DEVICE FOR SUPPLYING WATER VAPOUR TO AN INTERNAL COMBUSTION ENGINE

Abstract: A device for supplying water vapour to an internal combustion engine having at least one combustion chamber, means for supplying fuel and air to the chamber, including an air inlet provided with an air cleaner element (13), and an exhaust system to exhaust combustion gases from the chamber, which device comprises a water boiler (1) for placing in heat-exchange relation with the exhaust system, means (4, 5, 17, 19) for automatically maintaining a predetermined water level in the boiler, a pipe (10) for connecting space above the water level to the air intake of the engine downstream of the air cleaner element (13) (but upstream of a butterfly valve if any), and a scavenging hole (14) for connecting said space to the atmosphere, the arrangement being such that in use water in the boiler (1) is boiled by the heat transferred from the exhaust system (2) and wet steam passes along the pipe (10) to join the air entering the air intake, said water-level maintaining means having provision for ensuring that an adequate sypply of wet steam enters the air intake, under various conditions of use.

Description: DEVICE FOR SUPPLYING WATER VAPOUR TO AN INTERNAL COMBUSTION ENGINE This invention relates to internal combustion engines including compression ignition engines and rotary engines, and a device for fitting to said engines for supplying water vapour to the air intake. The invention is particularly though not exclusively suitable for motor vehicle engines. It has become desirable to use low grade petrol, for example lead-free petrol, in internal combustion engines to reduce the amount of pollutants emitted by these engines. The present invention aims to provide an internal combustion engine which permits this and which operates more efficiently. Various proposals have been made for supplying steam to internal combustion engines with the air used for combustion. We have now found that the main ef ect of the water in improving the efficiency of the engine is achieved by evaporation of liquid water in the combustion chamber. For this purpose, it is necessary that the water is supplied in the liquid phase as fine suspended droplets and for convenience, we shall refer to the supply of liquid water in this way as the supply of wet steam. According to the invention there is provided a device for supplying water vapour to an internal combustion engine having at least one combustion chamber, means for supplying fuel and air to the chamber, including an air inlet provided with an air cleaner element, and an exhaust system to exhaust combustion gases from the chamber, which device comprises a water boiler for placing in heat-exchange relation with the exhaust system, means for automatically maintaining a predetermined water level in the boiler, a pipe for connecting a space above the water level to the air intake of the engine downstream of the air cleaner element (but upstream of a butterfly valve if any), and a scavenging hole for connecting said space to the atmosphere, the arrangement being such that in use water OMPI In the boiler is boiled by the heat transferred from the exhaust system and wet steam passes along the pipe to join the air entering the air intake, said water-level maintaining means having provision for ensuring that an adequate supply of wet steam. enters the air intake under various conditions of use. In one form of the invention, the water-level maintaining means comprises an adjustable float valve for maintaining a variable predetermined water level. It has been found that with different vehicles, differing arrangements of exhaust pipes, engines and carburettors necessitate differing positions for the boiler. In some cases where the boiler is particularly exposed to air currents due to the engine fan or the motion of the vehicle, a full boiler may never reach a sufficiently high temperature. On the other hand, a partly filled boiler has less water to heat and will produce the required vapour at approximately the right temperature because some heating can take place in the space above the water level to compensate for the cooling effect referred to above. In another form of the invention, the water-level maintaining means comprises a water inlet reservoir beside the water boiler and connected thereto by a plurality of tubes disposed one above the other. With such an arrangement, which divides the water being heated Into a relatively small volume in the boiler itself and a relatively large volume in the reservoir, not all the water has to be heated to boiling point during start-up before steam is generated. On the other hand, the natural convection effect pre-heats the water in the reservoir so that water supplied to the boiler itself rapidly reaches boiling point under conditions of high steam demand. It has been found that by altering the volume of water in the boiler, the fuel/water ratio can be adjusted. This fuel/water ratio is the ratio of the volume of fuel to the volume of water (in the form of wet steam) fed to the engine over a period of use. The optimum ratio has been found to be about 5:1 for diesel (compression ignition) engines running on fuel oil and about 8:1 for petrol engines. These figures have been calculated for the United Kingdom: in drier climates where the relative humidity is lower, the ratio for petrol engines may, for example, be reduced from about 8:1 to about 6:1. In the case where, for example, the means for supplying fuel and air to the combustion chamber comprises a carburettor or a fuel-injection system, the steam is supplied to the air intake upstream of the carburettor or fuel-injector system. The boiler can be formed so that it receives heat from only a part of the periphery of a pipe of the exhaust system of the engine but preferably encircles a pipe of the system and receives heat from the complete periphery of the pipe. In use, the heat from the exhaust system of the engine heats the water in the boiler and produces steam. This steam is fed to the combustion chamber or chambers of the engine and since the heat produced by the engine is dependent on the engine speed,, the amount of steam supplied to the combustion chamber ill also depend on the engine speed. A condenser chamber can be located in the steam supply pipe between the boiler and the air intake so that when the engine suction is reduced, some of the steam is stored in the condenser chamber and the remainder is condensed and flows back to the boiler. When the suction is again increased, the steam stored in the condenser chamber ensures an adequate supply of steam until the extra heat generated by the combustion gases restores the balance of supply and demand. In any case the pipe connecting the boiler to the air intake should be so arranged that condensed water returns to the boiler. It will be appreciated that in the case of engines having two or more carburettors and air intakes, supply lines can lead to each air intake from a single boiler or from a separate boiler for each carburettor. In the case of V-type engines, the boilers can be provided on opposite sides of the engine with one boiler on each exhaust system. An embodiment of the device according to the invention will now be described by way of example with reference to the accompanying drawings in which the device is shown diagramatically in cross section, Fig. IB being a continuation upwards from Fig. LA. OMPI -<τ- The device shown in the drawing is intended for an agricultural tractor with a vertical exhaust or stack pipe. As shown the annular boiler or steam generator 1 is welded to the stack pipe 2 to provide maximum heat transfer but for a conversion unit an annular or semi-annular boiler 1 may be used which has an inner cylindrical wall through which the stack pipe 2 may be passed in close fitting relation. Such a conversion unit boiler may be secured to the exhaust pipe by means of an arrangement of a semi-circular clamp and two bolts, such an arrangement being similar to arrangements conventionally used for securing exhaust pipe sections together. The annular boiler 1 has a drain plug 3 for draining and flushing out and is connected by seven horizontal tubes of relatively small bore to a cylindrical water inlet reservoir 5. The reservoir 5 has a drain plug 5 and in this embodiment also serves as a steam chamber, a relatively large bore steam outlet pipe 7 being arranged to connect the upper part of the boiler 1 and the upper part of the reservoir 5. The pipe 7 is inclined so that any condensed steam and any water which splashes into it run back to the boiler. A flexible pipe 10 leads via an intermediate cylindrical condenser unit 11 to a conventional engine air cleaner unit 12 downstream of the annular air cleaner element 13; the unit 12 will usually be mounted on top of a carburettor. The unit 12 has an air inlet 12a leading to the atmosphere and an air outlet 12b leading to the carburettor. The steam should be fed to the air intake upstream of the butterfly valve (not shown) if any - some compression ignition engines with injectors do not have a butterfly or other control for the air intake. The condenser unit 11 can be simply a cylindrical metal container which permits the steam to cool. The temperature at which steam is fed by the device to the air cleaner should be about 30 C. Air can be drawn into the cleaner housing and through the element 13 from the inlet pipe 12a in the usual way. It is important that the pipe 10 should introduce steam into the housing at the downstream side of the element 13 with respect to air flow. Air can be drawn into the cleaner housing and through the element from the inlet 12a in a conventional manner. It is important that the pipe 10 should introduce steam into the housing at the downstream side of the element 13 with respect to the air flow. A hole (not shown) may be provided in the base of the cleaner housing so that, when the engine stops, any water which condenses on the element or on the inner walls of the housing can run through this outlet. The upper part of reservoir 5 has three scavenging air holes 14 which serve to mix atmospheric air with the steam and to dilute and cool it. The size of the holes will depend on the size and nature of the engine but three \ inch holes are generally suitable for petrol engines. Secured to the side of the reservoir 5 is a bracket 5 having a vertical slot through which a bolt 16 passes to adjustably mount a float valve assembly 17. The assembly 17 is fed from a water tank (not shown) through a flexible pipe 18 and maintains a constant water level in the reservoir 5 and boiler 1 via a flexible pipe 19. It is thus an easy matter to adjust this water level by slackening the bolt 16, moving the float valve assembly 17 up or down, and retightening the bolt 16. The float valve assembly 17 may be of conventional form and is preferably of plastics material to resist corrosion. The horizontal tubes 4 maintain the water level in the boiler but reduce convection flow into the reservoir (as compared to a single large tube) and thus permit more rapid water heating in the boiler. The air holes 14 need not be in the reservoir 5; it is sufficient that provision is made for sucking air into the air intake so that it carries along the steam. It is also not necessary that steam drawn from the boiler passes through the reservoir. The air holes 14 may have filters to prevent foreign matter being sucked in. In operation steam generated in the boiler collects in the space at the top of the boiler and in the space at the top of the reservoir (via the pipe 7). The suction generated by air being drawn into the engine through the cleaner element 13 draws air through the holes 14 and this air carries the steam in the upper part of the reservoir 5 through the pipe 10 and the condenser 11 into the air cleaner unit 12. The steam there joins the air entering the inlet 12a and passes through the carburettor into the combustion chamber or chambers of the engine. O PI Since the heat produced by the engine depends on the engine speed, the amount of steam received by the combustion chambers depends on the engine speed. When the throttle of the carburettor is closed, steam is stored in the condenser 11 and excess steam is condensed and returns to the boiler. Then, when the throttle is opened, the free flow of air from the atmosphere is restricted by the drag of the cleaner element 13 and reduces the pressure In the pipe 10 and this causes the water in the boiler to boil more readily. The steam stored in the condenser II provides an adequate supply of steam until the heat generated by the more rapid combustion of the fuel resulting from the opening of the throttle causes the balance of supply and demand to be restored. In a modification (not shown) the seven horizontal tubes are replaced by three 10 mm tubes.

Claims: CLAIMS 1. A device for supplying water vapour to an internal combustion engine having at least one combustion chamber, means for supplying fuel and air to the chamber, including an air inlet provided with an air cleaner element, and an exhaust system to exhaust combustion gases from the chamber, which device comprises a water boiler for placing in heat- exchange relation with the exhaust system, means for automatically maintaining a predetermined water level in the boiler, a pipe for connecting a space above the water level to the air intake of the engine downstream of the air cleaner element (but upstream of a butterfly valve if any), and a scavenging hole for connecting said space to the atmosphere, the arrangement being such that in use water in the boiler is boiled by the heat transferred from the exhaust system and wet steam passes along the pipe to join the air entering the air intake, said water-level maintaining means having provision for ensuring that an adequate supply of wet steam enters the air intake under various conditions of use. 2. A device as claimed in Claim 1, wherein said water-level maintaining means comprises an adjustable float valve for maintaining a variable predetermined water level. 3. A device as claimed in claim I or 2, wherein said water-level maintaining means comprises a water inlet reservoir beside the water boiler and connected thereto by a plurality of tubes disposed one above the other. 4. A device as claimed in Claim 3, wherein the space in the boiler above the water level is connected by a tube to the upper part of the reservoir so that steam is withdrawn from the upper part of the reservoir. 5. A device as claimed in Claim 4, wherein the tube is Inclined so that any condensed steam runs back to the boiler. 6. A device as claimed in Claim 4 or 5, wherein the scavenging hole is in the upper part of the reservoir. 7. A device as claimed in any preceding claim, wherein the pipe is provided with a condenser. 8. An internal combustion engine to which is fitted a device as claimed in any preceding claim. 9. A vehicle powered by an engine as claimed in Claim 7.

Inventors: SKEELS LOUIS REGINALD, SKEELS, LOUIS, REGINALD
Applicants: ADVANCED MOTION LTD, ADVANCED MOTION LIMITED
Application year: 1982
Main classification: F02M25
IPC codes: F02M25