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Fluid Coupling
UME 502 Automobile Engineering
Dr. Devender Kumar & Dr. Atul Sharma
Mechanical Engineering Department
Fluid Coupling
• Fluid coupling is also
known as a hydraulic
coupling.
• It is a hydrodynamic
device which is used to
transfer rotational power
from one shaft to another
by the use of a fluid.
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Fluid Coupling
• It is used in automotive
transmission system, marine
propulsion system and in
industries for power
transmission.
• It is used as an alternative
for the mechanical clutch.
Fluid Coupling Torque Converter
Fluid Coupling
• Although quite similar in
construction, a torque
converter can multiply the
engine torque whereas a
fluid coupling cannot do
this.
• The torque converter and
the fluid coupling both were
invented by Dr. Hermann
Fottinger.
Dr. Hermann Fottinger
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Components
Fluid Coupling
3 Housing cover
• A typical Fluid Coupling
consists of three primary
components:
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or 1
1. A driving Impeller or Pump
a pump.
2. A driven Turbine.
3. and a Housing cover.
Components
Fluid Coupling
Impeller
(housing)
or
• The impeller has (Shell)
numerous straight blades
that rotate as a unit with
the housing.
• The impeller turns at
Gearbox input
engine speed, acting like a Crankshaft
shaft
pump to start the
transmission oil
circulating within the fluid
coupling shell. Turbine
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Working Principle
Fluid Coupling
• The working principle of
fluid coupling can be easily
explained by taking two fans
in which one is connected
to the power supply and
other is not.
• When the power switch is
ON, the air from the first fan
starts to blow towards the
second fan (which is not
connected to the power
source).
Working Principle
Fluid Coupling
• Initially when the first fan is
blowing at lower speed, it is not
able to drive the second fan.
• But as the speed of the
powered fan increases, the
speed of air striking the blades
of second fan also increases
and it starts to rotate. After
some time the second fan
acquires almost the same
speed as that of the powered
fan.
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Working Principle
Fluid Coupling
Turbine
• On the same principle the Impeller
fluid coupling works.
• The impeller wheel act as
first fan which is
connected to the power
source and the turbine act
like the second fan.
Working Principle
Fluid Coupling
• The fluid after passing
through the turbine
blades again return to the
impeller.
• Since there is no rigid
contact between the
pump and the turbine,
the torque is transmitted
without any wear and
tear.
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Types of oil flow
Fluid Coupling
• Rotary flow describes the
centrifugal force applied
to the fluid as the
converter rotates on its
axis.
• Vortex flow is the circular
flow that occurs as the oil
is forced from the
impeller to the turbine
and then back to the
impeller.
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Types of oil flow
Fluid Coupling
• If a toy pinwheel were
held at arm’s length and
swung in a large circle, air
movement at the outer
circle would produce
rotary flow, while the
small circles cut by the
pinwheel’s propeller
vanes would produce
vortex flow.
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Turbulence in Fluid Flow
Fluid Coupling
• When the impeller is
turning at speeds much
greater than the turbine,
a great deal of oil
turbulence occurs.
• Fast moving oil exits the
impeller blades, striking
the turbine blades with
considerable force.
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Turbulence in Fluid Flow
Fluid Coupling
• Thereafter it has a
tendency to be thrust
back toward the center of
both impeller and turbine.
• To control this fluid thrust
and the turbulence that
results, a split guide ring is
located in both the
impeller and turbine
sections of the coupling.
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Turbulence in Fluid Flow
Fluid Coupling
• The guide ring suppresses
the turbulence, and
thereby allowing more
efficient operation.
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Advantages
Fluid Coupling
• Absence of direct
mechanical contact.
• No positive
disengagement or
engagement of the drive.
• Protection against the
harmful loading of the
engine at low speeds.
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Thanks for
Watching
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