It is well known that gas generators have a tarnished reputation with regard to the pollution they create and also with regard to the troublesome attention that is required. Furthermore such generators are unable to 10 produce satisfactory gasification under load and the highest possible engine output power is therefore not achieved.

The poor total efficiency of an internal combustion 15 engine is due to the considerable loss of heat through the exhaust gases and through the engine cooling water.

It has been found, however, that this energy can be 20 recovered by passing the primary air of combustion first through a first heat exchanger for heat exchange with the engine cooling water and then through a second heat exchanger for heat exchange with the exhaust gases, therewith to improve the operating 25 efficiency of a gas generator and of the engine, with subsequent improvement in range.

The actual generating part of the generator is con¬ structed so that it can be adjusted to the best gasi- 30 fication process at that time with regard to the varying nature of the solid fuel.

The actual fuel container may include the generating part of the generator or the generating part may be 35 placed in a smaller container which holds only a small amount of fuel, and to which fuel is supplied from a

* fuel magazine. A pipe connects the fuel container to r ^■ j, _l _ the fuel magazine.

40 The present invention is intended for application with two-stroke and four-stroke engines comprising recipro¬ cating pistons, although it can also be applied in rotary piston engines such as the ankel engine.

However, it is probable that the invention can be also applied effectively in gas turbines and jet engines and also in gas generators that are intended for heating purposes. It will therefore be understood that the invention has a wide area of use.

An exemplifying embodiment of the invention will now be described in more detail with reference to the accompanying drawing, the single Figure which is a schematic illustration of the inventive gas generating arrangement.

The illustrated arrangement includes a fixed cylinder 1 which has an apertured part 2 and which is closed at one end and open at the other. A moveable cylinder 3 is mounted in the cylinder 1 and carries at one end a shaft 4 by means of which the cylinder 3 can be moved to a selected position by rotating the shaft 4, either manually or mechanically. Mounted in the fixed cylin- der 1 is a grating 5 which can be brought to a given position in the aperture 2 and therewith exposed to solid fuel 6 that lies above the grating. The grating 5 and the aperture 2 coincide mutually both with regard to surface area and shape. The hole pattern of the grating, by which is meant the hole diameter and the centre-to-centre distance between the holes, is critical constructionally in obtaining qualitative and quantitative gas generation. The cylinder 3 may in¬ clude several mutually different grating surfaces, so as to enable the best solid fuel gasification process to be obtained at that particular time, by appropriate rotation of the cylinder 3 with the aid of the shaft 4.

The primary air of combustion is taken primarily from the surrounding ambient air, secondarily from a cool¬ ing water heat exchanger 7, which is heated by an internal combustion engine and which is in constant use for the primary air required by the gas generator,

wherein the temperature of said heat exchanger being regulated by the cooling water thermostat of the engine, and thirdly from a heat exchanger 8 in which an exchange of heat takes place between the air of combustion and the exhaust gases. A primary air nozzle 9 is mounted between two holders which are provided with elongated slots, which may be straight or curved in shape. The illustrated primary air nozzle comprises a tubular member which is closed at both ends and which has an elongated slot ( not shown) which functions to spread a maximum amount of air over the surface of the grating 5. The tubular air nozzle 9 is guided for movement in the slots in the holders by means of a respective guide pin mounted on each end of the nozzle. Primary air is delivered to the nozzle 9 through an air duct 10 and the height of the nozzle 9 above the grating 5 and the aperture 2 can be adjusted through the medium of a schematically illustrated lifting and raising device 11. The temper- ature of the exhaust gas/primary air heat exchanger 8 is regulated by means of a throttle means 12. The thus heated primary air of combustion provides a signifi¬ cant heat boost which in turn results in an elevated reduction temperature. In order to prevent this ele- vated temperature from initiating destruction of the material exposed to reduction and oxidation, a certain amount of engine exhaust gases 13 are returned, these gases containing carbon dioxide which when coming into contact with glowing carbon undergoes an endothermic reduction to carbon monoxide. The exhaust gases are captured by a "catcher" which is inserted into the exhaust pipe. The catcher functions to capture exhaust gases, which enter under overpressure and are passed along a pipe to an ejector nozzle 15 mounted on the bottom of a cyclone purifier 14. The ejector is adapt¬ ed so as to obtain a given overpressure and sub- pressure, such as to enable the stream of exhaust gas to return the carbon particles that settle continously on the bottom of the cyclone purifier. The returned

exhaust gases and carbon particles are passed to the combustion process through a pipe 16 leading to the primary air duct 10 and from there to the primary air nozzle. This returned exhaust gas lowers the reduction temperature. This temperature is again raised by activating the throttle 12, which results in raising the temperature of the exhaust gas/primary air heat exchanger and also in raising the reduction tempera¬ ture. This temperature is again lowered as more ex- haust gases are returned. Because of the greater need to return more exhaust gas, the ejector nozzle 15 must be a variable nozzle so that it is able to allow more exhaust gases to pass through while nevertheless maintaining the purifying process, by collecting carbon particles from the bottom of the cyclone puri¬ fier and/or that exhaust gases are returned directly to the primary air duct 10 through a pipe 18 and through the agency of a further throttle means 17. Thus, there is found a point at which the reduction temperature can no longer be maintained, with the result that the heat value of the gas will fall and therewith cause a reduction in engine power. Instead of controlling the reduction temperature by means of the aforedescribed exhaust gas return process, the temperature can be controlled with the aid of water, steam or superheated steam, or these two processes may be combined. The water is injected prior to the prima¬ ry air of combustion entering the exhaust gas/primary air heat exchanger when concerning steam generation. The water is metered by means of a device 19 which pumps the water or draws the water by suction into a pipe 20 upstream of the exhaust gas/primary air heat exchanger. When only water is to be supplied, the water is delivered to a point downstream of the ex- haust gas/primary air heat exchanger by means of the device 19 and a pipe 21, instead of through the pipe 20. The water may be preheated, by passing it through an electric heating device.