Window in combustion chamber?

[Fricke]

JW -

Remeber to use a glass that can withstand a pressure of at leat 3 times the highest possible boost pressure... To be shure that the glass don´t blowup in Your face... And it should withstand the pressure at a temperature 3 times the max temp the CC and readiated heat from the flametub will be...

Just a reminder PLAY SAFE! - picking glass pieces from your face is not fun... And the risk of losing an eye...

//Fredrik

[JW]

Yeah I know, safety comes first!
I have designed a method to mount the window is such a way that it can be a plate, and doesn't needs to be bended around the cc.
My design also can be used to have 2 layers, with one layer free to expand.

A safety factor of 3 is indeed a must in this case!

[RG Rhodes]

Howdy all-

I wonder if something along the lines of a pin-hole camera could give
us a view of the interior of a running engine.

I cut bottom off an empty beer can, and poked a hole in the side with
a pin at half-height. I then placed this over a candle, and holding a
piece of mylar drafting film before the hole I saw a pretty clear image
of the flame. In view of the utter crudeness of the set-up, the
resolution was suprisingly good. Next, I cut a piece of masking tape
the length of the can and marked six heavy X marks along its length.
This I stuck vertically on the inner wall of the can opposite the
pin-hole. The can was then placed back over the candle, and viewed
with the mylar. I could clearly see the flame, and could sort-of make
out the tape, but could not see the X's. Next, I removed the can and
fitted the open end over my flashlight, and again viewed with the
mylar. this time I could clearly see four of the six X's

I dunno if something like this could be made to work or not.
Justa thought.

RG

[Tom]

The thing about webcams is that they are amazingly sensetive to IR radiation. Just think about all the digital camera photos of engines running on this forum. Most of them have little statements with them, to the tune of "appears hotter then it actually is". You'd have a hell of a time trying to work with that.

On a tangent, what about fibre optics? Does anyone know of any fibres that are heat resistant enough?

Tom

[pezman]

If you:

- place a window on each side of the CC and ..
- spray paint "random" dots using high-temp paint on one of the windows and ...
- Put a strobe behind the painted window and ...
- Photograph the dots (through the unpainted glass, through the CC, focusing on the dots on the painted window). Use a very small aperture, rear-lighting the "dotted" window with a fast strobe
- Photograph the same scene while the engine is running ...

Then you can use DigiFlow to easily generate a Synthetic Schlieren image of the PJ while running. You can even take a movie of the scene and use the software to generate a sequence of Schlieren images.

It's easy, it's free.

[RG Rhodes]

G'morning all-

I believe saphire has been used for windows in high-temp burners.
Saphire has very good thermal conductivity and can be cooled with
with forced draft. This might make a good window for a turbojet
burner can. An outfit named Melles Griot makes them.

RG

[longjohn]

You dont need tempered glass. Just thick glass. You mount it in the end, so some of the air from outside the flame tube, flows across the glass. Use glass at least 10mm thick........and you will have success like this...

My jet scooter CC chamber site glass window vid..

http://sancho.ips-mesh.net/Jetscoot/Fou ... hamber.avi

[longjohn]

oh and I found a outside piccy of it, (pic is taken sideways, but its on the left, you will get the idea) I thought id better post this picture, since the video doesnt show the site glass window itself very well.

cheers

http://sancho.ips-mesh.net/Jetscoot/Fou ... 0_0829.jpg

[Rossco]

Hey Longjohn,
Is that Ipswich, Brisbane, Australia?
Were getting quite a team up!

Rossco

[bob000555]

aerogel might work, its hard to get in big chunks try a milatery surplus store
http://www.unitednuclear.com/aerogel.htm

[larry cottrill]

Interesting idea, RG. I wonder how much flame would be visible, and how much would just be the wall glowing. There's also the issue of the escaping gas melting your viewing screen.

Of course, I don't pretend to know anything about turbos, but what Ben says here is important to consider. We have often looked into pulsejets, and what you see is the radiant red hot color of the steel wall MODIFIED by its passage through the blue flame. While interesting (and often quite beautiful), this is very difficult to sort out, although it is true that considerable flame detail is clearly visible. Of course, we're viewing it from the tail end where you're looking through half a meter of flame! It would be nice to do a spectral analysis of such a flame running, but I think that would be impossible with the glowing steel in the background, which puts out so much visible light it totally predominates.

On the other hand, if your turbo chamber is well designed and properly aspirated so that your flame tube is working properly, shouldn't the tube itself be (relatively) cool? If it stays dark (in terms of visible light), then you should see the characteristics of the flame very easily. A lot will depend on exactly how you locate your window, of course.

L Cottrill