Dynamic Modelling of pressure reducing valves

No generally accepted representation of a Pressure Reducing Valve (PRV).

Pressure control reduces background leakage/pipe bursts.

Single feed = ease of control but loss of feed if fail.
Multi feed = increase security but less well understood/easy to model.

Differential algebraic equation or PDAE (Partial DAE) describe water network dynamics.

4 models in this paper

1. Detailed phenomenological model - constructed from applying physical laws to individual elements in PRV. Model is accurate but complex - solution in larger networks/linked to transient pipe is difficult. Basis for simpler models and gold standard to compare by.

2. Simplified version of phenomological model.

3. Behavioural model formed by observations of PRV on a test rig. Simplest model - very easy to solve. Reduction in accuracy.

4. Linear model - linearise the phenomenological model about its steady state. Model independant of needle setting in PRV.

PRV - valve operated by a control loop via orifice, pilot valve and needle valve connecting loop to the control space.

Actual Outlet Pressure > Required Outlet Pressure - pilot valve closes causing increase in T-junction pressure. Control space pressure increases causing main valve to close. Reduces outlet pressure.

Inlet Pressure < Required Outlet Pressure - PRV opens and acts as a short pipe.

Outlet Pressure > Inlet Pressure - completely closes to prevent reverse flow.

PRV = system of DAEs to solve. Ease depends on size of network, type of pipe model and choice of PRV model.