2 vues (au cours des 30 derniers jours)
le 22 Août 2023
I want to add a make-up port to the controllable mass flow element, but when I run it he gets the error: Cannot find parameter 'area_C'.And I want to be based on adjusting the position of interface C, what should I do.
component controlled_mass_flow_source
% Controlled Mass Flow Rate Source (2P)
% This block represents an ideal mechanical energy source in a two-phase
% fluid network that can maintain a controlled mass flow rate regardless of
% the pressure differential. There is no flow resistance and no heat
% exchange with the environment. The mass flow rate is set by the physical
% signal port M [kg/s]. A positive value causes fluid to flow from port A
% to port B.
% Copyright 2013-2021 The MathWorks, Inc.
nodes
A = foundation.two_phase_fluid.two_phase_fluid; % A:left
B = foundation.two_phase_fluid.two_phase_fluid; % B:right
C = foundation.two_phase_fluid.two_phase_fluid; %
end
inputs
% Mass flow rate
M = {0, 'kg/s'}; % M:left
end
parameters
power_spec = foundation.enum.power_spec.isentropic; % Power added
% 1 - isentropic
% 0 - none
area_A = {0.01, 'm^2'}; % Cross-sectional area at port A
area_B = {0.01, 'm^2'}; % Cross-sectional area at port B
area_C = {0.01, 'm^2'}; % Cross-sectional area at port C
end
% Parameter checks
equations
assert(area_A > 0)
assert(area_B > 0)
assert(area_C > 0)
end
variables (Access = protected)
mdot_A = {0, 'kg/s'}; % Mass flow rate into port A
mdot_B = {0, 'kg/s'}; % Mass flow rate into port B
mdot_C = {0, 'kg/s'}; % Mass flow rate into port C
Phi_A = {0, 'kW' }; % Energy flow rate into port A
Phi_B = {0, 'kW' }; % Energy flow rate into port B
Phi_C = {0, 'kW' }; % Energy flow rate into port C
end
branches
mdot_A : A.mdot -> *;
mdot_B : B.mdot -> *;
mdot_C : C.mdot -> *;
Phi_A : A.Phi -> *;
Phi_B : B.Phi -> *;
Phi_C : C.Phi -> *;
end
if power_spec == foundation.enum.power_spec.isentropic
variables (Access = private, ExternalAccess = none)
u_in_A = {1500, 'kJ/kg'}; % Specific internal energy for inflow at port A
u_in_B = {1500, 'kJ/kg'}; % Specific internal energy for inflow at port B
u_in_C = {1500, 'kJ/kg'}; % Specific internal energy for inflow at port C
u_out_A = {1500, 'kJ/kg'}; % Specific internal energy for outflow at port A
u_out_B = {1500, 'kJ/kg'}; % Specific internal energy for outflow at port B
u_out_C = {1500, 'kJ/kg'}; % Specific internal energy for outflow at port C
end
intermediates (Access = private, ExternalAccess = none)
% Compute change in specific entropy
[Ds_AB, ht_in_A, ht_out_B] = foundation.two_phase_fluid.sources.isentropic_relation( ...
A.p, B.p, u_in_A, u_out_B, mdot_A, area_A, area_B, ...
A.u_min, A.u_max, A.unorm_TLU, A.p_TLU, A.v_TLU, A.s_TLU, A.u_sat_liq_TLU, A.u_sat_vap_TLU);
[Ds_BA, ht_in_B, ht_out_A] = foundation.two_phase_fluid.sources.isentropic_relation( ...
B.p, A.p, u_in_B, u_out_A, mdot_B, area_B, area_A, ...
A.u_min, A.u_max, A.unorm_TLU, A.p_TLU, A.v_TLU, A.s_TLU, A.u_sat_liq_TLU, A.u_sat_vap_TLU);
end
% For logging
intermediates (Access = private)
power = if ge(M, 0), mdot_A*(ht_out_B - ht_in_A) else mdot_B*(ht_out_A - ht_in_B) end; % Power added to fluid flow
end
equations
% Isentropic relation between inflow and outflow
Ds_AB == 0;
Ds_BA == 0;
% Specific total enthalpy for outflow
ht_out_A == convection_A.ht_I;
ht_out_B == convection_B.ht_I;
end
else % power_spec == foundation.enum.power_spec.none
% For logging
intermediates (Access = private)
power = {0, 'kW'}; % Power added to fluid flow
end
end
equations
% Commanded mass flow rate
mdot_A == M;
% Mass balance
mdot_A +mdot_C +mdot_B == 0;
% Energy balance
Phi_A + Phi_B + Phi_C + power == 0;
% Run-time variable checks
assert(A.p >= A.p_min, message('physmod:simscape:library:two_phase_fluid:PressureMinValid', 'A'))
assert(A.p <= A.p_max, message('physmod:simscape:library:two_phase_fluid:PressureMaxValid', 'A'))
assert(A.u >= A.u_min, message('physmod:simscape:library:two_phase_fluid:InternalEnergyMinValid', 'A'))
assert(A.u <= A.u_max, message('physmod:simscape:library:two_phase_fluid:InternalEnergyMaxValid', 'A'))
assert(B.p >= B.p_min, message('physmod:simscape:library:two_phase_fluid:PressureMinValid', 'B'))
%assert(B.p <= B.p_max, message('physmod:simscape:library:two_phase_fluid:PressureMaxValid', 'B'))
assert(B.u >= B.u_min, message('physmod:simscape:library:two_phase_fluid:InternalEnergyMinValid', 'B'))
assert(B.u <= B.u_max, message('physmod:simscape:library:two_phase_fluid:InternalEnergyMaxValid', 'B'))
end
% Internal components that calculate energy convection at ports A and B
components (ExternalAccess = none)
convection_A = foundation.two_phase_fluid.port_convection(flow_area = area_A, length_scale = sqrt(4*area_A/pi));
convection_B = foundation.two_phase_fluid.port_convection(flow_area = area_B, length_scale = sqrt(4*area_B/pi));
end
connections
connect(A, convection_A.port)
connect(B, convection_B.port)
end
% Equate variables for internal components that calculate energy convection at ports A and B
equations
convection_A.mdot == mdot_A;
convection_A.Phi == Phi_A;
convection_B.mdot == mdot_B;
convection_B.Phi == Phi_B;
convection_A.ht_I == convection_B.ht_I;
end
end
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Réponses (1)

Abhishek Chakram le 6 Fév 2024
Hi ,
It looks like you are trying to add a make-up port to a controlled mass flow source component in a Simscape language model. The error message: Cannot find parameter “area_C" suggests that there is a problem with the definition or usage of the parameter “area_C” in your model.
Here are the steps to address the issue and adjust the position of interface C:
• It seems that you already have “area_C” defined in the parameters section of your component. Make sure that it is not commented out or removed accidentally.
• To adjust the position of interface C, you will need to define how the mass flow rate into port C (“mdot_C”) is controlled. This could be done by creating another input similar to `M` for port C or by defining a relationship between “mdot_C” and other variables in the model.
• You will need to add equations that describe the behavior of port C, like how ports A and B are described. This includes mass balance, energy balance, and any specific conditions or constraints for port C.
• If port C also exchanges energy, you might need to add another internal component like “convection_C” for energy convection calculations at port C.
Here is a sample code for the same:
% Add the internal component for Port C
components (ExternalAccess = none)
convection_C = foundation.two_phase_fluid.port_convection(flow_area = area_C, length_scale = sqrt(4*area_C/pi));
end
% Add the connection for Port C
connections
connect(C, convection_C.port)
end
% Update the energy convection equations to include Port C
equations
convection_C.mdot == mdot_C;
convection_C.Phi == Phi_C;
end
% Update the energy balance equation to include Port C
equations
% Energy balance
Phi_A + Phi_B + Phi_C + power == 0;
end
I hope this helps!
Best Regards,
Abhishek Chakram
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