So as the title says I am trying to write code to calculate engine size and some other parameters.
For the equations, I used mostly :
Sutton's Rocket Propulsion Elements 8th Edition, and for the starting parameters, the CEA (Chemical Equilibrium Applications) program and with some help from fellow StackExchangers, I managed to get through most of the questions.
Before I give you the procedures, here are the starting parameter, used just so it helps me get through the equations:
Fuel: 96% Ethanol (dissolved in water) - about room temperature Oxyidiser: Liquid Oxygen O/F ratio: 2 Chamber pressure: 20 Bar = 2 000 000 Pa Outside pressure: 1 Bar = 100 000 Pa(I know that's not the totally correct outside pressure) Chamber temperature: 3310.9K Molecular mass: 24.347 g/mol = 0.024347 kg/mol Gamma (ratio of specific heats): 1.1961 Characteristic chamber length L*: 2.2m (Starting/desired) thrust: 500N V1: 0.565 m3 /kg
Here are the equations that I used and the actual calculations right after it. The equations are all from the Sutton:
Ve/vt = 2.085
At/Ae = 0.274
Ae/At = 3.64
Tt = 3015.9K
Gas constant = 341,47J/kg K
Vt = 1109,7 m/s
Ve = 2.085* Vt = 2313.52 m/s
mdot = F/c = 0.216 kg/s
m dot ox = 0.144 kg/s
m dot f = 0.072 kg/s
At = 0.0001772 m2
Ae = At * 3.643(calculated above) = 0.0006455 m2
c* = 1640.64m/s
Isp = 235.9s
Vc = 0.000389 m3
ts = 0.00319s
these are all the equations I got. Now for the last part, the length and diameter of the chamber. I know that the diameter should be 3 to 5 times the diameter of the throat.
So I put 2*, 3*, 4*, and 5* diameters of the throat for the chamber diameter, and the 3* was the best.
I concluded that the 4* option looked good so i chose:
Dc = 6 cm
Lc = 11 cm
There were 5 options but the aspect ratios were a bit weirder.
I know this is just the first part of the process of designing a rocket engine but I just want to be sure before I go any further with it. So if you took/take the time, thank you. Also, I apologize for bad formating, still learning that too. Any tips (for the rocket and formating) are always welcome!
Subscript e or 2 is for nozzle exit
Subscript 1 or c is for chamber
Subscript t is for throat