Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/26—Rotors specially for elastic fluids
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D23/00—Other rotary non-positive-displacement pumps
  • F04D23/008—Regenerative pumps
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2250/00—Geometry
  • F05D2250/50—Inlet or outlet
  • F05D2250/51—Inlet
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
  • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
  • F05D2250/00—Geometry
  • F05D2250/50—Inlet or outlet
  • F05D2250/52—Outlet

Definitions

• This invention relates to regenerative rotodynamic machines, and more especially to regenerative compressors and exhausters.
• a regenerative or peripheral pump is a rotodynamic machine which permits a head equivalent to that of several centrifugal stages to be obtained from a single rotor with comparable tip speeds.
• the impeller can take the form of a disc with a set of flat vanes projecting axially at each side near the disc periphery. Around the greater portion of the periphery the vanes project into an annular channel of which the cross-sectional area is greater than that of the impeller vanes. Over a sector of limited extent between the inlet and discharge the annular channel is reduced to a close running clearance around the impeller. This sector is called the stripper seal and its function is to separate the inlet and discharge ports, thereby forcing fluid out through the discharge port.
• the stripper seal allows only the fluid between the impeller vanes to pass through to the inlet.
• the advantage of pumps of this type lies in the generation of a high head at low flow rates. They have a very low specific speed. ' Although their efficiency is not very high, pumps of this type have found many applications in industry where it is preferred to use rotodynamic pumps in place of positive displacement pumps for duties requiring a high head at low flow rates. Their simplicity, the low noise levels generated and the absence of problems due to lubrication and wear, give advantages over positive displacement pumps, despite the lower efficiency.
• the flat vane regenerative pump has been adapted for the compression of gas.
• the advantage lies in the low specific speed giving a high pressure ratio together with a low flow rate for a given size of machine. Further advantages are oil free operation and freedom from stall or surge instability.
• the gas follows a helical path through the annular channel and passes through the vanes a number of times in its peripheral path from the inlet port to the discharge port.
• Each passage through the vanes may be regarded as a stage of compression and thus the equivalent of several stages of compression can be obtained from a single impeller.
• this pumping process by means of flat vanes cannot be considered as efficient.
• the fluid between the vanes is thrown out and across the annular channel and violent mixing occurs, the angular momentum acquired by the fluid in its passage between the vanes being transferred to the fluid in the annular channel.
• the mixing process is accompanied by the production of a great deal of turbulence and this implies an undesirable waste of power.
• Senoo A.S.M.E. Trans. Vol. 78, 1956, pp. 1091 - 1102
• Senoo and Inversen A.S.M.E. Trans. Vol. 77, 1955, pp 19 - 28
• Senoo and Inversen considered turbulent friction between the moving impeller and the fluid as the primary force causing the pumping action.
• Wilson Santalo and Oelrich (A.S.M.E. Trans. Vol.
• Roots blower is an exceptionally noisy machine - therefore, design improvements to reduce noise will require a construction that is progressively less like a Roots blower; ii) The clearances between the moving parts are crucial to performance and must be maintained at a minimum in manufacture by expensive machining techniques, iii) The small clearances require special expensive precautions to be taken in choice of materials and manufacture in order to avoid the machine seizing with the considerable heat generated in operation, iv) High precision - fitting parts are also necessary to prevent radial leakages from the blade channel.
• a regenerative rotodynamic machine comprising a stator and a rotary impeller co-operating to define, adjacent the impeller periphery, a flow channel extending circumferentially to form an annulus coaxial with the impeller, the cross-section of the flow channel being circular except at the location of a stripper seal in the flow channel that separates an inlet and an outlet respectively for fluid entering and leaving the flow channel, a static annular core ring contained within the flow channel and coaxial with the flow channel and the impeller, the core ring having, except at the stripper seal, a substantially circular cross-section coaxial with the circular cross section of the flow channel, and a ring of curved aerodynamic blades on the impeller projecting into the flow channel into close proximity with the core ring, the aforesaid components being adapted to be manufactured for assembly as die-cast parts.
• Figure 1 is a view of a compressor according to the invention, in axial section on the line 1-1 of Figure 2,
• Figure 2 is an external elevation of the compressor in the direction of the arrow 2 of Figure 1,
• Figure 3 is a partial view in section on the line 3-3 of Figure 2 showing the stripper seal of the compressor
• Figure 4 shows velocity diagrams for the impeller blades of a compressor of this kind.
• Figure 5 is a diagrammatic cross-section through the blade channel of the compressor at the region of the inlet port.
• Figure 6 is a view in section on the line 6-6 of Figure 5,
• Figure 7A is a diagram of the blade channel in the region of the outlet port.
• Figure 7B is a diagram showing velocity distributions at the region of the outlet.
• Figure 8 is a plot of comparative curves for adiabatic efficiency
• Figure 9 is a diagram of blade profiles
• Figure 10 is a diagram useful in determining the cross-section geometry for the flow channel and the core ring.
• FIG. 1 shows a regenerative rotodynamic compressor according to the invention consisting primarily of a rotary impeller 10 inside a stator or casing 11.
• the stator defines internally a circular impeller chamber 12 which, at one side, is in communication around its peripheral margin with an annular channel 13 of circular cross-section that is offset axially with respect to the impeller chamber 12.
• the side-wall 12A of the impeller chamber has a large central bore 14 in which is disposed a rotary flange 15 at the end of a drive-shaft 16, to which flange the impeller 10 is bolted by bolts 15A.
• the drive-shaft 16 is supported in a roller bearing 21 and ball bearings 22, 23 housed within a stationary sleeve 17 which extends axially away from the side-wall 12A and is held rigid with the casing 11 by a spider of circumferentially spaced axial webs 18 that extend both radially outwards and also axially from the side-wall 12A almost to the remote end of the sleeve 17.
• the outer races of the bearings 21, 22, 23 are located in a liner 19 fitted within the sleeve 17; the inner races on the shaft 16 are located by a shoulder 16A on the shaft and spacers 16B, and are retained by a nut 16C.
• the drive-shaft 16 projects beyond the end of the sleeve 17 and liner 19 and has a shaft key 24 on its external end for coupling to a drive motor (not shown) .
• the casing 11 is split into two parts at a stepped radial plane indicated at 25.
• One part 11A therefore comprises the right-hand wall (as seen in Figure 1) of the impeller chamber and a peripheral flange that provides the circumferential wall of the impeller chamber and is also internally profiled, as at 26, to provide a portion of the wall at the right-hand side of the blade channel 13.
• the other part 11B comprises the left-hand wall 12A of the impeller chamber, the left-hand half of the blade channel 13, the spider 18, the sleeve 17 and an integral inlet/outlet port block 28. Both these parts are designed for easy manufacture by die-casting and are secured together by bolts 31.
• the remainder of the blade channel 13 is formed by a separate profiled insert ring 27, also a die-casting, that fits on to and around the step that is present on the part 11B due to the stepped plane 25 and is profiled at its outer circumference, as at 29, to provide a sector of the blade channel circular cross-section, as shown.
• This ring is secured in place by screws 30.
• There remains a gap in the blade channel circular section where it communicates with the impeller chamber 12 and through which a ring of blades 32 on the side of the impeller 10 around its peripheral margin project into the blade channel 13.
• Concentric with the blade channel is a static annular core ring 33 which is of circular cross-section except for a flat 34 directed toward the impeller blades 32.
• the core ring is split at its maximum diameter on a plane 35 radial to the axis of the machine so that it can be readily manufactured as two die-castings and it is largely hollow, to reduce weight, as indicated as 33 , but with blocked portions 37 provided at circumferential intervals to receive screws 36 for securing the two parts together.
• blocked portions 37 provided at circumferential intervals to receive screws 36 for securing the two parts together.
• pegs 38 projecting radially inward from the blocked portions 37 whereby the core ring is secured in place, these pegs being clamped by the profiled insert ring 27.
• the impeller 10 and the blades 32 are designed for die-casting as one integral part.
• the opposite faces of the impeller are 'scalloped' with sectoral bands 41 alternating with sectoral recesses 42; this removes mass while giving high resistance to distortion under heat.
• the removal of mass in this way is highly beneficial in that the machine can be started by its synchronous driving motor without the need for either a separate high starting torque starter motor or an unloading device to relieve fluid pressure on starting, as typically used in the case of a Roots type positive displacement machine.
• the blades on the impeller are curved in the radial plane of the impeller, being concave and convex, respectively, at their leading and trailing surfaces, and they are aerodynamic in that they have aerofoil profiles in which the thickness of the blade varies across its chord. It can also be seen in Figure 1 that the chord of the blades narrows toward their extremities, so that at the blade extremities the chord dimension matches that of the flat 34 on the core ring.
• Velocity diagrams for the impeller blades are given in Figure 4, the blades here being shown stylised and not in actual profile. In the diagrams, the angle ⁇ - + ⁇ 2 through which the fluid is turned at each blade is shown as 90°; the angle should be at least this and the best angle appears to be 90.25°.
• Such blades are intended to be driven at a nominal speed of
• N rotational speed (rev/min) and in any event, the number should be less than:-
• the correct rounded blade profile should be achieved.
• FIGs 5 and 6 are diagrams of the inlet port.
• a baffle plate 44 is provided to guide the fluid entering the inlet 43 more efficiently into the machine and this gives a significant improvement in adiabatic efficiency.
• This baffle extends from the radially inward surface of the core ring 33 out into the inlet 43, where it lies against the adjacent side surface of the inlet, and it can be cast integral with the core ring.
• FIG. 7A is a diagram of the blade channel at the region of the outlet port 45.
• the exit angle ⁇ is the angle between the axis of the outlet passage 45A and the radial line through the rotational axis of the machine that passes through the intersection point of the outlet passage axis and the circle that defines the centre axis of the annular flow channel.
• an exit angle ⁇ of 50" - 90 preferably 70°, is beneficial for high pressure ratios across the machine and, in addition to setting the exit passage of the outlet port at the appropriate angle, a baffle 46 may be provided, ahead of the stripper seal 40, to give the correct angle to discharge the fluid most efficiently into the outlet port. Again this baffle can be cast integral with the core ring.
• FIG. 7B illustrates the effect of changes in rotational speed upon-the velocity distribution across the flow channel. As can be seen, there may be a negative velocity or reverse flow in the radially inner region of the flow channel at low speeds.
• the machine is designed to minimise heat transfer to the shaft bearings, with air space 48 between the bearing sleeve 17 and the machine casing and impeller. If desired, stirrer blades can be cast on the back of the impeller mounting flange 15 to promote the circulation of cooling air.
• Figure 8 shows comparative curves of adiabatic efficiency plotted against pressure for different speeds of rotation.
• the full line curves illustrate what can be achieved with the present machine as compared with the curves shown in broken lines for the best prior art regenerative rotodynamic machine.
• the blades shown in Figure 4 are stylised and do not represent the actual blade profiles employed. Suitable blade profiles are shown in Figure 9.
• N rotational speed (rev/min) .

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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• 1987
  • 1987-12-31 GB GB878730341A patent/GB8730341D0/en active Pending
• 1989
  • 1989-01-03 KR KR1019890701381A patent/KR900700761A/ko not_active Application Discontinuation
  • 1989-01-03 JP JP1501528A patent/JPH02503815A/ja active Pending
  • 1989-01-03 AU AU30328/89A patent/AU3032889A/en not_active Abandoned
  • 1989-01-03 GB GB8912854A patent/GB2231090A/en not_active Withdrawn
  • 1989-01-03 EP EP89901728A patent/EP0346456A1/en not_active Withdrawn
  • 1989-01-03 BR BR898904541A patent/BR8904541A/pt unknown
  • 1989-01-03 WO PCT/GB1989/000014 patent/WO1989006318A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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