I could not open the cad files, could you save as r12?
On looking at the jpeg it seems that there is nothing holding the plug
in place, is this a sectional drawing? Pretty curves though. Will TC
calculate area?
David Masten wrote:
> I received the TurboCAD stuff Friday (actually, I got it Saturday, but
> it was delivered Friday :)). So I installed a copy, and started trying
> it out. If you want a copy let me know, it is pretty good stuff.
>
> Of course the best way to try out a CAD tool is to design something
> useful with it. The something useful I tried was an aerospike engine:
>
> http://lucifer.piratelabs.org/Rockets/spikelist.jpg
> http://lucifer.piratelabs.org/Rockets/spikelist.TCW
> http://lucifer.piratelabs.org/Rockets/spikelist.dxf
>
> I have run into a few difficulties and learned quite a bit:
>
> 1. The actual location and size of the throat is not obvious. Twice I
> dimensioned the spot where I thought the throat was to later find out
> that there was a smaller area downstream of it. (The first time was just
> a boneheaded DOH!, the second time was a subtle trick of conical
> geometry.)
>
> 2. The throat dimension is going to be real tough to get right on the
> scale we are working at. .020 inches is a ~400N thrust difference.
>
> 3. It looks like (from what little I have found) the "ramp" geometry is
> fairly important to getting good performance and the proper flow fields.
> The ramp on my drawing is pretty much wrong, I think. A NASA-AIAA paper
> that I found uses a flow 28-34 deg off the center axis at the throat and
> a cubic spline curve for the ramp.
>
> 4. WOW!!! something is wrong with my calcs. I get theoretical numbers
> from 3700N thrust and 132 Isp at 500m elavation (our test stand) up to
> vacuum 5000N and 180 ISP. Okay, so vacuum performance is unattainable
> even for an aerospike, but I am questioning my thermodynamic analysis -
> does this seem reasonable for theoretical numbers at 300psi chamber
> pressure and 85% HTP??
>
> 5. I really need to do some CFD on this. Does anyone know of a good
> grid/mesh generation software package that is low-cost and easy to
> obtain? I have some CFD code that should do exactly what I need
> (AllSPD-3D from NASA Lewis) but generating a grid by hand is more tedium
> than I can bear.
>
> Dave
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