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Post by turboron on Jul 9, 2020 14:26:37 GMT -5
John, I also love experimenting with something new. However, I seem to be chasing my tail trying to solve a problem most of the time.
Thanks, Ron
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Post by racket on Jul 9, 2020 16:44:56 GMT -5
Hi Ron
LOL......I know just how you feel, it can get frustrating at times , just gotta stick in there and persevere...............sometime I feel I spend more time sitting and thinking rather than doing .
But its more rewarding when a breakthrough is finally achieved :-)
Cheers John
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Post by enginewhisperer on Jul 9, 2020 20:20:54 GMT -5
I always spend more time sitting and thinking rather than doing - but it's certainly a lot cheaper (especially if the thinking works and you don't have to re-do things too many times)!
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Post by turboron on Jul 10, 2020 7:08:28 GMT -5
Think then act. All thinking does not accomplish anything. I think all of us have seen analysis paralysis in action.
Thanks, Ron
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Post by racket on Jul 10, 2020 17:27:43 GMT -5
Hi Ron
LOL .....generally in Government Departments ;-)
Cheers John
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Post by racket on Jul 17, 2020 20:36:18 GMT -5
Hi Guys All ready for another test run early next week, the exducer has another 2 mm of radial clearance so hopefully more mass flow through the engine , but I've been a bit worried that spoolup might suffer especially on these cold winter mornings so have been testing and experimenting with heating the oiltank, batteries and engine so that theres minimal oil drag and the best battery response . The oil tank pad heater has been powered up for extended periods to see what happens and it appears it needs ~4 hours before things reach terminal temps where the input equals radiant/conductive output , with bulk oil temps of ~40 deg C -100 deg F at which point the oil has thinned out nicely, so it looks like an all night heat of the tank required . The battery heating/charging regime using the little electric room blower heater for an hour seems adequate to get the chill off them . This left the engine warming , I tried using the engine's propane preheat , but it was "fiddly" as it required me to use the leafbloweretc etc, but it was quick , so decided to try something different and turned to the better halves hair dryer , just a simple 1,500W unit that I fitted through a wooden chip board "bush" pushed into the 108 mm jet nozzle, just a case of turning it on and forgetting ..........easy :-) A 15 minute operation and the engine was heated through nicely from the back end , with the alloy comp cover eventually too warm to hold the hand on for more than a few seconds , probably up ~70 deg C , the turb end even warmer, it should stay warm enough with its cover on until I get out to the test area and ready to fire her up . With everything nice and warm hopefully there'll be no problems spooling up and I can get some new running data and thrust readings to see what extra exducer clearance does to performance, either good or bad. Cheers John
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Post by racket on Jul 19, 2020 19:13:22 GMT -5
Hi Guys Bit of video from this mornings test run youtu.be/68Io36GsaSk Time to digest the numbers , ............good spoolup with everything warmed , but the fuel pump couldn't supply enough fuel at full throttle, the dump was fully closed Cheers John
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Post by racket on Jul 21, 2020 0:11:09 GMT -5
Hi Guys The "numbers" from yesterdays testrun . Mixed results , at some pressure ratios theres better thrust than before , but overall I don't think it was a success other than to indicate I need to go back a step or two . Today I blocked off the MWE slot exhausts on the comp front cover housing to see if that makes any difference and will try with a normal turb exducer shroud and a "mid way" sized jet nozzle at next testrun. Cheers John
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slittlewing
Senior Member
Joined: November 2017
Posts: 458
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Post by slittlewing on Jul 23, 2020 15:49:17 GMT -5
Congratulations John on what looked like a silky smooth test run, even if the numbers have given you a little more “tweaking” to do 😉 the thing sounds awesome!! How long do you think the TOTs at max P2 can be sustained out of interest? Is it kind of a 30 second job or continuous? Also I see you are using 2:1 petrol kero mix, is that what you have found provides optimal thrust?
Thanks for sharing your work and expertise 😊
Cheers
Scott
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Post by racket on Jul 23, 2020 16:43:48 GMT -5
Hi Scott
Those max P2 temps are only very short term ones to get an idea of how the various jetnozzle size changes are affecting those temps , certainly only for several seconds at a time .
The turb wheel is a genuine Garrett with <1 hours run time so I feel fairly confident that it should cope with 750-800 C for the TOT .
The 2:1 petrol/kero mix is being tried to minimise combustion times because of the short flametube length, as a secondary benefit its cheaper to buy petrol than kero , and the petrol is locally available , the mix is like JP-3 jet fuel used in your big long range passenger jets , it shouldn't give any more power than just straight kero or diesel .
I hope my contributions provide some inspiration for you :-)
Cheers John
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Post by racket on Aug 2, 2020 17:49:10 GMT -5
Hi Guys Just returned from this mornings test run , a bit of closeup video of the spoolup youtu.be/ongykrQyFvsCheers John
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Post by racket on Aug 2, 2020 17:55:53 GMT -5
And a vid of the run youtu.be/J29zgn7xv6gI think this is as good as she'll ever be , the closing off off the inducer bleed slot created some "changes" , I'll have to think on this :-) Cheers John
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Post by pitciblackscotland on Aug 2, 2020 18:44:36 GMT -5
Hi John, Yeah sounds like you have done a lot of work as possible to get her to a high standard of performance.
Cheers, Mark.
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Post by racket on Aug 2, 2020 23:02:35 GMT -5
Hi Mark Yep , this is about as good as I can make her. Heres todays "numbers" Thrust was good at 192 lbs , add on 5 lbs for rolling resistance and at 197 lbs thats only 9 lbs less than my original hoped for thrust , only down ~4% The best part was temperatures at that thrust , 858 and 787 C, so 833 deg C average, no 900+ C temps today . I did notice that my air/gas pressure gauges weren't as steady as on previous tests , and on throttling back to a very low idle there was a "funny noise" , I think the comp was getting closer to surge , into the unsteady air zone preceeding surge , I might need to uncover the comp inducer bleed slot again as I had it blanked off for this test . The comp efficiency numbers weren't as good as at last test where the 2mm turb exducer clearance was allowing more mass flow and possibly in a better efficiency island on the comp map, but because of the extra clearance the temps got too high , bloody tradeoffs . Jetpipe total pressure was very good today at 0.9 Bar - 13.2 psit at only a 3.7:1 PR - 39.7 psi P2 , enough to choke the nozzle ?? My fuel pressure readings were a bit sus as I forgot to fully open the small needle valve I use to control spoolup fuel flow rate on the supply line to the engine. Jet nozzle size is 108mm with a 33mm tube in the centre that fairs the turb hub , so an effective area of ~103 mm dia hole , my original design size 4 years ago called for a 104 mm nozzle , things are pretty close to those "ballpark" numbers I had initially to aspire to . Cheers John
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Post by azwood on Aug 5, 2020 20:49:39 GMT -5
Just watched the vid what a ripper
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