SINCE the operation of the positive-displacement supercharger is characterized by a fixed displacement of air per revolution and delivery is affected only to a small amount by pressure variations, the supercharger continues to deliver extra air to the engine at the lower speeds. For applications requiring a high torque at the lower speeds, this characteristic is advantageous; it imparts the desired “lugging” ability to the engine in contrast to centrifugal units where the pressure, being proportional to the square of the rpm, falls off rapidly as the speed is reduced.In spite of the fact that the theoretical efficiency of the Roots type of positive-displacement supercharger is not as high as that of the type which compresses the air within the blower before delivery, the Roots type has the simplest design, having but two moving parts; requires no lubrication in the blower air chambers, the only points of friction being the bearings, seals, and gears.This paper presents a preliminary means of estimating the performance of a positive-displacement supercharged engine and offers a yardstick of the practical limitations for the performance of the units with present-day equipment. It is shown in a discussion of valve overlap, intercooling, and scavenging that the combined effect of the inter cooler and the use of scavenging permits the highest increase in output of any supercharging arrangement discussed - reaching a value of 166% at 10 psi. Intercoolers are much better adapted for use in marine engines where cool sea water is available to absorb the heat than for automotive engine use.


    Access

    Check access

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    THE POSITIVE-DISPLACEMENT SUPERCHARGER


    Additional title:

    Sae Technical Papers


    Contributors:

    Conference:

    Pre-1964 SAE Technical Papers ; 1906



    Publication date :

    1942-01-01




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




    Simulation of a Positive Displacement Supercharger

    Sorenson,S.C. / Univ.of Illinois,US | Automotive engineering | 1984


    Simulation of a Positive Displacement Supercharger

    Sorenson, S. C. | SAE Technical Papers | 1984



    Introducing a High Efficiency Variable Positive Displacement Automotive Supercharger

    Milburn, S. M. / SAE | British Library Conference Proceedings | 1994


    Introducing a high efficient variable positive displacement automotive supercharger

    Milburn,S.M. / VAIREX,US | Automotive engineering | 1994