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 for an aircraft design with a jet engine that ingests boundary-layer air to improve propulsive efficiency and reduce drag.
| Identifier | ExFiles\Box 147\2\ scan0214 | |
| Date | 23th March 1939 guessed | |
| 2 512,064 by constant-pressure-cycle gas, turbine arrangements in conjunction with rearward jets. The present invention seeks primarily to increase propulsive efficiency. 5 The invention also seeks to provide an arrangement or layout of an aircraft employing jet propulsion, wherein are afforded propulsive efficiency and a particularly convenient disposition of pilot, 10 engine, and propulsion nozzle. This arrangement is especially favourable to military use, owing to good pilot's view and absence of an airscrew, the latter feature enabling a number of guns to be 15 grouped in the nose. Although in the following example a single power unit (engine, nozzle, etc.) is shown, the invention is applicable to aircraft having a plurality of such units, in which case the 20 units may comprise nacelles or compartments in wings. There have been prior suggestions to provide aircraft or nacelles of aircraft with gas turbine arrangements the exhaust 25 gases of which are agitated rearwardly for propulsion, and in which air intake was provided for by a forwardly facing bell-mouthed or like duct. Such a location for the air intake is not efficient since it 30 does not make use of the fact that there are regions of the aircraft surface where the total head in the relative airflow is inevitably less than the total head in the undisturbed relative airflow, whilst the 35 head in the airflow immediately in front of an air-displacing shape such as a nacelle, is not reduced or substantially affected by the passage of the aircraft. The invention consists primarily in an 40 aircraft with a combustion engine consuming compressed air, in which provision is made for some or all of the air to be consumed (before final compression) to be derived from one or more regions of the 45 surface of the aircraft where the relative airflow due to flight is reduced in total head below the total head of the undisturbed relative airflow by skin friction or its effects, the exhaust from such engine 50 being directed rearwardly, all in such a manner that the intaken air (subject to such chemical or physical change as may be caused by the engine) is emitted as a propulsive jet. Underlying this arrange- 55 ment is the idea that the aircraft in flight has in any case to entrain and thus accelerate (retard relative to the aircraft) a certain mass of air, and in existing practice has also to accelerate engine in- 60 take air, and in so doing has to expend a certain amount of energy which is partially or largely lost: the present invention reduces the loss by enabling the aircraft only to accelerate such air as is 65 aerodynamically inevitable (as distinct from accelerating air for engine aspiration, wastefully), and by making use of some of that air for the engine. Put in another way, the arrangement is such that 70 boundary-layer air which has already been entrained and accelerated by the aircraft structure is supplied to an engine of the reaction or jet propulsive type, with the double economy that drag directly on the 75 aircraft, and also that energy wastage which is usual in aircraft due to the necessary acceleration of engine-intake air, are reduced. Drag on an aircraft other than induced drag, is due either directly 80 to skin-friction or to a secondary effect of skin friction, viz. the setting up of turbulence. There are regions of the surface of an aircraft where, by virtue of such drag, the relative airflow is at less head than the 85 total head in the undisturbed relative flow to the aircraft. These are regions from which it is believed to be advantageous to derive the engine intake air, since the air in such regions has in any case been 90 accelerated by the passage of the aircraft. The invention is especially applicable to aircraft of which the engine is such as to have a very large throughput of air, for the purpose of jet or reaction propulsion 95 without an airscrew, and Specifications Nos. 456,976, 456,980, and 471,368 are cited as disclosing typical engines of this type. The invention includes certain structural arrangements in an aircraft, 100 which will be enlarged upon by way of example with the aid of the accompanying diagrammatic drawing. In this drawing appears the arrangement of a mid-wing monoplane in side ele- 105 vation. It is to be understood that the invention may be embodied in other arrangements and is, for example, applicable to nacelles as well as to fuselages, and may in some cases also be embodied 110 mainly within the thickness of a wing. In the case illustrated, a circular or oval sectioned streamline fuselage 1 has a monoplane wing 2, main undercarriage wheels, and nose-wheel 4. The pilot's 115 compartment has a transparent cover 5 and the pilot can also see out through a forward and downward window 6. The rear part of the fuselage, following the streamline shape, carries empennage sur- 120 faces at 7. The streamline form of the under-part of the fuselage is truncated at 9, where a circular propulsion nozzle is provided, directed rearwardly and as nearly as possible coaxial with the fore- 125 and-aft axis of symmetry of the aircraft, so as to produce a thrust-line approximately passing through the centre of drag of the whole aircraft. Internally, the fuselage 1 is divided 130 into a forward compartment, containing 512,064 3 pilot, fuel tank, etc., and a rear compartment. A bulkhead 10 which its airtight separates these compartments, and the ward compartment may be made airtight 5 and used as a "pressure cabin" if required. Within the rear compartment is mounted the engine 11, which, as shown, is the outline of that shown in Specification No. 456,980. The engine 10 delivers its exhaust gases through the conduit 12, to the nozzle at 9. The under part of the tail-end, at 13, and such parts of the empennage as may be required, may be of highly heat-resisting material or 15 may be protected by insulative material. The engine 11 works in the atmosphere of the rear compartment; this is supplied with air through forwardly-facing intake scoops 14 which are faired rearwardly into 20 the general contour of the fuselage 1 as at 14A. Ahead of the scoops 14, the surface of the fuselage may be recessed inwardly and rearwardly, as by forming "flats" indicated at 15. 25 The scoops 14 are arranged, as shown, in a ring circumferentially around the fuselage 1, and they are in the region of greatest girth, or somewhat rearward of that region. In the drawing the extent 30 to which they project into the relative airflow is exaggerated in proportion. It is not expected to be found necessary to have as much projection. Within the scoops 14, and either locally 35 behind each scoop or as a circumferentially continuous ring, a guide surface 16 is provided within the fuselage, which is so formed that the air passage way within the scoop is divergently formed, 40 progressively rearwardly increasing in cross section, in order to convert the kinetic energy of the incoming air into pressure energy and consequently to encourage an increase of pressure within the rear com- 45 partment of the fuselage. Instead of individual scoops such as 14, a single scoop extending partly or wholly around the fuselage 1, may be provided. Again the scoops may be omitted and 50 other intake means, such as a localised patch of porous skid, may be substituted. Ducting within the wings 2, leading from regions of relatively low air-velocity into the surface of the wing into the rear com- 55 partment, may supply further air for the engine. Such an idea has been suggested previously, in a general sense, for the sucking-in of boundary-layer air from a wing. 60 It will be seen that the aircraft is of particularly clean form, and the landing gear even if not retractable, is probably not so protuberant as to give rise to excessive drag. This arises to some extent 65 from the fact that aircraft according to this invention have no airscrew and therefore the problem of providing ground-clearance for an airscrew does not arise. Having now particularly described and 70 ascertained the nature of my said invention, and in what manner the same is to be performed, I declare that what I claim is :- 1. An aircraft with a combustion engine 75 consuming compressed air, in which provision is made for some or all of the air to be consumed (before final compression) to be derived from one or more regions of the surface of the aircraft where the relative 80 airflow due to flight is reduced in total head below the total head of the undisturbed relative airflow, by skin friction or its effects and in which the exhaust from such engine is directed rearwardly, 85 in such a manner that the intaken air (after being subjected to chemical and/or physical changes within the engine) is emitted as a propulsive jet. 2. An aircraft according to claim 1, in 90 which the combustion engine is adapted to expend the whole of its useful work in propelling the aircraft by reaction propulsion. 3. An aircraft according to claim 1 or 95 2, in which there is no propulsive air-screw. 4. An aircraft according to claim 3, in which the landing gear is of a tricycle type and only sufficiently protuberant be- 100 neath the aircraft for running purposes. 5. An aircraft according to claim 1, in which the engine is enclosed in a compartment to which air is supplied from the said regions. 105 6. An aircraft according to claim 1 or 5, in which air to be consumed by the engine is derived from an opening or openings disposed around a streamlined fuselage or nacelle in a region of approximately maxi- 110 mum girth thereof. 7. An aircraft according to claim 6, in which the air openings are formed by forwardly facing scoops. 8. An aircraft according to claim 7, in 115 which a passageway or ways within the scoops has or have a rearwardly divergent form, substantially as and for the purpose described. 9. An aircraft according to any previous 120 claim, in which the exhaust from the combustion engine is through a rearwardly directed nozzle arranged at a truncation of the streamline form of a fuselage or nacelle, substantially as described. 125 10. An aircraft according to claim 1 and 2 comprising a streamline fuselage, a rear compartment therein housing a combustion engine adapted for reaction propulsion, a rearward nozzle for propulsion 130 emerging from this compartment, and a | ||