The Naked Scientists

The Naked Scientists Forum

Author Topic: Turbo Chargers  (Read 1452 times)

Offline bcou

  • First timers
  • *
  • Posts: 3
    • View Profile
Turbo Chargers
« on: 21/02/2014 16:16:48 »
does turbo chargers use air from the exhaust ? If yes , it should lack oxygen for combustion as it has gone through already one combustion cycle before it reaches the turbo charger  ?


 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Re: Turbo Chargers
« Reply #1 on: 21/02/2014 20:03:13 »
The turbo charger has a fan in the exhaust stream that is connected to another fan in clean air, so that the clean air is pumped into the engine under pressure. 

The air intake and exhaust are kept separate, and thus no oxygen depletion.

By the ideal gas law, compressing air increases the temperature.  An intercooler decreases the temperature, and by the ideal gas law again further increases the density of the intake air.
 

Offline bcou

  • First timers
  • *
  • Posts: 3
    • View Profile
Re: Turbo Chargers
« Reply #2 on: 23/02/2014 13:47:20 »
Does the compressor store the pressurized air to be feed into the engine later when the turbo charger is used ?
 
 

Online Ethos_

  • Neilep Level Member
  • ******
  • Posts: 1277
  • Thanked: 14 times
    • View Profile
Re: Turbo Chargers
« Reply #3 on: 23/02/2014 15:43:19 »
Does the compressor store the pressurized air to be feed into the engine later when the turbo charger is used ?
Not really. The only time air is being compressed is when the turbo is active. As Clifford has pointed out, the exhaust side of the turbo uses exhaust pressure to drive the compressor side to compress fresh air for use in the engine. While running, the engine might be said to store this compressed air in the intake plenum for immediate use in the engine. But the storage of this compressed air is only available while the turbo is running and while exhaust gases are available to initiate turbo spooling up. Turbo lag is a term designed to explain the short duration that is needed for the exhaust gas energy to achieve the desired compression of clean fresh air to the engine. This results in a very short hesitation in response time after pushing the accelerator down. New technology has virtually illuminated turbo lag in newer automobiles.
 

Offline CliffordK

  • Neilep Level Member
  • ******
  • Posts: 6321
  • Thanked: 3 times
  • Site Moderator
    • View Profile
Re: Turbo Chargers
« Reply #4 on: 23/02/2014 21:57:37 »
The amount of air that an engine sucks through it is pretty extraordinary. 

Say you have a 4L engine running at 3000 RPM (50 RPS).

For a 4-stroke engine, 2 revolutions of the crank for each intake cycle.  And your engine pulls in somewhere around 25x4 = 100 liters of air every second, or about 6,000 liters a minute.

Obviously one could store a bit of air if one compressed it to a few thousand PSI in an oxygen cylinder.

However, the Turbos are designed to pump high volumes at low pressures.  1ATM = 14.7 PSI, so if the turbo is running at about 14 PSI, it is running at about 2x compression, so one would need about a 100L tank to store a second's worth of air intake. 

 

The Naked Scientists Forum

Re: Turbo Chargers
« Reply #4 on: 23/02/2014 21:57:37 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums