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Post by racket on Aug 10, 2017 23:27:32 GMT -5
Hi Erik Generally we need 30% for Primary , 20% for Secondary and the remaining 50% for Tertiary , jetandturbineowners.proboards.com/thread/680/diy-turbines ............ with your "extra " Primary and Secondary area you might find that theres not enough remaining dilution air to cool the combustion products to acceptable turbine inlet temps whilst maintaining acceptable combustion in the "excess" air in the Primary and Secondary Zones. Cheers John |
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nersut
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Post by nersut on Aug 12, 2017 8:32:26 GMT -5
Hi Erik Generally we need 30% for Primary , 20% for Secondary and the remaining 50% for Tertiary , jetandturbineowners.proboards.com/thread/680/diy-turbines ............ with your "extra " Primary and Secondary area you might find that theres not enough remaining dilution air to cool the combustion products to acceptable turbine inlet temps whilst maintaining acceptable combustion in the "excess" air in the Primary and Secondary Zones. Cheers John Hi John My bad, I remembered wrong... In my head it was 33/33/33 for air distribution. I will correct the hole sizes. Maybe weld some washers with 14 mm holes over the secondary holes to get 20 % inducer area. The tertiary holes will be bored up to 28 mm to get 50 % inducer area. The ring of 24 cooling holes with 2 mm diameter only accounts for about 1 % inducer area. In total 68 cooling holes accounts for about 3 % inducer area. The extra cooling holes should not offset the flow area too much considering the total flow area & "vena contracta" through small diameter orifice. Please correct me if I am wrong  |
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Post by racket on Aug 12, 2017 17:18:24 GMT -5
Hi Erik
A few percentage points one way or the other isn't going to be an issue :-)
Yeh , the difference in flows between plain and bellmouthed holes is going to have a bigger effect on things , generally its easier to bellmouth the bigger holes in sheet metal and is one of the reasons why I go for the 30% rather than the probably more "correct" 25% for the Primary holes , as they are generally plain holes so flowing less .
Some washers will fix the problem .
Cheers
John
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nersut
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Post by nersut on Aug 13, 2017 10:42:37 GMT -5
The holes for the secondary zone is now corrected from 18 mm to 14 mm with some washers  And the tertiary holes are also bored up to 28 mm, couldn't find a 28 mm drill bit so I used a air grinder instead.  A short piece of tube was welded on top of the combustor liner, now the combustor liner is "free-floating" & can expand & contract axially. The tube on top fits nicely with a little play in the combustor outer casing's neck & the other end (outlet) fits inside the flanges at the bottom & has also a little play.   The fuel nozzle holder is also almost done, just need some silver solder. The nozzle holder will be soldered to the original brass fire extinguisher valve (a section of it) and it seals nicely with a o-ring. A combustor drain is also made at the lowest part.   I didn't like the sheet metal pipe connector to the air inlet so it was upgraded with a heavy duty pipe now it should make a secure sealing & it fits the silicone hose (102 mm) nice & tightly.  The gab was also narrowed from 10 mm to about 5 mm.  The combustor is almost done, it only needs the spark igniter plug & a secondary (pilot/preheat) fuel nozzle. Sense the combustor liner has the swirlers at the dome I cannot put the secondary fuel nozzle there. The secondary nozzle will be a small 0,5 GPH at 100 psi (31 ml/min.), fine mist & easy to ignite with a spark ignitor. If I placed the secondary nozzle from the sidewall near the dome maybe with an angle towards the exhaust there should not be any issue with excessive heat on the opposite wall due to the nozzle placement?
Cheers Erik |
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Post by racket on Aug 13, 2017 17:10:19 GMT -5
Hi Erik
Yep , the heavy duty ring at the flexible joint is needed for a good seal .
I had my start gas fed in around the main fuel nozzle on my TV84 , but if you want to use a second nozzle and liquid fuel you'll need to have it "upstream" of the spark ignitor so that the mist flows "downstream" with the start air going, it could be a tricky setup to get working efficiently .
Your flametube is fairly thick walled so I don't think a short duration heating from a start fuel spray will affect it too much , it might be easier to simply fit the nozzle straight into the side wall , the airflow within the flametube will very quickly "bend" the spray over to a more axial flow , the ignitor might need to be some distance downstream for it to have a fuel mist impact it .
Cheers
John
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nersut
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Post by nersut on Aug 16, 2017 5:12:03 GMT -5
Hi Erik Yep , the heavy duty ring at the flexible joint is needed for a good seal . I had my start gas fed in around the main fuel nozzle on my TV84 , but if you want to use a second nozzle and liquid fuel you'll need to have it "upstream" of the spark ignitor so that the mist flows "downstream" with the start air going, it could be a tricky setup to get working efficiently . Your flametube is fairly thick walled so I don't think a short duration heating from a start fuel spray will affect it too much , it might be easier to simply fit the nozzle straight into the side wall , the airflow within the flametube will very quickly "bend" the spray over to a more axial flow , the ignitor might need to be some distance downstream for it to have a fuel mist impact it . Cheers John Okay thank you, I will try to put the secondary nozzle as close as possible & angle it downwards. I am trying to calculate the required fuel flow rate to reach max power. With a air mass flow rate of 2,07 lbs/sec. (calculated with JetSpecs) and air to fuel ratio of 50:1 (Diesel density, 840kg/m 3) I would need about 21 US gal/h fuel nozzle. For self sustained/idle operation what kind of fuel flow percentage is usually needed compared to max power? Cheers Erik |
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Post by racket on Aug 16, 2017 17:00:54 GMT -5
Hi Erik
I'd cut back on that mass flow rate , I found ~1.8 -1.9 lbs/sec was the best flow , requiring a 76mm dia jet nozzle .
When I had an 11 US GPH fuel nozzle installed , my max fuel pressure was 600 psi , take off the 40 psi P2 and we had ~560 psi pressure drop , square root 560 = 23.6 , or ~2.3 times the rated flow , so ~25 US GPH , but I was running TOTs of ~800 C .
Depending on your idling P2 you might be needing ~25% of max fuel flow , they're very thirsty even when idling .
Hope this helps :-)
Cheers
John
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nersut
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Post by nersut on Aug 17, 2017 12:23:14 GMT -5
Hi Erik I'd cut back on that mass flow rate , I found ~1.8 -1.9 lbs/sec was the best flow , requiring a 76mm dia jet nozzle . When I had an 11 US GPH fuel nozzle installed , my max fuel pressure was 600 psi , take off the 40 psi P2 and we had ~560 psi pressure drop , square root 560 = 23.6 , or ~2.3 times the rated flow , so ~25 US GPH , but I was running TOTs of ~800 C . Depending on your idling P2 you might be needing ~25% of max fuel flow , they're very thirsty even when idling . Hope this helps :-) Cheers John Hi John Thank you for the information. I have different fuel nozzles to play with I could try to fit a about 5 US gal/hr. as main nozzle to start with to be able to get self sustaining state (idle) & test oil pump/pressure/cooling before throttling up to higher power. Cheers Erik |
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nersut
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Post by nersut on Aug 17, 2017 12:45:59 GMT -5
The old oil tank used on the FJK1 & FJK2 was reused, I modified the corner to save some space in the frame & mounted it. The fitting for the turbo oil return line was also relocated.   I will make a heat shield for the turbine scroll after all the piping is routed to protect the surrounding components from radiant heat. Here is a mock up for the oil filter, oil cooler & dual radial cooler fan location.   Cheers Erik |
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Post by stoffe64 on Mar 22, 2018 4:52:17 GMT -5
I started to fabricate a tubular frame for the turbine. The base is semi done, and here is the turbines location. Compact but there should be enough room for the accessories. When finished it should look like one of those portable generators in shape.   The combustor has a slight downward tilt to the "colder side" for fuel drainage purpose. I have a similar adjustable air pressure regulator to this in the picture below. I will try to use it to regulate the oil pressure (pressure dump). It can handle pressure up to 10 bar & able to flow 550 liters of air/min. They should be able to handle oil as they also usually are paired with a oil/moisture separators. 
Cheers Erik Would such air regulator really work for engine oil?,would it survive the heat from the oil after the engine running for a while..... Interesting if it works! Cheers /stephan |
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