Patent GB-826669-A (GB)
Title: Improvements in or relating to axial-flow compressors
Inventor: TURNER RONALD CHARLES
IPC: F04D29/54
Filed: 1955-07-18
Abstract: 826,669. Axial-flow compressor blading. POWER JETS (RESEARCH & DEVELOPMENT) Ltd. July 17, 1956 [July 18, 19551, No. 20783/55. Class 110 (3). [Also in Group XXXIII] In an axial-flow compressor having a row of rotor or stator blades provided with shroud means at the blade tips, means are provided in the region of the shrouds to afford a flowpath between the working fluid passages on opposite sides of a blade of the row. Means may also be provided affording a flowpath between the passages on opposite sides of a blade of the blade row adjacent the root portion of the blade. In the compressor shown, the rotor 2 carries rows of blades 4, 6, 8, 10, 12 mounted by their roots 13 in circumferential grooves, and the stator easing 1 carries rows of blades 3, 7, 9, 11 likewise mounted by their roots 33 in circumferential grooves. The rotor blades 4 have a shroud ring 16 secured at their tips by projections 17, recesses 19 being formed in the blade tips beneath the shroud ring 16 so that working fluid can pass from one side of the blade to the other. The shroud 16 is disposed within a channel 18 formed in the stator easing. The stator blades 5 are secured by a spigot 20 and nut 23, small gaps 24 being left between the blade aerofoil portion and the surface of the casing so that working fluid can pass across the blade profile. Similar gaps 27 are provided at the blade tips between the aerofoil portion and the shroud band 25, the shroud band 25 being disposed in a groove 26 in the rotor. The rotor blades 6 have a shroud band 16 and apertures or recesses such as 28, 29 or 30 are provided through the aerofoil portion adjacent the shroud. Similar apertures 31, 32 are provided through the aerofoil portion adjacent the root 13. The shroud band 25 of the stator blades 7 is formed with axially-spaced dimples 36 which afford communication between the two sides of the blade at the blade tips. The shroud band 16 of the rotor blades 8 is likewise provided with a plurality of circular dimples 37 to afford passages between the shroud and blade tips. The root 13 of the rotor blades 8 is provided with a transverse bore 38 and short bores 39, 40 disposed on either side of the blade aerofoil portion. The shroud band 25 of the stator blades 9 has radially-extending holes 41, 42 on either side of each blade aerofoil, communication between the two sides of each blade being afforded by the holes 41, 42 and the groove 26 in the rotor in which the shroud band 25 is disposed. The rotor blades 10 have a shroud band 16 likewise provided with radial apertures 43, 44 on either side of the blade aerofoil portions, working fluid passing from one side of each blade to the other through the apertures 43, 44 and the channel 18. The shroud band 25 of the stator blades 11 is provided with recesses 45, 46 in its edges, the recesses 45, 46 and groove 26 affording a path for working fluid from one side of the blade to the other. The rotor blades 12 have root portions 13 the abutting surfaces of which are inclined and are formed with radial grooves, 48, 49, the grooves in each pair of abutting surfaces co-operating to form holes which with the groove 50 beneath the blade roots afford a path for fluid flow from one side of the blade to the other. The shroud members 51 of the rotor blades 12 have radial grooves 53, 54 similar to the root portions. The object of the invention is to reduce the tendency for the blades to stall.