how to plot the motor chamber pressure and the vacuum thrust as a function of both time and web assuming quasi-steady state (equilibrium)

5 views (last 30 days)
Christina Reid
Christina Reid on 24 Jan 2021
Answered: Gaurav Garg on 23 Feb 2021
I have computed the equilibrium pressure assuming a quasi steady state condition: using the following eq attached to this question and below is my code. How do I plot Pc_eq as a function of time?
clear all
%% Step 1
% ========================================================================= %
% Basing on the motor and propellant data indicated in Table 1 and on the
% burning surface evolution shown in Figs. 5 and 6 and assuming a constant
% chambre temperature profile compute the following curves without taking
% into account the non-ideal parameters.
%% Step 1.1
%Find: The motor chamber pressure and the vaccume thrust as a
% function of both time and web assuming quasi-steady state (equilibrium)
% User inputs - First stage P80 SRM
% ========================================================================= %
mp = 88000; % Propellant Mass [kg]
ms = 7330; % Structural mass [kg]
l = 10.6; % length [m]
d = 3.0; % Diameter [m]
f = 3015; % Max thrust(vaccum) [kN]
bt = 110; % Buring time [sec]
isp = 280; % Specifi Impulse (vaccuum) [sec]
% User inputs - Propellant Ballistic Properties
% ========================================================================= %
a = 1.847e-05; % Temperature coefficient @ 300 K [m/s * Pae-0.4]
n = 0.4; % Combustion index
tau = 0.0015; % Temperature sensitivity [k^-1]
rho = 1790; % Density [kg/m^3]
% User inputs - Propellant thermochemocal properties
% ========================================================================= %
T_F = 3550; % Flame temperature [K]
M = 29; % Molecular mass [kg/kmole]
gamma = 1.13; % Specific heat ratio
% User inputs - Motor geometrical properties
% ========================================================================= %
d_throat = 0.496; % Throat diameter [m]
e = 16; % expansion ratio
v_c = 8.6; % Initial chamber volume [m^3]
v_frac = 0.85; % volumetric loading fraction (V_c/(V_c+V_p)
% constants
% ========================================================================= %
r = 8314.5 % gas constant [J/kmol)
% Calculations
% Find: The motor chamber pressure and the vaccum thrust as a
% ========================================================================= %
a_t = pi* (d_throat/2)^2; % Thrat area [m^2]
m_dot = mp/bt; % mass flow rate [kg/s]
s_b = 48; % burning surface area - pulled from the Sb vs Y plot [m^2]
cap_gamma = sqrt (gamma * (2/(gamma + 1))^((gamma+1)/(gamma-1))); % capital gamma
c_star = (1/cap_gamma)*sqrt((r*T_F)/M);
K = s_b/a_t; % Klemmung
Pc_eq = (a *rho*c_star*K)^(1/(1-n));
  3 Comments

Sign in to comment.

Answers (1)

Gaurav Garg
Gaurav Garg on 23 Feb 2021
Hi Christina,
The variable Pc_eq is a scalar value, in your case. You need to have a vector in order to plot it.
Moreover, your equation doesn't seem to have any time dependency.
So, I would suggest you to rewrite the code and give the variables you want to plot, some dependency over time and then use plot funciton.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by