US3811807A - Rotary compressing,displacing or expanding machine - Google Patents

Rotary compressing,displacing or expanding machine Download PDF

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Publication number
US3811807A
US3811807A US00263095A US26309572A US3811807A US 3811807 A US3811807 A US 3811807A US 00263095 A US00263095 A US 00263095A US 26309572 A US26309572 A US 26309572A US 3811807 A US3811807 A US 3811807A
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United States
Prior art keywords
blades
lobes
casing
rotor
bore
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US00263095A
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English (en)
Inventor
D Tryhorn
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Sir WG Armstrong Whitworth and Co Engineers Ltd
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Sir WG Armstrong Whitworth and Co Engineers Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01C—ROTARY-PISTON OR OSCILLATING-PISTON MACHINES OR ENGINES
    • F01C1/00—Rotary-piston machines or engines
    • F01C1/30—Rotary-piston machines or engines having the characteristics covered by two or more groups F01C1/02, F01C1/08, F01C1/22, F01C1/24 or having the characteristics covered by one of these groups together with some other type of movement between co-operating members
    • F01C1/36—Rotary-piston machines or engines having the characteristics covered by two or more groups F01C1/02, F01C1/08, F01C1/22, F01C1/24 or having the characteristics covered by one of these groups together with some other type of movement between co-operating members having both the movements defined in sub-groups F01C1/22 and F01C1/24

Definitions

  • ABSTRACT A rotary fluid compressing displacing or expanding machine of the type in which lobes on a rotor rotate within a casing relative to blades which are rotatably mounted on the casing so as in sequence to form a barrier to the passage of fluid and by their rotation permit passing of the lobes to cause a continuous delivery of fluid in front of the lobes and intake of fluid behind the lobes.
  • an improved machine is characterized in that the tips of the blades sequentially form a sealing clearance with an inner surface of the casing which is concentric with the rotary axis and further in that'the blade thickness to width ratio is in the range of 0.4/N to 0.9/N where N is the number of blades.
  • the invention relates to rotary fluid compressing, displacing or expanding machines of the kind known as blade-type blowers and has been devised with the object of improving said machines by reducing their noise level and increasing the fluid displacement for a given casing diameter;
  • British Pat. No. 804,602 sets out the cycle of operation of this type of machine in which lobes mounted on a rotor rotate within a casing relative to blades which are rotatably mounted on the casing so as in sequence to form abarrierto the passage of air and by their rotation permit passing of the lobes to cause a continuous delivery of air in front of said lobes and intake of air behind said lobes.
  • Any part of the air circuit which forms a pipe amplifies noise when a pressure disturbance excites its natural frequency, and harmonics.
  • the tips of the bladessequentially forma sealing clearance with aninner surface of the casing which is concentric with the rotor axis and that the blade thickness to width ratio is in the range of 0.4/N to 0.9/N, where N is the number of blades.
  • the thickness of the blades is determined by the angle through which they turn over the period of the trapped volume and on the profile of the blade tip.
  • the gap between the lobes has a width sufficient to pass the hub part of the blades and since the tips approach this gap at an angle, the thickness is not truly uniform but tapers with reducing thickness towards the outside diameter of the blade.
  • the curvature of the blade may be approximate to the arc of the circle having a radius of 2d /t, where D is the pitch circle diameter of the blades and t is the tip thickness thereof. 7
  • a lowrate of pressure-increase in the trapped volume is achieved by keeping it sealed from the intake space for a period and permitting a controlled rate of leakage from the delivery space to raise the pressure.
  • the susceptibility of the blade to bending and vibrating also depends upon the method of mounting the blade. By use of a ring mounted on spacer pieces between the blades additional bearings can be mounted. This allows the .blades to be doubly supported instead of cantilever supported.
  • the invention thus may further provide for the blades to be supported at both ends. 7
  • Both these conditions can vbe avoided by eliminating the end disc of the rotor andhaving a rotor in the form of a bar having to one side of its rotation axis radially inner and outer lobes and to the opposite side of its rotation axis a plate which makes sealing clearance with the end of the blade which forms the barrier to the passage of fluid.
  • a duct which rotates with the rotor may separate the intake and delivery air flows.
  • FIG. 1 is a transverse section of the blower and the working space swept by the lobes
  • FIG. 2 is a longitudinal section on the line XYZ of FIG. 1, showing the air ducting and blade mounting.
  • the blower of FIGS. 1 and 2 comprises a cylindrical casing l in which runs concentrically a bar or anchor type rotor comprising an inner sealing hub 2 and a radial bar 3 which support a radially outer lobe 4, a radially inner lobe 5, and the radially inner and radially outer sealing plates 6 and 7 which seal the ends of the blades 8 when they contain between them the trapped air volume of a working space 9.
  • the thickness of these blades is such that there is always an effective seal on the bore of the casing between a delivery space 10 and an intake space 11.
  • a continuous seal must be obtained between the delivery and intake spaces at the lobes, and where the lobes pass from one blade tip to the next, concentric stationary spacing pieces 12 are used to fill the gaps between the blade tips.
  • the sealing plates 6 and 7 are preferably made to cover a larger arc than the trapped air volume 9. This gives a period of time over which compression takes place.
  • the rate of compression is controlled by the leakage around the blade on the delivery side and the rotor hub may be cut away at 13 to give the requisite leakage flow rate. It is more convenient however to have groove holes formed in the sealing plates 6 and 7 to yield this controlled increase in leakage compression.
  • FIG. 2 there is shown a ring 14 mounted on the spacing pieces 12 and which supports the blades 8 at their ends remote from the backplate 15. Further, the ring 14 runs in close fitting grooves between the lobes 4 and 5 and the two parts of the sealing plates 6 and 7.
  • the air intake from the casing 16 to the working space 11 is via a rotating duct 17 which maintains an air seal between the casing 16 and the casing 1.
  • the air is delivered from the working space to a delivery casing 18 round the outside of this rotating duct and thence to a delivery flange 19.
  • the design as described satisfies the object of the invention and provides a machine having a minimum of sources of noise in that:
  • the effective area causing displacement remains substantially constant. Also, the projected area of the rotating lobes remains constant so that if the projected area of the blades were also constant then the air flow into the machine would be steady.
  • a blade having a tip thickness 1 and diameter d to give a t/d ratio within the range of 1.4/N to 0.9/N where N is the number of blades and by suitable choice of the blade tip radius it is arranged that the projected area of the outer half of the blade does remain substantially constant.
  • the center hub the effective area causing displacement is low and small changes in projected area of the blades are acceptable because they cause little change in rate of the total air intake.
  • the implosion of air from the delivery space to the trapped volume is brought to a low level of intensity by making it take place over a long time period.
  • the rate of leakage is controlled by profiling one of the rotating surfaces which makes a seal on the blade, as depicted by the cut away part 13. To avoid too rapid an increase in leakage area, the blade tips tend to seal again towards the end of the part 13 to compensate for the rapid increase in leakage area at the outer blade tip.
  • the leakage compression period can be made equal to one quater of the blade separation angle or cyclic repeat time which in the machine of FIG. 1 is or four cycles per revolution and the compression period 22.5".
  • the trapping blade is subject to this rising pressure on one side and inlet pressure on the other. This causes bending of the blade and it is a feature of the design that the natural frequency of bending of the blade is high compared with the frequency of blade loading by compression pressure. It is to assist in achieving this feature that the blade is supported at both ends by the ring 14 as previously explained instead of by a cantilever arrangement.
  • vAir pressure disturbance can be reduced, but not eliminated. Eddy noises of air passing through the working clearances remain, even with steady flow. It is possible however, to reduce the amplification given to such noises, and other pressure changes, by not letting them excite air vibrations in pipes.
  • the inlet and delivery working spaces 11 and 10 are in full and continuous communication with the duct openings in the casings l6 and 19 via the rotating duct 17 and the delivery casing 18.
  • the anchor type rotor comprises a bar 3 supporting at one end the lobe 4 and at the other end the sealing plate 7 and being mounted on the driving shaft. This bar is narrow, so that it does not form an end wall to the working spaces. The thickness of this bar may be increased locally as weight to correct the dynamic balance of the lobes and sealing plates, as shown at 20 in FIGS. 1 and 2.
  • Each blade 8 is mounted on a shaft passing through the back plate 15 and provided with a gear 21 which engages an intermediate gear 22 itself engaging a gear 23 on the driving shaft of the machine.
  • the ratios of the gears are so chosen that each blade makes one revolution for each two revolutions of the driving shaft.
  • Other forms of reduction gear may be used to obtain this drive ratio.
  • the machine can be run as a compressor, as a displacing or metering device or as a motor.
  • the fluid flow may be reversed for a given rotation by turning the rotating duct 17 by relative to the rotor.
  • a fluid compressing, displacing or expanding machine comprising: a stationary casing having a cylindrical bore with a perpendicular end face, said casing having inlet and delivery openings disposed on the exterior thereof;
  • a rotor rotatably mounted in said casing and being co-axial with said bore, said rotor having a pair of radially aligned lobes disposed on one side of the rotor axis;
  • an outer one of said lobes being disposed closely adjacent the surfaceof said bore in said casing and an inner one of said lobes terminating in a sealing hub disposed on the opposite side of the rotor axis from said lobes; said lobes being spaced apart from one another to permitwidthwise passage of each blade and each stationary spacing piece as said rotor ro- .right angles to the radius of said bore on the side i of said rotor having lobes to provide a seal between the surface of said cylindrical bore and said sealing hub when in the former direction, and
  • passageways being rotatable with said rotor for the intake and delivery of fluid at opposite sides of said lobes and communicating with said inlet and delivery openings on the exterior of said casing.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)
  • Rotary Pumps (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
US00263095A 1971-06-17 1972-06-15 Rotary compressing,displacing or expanding machine Expired - Lifetime US3811807A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2842471A GB1370353A (en) 1971-06-17 1971-06-17 Rotary positive-displacement machine

Publications (1)

Publication Number Publication Date
US3811807A true US3811807A (en) 1974-05-21

Family

ID=10275428

Family Applications (1)

Application Number Title Priority Date Filing Date
US00263095A Expired - Lifetime US3811807A (en) 1971-06-17 1972-06-15 Rotary compressing,displacing or expanding machine

Country Status (7)

Country Link
US (1) US3811807A (fr)
CA (1) CA1001596A (fr)
DE (1) DE2229532C3 (fr)
FR (1) FR2142505A5 (fr)
GB (1) GB1370353A (fr)
IT (1) IT959170B (fr)
SE (1) SE389542B (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110986809B (zh) * 2019-12-23 2021-07-02 中车株洲电机有限公司 一种电机轴承装配径向游隙测量方法及装置

Also Published As

Publication number Publication date
GB1370353A (en) 1974-10-16
DE2229532A1 (de) 1973-04-19
DE2229532B2 (de) 1979-08-09
IT959170B (it) 1973-11-10
CA1001596A (en) 1976-12-14
DE2229532C3 (de) 1980-04-17
SE389542B (sv) 1976-11-08
FR2142505A5 (fr) 1973-01-26

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