BFTO
Veteran Member
Joined: February 2016
Posts: 128
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Post by BFTO on Oct 14, 2017 18:23:35 GMT -5
That didn't sound good :-( Thankfully all OK . The PWM I used on my 12V EFI fuel pump regulates the negative/earth side of the current flow , and as I was feeding 24 V to the PWM , because I need the flow from ~18 V , the pump suddenly went to full voltage when I inserted the 24V starter into its mounts and made an earthing circuit through the test stand , ended up having to "rubber mount" the fuel pump to isolate it from the test stand framing , works OK now , but I really don't like PWMs , theres too many "horror stories" about them when used on our engines . Cheers John Will look into the wiring and change the PWM tomorrow if needed, have a spare unit When I switched on the fuelpump on the lowest setting (0%) it didnt respond and gave it 100% and flooded the engine. But I find the PWM a bit sketchy, what other options do I have?
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Post by racket on Oct 14, 2017 19:56:12 GMT -5
Why don't you remove the PWM and run the pump on full voltage and simply dump fuel back to the tank through a small needle valve , the one I've used on my test stand has the valve open ~3/4 of a turn during startup and then is slowly closed off as I want more power from the engine , its worked perfectly for many years , but since the 12/118 engine needed more fuel than the pump could supply on 12 volts ,I needed to fit a PWM and use 24 Volts.
Cheers John
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BFTO
Veteran Member
Joined: February 2016
Posts: 128
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Post by BFTO on Oct 15, 2017 9:31:20 GMT -5
Found the problem with the PWM, it was because the fuel tank was grounded. I will add a bypass valve on the fuel to regulate it more.Found another problem, the syringes needs to be resolder again Diesel pooled in the bottom of combustor because of two bad syringes and then it was on its own again Time to install a safety wire when the shit hits the fan next time
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Post by racket on Oct 15, 2017 17:09:06 GMT -5
Generally with a vertical combustor , fuel pooling isn't a problem because as soon as theres the least amount of air pressure within the combustor during a spoolup any fuel that is in the combustor is simply forced into the turb scroll and blown out the exhaust before the engine even reaches idle ...............you should have a drain fitted anyway , just in case .
Syringes shouldn't unsolder , they're liquid cooled , could there be another problem ??
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 16, 2017 1:56:50 GMT -5
I think it is many problems that resulted in the uncontrolled rpm increse.
1. One syringe had bad soldering and spraying diesel everywhere between flametube and combustor liner. One syringe was blocked. One syringe sprayed not correct in the evaporator. The syringes didnt unsolder.
2. The PWM on low setting is delivering way to much diesel.
I have a drain in the bottom fitted with a valve. I will install a bypass valve for the fuel and I have ordered more syringes and will ultrasonic wash them after soldering.
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CH3NO2
Senior Member
Joined: March 2017
Posts: 455
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Post by CH3NO2 on Oct 16, 2017 21:50:21 GMT -5
Hi John,
In our turbine application is VFD any better or safer than PWM?
Tony
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CH3NO2
Senior Member
Joined: March 2017
Posts: 455
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Post by CH3NO2 on Oct 16, 2017 22:17:27 GMT -5
Clean build BFTO! It's coming along very nicely.
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BFTO
Veteran Member
Joined: February 2016
Posts: 128
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Post by BFTO on Oct 26, 2017 11:02:46 GMT -5
Clean build BFTO! It's coming along very nicely. Thanks! What kind of tip speed should we set as max speed? jetspecs is saying 91750rpm, ~440m/s. Sounds a bit high? And what kind of TIT temp should we set as max? 750-800C?
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CH3NO2
Senior Member
Joined: March 2017
Posts: 455
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Post by CH3NO2 on Oct 26, 2017 18:17:33 GMT -5
Hi BFTO,
This is a question that is better answered by John. He can probably tell you based on the age of the Turbo.
Tony
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Post by racket on Oct 26, 2017 18:57:11 GMT -5
Yeh , 91,750 rpm should give a "safe" tip speed of 1450 ft/sec - 440m/s , if T I T is kept to 1450 deg F - 787 C things should also be OK , as we normally measure TOT so that the thermocouple can't go through the turbine wheel if it fails, you'll need to keep TOT to below ~650 C at max rpm , it can go a bit higher a lower rpm/P2 as there'll be less temp drop through the turb stage .
If the turbo is a good quality turbo with little usage time , preferably new , then the temps and tip speeds can generally be increased by 10% as development progresses.
Cheers John
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BFTO
Veteran Member
Joined: February 2016
Posts: 128
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Post by BFTO on Oct 27, 2017 1:52:28 GMT -5
Yeh , 91,750 rpm should give a "safe" tip speed of 1450 ft/sec - 440m/s , if T I T is kept to 1450 deg F - 787 C things should also be OK , as we normally measure TOT so that the thermocouple can't go through the turbine wheel if it fails, you'll need to keep TOT to below ~650 C at max rpm , it can go a bit higher a lower rpm/P2 as there'll be less temp drop through the turb stage . If the turbo is a good quality turbo with little usage time , preferably new , then the temps and tip speeds can generally be increased by 10% as development progresses. Cheers John Thanks John!
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Chuks
Senior Member
Joined: August 2015
Posts: 498
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Post by Chuks on Nov 2, 2017 4:51:38 GMT -5
what a nice engine, Am tempted to ask for a tutorial on AN couplings.. very flexible colorful engine!
am always struggling with bending of copper pipes that always leaks when heated.
wish to get that beautiful oil pump you have there to compare with the ''SIMRAD RPU 160 reversible pump'' that I use to have, but am just scared
of that current 105A.
Cheers Chuks
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BFTO
Veteran Member
Joined: February 2016
Posts: 128
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Post by BFTO on Nov 2, 2017 9:24:00 GMT -5
what a nice engine, Am tempted to ask for a tutorial on AN couplings.. very flexible colorful engine! am always struggling with bending of copper pipes that always leaks when heated. wish to get that beautiful oil pump you have there to compare with the ''SIMRAD RPU 160 reversible pump'' that I use to have, but am just scared of that current 105A. Cheers Chuks Thanks Chuks! The standard AN hoses is simple to assemble (You dont need a fancy AN-hose cutter or special wrenches) www.youtube.com/watch?v=PeeflgGlenYThe PTFE braided hoses is a bit more job to assemble (You dont need a fancy AN-hose cutter or special wrenches) www.youtube.com/watch?v=2vYpIaf75UIThe current draw is kinda ridiculous, need to have a big car battery to get decent runtime with this oil pump. Oil pump + 2pcs Bosch 044 + cooling fan + ignition. But the pump is working flawless, very easy to adjust oil pressure.
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BFTO
Veteran Member
Joined: February 2016
Posts: 128
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Post by BFTO on Nov 7, 2017 13:15:19 GMT -5
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Post by racket on Nov 7, 2017 15:33:02 GMT -5
Beautiful bit of stainless work :-)
Have you calibrated the A/B nozzle size , from the pics it looks a bit small in diameter ??
Also the support brace ...............is there allowance for axial expansion in the mounting holes??
Cheers John
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