Kaplan Turbine : Parts, Working, Advantages and Disadvantages

Kaplan turbine is from the reaction turbine categories of hydraulic turbine. Kaplan turbine is name after its inventor Viktor Kaplan. It was the first hydraulic turbine which work in low head and high flow rate. 

Kaplan turbine is also known as the propeller turbine because its blades are just like propeller and working phenomena is same but opposite in direction and this make Kaplan turbine fit for use in rivers and low head area.

Its recommended to read our article on Francis Turbine and Pelton Wheel Turbine to know all about their parts, working and advantages and disadvantages. 

Parts of Kaplan Turbine

Hub

Hub is the part on which blades of the turbine are attached which is attached to the central shaft of the turbine

Blades

Blades of the Kaplan turbine are like the propeller. Blades of other axial turbine are planer but that of Kaplan are not planer instead they are of twist shape along the length to allow the swirling flow of water at entrance and exist.

Guide vanes or wicket gates

Function of the wicket gate is to direct the flowing water toward the blades of the turbine

Shaft

Rotation motion of the blades is transfer to the generator by means of shaft which is a long solid part of the turbine.

Blade control mechanism

Blades at point of their attachment have movable joints. Blade control mechanism control the angle of attack by which water will strike the blades by rotating the blades because of their movable joint.

Governing mechanism

Governing mechanism control the movement of the guide vanes. When power requirement is high it open the guide vane and when power requirement is low is close the guide vanes

Scroll casing

The whole mechanism of the Kaplan turbine is closed in a casing called scroll casing. Scroll casing take water from the resource and direct it towards the blades with the help of the guide vanes.

Draft tube

Waster after passing through the blades is take put of the turbine by the means of the draft tube. Draft tube decrease the velocity of the water by increasing its area.

Kaplan Turbine Parts Diagram

Working of Kaplan Turbine

Water having low head and high flow rate is collected by the scroll casing whose continuously decreasing are in flow direction make shore that water moves with the uniform velocity until it reached the guide vanes and water then directed toward the blades by the guide vanes. 

Between guide vanes and blades their is a curve passage whose main function is to convert the radial flow of water into the axial flow. 

After the curve passage water flow over the blades and creates the high and low pressure region and thus their establish a lift force which force the blades to move from high pressure region to low pressure region.

To learn the difference between different turbine type read our article Frances Turbine vs Kaplan Turbine

Advantages of Kaplan Turbine

• Runner vanes are adjustable

• In Kaplan Turbine a very low head is required

• Kaplan Turbine has very small number of blades 3 to 8

• Very less resistances have to be over come

Disadvantages of Kaplan Turbine

• The disposition of shaft is only in vertical direction

• A very large flow rate is required

• In Kaplan Turbine a specific speed is 250-850

• In Kaplan Turbine a heavy duty generator is required

Francis Turbines : Parts, Working, Advantages and Disadvantages

Francis turbine is from the reaction turbine class of hydraulic turbine. It is name after its inventor James Francis. 

It was the first turbine with the radial flow, water enter the turbine radially and leave axially. 

High pressure water entering the turbine strike the blades of turbine and reaction of which blades of turbine rotates.

Its recommended to read our article on Kaplan Turbine and Pelton Wheel Turbine to know all about their parts, working and advantages and disadvantages

Francis Turbine Parts

Pen stock

It is a large size pipe which take water from the reservoir and take it to the turbine runner

Spiral / scroll casing

It is a close end passage with maximum cross section area at the inlet which decrease continuously along the direction of flow and finally zero at the outlet

Guide vanes / wicket gates

Main function of the guide vanes is to guide the water toward the runner at an angle appropriate for the design

Governing mechanism

Main function of the governing mechanism is to change the angle of attack at runner by guide vanes when flow rate of the water is changing

Runner and Runner blades

There are 16 to 24 runner blades attached to the runner. Runner blades the the direct action of water and rotate the runner. runner rotate due to both impulse and reaction forces

Bottom Ring

provide drainage space

Shaft Seal

Prevent water leakage between main shaft and head cover.

Draft Tube

It is gradually expanding tube which discharge water passing through the runner, to the tail race

Working of Francis turbine

As water enter the turbine through the inlet nozzle its velocity will decrease as it moves forward in the turbine but the continuous decrease in the area of spiral casing will not let it happen. Design of spiral casing makes shore that the water strike the each blade of the turbine as a constant speed.

Francis Turbine Working

Blades are mounted on the runner. Design of the blade is like a thin air foil so when water flow over it low pressure is created at one point and high pressure is created on other side

and motion take place from high pressure to low pressure. Lower side of the blade is like a bucket which use the impulse forces of water in the rotation.

Francis Turbine Blades

If water flow rate change then governing mechanism came into use and change the angle of attack of water on to the blade so the turbine can work properly. After the water passes the blades it enter the draft tube whose continuous increase in area decrease the velocity of the water.

Francis Turbine Draft Tube

To learn the difference between different turbine type read our article Difference Between Inward Flow and Outward Flow Reaction Hydro Turbine

Advantages of Francis turbine

• Easy control on changing head

• Size of runner and generator is small

• Small change in efficiency over time

• The operating head can be utilized even when the variation in the tail water level is relatively large when compared to total head

Disadvantages of Francis turbine

• Unclean water can create wear 

• Inspection method is very difficult

• Cavitation is an ever present danger

• Water hammer effect can create some problems

• Head 50% lower can have harmful effect on the efficiency as well as cavitation danger became more serious

Pelton wheel turbine : Parts, Working, Advantages and Disadvantages

Pelton wheel turbine is from the impulse turbine categories of hydraulic turbine. Pelton turbine was named after its inventor Allan Pelton. There are many other types of impulse turbine but Pelton  turbine is the most efficient from all of them. 

Its recommended to read our article on Francis Turbine and Kaplan Turbine to know all about their parts, working and advantages and disadvantages. 

Parts of Pelton Wheel Turbine

Pen stock

Pen stock is a solid pipe which take water from the dam( structure which store water on its one side) and take it to the turbine at very high speed.

Spear

A spear is provided with in the pen stock and its main function is to increase and decrease the speed of water entering into the turbine. If more water is needed spear move back and allow more to enter into the turbine and if less water is needed spear moves forward to spot excess water from entering in to the turbine.

Nozzle

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

Buckets

Each Pelton wheel turbine has a specific number of buckets attached to its runner. Buckets take the impact of water and start to rotate along the runner

Runner

Runner is a heavy circular disc on which buckets are attached. Runner is further attached to the shaft. 

Brake nozzle

When turbine is need to be stopped then water is thrown at the back of the buckets from another nozzle called brake nozzle

Casing

The whole setup of the turbine is enclosed in a structure called the casing of the turbine

Pelton Wheel Turbine Diagram

To learn the difference between different turbine type read our article Frances Turbine vs Kaplan Turbine

Working of the Pelton wheel turbine

Dam store water at its one side when water level is increased at a specific height then the gates of the dam is open and water start to flow through the pen stock. 

Nozzle at the end of the pen stock convert this high speed water into a water jet which on striking the bucket convert its kinetic energy into the rotation energy of the buckets and the runner. 

Runner is attached to the shaft which is further attached to a generator. Rotating runner rotates the shaft which rotates the generator. 

Different efficiency

Hydraulic efficiency 

It is the ratio of the power developed by runner to the power supplied at in let of turbine

Mechanical efficiency

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

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

Overall efficiency

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

Advantages of Pelton wheel turbine

• Most efficient of all turbines

• High overall efficiency

• Easy assembly 

• Operate at low discharge

• Flat efficiency curve

• Can be operation in silted water

Disadvantages of Pelton wheel turbine

• Decrease in efficiency with time

• Components have large size

• Variation in the operating head is very difficult to control

• The operating head cannot be utilized even when the variation in the tail water level is relatively large when compared to total head

Top 7 Difference Between Inward Flow and Outward Flow Reaction Hydro Turbine

To know the difference between the inward flow and outward flow reaction hydro turbines we will compare them on the following points 

1. Energy of water 

2. Centrifugal head imparted 

3. Discharge 

4. Discharge 

5. Wheel tendency to race 

6. Suitability 

7. Application 

To learn the difference between different turbine type read our article Frances Turbine vs Kaplan Turbine

Difference between inward flow and outward flow reaction hydro turbine 

Energy of water

In Inward flow reaction hydro turbine water enters at the outer periphery, flows inward and toward the center of the turbine, and discharges at the outer periphery whereas in outward flow reaction hydro turbine water enters at the inner periphery flows outward, and discharges at the outer periphery 

Centrifugal head imparted

In the Inward flow reaction hydro turbine negative centrifugal head reduces the relative velocity of water at the outlet whereas in the outward flow reaction hydro turbine positive Centrifugal head increases the relative velocity of water at the outlet.

Discharge

In an Inward flow reaction hydro turbine, the discharge does not speed up at exit whereas, in an outward flow reaction hydro turbine, the discharges do speed up at the Hostetler.

Speed control

In inward flow reaction hydro turbine it's easy to control the speed of the turbine effectively whereas, in an outward flow reaction hydro turbine, it's very difficult to control the turbine its speed.

The tendency of the wheel to race

an In inward flow reaction hydro turbine there is no tendency for the wheel to race with increasing speed whereas an in an outward flow reaction hydro turbine if the speed increase wheel tended hit.

Suitability

The inward flow reaction hydro turbine is quite suitable for medium to high speed and is best suitable for large output power producing units whereas the outward flow reaction hydro turbine is quite suitable for low or medium heads and small power production plants.

Application

The inward flow reaction hydro turbines are used for power production projects whereas the outward flow reaction hydro turbines are practically obsolete 

Last words 

So that our work on the difference between inward flow and outward flow reaction hydro turbine. If you still have a question do comment or ask directly via the contact form.

Frances Turbine vs Kaplan Turbine

Frances Turbine vs Kaplan Turbine : What are the some of the differences between the two? 

Frances Turbine is one of the most widely used hydro turbines due to its high efficiency and versatility in a wide range of head and flow conditions. 

Kaplan Turbine is typically used for low to medium head hydroelectric power generation, particularly in large scale plants.

Both Turbines are specifically designed to meet certain needs so lets find the difference between the Frances Turbine and Kaplan Turbine

To learn the difference between different turbine type read our article Difference Between Inward Flow and Outward Flow Reaction Hydro Turbine

Frances Turbine vs Kaplan Turbine

Type of Turbine

France Turbine is radially inward or mixed flow Turbine whereas Kaplan Turbine is partially axial floe

Position of shafts

In France Turbine position of shaft can be in vertical or horizontal whereas in Kaplan Turbine position of shaft is only in vertical direction.

Number of vanes

France Turbine has very large number of blades 16 to 24 whereas Kaplan Turbine has very small number of blades 3 to 8

Adjustment of runner vanes 

France Turbine Runner vanes are not adjustable whereas Kaplan Turbine Runner vanes are adjustable

Resistance to over come

France Turbine very large resistances have to be over come whereas Kaplan Turbine very less resistances have to be over come

Head

France Turbine medium head is required whereas Kaplan Turbine very low head is required

Flow Rate

France Turbine medium flow rate is required whereas Kaplan Turbine very large flow rate is required

Specific Speed

France Turbine 50 to 250 rpm whereas Kaplan Turbine 250 to 850 rpm 

Type of generator

France Turbine regular generator is required whereas Kaplan Turbine heavy duty generator is required

Conclusion on Frances turbine vs Kaplan Turbine

So that's was our comparison of Frances turbine vs Kaplan turbine. Hopefully this has added valuable knowledge and had cleared your concepts about difference between Frances turbine and Kaplan turbine.