Air Check Valve: Preventing Air Pressure Backup in Lift Fans

[Piper84]

would an air check valve help lift by preventing air presure backup through the lift fan?

 

[Nidum]

What do you think ? Try doing a sketch of the air flow system in a simple hovercraft .

 

[Piper84]

It may not require as much hp if a ck valve is used our a large poppit type valve?

 

[Baluncore]

would an air check valve help lift by preventing air presure backup through the lift fan?

The lift fan is a compressor that generates a downward flow and so should have no back flow. I would expect a continuous smooth flow of air would be necessary to maintain the continuous flow that is lost from below the skirt. Any stop-start flow condition would stall and greatly disrupt the flow through the compressor, it would lead to a total loss of compressor efficiency.

A one way valve would need to stay open. It would reduce the flow by the restriction or by the return spring pressure. It appears that, not only is a non-return valve not needed but it would increase the weight and reduce the flow, both of which would increase fuel usage.

 

[Piper84]

Thank you for the info. Should have realized that the whole craft is like a ck valve holding air presure in and released at a controlled rate by the skert. Trying to think of ways to use less hp. Closer tolerance in fan and ducting may help.

 

[CWatters]

Closer tolerance in fan and ducting may help.

It's losses between skirt and ground that matter most. If you could reduce that to zero you would only have to pump up the skirt once.

 

[Piper84]

Any one think of using an outrunner motor? Thay are light wt. and the one I'm looking at can put out 25 hp but requires 150 to 200 amps at 70 v max ECS control mod. This may be a good lift/thrust motor. Would need an onboard generator for power. I have used micro wave transformers rewound as a step down transformer For other projects may try it for this application. Any input?

 

[anorlunda]

Any one think of using an outrunner motor? Thay are light wt. and the one I'm looking at can put out 25 hp but requires 150 to 200 amps at 70 v max ECS control mod. This may be a good lift/thrust motor. Would need an onboard generator for power. I have used micro wave transformers rewound as a step down transformer For other projects may try it for this application. Any input?

Did I miss it; how much weight are you trying to lift?

As @CWatters said, the key parameter is the skirt-to-ground losses. Without that estimate, you can't estimate the size of anything else.

 

[Piper84]

Total wt. of craft with two people will be around 600 lbs using a 12 x 5 ft. Deck

 

[Baluncore]

This may be a good lift/thrust motor. Would need an onboard generator for power. I have used micro wave transformers rewound as a step down transformer For other projects may try it for this application. Any input?

Any electrical lift system should avoid transformers and low frequency power. It needs to use aircraft technology = 400Hz three phase alternators and switching power controls. Why have an internal combustion engine plus an alternator and a motor when the ICE could do the job without the added mass and inefficiency of the electrical components?

As a hovercraft increases in size the skirt length rises in proportion to the diameter while the area rises as to the square of the diameter. Load capacity rises with area. PV panels become a better investment as size increases.

Since power requirements are continuous it would seem that a high bypass gas turbine engine would be a good lift solution as it could operate at an optimum setting. For smaller craft, a tuned two stroke diesel might also be considered in that application. Batteries are still heavy so there seems little advantage in electric motors for lift air compressor, unless the craft is fitted with efficient solar panels. Unlike some high altitude UAV aircraft, hovercraft do not always operate in clear sunlight, there are shadows.

 

[CWatters]

+1

I don't see any advantage of using an internal combustion engine to power a generator that powers an electric motor. Just use the internal combustion engine to drive the lift fan direct.