Fundamentally, a turbine is a type of rotating equipment designed to remove energy from a fluid. For a given flow rate, turbines remove a specific amount of the fluid’s energy head. WaterCAD 2024 provides a single but very powerful turbine representation:

• Turbine between 2 Pipes—A turbine that undergoes electrical load rejection at time zero, requiring it to be shut down rapidly. The four-quadrant characteristics of generic units with certain specific speeds are built into WaterCAD 2024. The turbine element allows nonlinear closure of the wicket gates and is equipped with a spherical valve that can be closed after a time lag. It has the following parameters:
• Time (Delay until Valve Operates) is a period of time that must elapse before the spherical valve of the turbine activates.
• Time for Valve to Operate is the time required to operate the spherical valve. By default, it is set equal to one time step.
• Pattern (Gate Opening) describes the percentage of wicket gate opening with time.
• Operating Case allows you to choose among the four possible cases: instantaneous load rejection, load rejection (requires torque/load vs time table), load acceptance and load variation.
• Diameter (Spherical Valve) is the diameter of the spherical valve.
• Efficiency represents the efficiency of the turbine as a percentage. This is typically shown on the curves provided by the manufacturer. A typical range is 85 to 95%, but values outside this range are possible.
• Moment of Inertia The moment of inertia must account for the turbine, generator, and entrained water.
• Speed (Rotational) denotes the rotation of the turbine blades per unit time, typically as rotations per minute or rpm. The power generated by the turbine depends on it.
• Specific Speed enables you to select from four-quadrant characteristic curves to represent typical turbines for three common types:
  • SPECIFIC SPEED (US/SI): 30 / 115 Range: US 25-40, SI 111-178
  • SPECIFIC SPEED (US/SI): 45 / 170 Range: US 40-48, SI 178-214
  • SPECIFIC SPEED (US/SI): 60 / 230 Range: US 48-75, SI 214-334

  The predefined 4-quadrant curves can be used for a range of turbine specific speeds, so the range is specified for each type. This will help you select a turbine curve when you know the turbine specific speed.

  The predefined quadrants are stored in an auxiliary data txt file in the installation directory, named "QuadrantCurvesPredefined.txt". There is also an auxiliary data txt file for user-defined 4-quadrant curves in the installation directory, named "QuadrantCurves.txt".

The equation to estimate specific speed for a turbine is as follows:

In US units n is in rpm, P is in hp, and H is in ft.In SI units n is in rpm, P is in kW, and H is in m.

• Turbine Curve For a transient run, HAMMER uses a 4-quadrant curve based on Specific Speed, Rated Head, and rated Flow. This is only used for steady state computations.
• Flow (Rated) denotes the flow for which the turbine is rated.
• Head (Rated) denotes the head for which the turbine is rated.
• Electrical Torque Curve defines the time vs torque response for the turbine. Only applies to the Load Rejection operating case.