|
Post by Johansson on Oct 8, 2014 0:18:31 GMT -5
Do you think that the tighter clearance will lower the temps to acceptable levels? My Swedish friend Fläppen calculated the comp efficiency during the last run to somewhere in the region of 65-68% so it hasn´t exactly been performing at its best.
I´ve ordered four thermocouples, they won´t make it here in time for the next test but I have a handful of other ones that I can use until they arrive.
Cheers! /Anders
|
|
|
Post by racket on Oct 8, 2014 1:06:17 GMT -5
Hi Anders
Yep , the tighter clearances will help with temperatures , but how far I don't know ..................LOL, I had your efficiencies up in the 70-75% range , it was only the idling one that seemed absurdly poor , but its easy to have minor "calibration" errors with our "off the shelf" measuring equipment .
Cheers John
|
|
|
Post by Johansson on Oct 8, 2014 7:31:17 GMT -5
Hi John,
Yeah, the idling numbers are a bit strange to say the least. It will be very interesting to see what difference the tighter clearance will make.
Cheers! /Anders
|
|
|
Post by Johansson on Oct 9, 2014 15:26:46 GMT -5
I fitted a second TOT probe today to find out if the high temp readings are caused by a faulty thermocouple, I also removed the jet nozzle to keep the temps down a bit. I have good readings of the temp both with and without the nozzle so it doesen´t matter. To avoid the rolling red numbers on the dashboard caused by some interference with the GoPro camera frequency I am using a different temp meter for the second TOT, it is the yellow hand held meter strapped to the rev counter. I also got a mail from my friend Fläppen, he has just calculated the compressor efficiency and it wasn´t at all that bad as I was told earlier. He will get back to me with the rest of the results once the data model is finished. He suspects that the jump at 40.000rpm is a reading error by the way. Cheers! /Anders
|
|
|
Post by racket on Oct 10, 2014 0:05:59 GMT -5
Hi Anders
I looked at some compressor efficiency numbers for the 10/98 engine and they were a bit poor up to >50,000rpm where they improved substantially , it doesn't take much of an inaccurate temp or P2 reading to throw the efficiency calculation right off , as long as its above 70% at those high P2 readings you'll be OK :-)
Cheers John
|
|
|
Post by Johansson on Oct 10, 2014 4:04:27 GMT -5
Hi John, Hmm, if the compressor ran at >70% last time then the chances of having cured the high temp issue with the improved compressor clearance are rather slim. I am putting my money on a faulty thermocouple then. If the temps are still high below 30-40.000rpm and drops off to normal at higher revs, is it really a problem for the full throttle racing? Sure it would be best if I could cure it but if I have to make a new diffuser/NGV I won´t have the bike finished for Speed Weekend this year, so the easy fix would be to modify the power turbine NGV until I get the temps at full throttle down to reasonable levels. Cheers! /Anders
|
|
|
Post by racket on Oct 10, 2014 15:39:54 GMT -5
Hi Anders
Yep, there should be a simple solution for you , that trapdoor wastegate fitted to the interstage duct will "cure" the idling temps, and with it slowly closing off as the speed rises any problems caused by the 4th stage blade angle won't be such a problem , the main thing is to have acceptable temps from say 50% N2 and upwards as thats where more of your time will be spent , accelerating to 50% won't take you very long ;-)
Cheers John
|
|
|
Post by Johansson on Oct 11, 2014 0:23:30 GMT -5
Hi John,
I still have some work on the freepower NGV to do since I by mistake made the NGV throat a couple of cm2´s tighter than the 89mm jet nozzle area, but the trapdoor wastegate idea is great. With a P2 actuated lever (aftermarket turbocharger stuff) I won´t have to manually operate the wastegate which would be a bit difficult while driving.
Cheers! /Anders
|
|
|
Post by Johansson on Oct 12, 2014 4:03:53 GMT -5
I am setting everything up for a test later today, it is raining outside so I will have the bike in the workshop and blow the exhaust out through the door. Fläppen sent me a chart of the compressor efficiency (blue line) compared to the model (red line), it looks strangely familiar with how the measured TOT compares with the ideal line. Hmmm... Cheers! /Anders
|
|
|
Post by Johansson on Oct 12, 2014 6:56:39 GMT -5
I did the test an hour ago with the open jet pipe and tighter clearance, I changed the fps setting on the camera so the temp numbers stopped rolling on the display. As you can see the new thermocouple is acting strange, not one measurement over 400°C. I have ordered a handful of the ones Ernie recommended so I will try again when they arrive. One thing I can say is that the engine sounds very VERY potent. The video sound is of course overloading but at 66.000rpm the engine is roaring like mad, and I am pretty used to loud engines with all the afterburner tests we´ve done on the jet kick. Cheers! /Anders
|
|
ashpowers
Veteran Member
Joined: February 2011
Posts: 207
|
Post by ashpowers on Oct 12, 2014 10:44:37 GMT -5
Anders,
Not sure if this may be the issue or not but not all thermocouples are made the same. Some have the junction electrically connected to the sheath itself. That caused a ton of misery for me with my setup. While they do have a faster response when built this way, it requires completely isolated circuitry to read the probe signal. I had to go to the non-grounded style to get around this problem.
You can take a quick measurement between the probe sheath and either of the two sensor wires. You should have an open circuit if they are ungrounded.
She certainly is running very well in the video - sounds great and looks very responsive! Just gotta get your gauge cluster cleaned up - looks like an electrician's yard sale! ;-)
-Ash
|
|
|
Post by Johansson on Oct 12, 2014 11:36:52 GMT -5
Hi Ash, That is something worth trying out, I´ve always trusted thermocouples to be 100% accurate but since these two differ 300°C I realize I haven´t really had a clue what temps the engines I´ve built really were producing. This is the strange bit, if numbers don´t add up there is usually something very wrong but the engine is running so sweet that I can´t understand why it isn´t producing the "correct" numbers. The heap of gauges is just for stationary testing, for racing I will only use P2, TOT and oil pressure gauges. I have an idea that I will log the T2, P4 etc etc numbers so I can check them after each race, need to talk to my electronically capable friends for that though. Cheers! /Anders
|
|
|
Post by Johansson on Oct 12, 2014 15:39:54 GMT -5
John, Now I have some fairly accurate data on the engine at its design rpm of 66.000rpm, would you mind walking me through how to calculate the angle and throat area of the power turbine NGV? 66.000rpm 725°C TOT 190°C T2 2.3 bar P2 0.45 bar P4 I think it is time to throw a leg over the old lady and do the testing on the track from now on, the engine seems to survive so I want to wrap this up, make the necessary modifications to the power turbine NGV and get some seat time out of her at Speed Weekend. The easiest way to log the data will be to permanently mount the rev counter and T2 gauge under the fairings so I can keep video logging them during the runs, I promise to make it look a bit better Ash. Here are some graphs and numbers for anyone interested: (ignore the 7°C outside temp note, I ran the bike inside the workshop where it was 15°C) Cheers! /Anders
|
|
|
Post by racket on Oct 12, 2014 18:29:14 GMT -5
Hi Anders
The numbers still aren't adding up :-(
At 66,000 rpm you have a T2 of 190 , assuming 15 C ambiant then comp rise 175 C degrees for a PR of 3.3 , that equates to a rather poor 67% efficiency ...........the comp map at 66K gives a PR near 3.5 at 74% effic , but if you're flowing over in the choke side of the map then PR and effic will be down for those 66K
Now a 175 C rise in the comp will need a drop of ~150 C through the turb .
Assuming a 5% PR drop across the flametube that gives us a 3.135 PR going into the turb at say ~875 C - 1148K , if we have a turb operating at 80% effic then we need a PR across the turb of ~2:1 , if we divide our 2:1 into our 3.135 going in we should have a PR in the jetpipe of ~1.53- 7.7psi , but you only have 0.45 bar -6.5psi
Yep , something wrong with the TOT numbers ..............if you're currently over reading by say 100 C degrees then your current P4t reading would be getting closer to the mark as more PR across the turb will be required , also cooler gas temps will allow more flow exacerbating the P2/T2 figures .
Is there any "glowing" of the exhaust bend ??
Lets get those TOT numbers sorted before we get onto the freepower :-)
Cheers John
|
|
|
Post by Johansson on Oct 12, 2014 23:18:13 GMT -5
Hi John, Hmm, I might be reading in a hot spot without knowing it. If a colder running engine would make the numbers add up I am more than willing to continue testing. Before I started the bike: At full throttle: Cheers! /Anders
|
|