Duct Duct Go

[kach22i]

The opening sketch is very interesting.

Would it operate at the aero-template profile in cross-section or be better suited to operating in free air and larger than the envelope?

One major concern would be corrosive effects of automobile exhaust on the materials.

With that much mass/surface area I can see this being all titanium although perhaps there are some high temperature plastics that are carbon based that I don't know about.

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The FW-190 video was amazing, even though I only watched the first half before many of the heavy charts came out.

It touched on "ram-air" intake only being effective on automobiles +80mph, first time I've heard that claim.

The air-intake being post fan and internal begs the question of why Porsche didn't do this on the air-cooled 911 models. Seems like an easy way to semi-supercharger/blower one's engine if there is already a powerful fan running.

On the older 911's like my car (1977), it would be pretty easy to cut a hole or slot into the cooling fans fiberglass ducting shroud and close loop it to the CIS airbox located just above it.

[freebeard]

I thought you might like it.

I specified stainless steel and aluminum but I agree the corrosive effects are a problem. I wanted cooling air only with the Coanda boat tail, but then there was that discussion of exhaust driven cooling and I succumbed to peer pressure.

I don't know if the airflow available would support that large a duct. Since the boundary layer makes it half-way down the back window unassisted the final duct might not be much larger that the engine compartment lid. Mimicking the Bird of Prey, it might stretch from out to out on the fenders and be no higher that the beltline.

[Piotrsko]

Sounds to me that the infamous displaced hinge on the engine hood is ideal for the inlet opening.

I have heard that CFM is thought to be 1200 through this fan, but I'm probably wrong.

There are duct sizing calculators for HVAC available online and tables available on ICBO diy house plan sites, although they may not do airspeed.

[freebeard]

I'd heard 1500. IIRC the Porsche fan came with anywhere from 5 to 11 blades.

I'm looking at through the rear fenders at the same hinge line. The whole assembly could reverse-alligator from a new hinge line in the rear apron.

[Piotrsko]

Might be more efficient to reverse cooling flow through the engine than duct it through the wheel wells, say perhaps with an underbody engine scoop. Couple of standard vent boxes joined at the fan inlet, couple of circumference vents on the doghouse ducting to the exit hole......

I believe you know the redline was supposedly 3600 rpm and everything was based on that. Porsches, being a later variant could spin much faster have different numbers. The bug street racers I knew were getting a reliable (?) 300 horse at 6 grand which would have floated stocker valves into the pistons.

[freebeard]

Valve float = shift point.

Your reversed flow needs a pic. A 3D printed fan with reversed pitch?

What I've been thinking the last few days is a supplemental fan driven off the lower crank pulley with a belt drive to raise it's location (then into the bladeless duct of course).

Whoa! Type III aluminum scroll fan and the squirrel cage.

[kach22i]

Originally Posted by Piotrsko

Might be more efficient to reverse cooling flow through the engine than duct it through the wheel wells, say perhaps with an underbody engine scoop. Couple of standard vent boxes joined at the fan inlet, couple of circumference vents on the doghouse ducting to the exit hole......

An old thread in Pelican Parts explored this, everyone agreed that with the exhaust pipes under the car pre-heating the cooling air this would be a bad idea.

One would have to flip the engine upside down to get around this I suppose.

Also the design of the fan cooling shroud is very specific and directional, another complete redesign there.

[freebeard]

An old thread in Pelican Parts explored this...

[citation needed]


http://cdn7.bigcommerce.com/s-sclwyu...1519343140.jpg

Dune buggy exhaust would work with a heat-pump heater out of a Leaf?

[Piotrsko]

Originally Posted by kach22i

An old thread in Pelican Parts explored this, everyone agreed that with the exhaust pipes under the car pre-heating the cooling air this would be a bad idea.

One would have to flip the engine upside down to get around this I suppose.

Also the design of the fan cooling shroud is very specific and directional, another complete redesign there.

I have seen exhaust systems on sand buggies that wander all over the engine in an effort to get equal length runners. Bugger to replace injectors and plugs, BUT...... ducting does not have to contend with hot air if the inlet is in front of the heat source. Or even a teepee style sand exhaust that would dump exhaust heat into the total exhaust
Backwards rotation cam and the fan now pulls air out of the engine, need to flip the ring gear in the trannie like a reduction bussie, and I do like the squirrel cage idea. I think I get 750 cfm on 1/2 hp squirrel cage fan in my house heater, maybe not. Or you can reverse rotation with a different fan belt scheme, like the serpentines on current cars runs the cooling fan "backwards". Worse case make a backwards fan since they are a brazed assembly.

I think it's doable, not sure it would be worth the effort. Freebeard: have you installed your aero software on your new computer to test your hoop concept?

[freebeard]

It was Cd that wanted CFD software tested. ecomodder.com/forum/showthread.php/can-you-test-out-free-cfd-software-39117.html

In my case, I'm watching for someone to implement CFD in the Blender physics engine. I do have Blender 2.92 running, but I've been using it to design geodesic domes.

The potential for CFD is there because Blender has implemented OpenVDB.

The Tepee header is an interesting case. One Coanda nozzle right about the license plate location. It would look like a Breer stinger (the one on the right)



Now updating this is something I could do in Blender, if I can find the Beetle model. Hmmmm, an aerospike? Minimal exhaust mixing?