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Often wondered whilst passing jets on the apron, what sort of revs do a common-or-garden jet engine rotate at (take off {max power}, cruising, etc). I understand they don't need servicing until some large interval has passed, so i guess they don't spin that fast?
Might be best in the chat forum...
It varies depending on the age of the design, and different stages turn at different rpms.
Compressor fan a few thousand rpm.
Follow AgentJayZ on You Tube to become a jet engine expert from your armchair. Fascinating stuff from this engine re builder/expert.
It's complicated. Core of the engine is about 3000 - 3500 rpm.
The fan speed is limited by aerodynamics and at high RPM starts to develop shockwaves on the leading edge of the fan blades. On some engines this accounts for the distinctive buzz saw noise at high power settings.
Take off, climb, and cruise rpms are broadly similar, with a heavy aircraft demanding 90-95% of the engine's power to remain at cruise levels.
True fact: model turbine turns at 120k RPM!
According to Rolls Royce the RB211 (use on lots of 747's etc) turns at up to 6000rpm depending on the exact variant.
http://www.rolls-royce.com/energy/energy_products/gas_turbines/rb211/
and the Trent 60 which is one of the latest versions manages 3000-3600 depending on variant
http://www.rolls-royce.com/energy/energy_products/gas_turbines/trent_60/
A related factoid is that the 3.5cc nitro engine in my Losi 8ight revs to just over 30,000rpm.
*surprised*
i knew model sized turbines went at those sort of speeds, and i assumed full size ones were similar.
amazed at how slowly they spin tbh.
Me too. I had kinda assumed that the core of the big ones ran at fairly insane rpms.
On the bigger engines high shaft rpm would mean that the blade tips are going stupidly fast which causes all sorts of problems (as already mentioned). Thats why tiny model ones can go so high.
Rockhopper's link is a little out as that is industrial gas turbines, and the shaft speed quoted is, I think, the shaft speed of the free power turbine which would then drive the pump/generator/propeller shaft.
It is a bit complicated due to all sorts of aerodynamic jiggery-pokery. Rolls-Royce engines are 3 shaft - low, intermediate, and high pressure systems. GE & P&W used 2 shaft.
It's been a few years since I left RR, but from memory the Trent500 at take off would be running the LP system (ie the front fan & LP turbine) around 3000rpm, the IP system around 8000, and the HP system 10,000+.
I'm sure someone a bit closer to the action will be along shortly and correct me if I'm way out!
Rob
the smaller the diameter of the rotor the higher the speed, this is because there are much less limitation on the tip speed due materials of construction. At large diameters the limits on rotational speed are dependent on blade stress that the blade construction will withstand. It is a bit more complicated but putting it simply.
The latest Trent 1000 (Boeing Dreamliner engine) is a 3 shaft engine and take off rpms as follows:
LP (inc fan blades) - 2700rpm
HP core (the workhorse) - 13700rpm
IP - 8200rpm
quite an interesting interactive game on the RR website
http://www.rolls-royce.com/interactive_games/journey03/
IIRC the Allison engines on my steed operate at 40,000 RPM. The prop operates off a 20:1 reduction gearbox.
Phew, memory seems to be holding up ok then!
IIRC the Allison engines on my steed operate at 40,000 RPM. The prop operates off a 20:1 reduction gearbox.
Allison engine? You a multi-millionaire that own's a P-38, P-40 or early model P-51A before they went to merlins?
When I was a youngster I was a huge vintage aircraft nerd.
I was wrong, that data is from a Garrett unit I previously used to use. The Allisons do 14K RPM and the prop 1k RPM.
I test GE aircraft engines, and the fan(low pressure system) dependant on engine variant, is around 3400-3600 at take off power, but around 1200-1400 at flight idle. Core (high pressure) is around 9000-10000 at take off.
That's all based on the CF6 series, which is getting on a bit, but we're starting to test the new GEnX soon, so that'll be a bit different, lots of composites and plastics.
Bwaarp,
I wish!! 8)
Geared turbofans are where it's at.
www.popsci.com/bown/2009/product/pratt-amp-whitney-pure-power-geared-turbofan-engine