Capability for Monopropellant Rocket Problem?

[tdhampson12]

Hey, thanks for creating this toolbox! I'm trying to use it to simulate monopropellant blowdown. Standard NASA CEA allows you to input a propellant temperature and pressure then solve the rocket problem accordingly. The associated CEA input file is attached. I have attempted to emulate it in various configurations, the closest of which is below, but unfortunately, it does not converge. Do you know if the toolbox has the capability to model non-combusting flow yet?

Thanks,

Taylor
CEAINPUT.txt

Code I tried:
`

% Initialize the mixture

import combustiontoolbox.databases.NasaDatabase
import combustiontoolbox.core.*
import combustiontoolbox.equilibrium.*
import combustiontoolbox.utils.display.*
import combustiontoolbox.rocket.*

DB = combustiontoolbox.databases.NasaDatabase;
system = ChemicalSystem(DB); % Define the chemical system
mix = Mixture(system);

mix = set(mix, {'H2'},1);
mixArray = setProperties(mix, 'temperature', Tc, 'pressure', Pc, 'areaRatio', 150);
rocketsolver = RocketSolver('problemType', 'ROCKET_IAC');
[mixArray1, mixArray2, mixArray3, mixArray4] = rocketsolver.solve(mixArray);`

[AlbertoCuadra]

Hi Taylor,

Thanks for reaching out! From your description, it seems like your configuration should work since the Combustion Toolbox equilibrium solver minimizes Gibbs free energy, making it suitable for both combusting and non-combusting cases.

What version of Combustion Toolbox are you using?

I tested a similar setup, and it converges correctly. Here’s the script I used:

% Import packages
import combustiontoolbox.databases.NasaDatabase
import combustiontoolbox.core.*
import combustiontoolbox.equilibrium.*
import combustiontoolbox.utils.display.*
import combustiontoolbox.rocket.*

% Get NasaDatabase
DB = combustiontoolbox.databases.NasaDatabase;

% Define the chemical system
system = ChemicalSystem(DB); 

% Initialize the mixture
mix = Mixture(system);
mix = set(mix, {'H2'}, 1);
mixArray = setProperties(mix, 'temperature', 3000, 'pressure', 10, 'areaRatio', 150);

% Define solver
rocketsolver = RocketSolver('problemType', 'ROCKET_IAC');

% Solve problem
[mixArray1, mixArray2, mixArray3, mixArray4] = rocketsolver.solve(mixArray);

Output

The results match NASA CEA (CEAOUTPUT.txt):

Flow Properties

Property	Inlet Chamber	Outlet Chamber	Throat	Exit
T [K]	3000.0000	2824.4487	2553.4992	300.4488
p [bar]	10.0000	10.0000	5.5642	0.0017
ρ [kg/m³]	0.0808	0.0846	0.0525	0.0001
h [kJ/kg]	44015.6051	44015.6051	37446.3765	32.8105
e [kJ/kg]	31642.1564	32201.8341	26843.7230	-1206.3857
g [kJ/kg]	-229426.1908	-213849.9663	-195682.1410	-27397.4660
s [kJ/(kg-K)]	91.1473	91.2977	91.2977	91.2977
W [g/mol]	2.0159	1.9878	2.0024	2.0159
γ [-]	1.2891	1.2236	1.2433	1.4049
Sound velocity [m/s]	3993.7646	3788.8768	3624.7130	1319.4338

Performance Parameters

Parameter	Throat	Exit
A/At [-]	1.0000	150.0000
C* [m/s]	5256.9896	5256.9896
CF [-]	0.6895	1.7841
I_vac [s]	667.8939	969.8645
I_sp [s]	369.6166	956.3916

Molar fractions

Location	Inlet Chamber	Outlet Chamber	Throat	Exit
H₂	1.0000	0.9722	0.9867	1.0000
H	-	0.0278	0.0134	-

Best,
Alberto

[tdhampson12]

Ahh I see my mistake was in my inputs coming from elsewhere; I entered it in Pascals, and it takes bar. Works now, thank you!