present device makes use of deflection plates or blades of predetermined curvature, insertable within the air intake ports of any two-stroke cycle engines. A portion of the incoming air is deflected transversely from "ice its normal flow path and directed vertically and closely along the side walls of the engine cylinder. The deflection plates are further arranged tangentially with respect to an imaginary circle within the engine cylinder to provide a slight swirl of scavenging gases for washing clean the entire cylinder wall above the induction ports.

It is another object of this invention to provide device which is adaptable for use within the intake ports of all two-stroke cycle engines either as a modification to present installations or as a revision to engines under production. This device may be readily inserted within an induction port with but slight alteration to the cylinder liner. The present device is easy to manufacture, exceedingly simple in structure, requires no precision alteration or machining of presently installed equipment, is inexpensive, and contributes appreciably to the overali efliciency of any engine.

Figure 1 is a cross-sectional side elevational view of a part of an engine showing an engine cylinder having the present invention embodied therein.

Figure 2 is a view of a part of the engine cylinder shown in Figure 1 enlarged to more clearly show the present device and its position within the induction port of such cylinder.

Figure 3 is an isometric view of the present embodiment of this invention removed from the induction port of an engine cylinder.

Figure 4 is a fragmentary cross-sectional view through Figure 1 taken in the plane of line 4-4 and viewed in the direction of the arrows thereon.

Thepresent invention is hereinafter described as incorporated within a two-stroke cycle, unifiow diesel engine. The engine comprises a cylinder block 12 having engine cylinders 14 formed therethrough. Cylinder liners 16 are inserted within each of the engine cylinders 14 and cooling passages 18 are formed through the block and about all of the cylinders- Air induction passages 20 are also formed within the engine cylinder block 12 and communicate with intake ports 22 formed through the liner 16. The inlet ports 22 are formed through the liners 16 circumferentially about the liner and tangentially with respect to an imaginary circle within the engine cylinders. A cylinder head 24 is secured to the cylinder block 12 and has exhaust passages 26 formed therein which communicate with the engine cylinders 14. Exhaust valves 28 are adapted to close and open the exhaust passages to the engine cylinder. It is apparent that scavenging air introduced through the intake ports 22 is adapted to pass through the engine cylinders 14 and out the exhaust passages 26.

A piston 30 secured to a crank arm 32 is driven up and down within the engine cylinder 14. The piston is adapted to close the intake ports 22 during its upward stroke and to open or uncover the ports during its downward motion.

An air bafliing or deflecting device 34 embodying the principles of this invention is secured within each of the intake ports 22. The air deflection device 34 comprises two deflection plates or blades 36 secured transversely across a rib member 38. The r-ib member 38 is adapted to be vertically disposed across each inlet port 22 and is comparatively thin to provide a minimum restriction to air inducted through such ports. The deflector plates 36 are likewise thin and adapted to provide a minimum restriction to air flow. The deflectors 36 are pie-formed to a selected curvature. The curvature imposed upon the deflectors is dependent upon thethickness of the liner 16 and is adapted to conform to a quarter circle having a radius equivalent to the thickness of the liner. The convex side of the deflectors 36 face within the engine cylinder 14 and curve upwardly towards the top of the cylinder. The deflector plates 36 are centrally secured to the rib 3 member 38 and spaced apart a distance equivalent to the radius of their curvature, which is likewise the thickness of the cylinder liner 16.

Vertical slots or grooves areformed within the engine cylinder liner 16 across each of the air inlet ports 22. The slots 40 extend inwardly from the Outer surface of the liner 16 in a direction parallel to the tangential line upon which the ports 22 are formed. The rib members 38 of the deflector devices 36 are inserted within the slots-40 and are held between the liner 16 and the walls forming the engine cylinder 14 by frictional engagement, spot welding or any other convenient means. The deflector plates 36 are adapted to extend from the outer surface of the liner 16 to its inner surface with their innermost edge lying tangential to the wall of the cylinder liner. The uppermost deflector plate 36 is adapted to engage the innermost upper edge of the inlet port 22 within which it is disposed. The width of the deflector plates 36 conforms to the width of the inlet ports 22 and because of the tangential alignment of such ports with an imaginary circle within the cylinder, as aforementioned, are not perfectly rectangular in shape.

During the scavenging cycle of the engine, the piston 30 on its downward motion uncovers the air inlet ports 22 allowing scavenging air to be inducted through the induction passages 20 to the engine cylinders 14. At the same time the exhaust valves 28 are opened. The major portion of the air inducted passes directly through the inlet ports and across the face of the piston 30. A part of the air however is received against the deflector plates 36 and is deflected by the plates from its normal direction of flow vertically upward along the sides of the cylinder liner 16. The tangential alignment of the deflector plates 36 with respect to the inner surface of the liner 16 causes the air to adhere closely to the liner wall. The offset of the inlet ports 22 from the cylinder radius further causes the air to travel in a swirling motion, thereby sweeping clean the entire cylinder space above the inlet ports 22. The deflectors 34 expedite the scavenging of the engine cylinder so effectively that a greater period of time is available for the induction of a fresh charge within the engine cylinder before the piston 30 raises to close off the inlet ports 22.

In the present embodiment of the invention a deflector device 34 has been provided which is adaptable for use in modifying presently installed engines. However, it should be readily forseeable that the deflector plates 36 might be formed directly within a cylinder liner or means might be provided for securing such plates within liners without the necessity of providing the rib member 38. It is also to be noted that although the concave side of the uppermost deflector plate 36 does obstruct the flow of a part of the air which would otherwise be inductced within the engine, there is generally more than ample air directed through the inlet ports 22. The use of the uppermost plate provides a curvature to the inlet port which is otherwise most diflicult to obtain by any presently known machining process. In the event that the modification is felt to impair the quantity of air otherwise received, the inlet ports may be enlarged to offset the disadvantage.

I claim:

1. A fluid deflecting device adaptable for association within the outlet opening of a fluid flow passage for the right angle deflection of a fluid passing therethrough and comprising a plurality of deflector plates adjacently arranged, means for securing said plates together and in parallel spaced relation to eachother across said opening, said plates having a radius of curvature substantially equal to the distance separating said plates and being extended in the same direction to lie tangential to and terminate at a plane transversely of the direction of fluid flow through'said passage.

2.' A fluid deflecting device adaptable for association within the outlet opening of a fluid flow passage for the right angle deflection of a fluid passing therethrough and comprising a plurality of deflector plates adjacently arranged, means for securing said plates together and in parallel spaced relation to each other across said opening, said plates being formed to provide quadrants having a radius of curvature substantially equal to the distance separating said plates and each being extended in the same direction and terminating upon intersection with a plane tangential to all of said plates.

3. A fluid deflection device adaptable for association within the outlet opening of a fluid flow passage for the right angle deflection of a fluid passing therethrough and comprising a plurality of deflector plates adjacently arranged, means for securing said plates together and in parallel spaced relation to each other across said opening, said plates being similarly curved in the same direction and having a radius of curvature substantially equal to the distance separating said plates, the outermost ends of said plates terminating upon intersection with a plane tangential to all of said plates and the innermost ends terminating upon perpendicular intersection with a planethrough said passage parallel to said first plane.

4. A fluid deflection device adaptable for association within the outlet opening of a fluid flow passage for the right angle deflection of a fluid passing therethrough and comprising an elongated spacer rib adapted to be secured across said outlet opening, a plurality of deflector blades secured in parallel spaced relation transversely across said rib, said blades being formed to provide quadrants having a curvature whose radius is substantially equal to the distance separating said blades at their innermost ends, the outer ends of said blades being adapted to extend outwardly to the edge of said outlet opening and to curve in the same direction.

5. In a two-stroke cycle engine having air inlet openings formed circumferentially about the engine cylinders, 21 deflector disposed within said openings for directing the inducted charge vertically upward and along the walls of said cylinders, said deflector comprising a spacer rib having a plurality of baflle blades secured transversely thereacross, said ribs being secured within said cylinder walls and across said openings, said blades being curved upwardly and terminating in the plane of the inner surface of said cylinder wall, the uppermost of said blades engaging the wall forming said openings for providing a rounded inlet opening. a

6. A cylinder liner for two-stroke cycle engines having air inlet ports formed through said liner circumferentially therearound, and scavenging air deflection blades secured within said ports, said blades being formed to provide a quadrant having a radius of curvature substantially equal to the thickness of said liner and being adapted to extend across said ports between the inner and outer surfaces of said liner in parallel spaced relation.

7. A cylinder liner for two-stroke cycle engines having air inlet ports formed through said liner circumferentially therearound and obliquely with respect to the radius of said liner, scavenging air deflection blades secured within said ports, said blades having a radiusof curvature substantially equal to the thickness of said liner and being adapted to extend horizontally across said ports from the inner to the outer surfaces of said liner in parallel spaced relation. t

8. A cylinder liner for two-stroke cycle engines having air inlet ports formed through said liner eircumferentially therearound and obliquely with respect to the radius of said liner, scavenging air deflection blades secured Within said ports for the'helical deflection of air flowing therethrough about the inner wall of said liner, said blades having a radius of curvature substantially equal to the thickness of said liner and being adapted to extend horizontally across said ports from the inner to the outer surfaces of said liner, said blades being spaced apart a distance substantially equal to their radius of curvature and terminating in a common plane tangential to said blade and transversely of said passage.

9. In combination with a two-stroke cycle internal combustion engine having a cylinder block, working cylinders and air inlet and outlet passages, a liner disposed within each of said cylinders, a plurality of air inlet ports formed obliquely through said liner and circumferentially therearound, said ports communicating with said air inlet passages, deflector blades secured within said ports in parallel spaced relation, said blades having a radius of curvature equal to the thickness of said liner and being separated from each other a dimentional distance equal to said radius of curvature, the uppermost blade engaging said liner Within said opening for-providing an unobstructive surface about which scavenging air may be directed.

10. In combination with a two-stroke cycle internal combustion engine having a cylinder block, working cylinders, and air inlet and outlet passages, a liner disposed within each of said cylinders, a plurality of air inlet ports formed obliquely through said liner and circumferentially therearound, said ports communicating with said air inlet passages, and a deflector disposed within said ports, said deflector comprising a spacer rib and a plurality of deflecting blades secured to said rib in parallel spaced relation, said blades having a curvature whose radius equals the thickness of said liner and each being separated from the other a dimentional distance equal to said radius of curvature.

11. In combination with a two-stroke cycle internal combustion engine having a cylinder block, working cylinders, and air inlet and outlet passages, a liner disposed within each of said cylinders, a plurality of air inlet ports formed obliquely through said liner and circumferentially therearound, said ports communicating with said air inlet passages, and deflectors disposed within said air inlet ports for directing incoming air along the wall of said liner, said deflectors each comprising a spacer rib secured across one of said ports and having a plurality of deflector blades secured transversely thereto in parallel spaced relation and curved upwardly with a radius of curvature equal to the distance between said blades, the uppermost blade engaging the edge forming said port to provide an unobstructive surface about which said air is directed.

References Cited in the file of this patent UNITED STATES PATENTS 1,176,096 Richter et al Mar 21, 1916 2,016,344 Simmen Oct. 8, 1935 2,126,860 Alfaro Aug. 16, 1938 2,220,833 Young Nov. 5, 1940 2,244,453 Fottinger et a1. June 3, 1941 2,573,663 Hand Oct. 30, 1951 2,573,989 Sammons et a1 Nov. 6, 1951 FOREIGN PATENTS 19,784 Great Britain Sept. 1, 1913 119,224 Australia Nov. 14, 1944

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