|
Post by Johansson on Oct 13, 2014 1:54:39 GMT -5
Looking at the picture of the hot jet pipe there seems to be a hot spot at 9 o´clock and one at 6 o´clock where the thermocouple is. The top of the pipe seems to be running colder if the ambient light isn´t playing tricks with the camera so I will try to fit a new thermocouple at 12 o´clock and a bit further downstream and spool her up again this week. Good thing I can test the bike indoors, when I get home from work it is pitch black outside this time of year.
|
|
|
Post by smithy1 on Oct 13, 2014 13:34:17 GMT -5
Hi Anders, Looking at your pics and video, the jet-pipe is just a little "Cherry Red"....most of the stainless steels we tend to use will start to "colour up" as they pass through ~620C, if this is the case your TIT is well within the good range. In my humble opinion, your engine is running very nicely, it's smooth, responsive and sounds great. You may be having some "instrument" issues but the engine itself is running sweetly and making all the right noises... with good oil pressures too. Your testing has shown it is easy to start and accelerates easily from the lower P2 pressures. If the engine wasn't running properly it obviously wouldn't perform as well as it does.
Do as John suggests with the PT and you won't go far wrong.
With the "hot spots", don't be too worried, I own quite a few commercially made mini-turbines and they still have hot spot issues, the manufacturers just fit the thermocouples where the hot spot isn't..!
Just for interest, what type/grade of lube oil are you using??
You should be very happy and proud of your work, I really enjoy watching your progress.
Cheers, Smithy.
|
|
|
Post by Johansson on Oct 13, 2014 15:13:14 GMT -5
Hi Smithy, That warmed my heart you know, it is easy to go all boohoo about some minor issue and forget about the larger picture that I´ve actually built this damn thing from blocks of metal and it works! I have filled the scuba tank tonight and fitted a second thermocouple identical to the one I am already using in the place at 12 o´clock near the end of the exhaust pipe where the faulty thermocouple was during the last run. A location 20-30cm downstream the turbine should place the probe well away from the possible hot spot that is fooling my other probe. I am using 10/40 synthetic oil, regular automotive stuff. Thanks mate! /Anders
|
|
|
Post by Johansson on Oct 13, 2014 15:52:06 GMT -5
Here is another video from yesterdays run, here you can more clearly see the color of the jetpipe along with some swaying bushes next to the road outside. Cheers! /Anders
|
|
|
Post by smithy1 on Oct 13, 2014 16:01:11 GMT -5
Hi Smithy, That warmed my heart you know, it is easy to go all boohoo about some minor issue and forget about the larger picture that I´ve actually built this damn thing from blocks of metal and it works! I have filled the scuba tank tonight and fitted a second thermocouple identical to the one I am already using in the place at 12 o´clock near the end of the exhaust pipe where the faulty thermocouple was during the last run. A location 20-30cm downstream the turbine should place the probe well away from the possible hot spot that is fooling my other probe. I am using 10/40 synthetic oil, regular automotive stuff. Thanks mate! /Anders Hi Anders, Thanks for the info.....and good luck with your next run, be sure to take plenty of video for us. The thermocouples on my 6041 go-kart are ~120mm downstream of the turbine, John had them fitted directly opposite each other at 9 and 3 o'clock, they work very well and are always within 20c of each other during a run, at ambient temps they are spot on, this points to a tiny difference in temps on each side of the pipe but nothing I'm worried about. I've never seen the EGT exceed 700c, even during one of my poor starts. EGT's @ idle (~4.5psi P2) is only ~460-480C....so there's plenty of room to play. Cheers, Smithy.
|
|
metiz
Senior Member
Joined: April 2011
Posts: 297
|
Post by metiz on Oct 13, 2014 16:03:43 GMT -5
Nice run! also: scared cat @0:37
|
|
|
Post by racket on Oct 13, 2014 16:36:47 GMT -5
Hi Anders
Yep , keep an eye on the big picture .............its looking very nice :-)
Cheers John
|
|
|
Post by Johansson on Oct 14, 2014 4:32:34 GMT -5
Hi Anders, Thanks for the info.....and good luck with your next run, be sure to take plenty of video for us. The thermocouples on my 6041 go-kart are ~120mm downstream of the turbine, John had them fitted directly opposite each other at 9 and 3 o'clock, they work very well and are always within 20c of each other during a run, at ambient temps they are spot on, this points to a tiny difference in temps on each side of the pipe but nothing I'm worried about. I've never seen the EGT exceed 700c, even during one of my poor starts. EGT's @ idle (~4.5psi P2) is only ~460-480C....so there's plenty of room to play. Cheers, Smithy. Hi Smithy, I´ll make sure to get some video material from the run, it is a bit difficult to decide whether to use the external video or the dashboard video when I make the final youtube video but I figure that seeing the dashboard gauges is more interesting than watching a bold guy standing next to a motorcycle. Cheers! /Anders Nice run! also: scared cat @0:37 He he, not the first time scared cats can be seen running away in my test videos... Hi Anders Yep , keep an eye on the big picture .............its looking very nice :-) Cheers John Thanks! The temp issue is just a minor bump on the road to success.
|
|
|
Post by Johansson on Oct 14, 2014 13:02:08 GMT -5
I ran the bike today to test the hot spot idea, I forgot to start the gopro camera so it starts when the engine is at full throttle. The damn reflections in the gauges are a constant pain in the ass, can´t see if I have them until I download the video into the computer after the run... Anyway, the new thermocouple downstream the old one shows even higher TOT. I looked up the exhaust with the engine at idle and the TOT at a supposed 700°C and the probe wasn´t glowing at all, the duct had a faint deep orange glow to it but I couldn´t see any signs of hot streaks that could fool the probe. In the middle of the run there was a loud POP and I quickly shut down the engine expecting the worst, but it was only the oil tank that had split a seam due to thermal expansion. John pointed this out to me during the build process and I did leave a bit of room for it to grow but not enough apparently, good thing it happened here in the workshop and not on the race track. I will completely disassemble the engine now to check everything out, test flow the syringes etc. If I can´t find anything wrong, should I do a test and block one of the NGV channels off? I will do some calcs to find out the total NGV area with and without the blocking plate, feel free to come up with suggestions about it because that is all I can think of right now in order to cure the temp problem. Cheers! /Anders
|
|
|
Post by racket on Oct 14, 2014 15:46:55 GMT -5
Hi Anders
LOL.............that tank splitting would have made me jump too ..............bugger .........we always think the worst when we hear things like that when under power .
"Interesting" that the thermocouples were showing the temps they were , yep, a check inside the engine is called for , something ain't right when you have those temps with an "open pipe" .
Is it possible for you to have your thermo setup checked for accuracy ??
I once check mine by fitting/threading both thermocouples into each end of a short section of 25mm round bar, then heating the bar in the middle with the oxy torch , theoretically the air gap in the middle should have been the same temp for both thermocouples .
We might need to check your turb wheels dimensions/angles as well just to make sure nothings "off design"
Cheers John
|
|
|
Post by Johansson on Oct 15, 2014 4:39:02 GMT -5
Hi John, I saw in my mind a winter filled with machining when the bang came, but since the engine spooled down like normal I figured it couldn´t be a complete mess. Hopefully my new thermocouples will arrive soon, I´ll try to test the old ones against the new to see if there is any difference. I´ll start disassembling the engine tonight to see what I can find. Since the compressor efficiency seems to be within limits, can I assume that the diffusor is ok and focus on the parts downstream? If the diffusor angles would have been wrong it would show on the T2 readings, right? I remember measuring the NGV throat area and it was larger than yours, but I can´t find the email where the numbers are. I am pretty excited about measuring it, I hope to find that blocking one slot will bring the area down to the 31.6cm2 I was aiming for from the beginning. There is some minor leakage around the NGV studs, air and a bit of oil has seaped out but when I check the engine case drain there is not a single drop of oil coming out. Not enough leaks to affect the TOT in any noticable way though. Cheers! /Anders
|
|
|
Post by Johansson on Oct 15, 2014 15:10:22 GMT -5
After a long, long day full of anticipation I finally could pull the engine apart to check out the internals. What would the core look like after several minutes of full power runs with high temps? Unbelievably good actually! The NGV section looks fine with the coating still in place although a bit discoloured, vapor tubes ok as well, some slight rounding around the end of the tubes but I had to look for it to see it. The guide vanes are still as sharp as they were when they were new, hard to believe since they are the most exposed pieces of metal in the engine. The combustor is looking like new as well, no cracks or dents anywhere. The turbine wheel has some burned oil deposits near the blade roots, might be some minor oil leak past the shaft seal. Other than that it looks fine, no signs of heat soak past the rear bearing. I removed the fuel manifold and tested it with propane, it was difficult to take a good picture of it since I had to hold the preheat button down to keep the propane flowing. No blocked syringes but two of them were flowing a bit less than the others so that will be adressed later. And now to the main attraction, the NGV throat area! *drum roll* I finally think I´ve nailed the temp issue, the throats measures 10mm x 19mm which calculates to a total of 34.2cm2. Take away the impingement nozzle area and I end up at 33.7cm2. That is not exactly near the 31.6cm2 I should have had. If I block one of the passages I get a total of 31.8cm2 which is close enough I think, might be worth a try before I go ahead and make a completely new NGV. Cheers! /Anders
|
|
|
Post by racket on Oct 15, 2014 15:59:50 GMT -5
Hi Anders
BORING....BORING...... BORING .............no broken bits , I wanna see broken bits ;-)
Bits look in good condition , theres even some shiny inconel at the turb hub , cooling is working nicely , .................is the "black" deposits soft or hard , it doesn't look like the wheel has been overheated .
Yep , NGV area might be a bit big .
One thing I'd like some info on is the turb exducer , just looking at the pic it appears as though its fairly "open" , could you measure the angles and maybe post a couple of pics please .
Heh heh , nope, not a lot of machining over winter :-)
Cheers John
|
|
|
Post by Johansson on Oct 15, 2014 16:07:25 GMT -5
Hi John, I´ll get some pics and measurements of the turbine taken tomorrow evening, now it is time for bed. Cheers! /Anders
|
|
|
Post by smithy1 on Oct 15, 2014 16:11:26 GMT -5
Hi Anders, I wouldn't call it a "Big F@#k-up". She looks pretty good in there, not much in the way of burnt or bent bits.! The shaft bearing surface looks good too, no real heat soak evidence on the shaft either...I think that's further evidence of the TIT's being in the "OK" range, if the TIT's were too high we'd see some "blue-ing" of the shaft.
It might pay to check the "roundness" of the oil ring sealing face in the rear housing, might be where the oil is getting through, do you have a new/spare ring to use? Or possibly the a high differential between oil pressure vs the pressure at the back-side of the turbine.
Cheers, Smithy.
|
|