Modelling of 2 stage reciprocating compressor

Hi, is it possible to model a 2 stage reciprocating air compressor by Matlab fully without Simulink? Because I found out most of the modelling and simulation work are done using Simulink. I would like to know whether I can use Matlab fully for compressor modelling.

Answer 1

[Varun]

Hi Nai,

Looks like you want to model a 2-stage reciprocating air compressor by using only MATLAB and not Simulink.

You can use MATLAB exclusively to model a 2-stage reciprocating air compressor by coding the mathematical equations and implementing the necessary solvers in MATLAB scripts or functions.

Please consider the following example code snippet:

function compressorSimulation()

    % Parameters
    V1 = 0.01; % Volume of first stage (m^3)
    V2 = 0.005; % Volume of second stage (m^3)
    P0 = 1; % Initial pressure (atmospheric pressure)
    gamma = 1.4; % Ratio of specific heats

    % Time parameters
    tspan = 0:0.01:5; % Simulation time span

    % Initial conditions
    initialConditions = [P0, V1, P0, V2];

    % Solve ODEs
    options = odeset('RelTol', 1e-6, 'AbsTol', 1e-9);
    [t, state] = ode45(@compressorODE, tspan, initialConditions, options, gamma);

    % Plot results
    figure;
    subplot(2, 1, 1);
    plot(t, state(:, 1), 'LineWidth', 2);
    xlabel('Time');
    ylabel('Pressure (Pa)');
    title('Pressure vs Time');

    subplot(2, 1, 2);
    plot(t, state(:, 2), 'LineWidth', 2);
    hold on;
    plot(t, state(:, 4), 'LineWidth', 2);
    hold off;
    xlabel('Time');
    ylabel('Volume (m^3)');
    legend('Stage 1', 'Stage 2');
    title('Volume vs Time');

end

function dydt = compressorODE(t, y, gamma)

    % State variables
    P1 = y(1);
    V1 = y(2);
    P2 = y(3);
    V2 = y(4);

    % Compression process (simplified isentropic compression)
    dV1dt = 0; % Assume no volume change in first stage
    dP1dt = -gamma * P1 * dV1dt / V1;

    dV2dt = 0; % Assume no volume change in second stage
    dP2dt = -gamma * P2 * dV2dt / V2;

    dydt = [dP1dt; dV1dt; dP2dt; dV2dt];

end

Please note that this is a very basic model. Depending on your specific requirements, you may need to introduce additional features and refine the model accordingly. Additionally, ensure that the physical units and constants used in your model align with your system's specifications.

You can also refer to the following documentations, might be helpful for your task:

"odeset": https://www.mathworks.com/help/matlab/ref/odeset.html#namevaluepairarguments

"ode45": https://www.mathworks.com/help/matlab/ref/ode45.html

"plot": https://www.mathworks.com/help/matlab/ref/plot.html

Hope it helps.

[Ahmed]

I tried to take your code and run it, but the run icon isn't turned on to be able to run the code.

Do you know how to workin in it ?