Patent GB-1225704-A (GB)
IPC: F04D29/58
Filed: 1968-12-30
Abstract: 1,225,704. Circumferential-flow compressors. ROTRON Inc. Dec. 30, 1968 [Dec. 29, 1967], No.61697/68. Heading F1C. A circumferential-flow compressor comprises unshrouded blades projecting radially from the impeller into an annular chamber having inlet and outlet ports, the chamber being divided into a first portion occupied by the blades and a second portion clean of blades, the blades having edges conforming to the cross-sectional shape of the wall of the first portion and defining between adjacent blades and the wall a series of peripheral cavities to induce vortex motion of fluid in the chamber between the inlet and outlet ports, and a flow stripper interrupting the second portion to establish flow of the compressed fluid through the outlet port, the outlet port being located in the first portion adjacent the blades and constructed to induce angular velocity of at least part of the flow of fluid therein counter to the direction of the vortex flow of the fluid entering the outlet port. The flow stripper comprises a plate 30, Fig.3, located adjacent the inlet port 26 and serving to divert the flow of compressed fluid through the outlet port 28. A sealer plate 32 extending downstream from the stripper plate 30 for a distance preferably at least equal to the peripheral spacing between the impeller blades 18 prevents the compressed fluid entering the unbladed portion 12a of the annular compression chamber at a point adjacent the inlet port 26. As shown in Fig.7, the sealer plate 32 may have curved upstream and downstream edges 32a, 32b, the width of the sealer plate at the inner periphery of the compressor chamber being at least equal to the spacing between adjacent impeller blades, while at the outer periphery the width is preferably approximately equal to that necessary to cover all blades between the high-pressure outlet region and the lowpressure inlet region and is usually greater than twice the spacing between adjacent blades. In this embodiment, the inlet port 50, Figs.6 and 7, is of convolute form to give the fluid leaving it at an opening 52 a helical motion conforming generally to the desired motion in the compressor chamber. The outlet port 54, Figs. 9 and 10, is also of convolute form to provide a smooth transition from the direction of flow within the compressor chamber. A shoulder 55a terminates at a sharp edge which promotes a counterspin 55b which counteracts an undesired turbulence occurring in the outflowing fluid. A similar effect is produced at a shoulder (28a), Fig. 1 (not shown) in the embodiment of Fig. 3. Some of the compressed fluid fails to be discharged through the outlet port 54. To prevent this compressed fluid from entering the region of the inlet port and disrupting the flow pattern in that region, a narrow opening 56, Figs. 6 and 7, is provided adjacent the sealer plate 32 to receive the fluid, which passes through a passage 56a to be discharged at 58 into the compressor chamber at a point downstream of the inlet opening 52 in a direction substantially tangential to the desired vortex motion. Leakage flow through the clearance 34, Fig. 5B, between the impeller 16 and the housing is deflected at 41 by a ring 40 on entering the compressor chamber so that it conforms to the desired vortex motion. The ring 40 also provides a slot 42 through which a stagnant boundary layer adjacent the compressor chamber wall is bled off. Leakage flow on the other side of the impeller 16 is reduced by a series of curved ridges 38 arranged generally transverse to the direction of leakage flow. Leakage along the outer circumference of the blading is reduced by a ring (19) Figs. 1 and 4 (not shown), fixed to the outer edges of the blades and carrying radial projections (45) which project into an annular groove (19a). The two portions of the housing respectively containing the inlet port and the outlet port may be relatively rotatable so as to vary the distance between the ports and consequently vary the outlet pressure. In a two-stage embodiment, Figs. 12-14 (not shown), interstage cooling is provided by a cooling fan located between the stages and having a casing which is finned to form cooling channels.