The Science Of Boost
687,091
Published 2020-12-01
ROOTS SUPERCHARGER
In 1859 two brothers Philander Higley Roots and Francis Marion Roots founded The Roots Blower Company in Connersville, Indiana.
Roots superchargers operate by pumping air with a pair of meshing lobes resembling a set of stretched gears. The incoming air is trapped in pockets surrounding the lobes and carried from the intake side to the exhaust of the blower.
TWIN-SCREW SUPERCHARGERS
In 1935, Swedish engineer Alf Lysholm patented a new air pump design as well as a method for its manufacture that improved upon the limitations of Roots blowers. Lysholm had replaced the lobes with screws, creating the rotary-screw compressor.
CENTRIFUGAL SUPERCHARGERS...
INTERCOOLERS
Forcing more air into a cylinder with boost easily creates more power in an engine by increasing the air mass of the intake charge beyond what is possible with natural aspiration. This also inherently pushes volumetric efficiency well beyond 100%
Because forced induction occurs outside of the engine the properties of the air mass can be further enhanced by cooling, by passing the compressed air through a heat-exchange device known as an intercooler.
TURBOCHARGERS
In some extreme cases, it can take as much as ⅓ of the base engine's power to drive the supercharger to produce a net gain in power.
The first turbocharger design was patented in 1905 by Swiss Engineer Alfred Büchi. He had conceptualized a compound radial engine with an exhaust-driven axial flow turbine and compressor mounted on a common shaft.
Turbochargers work by converting the heat and kinetic energy contained within engine exhaust gases, as they leave a cylinder. Radial inflow turbines work on a perpendicular gas flow stream, similar to a water wheel.
This shaft is housed within the center section of a turbocharger known as the center hub rotating assembly. Not only must it contain a bearing system to suspend the shaft spinning at 100,000s of RPMs, but it must also contend with the high temperatures created by exhaust gases.
In automotive applications, the bearing system found in most turbochargers are typically journal bearings or ball bearings. Of the two, journal bearings are more common due to its lower costs and effectiveness. It consists of two types of plain bearings; cylindrical bearings to contain radial loads and a flat thrust bearing to manage thrust loads.
Turbine aspect ratio - This is the ratio of the area of the turbine inlet relative to the distance between the centroid of the inlet and the center of the turbine wheel.
Compressors Trim -This is the relationship between the compressor wheels’ inducer and exducer diameter.
WASTEGATES
In order to prevent safe pressures and speeds from being exceeded, a mechanism called a wastegate is employed. Wastgates work by opening a valve at a predetermined compressor pressure that diverts exhaust gases away from the turbine, limiting its rpm. In its most common form, wastegates are integrated directly into the turbine housing, employing a poppet type valve. The valve is opened by boost pressure pushing a diaphragm against a spring of a predetermined force rating, diverting exhaust gases away from the turbine.
BLOW OFF VALVES
On engines with throttles, such as gasoline engines, a sudden closing of the throttle plate with the turbine spinning at high speed causes a rapid reduction in airflow beyond the surge line of the compressor. A blow-off valve is used to prevent this.
MULTI-CHARGING
Twincharging started to appear in commercial automotive use during the 1980s, with Volkswagen being a major adopter of the technology. In its most common configuration, a supercharger would feed directly into a larger turbocharger.
TWIN-SCROLL TURBOCHARGER
Twin-scroll turbochargers have two exhaust gas inlets that feed two gas nozzles. One directs exhaust gases to the outer edge of the turbine blades, helping the turbocharger to spin faster, reducing lag, while the other directs gases to the inner surfaces of the turbine blades, improving the response of the turbocharger during higher flow conditions.
VARIABLE GEOMETRY
Variable-geometry turbochargers are another example of turbocharger development. They generally work by allowing the effective aspect ratio of the turbocharger’s turbine to be altered as conditions change.
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All Comments (21)
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Check out this related video on how oxygen sensors work - https://youtu.be/KIF8P2J1CeE
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The animation of the roots supercharger at 5:25 has the air flowing the wrong way.
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This is the most in-depth explanation of forced induction I've ever seen.
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25:07 the WRX ejected its foglight cover. That's a +5hp net gain.
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I've been a mechanic for over 12 years so I know most of the information provided in this video, but I enjoy watching videos like these just to broaden my understanding of the automotive world and you never know you might learn something. This is by far the best visual and in depth accurate video (excluding the one part) I've seen made about a subject surrounding automobiles. Fantastic video 👍
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All I've ever known about FI was contained in this presentation, combined with twice as much stuff I didn't know ALONG with the history... I wish I could like this twice
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yeah as others have also said the blower is turning the wrong way, the air goes around the outside
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I enjoy these videos because: A) No distracting music, B) Pure facts and figures, C) No flowery "chic" terms or phrasing, D) Interesting subject matter that is relevant to modern life. Thank you for keeping it "simple"...so to speak.
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0:15 wtf??? What the hell is she doing, how is someone able to spill that much gas??
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Srsly dude. Kudos to you. This is some HIGH QUALITY content.
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The pumped airflow is the Opposite way in the animation of the rootsblowerpump. The lobes move the air on their outsides up, not down between them as drawn
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I love the longer format and the amount of detail you went into. You make great videos, keep it up!
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Hey @New Mind. I know you might not see this but if you do, thank you for the hard work you do with these videos. I am currently getting ready to go to University for Mechanical engineering and your videos gave me even more confirmation that I am making the right decision. You are an inspiration and you should keep up the hard work!!!
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Problem solved: The animation crisis portion was filmed on a mirror.
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What a wonderful presentation and information- since the beginning of your channel I knew you’re a car guy , now I’m sure 👍🏼 keep em coming
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The animation at 5:10 is wrong, the rotors spin backwards compared too the airflow
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Even though i already knew this, this was still super interesting and so well explained! Best explaination of forced induction i have ever seen
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This is impeccably well researched and brilliantly articulated.
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The illustrations show the air taking the wrong path through the rotors. It actually goes around the outside and the meshing rotors seal the air down. There is no room for displacement between the rotos it therefore has to use the volume of the shape of the mating parts. Great video. Thank you.
