From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Patent application by F. Whittle for improvements in aircraft propulsion systems, commonly known as jet propulsion.
| Identifier | ExFiles\Box 147\2\ scan0190 | |
| Date | 3rd March 1936 | |
| 2 working fluid, the whole then forming a supply of working fluid capable of further expansion. In more particularly describing the invention in a form suitable for aircraft propulsion by fluid reaction, air is taken into the aircraft through a diverging passage wherein the kinetic energy which the air possesses relative to the aircraft by virtue of the forward speed is partially or wholly converted into pressure. This slightly compressed air is then further compressed to an intermediate pressure by a centrifugal compressor of moderate speed whence it passes to the intermediate pressure chamber. A portion of the air from the intermediate pressure chamber is then compressed in a second high speed centrifugal compressor and passed through a heat interchanger into a combustion chamber where it is heated by the constant combustion of oil fuel. It then expands through two impulse turbines, each driving a compressor. The exhaust from the turbines then passes through the heat interchanger, and into the intermediate pressure chamber, where it mixes with the remainder of the working fluid. The whole of the working fluid then expands through a nozzle discharging rearwardly, to provide thrust by fluid reaction. In order that the mass flow is as great as possible inproportion to the size of the components, it is deemed particularly desirable that both compressors should be of the type with bilateral intakes. The high speed compressor has an impellor with a large number of straight radial blades formed on a suitably shaped central disc which has tapering extensions forming strengthening ribs at the back of each radial blade. The impellor also has a large number of rotating guide blades to impart the initial change of angular momentum to the inspired fluid, the said guide blades being of a number and shape the most suitable for this purpose. The compressor has a bladeless discharge ring of substantial radial dimensions, and a second diffuser stage formed by a diverging passage or groups of diverging channels. The moderate speed compressor may be similarly constructed, but considerable latitude is possible owing to the less severe conditions under which it operates. The above describes one form of the invention, but there are many possible variations. For example, the compression of the lower cycle may be formed in two or more compressors, working in parallel, either driven by separate turbines or by a single turbine, or multi stage compressors may be used instead of the single stage compressors described, or again the compression of the lower cycle may be wholly or partly performed by screw type axial flow compressors. Again all compressors may be driven by a single turbine, or where more than one turbine is employed, the expansion may take place through them either in parallel or in series. An example of one such modification suitable for the propulsion of aircraft by fluid reaction is one in which two compressors working in parallel perform the compression of the lower cycle, and a single high speed compressor performs the compression of the higher cycle, each compressor being driven by separate turbines in parallel. In this arrangement two lower cycle compressors with their drivers are housed in nacelles mounted on the wing structure, while the high speed compressor and its driver is housed in the hull or fuselage; each engine being fed from a separate combustion chamber. The propelling nozzles would then be at the rear of each nacelle. Another form of the invention is one in which the higher cycle is wholly performed in any well known type of internal combustion engine. Describing a particular example of such a form, a compression ignition engine drives an air compressor which delivers air under a moderate pressure to a chamber from which the engine inspires air and into which it exhausts; only a portion of the air at the intermediate pressure passing through the engine. The engine may have a normal supercharger in addition to the main compressor. The fluid from the intermediate pressure may then be used for any desired purpose, such as the working fluid supply for one or more turbines. It can be shown that the thermal efficiency of such a combination may be as much as 30% greater than the engine working alone, and for that reason such a power plant would be very suitable for the propulsion of long range aircraft at moderately high altitudes. In all applications of this invention the shape and arrangement of the intermediate pressure chamber is such that the flow of the fluid will not permit the products of combustion to enter the intake of the higher cycle compressor. For normal purposes it would be sufficient to arrange that the higher cycle compressor inspires from the intake end of the intermediate pressure chamber while the products of combustion enter near the discharge end, but for starting, when there may not be a natural flow preventing the products of combustion from entering the compressor intake, it may be necessary to arrange an adjustable butterfly valve in the intermediate pressure chamber, whereby the intermediate pressure chamber may be temporarily divided into two parts. The supply of working fluid which results from any of the described arrangements of the invention may be further heated before final expansion of the combustion of additional fuel. Such modification may provide a useful means of dealing with a temporary overload. The invention may include any other devices necessary for its efficient operation, such as electric starter motors or hand starting means, fuel ignition devices, fuel pumps, pumps for lubrication, water jackets for the turbine wheelcases and other parts, fuel heaters, radiators, throttles or other suitable governing means, and any other necessary or desirable auxiliaries. March 3rd, 1936. F.{Mr Friese} WHITTLE. COMPLETE SPECIFICATION Improvements relating to the Propulsion of Aircraft I, FRANK WHITTLE, a British Subject, of "Blackamoors", Harston Road, Trumpington, Cambridgeshire, do hereby declare the nature of this invention and in what manner the same is to be performed, to be particularly described and ascertained in and by the following statement:— This invention refers to apparatus, the function of which is to provide a supply of working fluid at a pressure above that of the atmosphere for the purpose of propelling an aircraft by fluid reaction, such action being commonly known as "jet propulsion". A known form of such an apparatus is one in which a centrifugal compressor compresses air into a combustion chamber wherein it is intended to be heated at constant pressure by the burning of a suitable fuel, the heated products of combustion then expanding through the nozzles of a turbine, the function of which is to drive the compressor and any auxiliaries. The fluid leaving the turbine, being capable of further expansion, is a supply of working fluid for the production of power in various ways such as that cited above. In a reaction propulsion system for boats or aircraft, a prior proposal is the provision of a compressor followed by a burner and delivering through propulsion nozzle means, the compressor being fed by fluid taken in at a pressure created by movement of the whole vehicle in the fluid medium, and it is mentioned that the compressor may be fed by part of its output. The term "internal combustion engine" in the following statements includes any engine which compresses air, combustion in it, and is operated by the expansion of the combustion products, and thus includes a reciprocating internal combustion engine or a compressor-burner-turbine combination in which the turbine drives the compressor. The purpose of this invention is to provide an improved system, apparatus, or power unit, for the same purpose. The primary object is to provide as great a mass flow of the working fluid as possible in proportion to the size of the mechanisms employed, in order that certain losses, such as fluid friction loss, shall be kept as low as possible in all components. High mass flow is particularly desirable in the case of propulsion of aircraft by fluid reaction, in order that the jet velocity shall be as low as possible for a given thrust, and it is to this purpose that the invention is primarily applicable. According to the invention, there is combined in a fluid-reaction propulsion system for aircraft an air compressor which in effect divides the output from the compressor into a first stream which is passed out through a propulsion nozzle and a second stream, an internal combustion engine supplied by the second stream, and a gas turbine supplied wholly or partly by the effluent gas from said engine and driving the said air compressor. In this system the combustion products of the engine preferably contribute to the thrust by fluid reaction, for example joining the main flow from which they were originally diverted before combustion. The engine referred to may be a compressor-burner-gas turbine combination. The system is embodied, in accordance with the invention, in a unit for aircraft propulsion, and this in two examples takes the form diagrammatically illustrated in the drawings. Where a gas turbine is employed it may be adapted to operate with a plurality of stages of compression of the kind in which the compressor means is in the form of a bilateral intake centrifugal compressor | ||