|
Post by racket on Feb 14, 2023 21:47:54 GMT -5
|
|
|
Post by stoffe64 on Feb 15, 2023 1:04:48 GMT -5
Hmmm,could you explain John?....what was bad with that run?
|
|
|
Post by racket on Feb 15, 2023 3:04:23 GMT -5
Not enough thrust , my old compressor produce another 70 pounds
|
|
slittlewing
Senior Member
Joined: November 2017
Posts: 458
|
Post by slittlewing on Feb 15, 2023 16:07:12 GMT -5
Well done on getting past the starter issues and back to test running 💪
Overall it’s still got plenty of thrust! But the momentary 900 TOTs at 3.5bar AB made me wince for you 😅 It feels like the <2.5bar range would be safer to stick to at the moment for any longish power application (with AB) to avoid any damage but it’s good data.
Before you lit the AB, upto 3 bar things seemed sustainable (750ish TOT) and p4t was lower. With AB at same P2 there was another 100deg added to TOT. Almost like your current AB nozzle is about the right size to be a “dry” one?
Cheers
Scott
|
|
|
Post by racket on Feb 15, 2023 19:16:12 GMT -5
Hi Scott Yep , things got a bit hot for a few seconds Heres some numbers I extracted from the various vids . Comp effic improved with the A/B activated and a reduction in mass flow Lots to digest Cheers John
|
|
praendy2203
Veteran Member
Joined: August 2020
Posts: 162
|
Post by praendy2203 on Feb 16, 2023 2:05:15 GMT -5
Hi John,
the run itself looked stable and smooth.
After weeks waiting and problems a good test.
I would be happy to see 100 pounds on the scale with my engine😉
Andy
|
|
bigkwaka
Member
Joined: August 2010
Posts: 11
|
Post by bigkwaka on Feb 16, 2023 2:22:04 GMT -5
Looked like a positive step to Me; well done. I’m willing to bet that will be able to squeeze quite a bit more thrust out of her.
|
|
|
Post by racket on Feb 16, 2023 3:14:27 GMT -5
Hi Guys
I've been having a bit of a think on things and theres some areas for me to explore :-)
The water manometer readings at full power are the most obvious , "dry "reading showed a slight vacuum , meaning the outflow from the comp was higher than when running "wet", this higher flow rate means the diffuser isn't running choked when "wet", so I can increase mass flow by lowering the backpressure on the engine by opening up the 136mm A/B nozzle so that the manometer is running in a neutral position at full power .
The better comp effic at the lower mass flow is another area deserving attention to see if I can maintain that effic at a slightly higher mass flow , maybe half way towards the dry flow rate .
I'm also going to move my instrument panel and hopefully improve airflow to the engine , at present there could be major turbulence in the air flow attempting to get to the bellmouth , theres > 3,000 CFM trying to squeeze into that hole at the front .
Cheers John
|
|
|
Post by racket on Feb 21, 2023 16:55:26 GMT -5
Hi Guys
Been thinking on this and have come to the conclusion I need to get back to basics , there are just too many odd things going on :-(
I made the mistake of simply continuing with development using the previous jet nozzles etc etc when I fitted the new comp wheel, rather than starting again .
Afterburner is being removed and an open exhaust stub fitted with just thermocouples and pitot for P4t , might fit a flow "flag " to verify any swirl .
After reading a Paper put out by ABB turbos on a bleed slot investigation , and how the pressure at the slot varies with relative mass flow , I need to find out just how much "vacuum" I can create at the slot and the comp efficiency at that flow to get a better idea of a potential map for this wheel taking into consideration the data from my last testrun .
I've moved the instrument panel further from the engine to allow airflow from that side of the engine , hopefully a more even supply might improve the flow into the wheel and reduce any instabilities within it .
Cheers John
|
|
dieselguy86
Veteran Member
Joined: September 2014
Posts: 186
|
Post by dieselguy86 on Feb 21, 2023 19:29:57 GMT -5
John,
Any link to that paper? Sounds interesting!
|
|
|
Post by racket on Feb 21, 2023 20:36:45 GMT -5
|
|
|
Post by racket on Mar 4, 2023 0:23:18 GMT -5
|
|
|
Post by racket on Mar 4, 2023 23:56:25 GMT -5
Hi Guys
After checking the numbers it looks like I was flowing more air as the "vacuum" at the surge slot was higher than previously .
Comp efficiency was at ~75% for all but low power settings .
Spoolup went off in one go whereas it needed a couple of attempts before .
TOTs were considerably cooler despite there being a tad more P4t than when running the A/B dry .
Conclusion .............I haven't the faintest idea whats going on :-(
For the next run, I might hook up the static pressure probe at the comp inlet face to a manometer to get more accurate readings , the small gauge at the top of the panel indicated a drop of ~12Kpa , which would indicate an entry velocity of ~475 ft/sec and >4 lbs/sec
A fairing between turb exducer hub and A/B spray body is also needed to reduce turbulence and potential backpressure/losses .
Cheers John
|
|
|
Post by finiteparts on Mar 15, 2023 18:57:57 GMT -5
Hi Guys After checking the numbers it looks like I was flowing more air as the "vacuum" at the surge slot was higher than previously . Comp efficiency was at ~75% for all but low power settings . Spoolup went off in one go whereas it needed a couple of attempts before . TOTs were considerably cooler despite there being a tad more P4t than when running the A/B dry . Conclusion .............I haven't the faintest idea whats going on :-( For the next run, I might hook up the static pressure probe at the comp inlet face to a manometer to get more accurate readings , the small gauge at the top of the panel indicated a drop of ~12Kpa , which would indicate an entry velocity of ~475 ft/sec and >4 lbs/sec A fairing between turb exducer hub and A/B spray body is also needed to reduce turbulence and potential backpressure/losses . Cheers John Hi John, I am curious to hear your thoughts on what you were expecting verses what the test data told you. I haven't poured over the data like you have, but at first glance it seems to be following the trends that I would have expected, but I realize that I might not have all the information. I have been searching for a picture that I have in my collection of a J-69 being tested with a board full of manometers as the gauges that I wanted to share when I first read about your use of a homemade manometer. I am really glad to see you using one and I feel that they are cheap and easy to make and should be used more in this hobby. - Chris
|
|
|
Post by racket on Mar 15, 2023 19:28:56 GMT -5
Hi Chris
Yep , trends were in the right direction , the extra "vacuum" at the surge slot meant more mass flow , so my comp diffuser wasn't choking previously.
I've mounted the manometer ( green fluid this time) for the comp face pressure and a bit of streamlining for the A/B sprayer .
What was interesting was the lower TOTs out of the 130 mm exhaust stub , much lower than when I had the A/B fitted and running dry with its 136 mm nozzle , maybe a lot of losses from turbulence in the A/B even without combustion.
I want to do a bit of fuel flow checking before the next testrun to see if theres any issues which might be causing my P2 and P4t gauge bouncing .
On a side note ...............I've found a supplier of a 115/171 mm axial turb wheel casting , they also do the NGV ...............temptation :-(
Also a 103.6/152.8mm wheel ................they look like a scaleup of a Jetmax 85 wheel , .............reputable company in 713LC material :-)
Cheers John
|
|