Centrifugal SuperchargerThe centrifugal supercharger (fig. 1-33, view A) hasan impeller equipped with curved vanes. As the impelleris driven by the engine, it draws air into its center andthrows it off at its rim. The air then is pushed along theinside of the circular housing. The diameter of thehousing gradually increases to the outlet where the airis pushed out to the engine intake system.Roots SuperchargerThe Roots supercharger (fig. 1-33, view B) is apositive displacement type of supercharger that consistsof two rotors inside a housing. As the rotors are drivenby the engine, air is trapped between them and thehousing. The air is then carried to the outlet where it isdischarged. Because of the extremely narrow clearancebetween the rotors and the housing, this supercharger isvery sensitive to dirt.Vane SuperchargerThe vane supercharger (fig. 1-33, view C) is apositive displacement supercharger that has a rotor thatrevolves in a body, the bore of which is eccentric to therotor. Two sliding vanes are placed 180 degrees apart inslots in the rotor and are pressed against the body boreby springs in the slots. When the shaft is rotated, thevanes pick up air at the inlet port and carry it around thebody to the outlet side where the air is discharged to theintake system of the engine.AIR CLEANERSClean air is essential to the performance and life ofan engine. The air cleaner must remove fine materials,such as sand, dust, or lint, from the air before it entersthe intake system. The air cleaner normally has areservoir large enough to hold material taken out of theair; therefore, operation over a reasonable time ispossible before cleaning and servicing are necessary.NOTE: A buildup of dust and dirt in the air cleanerpassages will eventually choke off the air supply,causing poor combustion.Multiple air cleaners are sometimes used inlocations where engines are operated under extremelydusty air conditions or when two small air cleaners mustbe used in place of a single large cleaner.The most common type of air cleaners are thefollowing: pre-cleaners, dry air cleaners, dry element aircleaners, and oil bath air cleaners.Pre-CleanersPre-cleaners are devices that remove large particlesof dirt or other foreign matter from the air before it entersthe main air cleaner. This relieves most of the load onthe air cleaner. Pre-cleaners are normally installed at theend of an air cleaner inlet pipe that extends upward intothe air (fig. 1-34). This locates them in an area relativelyfree of dust.NOTE: Cleaning out the collector bowl of thepre-cleaner is part of operator’s maintenance and shouldbe performed during both prestart and post-operationmaintenance.Dry Air CleanersDry air cleaners (fig. 1-35) are attached directly tothe intake system and are used on engines in which theFigure 1-34 .—Pre-cleaner.Figure 1-35.—Dry air cleaner.1-25
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