Greetings,
Say you have two identical engines turning identical props. I'm assuming the most efficient option is to have them separated by enough distance to prevent interaction between the props. I'm further assuming that having them completely overlapping in a coaxial arrangement would reduce efficiency the most, and that counter-rotating would be better than having both rotating the same direction. Anything in between like 50% overlapping would be less of a reduction in efficiency than fully overlapping. First question, are these assumptions typically correct for low speed (under 80 mph) aircraft?
The next question is much harder I imagine. Are there any general estimates of efficiency loss? For example, if we consider completely separated props to be 100%, what would be the efficiency of fully overlapping coaxial prop, or partially overlapping props. I know there are going to be a million variables, and "it depends on" caveats, but I'm just looking for the roughest of guestimates. I also expect it will increase noise and vibration.
Thanks,
Rusty (I hate winter)
Say you have two identical engines turning identical props. I'm assuming the most efficient option is to have them separated by enough distance to prevent interaction between the props. I'm further assuming that having them completely overlapping in a coaxial arrangement would reduce efficiency the most, and that counter-rotating would be better than having both rotating the same direction. Anything in between like 50% overlapping would be less of a reduction in efficiency than fully overlapping. First question, are these assumptions typically correct for low speed (under 80 mph) aircraft?
The next question is much harder I imagine. Are there any general estimates of efficiency loss? For example, if we consider completely separated props to be 100%, what would be the efficiency of fully overlapping coaxial prop, or partially overlapping props. I know there are going to be a million variables, and "it depends on" caveats, but I'm just looking for the roughest of guestimates. I also expect it will increase noise and vibration.
Thanks,
Rusty (I hate winter)
