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 F. Whittle for improvements in internal combustion turbines, detailing compressor and turbine arrangements.
| Identifier | ExFiles\Box 147\2\ scan0194 | |
| Date | 24th July 1935 | |
| 2 461,887 ment, the said compound diffuser contain- ing of an inner bladeless portion of con- siderable radial dimensions, and an outer ring of stationary diffuser blades. Various modified forms of this type of compressor may be used, for instance it may have a diverging volute in addition to or instead of the stationary diffuser blades. This compressor is intended to operate at tip speeds well above the acoustic velocity, and hence it is believed that one stage only will suffice to produce a suf- ficient compression, though if progress in turbine blade material permits more than one stage may be used. Possible arrangements of the principal components are as follows:— (a) The whole of the expansion may take place in one pressure stage through a single turbine wheel, in which case a two or three row Curtis wheel would be preferable. It is probable that with this arrangement it would be necessary to drive the compressor or compressors through gearing. (b) Two stages of expansion may be em- ployed, one stage being sufficient to pro- vide the power necessary to drive the com- pressor or compressors, and the remainder for providing the net output of the engine, turbines being used to transform the energy of each stage. (c) The whole of the expansion may take place in one pressure stage, but is divided between the turbine or turbines driving the compressor or compressors, and the turbine or turbines providing the useful power. (d) The whole of the expansion may take place in one pressure stage, and the whole of the working fluid passes through two oppositely rotating wheels in suc- cession, the said wheels being either con- nected by gearing or not connected at all, one being used to drive the compressor, and the other to provide the useful power. With any of these arrangements mul- tiple, or multi stage compressors, or both, may be used. In more particularly describing the in- vention in one form, a unit (hereafter called a compressor unit) consisting of a single stage compressor, a combustion chamber, and a single row impulse turbine on the same shaft as the compressor, sup- plies another turbine (hereafter called “ the power wheel ”) with hot gases under pressure. Part of the energy of expansion is thus utilised in the “ com- pressor unit ”, and the remainder passes to the power wheel. For high altitude aircraft, it is deemed desirable that the exhaust from the com- pressor unit should form the supply for the power wheel, that is to say, there are two stages of expansion, but for ground units it is believed to be preferable that the power wheel should receive its supply direct from the combustion chamber of the compressor unit, that is, a single stage divided expansion. With either arrangement, the power wheel is mechanically independent of the compressor, and if necessary may be made to rotate in the opposite direction in order to cancel out gyroscopic torques. The turbine driving the compressor and the power wheel are each fed from single nozzles which discharge into a suitably shaped “ delivery channel ” such that the gases are fed into the buckets of the wheels uniformly round the periphery, thus securing full peripheral admission with a single nozzle, in furtherance of the object of maximum mass flow in propor- tion to size. The arrangement described above per- mits of very considerable latitude in design, for example, a number of com- pressor units may feed a single power wheel, or one compressor unit may feed several power wheels. Various ways of controlling the engine may be provided, but it is believed that the most satisfactory method is by varia- tion of the fuel supply accompanied by automatic speed regulation. For ex- ample, it is believed to be desirable that the speed of the compressor unit should remain constant under most conditions of load on the power wheel, and thus a speed governor on the compressor unit may be made to regulate the proportion of the ex- pansion taking place through the turbine of the compressor unit by controlling the nozzle valves of the respective wheels. Arrangements for starting may take several different forms, but it is believed that the most satisfactory method may provide means for speeding up the rotors of the compressor unit by hand, or electric motor, or mechanically, or by any other suitable arrangement with the turbine nozzle valves 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 com- plete the starting of the compressor unit. The starting of the power wheel may then be achieved by increasing the fuel sup- ply and opening the nozzle valve of the power wheel. Alternatively compressed air may be used for starting up the com- pressor unit. Where a power plant of this type is in- tended for a high altitude aircraft, it is proposed to provide an auxiliary com- pressor for the supply of compressed air 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. This compressor may be driven either by the turbine of the compressor unit, or by the power wheel. It will also be necessary to provide a fuel pump, and possibly also a pump for lubrication; such pumps may con- veniently be of normal gear type. For units intended for operation at ground level, it will probably be sufficient to provide turbine buckets of a material such as the well-known Silicon-Chrome valve steel, which retains a considerable strength at high temperatures, but for high altitude aircraft it is desirable to provide buckets which will not only have a strength sufficient for their purpose at high temperatures, but which will also prevent the passage of large quantities of heat to the turbine discs, in order to avoid the cooling difficulties which would arise in a rarefied atmo- sphere. For this reason it is proposed to provide a type of bucket consisting of two materials, the outer portions consist- ing of a heat resisting material of low heat conductivity, carried by a stout core of high tensile steel. For example the outer portion of a bucket may be formed from fused silica, this being carried on a steel core and retained radially by an outer shroud ring of steel riveted to the steel core of each bucket. Again the outer portion of a bucket may be formed from such materials as are used for high speed tool tips, and consisting largely of the fused carbides of Tungsten, Chromium, Vanadium and the like. It should be understood that much of the apparatus specified is provisional, and that many modifications of these arrange- ments may be made without departing from the invention. For example, the compressors may have more than one stage, and each stage may be separately driven by its own turbine. There may be a plurality of combustion chambers, or a normal arrangement of nozzles may be used with the turbines in- stead of the single nozzles described. It should be further understood that components, and details not particularly specified, such as materials, packings, casings, bearings, lubrication and the like are those most suitable for the efficient operation of the engine. Dated the 24th day of July, 1935. F.{Mr Friese} WHITTLE. 461,887 3 COMPLETE SPECIFICATION Improvements relating to Internal Combustion Turbines I, FRANK WHITTLE, a British Subject, of Blackamoors, Harston Road, Trump- ington, Cambridge, 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 relates to that type of internal-combustion turbine in which a constant pressure cycle is employed and in which the compression is effected wholly or in part by a centrifugal compressor and the expansion takes place wholly or in part through a turbine or turbines from which the useful power is taken. The object of the invention is to pro- vide an improved prime mover of this type which has a high power-weight ratio. There are many prior proposals of a similar nature, but all turbines of this type have hitherto been condemned on the ground that if the working fluid is to en- gage the turbine buckets at a temp- erature they can withstand continuously, then the efficiencies of turbines and centrifugal compressors are such that too little power is available for useful work when the power necessary to drive the compressor is subtracted from that realised at the turbine shaft. Though this argument loses some of its force when considering a gas turbine suit- able for operation at high altitudes, nevertheless real success depends upon a considerable improvement in the efficiencies of both the centrifugal com- pressor and of the turbine, and also in the successful production of turbine buckets which are either cooled, or made of materials which have all the necessary mechanical properties at very high tem- peratures. It is believed that the great improve- ments in materials and methods of cooling which have taken place in the develop- ment of exhaust valves for high duty aero engines have considerably reduced the turbine bucket difficulty. The efficiency of both turbines and com- pressors depends upon the ratio of the losses which occur to the energy conver- sion which they produce These losses consist principally of (a) Fluid friction losses, (b) Shock losses, (c) Bearing friction. Amongst other things, the fluid friction | ||