Thanks for the tip Rick. I will test nozzle-down for my first tests.
On Mon, Sep 11, 2017 at 3:26 AM, Rick Maschek <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
Testing nozzle up results in slag build up on the bulkhead.
Testing horizontally results in slag predominantly on the underside of the
motor.
Testing with nozzle down (flight orientation) results more slag on/out the
nozzle.
The pressure and temperature your nozzle gets also determines how much
slag accumulates. Lower pressure/temperature or regressive motors tend to
have a greater accumulation on the nozzle from my experience.
On Sunday, September 10, 2017 3:59 PM, Mike Smith <smittypwr@xxxxxxxxx>
wrote:
My formula has more sucrose than dextrose. And since I use Jimmy Yawn's
method of moldable fuel I use more oxidizer, 66%. Both result in a hotter
burning fuel (I am told). Perhaps I will go back to using a convergent
section if my steel washer shows no build-up of slag. It makes sense that
stagnant flow and cooling gases would result in more liquid potassium
carbonate. So i need to keep it hot and flowing.Thanks for your research.
On Sun, Sep 10, 2017 at 3:40 PM, Steve Peterson <
dmarc-noreply@xxxxxxxxxxxxx> wrote:
Below is some output from propep for dextrose. There's a lot of stuff
there, but the last item is the potassium carbonate (as a liquid). It's
always going to be there. Whether it's an issue or not depends, I'm sure,
on the situation. (Sorry about the column alignment).
The melting point for K2CO3 is 891C, and propep says that at 1000 psi,
combustion temperature is 1700K which is about 1427C. The question would
be, I guess, is whether the chamber gas flow is such that there could exist
stagnant areas where the stuff could cool a few hundred degrees.
With a throat of only, say, 0.125" diameter in a 2" diameter chamber,
especially with no, or very little converging section, I would think
there'd be some opportunity for stagnant flow. Anyone care to take a stab
at it with FEA? Ben?
--Steve
==============================
Frozen equilibrium performance evaluation
Propellant composition
Code Name mol Mass (g) Composition
765 POTASSIUM NITRATE 0.6429 65.0000 1N 3O 1K
908 DEXTROSE (GLUCOSE) 0.1943 35.0000 6C 12H 6O
Density : 1.890 g/cm^3
5 different elements
N O K C H
Total mass: 100.000000 g
Enthalpy : -5650.92 kJ/kg
161 possible gazeous species
31 possible condensed species
CHAMBER THROAT EXIT
Pressure (atm) : 68.046 39.324 1.000
Temperature (K) : 1710.675 1604.776 1030.474
H (kJ/kg) : -5650.924 -5829.118 -6764.750
U (kJ/kg) : -5986.372 -6143.801 -6966.817
G (kJ/kg) : -17506.126 -16777.869 -13906.070
S (kJ/(kg)(K) : 6.930 6.823 6.930
M (g/mol) : 42.401 42.401 42.401
(dLnV/dLnP)t : -1.00000 -1.00000 -1.00000
(dLnV/dLnT)p : 1.00000 1.00000 1.00000
Cp (kJ/(kg)(K)) : 1.68952 1.67563 1.57522
Cv (kJ/(kg)(K)) : 1.49342 1.47954 1.37913
Cp/Cv : 1.13130 1.13253 1.14219
Gamma : 1.13130 1.13253 1.14219
Vson (m/s) : 613.50422 596.98305 478.12015
Ae/At : 1.00000 10.09999
A/dotm (m/s/atm) : 13.40451 135.38532
C* (m/s) : 912.12249 912.12249
Cf : 0.65450 1.63633
Ivac (m/s) : 1124.10413 1627.91710
Isp (m/s) : 596.98305 1492.53178
Isp/g (s) : 60.87533 152.19589
Molar fractions
CH4 1.6769e-06 1.6769e-06 1.6769e-06
CO 1.6786e-01 1.6786e-01 1.6786e-01
CO2 1.5403e-01 1.5403e-01 1.5403e-01
COOH 3.1649e-08 3.1649e-08 3.1649e-08
H 5.9406e-06 5.9406e-06 5.9406e-06
HCN 8.1592e-07 8.1592e-07 8.1592e-07
HCO 5.8867e-08 5.8867e-08 5.8867e-08
HNC 2.4975e-08 2.4975e-08 2.4975e-08
HNCO 8.5490e-07 8.5490e-07 8.5490e-07
H2 1.0350e-01 1.0350e-01 1.0350e-01
HCHO,formaldehy 5.7919e-07 5.7919e-07 5.7919e-07
HCOOH 1.8971e-06 1.8971e-06 1.8971e-06
H2O 3.2862e-01 3.2862e-01 3.2862e-01
K 3.2581e-04 3.2581e-04 3.2581e-04
KCN 1.6907e-06 1.6907e-06 1.6907e-06
KH 2.7062e-06 2.7062e-06 2.7062e-06
KOH 9.2741e-03 9.2741e-03 9.2741e-03
K2 4.8160e-08 4.8160e-08 4.8160e-08
K2CO3 1.2476e-05 1.2476e-05 1.2476e-05
K2O2H2 4.2618e-04 4.2618e-04 4.2618e-04
NH3 3.2204e-05 3.2204e-05 3.2204e-05
NO 2.0784e-08 2.0784e-08 2.0784e-08
N2 1.2056e-01 1.2056e-01 1.2056e-01
OH 9.9992e-07 9.9992e-07 9.9992e-07
Condensed species
K2CO3(L) 1.1534e-01 1.1534e-01 1.1534e-01
