.AixLib.Fluid.Actuators.BaseClasses.exponentialDamper

Information

This function computes the opening characteristics of an exponential damper.

The function is used by the model AixLib.Fluid.Actuators.Dampers.Exponential.

For yL < y < yU, the damper characteristics is

k_d(y) = exp(a+b (1-y)).

Outside this range, the damper characteristic is defined by a quadratic polynomial.

Note that this implementation returns sqrt(k_d(y)) instead of k_d(y). This is done for numerical reason since otherwise k_d(y) may be an iteration variable, which may cause a lot of warnings and slower convergence if the solver attempts k_d(y) < 0 during the iterative solution procedure.

Interface

function exponentialDamper
  extends Modelica.Icons.Function;
  input Real y(min = 0, max = 1, unit = "") "Control signal, y=0 is closed, y=1 is open";
  input Real a(unit = "") "Coefficient a for damper characteristics";
  input Real b(unit = "") "Coefficient b for damper characteristics";
  input Real[3] cL "Polynomial coefficients for curve fit for y < yl";
  input Real[3] cU "Polynomial coefficients for curve fit for y > yu";
  input Real yL "Lower value for damper curve";
  input Real yU "Upper value for damper curve";
  output Real kThetaSqRt(min = 0) "Square root of loss coefficient, sqrt(pressure drop/dynamic pressure)";
end exponentialDamper;

Revisions

• April 14, 2014 by Michael Wetter:
  Improved documentation.
• July 1, 2011 by Michael Wetter:
  Added constraint to control input to avoid using a number outside 0 and 1 in case that the control input has a numerical integration error.
• April 4, 2010 by Michael Wetter:
  Reformulated implementation. The new implementation computes sqrt(kTheta). This avoid having kTheta in the iteration variables, which caused warnings when the solver attempted kTheta < 0.
• June 22, 2008 by Michael Wetter:
  First implementation.