slittlewing
Senior Member
Joined: November 2017
Posts: 458
|
Post by slittlewing on Aug 20, 2020 14:32:07 GMT -5
It is relatively easy to use a relay, resistor and capacitor to make a pulsing module which grounds the coil at a frequency (defined by the resistor and capacitor) in order to generate a pulsed supply to the coil. I used this in my “jet sledge” with a Bosch cool. Alternatively you could use a 555 timer chip and transistor and relay. However, the small “spark generator” units are cheaper, easier to wire (just a dc input) and lighter, which is why I switched to them instead.
Cheers
Scott
|
|
ausjet
Veteran Member
Joined: May 2013
Posts: 133
|
Post by ausjet on Aug 20, 2020 21:46:14 GMT -5
I made an ignition system exactly the same as in Johns YouTube link. Simple off the shelf parts and worked very well with my engine. (Which was very similar to yours) I opened up the gap on the spark plug to as big as I could go, it lit the propane easily every time.
|
|
|
Post by sauerkraut on Aug 21, 2020 14:29:42 GMT -5
Tried the 80kV spark generator earlier this morning. I still had the compressor disconnected from the combustion chamber, I just blew air straight into the combustion chamber.
It lit fairly reliably. The spark generator gets very hot very fast so I dont know how long it'll last but it'll do for now.
I also added a needle valve last night for more fine gas control without having to use the valve on the tank. I was able to get my EGT above 400°C without tripping the OPD for the first time. I discovered an air leak where the flame tube bolts onto the housing.
I've hooked the compressor back up, and I'm going to throw some liquid gasket around the aforementioned leak. Once that's set up I think the engine might finally be ready for its first startup.
|
|
|
Post by sauerkraut on Aug 22, 2020 14:30:48 GMT -5
I had time for a test this morning. I am really fighting the OPD... I managed to get some not-so-good video while attempting to get it to idle. I'm right on the cusp, but I keep tripping the OPD. When the blower is removed it starts spooling down. That being said, I'm surprised it lasts as long as it does considering it only ever gets to about 2 psi P2. youtu.be/Ercl4h5IRXk
|
|
|
Post by turboron on Aug 22, 2020 15:51:57 GMT -5
sauerkraut, you might try a different BBQ tank as the one you have seems to be especially restrictive. Also, you can tee two tanks together to get a higher flow. Two tanks also helps with gas generation from the liquid since it is based on wetted area.
Thanks, Ron
|
|
|
Post by racket on Aug 22, 2020 17:07:16 GMT -5
Might be time to think about spraying some kero/diesel in to augment the propane
|
|
|
Post by sauerkraut on Aug 22, 2020 17:44:14 GMT -5
Buying parts for that now.
I got a 60-70 degree adjustable nozzle threaded at 1/8 npt, so it'll just fit right into the hole for my propane orifice.
I'll shift the propane orifice over and use it as a starter.
|
|
|
Post by sauerkraut on Aug 26, 2020 12:47:23 GMT -5
Took the flame tube out in preparation for Kerosene, the two nozzles with different orifice sizes should be here tomorrow. The carbon deposits from the test run in the video denote that it is burning hotter on the side where the air is coming in. I feel like its reasonable to conclude that my air inlet is too close to the primary holes, but too late to change that now. The good news is that the carbon deposits end after the secondary holes, which I take to mean that the mixture is no longer fuel rich past the secondary holes and that my hole areas are correct. One quick question - I've seen people mention that they use a mixture of Kerosene and gasoline (like JP-4) to get a little more volatile & easily burning fuel. Is this a "bad" practice?
|
|
|
Post by racket on Aug 26, 2020 17:05:02 GMT -5
No need for a kero/gasoline mix in your engine , I use it because my flametube is at its limits being only ~70 mm long , the time frame for combustion simply isn't long enough for "normal" kero or diesel , you have several times more dwell time in the combustor, stick with straight fuels , gasoline isn't a "good" fuel , kero is best
|
|
|
Post by sauerkraut on Aug 31, 2020 19:47:37 GMT -5
Update:
It Lives!
Good news: It runs great. Warmed things up on propane for a minute or so, then turned the fuel pump on and she comes to life. I then turned the gas off, and she idles well at 5 psi on pure kerosene. I tested it up to 20 psi with no surging, and EGT never passed 400C at any point. Bad news: Kerosene leak where the nozzle is screwed in to the fuel supply, so I had to cut my test short. Also, the oil seal on the turbine (and possibly the compressor as well, I'd have to take it apart to see that though) appears to be blown. The insignificant side to side play has doubled in magnitude, and there is now forward and back play. Not enough to see any movement, but enough to feel it when you push back and forth. In summary, turbo might be trashed.
At some point, a light amount of smoke started coming from the exhaust and that familiar smell (burning oil) became apparent. I could see a pattern of liquid that had slowly been spraying onto the plate holding my EGT probe. Once I killed the fuel supply the engine turned into a smoke generator, no matter how long I ran the blower the smoke kept coming. Just to make sure it wasn't residual Kerosene, I lit and ran propane for about 10 seconds but the smoke just kept coming. I shut off the blower and let the oil pump keep running to prevent coking. At this point I noticed liquid on the turbine blades and pooling on the bottom of the turbine housing. There were also streaks of coked oil on the turbine blades. After a few minutes of the oil pump running I fired up the blower one more time and oil just spewed out of the thing, there was a good tablespoon or 2 of oil that had collected in that time.
I started it with the oil pressure at 30 psi. Once it was up to idle, I kicked the oil pressure up to 50 psi before running it up. Once I shut off the fuel, I turned it back to 30 psi, and once I shut off the blower, I turned it down to 20 psi.
I either wasn't giving it enough oil pressure, or I was giving it too much oil pressure, or my 4AN oil feed needs to be 6AN, or this turbo can't handle 20 psi @ 375C. I'm pretty sure it isn't the oil drain - the flange is 1/2 NPT female, and I have a 1/2 NPT to AN10 adapter to connect to the drain line. The oil also drains above the oil level in the tank. If the drain was the problem the leak should have subsided once the pressure was turned back down.
EDIT: I'm using 0w20 oil, and I just read on a TurboofAmerica article that oil thinner than 10w30 can leak even when the seals are still good, and that oil which is too thin can cause premature wear. I'm using thinner oil because I'm using a 12V inline fuel pump, and I wanted to shy away from thicker oil because the pump wasn't designed for it. Does this have any merit to it? I suppose that tomorrow I can run the oil pump with cold oil and see if the seal leak continues. I'll also try removing the return line to make sure oil is still draining properly.
EDIT 2: Is is possible that a lack of ventilation of the oil tank has caused enough pressure inside the drain line to restrict flow? Again, I'm pretty sure the problem isn't with the oil return, as the problem would have presented itself earlier and would have stopped once I reduced the oil pressure. I just want to make sure that all of my bases are covered
|
|
|
Post by racket on Sept 1, 2020 2:23:21 GMT -5
The oil tank needs to be well ventilated as theres always some air/gases bypassing the seals even with a new turbo
0W20 when cold should be OK .
|
|
|
Post by sauerkraut on Sept 1, 2020 18:13:02 GMT -5
The implication being that it isn't okay when hot?
I'm definitely going to switch to heavier oil. From what I've been reading 0w20 isn't thick enough to prevent excessive wear.
I'm probably going to switch to 10w30. I dont like the idea of going even thicker than that because of bearing friction reasons.
Also, I took the flame tube out... wow did all that oil just sitting there burning do a number on stuff. The metal is... pretty ugly even after I got all of the carbon removed. It was a huge mess too, lots of oil just sitting in the bottom of the flame tube.
I'm hopeful that its just an issue with the oil drain... but the fact that this didnt happen on the first failed startup has me very concerned about the turbo itself. If it happened now it should have happened then too.
|
|
|
Post by racket on Sept 2, 2020 0:23:50 GMT -5
Hi
You oil system needs an overhaul .
Firstly , you are measuring oil pressure at the pump outlet rather than at the turbo oil inlet fitting , an unsuitable pressure line could mean minimal pressure getting to the turbo bearings .
Secondly the oil tank volume , the tank needs to hold at least 3 litres of oil even for a modest sized turbo and there must be a large "expansion volume" above static oil level , so the oil must only fill maybe 2/3rd of the tank.
Thirdly the ID of the drain tube from the turbo must be at least the diameter of the drain hole in the turbo centre housing casting , the oil coming out of a turbo is heavily aerated and frothy .
Fourthly, the oil drain needs to dump in above the running oil level which will be much higher than static level.
And finally the tank venting needs to be at least 1/4" ID , lotsa gas comes out of it .
I tried using a fuel pump for oil and it wasn't satisfactory even with a ball bearing arrangement, remove the oil line at the turbo and place the outlet in a container and turn on the oil pump and measure the flow
Cheers John
|
|
|
Post by turboron on Sept 2, 2020 5:11:16 GMT -5
John, the 1/4" vent suggestion surprises me. It is much lower than I expected. My tank is not sealed I just have a clear cover over it with view of the oil drains. The cover leaves a lot of open area for venting. Have you ever check the pressure in the tank while at maximum power? What type of plume do you see at the vent exit.
Thanks, Ron
|
|
|
Post by sauerkraut on Sept 2, 2020 11:14:33 GMT -5
I can move my pressure tap easily enough.
The oil tank has a capacity of about 5 US Qts, or 4.7 L. I initially filled it with 2.5 Qts of oil, although I've lost what seems to be about .5 Qts from the leak.
As for the oil drain, what I can do is drill out the NPT to AN adapter, but I've pretty much blown my budget and then some so I'm going to have to stick to 10AN line.
The oil drain dumps at the very top of the tank, well above the oil level.
My tank venting is clearly not sufficient, for now I'll just remove the oil fill cap and put a mesh over it.
As for the pump and oil flow rate, the pump is definitely not the limiting factor. Advertised flow rate is 45 GPH and I'm sure it can do it too, just not thru a 4AN line. I'll measure the flow rate.
EDIT: After I make the aforementioned changes, what I'll do for the next test is remove the oil drain line, and just let the oil drain into a funnel that is stuck into the oil fill port. That's how I initially tested the oil system to ensure proper flow. If there are no problems running like this, but they appear again after I re-attach the drain line, then I guess my hand is forced.
|
|