GB2232201A

GB2232201A - Adjustable swirl i.c. engine intake duct

Info

Publication number: GB2232201A
Application number: GB8911543A
Authority: GB
Inventors: Andreatta Bruno; Puglisi Alfio
Original assignee: Fiat Auto SpA
Current assignee: Fiat Auto SpA
Priority date: 1989-05-19
Filing date: 1989-05-19
Publication date: 1990-12-05
Anticipated expiration: 2009-05-19
Also published as: GB2232201B; GB8911543D0

Abstract

A supplementary duct 13 contains a movable flexible steel strip 14 which variably protrudes into the intake duct 10 immediately upstream of the valve spiral 11. The strip 14 position may vary dependent upon engine load and speed. <IMAGE>

Description

An improved internal combustion engine with adjustable turbulance of intake *** The invention relates to an improved high-turbulence internal combustion engine, more particularly of the direct-injection high-speed diesel kind, having intake ducts provided with means for adjusting the turbulence of the flow of air supplying the engine depending on the operating conditions thereof.

As is known, in internal combustion engines1 more particularly in direct-injection diesel engines having a low cylinder capacity, it is particularly important to supply air having the right degree of turbulence, in order to obtain a uniform mixture of air and fuel.

There are numerous known devices for obtaining this end, e.g. the use of spiral intake ducts. These systems, which are well known to the skilled addressee, are used to obtain turbulence at a value which periodically optimises the combustion conditions at various rotation conditions of the engine. Basically, the aforementioned conditions obtain ideal turbulence only over a restricted range of use of the engine, whereas if the engine operating conditions are varied outside the aforementioned range the turbulence does not match the required characteristics of the engine.Other devices such as sending a jet of compressed secondary air at a tangent to the supply spiral in order to vary the range of motion and consequently the turbulence of the intaken air, or the expedient of disposing inflatable members inside the supply duct so as to vary its geometry in dependence on the operating conditions of the engine, are far from solving the problem of ensuring the proper turbulence of intaken air under all conditions since, for example, supplementary air systems have relatively short ranges of adjustment and in any case require the availability of a source of compressed air, and on the other hand it is difficult accurately to control the geometry of the intake duct by using inflatable members.It is desirable to construct an internal combustion engine comprising intake means capable of producing high turbulence in the air flow supplying the engine and to adapt the turbulence to the optimum value for the various end operating end load conditions of the engine.

The invention provides an internal combustion engine, comprising at least one combustion chamber. at least one inlet duct or intake pipe and at least one corresponding supply duct (which may have a spiral axis) connecting the inlet duct to an inlet or suction aperture in the combustion chamber, and for each supply duct it comprises an element (which may be in the form of a flexible strip) movably disposed inside a supplementary duct opening into the supply duct at a connection zone between the supply duct and the inlet duct, and means for selectively positioning the element so that it partially protrudes into the connecting zone and can thus to a varying extent choke the flow cross-section of the inlet duct.

For a better understanding of the invention there follows a non-limitative description of an embodiment thereof with reference to the accompanying drawing, which is a simplified diagramatic plan view, partly in section, of an internal combustion engine constructed according to the invention.

The drawing shows an internal combustion engine (general reference 1) of any known kind, i.e. in the present case a direct-injection high-speed diesel engine: for simplicity the drawing shows only an engine block 2 and part of a cylinder head 3 above, shown in section. The engine block 2 comprises at least one cylinder 4. the interior of which defines a combustion chamber 5 closed at the top by a cylinder head 3 and formed with various intake and exhaust openings 7, 8 adapted to be closed by respective valves, which are known and omitted for simplicity and are movable e.g.

across respective seats 9 formed in cylinder head 3 opposite the apertures 7 and 9 (for simplicity the drawing shows only the seat 9 formed opposite aperture 7). Engine 1 can comprise one or more combustion chambers 5 of the aforementioned kind, and the cylinder head 3, for each chamber 5, comprises a respective exhaust duct (of known kind and omitted for simplicity) and an intake duct 10 ending tangentally in a supply spiral 11 of known kind, formed in the cylinder head 3 in a position above the aperture 7 so as hydraulically to connect duct 10 with the aperture 7. More particulary the duct 10, which is adapted to be tangentally connected to spiral 11, is curved and has the opposite radius of curvature to the spiral 11, so that a flow of intake air 12 is forced to enter the suction aperture 7 after travelling along a substantially S-shaped trajectory.

According to the invention, at least one supplementary duct 13 for each combustion chamber 5 is also formed inside the cylinder head 3 and is disposed substantially parallel to the duct 10 and is likewise curved so as to open tangentally into the spiral 11, more particularly opposite a connection zone 15 between the spiral 11 and the duct 10; the supplementary duct 13 describes a curve having a wide range of curvature and is formed from part of an outer-surface side 16 of duct 10 so as to open substantially parallel to a corresponding inner-surface side 18 of spiral 11.

According to the invention, a flexible strip 14 is movably disposed inside the supplementary duct 13, and is resilientally deformable and made preferably of piano-wire steel and/or any other self-lubricating synthetic plastic material adapted to withstand the operating temperatures in duct 10 and spiral 11. Strip 14 is longer than duct 13 so that its opposite ends 19, 20 extend out of and protrude into the duct at the prospective opposite ends thereof. EM extends from duct 13 substantially opposite the mouth of duct 10 and is connected to diving means adapted to vary the axial position of strip 14 inside duct 13.The means comprise e.g. an actuator 21 of any known kind controlled by a switchboard 22 in dependence on the rotation and load conditions of engine 1 as detected by one or more sensors 13 which are also of known kind and are therefore for simplicity not however described. The opposite end 20 of strip 14 opens into the aformentioned zone 15 substantially behind the inner surface 18 of spiral 11 as substantially an extension of the cross-section of the outer surface 16 of duct 10.

Depending on the axial position of strip 14, which is controlled by switchboard 22 via the actuator 21, the end 20 is adapted selectively inside the connecting zone 15 to assume a number of operating positions in which the strip 13 chokes to a varying extent the flow section available in the intake pipe 10 for the airflow 12.

Basically the strip 14 is moved along duct 13 in the direction of the arrows by actuator 21 and is adapted to vary the cross-section of duct 10 as required, so as in all cases to obtain an optimum connection to spiral 11 and vary the cross-section precisely at the connecting zone 15, which is particularly critical with regard to bringing about the ranges of motion which determine the degree of turbulence which can be reached by the airflow 12 on entering the aperture 7.

The engine 1 constructed according to the invention operates as follows. During the intake phase (or when apperture 7 is open) the air supply flow 12 is mainly intaken through duct 10, any air drawn through duct 13 being completely irrelevant. The air intaken through 10 enters spiral 11 and, owing the geometry thereof, rotates in accordance with the cross-section of spiral 11 so as to generate the required turbulence before the charge of air is introduced through apperture 7 into the combustion chamber 10 so as to assist in spraying the charge of fuel which is subsequently injected into the combustion chamber 5. It is clear that the turbulence acquired by the airflow 12 once introduced into the spiral 11 depends on the speed of entry thereof into the spiral 11, which clearly depends on the size and orientation of the minimum flow section available to the airflow 12.It is therefore clear that if a varying portion of strip 14 overhangs. depending on the axial position of the strip in duct 13, inside the joining zone to the connection 15, the result is that the speed of entry of air into the spiral 11 is indirectly higher and directed tangentally in proportion as the end 20 of strip 14 projects and overhangs from duct 13. This increases the momentum of the air in spiral 11 and consequently helps to maintain higher turbulence than if the strip 14 was in the retracted position or if end 20 was completely inserted into duct 13.Consequently, depending on the operating conditions of the engine (e.g. speed of rotation of the driving shaft) as detected by the sensor or sensors 23, the switchboard 22 is adapted to control the actuator 21 so as periodically to bring the strip 14 into an axial position such that the end part 20 overhangs to a varying extent outside duct 13 so as to vary the geometry and the cross-section of duct 10 as required and in controlled manner at the connecting zone 15, and adjust then to the optimum values for the particular operating condition of the engine 1 as detected by sensors 23.

Basically, the duct 13 and corresponding moving strip 14 as described herein before are a simple, economic and highly efficient method of obtaining a variable-geometry cross-section of the intake duct 10, and of optimising, under any operating conditions on engine 1, the turbulence of the flow of suction air 12 so that in all cases, both at low and other operating conditions of the engine 1, the turbulence is better than that obtainable in engines of known kind but without a duct 13 and strip 14. Clearly, whatever the axial position of strip 14 inside duct 10, there was always a restriction in the flow section of duct 10 and consequently an increase in the air speed entering the spiral 11 and a consequent increase in turbulence.

Also, according to another feature of the invention, strip 14 can be moved so as only to vary the geometry of the appropriate zone for varying the turbulence of the airflow at the inlet 12, the valuation being highly reproducable while maintanining unaltered the overall geometry of the intake duct 10.

Finally, of course, the preceding description can be varied and modified without thereby departing from the scope of the invention.

Claims

1. An internal combustion engine, comprising at least one combustion chamber, at least one inlet duct and at least one corresponding supply duct connecting the inlet duct to an inlet aperture in the combustion chamber, and for each supply duct it comprises an element movably disposed inside a supplementary duct opening into the supply duct at a connection zone between the supply duct and the inlet duct, and means for selectively positioning the element so that it partially protrudes into the connecting zone and can thus to a varying extent choke the flow cross-section of the inlet duct.

2 An engine according to Claim 1, wherein the supply duct is curved.

3 An engine according to Claim 2, wherein the axis of the supply duct is a spiral

4. An engine according to Claim 2 or 3, wherein the supplementary duct in which the element moves opens into the connecting zone at a tangent to the wall of the supply duct.

5. An engine according to any of the preceding Claims.

wherein the means for selectively positioning the element inside the supplementary duct comprise an actuator connected to an end of the element remote from the connecting zone, and at least one sensor that senses the operating conditions of the engine and which sensor is adapted to control the actuator.

6. An engine according to any of the preceding Claims, wherein the element is a strip.

7. An engine according to any of the preceding Claims, wherein the element is flexible.

8. An engine according to Claim 7, characterised in that the element is made of piano-wire steel.

9. An engine according to any of the preceding Claims, characterised in that the supplementary duct is integrally formed in part of a side of an outer surface of the inlet duct, which like the supplementary duct is curved.

10. An internal combustion engine, substantially as herein described with reference to the accompanying drawing.