Mech_Engineer said:
If you propose to use compressed air for a power source, you need to carry it on-board. Otherwise you'll need to carry your required energy to compress the gas on-board in some other form, like gasoline.
This isn't sounding good. You're saying you use the kinetic energy from the blades to drive a compressor that pumps air to spin the blades, so at most all this thing could do is spin the blades for a little bit until they run out of kinetic energy (you're neglecting external air drag on the blades also, probably one of the largest factors on a helicopter rotor).
With 5 horsepower of input, that will be your maximum output as well. The point of a helicopter's engine is to put out enough power to create a downward flow of air that in turn creates a thrust in the opposite direction. Moving all of that air takes a lot of energy, and since your special blades aren't "creating" any energy no matter how complex the rotary vane compressor approach is, they're just spinning around and will completely dependent on additional power input if they need to lift something.
Being "very close to a perpetual motion machine" is probably not a good thing... To answer your question the only fundamental efficiency that all machines must live by is that their efficiency will be less than 100%. For a machine to continue moving indefinitely, it must have a power input that is equal to all losses in the system.
Your problem is that you're thinking of the rotor as the system, where all it needs to do is keep spinning. In fact the rotor is one part of a helicopter as a system, and the rotational kinetic energy stored in the rotor is small compared to the energy required to keep the helicopter aloft for say 5 minutes.
First I think I need to extend an apology, after re-reading my response to you it sounded condescending, and in no way do I feel that.
Now to defend as best I can my thoughts, first air that is compressed in a sealed environment, will return almost all the energy of compression with the exception of friction in both directions, and loss of thermal value through the confining walls. In a conventional system the force of compression is spread over the surface area of say a piston, and any energy returned would be spread over the same area and plane of movement.
In the start of any compression cycle the required energy is low, and as pressure builds the energy demand grows, and in all designs that I'm aware of power is applied very near the main shaft, close to the center of rotation, the least effective place to put torque.
In the design that is being talked about here, the initial energy input will cause movement in both directions, and as air pressure, and kinetic energy increase, a throttle of some design will start bleeding air at the point of maximum torque application... (An example that comes to mind is something I'm sure almost everyone has done, Washing a tire that is free to spin, the tire turns quite fast if water is directed on the outer diameter, but putting pressure at the hub near the bearings will produce very little turning, if any).
As this is pretty much a flow through design, good insulation in the right places will prevent most thermal loss.
Thrust produced by the turning of the rotors, should be around 90%+ of the power absorbed from the tip jet discharge. As stated in the past post, air temperature at the intake, and temperature of discharge, will give the sum of energy conversion within the system.
Would this not be a little along the same lines as a heat pump, that gathers much more BTU value than is required by the driving power unit, that moves the gas through the cycle.
A COP in mechanical form?
The rotors and compressor halves, do make the system, along with a few control features.
Consider an electric motor that is set in a bearing mount that will allow both, armature, and housing to turn, each unit is attached to a proper propeller (1 tractor, and 1 pusher) and the leads supplied a voltage(two contact rings on the housing), each part will rotate in opposite directions, and at a speed equal to the division of the sum of both props. If one prop has a different thrust than the other one, speed will divide accordingly and the prop with less thrust will run faster.
Air has energy based on it's temperature, and if BTUs are liberated through the compression and expansion cycle, how are those BTUs any different than those liberated through combustion of fossil fuel??
I think Rudolph Clausius made comment about the exactness of "work into heat, and heat into work"
So many thoughts, I'm about to go brain dead.:shy:
Ron
