Patent GB-761122-A (GB)
Title: Improvements in machines operating according to a modified stirling cycle
Inventor: RIGBY RICHARD
IPC: F02G1/043
Filed: 1951-10-03
Abstract: 761,122. Hot gas engines ; combustion product engines ; two-stroke cycle engines ; cycles; pumps. SHELL REFINING & MARKETING CO., Ltd. Sept. 24, 1952 [Oct. 3, 1951], No.. 23034/51. Classes 7 (1), 7 (2), 7 (3) and (6). [Also in Groups XIII] A machine operating according to a modified sterling cycle in which gas or fluids which will burn to produce gas at a temperature above the temperature of the working gas at the heat absorption side of the regenerator is admitted to the system at the heat absorption side of the regenerator and flows at least in part unidirectionally through the regenerator to the heat rejection side of the regenerator whence gas at the heat rejection temperature of the working gas is withdrawn from the system and gas at a temperature below the heat rejection temperature of the working gas is admitted to the system at the heat rejection side of the regenerator and which possesses one or both of the following features :-(i) the gas or fluids. are admitted to the heat absorption side of the regenerator from a first space in which the pressure at the time of admission is higher than that obtaining in the system which first space is either isolated from the system at all other times or is only in communication with the system at such other times under such conditions that the first space has substantially no effect on the compression ratio and (ii) the withdrawal of gas from and the admission of gas to the system at the heat rejection side of the regenerator are so controlled as either to prevent communication during the existence of the higher pressures in the system between the system and a second space to which the gas is withdrawn and from which cooler gas is admitted or to permit such communication only under such conditions that the second space has substantially no effect on the compression ratio. The invention is applicable to heat engines, heat pumps and refrigerators. When operating as a heat pump the hot gas will be only slightly higher in temperature than the gas it meets on entering the cylinder and the first and second spaces are conveniently recuperative heat exchangers. In Fig. I air under pressure is supplied at 19 and liquid fuel at 18 to the combustion chamber 10. At the bottom dead centre the inlet valve 7 opens under the action of the hot gases and these gases are admitted to the cylinder. Cooled scavenge gas is supplied to the cylinder from the cooled heat exchanger 11 under the influence of the blower 12. The hot gas may be admitted during the existence of higher pressures in the system. The hot gas may be allowed to trickle into the working cylinder on the hot side of the regenerator continuously throughout the operation of the system excess gas being withdrawn at the most economical time which will normally be when the pressure in the system is low. Mixture may be compressed and fed to the combustion chamber 10 and burnt by using a suitable flame stabilizer or baffle over a limited range of fuel flow. A further development is to inject the greater part of the fuel by means of a suitable valve at a point indicated by the reference B or C (Fig. I) retaining the combustion chamber at A to supply a relatively small amount of hot gas at such a temperature as to ensure rapid and complete combustion of this fuel. If the gaseous or atomized liquid fuel is injected at B this supply can be continuous since it is evident that mixing with hot gas from the combustion chamber 10 and combustion of the fuel will only occur when the valve 7 opens. If part of the fuel (gaseous or atomized liquid) is injected directly into the cylinder at the point indicated by the reference C it is evident that a timed injection is necessary to coincide with the operation of the valve 7. Suitable turbulence will also have to be provided in the cylinder 1 to ensure mixing of the fuel and air to complete combustion. Alternatively the whole of the (gaseous or atomized liquid) fuel could be injected at the point indicated by the reference B or C and no combustion chamber employed. In this case the combustion may be a continuous or wholly intermittent process in the cylinder and if it is the latter ignition arrangements such as sparking plugs to ensure its persistence must be provided in the cylinder. The loss of energy in gas withdrawn from the system may be partly recouped by expanding the exhaust gas through an auxiliary engine whose output may be coupled to the main engine crankshaft or which may be used to drive a compressor associated with the fuel feed system i.e. a compressor for feeding fuel or a medium for supporting combustion or both. The exhaust gas may drive a constant volume auxiliary engine that is an engine which takes a volume of gas proportional to its running speed this engine being coupled to the crankshaft of the main engine. A compressor associated with the fuel feed system may be driven either independently or by the main engine. In either case control of the engine output can be effected by means such as a throttle for controlling the delivery pressure of the compressor. Increase of this pressure will then either increase the speed of the engine against a constant load the mean effective pressure remaining constant or will maintain the engine speed against increasing load the mean effective pressure then increasing with load. If the compressor is driven independently of the main engine a high torque at low speeds can be obtained making the combination suitable for vehicle propulsion. The fuel supply may be controlled in dependence on both the engine speed and the setting of the member for controlling the delivery pressure of the compressor so that it is proportional both to this speed and the mass flow of combustion supporting medium delivered by the compressor. The lower pressure in the system may be above atmospheric. The mean effective pressure may be controlled by controlling a valve 20. Fig. III shows a four cylinder engine. The cylinders can be mounted in a group and the pistons be driven by a swash plate or Z crank. A four cylinder radial engine with a single throw crankshaft is sometimes convenient. An alternative layout is to arrange the cylinders in the form of a 90‹ V with two cylinders per bank coupled on a two-throw crankshaft the cranks being at 180 degrees. The cooled heat exchanger is shown diagrammatically at 11. Fig. IV shows a refrigerator which operates by absorbing heat in a heat exchanger 36 and rejecting heat from a heat exchanger 35. Non-return valves 37, 38, 40, 41 function to permit passage of gas only in the direction of the arrows. Throttle valves 39, 42 are provided. Each heat exchanger is only in communication with the cylinder at a time when' there is a higher pressure in the cylinder than in the heat exchanger under conditions which prevent the heat exchangers from having substantially any effect on the compression ratio. Although described as non-return valves the valves 37, 38, 40 and 41 might alternatively be operated from a camshaft. The same applies to the throttle valves 39, 42. In Fig. V transfer of working gas is effected by two pipes 50, 51. The pipe 50 is provided with non-return valves 52, 53.' The pressure of the working fluid may be controlled by a valve 34. Heat pumps may be constructed with a regenerator moving in relation to the working gas as in the engine of Fig. I and heat engines may be constructed with a fixed regenerator and opposed pistons as in Fig. IV. The regenerators are preferably made of ironchromium nickel alloy wire or a ceramic regenerator may be used.