Two way valve with polynomial opening characteristic. The
polynomial coefficients are defined using parameter c.
The elements of c are coefficients for increasing
powers of y, starting with the power 0,
which corresponds to a fixed offset. This valve model can be used
to implement valves with a custom opening characteristic, such as a
combination of a linear and an equal percentage characteristic.
This model is based on the partial valve model IBPSA.Fluid.Actuators.BaseClasses.PartialTwoWayValve. Check this model for more information, such as the regularization near the origin.