GB2064085A

GB2064085A - Cooling device for the supercharging air of an internal combustion engine

Info

Publication number: GB2064085A
Application number: GB8036690A
Authority: GB
Original assignee: Centro Ricerche Fiat SCpA
Current assignee: Centro Ricerche Fiat SCpA
Priority date: 1979-11-28
Filing date: 1980-11-14
Publication date: 1981-06-10
Also published as: FR2470858A1; DE3043513A1; IT7969296A0; IT1119516B

Abstract

A heat exchanger 11 for the cooling of compressed supercharged air of an I.C. engine comprises a regenerative matrix rotor 56 rotatably mounted in a chamber (formed e.g. of two half-shells 18, 19) having therein opposed surfaces in which are formed two pairs of apertures (viz 30,31 and 32, 33) respectively conveying cooling air and compressed air to and from the matrix for heat exchange therein, sealing means being provided between the rotor and said surfaces. The sealing means may comprise pads 62 pressed against the rotor end faces by resilient gaskets 65 (e.g. of rubber tubing) which may be open ended or filled with compressed air. The rotor may be rotated by an electric or hydraulic motor or by a turbine driven by the engine exhaust. In a unit (e.g. Figs. 1 & 2) comprising an I.C. engine (1) and a compressor-turbine unit (4-7) operated by the engine exhaust gas in order to feed compressed air to the intake manifold (2) of the engine, the compressed air leaving the compressor (4) is cooled by said air- to-air heat exchanger (11). <IMAGE>

Description

SPECIFICATION Cooling device for the supercharging air of an internal combustion engine This invention relates to a cooling device for the supercharging air of an internal combustion engine, in particular an engine for motor vehicles.

In supercharged Diesel or Otto engines, it is always advantageous to cool the supercharging air, firstly because due to the fact that the air density increases as its temperature decreases, more fuel can be fed to the engine the lower the air temperature, for equal pressures, and secondly because the operating temperatures to which the constituent materials of said supercharged engines are subjected are greater the greater the supercharging air temperature. In other words, in supercharged internal combustion engines, the delivered power and reliability normally increase as the supercharging air temperature decreases, at least within a certain range.

For the aforesaid reasons, supercharged internal combustion engines used in fixed installations are normally fed with compressed air which is cooled in water radiators which, because of their poor efficiency, are generally bulky and are poorly suitable for use in engines for vehicles, in particular motor vehicles.

The object of the present invention is to provide a cooling device for the supercharging air of an internal combustion engine, which has a relatively high efficiency and is sufficiently compact to be easily mounted in a motor vehicle.

Said object is attained according to the present invention by a cooling device for the supercharging air of an internal combustion engine, characterised by comprising a chamber, two first apertures for the compressed supercharging air for said engine which are disposed facing each other and provided in a first portion of two opposing surface of said chamber, two second apertures for countercurrent cooling air for said compressed air which are disposed facing each other and provided in a second portion of said two opposing surfaces of said chamber, a rotating air-air heat exchanger mounted in said chamber and comprising a disc rotatable about an axis substantially perpendicular to said two surfaces, said disc being disposed between said two first apertures and between said two second apertures, and air sealing means disposed between said disc and said two surfaces to prevent communication between either of said first apertures and either of said second apertures.

The present invention also relates to a supercharged engine unit, particularly for motor vehicles, of the type comprising an internal combustion engine, a turbine drivable by the exhaust gas of said engine, a compressor driven by said turbine and disposed in the intake circuit of said engine, and a cooling device as described in the preceding paragraph; one of said first apertures being connected to the outlet of said compressor, and the other of said first apertures being connected to the intake manifold of said engine.

Further characteristics and advantages of the present invention will be apparent from the description given hereinafter with reference to the accompanying drawings, which iliustrate a nonlimiting embodiment thereof, and in which: Figures 1 and 2 are two block diagrams each relative to a supercharged engine unit incorporating a cooling device constructed according to the present invention; Figure 3 is a sectional diagrammatic view of a preferred embodiment of the cooling device of the present invention; Figure 4 is a section on the line IV--IV of Figure 3; Figure 5 is a section through a detail of Figure 3 to an enlarged scale; and Figure 6 is a section through a modification of the detail of Figure 5 to an enlarged scale.

In Figures 1 and 2, the reference numeral 1 indicates an internal combustion engine, to the intake manifold 2 of which compressed air is fed by way of a conduit 3 connected to the outlet of a compressor 4, the inlet of which is connected to an air intake 5. The rotor of the compressor 4 is keyed on to a shaft 6, rotated by a turbine 7, the inlet of which is connected to the exhaust manifold 8 of the engine 1 by means of a conduit 9, and the outlet of which, indicated by 10, discharges to atmosphere.

The conduit 3 traverses a cooling device, indicated overall by 11, in which heat is transferred between the compressed air leaving the compressor 4 and a stream of relatively cold air flowing along a conduit 12 through the device 11 in the opposite direction to the compressed air.

The conduit 12 extends between an air intake 1 3 disposed upstream of the device 11, and an exhaust member 14, by way of an ejector 1 5 disposed downstream of the device 11 and operated by gas fed into its restricted section.

Whereas in the diagram of Figure 1 the gas operating the ejector 1 5 is fed from the outlet 10 of the turbine 7, in the diagram of Figure 2 said gas is fed to the ejector 1 5 through a conduit 1 6 provided with a control valve 1 7 and extending between a point on the conduit 7 and the restricted section of the ejector 1 5. In this manner, it is possible to advantageously use the otherwise dissipated waste gate flow which in supercharged engines, and in particular supercharged automobile engines, bypasses the turbine in order to limit the compression ratio at high rotational speeds.Because the waste gate flow is substantially zero at low rotational speeds of the engine 1 it is advantageous to leave the valve 1 7 slightly open even at low rotational speeds, in order to create a small waste gate flow which, even though not required for proper operation of the engine, is however necessary in order to maintain a cooling air flow through the device 11.

According to one modification, not shown, the conduit 1 6 discharges to atmosphere, and the ejector 1 5 is replaced by a fan driven by the engine 1 or by another similar device connected into the conduit 12.

As shown in particular in Figure 3, the cooling device 11 comprises two half shells 18 and 19 which are rigidly joined together and define an inner chamber 20 bounded externally by a cylindrical surface 21 and by two parallel end surfaces 22 and 23 perpendicular to the axis of the surface 21.

As shown in particular in Figure 4, each surface 22, 23 (of which only the surface 23 is shown) comprises a peripheral circumferential strip 24 and a substantially circular central zone 25 connected together by two radial strips 26 and 27 which are of circular arc configuration and define, on the strip 24, two portions of which the first, indicated by 28, subtends an angle at the centre which is greater than 1800, whereas the second, indicated by 29, subtends an angle at the centre which is less than 1800.

The strips 26 and 27 and the portions 28 and 29 define on the surfaces 22 and 23 two pairs of apertures 30, 31 and 32, 33, of which the first are.

mutually facing and equal to each other, and are bounded externally by the portions 28, and the second two are mutually facing and equal to each other and are bounded externally by the portions 29.

The two half shells 1 8 and 19 comprise a first pair of tubular connectors 34 and 35 which extend in opposite directions from the apertures 30 and 31 in order to connect the chamber 20 to two portions of the conduit 12 (Figures 1 and 2), and a second pair of tubular connectors 36 and 37 which extend in opposite directions from the apertures 32 and 33 in order to connect the chamber 20 to two portions of the conduit 3 (Figures 1 and 2).

Each of the half shells 1 8 and 19 comprises a central portion internally bounded by the central zone 25 of the respective surface 22, 23, and constituting a hub 38 comprising a central through bore 39, through which the end of a shaft 41 is rotatably mounted by way of a radial bearing 40. The ends of this shaft are in the form of two threaded axial sterns 42 engaged by respective ring nuts 43 provided with respective tubular distance pieces 44, while the intermediate portion of this shaft extends through a central tubular support 45 of a rotating air-air heat exchanger housed in the chamber 20 and indicated overall by46.

By tightening one of the ring nuts 43 it is possible to lock the inner race of the relative bearing 40 against a fixed stop ring 47 carried by the shaft 41, whereas by tightening the other ring nut 43 it is possible to lock together the ring 47, the tubular support 45, the inner race of the other bearing 40 and a stop ring 48 mounted slidable on the shaft 41 between said bearing 40 and one end of the tubular support 45.

The half shell 18 comprises an outer tubular appendix 49 coaxial to the shaft 41 and having connected to its free end, by means of a plurality of screws 50, a connection flange 51 for a drive device, illustrated diagrammatically in Figure 3 and indicated by 52, which comprises an exit shaft 53 connected to the shaft 42 by means of a coupling 54.

The device 52 can be constituted by a low power electric motor, for example an electric motor normally used for windscreen wipers, or a small hydraulic motor connected to the lubrication circuit of the engine 1, or again a turbine device fed by the exhaust gas of the engine 1 in series or in parallel with the turbine 7.

In addition to the tubular support 45, the rotating heat exchanger 46 comprises an outer cylindrical ring 55, which in the limit can also be dispensed with, and an intermediate perforated cylindrical disc or matrix 56 defining a plurality of axial channels 57 disposed parallel to the axis of the shaft 41. In particular, as shown in Figure 4, the channels 57 are defined by means of a sheet metal strip 58 wound in a spiral and supporting a strip 59 of corrugated sheet metal. Alternatively, according to a further embodiment shown in Figure 4, the channels 57 are defined by a plurality of sheet metal strips 60 extending outwards from the support 54 in the form of spirals, and each supporting a respective strip 61 of corrugated sheet metal.

In order to prevent communication between one or other of the apertures 30 and 31 on one side and one or other of the apertures 32 and 33 on the other side, the rotating heat exchanger 46 cooperates in an airtight manner with each of the surfaces 22 and 23 by way of a pad 62, of which a first portion, indicated by 63, extends as an arc along the entire portion 28 of the strip 25, and a second portion, indicated by 64, extends as a ring along the portion 29 of the strip 24 and along the strips 26 and 27.

Each pad portion 62 is kept in contact with the respective end surface of the matrix 56 by a resilient gasket 65 compressed between the relative portion 63 and the relative surface 22, 23, and constituted in the example illustrated by a tubular element of rubber or other similar material open at its ends.

In contrast, each pad portion 64 is kept in contact with the relative end surface of the matrix 56 by means of an endless resilient gasket 66 compressed between a flat surface 67 of the relative portion 64 and the relative surface 22, 23.

In the example illustrated, the gasket 66 is constituted by a tubular element of rubber or other like material filled with compressed air.

When in operation, the device 52 rotates the shaft 41 (in the anti-clockwise direction in Figure 4), and thus rotates the cylindrical matrix 56 inside the chamber 20. The matrix intercepts a first air stream which is drawn in through the air intake 5 at ambient temperature and atmospheric pressure, is compressed in the compressor 4 to the pressure required for supercharging the engine 1, and is heated by the effect of the compression to a temperature of about 1 1 OOC. This compressed air stream is fed by the compressor 4 to the connector 37 by way of a first portion of the conduit 3, and reaches the connector 36 by flowing through the channels 57 of the matrix 56.

Inside this latter, because of the large surface area of the channels 57 which at any moment are aligned with the aperture 33, the compressed air arriving from the connector 37 gives up heat to the sheet metal portions which define the channels 57, and reaches the aperture 32 and connector 36 at a temperature of about 500C, to then be fed at this temperature to the engine 1 through a second portion of the conduit 3 and manifold 2.

That part of the matrix 56 heated by the effect of the passage of compressed air from the connector 37 is moved by rotation of the shaft 41 to a position corresponding with that part of the chamber 20 disposed between the apertures 30 and 31 where it is struck by an air stream drawn in at ambient temperature and atmospheric pressure through the air intake 1 3 and fed to the connector 34 through a first portion of the conduit 12.The air fed to the connector 34 has an average temperature of between 250 and 300 C, and as it flows through the matrix 56 in the opposite direction to that of the compressed air from the connector 37, it removes heat from the sheet metal portions defining the channels 57 and gradually heats up before leaving through the aperture 31 and connector 35 to a temperature slightly less than the temperature of the outlet air from the compressor 4.

The pad portions 64 and resilient gaskets 66 disposed along the periphery of the apertures 32 and 33 prevent the compressed air from the connector 37 bypassing the matrix 56 and/or mixing with the air from the connector 34. This is because as the gaskets 66 are constituted by air chambers which are inflated to a pressure normally greater than the pressure of the compressed air fed by the compressor 4, they prevent the relative pad portions 64 from moving away from the end surface of the matrix 56. Both the resilience of the gaskets 66 and the gas pressure acting on the surface 67 (Figure 5) of the pads 62 cooperate in this action.

The thrust exerted by each gasket 66 on the relative pad portion 64 is not sufficient by itself to ensure that the contact pressure between the portion 64 and matrix 56 is substantially constant at all points of the portion 64, because of the presence of the strips 26 and 27. In this respect, with reference to Figure 4 it can be seen that the channels 57 which arrive in a position below that branch of each pad portion 64 extending along the respective strip 27 by virtue of the rotation (anticlockwise in Figure 4) of the matrix 56, are full of (cooling) air at atmospheric pressure, and would therefore receive compressed air only after passing said branch of the pad portion 64.In contrast, the channels 57 which arrive in a position below that branch of each pad portion 64 extending along the respective strip 26 are full of compressed air and would therefore receive air at atmospheric pressure only after passing said branch of the pad portion 64.

Because of this, the pad portions 64 would tend to push against the matrix 56 at the strips 27, and to "float" on the matrix 56 at the strips 26. In order to prevent such a drawback, each pad 62 is provided with two grooves 68 which each communicate by way of a plurality of transverse grooves 69 with that part of the chamber 20 disposed downstream of the relative strip 26,27 in the direction of rotation of the matrix 56.

The purpose of the pad portions 63 and gaskets 65 is to prevent the cooling air bypassing the matrix 56. However, in this case it should be noted that as the cooling air is at atmospheric pressure, not only can the necessary seal be ensured by the resilience of the gaskets 65 alone, which are open at their ends and do not contain compressed air, but in addition the gasket 65 and relative pad portion 63 disposed along the periphery of the aperture 31 can also be dispensed with.

In the modification shown in Figure 6, each gasket 66 comprises at least one lateral bore 70 through which the compressed air from the compressor 4 penetrates into the gasket 66 to exert a pressure over a larger area of the relative pad portion 64.

Numerous modifications can be made to the preferred embodiment described without leaving the scope of the present invention. In particular, the metal matrix 56 could be replaced by a ceramic matrix (not shown) of known type, and the drive device 52 could instead of the described device be constituted by any low-cost, low-power motor bearing in mind that the resistant power applied to the shaft 42 is extremely low because of the relatively low rotational speed of the heat exchanger 46, and under normai working conditions is due almost entirely to the friction between the matrix 56 and pads 62.

Claims

1. A cooling device for the supercharging air of an internal combustion engine, characterised by comprising a chamber, two first apertures for the compressed supercharging air for said engine which are disposed facing each other and provided in a first portion of two opposing surfaces of said chamber, two second apertures for countercurrent cooling air for said compressed air which are disposed facing each other and provided in a second portion of said two opposing surfaces of said chamber, a rotating air-air heat exchanger mounted in said chamber and comprising a disc rotatable about an axis substantially perpendicular to said two surfaces, said disc being disposed between said two first apertures and between said two second apertures, and air sealing means disposed between said disc and said two surfaces to prevent communication between either of said first apertures and either of said second apertures.

2. A device as claimed in claim 1, characterised by comprising drive means for rotating said disc about said axis.

3. A device as claimed in claim 2, characterised in that said drive means comprise an electric motor.

4. A device as claimed in claim 2, characterised in that said drive means comprise a hydraulic motor connected to the lubrication circuit of said internal combustion engine.

5. A device as claimed in claim 2, characterised in that said drive means comprise turbine means.

6. A device as claimed in any one of the preceding claims, characterised in that said sealing means comprise, for each of said first apertures, a pad slidably coupled to said disc and disposed between this latter and that surface of said chamber in which said first aperture is provided, said pad surrounding said first aperture and being coupled to the relative surface of said chamber by way of resilient seal means.

7. A device as claimed in any one of the preceding claims, characterised in that said seal means comprise, for at least that of said two second apertures which is disposed upstream of said disc in the direction of movement of said cooling air, a pad slidably coupled to said disc and disposed between this latter and that surface of said chamber in which said second aperture is provided, said pad extending along at least part of the perimeter of said second aperture and being coupled to the relative surface of said chamber by way of resilient seal means.

8. A device as claimed in claim 6 or 7, characterised in that said resilient seal means comprise a tubular element constituted of elastomer material.

9. A device as claimed in claim 8, characterised in that said tubular element has its two opposing ends open.

10. A device as claimed in claim 8, characterised in that said tubular element has its two opposing ends closed.

11. A device as claimed in claim 8, characterised in that said tubular element is endless.

12. A device as claimed in claim 10 or 11, characterised in that fluid is present under pressure in said tubular element.

13. A device as claimed in claim 10 or 11, characterised in that said element comprises at least one lateral bore which connects the interior of said tubular element to said first apertures.

14. A device as claimed in any one of claims 6 to 13, characterised in that each of said pads comprises two radial portions, each of which comprises, on the side facing said disc, a central groove which communicates with that aperture of the two said first and second apertures which is disposed downstream of the relative radial portion in the direction of rotation of said disc.

1 5. A supercharged engine unit, particularly for motor vehicles, of the type comprising an internal combustion engine, a turbine drivabie by the exhaust gas of said engine, and a compressor driven by said turbine and disposed in the intake circuit of said engine, characterised by compnsing a cooling device as claimed in any one of the preceding claims, one of said first apertures being connected to the outlet of said compressor, and the other of said first apertures being connected to the intake manifold of said engine.

16. An engine unit as claimed in claim 15, characterised by comprising an air suction device operated by said exhaust gas, one of said second apertures being connected to atmosphere and the other of said second apertures being connected to said suction device.

17. An engine unit as claimed in claim 16, characterised in that said suction device comprises an ejector with two inlets, the first of which communicates with said other second aperture, and the second of which is arranged to receive at least part of said exhaust gas.

18. An engine unit as claimed in claim 17, characterised in that said second inlet is connected to the discharge of said turbine.

19. An engine unit as claimed in claim 17, characterised in that said second inlet is connected to the waste gate gas discharge of said turbine.

20. A supercharged engine unit substantially as described with reference to any one of the accompanying figures.