Roots And Centrifugal Supercharging; Together?

Discussion in 'Technical' started by 84FordMan, Dec 12, 2004.

  1. A thought has struck and stuck in my sleep depraved mind, would there be any benefit over just a roots blower or centrifugal supercharger alone in the setup below:

    - Vortech V1 T-trim spun by the belt, discharge tube goes to an intercooler, tube from intercooler feeds to a throttle body bolted onto the back of an Eaton M112 roots blower.
  2. your trying to compress compressed air. you may experience higher PSI but you can accomplish the same by using a different blower.

    the only thing that it may do is help lower end torque because the roots is better for that and the centrifugel will bring the high numbers. although i dont know for sure, but i have seen some twin turbo and roots blown engines before and in that case the turbo would act like the centrifugal blower. but i dont know what kind of gains they experienced, it may have just been for the "wow" factor when he popps the hood.
  3. Go for a single screw compressor instead, it combines the advantages of positive displacement compressors with the efficiency of the centrifugal compressor.
  4. Or you could use a Lysholm blower, which is the best of both worlds.
  5. Note that the Lysholm screw is a compressor, not a blower like the roots. The difference being that the lysholm has internal compression.
  6. Right. But it's still positive displacement.
  7. what is positive displacement?
  8. I don't know, but it has to do with tourqe.

    EDIT: Boost level increases in direct proportion to engine speed with positive-displacement designs, but with centrifugal superchargers (both belt and turbine operated) boost increases proportional to the square of the engine speed. Or something.
  9. #9 Sled Driver, Dec 16, 2004
    Last edited by a moderator: Apr 25, 2016
  10. so positive displacement is when air cannot move backwards in a supercharging configuration?
  11. Fück if I know.
  12. A positive displacement compressor works by using a "displacement", the piston engine is basicly a positive displacement compressor, it fills its "displacement" with the gas which are going to be compressed, then it compresses it. With a screw or a piston engine the air is compressed inside the compressor while the roots basicly "blows" air (hence the name blower) at a rate greater than the its being consumed by the engine or equipent that is feed by the roots blower.

    The centrifugal compressor is instead a dynamic compressor, it has an open flow, it doesn't use a "displacement".

    This doesn't mean that the boost is going to be constant with a positive displacement compressor as its volumetric efficiency isn't constant. Leaks are greater at lower speeds, this also affects the flow.
  13. ah.. i see.. thanks for the schooling, johan.. would you say a centrifuge SC is the most effective form of SCing? im inclined to think so, but what specifically can be the advantage of positive displacement and why is its form of compression better then "dynamic compression" provided by a centrifugal SC? or are they just different? im also inclined to think a centrifugal SC is better cause a intercooler can be mounted.
  14. Roots blowers can also utilize intercoolers sandwiched between the blower and the manifold.
  15. Hmm, I know of turbocharger/twin screw supercharger setups, mainly on diesels though. However for a combined supercharger system, it will end up drawing the same power to turn two chargers as it would to turn one larger one
  16. I have a little bit different question: Is it possible/feasable to put a non-intercooled SC in front of a large turbo and if so, what would be the ideal SC for it? Or would it be a better idea to just twin turbo?
  17. I once read that some company was building a centrifugal Supercharger/turbocharger....Gas blown and pully driven.
  18. The lysholm screw is probably one of the best compressors one can use for supercharging, they have high adiabatic efficiencies and they are of positive displacement type with together with small leaks and a good volumetric efficiency gives a quite constant boost.
    Centrifugal kompressors also have a high adiabatic efficiency but their boost increase with engine speed. With limitations in economy I would expect that the compressors found in superchargers aren't of the same class as turbochargers where a lot of money can be spent on developement.

    All compressors can be cooled with and intercooler, with the exception of where the fuel is injected before the compressor (the fuel would then condensate in the interccoler). An intercooler is in general recommended for all applications.

    Mechanically driven compressors have been used together with turbochargers, the turbocharger then feeds the compressor. When the turbochargers delivers boost the compressor is basicly bypassed with a valve. This setup makes it possible to combine the low speed torque with the high speed torque of the turbocharger.
  19. #19 84FordMan, Dec 17, 2004
    Last edited by a moderator: Apr 25, 2016
  20. #20 2998ccCSL, Dec 17, 2004
    Last edited by a moderator: Apr 25, 2016
  21. #21 Sled Driver, Dec 17, 2004
    Last edited by a moderator: Apr 25, 2016

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