US20120195783A1 - Noise and shock reduction in rotary positive displacement blowers - Google Patents

Noise and shock reduction in rotary positive displacement blowers Download PDF

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Publication number
US20120195783A1
US20120195783A1 US12/931,093 US93109311A US2012195783A1 US 20120195783 A1 US20120195783 A1 US 20120195783A1 US 93109311 A US93109311 A US 93109311A US 2012195783 A1 US2012195783 A1 US 2012195783A1
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United States
Prior art keywords
housing
blower
rotor
chamber
discharge
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Abandoned
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US12/931,093
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English (en)
Inventor
Erich R. Fitzpatrick
Michael R. Buis
Charles R. Jones, Jr.
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Tuthill Corp
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Tuthill Corp
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Priority to US12/931,093 priority Critical patent/US20120195783A1/en
Assigned to TUTHILL CORPORATION reassignment TUTHILL CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: Buis, Michael R., FITZPATRICK, ERICH R., JONES, CHARLES R. JR.
Publication of US20120195783A1 publication Critical patent/US20120195783A1/en
Priority to US15/050,651 priority patent/US20160245287A1/en
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00—Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/08—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
    • F04C18/12—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
    • F04C18/126—Rotary-piston pumps specially adapted for elastic fluids of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type with radially from the rotor body extending elements, not necessarily co-operating with corresponding recesses in the other rotor, e.g. lobes, Roots type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
    • F04C29/06—Silencing
    • F04C29/065—Noise dampening volumes, e.g. muffler chambers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
    • F04C29/06—Silencing
    • F04C29/068—Silencing the silencing means being arranged inside the pump housing
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2240/00—Components
    • F04C2240/30—Casings or housings

Definitions

  • the invention relates to rotary positive displacement blowers (of the Roots type) and, more particularly, to a back-pass loop for gradually pressurizing the working cell to outlet pressure in order to weaken the strength of the pulsations that would otherwise happen without such a back-pass loop, and thereby reduce noise and shock (and perhaps better efficiency as well).
  • blowers are typically measured (or specified) in terms of the following factors:—flow, pressure, efficiency, noise, and reliability.
  • blowers of this type can be built to all kinds of sizes (including very large). Hence design flow rate is an operating point that is scalable over a wide range.
  • the operating pressure differential ( ⁇ p) across such blowers might typically vary under the circumstances between very slight (eg., 1 to 2 psi or ⁇ 1/15th to 2/15th atm) to something typical (eg., 15 psi or ⁇ 1 atm). It might be just as typical that a blower of this type be rated for up to 18 psi duty ( ⁇ 1 3/15ths atm pressure differential).
  • some end-use applications may require that the discharge line supply flow at a pressure as high as 100 psig ( ⁇ 72 ⁇ 3rds atm). To do this, the pressure in the inlet line has to be elevated to within 18 psi ( ⁇ 1 3/15ths atm pressure differential) or less of the target pressure for the discharge line.
  • the Acoustic Air blower introduced some matters in blower design which have been changed, substantially or so, here for better meeting the objects of the invention. These changes fall under two major categories.
  • One major category comprises changes in design for purely or substantially pneumatic reasons.
  • the other major category comprises changes in design for purely or substantially ease of manufacture reasons.
  • an object of the invention for the Acoustic Air design included reducing pressure pulsations, and thereby reducing resulting noise and vibration.
  • the Acoustic Air design sought to do this by the following two ways.
  • a backflow loop is meant to gradually pre-pressurize a low-pressure closed cell (eg., 64 or 66 ) so that when the closed cell (eg., 64 or 66 ) opens across an edge 78 or 80 into the higher-pressure discharge chamber 46 , the backflow loop eliminates or weakens the direct backflow from the discharge chamber 46 into the opening closed cell (eg., 64 or 66 ).
  • the backflow from the discharge chamber 46 flows directly into the opening closed cell (eg., 64 or 66 ) and is the source of the sonic pop (eg., the noise) as well as the momentary opposition to the rotation of the rotors 50 , 52 (eg., the vibration).
  • the Acoustic Air blower has backflow chambers 106 , 108 , 120 , 122 filled by backflow ports 112 , 116 , 126 , 130 and for pre-pressurizing fluid in the sealed pocket (eg., 64 , 66 ) by injector ports 110 , 114 , 124 , 128 .
  • the patent contains this remark on the effectiveness of this design.
  • FIG. 1 is a perspective view of a rotary positive displacement blower with noise and shock reduction improvements in accordance with the invention
  • FIG. 2 is an exploded view thereof
  • FIG. 3 is an enlarged scale detail view of the rotor chamber and discharge plenum in FIG. 2 ;
  • FIG. 4 is a vertical sectional view taken through the rotary positive displacement blower of FIG. 1 , taken perpendicular to the plane of the rotor axes, and, taken along an offset plane to contain not only the centerline of one inner port(s) in the rotor chamber (as well as portions thereabove), but also, the centerline of one (of the two) outer port(s) in the discharge plenum (as well as portions therebelow); and
  • FIG. 5 is a chart showing the effect of back-pass manifold chamber volume on the fluctuation away from mean discharge flowrate.
  • FIGS. 1 through 4 provide line drawings of a rotary positive displacement blower 210 with noise and shock reduction improvements in accordance with the invention. It is an aspect of the invention to incorporate a pair of back-pass manifolds 212 .
  • FIG. 4 shows better that, it has a substantially hollow housing 214 defining an inlet plenum 220 , a rotor chamber 224 , and a discharge plenum 228 .
  • the housing 214 is cast, but the flange surfaces would be machined and ground.
  • a pair of rotors 230 are disposed in the rotor chamber 224 .
  • the rotors 230 would be sealed inside by a pair of opposed end plates (far side end plates shown in FIGS. 1 and 2 ).
  • the rotors 230 are driven to rotate counter-rotationally to each other. For instance, the left rotor 230 rotates counter-clockwise (CCW).
  • blower 210 is shown with the inlet port 220 P up and the discharge port 228 P down.
  • the blower 210 can be mounted in any orientation, and accordingly, terms like “up” and “down”, “left” and “right” are used merely for convenience in this description and do not limit the installation of the blower 210 to any particular orientation.
  • the rotors 230 are identical. Each rotor 230 comprises three lobes 232 . Each lobe 232 culminates in a tip 232 T. The lobes 232 are spaced by pockets 240 .
  • the inlet plenum 220 transitions into the rotor chamber 224 at a pair of spaced ledges 242 L, and these define an inlet opening 242 for the blower 210 .
  • the rotor chamber 224 transitions into the discharge plenum 228 at another pair of spaced ledges 244 L, and these define a discharge opening 244 for the blower 210 .
  • FIG. 4 shows that the left rotor 230 's upper lobe tip 232 T is about to sweep (counterclockwise) past the left ledge 242 L of the inlet opening 242 .
  • each pocket 240 in turn will form the temporarily existing closed cell 240 X, successively, and in an endless succession.
  • the trapped gas is carried around in the closed cell 240 X, from the inlet plenum 220 to the discharge plenum 228 , at the pressure of the inlet plenum 220 while being carried around like that. In contrast, the trapped gas will be ultimately discharged into the discharge plenum 228 , at the pressure of the discharge plenum 228 .
  • the closed cell 240 X opens to discharge space.
  • noise eg., an audible sonic pop or snap, something akin to a popping balloon or snapped cell of bubble wrap
  • the reverse flow is a problem of its own.
  • the reverse flow creates an opposing force in opposition to the turning rotors 230 , and the rotors 230 have to power through the reverse flow.
  • the reverse flow is a readily identifiable source of inefficiency.
  • the reverse flow also has another effect, which is likewise detrimental, which is that of causing mechanical shock through the blower (vibration), and not just to the blower's castings but also to the joints, couplings, bearings, seals and so on.
  • the reverse flow comprises a pulsing phenomenon. That is, for each revolution of the rotors 230 , there are six reverse flow events.
  • the rotors 230 are typically driven at 1200, 1800 or 3600 RPM. At the high value given there, that corresponds to 1.3 million reverse flow pulses—each hour.
  • the effects of reverse flow comprise an unceasing hammering on the blower, and over its whole lifetime. Accordingly, it is an object of the invention to not just weaken but eliminate each reverse flow event. It is a further object of the invention to reduce vibration, and not so much the frequency of the vibration but the shock value (amplitude) of each pulse. It is a corresponding object of the invention to enhance reliability.
  • a rotary positive displacement blower 210 (of the Roots type) with a back-pass loop 250 - 52 for gradually pressurizing the closed cell 240 X to the pressure of the discharge plenum 228 in order to weaken the strength of the pulsations that would otherwise happen, and thereby reduce noise and shock.
  • FIGS. 1 and 4 show a rotary positive displacement blower 210 provided with a pair of flanking manifolds 212 .
  • both manifolds 212 are shown dismounted and apart from the main housing 214 .
  • both manifolds 212 are shown mounted to the main housing 214 .
  • main housing 214 is a monolithic casting of (preferably) steel, so is each manifold 212 its own separate monolithic casting of steel.
  • the flange surfaces for the bolt-on surfaces are preferably ground very smooth, as are the mating surfaces on the main housing 214 .
  • FIGS. 1 and 2 allow discernment that the manifolds 212 mount to the main housing 214 by a pattern of bolts (bolts not shown). Each manifold 212 defines a back-pass chamber 250 .
  • the main housing 214 is bored through from both sides in order to form a number of channels 251 and 252 for connecting each back-pass chamber 250 into a back-pass loop 250 - 52 with the blower 210 . That is, the main housing 214 is bored through a series of times into each side of the rotor chamber 224 to form a pattern—a line parallel with the axis of the rotor 230 —of inner channels 251 to the rotor chamber 224 .
  • the main housing 214 is furthermore bored through two times into each side of the discharge plenum 228 to form a pattern of (eg., two in-line) outer channels 252 (‘outer’ relative to the rotor chamber 224 ).
  • FIG. 3 shows better the ports 251 P and 252 P of the inner and outer channels 251 and 252 , respectively, in the rotor chamber 224 and discharge plenum 228 , respectively.
  • the cumulative cross-sectional flow area for the two outer channels 252 feeding one manifold 212 chamber 250 equals or is substantially close in value to the cumulative cross-sectional flow area of all the inner channels 251 serving the same manifold 212 chamber 250 .
  • the ratio of the cumulative cross-sectional area of the outer channels 251 to that of the inner channels 251 is about one to one (1:1).
  • FIG. 4 shows better that the flow axis of gas through the blower 210 is generally perpendicular to the plane containing the rotor axes.
  • This plane that contains the rotor axes
  • This plane is referred to herein for convenience sake as the rotor plane.
  • the dowel plane (It might alternatively be referred to as the dowel plane.
  • FIG. 1 shows better, it is typical that a housing 214 for a Roots blower would contain a pair of flanking dowels 255 in this same plane. These dowels 255 provide for alignment to the end plates and support to the housing 214 in this plane, and hence promote proper lobe tip 232 T clearance.)
  • the manifolds 212 mount to the main housing 214 on the discharge side of the rotor plane.
  • FIG. 4 allows reckoning of the following matters.
  • the lobes 232 of the rotors 230 are angularly spaced apart by 120°.
  • the ledge 242 L of the inlet opening 242 and the ledge 244 L of the discharge opening 244 are angularly spaced apart by about 180° (relative to rotor rotation).
  • the temporarily existing closed cell 240 X is formed for a time period corresponding to a 60° arc of the rotor rotation.
  • the design in accordance with the invention was obtained by virtual prototyping with the use of three-dimensional CFD software from SIMERICS, INC., that goes by the brand name PUMPLINX®.
  • the CFD analysis was performed with an existing blower of TUTHILL VACUUM & BLOWER SYSTEMS, model QX-3208, serving as the basis for blower dimensions.
  • the operating point for the analysis was chosen to be 3600 RPM at 15 psi ( ⁇ 1 atm pressure differential).
  • the prototype blower 210 in accordance with the invention compares to the un-modified original QX-3208 as follows. There was 8.9 db drop and a 12.4 dBA drop in sound pressure levels. There was an average drop across all tested speeds and pressures of 7.4 dB and 10.7 dBA. The maximum sound pressure level drop was 3600 RPM and 18 psi ( ⁇ 1 3/15ths atm differential pressure) for both linear and A-weighted scales. These results were 13.2 dB and 17.1 dBA respectively.
  • blower 210 in accordance with the invention is not just merely a quieter jack hammer, it has sort of lost its jack hammer staccato to where it just sounds like the hum of process machinery.
  • the improved blower 210 was prototyped out of a stock QX-3208 blower of TUTHILL BLOWER & VACUUM SYSTEMS.
  • the casting of the stock blower had to be beefed up in the regions where the inner and outer channels 251 and 252 were to be drilled, as well as where the manifolds 212 bolt on.
  • the manifold 212 is its own casting.
  • the backflow chambers were cast to size in the main housing casting for the blower.
  • the method of manufacture of the blower 210 with its separate cast manifolds 212 allowed much more flexibility in specifying different sizes and arrangements of inner and outer channels 251 and 252 as well a volume of the manifold 212 chambers 250 .
  • the second important factor is the cumulative flow area of the inner channels 251 .
  • the cumulative flow area is selected to fill the closed cell 240 X with about 100% plus of the make-up mass of air in the angular time that the inner channels 251 are filling the closed cell 240 X (eg., about 30° to 40° angular degrees).
  • the outer channels 252 cumulatively form about the same cross-sectional flow area for each manifold 212 chamber 250 as do the inner channels 251 therefor.
  • the inner channels 251 cannot be undersized or else there will be backflow when the leading lobe tip 232 T of the closed cell 240 X crosses the discharge ledge 244 L. Conversely, the inner channels 251 cannot be grossly oversized or else it just moves the moment of backflow from • when the leading lobe tip 232 T of the closed cell 240 X crosses the discharge ledge 244 L to • when leading lobe tip 232 T of the closed cell 240 X crosses the inner channels 251 . In sum, the inner channels 251 have to fill gradually, and do so all the way until the leading lobe tip 232 T of the closed cell 240 X crosses the discharge ledge 244 L, and then for a little while longer too.
  • the third important factor is a series of factors, and comprises the angle of attack angle of, and like matters concerning the inner channels 251 .
  • the angle of attack of the inner channels 251 is preferably is as close to a tangent line with the curve of the rotor chamber 224 and blowing onto the backside of the leading lobe tip 232 T of the closed cell 240 X as it crosses the inner channels 251 .
  • a prototype was built and tested where there were a series of inner channels 251 on three lines. It is believed from that experiment that closed cell 240 X wants to open all the inner channels 251 on one line that is parallel to the rotor axes.
  • the inner channels 251 preferably comprise a series of same diameter bore holes equally spaced from one another and generously distributed along the axial length of the closed cell 240 X in order to fill the closed cell 240 X in an axially even fashion.
  • the fourth most important factor is a timing factor.
  • the pressure in the discharge plenum 228 oscillates.
  • the back-pass loop 250 - 252 goes a long way to dampening the fluctuations. But it does not flatten the fluctuations to zero. Indeed, modest to mild fluctuations are a good thing.
  • the pressure fluctuations are propagated at the plane of the discharge ledges 244 L and move down (or away in) the discharge plenum until eventually the pressure fluctuations have moved so far away from the plane of the discharge ledges 244 L that they have canceled each other out into a mean pressure (with no fluctuations). But near the plane of the discharge ledges 244 L, there are measurable fluctuations.
  • the timing issue relates to where to locate the outer channels 252 relative to the plane of the discharge ledges 244 L.
  • FIG. 4 illustrates where the outer channels 252 should be located. Given the right side of FIG. 4 , it is preferred that a maximum of pressure fluctuation in discharge plenum 228 (even though propagated at the plane of the ledges 244 L) should reside at the plane of the outer channels 252 when the closed cell 240 on the right rotor 230 is about to cross the ledge 244 L. That way, the manifold 212 chamber 250 is pulling mass out of the discharge plenum 228 at the moment the closed cell 240 is about to blow out across the discharge ledge 244 L, which will be experiencing a local minimum in the pressure fluctuation.
  • the timing can be managed such that the opening closed cells 240 / 240 X never experience backflow when crossing the ledges 244 L.
  • the fifth factor is left for last perhaps because its range was most elusive. That is, it has been inventively discovered that the effectiveness of the blower 210 in accordance with the invention is sensitive to the ratio of closed cell 240 X volume to manifold 212 chamber 250 . Moreover, it is believed to be highly preferable that there be one dedicated manifold 212 chamber 250 pursuant to each rotor 230 . In contrast to the fourth factor above, the measure of performance here has to do with flow fluctuations.
  • FIG. 5 is a chart showing the effect of back-pass manifold 212 chamber 250 volume relative to volume of the closed cell 240 X on the fluctuation away from mean discharge flowrate.
  • FIG. 5 shows that the best performance is obtained when manifold 212 chamber 250 volume relative to closed cell 240 X volume is 100% (eg., the volumes are equal, or, there is one-to-one correspondence.
  • the fluctuation as a percentage of flowrate discharge is 12.8%. That means that, if the mean discharge centerline flowrate is 100 feet per second ( ⁇ 30 m/s), then the fluctuations in the flowrate are between about 93 feet per second ( ⁇ 28 m/s) and 107 feet per second ( ⁇ 32 m/s).
  • FIG. 5 shows that when manifold 212 chamber 250 volume as a percentage of closed cell 240 X volume is any of the following three values:—
  • the manifold 212 chamber 250 volume as a percentage of closed cell 240 X volume should fall between about 56% and 117% in order to obtain the preferred performance of the blower 210 .
  • the back-pass loop 250 - 52 weakens the pulsations by having an out-of-phase flow with chambers 250 comparable in volume to the closed cell 240 X.
  • blower 210 in accordance with the invention from conventional stock housings, except modified to accept the inventive manifolds 212 .
  • a preferred method of manufacturing a roots-style positive displacement blower 210 with a back-pass loop 251 - 252 comprises come of the following steps.
  • a housing 214 is provided, and it is highly preferred if the housing is a monolithic casting.
  • the housing 214 has a rotor chamber 224 portion, an inlet plenum 220 portion defining an inlet plenum 220 and a discharge plenum 228 portion.
  • the rotor chamber 224 portion defines a rotor chamber 224 comprising side-by-side left and right cylindrical cavities partially overlapping one another and meeting at tangent lines.
  • the left and right cylindrical cavities receiving the left and right rotors 230 such that the rotor axes define a rotor plane.
  • the discharge plenum 228 portion comprises a bell shape extending along an axis that projects away from the rotor plane. More preferred still is if the axis of the bell shape is perpendicular to the rotor plane.
  • the bell shape defines a discharge plenum 228 extending between a discharge opening 244 in the rotor chamber 224 and a discharge port 228 P.
  • the housing 214 is formed with left and right flange interfaces on the rotor chamber 224 portion of the housing 214 . Preferably this is done by surface machining followed by grinding.
  • the housing 214 is furthermore formed with left and right inner channels 251 in the rotor chamber 224 portion of the housing 214 that extend between interior ports 251 P in the left and right cylindrical cavities respectfully, and exterior ports in the left and right flange interfaces on the rotor chamber 224 portion of the housing 214 .
  • the housing 214 is preferably formed with left and right flange interfaces of the discharge plenum 228 portion of the housing 214 , again as by surface machining and grinding. Then, the housing is formed with left and right outer channels 252 in the discharge plenum 228 portion of the housing 214 , which extend between interior ports 252 P in the left and right sides respectively of the discharge plenum 228 , and exterior ports in the left and right flange interfaces of the discharge plenum 228 portion of the housing 214 .
  • these covers 212 concurrently seal over the exterior ports of the inner and outer channels 251 and 252 , respectively, and allow a back-pass flow therebetween underneath said covers 212 .
  • the flange interfaces on the rotor chamber 224 portion of the housing 214 that they are further outboard from the axis of the discharge plenum 228 than the flange interfaces of the discharge plenum 228 portion of the housing 214 . That way, the covers 212 might be L-shaped and still function sufficiently as covers 212 .
  • the ‘covers’ 212 are not just simply L-shaped by comprise a monolithic casting in a tubular C-shape.
  • the ‘covers’ given the tubular C-shape might interchangeably be referred to as manifolds 212 .
  • the manifolds 212 extend between a first interface for mating to the flange interfaces of the discharge plenum 228 portion of the housing 214 and a second interface for mating to the flange interfaces of the rotor chamber 224 portion of the housing 214 .
  • Each manifold 212 furthermore defines a back-pass chamber 250 which allows the back-pass flow between the inner and outer channels 251 and 252 . It is an aspect of the invention that the manifolds 212 are removably attached to the housing 214 by mechanical fastening.
  • each manifold 212 expands from being relatively narrower at the first interface to being relatively wider at the second interface.
  • being relatively narrower and wider is taken in context along axes parallel to the rotor axes.
  • the left inner channels 251 comprise a series of bore holes axially spread apart on an axis parallel to the rotor axes (the right inner channels 251 comprise symmetric opposites of the left inner channels 251 ).
  • the left outer channels 252 comprise at least two bore holes axially spread apart on an axis parallel to the rotor axes (right outer channels 252 would be symmetric opposites of the left outer channels 252 ). That way, the spread of the manifold 212 could accommodate the spread apartness of the inner channels 251 .
  • the left inner channels 251 define a cumulative flow area fairly close in size to the cumulative flow area defined by the left outer channels 252 .
  • inventive housing 214 is modified from conventional stock housings.
  • Conventional stock housing are characterized by many design aspects, including without limitation that the discharge plenum 228 portion of the housing 214 further comprises a circular ANSI flange encircling discharge port 228 P, and the bell shape comprises a six-sided subtended diamond-shaped bell flare.

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  • General Engineering & Computer Science (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)
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CN105485020A (zh) * 2016-01-20 2016-04-13 珠海格力电器股份有限公司 一种压缩机及其吸气端盖
US20170167362A1 (en) * 2013-10-31 2017-06-15 Eaton Corporation Thermal abatement systems
US20220145885A1 (en) * 2020-11-12 2022-05-12 Ingersoll-Rand Industrial U.S., Inc. Positive displacement roots blower noise suppression
CN115773243A (zh) * 2022-12-08 2023-03-10 西安交通大学 一种应用于燃料电池汽车系统的罗茨氢泵

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US2513446A (en) * 1946-05-17 1950-07-04 Brown And Brown Pump or motor
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US5090879A (en) * 1989-06-20 1992-02-25 Weinbrecht John F Recirculating rotary gas compressor
US5439358A (en) * 1994-01-27 1995-08-08 Weinbrecht; John F. Recirculating rotary gas compressor
US5702240A (en) * 1995-05-05 1997-12-30 Tuthill Corporation Rotary positive displacement blower having a diverging outlet part
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EP2348217A2 (fr) 2011-07-27

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