Patent GB-762254-A (GB)
Title: Radial flow rotary compressor
IPC: F04D21/00
Filed: 1954-08-17
Abstract: 762,254. Centrifugal compressors. RHEINISCHE MASCHINEN UND APPARATE GES. Aug. 17, 1954 [Aug. 17, 1953], No. 23927/54. Class 110 (1). In a radial-flow compressor, the fluid leaves the rotor with supersonic velocity, one or more compression shocks being produced downstream of the rotor, and the formation or entrance of compression or rarefaction waves in or into the rotor is prevented. Fluid leaves the impeller 10, Fig. 6, of a centrifugal compressor at supersonic velocity (with a radial component which may be subsonic or supersonic) and is subjected, while traversing diffuser blading 12a, to an oblique and curved shock-wave 81 and a normal shock-wave S2, after which the velocity is subsonic. The channels between the blades 12a are of convergent-divergent form, the divergency being attained by shaping the blades 12a as shown or by increasing the distance between the casing walls towards the outlet. Shockwave 81 may be followed by several, for example two, reflected waves. In the diffuser blading shown in Fig. 9, pressure-equalizing holes or slits 20 are provided both upstream and downstream of the shock-waves S, communicating with hollow spaces 21 and 22 respectively. This stabilizes the position of the shock waves S. The holes or slits may be provided in the casing wall, communicating with pressure-equalizing spaces outside the casing. Diffuser blades 25, Fig. 12, may be pivoted at their leading edges 26 so as to be deflected by the flow into the dotted positions when the flow direction changes from c1 to c1<SP>1</SP> as a result of a change in the speed of the impeller or of the flow being throttled ahead of the impeller. The diffuser blades may be turned by an external adjusting device, operable manually, or coupled with a throttle or a speed regulator, or controlled by a device sensitive to the flow velocity. Alternatively, the diffuser blades may be carried by a wheel which is stationary when the compressor is operating at the design conditions. Under other conditions, the wheel rotates at such speed and in such a direction as to compensate for the departure of the inflow from the design direction. The rotation is controlled by coupling the drive of the wheel with the control means of the compressor or by allowing it to be rotated by the fluid forces acting on it. The diffuser blading shown in Fig. 14 can be used at two different operating conditions. For this purpose, the main fixed diffuser blades 28 are supplemented by auxiliary blades 30 when the inflow has the direction shown. The first reflection S2 of each shock-wave S1 impinges at the edge 35 joining two flanks 31, 33 of each blade 30. When the inflow is in the alternative direction, the auxiliary blades 30 are sunk in the sides of the casing and the blades 28 are used by themselves. The auxiliary blades need not be contiguous with the main blades, but may be both upstream of and between them. A further ring of auxiliary blades may be provided, to suit a third operating condition. The initial part of the diffuser may be bladeless, an annular shockwave of cylindrical or frusto-conical form being produced, the velocity downstream of the shock-wave being supersonic but with a subsonic radial component.