Fluid Machinery (Hydraulic Turbines)

Penstock

A closed conduit or pipe for conducting water to the powerhouse.

Micro Hydropower

A micro hydropower plant has a capacity of up to 100 kilowatts. A small or micro-hydroelectric power system can produce enough electricity for a home, farm, ranch, or village.

Brake Nozzle

A nozzle directed at the back of the buckets, which is opened when there is a need to slow down or stop the turbine.

Cavitation

A phenomenon which occurs when the pressure at a point in a hydraulic system is lowered below the vapor pressure of the oil in the system. This allows bubbles of oil vapor to form in the oil. If this occurs at the pump inlet, the quick pressure rise inside the pump forces these bubbles to collapse violently. This can cause erosion of metal parts, noise and vibration.

Turbine

A rotary engine that converts the energy of a moving stream of water, steam or gas into mechanical energy.

Trash Rack

A screen that prevents the leaves, branches and other water contaminants to enter into the penstock.

Sluice Gate

A sliding gate used to control the flow of water.

Wicket gates

Adjustable elements that control the flow of water from the scroll case into the turbine passage.

Large Hydropower

Although definitions vary, the U.S. Department of Energy (DOE) defines large hydropower as facilities that have a capacity of more than 30 megawatts.

Guide mechanism/ Guide vane

It consists of a circular wheel all-round the runner of the turbine. The stationary guide vanes are fixed on the guide wheel. The guide vanes allow the water to strike the vanes fixed on the runner without shock at inlet.

Overall efficiency

It is the ratio of the power available at the turbine shaft to the power available from the jet.

Mechanical Efficiency

It is the ratio of the power available at turbine shaft to the power available at turbine runner.

Hydraulic efficiency

It is the ratio of the power developed by runner to the power supplied at the inlet of the turbine.

Volumetric efficiency

It is the ratio of volume of water actually striking the runner to the total water supplied by the jet to the turbine.

Shaft Seal

Prevent water leakage between main shaft and head cover.

Guide Bearing

Resists the mechanical imbalance and hydraulic side loads from the turbine runner thereby maintaining the turbine runner in its centered position in the runner seals.

Deflectors

Serves to bend the jet away from the runner at reduced loads to avoid a high speed increase.

Head cover

Supports the weights of guide vanes and confine the vibrations and unnecessary movements of the wicket gates.

Small Hydropower

The DOE defines small hydropower as facilities that have a capacity of 100 kilowatts to 30 megawatts.

Splitter

The dividing wall which separates each bucket of a pelton turbine into two symmetrical parts.

Tailrace

The downstream channel that carries water away from a dam or powerhouse.

Hub

The part of the runner to which blades are mounted.

Hydropower ("Hydro")

The process of generating electricity by capturing the potential energy of falling water through the use of a water wheel (turbine) to mechanically spin rotating magnets which create electrical current that can be distributed to users by transmission lines.

Turbine Shaft

The rotating element, usually circular in cross section, which is used to transmit power from the turbine runner to the generator shaft and generator rotor.

Runner or Impeller

The rotating part of the turbine that converts the energy of falling water into mechanical energy.

Specific Speed

The speed at which the turbine will run when developing one unit power under a unit head.

Stator

The stationary part of a rotary system, found in electric generators and electric motors. Its main purpose is to keep the field aligned.

Spillway

The structure or portion of a larger structure that is used to release excess water over or around a dam.

Tail water

The water level downstream of the powerhouse or dam.

Vane

a broad blade attached to a rotating axis or wheel that pushes or is pushed by wind or water and forms part of a machine or device such as a windmill, propeller, or turbine.

Duct

a channel or tube for conveying.

Dam

a concrete structure that impounds water for irrigation and hydropower purposes.

Motor

a device that converts electrical energy to mechanical energy.

Generator

a device that converts mechanical energy to electrical energy. An arrangement of magnets spinning inside a coil of wire to produce electricity.

Reservoir

a large natural or artificial enclosure used as a source of water supply in a hydraulic system.

Water wheel

a large wheel driven by flowing water, used to work machinery or to raise water to a higher level.

Vortex

a mass of whirling fluid or air, such as a whirlpool or whirlwind.

Propeller

a mechanical device for propelling a boat or aircraft, consisting of a revolving shaft with two or more broad, angled blades attached to it.

Waterway

a river, canal, or other route for travel by water.

Scroll Casing

a spiral casing with a decreasing area to make sure that water flows into the central portion of the Kaplan turbine at uniform velocity.

Affinity Laws

allow the output of a turbine to be predicted based on model tests.

Turgo Turbine

also known as a half Pelton turbine, it is an impulse turbine which uses spoon-shaped blades to capture the jet of water.

Axis

an imaginary line about which a body rotates.

Pentrough

an open usually planked or boarded trough or tank from which water falls onto a waterwheel.

Buckets

cups or bowls attached to the runner which take the impact of water from the nozzle causing the runner to rotate.

Slit Sluice

is a chamber that collects the mud and through which the mud is discharged.

Draft Tube

is a conically shaped conduit attached to the turbine discharge. It slows down the high discharge velocity water coming from the runner as it discharges to the tail race.

Hydraulic turbine

is a prime mover that converts the kinetic energy and potential energy of flowing water into mechanical power for the purpose of driving an electrical generator or other machinery.

Kaplan Turbine

is a propeller type water turbine with the adjustable blades which work in reverse. Mainly designed for low head water applications.

Forebay or Pre-dam

is a small reservoir where water is temporarily stored. It is used to trap sediment and debris to ensure that clean water enters the penstock.

Surge Chamber

is a standpipe connected to the penstock and open to the atmosphere so that the water will always be at atmospheric pressure.

Pelton Turbine

is a tangential flow impulse turbine that uses double curved buckets to capture the jet of water. It is primarily used for high heads.

Francis Turbine

is an Inward Flow Reaction Turbine having Radial Discharge at Outlet.

Hydroelectricity

is electricity produced from hydropower.

Nozzle

is provided at end of penstock and its main function is to increase the velocity of the water and to direct it to the buckets of the turbine.

Spear

is provided within the pen stock and its main function are to increase and decrease the amount and speed of water entering the turbine. If more water is needed the spear is moved back to allow more to enter into the turbine and if less water is needed the spear moves forward to decrease the amount of water entering the turbine.

Maximum Head (Hmax)

is the gross head difference in elevation between the maximum forebay (head water) level without surcharge and the tailrace level without spillway discharge. Under this condition, hydraulic losses are negligible and may be disregarded.

Blade

is the individual component responsible for extracting energy from the velocity of the water jet and uses it to do mechanical work on a rotating output shaft.

Design Head (Hd)

is the net head at which peak efficiency is desired. This head should preferably approximate the weighted average head, but must be so selected that the maximum and minimum heads are not beyond the permissible operating range of the turbine. This is the head which determines the basic dimensions of the turbine and therefore of the power plant.

Minimum Head (Hmin)

is the net head resulting from the difference in elevation between the minimum forebay (head water) level and the tailrace level minus losses with all turbines operating at full specified gate opening.

Braking Jet

the jet of water produced by the break nozzle.

Efficiency

the ratio of the useful work performed by a machine or process to the total energy expended or heat taken in.

Runaway Speed

the speed at full flow, and no shaft load.

Head Water

water level at supply reservoir.