Dave,
Glad to hear about your interest in the science of rocket propellants.
Good question you asked, straightforward answer.
H3, KCN, CHF, CH2O, etc were left out of the calculation because these are
present in such tiny quanities. If one took the extra effort to include
these, you'd find that the final values for isentropic exponent, etc, would
be unchanged. Good exercise to try perhaps :-)
Richard
<http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail>
Virus-free.
www.avg.com
<http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
On Sat, Mar 3, 2018 at 1:52 PM, David Snyder <dvdsnyd@xxxxxxxxx> wrote:
Hi Everyone,
I've been lurking for a while. There have been some very interesting
discussions so far. A little background on me - I have worked on Sugar
based propellants in the past, mostly KN-Sorbital, and KN-Erythritol. My
father and I have successfully flown a J powered KNER rocket to over a mile
at our peak in sugar propellant. Our success wouldn't have been possible
without help derived from sites by Jimmy Yawn, Richard Nakka and Scott
Fintel. Thank you!
Now, We are looking at getting into composite propellant, but I am trying
to learn more about Guipep and the science behind propellant development
and formulation. For this, I am going back to sugar, since so much of the
theoretical side is documented by Nakka. I am trying to replicate some of
the theoretical calculations he has done.
So, I began going through the technical notepads on Nakka's site.
Specifically the KNSU notepad:
http://www.nakka-rocketry.net/techs.html
I understand the math behind most of it, and was able to very closely
replicate the numbers he came up with, but I am having trouble identifying
why certain combustion products were left out in some of the calculations.
Specifically in note 2:
Nearly all of the combustion products from the Guipep run are listed in
the first table where the total moles, gas moles and condensed moles are
calculated.
However, I'm unsure of why some of the products are left out, notably
I'm unsure of why NH3, KCN, CHF, CH2O, and CNH were left out, but OH was
left in.
OH has a smaller mole fraction than NH3 and others as far as I can tell
when evaluating the complete list in excel.
Again, in the second table where the isentropic exponent for 2 phase flow
and others is calculated, I'm unsure of how the final list is derived.
Further combustion products are left out in this list. Such as OH, KH, H, K
and others.
Guipep also provides an exhaust products results. However, one of the
underlying assumptions is that chemical equilibrium is established in the
combustion chamber, and does not shift through the nozzle. Although, upon
inspection. The products in these results to not follow with that of the
table used to calculate the isentropic exponent either.
I can only assume that there is a reason for these decisions, but don't
have enough hand's on/gut-check style of knowledge to figure out why yet.
Before asking about some other questions I have, I'd like to gain some
insight on this if possible Would anyone be able to help shed some light on
why various combustion products were left out in each of the calculations?
Thank you for all of your help,
Dave
