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| Turbocharger power input (consumption) |
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| Circlotron:
--- Quote from: joeqsmith on March 25, 2020, 11:04:25 pm ---I try to match this at 1:1. So 30 PSI on the intake, 30 PSI in the exhaust. --- End quote --- I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap. A 1:1 pressure ratio wouldn't work very well for a turbo converted to a jet engine though! Inlet pressure would have to be higher than exhaust for the air + fuel to flow in the right direction. I've heard a single turbo with no air filter on an 855hp V8 on a dynamometer from a distance of about 20 metres. That convinced me that there was plenty of action going on! Living proof of advances in material science. |
| langwadt:
--- Quote from: Circlotron on March 26, 2020, 01:09:20 am --- --- Quote from: joeqsmith on March 25, 2020, 11:04:25 pm ---I try to match this at 1:1. So 30 PSI on the intake, 30 PSI in the exhaust. --- End quote --- I imagine that if intake pressure was much higher than exhaust pressure you would get blow-through during valve overlap. A 1:1 pressure ratio wouldn't work very well for a turbo converted to a jet engine though! Inlet pressure would have to be higher than exhaust for the air + fuel to flow in the right direction. I've heard a single turbo with no air filter on an 855hp V8 on a dynamometer from a distance of about 20 metres. That convinced me that there was plenty of action going on! Living proof of advances in material science. --- End quote --- modern efficient turbofans are more like 40-50:1, a 50 year old turbojet ~12:1 |
| firewalker:
For an EE forum we are doing pretty well! I guess engineering is engineering! :D :D :D Alexander. |
| mzzj:
--- Quote from: Circlotron on March 25, 2020, 10:32:41 pm --- --- Quote from: langwadt on March 25, 2020, 09:38:41 pm ---it is not quite so simple, the turbine is driven by the kinetic energy of the exhaust stream not just pressure --- End quote --- It sure isn't simple! I've often wondered about the effect of having a large plenum right at the inlet to the turbine similar to one commonly used at the compressor outlet where the inlet pipes branch from. That would spread and reduce the amplitude of the kinetic energy of the pulsating waves to more of a smooth flow, similar to the effect of a series choke with rectified DC current flow. The turbo might have to be resized to suit the new circumstances, but I wonder if there would be any benefit. Somewhat similar to a transformer not having to handle the peak currents of a capacitor input filter? Far fetched maybe, but sometimes physics has some interesting parallels. --- End quote --- Bad business, you want to keep the exhaust gas as hot as possible and large plenum would be difficult to insulate. (hot gas is flowing faster and energy is lost when it cools down) If you google "twin scroll turbocharger" it has almost opposite idea, maintain the kinetic energy and pressure spikes from each cylinder as well as possible. |
| firewalker:
With many assumption made. A 2000 cm3 engine at 6000 RPM with a "pump" driving the intake at 0.5 bar (50000 Pa). Every revolution the engine needs 1000 cm3 of air. This means 50000 cm3 or 0.05 m3 every second. The power the fluid takes from the pump is P=0.05*50000 = 2500 Watt. This is without taking in account the vacuum of the engine that the pump should overcome. This means that the pressure differential is in reality 1.5 bar or more for 0.5 pressure. And is just the power of the fluid. Alexander. |
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