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 improvements relating to turbines and compressors.
| Identifier | ExFiles\Box 147\2\ scan0202 | |
| Date | 15th December 1937 | |
| PATENT SPECIFICATION Application Date: Dec. 15, 1937. No. 34687/37. ,, ,, Jan. 12, 1938. No. 1063/38. One Complete Specification Left: Jan. 16, 1939. (Under Section 16 of the Patents and Designs Acts, 1907 to 1938.) Specification Accepted: Aug. 16, 1939. 511,278 PROVISIONAL SPECIFICATION No. 34687 A.D. 1937. Improvements relating to Turbines and Compressors I, FRANK WHITTLE, a British Subject, of Broomfield, Bilton Road, Rugby, Warwickshire, do hereby declare the nature of this invention to be as follows:— 5 This invention relates to turbines and compressors of the axial flow type. An object of the invention is to achieve a substantial improvement in the efficiency 10 of such machines. A further object of the invention is an improvement in design which takes into account an apparently hitherto neglected factor consequent upon the laws governing the flow of liquids. 15 Where a fluid has imparted to it angular momentum, as for example by a continuous ring of nozzle blades, there is created a pressure gradient in the radial direction which is accompanied by a com- 20 plementary velocity gradient such that the velocity decreases as the radius increases, and it follows that the greatest pressure is at the greatest radius. The invention seeks to take account of this in a practical 25 manner by providing a flow which satisfies the physical laws satisfactorily and enables the maximum conversion of energy to be achieved. Hitherto, it is believed, turbine rotor blades have been given a 30 twist from root to tip in accordance with the variation of linear velocity of the blades at respective radii. According to this invention the rotor and/or stator blades are formed so that 35 their effective pitch angle varies at different radial stations more than has hitherto been the practice. The shape is accordingly graduated from the inner to the outer end in accordance with formulae 40 enlarged upon below. Further, in a turbine the rotor blades have an effective pitch angle at their roots which is less, for a given set of conditions, than accepted practice, and an angle at their tips which 45 is greater. In the case of a compressor, rotor blades are shaped to convert an axial flow into a flow of uniform angular momentum about the axis, and uniform axial velocity. The stator blades are 50 correspondingly shaped to engage the flow created by the rotor blades without shock and to re-convert it into a purely axial flow. 55 In more particularly describing the invention in relation to a turbine with full peripheral admission, the stator blades have an angle of discharge which varies radially substantially in accordance with the formula:— 60 α = tan⁻¹ (r Vₐ) / C r . . . Radius Vₐ . . . Axial velocity Vw . . . Velocity in plane of rotation C = r Vw 65 The rotor blades have angles the minimum value of which is given by β = tan⁻¹ Vₐ / (c/r - u) and a discharge angle given approximately by 70 γ = tan⁻¹ Vₐ / u where u is the velocity of the blade at radius r.{Sir Henry Royce} The appropriate angles for the case of 75 the compressor will readily be seen. The above description requires some modification in the case of a “velocity compounded” wheel of two or more rows; in this case the condition for the stator 80 blades which act as nozzles still applies, but only the discharge from the last row of rotor blades would be axial. The angle of the blade system is then such that the angular momentum would be 85 uniform in the space between a set of rotor and stator blades. It is preferable that in this case the reduction of angular [Price 1/-] | ||