karoliina.t.salminen
Well-Known Member
I was watching a video about some EADS concept jet where the jet engines were replaced with electric ducted fans. And actually several such ducted fans instead of like two. And I was also looking some unducted fan information at the same time. And what we know is:
- it is beneficial to move a large amount of air a little compared to moving a small amount very fast, so low disc loading is good
- propeller size is limited by physical dimensions of the aircraft typically, e.g. ground clearance considerations
- what if we have one gasoline engine in a hybrid configuration where the gasoline engine turns generator and there are several electric motors turning props which have pitch speed at very high speed, in other words, they produce not so good thrust at low speed, however, because the penalty of adding more of them is smaller with electric technology, what if we had many props that have too high pitch speed and they would together have enough thrust for takeoff and at the same time the optimum cruise speed would be fairly high as the pitch speed of the prop would not be a limiting factor and no complicated mechanics would be needed (for adjusting prop pitch).
So this is the idea that I got today:
- very low disc loading by using multiple props to divide the load to large air mass
- high pitch speed (for high speed cruise)
- and one (or two if redundancy is desired) gasoline engine turning the generator, i.e. motorcycle or car engine. Motorcycle engine would be more ideal because the continuous high rpm (~e.g. 8000 rpm cruise) will allow using smaller and lighter weight generator as the generator can suffice with higher KV.
- it is beneficial to move a large amount of air a little compared to moving a small amount very fast, so low disc loading is good
- propeller size is limited by physical dimensions of the aircraft typically, e.g. ground clearance considerations
- what if we have one gasoline engine in a hybrid configuration where the gasoline engine turns generator and there are several electric motors turning props which have pitch speed at very high speed, in other words, they produce not so good thrust at low speed, however, because the penalty of adding more of them is smaller with electric technology, what if we had many props that have too high pitch speed and they would together have enough thrust for takeoff and at the same time the optimum cruise speed would be fairly high as the pitch speed of the prop would not be a limiting factor and no complicated mechanics would be needed (for adjusting prop pitch).
So this is the idea that I got today:
- very low disc loading by using multiple props to divide the load to large air mass
- high pitch speed (for high speed cruise)
- and one (or two if redundancy is desired) gasoline engine turning the generator, i.e. motorcycle or car engine. Motorcycle engine would be more ideal because the continuous high rpm (~e.g. 8000 rpm cruise) will allow using smaller and lighter weight generator as the generator can suffice with higher KV.