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are sometimes differentiated on the basis of the type of inlet flow, whether the inlet velocity is in axial direction, radial direction or a combination of both. The
Francis turbine is a mixed hydraulic
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was required to convert the energy at low pressure heads, given that the quantity of water was large enough. It was easy to convert high pressure heads to power easily but difficult to do so for low
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on decreasing the specific speed or decreasing the pressure head, and finally shows the evolution from the
Francis hydraulic turbine to the Kaplan hydraulic turbine.
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The shaft of a
Francis turbine is usually vertical (in many of the early machines it was horizontal), whereas in a Kaplan turbine it is always vertical.
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A Kaplan turbine has fewer runner blades than a
Francis turbine because a Kaplan turbine's blades are twisted and cover a larger circumference.
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In a Kaplan turbine, the water flows in axially and out axially, while in a
Francis turbine it flows in radially and out axially.
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In the figure, it can be seen that the increase in specific speed (or decrease in head) have following consequences:
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A Francis turbine's specific speed is medium (60–300 RPM); a Kaplan turbine's specific speed is high (300–1000 RPM).
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Generally, the Kaplan turbine works on low pressure heads (H) and high flow rates (Q). This implies that the
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70:(the inlet velocity has Radial and tangential components) while the Kaplan turbine is an axial hydraulic
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155:: Flow velocity (the axial component in the case of axial machines, the radial in the case of radial).
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A Kaplan turbine has a smaller cross-section and has lower rotational speed than a
Francis turbine.
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Hence, these are the parameter changes that have to be incorporated in converting a
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at inlet increases, and hence allows a large amount of fluid to enter the turbine.
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with the plane of the machine (usually the nozzle angle or the guide blade angle).
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converts energy at high pressure heads which are not easily available and hence a
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component decreases as moving to the Kaplan turbine, and here in the figure, V
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The efficiency of a Kaplan turbine is higher than that of a
Francis turbine.
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component). The evolution consisted of the change in the inlet flow mainly.
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heads. Therefore, an evolution took place that converted the
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Three-dimensional losses and correlation in turbomachinery
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works on low specific speeds i.e., high pressure heads.
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General differences between
Francis and Kaplan turbines
125:: Relative velocity of the fluid after contact with
261:, while it is the radial one in all other runners.
235:The flow at the inlet, in the figure, to all the
257:However, the exit velocity is axial in Kaplan
294:Friction losses in a Kaplan turbine are less.
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116: : Tangential velocity of the fluid.
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187:functions is high, as specific speed (N
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254:decreases as the evolution proceeds.
50:, which generated power at even low
103:consists of the following vectors:
85:The image describes the changes in
74:(the inlet velocity has only axial
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430:S. K. Agrawal (1 February 2001).
247:) and tangential (Vw) directions.
433:Fluid Mechanics & Machinery
202:A reduction in inlet velocity V
436:. Tata McGraw-Hill Education.
400:Fundamentals of Turbomachinery
352:Fundamentals of Turbomachinery
1:
419:A Text book of Turbomachines
417:Govinde Gowda, M.S. (2011).
377:A Text book of Turbomachines
375:Govinde Gowda, M.S. (2011).
142:(absolute velocity), called
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138:: Tangential component of
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16:Evolution of water turbine
96:of a velocity triangle:
402:. Prentice Hall India.
398:Venkanna, B.K. (2011).
354:. Prentice Hall India.
350:Venkanna, B.K. (2011).
228:represents the axial (V
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478:Hydraulic engineering
243:, is in the radial (V
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25:Further information:
19:Further information:
239:, except the Kaplan
54:heads efficiently.
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87:velocity triangles
443:978-0-07-460005-4
409:978-81-203-3775-6
361:978-81-203-3775-6
321:Velocity triangle
101:velocity triangle
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94:Nomenclature
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462:Categories
392:References
99:A general
423:Davangere
381:Davangere
305:See also
241:impeller
76:velocity
63:Turbines
52:pressure
40:pressure
326:Turbine
237:runners
72:turbine
68:turbine
58:Changes
36:turbine
449:23 May
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259:runner
337:Notes
269:to a
127:rotor
451:2013
438:ISBN
404:ISBN
356:ISBN
209:The
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215:f1
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222:w
220:V
213:V
206:.
204:1
181:s
169:β
163:V
159:α
152:f
150:V
146:.
140:V
135:w
133:V
129:.
122:r
120:V
114:U
108:V
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