Henry,
From my understanding there is a general equation used for estimating
residence time (NASA SP-8064 page 20) with the utilisation of L* seen as an
alternative method (page 66).
https://ntrs.nasa.gov/search.jsp?R=19720006088
Cheers,
Troy
-----Original Message-----
From: arocket-bounce@xxxxxxxxxxxxx [mailto:arocket-bounce@xxxxxxxxxxxxx] On
Behalf Of Henry Vanderbilt
Sent: Tuesday, 10 April 2018 4:38 AM
To: arocket@xxxxxxxxxxxxx
Subject: [AR] Solid Motor Length & Volume (Was Re: Aluminium vs
Magnalium)
This came up earlier, with several mentioning motor length as determining how
high a metal particle fraction could usefully be included in an APCP solid
motor.
My thought then was that ratio of chamber volume to throat area should be
the main thing determining combustion dwell time of a particle within a solid
motor, analogous to liquid motor L* determining how much time liquid fuel
droplets have to combust.
You mention both volume and length as factors. Should I understand then that
solid motor length is also a factor, even beyond the strict matter of how much
it contributes to available combustion volume? IE, that a long skinny solid
motor would combust metal particles more completely than a short fat one of
identical internal volume?
And, out of curiosity, do solid motor designers even use L* as a design
parameter? Or some equivalent, or partial equivalent?
Thanks for the very informative discussion of metal particles, BTW.
Henry
On 4/9/2018 6:36 AM, Jim Rosson wrote:
Note-When using high levels of any metal, be aware that a motor needs
sufficient chamber volume and length to allow complete reaction of
metal powder into reacted molecules. Failure to have large enough
space, will result in metal slag collecting on nozzle and/or burning
in plume (creating lower combustion efficiency than expected).