WO1988000281A1

WO1988000281A1 - Multi-phase combustion system for piston internal combustion engines

Info

Publication number: WO1988000281A1
Application number: PCT/AU1987/000209
Authority: WO
Inventors: Robert Walter Vowles
Original assignee: Engine Technology Limited
Priority date: 1986-07-09
Filing date: 1987-07-09
Publication date: 1988-01-14

Abstract

In a reciprocating piston engine a peripheral cavity (6) surrounds each engine cylinder (8) adjacent a cyclinder head (4) of the engine. A plurality of ports (7) provide communication between the cavity (6) and the cylinder (8), the ports (7) being opened and closed by passage of the piston (9) whereby a portion of the charge is received and sealed in the cavity (6) during the engine compression stroke. Following ignition, the power stroke takes place in two stages; a primary combustion stage while the ports (7) are covered by the piston (9) followed by a secondary combustion stage when the ports (7) have been uncovered by the descending piston (9) to re-establish communication between the cylinder (8) and the cavity (6).

Description

MULTI-PHASE COMBUSTION SYSTEM FOR PISTON INTERNAL COMBUSTION ENGINES

The invention concerns means by which a multi-phase combustion process may be achieved in piston internal combustion engines.

In the spark ignited internal combustion engine, combustion occurs in a multi-phase manner. Following the first phase, the establishment of a self-sustaining body of flame adjacent to the spark plug, a flame front propagates rapidly throughout the combustion chamber in what may be termed the primary combustion event. Very little piston movement occurs during this process. As the piston descends, further combustion occurs of areas of lean mixture, of quench products scoured by turbulence away from the combustion chamber walls and of mixture trapped in narrow parts of the combustion chamber. This process may be termed the secondary combustion event.

Methods have been devised to retard the combustion events in a manner calculated to make their duration more consistent with piston movement. One such method involves the fixing of a false crown to the piston, the diameter of the said .false crown being smaller than the cylinder bore in a way which provides a narrow annular opening around its periphery. During the compression stroke, mixture is forced through the said narrow annular opening into the area beneath the said false crown, being released during the firing stroke. This release of mixture has the effect of prolonging the secondary combustion event and improving engine torque and fuel economy.

The shortcomings of this arrangement are complexity of manufacture, the problem of cooling the false piston crown during high power operation, and the increased parasitic losses resulting from the increased reciprocating mass .

The present invention has for its object the provision of an arrangement in an internal combustion engine which will achieve a prolonging of the secondary combustion event without the disadvantages of the method described in the foregoing paragraph.

Accordingly the present invention provides an internal, combustion engine having at least one cylinder in a cylinder' block with a piston reciprocable therein and a cylinder head closing an upper end of the or each of said cylinders, the improvement comprising the provision of at least one recess in a wall of the or each of the said cylinders adjacent said cylinder head forming a chamber adapted to- receive combustible charge materials from the cylinder: a jacent thereto through a restricted access opening: ox: σp-enings.

According to a preferred arrangement, the upper part of the cylinder block of a piston engine is made such that an annular recess of rectangular cross-sectional shape is provided at the top of the or each of the cylinder bores.

Accommodated within the said annular recess and imprisoned by the cylinder head may be provided one or more rings incorporating at l.east one and preferably an annular space forming said chamber communicating with the cylinder through a plurality of ports, said ports being positioned such that they are covered by the piston as it approaches top dead centre. The inner face of the said ring or rings may be honed to make than a smooth contiguous extension of the engine upper cylinder bore. The cylinder bore area between the said discharge ports is such that adequate bearing surface is provided for the piston rings.

The present invention will be more readily understood by reference to the following description of preferred embodiments given in relation to the accompanying drawing which depicts a transverse sectional view of an engine cylinder block embodying the invention.

With reference to the drawing, a recess 1 is provided in cylinder block 5 at the top of cylinder bore 2, in said annular recess being acco odated ring 3 imprisoned by cylinder head 4. Said ring is fitted into cylinder block 5 in an interference fit to provide good heat transfer properties, and its inner surface 10 is honed to make it a smooth contiguous extension of the engine upper cylinder bore 2. Ring 3 incorporates annular space 6 communicating with cylinder 8 through a plurality of ports 7.

Said ports are positioned such that they are covered by piston 9 during the final part of its upward travel. Said ports are made to direct their discharge radially into the cylinder or, in alternative embodiments, are angled such that their collective discharge produces a v rtex' within the cylinder or is directed upward or downward.

In another embodiment, annular space 6 is positioned high up in a single ring 3, permitting discharge ports 7 to take the form of narrow channels in the upper surface of the said ring, said channels being closed by the lower surface of cylinder head 4. In the preferred embodiment, annular space 6 is made more or less toroidal with ports 7 positioned more or less tangential to its upper edge. In other embodiments, the said annular space is made with other cross-sectional shapes. In a further embodiment, one or more additional rings 3 are provided in the upper cylinder bore, each incorporating an annular space 6 and ports 7.

The bore and stroke dimensions of the engine are made to suit the desired duty characteristics of the engine and the number and volume of the said annular spaces. Depending upon the size and desired duty characteristics of the engine, the dimensions of ports 7 are altered to permit combustion to occur within the said annular space or spaces or to ensure that quenching effects prevent combustion from occurring therein.

In engines producing high torque, ports 7 are deleted from the cylinder bore thrust face, or are made smaller with wider bearing surfaces between them. In operation, during the compression stroke, mixture is forced through ports 7 into annular space 6 and is trapped by piston 9 closing off the said ports during its final upward travel. During the firing stroke and after completion of the primary combustion event, the said ports are uncovered releasing the compressed mixture to prolong the secondary combustion event. In an alternative embodiment, as piston 9 uncovers ports 7, combustion extends to annular space 6, resulting in jets of combustion products entering cylinder 8, said combustion products serving to prolong- the secondary combustion event.

Claims

CLAIMS ;

1. In an internal combustion engine having at least one cylinder in a cylinder block with a piston reciprocable therein and a cylinder head closing an upper end of the or each of said cylinders, an improvement comprising the provision of at least one recess in a wall of the or each of the said cylinders adjacent said cylinder head forming a chamber or chambers adapted to receive combustible charge materials from the cylinder adjacent thereto through a restricted access opening or openings, said access opening or openings being opened or closed by passage of the piston within the cylinder.

2. The improvement according to claim 1 wherein a single said chamber is provided in the form of a peripheral cavity surrounding each said cylinder with a plurality of access openings leading to said cylinder from said peripheral cavity.

3. The improvement according to claim 2 wherein said peripheral cavity is toroidal in configuration.

4. The improvement according to claim 2 wherein said peripheral cavity is arranged as an annular groove opening onto a parting face between said cylinder block and said cylinder head.

5. The improvement according to claim 4 wherein said openings are formed by circu ferentially located recesses opening onto said parting face and extending between each said cylinder and its associated said peripheral cavity.

6. The improvement according to any one of claims 1 to 5 wherein said chambers and said access opening or openings are formed in an annular insert arranged in a corresponding annular recess in the cylinder wall adjacent said cylinder head.

7. The improvement according to any one of claims 1 to 6 wherein said access opening or openings is/are shaped and configured to create vortex flow conditions within the adjacent cylinder.