Gross head, maximum flow, inlet penstock and runner height: the Layout tab describes the site before any machine.

Overview: Hydro Turbine design

The Layout tab receives what the site imposes: the head, the flow, the penstock that brings the water and the runner position relative to the tailwater level. Everything else in the window follows from it.

Contents:

• Gross head, site flow and height H2
• Inlet penstock: velocity and head loss
• Site power: ρ·g·Q·Hb

Gross head, site flow and height H2

• Hb, gross head (m): difference in altitude between the surface of the upstream reservoir and that of the downstream reservoir. It is an available pressure, not a velocity: the whole method of the window follows from this.
• Site max flow (m³/s): maximum flow that can be turbined. The software also shows it in m³/h. The + and − buttons adjust it by steps.
• H2, runner outlet height (m): height between the tailwater surface and the runner outlet, or its axis if the shaft is horizontal. It sets the pressure under the runner, hence the cavitation risk: the larger H2, the lower the pressure at the runner outlet.
• Junction duct and elbow: if the draft tube length and H2 do not allow a vertical draft tube, Heliciel says so and adds a horizontal junction duct and an elbow, showing their length and head losses.

Example

The vertical view shows the headwater and tailwater levels, the height H2 and the draft tube with its elbow.

Inlet penstock: velocity and head loss

Inputs: length (m), diameter (mm), roughness (mm), typed directly or set by choosing a material in the list.

Results: section (cm²), velocity in the penstock (m/s), friction loss (m), computed with the Colebrook formula.

Every metre lost in the penstock is taken from the head the runner receives (Hn = Hb − path losses). A penstock that is too small accelerates the water, and the loss grows roughly as the square of the velocity.

Example

The whole installation in 3D: the penstock connects the headwater reservoir to the spiral casing.

Site power: ρ·g·Q·Hb

This block shows the gross site power, P = ρ·g·Q·Hb, in kilowatts and in horsepower, from the maximum flow and the gross head of the tab. It is the physical ceiling: path losses reduce it to ρ·g·Q·Hn, the power available at the runner, and the runner converts part of it into shaft power. These three levels are plotted in the Results tab.

Example

The power chart: maximum site power, available power, axial kinetic power and shaft power.

Going further

The Hydro Turbine design reference page presents the complete method and a worked case. The other help pages of the window:

• Control panel
• Layout
• Spiral casing
• Distributor
• Runner
• Draft tube
• Specific speed
• Statistics
• Views and piezometric graph
• Fabrication kit
• Results, method, errors