New build, not 1:30 anymore...

[cnctech]

I WOULD NEVER RECOMMEND TELLING YOUR WIFE THAT IT MY MONEY AND ECT . BECAUSE A POORLY EQUIP. SHOP IS NOT A GOOD PLACE TO SLEEP

[stoffe64]

Hahaha,i know this feeling,My wife got freakin mad when i bought My Garrett TV 61 turbo for My build,and Ever since then she gets very upset as soon as i want to get ANYTHING for My engine build,she dont understand this hobby and it is not allowed to cost anything almost,very frustrating!

[wolfdragon]

So I ignored all of your suggestions on how to sneak buying tools around my wife and went back to the garage... where I belong...?

Yesterday, I put the Transition on the back of the Flametube so I could start making the ducting to the turbine inlet. And when I was done, I did a fire test and was not happy, way too hot and a couple feet worth of blue streaming out the end...



So after a bit of watching how the flame formed, I figured out the problem was most likely where the fuel was being injected as that was the widest diameter of the burn. It was about 10pm so I planned on fixing the burn problem would be best for the next day.

So this:


Now looks like this (except there are welds holding the fittings to the tube:


And the resulting flame pattern is:


Now there aren't streams of blue flames coming out the end of the transition housing, just licks of yellow/orange with a hint of blue when the fuel is running very high. Thermocouple in the exhaust stream read a controllable 850 degrees F at the lowest, if I had a better needle valve I could have gotten it lower, and to 1400 degrees F before I decided to stop opening the needle valve (which wasn't but a maybe a turn away from the 850 mark...)

Important lesson, the sintered portion of that pneumatic muffler that is my fuel injector, those are glued in place. Yeah, that glue doesn't stand up to the flame temperatures inside the combustor, so after that let go and it came out the ass end of the flametube, I got my "hot run".

After the initial cough of fire, the burn settled back down but into super high gear. Since nothing seemed to care all that much I let it continue, figuring this would be a valid test point. Once the transition housing cone turned red from the heat, I figured that was enough of a murder run to see if I buckled the flametube, and cut the fuel and let everything cool off. Looked inside and the flametube had more bluing from the additional heat but nothing had moved, score one for not insanely thin stainless.

All in all a very good day.

Next step, start adding ports for my thermocouple probes and pressure pickups.

[stoffe64]

this will be interesting to follow,i always loved mad scientists...well you sort of has to be when youre into this hobby ;D

[wolfdragon]

Installed my T2 and P2 pickups, will post pics later.

T2 is via a 1/8" compression fitting with a guide tube (6" thermocouple probe)
P2 is via a 1/4" flare fitting with a tube extension to point the pickup directly into the intake line, should read total pressure instead of a dynamic pressure that a side based port would have.

Next up is the ducting to get the combustor to the turbo inlet.

[stoffe64]

Dont you get the same pressure reading over the Whole
combustor? I dont think you get different pressures,maybe the needle
Can be jumping if you dont place the pickup point where it is reasonable
Qiet and stable pressure!

[racket]

Hi Wolf

Sidewall port gives static pressure , dynamic pressure is the difference between static and total pressure that the pitot tube will read .

Cheers
John

[wolfdragon]

Doh! That's right, it was too late last night for good posts lol

So do I want static pressure or total pressure? Placing pickups is easy right now...

IIRC most all the thermodynamics homework I did wanted total pressure to make math easy.

[racket]

Hi Wolf

Yeh , total absolutes for the calcs , a static wall port in the combustor where the airflow is at its slowest will give you a reasonable figure to work with , total pressure pitots will have their own inaccuracies which could be just as inaccurate as the static port ,
Cheers
John

[wolfdragon]

Sure is hot here in south Maryland lately... makes it hard to work up the courage to go welding... 100+F heat index out there right now

[wolfdragon]

Well I finally got back to the garage, installed the electronic ignition and did a few test burns

I don't think the neighbors appreciated the loud bangs of hard ignitions (I got it to nice little pops after I figured out what the hell I was doing) but I was able to get about 3 pounds of propane through the combustor before the bottle ran low.

Interesting thing to note:
After I have the flame going good and strong, there is a point (around 1100 degrees F) where the flame sucks all the way back into the combustor and even though I am opening the fuel valve more and more, and the fire is sounding angrier and angrier, the temperature doesn't really rise as quickly as it did at lower fuel levels.

Now I know that at lower fuel levels, with actual flames hitting the probe, things can get really hot really fast (at just barely enough fuel to keep a stable flame, I had over 1500F at the probe), but is this nonlinear temperature rise (it would seem to be a decaying exponential but I need more data for the math) with more fuel consumption correct? I was able to repeat the trends 3 or 4 times so I don't think it's an instrumentation issue.

It was just really odd to not have a big temperature spike as I kept opening the valve and yet the sound got louder and angrier and I had to stand farther and farther back to look inside the combustor to see how the swirl pattern was (which was really cool and the camera would not get a good picture of it, it just kept looking through the fire instead of at it).

Also, inspection after the runs showed carbon film buildup from the face of the flametube to the beginning of the primary zone, heating effects can be seen from there to roughly 2/3 the way tot eh secondary zone, the rest of the tube has no heat affected zones other than at the welds. Transition colors from the primary zone are light straw fading to a yellow and then to typical stainless silver.

I will get the propane bottle refilled before I try again and see if I can repeat the results with a fresh bottle.

nuggets of wisdom would be most appreciated

pictures and more youtube videos will follow the next bit of testing

[wolfdragon]

Was 102 deg F outside today, weatherman says heat index of 115

I don't know what a heat index is, all I know was it was damn hot, and the combustor wasn't making that garage any cooler...

Figured out the funny issue I saw with my temperatures, had a bit of trash in the fuel line, not sure how it got there but when I removed it, everything was happy again.

Instrumented test firing of the combustor with the transition cone installed. Thermocouple is 6" back and dead center of the opening. I did it once in F and once in C just to burn more fuel.





After that was done, I was curious to see how the flamtube was holding up. Points of reference, the tacked seam is on the bottom of the tube, fuel injection is on the top at the face. The bluing is only present in that one location, looks like that's where the hotspot for the burning swirl is. The face of the flametube all the way to the end of the primary zone has a fine layer of soot on it.

[racket]

Hi Wolf

You really shouldn't have that "tail" of yellow flame exiting the combustor at such "low??" temperatures ......................what are you using for a fuel injector ??

It appears as though the air swirl is so great, and with the fuel centred in the middle of the "vortex" its not mixing and burning correctly .

From the appearance of your gases exiting the combustor it looks like a bit more development required before its installed on a turbo otherwise you'll have flames exiting it

Cheers
John

[ernie wrenn]

The sharp edges of the rectangle pipe will cause a tremendous trubulance due to the pressure scrub (friction) of the low pressure air on the sides draging against the main flow area. (also adds distubulace to the swirl pattern). The is a reason that straws are round.

A round pipe has a far greater flow due to this auction, by reducing low pressure areas.

ernie

[wolfdragon]

I am also going to have about 2 feet of rectangular ducting from the end of the transition cone to where the turbine flange is, it will also have a swept 90 degree turn. My hope (and I will do another fire test to see if it actually does it) is that the length combined with the turn in that turbulent ducting will help knock out that tail so I do not have fire impingement on the turbine.

John, the injector is a pneumatic muffler positioned at the top of the flametube instead of near the center, the pictures of the flames produced by both positions are on the 3rd post of page 4. The flow pattern is a 90 degree cone pointed directly at the top of the inside face of the flametube, this of course is skewed by the local airflow and is distributed along that surface where it hits the primary zone mixes and burns, at least that is what the soot is telling me.

If I could figure out how to get the camera to see the flame instead of looking through it (not really sure how it is doing that) you would be able to see that the flame tail has a parabolic shape from where it separates from the wall of the primary zone, thus why more fuel and it grows at a steady shape.

Aside from adding a diffuser cone to the center of the flametube somewhere in the secondary to tertiary zone like you would see in an AB, I'm not sure what I can put in there to get in the way of that tail to keep it from coming out the back, thus the hope for the turbulent ducting and the turn. I know that will further exacerbate the need to insulate that ducting to minimize losses due to the heat exchange.

If that doesn't work I will probably cut off the current transition cone, make a new one that transitions to a small round tube instead of a rectangular duct, and probably add that small cone in the flametube to force the flame closer to the tertiary zone holes to cool it off.