Ducting pressure air from front to rear?

[Tesla]

Something I've been thinking about,
Just stumbled across this, patented aparantly.
Interview With Inventor and Patent Holder of the Air Channeler System For Trucks

Any comments??

Is it another "Smoke & Mirrors" trick, or could it work?

[drmiller100]

I have given a LOT of thought about this lately.

I don't think it is a simple solution.

The high pressure at the front of the car doesn't really cost energy in the long run. What costs energy is the turbulence or size of the rear of the car.

So, the channel has to be BIG to be effective. and if the channel can be big, why not just make the frontal area smaller?

I think there are easier, simpler benefits with just rearrange the tail - make it taper. You get most of the benefits with almost none of the hassle.

However, I really invite discussion - I think this is MOST of the mileage gains to be found.

[jime57]

I think that there might be some marginal gain on truck/trailers if a large amount of air were allowed to enter the front of the trailer and flow through the internal trailer load and be blead into the rear dead air area. But as Hucho pointed out, it isn't simple. The internal resistance of the trailer now comes into consideration, and they are usually very full and well blocked.

Of course, this would only work with covered trailers, and then only when the weather was dry.

As others have said, there are probably more productive tractor/trailer approaches which have greater gain. Full skirting around all the wheels, well radiused corners, and boattails come to mind.

[Frank Lee]

There are several threads about this on EM.

[Sven7]

As I'm told, one of the points of a boat tail is to allow the pressure built up with the front of the car to come back together and "squeeze" it forward as it moves aft. Kind of like when you take a bite out of a sandwich and all the mayo squirts out the other side. Your teeth are the airflow on the rear of the car and the mayo is your car being gently pushed forward.

Ducting air through the middle would do nothing but waste interior space, as drmiller has mentioned. It would be more effective to introduce rear end taper and reduce frontal area.

[shovel]

I've worked most of my adult life in industries which put me in direct contact with freight trailers, I have a class A license & drive (commercially) about 20,000 miles per year in a medium duty truck/trailer (48ft trailer/ >24001lb GCW) - not a full 18 wheeler, but close enough to not be entirely naive to the industry.

To me it seems more than plausible to make a standard box trailer whose rear doors are slightly offset, and whose sides are hinged mid-way, to allow the box itself to be narrowed to one door wide at the rear when the box is partially laden or empty. I think this could be done without dramatically adding to the dry weight of the trailer, and without having a significant negative effect on the security of the load or on the driver's docking practices. Visibility (when in aero mode) would be somewhat improved too, which isn't a bad thing.

Would it cost more up front? You betcha. Probably $10k more per trailer and yes, it's one more thing to "go wrong". My guess is it could be done well enough, reliably enough, and repeatably enough to pay for itself in fuel well inside the lifetime of the equipment.

[aerohead]

We struggle as it is to manage attached flow for vehicles with ALL the air flowing over the body.
If we begin to rob this flow,shunting it internally,we further compromise the 'outer' flow.
If you had time,calculate the volume of air you would wish to move through the duct at a given velocity.Then sit down with an HVAC contractor and have him calculate the horsepower necessary to move that volume,and static pressure,though the smoothest duct-work he could fabricate for the given duct size and length.
This HP requirement would give us something to think about.

[Tesla]

I get a lot of ideas, most don't work, but the ones that do a real pearls.
Just been investigating if anyone had done anything like that, he apparantly just used PVC pipes, but had no takers in the trucking industry, maybe because it didn't really work that well.
I was also reading on some truck studies using slow flow between cabin and trailer, positive results in testing, but no real world test results.
My initial thoughts were if you could introduce some venting into the centre of the rear to disrupt or shift the vortex cycling and maybe help decrease drag, just investigating ideas.

[aerohead]

Originally Posted by Tesla

I get a lot of ideas, most don't work, but the ones that do a real pearls.
Just been investigating if anyone had done anything like that, he apparantly just used PVC pipes, but had no takers in the trucking industry, maybe because it didn't really work that well.
I was also reading on some truck studies using slow flow between cabin and trailer, positive results in testing, but no real world test results.
My initial thoughts were if you could introduce some venting into the centre of the rear to disrupt or shift the vortex cycling and maybe help decrease drag, just investigating ideas.

See if you can scrape up an article on Ferrarri's 599XX racer.
They have 2-12VDC fans in the trunk which suck air from the diffuser area and blow it out where the tail lights would ordinarily be,at speeds up to around 150 mph.
They claim that if they pulse the discharge that they can intermittently detach the wake.They make no claims about its effect on speed or extended range on the track.
It's interesting reading.
It has been known for a 100-years that blown or suction slots near the rear separation point can lower drag remarkably.Georgia Tech is currently chasing this rabbit.
Historically,the energy to run the pump exceeds the energy saved,for a net loss.
Japan builds a 4-engined,jet turbo-prop STOL aircraft with suctioned wings and it has fabulous low speed flight characteristics.The downside is that the wings require a 5th jet turbine just to power the suction.Ouch!!!!!

[Tesla]

One of the ideas I was considering is just opening a rear vent, as part of the internal venting, dual benefit, may help pull air through vehicle better for ventilation, hence minimise fan use and also put air into the rear vortex and reduce it's size & volatility.
Even though it is only a small amount of air, I imagine it's effect would also follow the cubed equations for velocity & force, hence a small amount of air may have a measurable effect.
Agreed, once you start using power to create the aero effects, benefits can be marginal or negative, so my thoughts are mainly to look at passive ways of moving air from high pressure zones to low pressure zones.
Will try and locate the article you mentioned.