354:, and a lower temperature of the intake charge results in a greater thermodynamic expansion and vice versa. A hot intake charge provokes detonation in a petrol engine, and can melt the pistons in a diesel, while an intercooling stage adds complexity but can improve the power output by increasing the amount of the input charge, exactly as if the engine were of higher capacity. An intercooler reduces the thermodynamic efficiency by losing the heat (power) introduced by compression, but increases the power available because of the increased working mass for each cycle. Above about 5 psi (35 kPa) the intercooling improvement can become dramatic. With a Roots-type supercharger, one method successfully employed is the addition of a thin
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marked for reference (slightly above a pressure ratio of 2.0 compared to atmospheric pressure). At 15 psi (100 kPa) boost, Roots blowers hover between 50% and 58%. Replacing a smaller blower with a larger blower moves the point to the left. In most cases, as the map shows, this will move it into higher efficiency areas on the left as the smaller blower likely will have been running fast on the right of the chart. Usually, using a larger blower and running it slower to achieve the same boost will give an increase in compressor efficiency.
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Boost is given in terms of pressure ratio, which is the ratio of absolute air pressure before the blower to the absolute air pressure after compression by the blower. If no boost is present, the pressure ratio will be 1.0 (meaning 1:1), as the outlet pressure equals the inlet pressure. 15psi boost is
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For any given Roots blower running under given conditions, a single point will fall on the map. This point will rise with increasing boost and will move to the right with increasing blower speed. It can be seen that, at moderate speed and low boost, the efficiency can be over 90%. This is the area in
572:), pulsation noise and turbulence may be transmitted downstream. If not properly managed (through outlet piping geometry) or accounted for (by structural reinforcement of downstream components), the resulting pulsations can cause fluid cavitation and/or damage to components downstream of the blower.
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curves. For a two-lobed rotor, the smaller generating circles are one-quarter the diameter of the larger. Real Roots blowers may have more complex profiles for increased efficiency. The lobes on one rotor will not drive the other rotor with minimal free play in all positions, so that a separate pair
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Roots blowers are typically used in applications where a large volume of air must be moved across a relatively small pressure differential. This includes low vacuum applications, with the Roots blower acting alone, or in combination with other pumps as part of a high vacuum system. One very common
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The volumetric efficiency of the Roots-type blower is very good, usually staying above 90% at all but the lowest blower speeds. Because of that, a blower running at low efficiency will still mechanically deliver the intended volume of air to the engine, but that air will be hotter. In drag racing
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Because rotary lobe pumps need to maintain a clearance between the lobes, a single stage Roots blower can pump gas across only a limited pressure differential. If the pump is used beyond its specification, the compression of the gas generates enough heat so that the lobes expand to the point that
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are all types of what are commonly described as blowers, however there is a distinction between a roots type supercharger which is a positive displacement pump "blower" with no internal volume reduction/pressure increase, and other types of supercharger such as the eccentric vane
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The Roots-type blower is simple and widely used. It can be more effective than alternative superchargers at developing positive intake manifold pressure (i.e., above atmospheric pressure) at low engine speeds, making it a popular choice for passenger automobile applications. Peak
342:, a compression operation will raise the temperature of the compressed output. Additionally, the operation of the compressor itself requires energy input, which is converted to heat and can be transferred to the gas through the compressor housing, heating it more. Although
548:) in between to cool the gas. The lack of oil on the pumping surfaces allows the pumps to work in environments where contamination control is important. The high pumping rate for hydrocarbons allows the Roots pump to provide an effective isolation between oiled
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applications, where large volumes of fuel are injected with that hot air, vaporizing the fuel absorbs the heat. That functions as a kind of liquid aftercooler system and goes a long way to negating the inefficiency of the Roots design in that application.
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The Roots-type blower may achieve an efficiency of approximately 70% while achieving a maximum pressure ratio of two. Higher pressure ratios are achievable but at decreasing efficiency. Because a Roots-type blower pumps air in discrete pulses (unlike a
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design does not incorporate any reduction in volume/increase in pressure as air or other fluid passes through, hence it can best be described as a blower rather than a supercharger unlike some other designs of "supercharger" such as cozette, centric,
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Rotary lobe blowers, commonly called boosters in high vacuum application, are not used as a stand-alone pump. In high vacuum applications, the boosters' pumping speed can be used towards reducing the end pressure and increasing the pumping speed.
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The term "blower" is commonly used to define a device placed on engines with a functional need for additional airflow using a direct mechanical link as its energy source. The term blower is used to describe different types of superchargers. A
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With a low increase in pressure, fans are commonly used to move substantial quantities of gas. They're typically employed for the circulation of air in buildings, machine ventilation, cooling equipment and other industrial applications.
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included a Roots-style blower in a patented engine design, making the Roots-type blower the oldest of the various designs now available. Roots blowers are commonly referred to as air blowers or PD (positive displacement) blowers.
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480:) and made by companies such as Sir George Godfrey and Partners who were still shipping increasing numbers into the 1960s, they were later superseded by air bleeds from jet engine compression stages.
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placed between the blower and the engine. Water is circulated through it to a second unit placed near the front of the vehicle where a fan and the ambient air-stream can dissipate the collected heat.
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along the rotor axes, which reduces pulsing in the input and output (this is impractical with two lobes, as even a slight twist could open up a free path through the supercharger at certain angles).
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can be achieved by about 2000 rpm. Unlike the basic illustration, most modern Roots-type superchargers incorporate three-lobe or four-lobe rotors; this allows the lobes to have a
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with a pair of meshing lobes resembling a set of stretched gears. Fluid is trapped in pockets surrounding the lobes and carried from the intake side to the exhaust.
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each using nitro-methane fuel and T/AD dragsters and TA/FC funny cars using alcohol fuel and Pro
Modified using methanol fuel in professional drag racing classes
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Blowers are capable of creating medium air pressure with moderate pressure levels. They are used in applications where the pressure need is higher than fans.
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are capable of pumping large volumes but, as they only achieve moderate compression, it is not uncommon to see multiple Roots blower stages, frequently with
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used Roots blowers to pump air to the rotor (chopper) so as to drastically increase its sound output through all pitch ranges. The most well known are the
500:. The smaller generating circles (red and blue) are one quarter the diameter of the larger generating circle (black). The rotor profile is the thick line.
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industrial application is in pneumatic conveying systems, the blower delivering a high volume of air for the movement of bulk solids through pipes.
652:, using exhaust compression to spin its turbine, and not a direct mechanical link, is not generally regarded as a "blower" but simply a "turbo".
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Compressors generate higher air pressures in industrial applications generally between 8 and 12 bars with less amount of air flow rates.
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use aftermarket GMC variants similar in design to the 71 series, but with the rotor and case length increased for added capacity;
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Roots blowers were used for cabin pressurisation in aircraft, initially being investigated immediately before WW2 (using the
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439:. The model name of these units delineates their size - the once-commonly used 4–71 and 6–71 blowers were designed for
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and the Eaton axial flow which have internal compression and are more correctly described as superchargers.
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466:, and ACA (now American Signal Corporation) Hurricane. These sirens are known as "supercharged sirens".
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Animation showing the flow direction through a three-lobe Roots blower with a slight twist to the rotors
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350:, superchargers may also benefit from the use of an intercooler. Internal combustion is based upon a
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729:"Positive Displacement Blowers (lobe, Roots, Screw) pressure & vacuum : Engineering Guide"
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A Roots blower with two-lobed rotors. Most real Roots blowers' rotors have three or four lobes. (
582:. Generalized blower efficiency map shows how a blower's efficiency varies with speed and boost.
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Roots blowers are also used in reverse to measure the flow of gases or liquids, for example, in
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334:. Of the three basic supercharger types, the Roots design historically possessed the worst
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which Roots blowers were originally intended to operate, and they are very good at it.
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and also the axial flow Eaton type supercharger which have internal "compression".
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vehicles, had a Roots-type blower; the two companies are not related.
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Accumulated heat is an important consideration in the operation of a
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The Roots-type blower is named after
American inventors and brothers
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The most common application of the Roots-type blower has been the
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Construction of a two-lobed cycloidal rotor. The red curve is an
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A variant uses claw-shaped rotors for higher compression.
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rotors, constructed of alternating tangential sections of
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divisions of
General Motors), which require some form of
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engines, with the blower being driven from the engine's
62:. Unsourced material may be challenged and removed.
742:"Sir George Godfrey and Partners (Holdings) Ltd".
664:, where Roots-type superchargers are used for T/F
392:, because there is no separate intake stroke.
273:, who patented the basic design in 1860 as an
281:and other industrial applications. In 1900,
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529:of gears provide the phasing of the lobes.
435:, which were adapted for automotive use in
346:are more commonly known for their use on
122:Learn how and when to remove this message
715:"Twin Screw vs. Roots | Kenne Bell"
516:The simplest form of a Roots blower has
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224:. Roots-type blowers are also used to
376:The Roots design was commonly used on
7:
396:. two-stroke diesel engine, used in
60:adding citations to reliable sources
704:. Bentley Publishers, 2001, p. 48.
25:
636:, Roots-type supercharger, and a
580:Roots supercharger efficiency map
464:Federal Signal Thunderbolt Series
27:A positive displacement lobe pump
689:http://www.airblowerservices.com
302:is visible at the front of this
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746:. 18 December 1961. p. 14.
47:needs additional citations for
1:
533:they jam, damaging the pump.
451:also use reproduction 6-71s.
443:diesels. Current competition
431:blowers for their industrial
429:General Motors Coach Division
508:A three-lobed Roots blower (
216:, such as those produced by
185:which operates by pumping a
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668:dragsters, F/C Fuel Coupe
556:, and the vacuum chamber.
407:The superchargers used on
332:internal combustion engine
773:Two-stroke diesel engines
378:two-stroke diesel engines
214:two-stroke diesel engines
638:centrifugal supercharger
554:rotary compression pumps
496:and the blue curve is a
484:Technical considerations
298:An Eaton M62 Roots-type
634:screw type supercharger
18:Roots-type supercharger
599:Comparative advantages
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203:Powerplus supercharger
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744:Birmingham Daily Post
691:, Air Blower Services
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478:Marshall supercharger
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271:Connersville, Indiana
222:Electro-Motive Diesel
199:Shorrock supercharger
180:positive displacement
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563:Roots efficiency map
460:civil defense sirens
380:(popularized by the
267:Roots Blower Company
263:Francis Marion Roots
56:improve this article
352:thermodynamic cycle
308:Saturn Ion Red Line
763:1860 introductions
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336:thermal efficiency
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265:, founders of the
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717:. 23 August 2017.
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304:Ecotec LSJ engine
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433:diesel engines
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218:Detroit Diesel
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67:Find sources:
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415:, and other
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344:intercoolers
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321:slight twist
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300:supercharger
290:Applications
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248:roller chain
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194:Roots blower
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176:Roots blower
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54:Please help
49:verification
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662:Drag racing
621:Compressors
498:hypocycloid
449:hot rodders
437:drag racing
425:derivatives
277:for use in
229:four-stroke
226:supercharge
757:Categories
677:References
552:, such as
494:epicycloid
471:gas meters
413:funny cars
328:compressor
306:in a 2006
252:gear train
236:crankshaft
232:Otto cycle
212:device on
82:newspapers
670:funny car
643:powerplus
518:cycloidal
445:dragsters
441:71 series
417:dragsters
259:Philander
210:induction
183:lobe pump
151:Pump body
666:top fuel
656:See also
421:hot rods
275:air pump
112:May 2014
615:Blowers
402:Karrier
240:toothed
164:Pumping
96:scholar
536:Roots
398:Commer
330:in an
317:torque
244:V-belt
238:via a
167:Output
161:Intake
144:) Key:
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550:pumps
538:pumps
458:Some
250:or a
187:fluid
178:is a
103:JSTOR
89:books
608:Fans
524:and
400:and
384:and
261:and
246:, a
220:and
192:The
174:The
75:news
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58:by
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