Draft Tube & Specific Speed topics include: Draft tube types and theory, draft tube efficiency, specific speed derivation, specific speed significance and problems. A draft tube is a component of a reaction turbine that recovers the kinetic energy of water flow leaving the runner. The amount of energy recovered depends on the turbine type, flow capacity, and specific speed. For high specific speed turbines, the draft tube's influence on turbine efficiency is more significant. There are two types of draft tubes: Conical diffuser or straight divergent tube: This type of draft tube has a... Show more Draft Tube & Specific Speed topics include: Draft tube types and theory, draft tube efficiency, specific speed derivation, specific speed significance and problems. A draft tube is a component of a reaction turbine that recovers the kinetic energy of water flow leaving the runner. The amount of energy recovered depends on the turbine type, flow capacity, and specific speed. For high specific speed turbines, the draft tube's influence on turbine efficiency is more significant. There are two types of draft tubes: Conical diffuser or straight divergent tube: This type of draft tube has a conical diffuser with a half angle of 10° or less to prevent flow separation. It's typically used for low specific speed, vertical shaft francis turbines. Simple elbow type draft tube: This type of draft tube has an extended elbow type tube. It's usually used when the turbine needs to be placed close to the tail-race. The shape of the draft tube is important, especially for high specific speed turbines. A draft tube is made divergent to reduce the velocity at the outlet to a minimum. A turbine's specific speed is the speed of a similar turbine that would produce one kilowatt of power under a one-meter head. The manufacturer provides the specific speed, which corresponds to the point of maximum efficiency The specific speed of a turbine is a non-dimensional value that describes all operating conditions that can be covered by similar flow in geometrically similar pumps. Any change in specific speed requires a corresponding change in pump geometry or a change in flow conditions. The specific speed of a turbine is a parameter that relates the characteristic data of the turbine. It can identify families of geometrically similar machines. These machines can have very different powers and sizes, but they all have one fundamental common characteristic. Show less
Draft Tube & Specific Speed topics include: Draft tube types and theory, draft tube efficiency, specific speed derivation, specific speed significance and problems.
A draft tube is a component of a reaction turbine that recovers the kinetic energy of water flow leaving the runner. The amount of energy recovered depends on the turbine type, flow capacity, and specific speed. For high specific speed turbines, the draft tube's influence on turbine efficiency is more significant.
There are two types of draft tubes: Conical diffuser or straight divergent tube: This type of draft tube has a conical diffuser with a half angle of 10° or less to prevent flow separation. It's typically used for low specific speed, vertical shaft francis turbines. Simple elbow type draft tube: This type of draft tube has an extended elbow type tube. It's usually used when the turbine needs to be placed close to the tail-race.
The shape of the draft tube is important, especially for high specific speed turbines. A draft tube is made divergent to reduce the velocity at the outlet to a minimum.
A turbine's specific speed is the speed of a similar turbine that would produce one kilowatt of power under a one-meter head. The manufacturer provides the specific speed, which corresponds to the point of maximum efficiency
The specific speed of a turbine is a non-dimensional value that describes all operating conditions that can be covered by similar flow in geometrically similar pumps. Any change in specific speed requires a corresponding change in pump geometry or a change in flow conditions. The specific speed of a turbine is a parameter that relates the characteristic data of the turbine. It can identify families of geometrically similar machines. These machines can have very different powers and sizes, but they all have one fundamental common characteristic.
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