What Is Fluid Coupling? Features, uses, application

Fluid dynamics principles are seen in different latest devices and inventions. It is commonly seen in modern toilets to rocket propulsion. Fluid dynamics is an important factor for products used in engineering. The fluid coupling is an important factor, like other engineering concepts. In this post, we will cover details for fluid coupling and related factors.

What Is Fluid Coupling?

A fluid coupling, also called a hydraulic coupling, is a hydrodynamic device used for the transmission of rotational mechanical power.

It is used for automobile transmission systems for the replacement of mechanical clutches.
It is used in marine and industrial machine drives and for variable speed applications, and controlled start-up without shock loading of the power transmission system.
Hydrokinetic drives are different from hydrostatic drives, like hydraulic pump and motor mixtures.
Fluid coupling is a torque-transmitting couplings that employ hydraulic oil. They are different from torque converters, where input torque equals output torque.
Fluid coupling is more effective than torque converters and comes with 2 to 4 percent losses.
Fluid coupling is used for providing acceleration control, torque limiting control, load sharing control, and speed control.
Constant power was also applied, and the power in load decreased with speed. The difference between input power and output power is power dissipated as losses in coupling.

Fluid coupling components

Fluid coupling comes with three main components and hydraulic fluid.

Housing, also called a shell, comes with fluid and turbines.
It has two turbines, one configured with an input shaft that is called a pump or primary wheel input turbine.
second connected with the output shaft, that is, the turbine, the output turbine, and the secondary wheel
driving turbine It, also called a pump, is rotated with a prime mover that is an internal combustion engine.
Impeller motion affects both outward linear and rotational motion for fluid.
Hydraulic fluid is directed with a pump that is designed to apply forces low in the direction of the output turbine.
The difference in angular velocity of the input phase and output phase causes a net force on the output turbine, resulting in torque. As a result, rotate the direction of the pump.
Fluid motion is toroidal; it moves in one direction along the paths that can be seen on the surface of the torus.
If a difference exists between input and output angular velocity, motion comes with a poloidal component.
If input and output stages come with identical angular velocity and do not have net centripetal forces, the motion of fluid is in a circular direction and the same axis as the axis of rotation. There is no flow of fluid from one turbine to the other.

Fluid Coupling Specifications

It comes with two bladed wheels that are connected in a hydraulic way.
power transmits without wear and has high input speed, providing mechanical transmission
Its fluid in the working state is a connection component.
Fluid quantity can change during machine starting time for controlling startup features and power transmission.
hydrodynamic devices provide longer working life through dampening torsional vibration and driveline shock.
fill level variations control-driven machine speed. Provide protection for the drive and machine from being affected by torque spikes.
Slip value is about 100 percent, providing motor stability.

Fluid Couplings Working

Before the use of fluid coupling, the vehicle comes with a manual gearbox. The clutch, which makes a connection with the engine and transmission, is operated by the driver for manual transmission.
A vehicle having a manual gearbox can stall if stopped without a clutch.
For accurate working of fluid coupling, fluid dynamics and hydrokinetics are used as the base for fluid coupling features.
It is different from hydrostatic systems like hydraulic pumps. fluid coupling made with two wheels having blades that face one another but do not have a connection.
The impeller that is one wheel connected with the power supply. The impeller provides power to the turbine. That is then delivered to transmission.
The turbine that is output rotates slowly as compared to the impeller, also called input. Energy is transferred through the system with the output spinning as a result of the fluid flowing in.
The oil-filled assembly comes with wheels that hold it in position.

Fluid Coupling Working Principle

The impeller starts the centrifugal pump oil static runner when the motor moves to running speed.
conical impeller baffle diffused oil transmission, generating slow torque increment, providing motor to move fast with running speed

When oil is pumped into the working location, the oil continuously circulates between the impeller and the runner, making a flow area as the helical spring makes a ring.
When the transmitted torque is at the resisting torque value, the runner rotates and accelerates the operating load.
Time needed for getting full speed is based on load inertia, resisting torque, and torque transmitted to the fluid coupling.

Fluid Coupling Types

There are two types of fluid coupling explained here.

Constant Filling

Constant filling has oil filling in fixed and variable filling, also called variable speed. Here, the oil quantity in the working area is different. Running to control the value of slip between the impeller and runner provides speed regulation.

Variable Filling

Variable filling fluid couplings also provide delatching of the machine from the drive and are used in conveyor drives for controlling torque applied at the time of acceleration and provide simple load balancing with external controls.

Advantage

It provides vibration- and noiseless power transmission and smooth operation in hard conditions.
It starts the motor unloaded with overload protection.
It can control the starting speed without the shock loading of the transmission system.
Maximum torque set with varying oil filled in the casing.
It is used for both vertical and horizontal circuits.

Disadvantage

It has a slip that makes a certain difference between the speed of the runner and the impeller.
It does not produce torque when driving the shaft and the driven shaft are moving with annular velocity.
In case of stalling conditions, coupling in dissipated heat causes damage.

Conclusion

The fluid coupling is important for using a transmission to rotate mechanical power for vehicles and industrial machines without a direct mechanical connection. the use of hydraulic fluid for transferring torque between input and output shafts that provides smooth and easy overload protection and shock absorption

FAQs

What is the working of a fluid coupling?

fluid coupling The other name is hydraulic coupling, which is a hydrodynamic process that transfers rotational force from one shaft to another with transmission fluid. It is used for vehicle transmission systems and power transmission in industries.

What Is the Difference Between Fluid Coupling & a Torque Converter?

Fluid coupling is a two-component drive that does not provide torque multiplication, and a torque converter comes with one more component, a stator, that varies drive features at times of high slippage, generating high output torque.

Why is thermal protection used on constant fill fluid couplings?

Thermal protection for this coupling provides safety for the fluid coupling and also for the driver and drive machine. A fusible plug is common thermal protection. If the temperature of the fluid in the coupling increases, the fusible metal in the plug melts, and the fluid in the coupling drains out, stopping power transmission and causing an overload on the prime mover.

What is the efficiency of fluid coupling?

Fluid coupling works with rotation that is reduced at the time of starting of the centrifugal clutch, which is at 100 rpm at the start. So low changes of centrifugal clutch with fluid coupling can provide high efficiency of about 82 to 85 percent.

What Are The Limitations Of Fluid Coupling?

Fluid coupling is not as effective as mechanical gears, which results in high power usage. It is not good for applications that need high-speed ranges. The higher cost for fluid coupling than for a mechanical gear system affects its uses.

What Are The Signs Of Coupling Failure?

Each damaged coupling shows some signs of failure. Some failures are easy to see, and others need proper working. Some external signs that show coupling damages are noises, like screeching, squealing, or chattering.

What Is The Purpose Of The Coupling?

A coupling is a mechanical component that joins two shafts with each other for transmitting power from drive to drive and absorbing mounting errors.