robosilo
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Joined: June 2019
Posts: 15
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Post by robosilo on Jun 17, 2019 20:04:05 GMT -5
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Post by madpatty on Jun 17, 2019 22:50:23 GMT -5
That’s a really interesting setup.
I am long time fan of TP Power motor. Really impressive power in small package.
Which TP power model are you using in this setup?
Cheers.
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Post by racket on Jun 18, 2019 1:54:37 GMT -5
Hi
An interesting build .
A couple of comments , our engines use huge quantities of fuel, I'm not sure your actetylene rate of supply will be sufficient even to get up to idle .
Secondly , have you worked out the air loads on those rivets , theres a lot of surface area , the load will be in tonages , and especially troublesome on those flat surfaces , your overlap joint might burst .
Thirdly , the starter/generator shaft is pretty long , theres a good chance it'll run into problems, shut her down immediately if you feel the slightest vibration.
All the best
Cheers
John
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robosilo
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Joined: June 2019
Posts: 15
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Post by robosilo on Jun 18, 2019 7:28:56 GMT -5
A couple of comments , our engines use huge quantities of fuel, I'm not sure your actetylene rate of supply will be sufficient even to get up to idle . Secondly , have you worked out the air loads on those rivets , theres a lot of surface area , the load will be in tonages , and especially troublesome on those flat surfaces , your overlap joint might burst . Thirdly , the starter/generator shaft is pretty long , theres a good chance it'll run into problems, shut her down immediately if you feel the slightest vibration. Thanks! I too am a bit concerned with the large surface area of the chamber causing stress. It's hard to see but there are vertical straps to help reinforce the end pieces and prevent bursting. I have a pressure gauge on the compressor side to monitor this and I plan on testing this in my garage to prevent injury in the event of a bust. The shaft is definitely longer than desired but i did a runout check and i'm within .0002" T.I.R. Coupled with the o-ring cushions I'm hoping vibration will be manageable long enough to at least prove the engine to be operational. In regards to the Acetylene: if i didn't already have it i'd go the propane route. I'm hoping it will work and work well enough to idle so I know the chamber size and hole size numbers work out. After that I'll work on converting to diesel or kerosene using a dedicated fuel pump. |
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robosilo
Member
Joined: June 2019
Posts: 15
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Post by robosilo on Jun 18, 2019 7:31:02 GMT -5
That’s a really interesting setup. I am long time fan of TP Power motor. Really impressive power in small package. Which TP power model are you using in this setup? Cheers. I'm using the TP5840L model, which as I'm typing this I realize the motor is rated for 53K RPM not 75K. If this motor works well enough for initial testing i'll build new end caps for the motor that use air/oil fed ceramic bearings so I don't need to worry about life span. |
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robosilo
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Joined: June 2019
Posts: 15
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Post by robosilo on Oct 5, 2019 17:29:13 GMT -5
I finally had enough time to start testing the engine. Here is a link to my most successful, but not successful run. youtu.be/HUBxpvDAK5sI can't get the engine to run on its own. I have a suspicion that the motor i'm using to to drive the turbo is acting as too much drag. The ESC should be set to freewheel and not brake but it's hard to confirm. Ultimately I want the motor to act as a generator but if i can't get it up to operating RPM then i'll never be able to pull power from it. I might try rigging a locking bearing on the drive shaft so the motor can disengage if the engine wants to run on it's own. From the flames I was getting out of the exhaust I'm wondering if i don't have enough internal pressure. I have high flow but maybe I need to have more of a restriction on the combustion outlet to help keep the combustion in the chamber and generate higher velocity gases. Any ideas? |
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Post by racket on Oct 5, 2019 22:51:25 GMT -5
Fuel injector .............what are you using ??
Fuel .............what type and pressure ??
Fuel throttle ..........what sort ??
Cheers
John
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BFTO
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Joined: February 2016
Posts: 128 
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Post by BFTO on Oct 6, 2019 2:12:59 GMT -5
What RPMs are you achieving with that motor? and I think you must disengage the starter..
Remove the starter and try to start it with a leaf blower.
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robosilo
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Joined: June 2019
Posts: 15
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Post by robosilo on Oct 7, 2019 6:14:40 GMT -5
Fuel injector .............what are you using ?? Fuel .............what type and pressure ?? Fuel throttle ..........what sort ?? Cheers John Thanks John, my injector was a stainless spray nozzle from McMaster Carr. It's rated at 3 gallon/hour at 100 PSI. I replaced it because i couldn't get enough flow from it. I'm now using a NPT plug with (4x) .06 holes drilled in it. I get much better flow and a much narrower spray pattern. Fuel is propane from a 20 pound tank. Pressure is running between 5-15 PSI during testing. Any higher and I get a big flame output from the exhaust. Fuel throttle is just the valve from the propane tank. I have a pressure gauge on the line so i can watch the line pressure and make sure i don't exceed the 350 psi rating of the hose. |
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robosilo
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Joined: June 2019
Posts: 15
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Post by robosilo on Oct 7, 2019 6:19:24 GMT -5
What RPMs are you achieving with that motor? and I think you must disengage the starter.. Remove the starter and try to start it with a leaf blower. That's a good question. I haven't added any method of measuring RPM yet. I plan on doing another test soon and will change the timing on the motor ESC. It should allow me to increase the motor RPM. I'm not sure a reflective type tachometer will work in this case since the tape might just whip off. I'll connect my multimeter to the ESC and hopefully measure the frequency output of one of the phases. I'll report back soon. |
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Post by racket on Oct 7, 2019 15:57:11 GMT -5
Hi
You need to modify your fuel injector , 4 holes isn't enough to provide coverage of the flametube, you need at least 6 and preferably twice that number
Your injector MUST only spray RADIALLY and be positioned axially within the flametube so that the fuel sprays towards the middle row of Primary Zone wall holes , your "narrower spray pattern" is the problem , there must not be any axial discharge of fuel with the flametube hole pattern you are using , that large number of smallish holes will not produce air jets that penetrate into a narrow fuel spray, the result is generally very late combustion and very poor combustion with flames exiting the turbine wheel.
Hope this helps
Cheers
John
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robosilo
Member
Joined: June 2019
Posts: 15
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Post by robosilo on Oct 7, 2019 18:51:52 GMT -5
Hi You need to modify your fuel injector , 4 holes isn't enough to provide coverage of the flametube, you need at least 6 and preferably twice that number Your injector MUST only spray RADIALLY and be positioned axially within the flametube so that the fuel sprays towards the middle row of Primary Zone wall holes , your "narrower spray pattern" is the problem , there must not be any axial discharge of fuel with the flametube hole pattern you are using , that large number of smallish holes will not produce air jets that penetrate into a narrow fuel spray, the result is generally very late combustion and very poor combustion with flames exiting the turbine wheel. Hope this helps Cheers John that's incredibly helpful and makes total sense. I'll go back to McMaster Carr since they have a good selection of spray nozzles that have an output that is closer to what I made but sprays in a consistent cone shape that should help mix with the air better. |
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Post by racket on Oct 7, 2019 19:27:20 GMT -5
Don't think about using a spray nozzle , just use a short length of 3/8" dia tubing with the end sealed and >6 X 0.060" wall holes spraying towards your Primary air holes , keep it simple .
The passageways in spray nozzles are rather small and designed for liquids not gases , you'll probably find they can't flow sufficient gas, ..............some data from one of my nozzle brochures , a 19GPH @100psi has an outlet oriface of 0.078". but is fed internally by two 0.044" X 0.029" slots...........too small for gas .
Cheers
John
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robosilo
Member
Joined: June 2019
Posts: 15
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Post by robosilo on Oct 8, 2019 16:41:01 GMT -5
What RPMs are you achieving with that motor? and I think you must disengage the starter.. Remove the starter and try to start it with a leaf blower.
I painted a spot on the drive shaft and used my optical tachometer just now. I was measuring about 23,000 RPM before the tach started giving stupid readings. I don't know what the limit is on my cheap chinese unit, but something tells me it's around 23k. I was at about 70% throttle when I hit 23Krpm and that last 30% was definitely a lot faster. A conservative guesstimate would be 30K, maybe 35K RPM. The air flow coming out the exhaust was on par with a simple electric leaf blower. Definitely not one of those backpack units with a 2hp engine but the air coming out was considerable.
I'm not ready to give up on the electric motor start yet. Since it's my intent to use it as a generator in the future I want to see how much I can get working before I give up and grab a leaf blower.
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Post by racket on Oct 8, 2019 18:44:10 GMT -5
Hi
What size is the compressor wheels inducer ??
Any turbo in the 50-60 mm inducer range will need to idle at between 70,000 and 60,000 rpm with a 40,000 rpm self sustain speed
Cheers
John
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