The present invention relates in general to a device for accelerating gas flows.

More particularly, the subject of the invention is a simple, economical and compact accelerator device which can be used in an extremely advantageous manner to improve the operating characteristics of an internal combustion engine for motor vehicles, and which uses the kinetic or wave energy of the combustion residues in exhaust systems or of the inducted air in inlet systems for such engines.

The gas-flow acceleration device according to the invention is characterised in that it comprises a hollow body having a tubular inlet connector and a coaxial tubular outlet connector interconnected by an intermediate expansion chamber defined by a prismatic casing with a quadrilateral cross-section constituted by two flat base walls which are parallel and generally rhomboidal in shape, of which the edges extending between the inlet and outlet connectors are each defined by two straight sides at an angle to each other, and by two pairs of substantially flat side walls which interconnect the corresponding pairs of straight sides of the base walls and define two opposing lateral corners in correspondence with the said angles, the inlet and outlet connectors having outer ends of circular cross-section and inner ends of a quadrilateral cross-section complementary to that of the respective connecting parts of the prismatic casing.

The inlet and outlet connectors conveniently form respective Venturi constrictions with the connecting parts of the prismatic casing.

Preferably, the device also includes a flow separator disposed coaxially in correspondence with the inner quadrilateral end of at least one of the inlet and outlet connectors.

The prismatic casing may have different geometric conformations according to whether the accelerator device according to the invention is intended for application to an exhaust system or to an inlet system of an internal combustion engine.

The advantages derived from the accelerating action achieved by virtue of the conformation of the device according to the invention lie in an appreciable improvement in the operating characteristics of the engine to which the device is applied, in terms of an increase in torque and power and a reduction in fuel consumption and pollution, due on the one hand to improved removal of the combustion residues and on the other hand to an improved quantity of charge.

The invention will now be described in detail with reference to the appended drawings, provided purely by way of non-limiting example, in which:

Figure 1 is a perspective view of a gas-flow accelerator device according to one embodiment of the invention.

Figure 2 is a longitudinal section taken o the line II-II of Figure 1,

Figure 3 is an exploded perspective view of Figure 1,

Figure 4 is a view similar to Figure 2 illustrating a first variant of the device according to the invention.

Figure 5 is an exploded perspective view of a detail of Figure 4,

Figure 6 is a longitudinal section illustrating a second variant of the device, and

Figure 7 is a schematic view illustrating the manner of use of•the device according to the invention.

With reference initially to Figures 1 to 3, a gas-flow accelerator device according to the _„ invention is generally indicated 10 and is constituted by a hollow body formed essentially by a tubular inlet connector 12 and a coaxial tubular outlet connector 14 interconnected by a prismatic casing 16 which defines an expansion chamber 18 between the two connectors 12 and 14.

The prismatic casing 16 has a quadrilateral cross- section defined hy two flat, parallel base walls 20 of generally rhomboidal shape and two angled side walls 22 which join the base walls 20.

Each base wall 20 is defined laterally by two edges extending between the connectors 12, 14 and each

defined by two straight sides 20a, 20b at an angle A to each other.' In the embodiment of Figures 1 to 3, the angles A are between 55° and 65° and the sides 20a are longer than the sides 20b , being approximately twice their length.

The two base walls 20 have respective longitudinal extensions 20c, 20d in correspondence with the free ends of the sides 20a and 20b, and also have edges 20e bent perpendicular to their planes and extending along the sides 20a, 20b between the extensions 20c, 20d.

The bent edges 20e are used for connection to the two side walls 22, each of which is generally L-shaped and is defined by two substantially flat faces 22a, 22b with a shape corresponding to that of the sides 20a, 20b of the base walls 20. The longitudinal edges of the walls 22 are connected permanently to the bent parts 20e by any suitable means, for example by welding.

The two side walls 22 define two corners 22c at the junction of the two sides 20a, 20b where the section of the prismatic casing 16 is greatest. In the configuration of Figures 1 to 3, the ratio between the width of the casing 16 in correspondence with this section, indicated B, and that in correspondence with the extensions 20c, 20d (that is in the zones of union with the tubular connectors 12, 14), indicated C, is between 2.5:1 and 3.5:1.

Each of the connectors 12 and 14 includes a respective outer cylindrical end 12a, 14a of circular section and an inner end 12b, 14b deformed so as to have a

quadrilateral cross-section complementary to that of the extensions 20c, 20d of the casing 16. These inner ends 12b, 14b are fixed permanently to the extensions 20c, 20d and to the corresponding zones of the side walls 22 by any suitable means, for example by welding.

Longitudinal slots 12c, 14c are formed in the end parts of the outer ends 12a, 14a in order to allow the connectors 12 and 14 to be fixed to two tubes in use, for the purposes which will be clarified below, by means of tube collars or clips of conventional type.

As will be apparent from Figure 2, the shape of the ends 12b and 14b of the connectors 12, 14 and of the corresponding ends of the prismatic casing 16 is such that two Venturi constrictions, indicated 24 and 26, the widths of which are obviously those indicated C, are formed in correspondence with the zones of connection between these elements, in practice.

In correspondence with the Venturi throat 24 is a flow separator constituted, in the case of Figures 1 to 3, by two mutually-parallel quadrilateral plates 28 which are spaced apart and extend perpendicular to the planes of the faces 20 of the casing 16. The two plates 28 are normally fixed within the part 12b of the inlet connector 12 by welding.

The variant of the device shown in Figures 4 and 5 is generally similar to the embodiment described above, and only the differences will be described in detail with the use of the same reference numerals for identical or similar parts.

In this variant, the flow separator associated with the Venturi neck 24 is constituted by a circular-sectioned tube 30 provided with two radial tabs 32 for its fixing, by welding, within the part 12b of the inlet connector 12, coaxially therewith.

It should be noted that a flow separator similar to that of Figures 1 to 3 or that of Figures 4 and 5 could also be provided in correspondence with the outlet Venturi neck 26.

The variant of the device illustrated in Figure 6, and generally indicated 11, differs from the embodiment of Figures 1 to 3 (the reference numerals of which are used for identical or similar parts) mainly in a different geometric configuration of the prismatic casing 16. In this case, in fact, the casing 16 has a symmetrical form derived from the fact that the sides 20a and 20b of the base walls 20 have the same length, the angle A between them being between 110° and 130°. In this case, the ratio between the width B and the width C measured in correspondence with the corners 22c and the Venturi necks 24 and 26 respectively is between 2.5:1 and 3.5:1.

Furthermore, in this case, two flow separator plates 28 are provided in correspondence with both the Venturi necks 24 and 26.

The device according to the invention is useable to advantage for accelerating inlet and exhaust flows in an internal combustion engine for motor vehicles. In particular, the embodiment of the device shown in Figures 1 to 5 is particularly suited for application

to the exhaust system while that of Figure 6 is more suitable for application to the inlet system.

The installation of the device is shown by way of example in Figure 7, in which an internal combustion engine of a motor vehicle, schematically indicated M, has a gas exhaust pipe E terminating in a silencer S,and an air intake duct I associated with an air filter F.

The device 10 according to Figures 1 to 3 or 4 and 5 is mounted in the exhaust pipe E upstream of the silencer S with its inlet connector 12 facing the engine M, while the device 11 according to the embodiment of Figure 6 is mounted in the intake duct I downstream of the filter F.

It should be noted that the assembled position of the devices 10 and 11 could differ from that illustrated: in particular, the device 11 could also be mounted upstream of the air filter F.

In operation, the devices 10 and 11 accelerate the flow of gas which passes through them (exhaust gas and inducted air respectively) using the kinetic energy or wave energy.

Experimental tests carried out by the Applicants have allowed them to ascertain that the action of the device according to the invention surprisingly allows the operating characteristics of the engine using it to be improved appreciably: in fact they have been able to note considerable increases in power and torque together with a considerable reduction in fuel consumption and

pol lution .

These improvements have been found both in the case of carburrettor engines and in the case of injection engines, even when provided with turbo-compressors.

It should also be noted that the device according to the invention may be applied with equal advantage to exhaust pipes for combustion products from boilers and similar heating apparatus.

Naturally, the constructional details and forms of embodiment of the device may be varied widely with respect to that described and illustrated, without thereby departing from the scope of the present invention as defined by the following claims.