StefanLazic

1) I was not planning of making one 2) I did not know about the german prototype before starting this thread

The germans built a functional one in 1943

I just found out that the germans built a counter-rotating turbofan engine in 1943... the Daimler-Benz DB 007. With the inside shaft rotating at 12k rpm, and the drum which was also holding the bypass fan blades rotating at 6k rpm. Interesting thing to note is that some of the bypass air was used to cool the turbine, and that counter-rotation was achieved with a gearbox.

I think that the germans made hundreds of prototypes before making a successful jet engine. I have to risk about 1 year of savings to build a prototype that may or may not work... I guess that I'd have to build at least 10 prototypes before having a viable commercial engine, thus I believe that a jet engine is out of my reach. And unfortunately in switzerland it's impossible to get financial help to build a prototype of an invention (from the govt). Maybe I should try a kickstarter.com project...

Unfortunately I'm just an automation engineer and I don't have any contacts within aerospace companies, which don't exist where I live (well except RUAG, but I don't like them as they think that I'm too stupid to work for them; I can't even imagine what kind of arrogant geniuses they have in there, minimum 130 IQ each employee, all with 100 years of experience and aged under 30, and willing to work free overtime). I'm a swiss citizen and there are no jet engine manufacturers in switzerland. Unfortunately I work full time and I don't have much free time to do R&D or to build a jet engine.

So does anyone have any contact information?

I think it depends on how hilly your terrain is. If there are many ups and downs, then renegerative braking would make A LOT of sense. But if your terrain is mostly flat, I believe that the added weight, complexity and cost will far outweigh any gains. Bikes do not have much kinetic energy due to their low speed. So there is almost nothing to be gained by converting the kinetic energy to chemical energy (battery) during braking. But there would be A LOT to gain in a hilly terrain as the potential energy will be significant. Here is a comparison: Kinetic energy in a 80 kg bike+rider travelling at 10 m/s: 80 kg * (10 m/s)2 / 2 = 4000 J Potential energy for a height of 100m of a 80 kg bike+rider: 80 kg * 100 m * 9.81 m/s2 = 78480 J You would get 20 times more energy from a 100m drop in height than a 10 m/s difference in velocity. At lower velocities the difference is even more significant. At 5 m/s you have about 1000 J of kinetic energy. Imagine accelerating from a stop to 5 m/s and then stopping immediately. You'd have to do that 78 times to equal the work needed to gain 100m of height (or 328 feet). Calculate how much acceleration and deceleration you do in a day, and to what speed. Then calculate the kinetic energy loss from braking. Then check how hilly your terrain is and calculate the potential energy loss. Then check out how much energy is stored in a battery. Then decide if it's best to carry a second battery or add regenerative braking.

By having one row of variable guide vanes at the inlet of the compressor and by bleeding the air from the compressor after the clockwise or counter-clockwise rows, depending on need. You can use bleed air to extract power from the compressor and use it elsewhere. Like turbine cooling and air conditioning in the aircraft.

What matters is that the blades encounter the air at the right angle of attack. The flow doesn't need to be axially straight for that.

Are you trying to get the maximum force on a conrod, or the average force on a conrod? If it's the average, just divide the torque of the engine by the number of cylinders and then divide again by the radius of the crankshaft. If it's the maximum... I think the easiest is to find the maximum pressure inside the cylinder, then divide by the area of the piston top to get the force. EDIT: I'm assuming that you are talking about internal combustion engines.

The mass of air is very small. The gyroscopic effects are negligible. As for gyroscopic effects due to the rotation of the engine components, they will be smaller in a counter-rotating design. What determines the direction of the airflow is not only rotational speed, but airfoil profile and angle of attack. You are assuming that the profile and angle of attack will be the same for each stage, which doesn't need to be the case. So the two shafts do not need to spin at the same speed for the flow to go straight on average. In a counter-rotating design you could have each stage rotating at a slower speed than a traditional setup while still delivering the same performance, thus optimizing the rotational speed for the slow-turning fan.

Lets say that I build two prototypes (one with a traditional design and one with a counter-rotating design) and find that the counter-rotating design is better, what then? Where do I publish the results? Care to give some contacts? Otherwise I just spent a lot of money for nothing.

Building a prototype is expensive. Maybe I should start a crowdfunding campaign

One rotating row and one stator row forms a stage. A traditional design with 10 stages would need 20 rows (10 rotating, 10 stationary). A counter-rotating design with 10 stages would need just 10 rows (no stationary blades). That's a 50% reduction. Check out wikipedia for a better understand on how axial compressors work: https://en.wikipedia.org/wiki/Axial_compressor

They have counter rotating spools, but one spool turns one compressor and the other spool turns another separate compressor. It's explained on wikipedia: https://en.wikipedia.org/wiki/Rolls-Royce_Pegasus#Design My idea is to take the two separate compressors and join them together in a single unit, in order to eliminate the stator blades and reduce the amount of parts, weight and size of the engine. I did some CFD simulations using CFX on the counter-rotating compressor and it looks like the counter-rotating stator-less compressor performs just as well as one with stators. Unfortunately I have only 16 GB of RAM and I could not use fine meshes nor many compression stages, so I can't tell for sure.