HC5A Kart build

[ausjet]

Got some tig time today, here’s the finished fuel tank which will hold 12L.


Started fabrication of the oil tank which should hold ~8L



Here the roughly finished oil cooler mount

[slittlewing]

Looks like you’re very handy with a tig!!

Nice work

[ausjet]

I was given an offcut of perforated sheet from a local engineering shop. What do you guys think of this as a de-airation plate? I’m thinking the holes are a bit too large at 11mm. I could restrict them down a bit to say 8mm which may be more effective.

[turboron]

ausjet, I have never seen any guidance or design information on the size of aeration plate holes. If the oil drains are not inline with the holes I don/t see how it could make a difference.

Thanks, Ron

[azwood]

I don't have a plate in mine but the tank is a big tube works great so far I wouldn't stress to much man the main thing with any turbo is to have a big return line and have it obove oil level and facing down hill I've seen many die from bad drainage problems just go big on the return mine is 1in.

[finiteparts]

Hi Ausjet,

Make sure to include a large vent on the oil tank. Since the turbo shaft seals are "dynamic" seals, there is a normal amount of leakage from the compressor and turbine flows that will be at a higher pressure than ambient. Without sufficient venting, you can pressurize your oil tank and potentially rupture it.
Since the tank has a large internal surface area and is really not designed to be a pressure vessel due to the 90 degree interfaces.

Good luck!

Chris

[azwood]

Dec 6, 2019 22:34:05 GMT -5 finiteparts said:

Hi Ausjet,

Make sure to include a large vent on the oil tank. Since the turbo shaft seals are "dynamic" seals, there is a normal amount of leakage from the compressor and turbine flows that will be at a higher pressure than ambient. Without sufficient venting, you can pressurize your oil tank and potentially rupture it.
Since the tank has a large internal surface area and is really not designed to be a pressure vessel due to the 90 degree interfaces.

Good luck!

Chris

Yes I agree have ample venting I use a catch can

[azwood]

Can't wait to you fire it up suddenly it all seems worth the work

[cchange4us]

Hows the progress on this beast? I really admire your metal fab skills.

[Colin Heath]

Aug 16, 2017 18:36:03 GMT -5 finiteparts said:

Hi Tony,

Sure that would probably work well for simple combustor. There were a few papers back in the 1970s or '80s that used fuel impingement on a surface as a means to breakup the liquid into smaller droplets and then having the sharp edge on the plate allowed for further flow shearing of the sheet, basically a simple airblast atomizer. Rolls explored several impingement atomization schemes for use in the RB162, which was a lift jet engine (when they were exploring other avenues to make supersonic VTOL aircraft propulsion systems). They had several schemes that used single jets impinging on scrolls and angled plates in the airflow to produce small droplet clouds. My guess is that they were not that successful, since I haven't heard about them since. I will see if I can find some of those papers.

The things that come to mind to look out for are:

1. The disc has to be attached to the dome somehow and the struts or mounting features might collect liquid fuel causing locally heavy fuel concentrations. You could probably get around this by shaping the struts to be thin and sharp in the radial direction, offering the least amount of wetted surface for the fuel to "stick" to. If the struts are too "big" the droplets will collect and coalesce into larger droplet that might cause combustion issues when they are shed off the strut into the passing flow.

2. The flow through the gap between the disc and the dome should be sized to get as high a flow speed as practical, while making sure that you are getting sufficient primary zone air. You want to impart a high level of kinetic energy to the airflow because that is the mechanism for breaking up the fluid into smaller droplets. It takes energy for a large droplet to break up into smaller droplets, because of surface tension. When you break a large droplet into a bunch of smaller droplets, you increase the surface area between the liquid and the air...this means that for a given amount of liquid, there is a larger overall amount of surface tension. You can provide the energy needed to for the additional surface tension by imparting kinetic or thermal energy to the fluid. Vaporizers do this by providing thermal energy, but to mechanically atomize fluids, you can push the fluid with a pump to high speeds or you can use the energy in high speed airflows to increase the fluids kinetic energy. The higher energy fluid can then be perturbed, which will allow it to break apart into smaller droplets. Keep the edge as sharp as possible to help "break" the liquid sheet and get the air flows on either side introduced to the liquid sheet as rapidly as possible.

3. There will be a stagnation point in the recirculating flow ON the hot side of that disc. That means you will likely hold the flame on the back side of that disc. You might want to bring your injector fairly close to the cold side of that disc so you make sure the fuel cools the disc as effectively as possible. You might even want to use a solid cone injector to make sure the center of the disc receives fuel droplets to cool the metal.

Good luck!

Chris

Sorry to drag up such an old post but I am reading through threads to help my build and this reminded me of machine I have worked on.

Carbonation machines for drinks use this very type of action to ensure consistent CO2 levels. They use a cone arrangement that the liquid hits at high speed causing the liquid to more easily take up the CO2 in the pressurised vessel.

Although we are already creating that cone with the nozzle so not sure if another cone would help or hinder. The sharp plate makes more sense to create shear.

[ausjet]

Progress is slow. But still moving forward 👍🏻 I did a bit more research on oil foam separation so changed the perforated plate to a wire mesh setup. I’m currently in the middle of mounting the tank to the chassis then need to sort out the oil and fuel systems.

[racket]

Nice tank

Have you added a "baffle" at the oil outlet to prevent a suction votex forming ??

If your oil "in" is positioned near the oil "out" you can end up with only part of the tanks capacity in circulation with longish shallow tanks .

Cheers
John

[ausjet]

Jan 26, 2020 17:49:15 GMT -5 racket said:

Nice tank

Have you added a "baffle" at the oil outlet to prevent a suction votex forming ??

If your oil "in" is positioned near the oil "out" you can end up with only part of the tanks capacity in circulation with longish shallow tanks .

Cheers
John

No I never thought a baffle to prevent a suction vortex! Thanks for that. I’ll have to do some testing with a clear suction tube to see if it will be problematic seeing as I’ve welded the lid on now 🤦🏻‍♂️ Might have to see again if I run into cooling issues regarding the outlet being in the same area as the inlet. More than half of the oil will be in the rear section as I’m mounting both the oil and fuel tanks with a backwards tilt to match the angle that I’ve sloped the tanks

[racket]

At times I've used the oil pickup from an auto engine , they have a large mesh surface to prevent big chunks of crap getting to the pump , and the "hood" of the pickup prevent the vortex as the oil flows through the long gap between hood and tank floor

[ausjet]

Rubber mounted both the tanks the other day. Hopefully this will still allow some flex between the main frame and the side pod carriers- not that I’ll be competing against anyone 😂







Now onto the fuel and oil systems. I had been collecting parts for this project many years before I started building it. Finally it’s come in handy!



The Seastar marine hydraulic steering pump is a nice little unit for a fuel pump, doesn’t draw much current, puts out a healthy 500psi but overall falls short on flow. I think it would work but could limit full power.
200psi 5a 1l/min
300psi 8.3a 0.75l/min
I have a 15.5 and 20gph nozzles.

I was planning to use the oberdorfer pump for the turbo oil supply but maybe it wouldn’t be a wise move. The motor got hot and generally struggled whilst flow testing it. Got 5.6L/min @80psi pulling 30amps. (Testing with kero) The Holset manual for the hx82/hx5a spec is 3.5L/min at idle and a min of 6L/min at full engine torque. I ordered the tried and tested Marco UP10 which should do the job with ease. (9.6L/min @ 80psi pulling ~21a)

The Astra electric power steering pump is an interesting one. It’s flow compensated or has some sort of displacement controller inside. When the outlet is restricted and pressure builds, the pump speeds up by itself and flow stays fairly constant. It’s quite heavy and bulky though.

The 24v hydraulic pump running off 12volts showed promising results as a fuel pump. Just hope it survives pumping kero instead of oil.
12.9 volts netted the following:
200psi 9.5a 1.4l/min
300psi 11.8a 1.35l/min
500psi 16.4a 1.15l/min

With all this testing the shed now has a permanent kero smell to it. Not such a bad thing I suppose