Patent GB-877990-A (GB)
Title: Improvements relating to free-piston compressed gas generators
Filed: 1957-09-27
Abstract: 877,990. Free-piston gas generators. YOUNG, N. O. Sept. 11, 1958 [Sept. 27, 1957], No. 30295/57. Class 7(1). A free-piston compressed gas generator operates on a compression-ignition cycle and has only a single cylinder of constant bore containing a single piston which divides the cylinder into two similar chambers, each chamber performing as a compression ignition engine and as a gas compressor, the piston moving in one direction due to combustion of fuel injected into one chamber to compress gases in the other chamber and then back again due to combustion of fuel injected into the other chamber to compress gases in the one chamber and the cylinder being free to move to and fro substantially in an axial direction contra to the movement of the piston. In the engine shown in Fig. 4 the porting ratio has been fixed at 7À5. The outlet tube 29 extends a suitable distance away from the axis of the cylinder 22 and terminates in a yoke best seen in Fig. 5 carrying a pair of coaxial pivots 31 and 32. The pivots form the axis about which the gas generator oscillates during running. A boss 39 integral with an output manifold flange 28 is provided for the attachment of accessories not shown and especially for the attachment of weights so that the centre of mass of the gas generator is located in the desired position. The air inlet valve may in general communicate with the cylinder from any position in the cylinder head or may communicate through a port opening into the cylinder at any axial position along the cylinder provided that the pressure within the cylinder cannot fall greatly below atmospheric pressure without an entering through an inlet valve. A combined fuel injecter fuel pump and spray nozzle is employed. The fuel which can be supplied to the injecter unit at a pressure which need not exceed a few tens of atmospheres is pumped by the axial motions of an injecter bob 60 with respect to the cylinder head 23. Screwed and locked into the bob 60 is an injecter ram 63. Pressed into contact with an outer zone of the plug 65 is an injecter annulus 68. When fuel is driven into the annular recess of the plug by the ram 63 the injecter annulus separates from being in contact with the surface of the plug 65. Upon formation of a crevice between the annulus 68 and the surface of the plug the fluid seal is broken and fuel flows radially inward as the radial inward flow of fuel approached the axis it forms into a jet and sprays fuel to the right. A similar fuel spray could be formed by a conventional injecter nozzle having a much smaller and more easily obstructed hole than the one which is described. The fuel supply tube 30 extends as far as the yoke to which it is fastened, e.g. by welding near the point 36. The outlet valve 19 is seen in Fig. 7 to be a dissected ring which may be cut from a single sheet of thin metal. The inlet valve 18 as shown in the same figure can be made from a single sheet of thin metal dissected by a number of radial slots each terminating in a registration hole. Although in the generator described the cylinder oscillates along an arc of a circle centred upon a pivot it is stated that it may be preferable to allow the cylinder to reciprocate along a straight path or along some other curve.