What is draft tube in hydro power plant?

The draft tube is an important component of a Francis turbine which influences the hydraulic performance. It is located just under the runner and allowed to decelerate the flow velocity exiting the runner, thereby converting the excess of kinetic energy into static pressure.

Why draft tube is used in turbine?

Which turbine uses draft tube?

It is used in the Kaplan turbine. In this type of draft tube, the cross-section area remains the same for the entire length of the draft tube. The inlet and outlet of the draft tube are circular. This draft tube is used at low head positions and the turbine is to be mounted next to the tailrace.

What is the purpose of Draught tube?

The main function of draft tube is to decelerate the velocity and increase the pressure of the fluid flowing from the runner exit to tail race. Water enters into the penstock and strikes the turbine vanes and reduces its pressure.

Which of the following turbine does not require a draft tube?

Pelton turbine. …

What is difference between impulse and reaction turbine?

What is the difference between the Impulse and Reaction Turbine? In an Impulse turbine, All hydraulic energy is converted into kinetic energy by a nozzle whereas In a Reaction turbine Only some amount of the available energy is converted into kinetic energy.

Where are draft tube used?

Draft Tube is a diverging tube fitted at the exit of runner of turbine and used to utilize the kinetic energy available with water at the exit of runner. ‘. This draft tube at the end of the turbine increases the pressure of the exiting fluid at the expense of its velocity.

Which principle is used in hydraulic turbine?

principle of momentum
A Hydraulic Machine uses the principle of momentum, which states that a force is generated and is utilized in a turbine.

Which kind of turbine is fourneyron turbine?

The Fourneyron turbine is reaction turbine.

Why the draft tube is not used for Pelton turbine?

A draft tube is generally not used since the runner operates under approximately atmospheric pressure and the head represented by the elevation of the unit above tailwater cannot be utilized. Since this is a high-head device, this loss in available head is relatively unimportant.

Why it is called reaction turbine?

The nozzle-guide vanes only guide the flow for the rotors. The turbine is driven by the reaction force resulting from the acceleration of gases through the converging blade passage and, hence, the name.

How is a draft tube used in a turbine?

To avoid this problem of back flow a draft tube is used between turbine exit and tale race. It increases the pressure of exit water at the expense of its kinetic energy. Now, the increased pressure of water becomes some what above to the atmospheric pressure. It solves our problem of back flow of water from the tail race to the exit of turbine.

Do you need a draft tube for Pelton turbines?

Do Pelton (or Impulse) turbines needs Draft Tube? No, in case of impulse turbines the head available to the turbine is very large which results in an above atmospheric pressure at the turbine exit. Since we have a above atmospheric pressure of water at the turbine exit then there is no problem of back flow of water.

How is the efficiency of a hydro turbine affected?

The efficiency of a hydraulic reaction turbine is significantly affected by the efficiency of its draft tube. The shape (profile) and velocity distribution at the inlet affect the performance of the draft tube. So far, the design of draft tubes has been improved through experimental observations resulting in ‘rules of thumb’ and empirical formulae.

Which is the tail race of a draft tube?

A draft tube is a kind of tube which connects (or acts as an intermediately) between the water turbine exit and tail race. Note: Tail race is the water channel that carries away water from the turbine exit. A draft tube has an increasing cross-sectional area from the inlet to the out let (as shown in figure).