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 specification by Frank Whittle for improvements in aircraft propulsion systems, detailing the design of a jet engine.
| Identifier | ExFiles\Box 147\2\ scan0199 | |
| Date | 17th May 1935 | |
| 2 456,980 nozzle at the delivery end. The said nozzle is of the convergent-divergent type and delivers to the whole of the first row of a two row Curtis wheel; this full peripheral admission is achieved by causing the nozzle to discharge into a passage conforming in radial dimensions and curvature in the plane of rotation to the buckets, but of helical form axially, and shaped such that the gases are passed into the turbine rotor uniformly round the periphery. The turbine nozzle may be fitted with a control valve. The exhaust from the turbine passes into a passage or chamber from whence it passes to the atmosphere through a single propelling nozzle. This propelling nozzle is fitted with a control valve of suitable type, and may also, if desirable, have a cowl or cowls arranged around its mouth for the purpose of causing the jet to modify the air flow over the external surfaces of the aircraft. The general arrangement is intended to be as compact as possible, and for this purpose, the turbine is placed as close to the compressor as the construction will permit, and it will lie as far as possible inside a space formed by the compressor casing and the combustion chamber. It is believed to be preferable that the arrangement in the aircraft should be such that in horizontal flight the plane of rotation is approximately horizontal, and hence the air intake and propelling nozzle will lie approximately parallel to the longitudinal axis of the aircraft. It is believed that this arrangement will lead to a minimum frontal area, and the least troublesome gyroscopic effects. Gyroscopic torques are likely to be large under certain circumstances, and for this reason it may be desirable to arrange that the direction of rotation of the turbine is made opposite from that of the compressor. In this case the turbine and impellor would be on separate shafts, and geared together. If such gearing is used, it is believed that a simple spur double helical gear is the most satisfactory for the purpose. The arrangement in the aircraft described will make it desirable that means should be provided for turning the fluid through approximately a right angle at the intakes of the compressor and the exhaust from the turbine. For this purpose, both the intake ducts of the compressor and the discharge duct of the turbine may be fitted with stationary deflecting vanes shaped and disposed to achieve the desired result. However this arrangement is not essential, and simple volutes or the like may be used. The general arrangement of the casing of the engine is such as to give the maximum possible rigidity and simplicity combined with low weight. For example, the inner portions of the compressor casing, the combustion chamber and the inner portions of the turbine casing may be formed in a single casting, or alternatively, two castings with a joint in a plane containing the axis or axes of the shaft or shafts. The remainder of the principle portions of the casing may be formed of two castings, one to form the outer wall or cover of the compressor and the outer air intake duct, and the other to form the outer wall of the turbine case and discharge duct, and possibly also, the housing for the propelling nozzle. Arrangements of the type described, in conjunction with suitable stiffening webs, will make the different parts of the casing mutually stiffening, and give great rigidity. The housing for auxiliary drives may be formed in either the compressor cover or the turbine cover. Arrangements for the satisfactory combustion of fuel in a high velocity air stream are described in a co-pending application No. 14,438/35, and it is believed that the arrangements there described will be very suitable for use in this invention, though other methods may be used. According to one form of this arrangement, the fuel is fed under pressure to a cylindrically shaped nozzle with a closed end, and which has near the end a number of fine holes in the nozzle wall, spirally arranged, through which the fuel is forced in a series of fine jets. The rate of fuel ejection is governed by adjusting the position of a close fitting sleeve, by means of a rod which passes through a gland in the combustion chamber wall to a suitable control. The fuel nozzle is approximately along the direction of motion of the air, and is surrounded by a cowl supported either by extension from the nozzle, or from the wall of the combustion chamber. The purpose of this cowl is to limit the travel of the fuel sprays radially, and to provide a flaming surface. On or near this surface, a hot wire or catalytic or other suitable ignition device may be placed. Various ways of controlling the engine may be provided, but it is believed that the most satisfactory method is by variation of the fuel supply accompanied by an automatic speed regulation. A suitable arrangement for such automatic speed regulation is one in which a speed governor of any suitable type is made to govern, either directly or indirectly, the throat area of the propelling nozzle by a suitable valve, and therefore the back pressure on the turbine nozzles. The governor speed setting may be made manually adjustable. For example, the governor may be linked to the piston of a piston relay valve which controls the admission of oil under pressure to a servo piston which operates the valve of the propelling nozzle. The positioning of the cylinder portion of the relay valve may be placed under manual control. Arrangements for starting may take several different forms, but it is believed that the most satisfactory method is to provide means for speeding up the rotors by hand, or electric motor, or mechanically, or by any other suitable arrangement, with the turbine nozzle in the fully closed position, so that mass flow is temporarily prevented until a suitable speed of rotation has been attained, after which the admission of a small quantity of air and the ignition of the fuel jet should be sufficient to complete the starting. Alternatively the turbine may be rotated with compressed air for starting purposes. It is also proposed to provide an auxiliary compressor for the supply of compressed air to a hermetically sealed cockpit for breathing purposes at high altitudes. Such a compressor of any type suitable for the purpose may draw air from the main compressor discharge passage and pump it into the cockpit at a suitable pressure. 456,980 3 It will also be necessary to provide a fuel pump, and possibly also, a pump for lubrication. Such pumps may conveniently be of normal gear type. All these auxiliaries may be driven from an extension of the turbine shaft, with suitable reduction gearing where necessary. It should be understood that much of the apparatus specified is provisional, and that only one of many possible arrangements has been described, and that many modifications of these arrangements may be made without departing from the invention. For example, the compressor may have more than one stage, or more than one discharge passage, and there may be more than one combustion chamber, or a normal arrangement of turbine nozzles may be used instead of the single nozzle described. It should be further understood, that components and details not particularly specified, such as materials, packings, lubrication and the like, are those most suitable for the efficient operation of the engine. One aircraft may have one, or a plurality of these engines. Dated the 17th day of May, 1935. 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 is for improvements in aircraft propulsion systems of the kind in which air is taken into the system, compressed, heated, partially expanded in a turbine which drives the compressor, and expelled rearwardly to provide a propulsive thrust by fluid reaction. A propulsion system of this kind is described in my patent Specification No. 347,206. The object of the invention is to provide an aircraft propulsion system of this kind in which the volumetric capacity and efficiency are increased and this object can be achieved by increasing the mass-flow of the gas through the system and by the use of a compressor constructed in accordance with the specification of patent application No. 14,285/35 (Serial No. 456,976). According to one feature of the present invention, a propulsion system of the kind described comprises a compressor having two air intakes, one on each side of the plane of rotation of the impellor. By this means a high mass-flow of air through the system is obtained, which is the fundamental requisite for thermodynamic efficiency, propulsive efficiency and a high power-weight ratio. According to another feature of the invention, an impulse turbine for driving the compressor is provided with a nozzle having a single annular orifice extending substantially entirely around the periphery of the turbine rotor. According to another feature of the invention, the outlet from the compressor is connected to the inlet to the turbine by a combustion chamber of continuously smooth form so as to minimise turbulent | ||