Sugar/Carmel nozzle success

[JMan]

Ive had quite some trouble with nozzles in the past. For high performance motors Ive stuck to washer reenforced nozzles. Clay nozzles would never stick for me. I dont have a press so Im guessing they just couldnt grip the walls of my motor tubes enough to stay put.

 

In an attempt to make my nozzles grip the case, I tried just caramelized sugar. I melt and cast my motors. Usually I separate the grain (usually single grain cast in the case) with tape while I pack the nozzle. This time, I separated it with tape (electrical, which I thought might melt under sugar, it didnt) and pored pure sucrose over the end of the motor tube and put a smaller coring tool in there to make a nozzle (and figured with it a bit while it was cooling to make a bit of an expansion section, you may be able to see in the pictures). After it cooled, I broke it loose and pulled it out, I cracked 3 (maybe a forth) places. I thought the cracks might compromise the motor and when pressure it out on the nozzles it will shatter and fall out. I tried testing anyways because the worst that could happen is the nozzle does shatter and blow out.

 

It worked perfectly and, unfortunately, I was unable to recover the motor (as I just shot it straight up because I do not have a test stand). So I am not able to look at the erosion of the nozzle (expected to be high at first, but after seeing the motor, might be much lower than expected).

 

Planning on doing a face down test to look at the nozzle after (and maybe through) the burn. Will report what I can about the erosion, but this may not be much as it might melt AFTER it fires.

 

The motor burn for about 1-2 seconds, it was a 2 inch deep core, 5/16 inch diameter core, 3/4 inch case, 1/8 inch throat diameter.

 

EDIT: not letting me attach pictures on mobile, will try up update later.

Edited May 14, 2020 by JMan

[JMan]

 

For some reason, it is not letting me upload jpegs. The nozzle looks like it eroded in this video, but the pictures show that the erosion (while still large) is not nearly as bad as it seems in the video.

[Micahama]

Please describe what youre doing here? What are you making this nozzle out of how and add every detail possible

[JMan]

I made a sugar nozzle with a clay throat (the sugar part was the expansion section of the nozzle) it helped it build up useful pressure and could allow for a stable system of erosion and area ratio for the nozzle.

 

My reasoning for thinking this could be stable is: if the flow is over expanded, the exhaust will be much cooler, and very low pressure, if its under expanded, higher pressures and temperatures will erode the sugar section to a point where it is no longer under expanded.

 

Let me know if you guys think this could be a potential self governing system, or if Im not thinking of something.

[Micahama]

How are you making these nozzles?

[JMan]

Micahama, I believe it is quite detailed in the first post. Im currently making a thrust stand to see how well the simulations with nozzle erosion match the real tests.

 

The nozzles are made by melting sugar (no agitation to keep it dense, if you stir or mix it, it will get cloudy and, I believe, less strong). Once all melted, scoop/pour over your fuel grain (with some separator like tape or aluminium cut from a can) and stick a nozzle forming tool into it to make the proper nozzle shape.

 

For the clay, I just packed clay on top of the Fule grain then repeated the process above, and drilled out the clay after the sugar cooled and nozzle former removed.