APS/Ω Gas turbine bike build

[bbarn]

Any chance of catching bleed air at shutdown and blowing it through the injectors? Might be beneficial in the long run to clear the system beyond the fuel pump and remove any fuel particles/soot sources from the system.

[Mobacken Racing]

Any chance of catching bleed air at shutdown and blowing it through the injectors? Might be beneficial in the long run to clear the system beyond the fuel pump and remove any fuel particles/soot sources from the system.

That would only complicate the plumbing and add the risk of dirt entering the fuel manifold from the unfiltered compressor discharge air.

It is not really a problem since I only race the bike once or twice every year and tear it down during off season to check the  engine for signs of wear or cracks in the hot section. No extra trouble doing a quick propane flame check and possibly exchange one or two injectors.

Cheers!
/Anders

[JoshH]

Curious. What's your plan to compensate for the larger injectors?

[Mobacken Racing]

Curious. What's your plan to compensate for the larger injectors?

You mean how to adjust the fuel rate to make the engine run as before?

I´ll simply back off on the PWM controller a tad to lower the fuel pump revs, a gas turbine is similar to a diesel engine in that the A/F ratio is self adjusting. The more fuel you feed it the faster it´ll spin, it is as simple as that. No tricky balancing act like with a petrol engine where you have to tune a carb or map the fuel injection.

Cheers!
/Anders

[Mobacken Racing]

With the new injectors in place I had no reason to keep the engine in pieces any more, so I started assembling it tonight.



Thr hot side looks remarkably healthy considering the abuse it has been through over the years.



The compressor must have digested something during the last race, the leading edges in the inducer blades had several small dents that I blended out with a small file. I might fit a new compressor wheel after next years racing depending on how much damage the water injection will do to it.



I borrowed a boroscope to check the gearbox internals for wear, the gear mesh wear looks ok to me but I think I´ll tighten it up a tenth of a millimeter or so since there is a bit much shaft play rotation wise before the teeths interact. It might be a tad larger than last year, perhaps because the shafts and everything has settled in properly after last years assembly.



Cheers!
/Anders

[Mobacken Racing]

A couple of evenings ago I assembled the engine and took a few pics of the thread locking and other stuff you´ve seen a dozen times before, but all of a sudden the SSD drive in my Macbook burned out...

Luckily I had made a copy of the hard drive only a few days before so I managed to restore almost everything on the computer, if not 20 years of project pictures, videos, turbine info, family pics etc etc would have been forever lost. Moments like this makes you realize just how much important stuff from your life that is being stored on computer drives...



I went outside and took these pics to show that the engine is installed in the bike again, look just how much space there is now! Fitting the engine before was a tight fit for sure but now it can just be placed there without any problem at all. Nice!



Cheers!
/Anders

[Mobacken Racing]

[Mobacken Racing]

I am working on making the fuel and oil lines now, with them in place I can start planning for 3D printing an air intake bellmouth and have a water injection manifold strapped to it.

The fuel filter was fitted tonight along with some oil lines.



I am still waiting for the fuel pressure gauge that will be fitted to the threaded adapter just downstream the filter, hopefully it will turn up soon along with some other stuff I´ve ordered.



I ran out of AN6 braided hose so I need to buy a couple of meters more before I can finish the oil lines.

Cheers!
/Anders

[Mobacken Racing]

I made a water injection spray nozzle holder last night.



I have another of these nozzles so in case one can´t flow enough it is a simple task fitting a second one to the water injection system.



I test flowed it with the small membrane pump I bought for this and got a flow rate of 0.8L/min at an unknown but supposedly not very high pressure, the spray pattern was a bit weak so I think that a better pump will improve both flow and spray pattern quite a bit.



I welded on a pair of AN6 fittings to the water tank and nozzle manifold today so I could do another flow test with my much larger Flojet pump that I used as an oil pump for my old jetcart.



Tank fitting welded and old kero boiling off inside the tank, Anna told me I smelled wonderful when I got back in the house.



This time the nozzle performed much better, 1.2L/min at 6.5kg water pressure with a pretty nice spray pattern.



In theory I could have two of these but I think I´ll try a single one first to see what happens.

Cheers!
/Anders

[Mobacken Racing]

Now that I know that the pump can flow enough water through the nozzle with a decent spray pattern I can start fitting the water injection system to the bike.



Last night I modelled a pump bracket in Inventor and started a 10 hour print before I went to bed, and when I got back from work this afternoon the bracket was waiting for me in the 3D printer. Neat!



After cleaning out some supports in the zip tie holes and threading two holes for M5 screws the bracket was finished.



Here the water pump is fitted to the upper frame tube, a good place to put it now that the air intake tunnel is out of the way.



I also fitted the water injector to the bike.



The angle is set so the center of the spray cone hits the compressor inducer slightly below the compressor hub.



Knowing that the tractor pulling guys inject massive amounts of water into their diesel turbos with little or no atomization of the water (some times just a plain water nozzle pissing water into the compressor inlet) I think this will work just fine. We´ll soon find out.

Cheers!
/Anders

[Glen]

You are running out of room for any more parts and pieces, maybe a side car, LOL. to carry more.

[Mobacken Racing]

You are running out of room for any more parts and pieces, maybe a side car, LOL. to carry more.

Actually there is plenty of room now that I retired the air intake tunnel.

[Mobacken Racing]

Today I think I assembled the last steel braided hose for a while, there must be a kings ransom in AN couplings on the bike by now...



I made a hose from the water tank to the pump and onward from the pump to the spray nozzle, I considered fitting a pressure gauge somewhere between pump and nozzle but decided not to since I can´t look at it while riding the bike anyway.



Time to start sorting the wiring out!

Cheers!
/Anders

[saltwheels262]

I can´t look at it while riding the bike anyway.

It might come in handy when it is on a stand during a test fire.

Franey

[Mobacken Racing]

I can´t look at it while riding the bike anyway.

It might come in handy when it is on a stand during a test fire.

Franey

Not really, the water injection is only meant to be activated above 2 bar boost pressure. I can´t run the bike that hard in the pits since the temps get too high when the rear wheel isn´t spinning.