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Turbocharged Engine exhaust Systems

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Old 4th May 2014, 03:24
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The turbo needs velocity its not px this is a myth that it require px
Turbo chargers extract energy from the exhaust stream by lowering its pressure as it expands though the turbine. Known as an impulse turbine . This has the undesirable side-effect of increasing the back-pressure in the engine, which decreases scavenging of the exhaust gas from the cylinders and thereby lowers the efficiency of the piston portion.

Design and Function of a Turbocharger - Turbine | BorgWarner Turbo Systems

Turbo compound engines, on the other hand, operate on the "blow down" principle, which extract energy only from the momentum of the rapidly moving exhaust gasses. Although less efficient than the impulse turbine, it has the benefit of not effecting the operation of the piston side of the system, since there is little to no back pressure.

www.dtic.mil/dtic/tr/fulltext/u2/b807167.pdf‎

In summary, the turbocharger is a pressure turbine, a power recovery turbine is a velocity one.
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Old 4th May 2014, 05:37
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Velocity is transformed across the turbine blade as in a wing that produces lift to px. Velocity is increased in the turbo scoll (divergent duct) from the exhaust. Px in the exhaust pipe from valve to the scoll is not relevant as it velocity that is required and not px.


A compound charger is the same transform's across the blade but instead of driving a compressor it drive a shaft onto the crankshaft.

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Old 4th May 2014, 06:14
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Velocity is transformed across the turbine blade as in a wing that produces lift to px. Velocity is increased in the turbo scoll (divergent duct) from the exhaust. Px in the exhaust pipe from valve to the scoll is not relevant as it velocity that is required and not px.
So explain the science behind waste gate operation, does it bleed off velocity or pressure from the system?

This quote from a turbo-charger manufacturer;

The turbocharger turbine, which consists of a turbine wheel and a turbine housing, converts the engine exhaust gas into mechanical energy to drive the compressor. The gas, which is restricted by the turbine's flow cross-sectional area, results in a pressure and temperature drop between the inlet and outlet. This pressure drop is converted by the turbine into kinetic energy to drive the turbine wheel.
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Old 4th May 2014, 06:51
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So what gives you the px differential across a wing ? Speed / velocity. Velocity across the blade. No difference to any gas turbine. Velocity transformed not px. If it was just px there would be no need for a divergent scroll would there.

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Old 4th May 2014, 06:55
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Remember
Velocity increase. Px decreases temp decrease.

Or

Velocity decreases. Px increases temp increases

Gas law for subsonic flow.

Unless they got that wrong as we'll

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Old 4th May 2014, 06:57
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You are confusing a gas turbine engine with a turbocharger they operate on different principles.

The turbine section of a "jet" engine has stators and rotors, the stators expand the air and accelerate it focusing on the rotors. These are aerofoil shaped and act like a wing turning the shaft.

In the basic turbocharger gas pressure builds up against it and the act of the pressure flowing through the unit to the exhaust drives the shaft.
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Old 4th May 2014, 07:19
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It's exactly the same the convergent duct in a turbine to increase velocity is the scroll in a turbo. Turbine wheels on a turbo also have airfoils

That's why you can make a jet engine out of a turbo and why anti lag as in a WRC rally car injected fuel into the turbo to increase velocity of the gas flow.

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Old 5th May 2014, 00:59
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A turbine is a divergent duct, not convergent - otherwise known as a nozzle.

Whether it's axial, radial or mixed flow, the principles are the same - expanding gas through a nozzle allows you to capture some kinetic energy that would otherwise be released as heat.
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Old 5th May 2014, 02:48
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A compound charger is the same transform's across the blade but instead of driving a compressor it drive a shaft onto the crankshaft
I'm afraid you don't understand the basic principles involved. One operates on the basis of Newtons second law of motion, and the other on the basis of Newtons third law. I'll leave you to figure which might be which.
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Old 5th May 2014, 03:49
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So the burner can is divergent is it guess better have a closer look. The 1st wheel is the smallest then wheel size increases proportional up to balance size against force as the energy is released
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Old 5th May 2014, 04:03
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no - burner can is (theoretically) the constant pressure part of the brayton cycle.
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Old 5th May 2014, 06:49
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Bummer can exit is convergent to increase volicity into the I
1st Ngv. From that point onwards it starts to go divergent thought the rest of the engine to get maximum energy recovery. Last point before air enters the bummer can it goes divergent to increase px and slow volicity. Why is this. So you don't blow the flame out
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Old 5th May 2014, 08:51
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Last time I look at a turbo charger ext gas entered the scroll in a convergent duct. Last time I saw a compound disc was approx 8"inches in dia and had on top of it wait for a convergent scroll to once again increase volicity or in your world dose a convergent duct not do that ?
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Old 5th May 2014, 08:56
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And Ngv do several things as the pass the gas flow though the engine. The increase in dia they flow the air onto the next disc at the correct aoa. And they have a convergent duct between the vanes to increase the the volicity of the air passing through the Ngv.

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Old 5th May 2014, 12:44
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Could you please learn to speak english. You posts are completely and totally unintelligible.
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Old 5th May 2014, 23:57
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Nah they fine if you know what your talking about I just showed the apprentice and he could work it out.
Dia diameter
Aoa angle of attract
Convergent large to small
Divergent small to large
Ngv nozzle guild vane

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Old 6th May 2014, 06:51
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Now that last post made me smile!

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Old 6th May 2014, 07:17
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He suffers from a very rare affliction known as ABSuRD: Apparently Selective But Random Dyslexia.
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Old 6th May 2014, 08:05
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He's actually responsible for maintaining aero engines (apparently..), well, those customers who don't have their perfectly maintained burnt valves lying allover the floor that is...
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Old 6th May 2014, 12:11
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He also suffers from delusions of grandeur
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