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Old 07-21-2014, 01:05 PM   #51 (permalink)
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Look at the engineering Dyson put into their fan to keep it quiet. It has Helmholtz Resonators (sounds like something out of Star Trek). The hypothetical aircraft would shriek like a banshee. You may as well put a jet engine in the middle. Presto, you have a modern high-bypass turbojet aircraft engine.

The Dyson fan uses Coanda nozzles. Those can be applied to vehicles. The paper, Advanced Aerodynamic Devices to Improve the Performance, Economics, Handling and Safety of Heavy Vehicles, is currently paywalled but it's quoted here.

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These experimental results show overall aerodynamic drag reductions on the Pneumatic Heavy Vehicle of 50% using only 1 psig blowing pressure in the plenums, and over 80% drag reductions if additional blowing air were available. Additionally, an increase in drag force for braking was confirmed by blowing different slots. Lift coefficient was increased for rolling resistance reduction by blowing only the top slot, while downforce was produced for traction increase by blowing only the bottom. Also, side force and yawing moment were generated on either side of the vehicle, and directional stability was restored by blowing the appropriate side slot. These experimental results and the predicted full-scale payoffs are presented in this paper, as is a discussion of additional applications to conventional commercial autos, buses, motor homes, and Sport Utility Vehicles.
Hi, Sven7.

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Old 07-21-2014, 06:30 PM   #52 (permalink)
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wonder

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I've wondered if such phenom could be used to propel an aircraft.

I also wonder if instead of a hollow ring foil, linear airfoils with air ejection could be used for spoilers and diffusers on the rear of cars, to fill and fair the turbulence behind the car, reducing drag.

Thoughts?
*I think the high-bypass turbofan uses less power (fuel) so they've settled on that for now.
*For cars,I think Georgia Tech is still trying.So far the 'pump' uses more energy than is saved by the blown/suctioned modifications.
The Japanese have a STOL aircraft which uses slot technology.It requires a 5th jet turbine engine to make the wings work.
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Old 07-22-2014, 01:55 AM   #53 (permalink)
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Have you heard anything recently out of Georgia Tech/Englar?

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These experimental results show overall aerodynamic drag reductions on the Pneumatic Heavy Vehicle of 50% using only 1 psig blowing pressure in the plenums, and over 80% drag reductions if additional blowing air were available.
This sounds like the requirement is mild, but it doesn't talk about the volumes involved. I have 1500cfm of hot air available under my back bumper but I don't know at what pressure.
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Old 07-22-2014, 11:00 AM   #54 (permalink)
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Excellent stuff, Phil.

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