CH3NO2
Senior Member
Joined: March 2017
Posts: 455
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Post by CH3NO2 on Feb 15, 2019 13:11:09 GMT -5
Depends on how much further its pushed. RPM could be a limiting factor. youtu.be/XlSPHL_nhpQBTW - Great job on the first start up. Looks like its running well.
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Post by madpatty on Feb 15, 2019 14:03:49 GMT -5
Hi. Congratulations on the successful spool up.
I wonder how the temperatures are so low at 35 psi P2. Can you share the compressor and turbine inducer/exducer measurements.
Thanks.
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Post by racket on Feb 15, 2019 18:36:29 GMT -5
Hi Gavin
900 deg F - 482 C at 35 psi P2 is understandable and ballpark for an engine with nil backpressure put on it, once a jet nozzle is installed it'll increase considerably , but keep those TOTs below ~1200 F - 650 C , we can't be certain of the wheel metal , if an old diesel type it might fail at higher temps and rpm .............don't force past 35 psi , there'll be little extra thrust to be had as the comp efficiency will be dropping which in turn consumes most of the extra energy that the increased P2 going to the turb produces...............we don't want a dead engine before you've had time to enjoy it ;-)
Cheers John
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htevo80
Member
Joined: November 2018
Posts: 36
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Post by htevo80 on Feb 15, 2019 20:26:31 GMT -5
This is the flame tube after a few runs seems a little inconsistent but overall not bad. I did start to wonder if not having back pressure was the reason for the low temps. Afterburner is next on the list of things(: the turbine wheel look good after the runs too. It's a 88mm inducer compressor and I believe 110mm exducer on the turbine. Thank you for all the help guys -Gavin
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Post by racket on Feb 15, 2019 20:39:06 GMT -5
Hi Gavin
Yep , not too bad , the inconsistancy is probably caused by the supply ducting bend forcing more air to one dide of the combustor .
With an 88 mm inducer and a 110 turb exducer theres plenty of turbine wheel to power the comp which will help keep those temps low at present.
Please do some experimenting with just a plain jet nozzle before going the A/B route , if you can optimise the plain nozzle size , keeping those TOTs below 1,200 F , its then a simple matter to calculate your required A/B nozzle size with less chance of "problems"
A plain nozzle of ~80 mm dia should be about right for you, and an A/B nozzle ~96 mm should keep backpressure low enough that TOTs won't exceed 1,200 F
Cheers John
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Post by turboron on Feb 15, 2019 21:05:33 GMT -5
Gavin, what is the clocking of your inconsistency versus the 180 degree duct bend? Are you talking about the darker areas in the liner? I agree with John that the bend will cause the velocity profile coming off the bend will be higher on one side of the combustor.
Thanks, Ron
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htevo80
Member
Joined: November 2018
Posts: 36
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Post by htevo80 on Feb 15, 2019 23:15:17 GMT -5
Gavin, what is the clocking of your inconsistency versus the 180 degree duct bend? Are you talking about the darker areas in the liner? I agree with John that the bend will cause the velocity profile coming off the bend will be higher on one side of the combustor. Thanks, Ron The welded seem of the flame is down so the soot is on the inside of the curve which makes sense the air would want to go towards the top of the combuster. Is the soot near the swirler vanes normal? Good recerculation?
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htevo80
Member
Joined: November 2018
Posts: 36
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Post by htevo80 on Feb 15, 2019 23:18:46 GMT -5
Hi Gavin Yep , not too bad , the inconsistancy is probably caused by the supply ducting bend forcing more air to one dide of the combustor . With an 88 mm inducer and a 110 turb exducer theres plenty of turbine wheel to power the comp which will help keep those temps low at present. Please do some experimenting with just a plain jet nozzle before going the A/B route , if you can optimise the plain nozzle size , keeping those TOTs below 1,200 F , its then a simple matter to calculate your required A/B nozzle size with less chance of "problems" A plain nozzle of ~80 mm dia should be about right for you, and an A/B nozzle ~96 mm should keep backpressure low enough that TOTs won't exceed 1,200 F Cheers John With that advice I will I didn't want to waste time with a nozzle but it does make sense to find the right outlet diameter. When you say "plain" nozzle does that mean just a normal cone? And if yes how long should the taper be?
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Post by racket on Feb 16, 2019 0:40:43 GMT -5
Hi Gavin
What design of afterburner were you considering ??
If you make the mounting flange to fit the turb scroll and have 4 to 6 inches of straight tubing with an ID the same, or slightly larger, as the exducer scroll shroud so that there isn't any step as the gases transition from the turb wheel into that tubing , then a simple/plain conical nozzle can be fitted to the end of that bit of tube , the tube also allows the mounting of TOT thermocouple/s and a P4t pitot tube for measuring total gas pressure exiting the turbine stage.
Taper on the cone can be 10 degrees each side, so 20 degree included , it need only be a few inches long at most
Once the engine has been sorted out its a simple matter to cut off the cone nozzle and mount the dump type A/B to that tube without disturbing anything else, its only there to put backpressure on the engine so that fuel supply and combustion can be checked at max P2 and max TOTs , when the A/B is fitted you shouldn't need to change those fuel settings , its just a case of "tuning" the A/B fuel supply and exhaust nozzle diameter to produce the same TOTs as when the plain nozzle was fitted .
Cheers John
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htevo80
Member
Joined: November 2018
Posts: 36
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Post by htevo80 on Feb 16, 2019 1:36:03 GMT -5
Hi Gavin What design of afterburner were you considering ?? If you make the mounting flange to fit the turb scroll and have 4 to 6 inches of straight tubing with an ID the same, or slightly larger, as the exducer scroll shroud so that there isn't any step as the gases transition from the turb wheel into that tubing , then a simple/plain conical nozzle can be fitted to the end of that bit of tube , the tube also allows the mounting of TOT thermocouple/s and a P4t pitot tube for measuring total gas pressure exiting the turbine stage. Taper on the cone can be 10 degrees each side, so 20 degree included , it need only be a few inches long at most Once the engine has been sorted out its a simple matter to cut off the cone nozzle and mount the dump type A/B to that tube without disturbing anything else, its only there to put backpressure on the engine so that fuel supply and combustion can be checked at max P2 and max TOTs , when the A/B is fitted you shouldn't need to change those fuel settings , its just a case of "tuning" the A/B fuel supply and exhaust nozzle diameter to produce the same TOTs as when the plain nozzle was fitted . Cheers John This is what I was planning on using. Is this still the preferred method of ab design? Also the turbo has a large v-band clamp that I can't see to find any ideas on how I could attach to it?
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Post by racket on Feb 16, 2019 2:32:19 GMT -5
Hi Gavin
Try and source a V band , maybe a large trucking exhaust shop , it should be available , V band is best .
The dump style A/B is easiest .
Also spraying fuel onto the turbine hub does work but it'll produce false TOT reading making it a dangerous practice , better to have a spray ring , checkout some of the other A/B builds , Andy M is the A/B man for advice .
Cheers John
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htevo80
Member
Joined: November 2018
Posts: 36
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Post by htevo80 on Feb 16, 2019 10:54:07 GMT -5
Hi Gavin Try and source a V band , maybe a large trucking exhaust shop , it should be available , V band is best . The dump style A/B is easiest . Also spraying fuel onto the turbine hub does work but it'll produce false TOT reading making it a dangerous practice , better to have a spray ring , checkout some of the other A/B builds , Andy M is the A/B man for advice . Cheers John I got that picture from the old Yahoo group just assumed that was convention. Where can I find example of others AB Thank you -Gavin
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Post by finiteparts on Feb 16, 2019 15:15:28 GMT -5
Gavin, what is the clocking of your inconsistency versus the 180 degree duct bend? Are you talking about the darker areas in the liner? I agree with John that the bend will cause the velocity profile coming off the bend will be higher on one side of the combustor. Thanks, Ron The welded seem of the flame is down so the soot is on the inside of the curve which makes sense the air would want to go towards the top of the combuster. Is the soot near the swirler vanes normal? Good recerculation? Hi Gavin, The soot near the swirler appears to be due to the way your combustor is set up. Usually, the exit of the swirler is inline with the dome wall, but on your combustor, the inlet of the swirler is inline with the dome wall. With this arrangement you have created a small recirculation zone in the space between the combustor dome and the discharge plane of the swirler. This recirculation zone pulls in enough fuel to make it a locally rich zone where the formation of soot is unable to be fully burned out. As for the asymmetry of the soot pattern, I would say that it is fine. It is really hard to get airflows perfectly balanced and without having very detailed measurements or a high fidelity CFD model telling you what is happening, any suggestion on why the patterns are as they are or how to get them more balanced would just be conjecture. Congrats on getting it going and I look forward to seeing more. Chris
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htevo80
Member
Joined: November 2018
Posts: 36
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Post by htevo80 on Feb 16, 2019 21:43:24 GMT -5
The welded seem of the flame is down so the soot is on the inside of the curve which makes sense the air would want to go towards the top of the combuster. Is the soot near the swirler vanes normal? Good recerculation? Hi Gavin, The soot near the swirler appears to be due to the way your combustor is set up. Usually, the exit of the swirler is inline with the dome wall, but on your combustor, the inlet of the swirler is inline with the dome wall. With this arrangement you have created a small recirculation zone in the space between the combustor dome and the discharge plane of the swirler. This recirculation zone pulls in enough fuel to make it a locally rich zone where the formation of soot is unable to be fully burned out. As for the asymmetry of the soot pattern, I would say that it is fine. It is really hard to get airflows perfectly balanced and without having very detailed measurements or a high fidelity CFD model telling you what is happening, any suggestion on why the patterns are as they are or how to get them more balanced would just be conjecture. Congrats on getting it going and I look forward to seeing more. Chris Thank you Chris. I'm still in disbelief it fired up first try. I was curious on how to mount the swirler vanes I guess jet nozzle testing will determine if they need to be moved. The flame tube is 16ga 316SS so hopefully any hotspots won't lead to stress cracks.
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htevo80
Member
Joined: November 2018
Posts: 36
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Post by htevo80 on Feb 17, 2019 0:37:15 GMT -5
You all might find this interesting on the topic of unplanned disassembly of the turbine wheel of our engines youtu.be/rNOktnFyk4U go to 7:20 in the video -Gavin
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