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Post by rocketman_mike on Jun 18, 2023 21:00:18 GMT -5
if the weather cooperates here, Im going to disassemble the CC and get some gaskets made to seal up the leaks I found. I have some concerns with the EGT gauge that went dead today, hopefully it's just a bad ground. Also going to begin figuring out a fail safe for oil system. I noticed some of you are using oil pressure switch as a means of killing the fuel pump if you lose pressure. I actually really like that and would like to incorporate that into my system. My oil pressure gauge was on the fritz this morning. I wasn't reading any pressure, but eventually freed up, possibly passed an air bubble through the system or maybe the gauge itself was stuck, needless to say, I want that looked into. www.youtube.com/watch?v=FD2eKV2OGY4 |
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Post by racket on Jun 18, 2023 21:37:32 GMT -5
Yep , oilpressure interlock with the fuel pump is a must have item , Hobbs switch and a relay , its very easy to have an oil pressure problem that goes unnoticed in the heat of the moment , its cheap insurance .
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Post by rocketman_mike on Jul 7, 2023 18:41:05 GMT -5
Rocketman Maddox has fabricated an exhaust nozzle for me and will be shipping it soon. I cant wait to get it welded on. I asked him to make the exit a little smaller so I can test it and trim it back as I need. Afterburner is almost done. Once I have the nozzle welded on, all I need is a threaded bung for a spark plug welded on, so I'll have them both done at the same time.  I haven't done too much since I got it started on father's day. I've been busy with dating and learning how to be human again. I took the kart to another car show at the local warbird museum and everyone loved it even though I didn't start it (safety reasons being in mind). I'd like to keep experimenting with it and feel it out before trying to start it near a crowd.  I was challenged to a race against Adam's pulsejet-powered sled. He's back in Canada this week getting it packed up to bring back here to Florida. He's also bringing some extra fuel pumps and bits from a past turbine build. Im excited to see this thing when he gets back. I tried building a pulsejet when I was maybe 14 or 15, but I made it too small and had issues getting it to self sustain because my reeds were too thick and the only way it would run was by forcing air into the intake. Adam built his engine with Maddox's plans, so Im very curious how this witchcraft works. I thought he said it pumps out about 100 lbs of thrust. |
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Post by racket on Jul 7, 2023 23:01:23 GMT -5
Be careful with the small nozzle , your temperatures can get too high very quickly because of the increased backpressure .
LOL....PJs are a great way to annoy neighbours
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Post by rocketman_mike on Jul 21, 2023 19:39:11 GMT -5
making some progress on the afterburner nozzle. It's just about ready to be welded together and the nozzle trimmed back a bit. It's just been too hot to do anything outside and I've been about as distracted as a crackhead 6th grader in a toy store. I managed to remove the AB fuel pump from it's original location and going to relocate it somewhere a little easier to access and not so close to the ignition system. I revisited the brakes again and did some more brake bleeding. I think I still have an air bubble stuck in the system, so we'll come back to that. I've been diving down the Arduino and Raspberry Pi rabbit hole the last couple days. I would like to eventually have a Pi dash display and an Arduino Uno and DC motor shield to control/monitor the engine. Im just not quite up to speed on the electro-digical bleep bloops. Unlike my millennial peers, who were learning how to program computers in high school, I was tucked away in a blacksmith shop on the edge of a cornfield in Maryland, learning how to forge knives and swords from car springs. HAHAHA. I guess some of us are just cut from a different cloth. Anyway, Not sure when I'll fire it up again. I'd like to have Adam with me again for an extra experienced set of eyes, but he's run back to Canada for another week to pick up some more things. But, when we do fire it up, we'll crank up the pressure on the diesel and see if we can get an idle on liquid fuel. We had a decent idle on propane despite having some pressure leaks around the combustion chamber. I also want to keep a closer eye on the oil temperature. We had solid 40 psi the entire couple of minutes it ran, but I don't recall seeing anything for oil temperature. Between the adrenaline rush of hearing this fire up for the first time and being distracted by a concerning lack of readings on my TIT gauge, I didn't hit the record button or I hit the back button when I put the phone back in my pocket and it didn't save the video. Tested the TIT and TOT gauges post run and they both seem to be working fine. I replaced the nylon line for the P2 gauge after I noticed it was snapped from being so old and brittle. I've also had some issues with the oil pressure gauge getting stuck, but frees up after a little tickle from the backside of an adjustable wrench. I have another pressure gauge ready to be installed whenever it's not a billion degrees outside. I do have a question for the experienced folks here, could I get away with fabricating the outer liner of the combustion chamber with aluminum, since it's just air from the compressor and have the flame tube fabricated from stainless? I hate to use dissimilar metals especially in this corrosive Florida environment, but just trying to look for ways to save some weight.    |
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Post by racket on Jul 21, 2023 23:45:36 GMT -5
With your outer can , it would be possible to use ally rather than stainless , but you might/will have problems at the "hot end" :-(
If you use a stainless, air over water extinguisher , the wall thickness is only ~1 mm or a tad less , so not very heavy and you won't have problems mating it up to the hot bits .
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Post by rocketman_mike on Aug 17, 2023 17:52:23 GMT -5
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Post by racket on Aug 17, 2023 19:00:22 GMT -5
Your A/B should be OK as long as you don't add a heat shield , theres never been any problems with naked A/Bs over the last coupla decades.
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Post by rocketman_mike on Nov 5, 2023 19:19:24 GMT -5
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Post by rocketman_mike on Nov 20, 2023 19:27:28 GMT -5
Had a very successful full power run and to my amazement, the afterburner worked beautifully. I honestly had some doubt if it would work. I was also able to successfully transition from propane to diesel without any difficulty. On a side note, the boost gauge wasn't working, so Im unable to calculate any performance numbers as of this time and one of my EGT gauges decided not to play, which made me understandably nervous flying blind. Oil pressure seemed to stay around 40-45 psi the whole time, so that was a little reassuring. Most of the smoke in the video is from the turbine housing punishing the cheap thermal blanket. I have some welding to do on the oil tank and add a fitting for oil temp sensor. Going to get that oil pressure/ fuel pump kill switch wired up. www.youtube.com/watch?v=pn4k-LLZAn0 |
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Post by rocketman_mike on May 8, 2024 1:48:08 GMT -5
A little embarrassed to share this, but Im still a noob and learning as I go. I attempted a third run a couple weekends ago to test the new 15.3 GPH fuel nozzle versus the old 4.5 GPH nozzle that I had been using previously. If maths are correct, the 70mm turbo is flowing approx. 80 lbs of air / minute, so I believe that I need approx. 12 GPH fuel. While using the 4.5 GPH nozzle, I believe I wasnt getting enough fuel into the engine for the amount of air coming through the compressor. Unfortunately, I was unable to test this idea because I attempted to start the kart with an unknown amount of air pressure and I found myself in a hung start and in a panic, I killed the power instead of just killing the propane. However, when I killed the power, the RPM's began picking up and I saw the opportunity to get over the "hump" and get to a sustained idle and get the temps back down. It surprisingly worked and the engine came to idle, but in the chaos, I forgot the oil pump was still off. When I tried throttling the diesel, I quickly realized there's no throttle response and, Oh, no oil pressure either. Thats when I killed the propane and shut her down. Removed the afterburner and inspected turbine. Nothing appears damaged or cooked. Still no play in the bearings and still spins freely. After I shut it down, I ran the oil pump and left the pneumatic start keep spinning the engine to keep cool air flowing through everything. Later come to realize that in the excitement of attempting another start, I had also forgotten to open the fuel shutoff valve, so we weren't going to get any diesel anyway. So, many lessons learned in one shot. Fortunately, nothing damaged and no one hurt. I have refilled the air tank, installed a "remove before flight" tag on the fuel shutoff valve so I dont forget to open it again. Im going to recharge the battery tomorrow. Test #4 probably happen this Saturday. I do have a question about throttling. Im currently using a needle valve for controlling the fuel pressure by closing off the fuel return back to tank. Seems to work, but the needle valve takes forever to open/close. Can I just use a ball valve for quicker throttle adjustments? youtu.be/t59SQ34O2uE?si=7g6xxnLwR2gMIvpt |
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Post by racket on May 8, 2024 4:12:57 GMT -5
LOL...........don't be embarrassed , you're not alone , we've all been there at one time or another , thankfully it seems you've escaped any damage :-)
A ball valve can be used , but they can be a bit "crude" for throttling vs a needle valve, you might simply need a larger flow needle valve that only requires a couple of rotations .
Might I suggest you have your start air bottle over besides the propane to minimise time loss between starting the spoolup and opening the propane.
Also your propane usage , is it simply for a pilot light to ignite the liquid fuel , if it is then a smaller supply might be safer to prevent any damage in the event you have a similar problem.
In the past when using propane I get the propane ignited before starting the spoolup and immediately start feeding in the liquid fuel as the rpm increase on the starter , the propane isn't used as "fuel" .
Yep , make sure your starter has maximum power available to minimise spoolup time
All the best on the weekend :-)
Cheers
John
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Post by rocketman_mike on May 18, 2024 10:08:05 GMT -5
LOL...........don't be embarrassed , you're not alone , we've all been there at one time or another , thankfully it seems you've escaped any damage :-) A ball valve can be used , but they can be a bit "crude" for throttling vs a needle valve, you might simply need a larger flow needle valve that only requires a couple of rotations . Might I suggest you have your start air bottle over besides the propane to minimise time loss between starting the spoolup and opening the propane. Also your propane usage , is it simply for a pilot light to ignite the liquid fuel , if it is then a smaller supply might be safer to prevent any damage in the event you have a similar problem. In the past when using propane I get the propane ignited before starting the spoolup and immediately start feeding in the liquid fuel as the rpm increase on the starter , the propane isn't used as "fuel" . Yep , make sure your starter has maximum power available to minimise spoolup time All the best on the weekend :-) Cheers John Here's exactly what I have been doing: I crack open the air tank to get the turbo spooling up then I turn on the ignition and slowly open the propane to keep from getting too much propane built up in the engine. It usually ignites immediately and brings the engine up to a low idle. While it's running, I turn on the diesel pump and wean the engine off the propane. Right now, Im fabricating a new end cap for the combustion chamber with a new fuel nozzle setup to eliminate a pesky fuel leak Ive been plagued with from the beginning. Also fried the motor controller for the afterburner fuel pump, so Im also reconfiguring that system as well. Other than that, I had an impressive run last week. Finally starting to see some power. Managed to get her up to 30 psi in the combustion chamber before I sprung a fuel leak where the nozzle passes through the end cap. I think today, Im going to get my turbine inlet EGT probe fixed so its deeper into the stream because it hasnt been reading any temperatures going into the turbine. I believe its just catching all the bypass air. Turbine outlet temps have been much better since I've opened the afterburner nozzle. Stayed at a steady 650C. Engine obviously flows air much better and maintains steady RPM while operating the afterburner. I want to get that TIT probe fixed so I can better understand whats happening in the combustion chamber now that Im running larger fuel nozzle. Right now, I cant tell if Im getting flame impingment into the turbine. |
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Post by rocketman_mike on May 18, 2024 10:16:54 GMT -5
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Post by racket on May 18, 2024 18:04:49 GMT -5
Interesting witness marks in that bottom pic , considerable force required to bend over the melted brass fitting , appears as though theres "sideways" airflow from the positioning of the air delivery tube .
Yep , better to have "bits" isolated outside the flametube innards , far too hot inside , including your TIT thermocouple , better to only have TOT measuring for safety , with your nice long flametube theres very little chance that you'll have flames going into the turbine , if you do , they'll also be coming out of it , ...............your TIT at 30 psi P2 will be ~120 C - 200 F degs hotter than the TOT due to expansion through the turb stage , so simply add that onto your TOT to get a rough TIT.
With my A/B fuel management, I simply activate the fuel pumps and open the ball valve and deliver whatever they pump , by activating the A/B at 1 Bar P2 theres a fair amount of air flowing , probably 50% of full throttle airflow , so no problems with igniting the rich mixture , then as the power is increased things "automatically" sort themselves out :-)
Cheers
John
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