Spindash64
Airman
- 82
- Oct 21, 2021
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The top speed of something driven by a propeller is around 528mph. This is a limitation of propellers, not engines. I am curious about ducted fans.WWII era engines needed to run very large safety margins by today's standards, since fuel can never be perfectly mixed, and it's entirely possible for a lean spot to ignite prematurely, even if the average is slightly rich
Helicopter turbine engines deliver huge power from a small and light unit.I'm aware of the limitation of propellers. But that alone wouldn't explain why helicopters use Turbine engines
It's not really important either way, though, because I'm not asking about aircraft performance, just engine performance
The top speed of something driven by a propeller is around 528mph. This is a limitation of propellers, not engines. I am curious about ducted fans.
Ten to fifteen years after a war without turbojets and turboprops, fighter aircraft and bombers are pushing that envelope. I think the most interesting thing about all this is defensive armament. Lacking massive speed advantages, fighter aircraft close slowly on the bombers from the rear, giving tail gunners lots of time to sight up on them.
The 575 mph for the Tu-95 partly due to the turbine engines' exhaust thrust.
A lot of that can be answered looking at the commercial aircraft market and prevalence of 500-2000hp turbo props. Granted the turbo props took over before the more modern/sophisticated reciprocating engines showed up. Trying to start up a "new" reciprocating engine using 1990s or newer technology vs existing small turbines would be difficult.the comparative costs and difficulties of the maintenance, parts, and supporting services/units needed for modern turbine engines vs a modern high power piston to say for sure,
Yes. The Pratt & Whitney turboshaft that Lotus used in their Lotus 56 1968-71 Formula One/Indy car was rated in a rebuild life in hundreds, if not thousands, of hours. The contemporary Ford DFV ICE was rated in single hours.The other thing to take into account is the engine life.
tank engines are not rated at thousands of hours. Most turbine engines are and modern turbines are modular. You can replace one section of the engine and not replace/overhaul the whole thing. Now tank turbines need better filters (or at least larger) because they need more air.
In the 1960s and 70s turbines on AG aircraft were being rated in the 3-5,000hr area, They may have cost more than 450-600hp radial but they lasted several times longer so the cost averaged out.
Manufacturing has gotten better but aircraft engines were sort of like mass produced race car engines. And that is what you need in for a modern piston aircraft engine.
A higher standard of manufacture and/or inspection.
But then the eventual top developments of the Merlin were twice the power and the comparably sized Roll Royce Crecy tests pointed to eventually getting twice that again. Not to mention we can look to more power recovery from thermal excess and electronic engine management in addition. From 27 litres it is not unreasonable to think of having 6,000bhp to hand by now. As to what one might do with it is another matter. The Rolls Royce Crecy and Napier Nomad are, perhaps, the best OTL pointers (in different directions) to what might have been.My 2009 Honda Fit has a 1.5l engine that puts out 117HP at 6600rpm. This works out to a BMEP of 1100N/m^2. A Rolls Royce Merlin II has 27l displacement. It put out 1030HP at 3000rpm for a BMEP of 1140N/m^2. Compared to WWII engines, my Honda pollutes less, and I hope it is more efficient. 150 octane gas is no longer available.
There are absolute physical limits to what you can do with a piston engine turning a propeller.
Don't forget variable valve timing!But then the eventual top developments of the Merlin were twice the power and the comparably sized Roll Royce Crecy tests pointed to eventually getting twice that again. Not to mention we can look to more power recovery from thermal excess and electronic engine management in addition. From 27 litres it is not unreasonable to think of having 6,000bhp to hand by now. As to what one might do with it is another matter. The Rolls Royce Crecy and Napier Nomad are, perhaps, the best OTL pointers (in different directions) to what might have been.