PACFramework
Vessel with One Inlet and One Outlet (smLevelCyl)
Brief Description and Purpose
A function block that simulates the operation of level sensors for a vessel with one inlet and one outlet, used in the simulation model as dosing vessels D1 and D2 (Fig. 1).
Fig. 1. Image of the simulated installation for testing PACFramework blocks.
The block receives inlet and outlet flow rates (in m³/s or L/s) as inputs, and outputs the level value L in meters or centimeters depending on the input units. It also simulates the LSH (high-level sensor) and LSL (low-level sensor) signals.
The parameters V0, Vmax, and S are set externally or by default. The parameter d_t defines the call period for correct dynamic calculation and can be used to adjust the simulation speed.
Implementation in IEC-61131
ST
FUNCTION_BLOCK "smLevelCyl1"
VAR_INPUT
INIT : Bool; // initialization command (sets initial conditions)
Fin : Real; // inlet flow rate specified in m3/s or L/s
Fout : Real; // outlet flow rate specified in m3/s or L/s
END_VAR
VAR_OUTPUT
L : Real; // level in meters or centimeters
LSH : Bool; // high-level sensor
LSL : Bool; // low-level sensor
END_VAR
VAR
d_t : Real := 0.1; // call period in seconds
V0 : Real; // initial volume value during model initialization
V : Real; // liquid volume in the vessel
Vmax : Real := 50.0; // vessel volume
S : Real := 20.0; // specified in m2 for m3/s or cm2 for L/s
END_VAR
BEGIN
IF INIT THEN
V := V0; (* set to minimum volume on initialization *)
ELSE
V := V + d_t * (Fin - Fout); (* volume increment *)
IF V < 0.0 THEN V := 0.0; END_IF; (* lower limit *)
IF V > Vmax THEN V := Vmax; END_IF; (* upper limit *)
L := V / S;
LSH := (V / Vmax) > 0.999; (* high-level sensor *)
LSL := (V / Vmax) > 0.001; (* low-level sensor *)
END_IF;
END_FUNCTION_BLOCK