Tiger Tim
Well-Known Member
A couple years ago I presented the world-changing steam Diesel engine here and, well, the world didn’t change. I went back to the drawing board and have returned with a power plant that has an absolutely unprecedented ratio of thrust to simplicity, and all at a very light weight. I figure the entire engine, propeller, and fuel control should weigh about the same as an equivalent size conventional three bladed prop. Hear me out.
I’m sure you’ve heard of pulse jet engines and maybe even seen a video or two of them on youtube. They’re dead simple in that they draw in air, mix it with fuel, and burn it sending the resulting gases out the exhaust which draws the next charge of air in. Some have one-way valves so the exhaust doesn’t blow forward, some don’t need valves due to their design. In any case, they couldn’t be much simpler and usually run on a compressed gas for fuel like propane to do away with the need for pumps. Throttle on the youtube ones is just two valves in parallel; one fixed at whatever minimum flow sustains idle and the other is controllable on a bypass for thrust above idle. For aviation safety purposes there should be a master fuel cut-off upstream of both of these valves.
The problem with these jets is that they move a small volume of air at a very high speed, which isn’t particularly efficient at our typical low airplane speeds. A propeller is much more efficient for us as it moves a large volume of air at a slow speed. Luckily even a slow moving airplane has a part that moves incredibly fast: the propeller tips. I don’t think a pulse jet would survive the forces of being mounted out at the tips of a propeller, but does it have to be there? What if only the exhaust was at the tip? By putting the intake at the hub and using hollow blades as the combustion chamber with the exhaust at the tip you can combine the engine and propeller into a single piece! The original model DynaJets were made of two steel stampings edge welded together, no reason a propeller can’t be the same, just different shaped stampings. Here’s a working demonstration model of what I have in mind but it’s range is limited because it uses a cold gas for simplicity:
Last but certainly not least, to further simplify, my idea uses an automatic variable pitch mechanism. Basically it’s just cribbed from the Everel propeller where the blade is on an angled flapping hinge. Load on the prop causes it to track further forward which in turn causes a reduction in pitch. This is a sort-of poor man’s constant speed prop and again does away with a lot of complexity. My BuzzProp would also be a single blade to take advantage of the largest possible swept area as well as minimizing tip losses.
So there you have it: a one blade, one piece, automatically variable pitch propeller and engine unit that would weigh next to nothing and run on cheap, readily available propane.
You just have to get over the noise and what I imagine would be a spectacular light show at night.
I’m sure you’ve heard of pulse jet engines and maybe even seen a video or two of them on youtube. They’re dead simple in that they draw in air, mix it with fuel, and burn it sending the resulting gases out the exhaust which draws the next charge of air in. Some have one-way valves so the exhaust doesn’t blow forward, some don’t need valves due to their design. In any case, they couldn’t be much simpler and usually run on a compressed gas for fuel like propane to do away with the need for pumps. Throttle on the youtube ones is just two valves in parallel; one fixed at whatever minimum flow sustains idle and the other is controllable on a bypass for thrust above idle. For aviation safety purposes there should be a master fuel cut-off upstream of both of these valves.
The problem with these jets is that they move a small volume of air at a very high speed, which isn’t particularly efficient at our typical low airplane speeds. A propeller is much more efficient for us as it moves a large volume of air at a slow speed. Luckily even a slow moving airplane has a part that moves incredibly fast: the propeller tips. I don’t think a pulse jet would survive the forces of being mounted out at the tips of a propeller, but does it have to be there? What if only the exhaust was at the tip? By putting the intake at the hub and using hollow blades as the combustion chamber with the exhaust at the tip you can combine the engine and propeller into a single piece! The original model DynaJets were made of two steel stampings edge welded together, no reason a propeller can’t be the same, just different shaped stampings. Here’s a working demonstration model of what I have in mind but it’s range is limited because it uses a cold gas for simplicity:
Last but certainly not least, to further simplify, my idea uses an automatic variable pitch mechanism. Basically it’s just cribbed from the Everel propeller where the blade is on an angled flapping hinge. Load on the prop causes it to track further forward which in turn causes a reduction in pitch. This is a sort-of poor man’s constant speed prop and again does away with a lot of complexity. My BuzzProp would also be a single blade to take advantage of the largest possible swept area as well as minimizing tip losses.
So there you have it: a one blade, one piece, automatically variable pitch propeller and engine unit that would weigh next to nothing and run on cheap, readily available propane.
You just have to get over the noise and what I imagine would be a spectacular light show at night.
