YABA COLLEGE OF TECHNOLOGY YABA, LAGOS

INDUSTRIAL MAINTENANCE ENGINEERING DEPARTMENT

TERM PAPER ON FLUID COUPLING AND TORQUE CONVERTER

(INDUSTRIAL HYDRAULICS AND PNEUMATICS 1)(I M E 302)

BY

Submitted to:ENGR. UDO

SEPTEMBER 2009

DEDICATION

Thank you Almighty God for seeing me through the completion of this work.

ACKNOWLEDGEMENT

Word would fail me in acknowledging the assistance and the inspiration got from many

people who contributed in one way or the other to the success of this work.

RECTIFIER BUILDER ASSOCIATION MEMBERS, Mr.Taiwo Abe, Mr. J. Ayokunle

Elegbeleye, and Mr. J. Adedayo Ogunlaja

To these few people mentioned, I am indebted to work harder to show forth many

things I learn through them.

I would not forget the encouragement got from some of my friends and course mates.

Thanks.

TABLE OF CONTENT

TITLE PAGE

CERTIFICATION

DEDICATION

ACKNOWLEDGEMENT

TABLE OF CONTENT

CHAPTER 1 FLUID COUPLING

1.1 Definition

1.2 Basic construction of Fluid Coupling

1.3 Operation and layout of a Fluid Coupling

1.4 Purpose of fluid coupling

1.5 Benefits and Limitation of the use of fluid coupling

1.6 Performance Characteristic Graphs for a Fluid Coupling

CHAPTER 2 TORQUE CONVERTER

2.1 Purpose of Torque Converter

2.2 Benefits and Limitation of the use of Torque Converter

2.3 Operation of Multistate of Torque Converter

2.4 Power Flow in Stages

2.5 Significance and Meaning of Torque Ratio and Converter Efficiency

REFERENCES

CHAPTER ONE FLUID COUPLING

1.0 Definition

A fluid coupling is a hydrodynamic device used to transmit rotating mechanical power or device

that transfers power through a fluid between its inputs and outputs. A fluid coupling basically

consists of two fans in a sealed, oil-filled housing. The input fan churns the oil, and the churning

oil in turn twirls the output fan. Such a coupling allows some speed difference between its input

and output shafts.

1.1 Basic Construction Of Fluid Coupling

The internal appearance of a fluid coupling has traditionally been likened to the two valves of a

grapefruit, each facing the other with the pulp scooped out and the cell divider s left intact.

Translated into technical language, the fluid coupling may be described as consisting of two

toroidally grooved discs facing one another with a small clearance between them.

Radial blades are formed across the grooves to divide them into curved cells. This blade also

supports the hollow semicircular cores for guide rings, which reduce turbulence in the coupling.

The guide rings are offset within their torodal cavities so as to equalize flow area in the cells. One

disc is mounted from the engine flywheel via a tore’s cover but connects t the input shaft of the

gear box and is termed the turbine. Fluid coupling are either produced from aluminum die casting

or as in later practice fabricated from steel pressing.

1.2 Principles of Operation and layout

There are three essential parts to a fluid coupling: the driving (input) section known as the

impeller the driven (output) section known as the runner and the casing which bolts to the

impeller enclosing the runner providing an oil tight reservoir. Both impeller and runner

each represents half of a hollow torus with flat radial vanes. At the inner circumference a

conical baffle is attached to the impeller and a flat baffle is attached to the runner. These

components comprise the working circuit.

 

The operation of the fluid coupling requires mechanical input energy, normally provided

by a standard NEMA B electric motor which is connected to the impeller and casing. The

runner, which has no mechanical connection with the impeller, is directly connected to

the driven load. A variety of mechanical connections; couplings, sheaves, and hollow shaft

mountings, are available to provide the mounting configuration best suited to the

application. Finally the fluid coupling must be initially charged by removing the fill

(fusible) plug and adding the recommended amount of oil based on the required torque.

Starting

Standard NEMA B motors are recommended when using fluid couplings and will start

virtually unloaded. Since the motor is mechanically connected to the impeller and casing,

the low inertia of these components and the oil are the only loads imposed. As the electric

motor accelerates to running speed, the impeller begins to centrifugally pump oil to the

stationary runner. Transmission of oil is diffused by the conical impeller baffle, producing

a gradual increase in torque, allowing the motor to accelerate rapidly to full running

speed. When all the oil is pumped into the working circuit, continuous circulation of oil will

occur between the impeller and runner forming a flow path like a helical spring formed in

a ring.

 

As soon as the transmitted torque reaches the value of the resisting torque, the runner

starts rotating and accelerates the driven load. The time required to reach full speed is

dependent on the inertia of the driven load, the resistive torque, and the torque being

transmitted by the fluid coupling.

Running

The operation of a fluid coupling is based on the hydrokinetic

principles and requires that the output speed be less than the

input. This difference in speed is called slip. Further this

principle provides that the output torque is equivalent to the

input torque, since windage and oil circulation losses are

negligible. Therefore, efficiency equals 100% minus the

percent of slip.

 

At full running speed fluid couplings will normally slip between 1% and 4%. The oil

circulation between the impeller and runner has formed a vortex at the outside

circumference of the working circuit and is no longer deflected by the conical baffle.

Overload – Stall

Should the load torque increase, the slip will increase, which causes the runner to drop in

speed. The vortex of oil circulating between the impeller and runner will expand to

provide additional torque. The extent to which this vortex can expand is limited by the flat

baffle on the runner. Consequently fluid couplings provide inherent overload protection.

 

If the increase in torque causes the oil in the working circuit to expand to the point of

contacting the baffle, the coupling will stall and slip will be 100%. This continuous high

slip generates heat and the oil temperature will rise unless the overload is removed.

When the temperature rises to the temperature limit of the fusible plug, the core of the

plug will melt, release oil from the coupling and effectively disconnect power to the output

shaft. To prevent the loss of oil the use of a proximity cutout switch or thermal trip plug

and limit switch is recommended.

 

Coupling guards must be designed to permit air circulation for cooling and to protect

when oil is released from fusible plug due to overload.

1.3 Characteristic Graph Of Fluid Coupling

Fluid coupling has centrifugal characteristics during starting, thus enabling no load start-up of prime mover, which is of great importance.

The slipping characteristics of fluid coupling provides a wide range of choice of power transmission characteristics which also result in speed variation, smooth & controlled acceleration, clutching and declutching operations and other characteristics of load limiting shock & peak load absorption and

dampening etc. By varying the quantity of oil filled in the fluid coupling, the normal torque transmitting capacity can be varied. The maximum torque of the fluid coupling can also be set to a pre-determined safe value by adjusting the oil filling.

The fluid coupling has the same characteristics in both directions of rotation.

Scoop Control Variable Speed Couplings:

These coupling have a sliding scoop tube which enters the coupling rotating casing through central clearance. The oil quantity level in the coupling can be varied which in operation by changing the position of the scoop tube which determines the oil level in the coupling. This change of oil level shifts the torque characteristic of the coupling thus enabling step less speed control .See the characteristic curve shown below.

1.4 Purpose of fluid Coupling

The purpose of using fluid coupling are listed below according to their application,

In vehicle transmission system it is generally used to secure the following:

Absence of direct mechanical contact between the driving and driven members minimizes the

transmission of shock and torsional vibration between the engine and the drive line.

No positive disengagement or engagement of drive allows a smoother starting characteristic this

being particularly advantageous when restarting up a steep hill

Protect against harmful laboring of the engine at low speeds, since the fluid coupling will merely

slip and allow the engine to increase speed when overloaded.

In Aviation transmission system it is used in the engine's exhaust gases and then, using three

fluid couplings and gearing, converted low torque high-speed turbine rotation to low-speed, high-

torque output to drive the propeller.

1.6 Benefit Of Fluid Coupling

Economical soft starts, with smooth acceleration. Shock- load protection

From underground & overland belt conveyors to crusher and mixing applications, equipment professionals are constantly seeking better technology to protect critical production systems against the effects of

damaging shock loads. And when it comes to eliminating sudden/ jarring starts, or preventing system failure/ deterioration due to overloads, nothing outperforms the system- saving capability of fluid couplings.

Unmatched, cushioned soft start flexibility, at an economical price point. Smooth acceleration.

Mechanical overload protection. NEW sizes 2760HF & 2870HF offer higher capacity at higher speeds. Increased starting torque available from standard NEMA B motors

with a fluid coupling. This is a benefit not offered by electronic soft start solutions.

Providing the softest, smoothest start will maximize the life of your system components.

As the smart alternative to expensive & complicated electronic solutions, fluid couplings allow precise adjustment of startup characteristics in the field, simply by changing the fluid fill level via the easy access fill & drain holes.

NEW Longer starting profiles and softer starts. For Sizes 1420HF & larger, adjustable metering

orifices regulate the passage of fluid from the delay fill chamber into the working circuit, further softening the start.

For sophisticated belt conveyors, consider Type HFDD. The extended delay fill chamber permits initial start factor as low as 40% of the full load torque, dramatically reducing shock & stretch to the belt at startup.

Use of the extended delay fill chamber (HFDD) is recommended for conveyors subjected to

unloaded starts, those with concave sections, those with low inertia, or those with any

combination of these conditions. Modest fill in the working circuit at startup minimizes belt liftoff,

and assures unloaded & low inertia conveyors are not rapidly accelerated. Protection - regardless

of load condition.

Torque applied to a belt conveyor starts at zero (point C) and gradually increases in magnitude as

the coupling impeller accelerates to point D. When the output torque of the fluid coupling exceeds

the breakaway starting torque of the belt conveyor (point D), the conveyor gradually & smoothly

accelerates to full speed.

 Prevent jamming overloads that can cut short the life of your system. 

True Torque™ fluid couplings safeguard your system against mechanical overload. Simple,

straightforward protection when instantaneous jams are encountered.

Two fusible plugs per coupling are a standard feature, and prevent damage to the driven

equipment and the motor.

The proximity sensor cutout switch accessory, an extra charge option, prevents fluid

discharge, and provides ability to reset cutouts in case of frequent overloads.

Another optional accessory, the easily replaceable thermal trip plug, is used in conjunction

with a trip switch, also preventing fluid discharge.

Increase the starting torque available for hard starting conditions.  

Over-sizing of electric motors for the purpose of increased starting torque can be avoided with a properly selected fluid coupling. A fluid coupling allows the motor to accelerate independently to full speed, the driven load has been isolated by the fluid coupling. Once the motor is started, the fluid coupling gradually introduces the driven load. If the starting load is high, the breakdown torque (Point B) of the energized motor is now available for starting purposes.  

Easily balance the load sharing between multiple drives. 

Adjust the fill so each motor carries an equal burden.

 

1.6.1 Fluid Coupling Efficiency

At operating speed and full load, fluid couplings remain highly efficient. Since all the mechanical

components, i.e. shaft seals, bearings, runner, and impeller, are operating at virtually the same

speed, there are few mechanical losses and the output torque is essentially equal to the input

torque.

With percentage differences normally ranging between 1 and 4%, full-load running efficiencies

between 99% and 96% are possible. AC motor power does not need to be increased to take

advantage of fluid coupling benefits (see Fig. 3). Slow start up times and the ability to operate in

the 100% "slip" mode also make fluid couplings useful on conveyors incorporating two or more

drives on the head-shaft and secondary pulleys. By sequence starting motors with 3 to 4 second

delay, both loaded and empty starting times can be further increased, minimizing line voltage

drop problems caused by excessive inrush current. Such configurations can also reduce excessive

belt tension, which prolongs belt life. A simple method for determining fluid coupling efficiency

includes a comparison of output speed vs. AC motor speed.

Fluid couplings also provide a simple method to load balance two or more drives operating on the

same headshaft or secondary pulley. For instance, once full-load power on each drive is recorded,

the working fluid can be increased or decreased slightly ensuring each drive delivers its share of

the power.

CHAPTER TWO TORQUE CONVERTER

2.0 Definition

A torque converter is a modified form of fluid coupling that is used to transfer rotating power from a prime mover, such as an internal combustion engine or electric motor, to a rotating driven load. Like a basic fluid coupling, the torque converter normally takes the place of a mechanical clutch, allowing the load to be separated from the power source. As a more advanced form of fluid coupling however, a torque converter is able to multiply torque when there is a substantial difference between input and output rotational speed, thus providing the equivalent of a reduction gear.

A device in the power train consisting of three or more rotating members, which transmits power through a fluid. It provides varying drive ratios ; with sped reduction, it increases torque.

2.2 Limitation Of Torque Converter

One of the most common torque converter failures is overheating. If there are continually high levels of slippage this may exceed the ability of the converter to dissipate the heat. If continuous levels of high heat are present it may cause damage to the elastomer seals that help to keep all of the fluids within the converter. The result is that the unit will leak and then stop functioning as a result of too little or no fluid within the converter.

Another common issue with a torque converter is the stator clutch breaking. When there is a sudden application of power it can shock the stator clutch with a heavy load and will actually cause it to break. When the stator clutch breaks it will allow the stator to rotate the pump in the wrong direction and there will be no transmission of power. When the stator clutch breaks the vehicle will not be able to move on its own.

In addition to the stator clutch breaking it can also seize, or simply stop working. The way that this works is that the inside and outside components of the clutch actually get locked together, which keeps the stator from rotating during the coupling phase. Seizure of this nature usually occurs when there has been sudden and severe loading. Usually a seized stator clutch will result in very little efficiency during coupling, and the fuel consumption will increase as a result.

Yet another common issue with a torque converter is blade deformation or even fragmentation of the blades. These issues can occur with the blades when there is sudden or excessive heating of

the converter, at which time the pump and turbine blades can become deformed. Often times, the blades will actually pull away from the hubs or rings or can simply break into fragments. This can often cause irreparable damage to the torque converter.

Ballooning is another common problem with torque converters. This problem is caused when there is an excessive load placed on the converter or when there is a sudden load. Ballooning may also occur when the converter is used at a very high RPM. Ballooning can even cause the converter housing to expand or even rupture, causing the converter to cease working.

All of these problems can occur when you least expect it, which is why you need to understand how your converter works and how you can avoid failure. Most failures can be avoided, it simply comes with knowledge and experience. Be sure to learn as much as you can about your specific converter.

2.3 Operation of Multistate of Torque Converter

A good example of multiplying force may be found in the fulcrum and lever principle. To make the explanation of torque multiplication simpler, consider the torque converter a “floating” fulcrum. To do this it will be necessary to review the function of the fulcrum and lever to see how it applies to the torque converter.

Fulcrum lever principle

The fulcrum and lever principle illustrates how a force can be multiplied. In Figure 7, Diagram “A”,

“x” and “y” are in balance because the fulcrum “f” is equally distant from “x” and “y”, and “x” is

equal to “y”. In Diagram “B”, Figure 7, the increased load at “x” is balanced by positioning the

fulcrum closer to “x” and farther from “y”.

In Diagrams “C” and “D”, Figure 8, two alternate ways to lift the load at “x”, are illustrated. The

force at “y” may be multiplied (Diagram C), or the distance from the fulcrum the force is applied

can be increased, while reducing the force (Diagram D).

2.31 Torque and speed

Figure 9 illustrates one to one speed ratio at a one to one ratio at “B”. Note, that the output

speed RPM at “B” will be the same as the input speed at “A”. Whatever torque or twisting effort is

put into “A” will be transmitted through the output “B”. If 20 ft lbs of torque go into “A”, 20 ft lbs

of torque will come out of “B”, or if there is 30 ft lbs input, there will be 30 ft lbs output, or in

other words, the torque ratio is one to one ….. Suppose it becomes necessary to double the lifting

force, this can be done in two ways. Increase the power source or relocate the fulcrum. The

fulcrum is relocated by moving a large gear into position (Figure 10).

For every two revolutions of “A”, gear “B” will make one revolution. If the input twisting effort is 20 ft lbs, the output torque will be 40 ft lbs. To make the fluid coupling perform as a torque multiplier, it is necessary only to add a reaction member, or fulcrum. The stator becomes the reaction member, by placing a stator (reaction member – Figure 15) between the load and power source, a fulcrum is provided. A torque converter has at least three elements – impeller (driving member), turbine (driven member) and stator (reaction member).

2.32 Oil Flow Patterns

To assist us in understanding hydraulic torque multiplication, let us consider three terms. First,

Kinetic Energy: Energy opposed by oil in motion. Second, Rotary Flow: The Flow of oil around the

outer circumference in the converter. Third, Vortex Flow: The Flow of oil across the converter.

Third, Vortex Flow : The flow of oil across the converter.

(2) Kinetic energy

The multiplication of input torque results from the kinetic energy imparted to the oil by the pump

(impeller) plus the kinetic energy entering the pump from the stator. The more the turbine resists

turning, the greater the velocity of the vortex flow of oil circulating in the converter, and the

greater the torque multiplication. The less the turbine resists turning, the less the velocity of the

vortex flow of oil in the converter and the less the torque multiplication.

(3) Rotary and vortex flow

The instant the torque converter impeller, which is driven by the engine flywheel, starts rotating,

the oil spins around with it. This movement of oil is rotary flow (Figure 11). The converter turbine,

connected to the load, resists turning as the oil strikes its blades. Because of this resistance, and

because of the shape of the blades within the converter elements, the oil takes a second path of

travel cross-wise. This second path is called vortex flow (Figure 12). The greater the load

resistance transmitted by the turbine, the greater will be the vortex flow.

2.3.3 Principle of Operation

The torque converter provides varying drive ratios between the driving member (impeller) and

the driven member (turbine). This is accomplished by using curved vanes in both the driving and

driven member, and by using one or more extra members. The extra members act to reduce the

splashing effect mentioned before in paragraph 2b (4). Figure 13 shows the curvature of the vane

in the torque converter members.

2.4 Power Flow

The impeller (Figure 13 (1) is driven by the engine. The turbine (Figure 13 (3) is attached to the

converter output shaft. The stator (Figure 13 (2) is supported between the impeller and turbine

and can either be held from rotating by being mounted rigidly on a fixed support, or mounted in a

one way clutch which permits it to turn free when the driving and driven members are both

turning at about the same speed. The impeller is driven by the engine; the turbine, connected to

the output shaft rotating free (no mechanical connection to the impeller or stator); the stator is

positioned between the turbine and impeller and directs the flow of oil between the two units.

2.41 Action of the Torque converterThe vanes in the impeller are curved in one direction, and the vanes in the turbine are more

curved in the opposite direction. The curvature of these vanes is critical for they are designed to

develop high torque efficiency. To visualize the operation of the torque converter, it is important

to remember that the oil flows essentially in two directions (paragraph 2c (2) ; around the

converter in the direction of rotation (Figure 11), and around the torus shaped ring formed by the

impeller, turbine, and stator (Figure 12).

(2) When the impeller is turned by the engine, centrifugal force tries to throw the oil in the

impeller outward. However, the oil cannot be thrown outward in a straight line because of the

curvature of the impeller and vanes. Therefore, the oil is thrown against the vanes of the turbine

(Figure 14). The force with which oil is thrown against

the vanes of the turbine causes the turbine to turn in the same direction as the impeller.

(3) After the oil passes over the turbine vanes, it leaves the inner edge of these vanes, and

travels in a direction almost opposite to that in which the turbine is traveling (Figure 15).

(4) If nothing were done to change the direction of the oil flowing from the turbine, it would strike

the blades of the impeller on their leading surfaces and tend to stop the impeller. This would

cause the engine to work harder to keep the impeller turning. At this point the reaction member

becomes vital.

(5) The stator (reaction member – Figure 15 (2), has no mechanical connection to either the impeller or turbine. It fits in between the outlet of the turbine and the inlet of the impeller so all the oil has to pass through it when returning from the turbine to the impeller. The stator changes the direction of the oil flowing from the turbine so that it will go in the same direction as the impeller. Also, the openings between the stator blades speed up the flow of oil so that it re-enters the impeller in such a manner that less engine torque is required to drive the impeller (Figure 15).

(6) Actually, the change-over from one phase to the next phase of operation, as outlined above, is not sudden but gradual and is in accordance with the changing demands of the operation. When starting and accelerating, as the turbine speed nears the impeller speed, the changing pattern of oil flow eases the back pressure on the stator vanes. As a steady speed is reached on a level road the impeller and turbine speeds become nearly equal. This means that further changes in the pattern of oil flow will have taken place and will not contribute anything to the operation of the converter. So, there is a continuous circulation of oil through the three units of the torque converter. From the impeller, through the turbine, through the stator, and back to the impeller.

2.4.2 Variations In Torque Converters

While the foregoing description covers torque converters generally, some torque converters have more members (other than the impeller, turbine, and stator).(1) Three element torque converterThe three element torque converter found on many pieces of equipment will have either a fixed or a rotating stator (reaction member).(a) The fixed stator is mounted rigidly in the converter and will not turn.

(b) The stator that is mounted on a one-way clutch is able to turn in the same direction as the engine only (Figure 16).(c) The overrunning clutch used in a torque converter is generally a sprag-type. The sprags are somewhat like flattened rollers. The inner and outer races of the overrunning clutch are smooth. A series of sprags are positioned between the inner and outer races and are held in place by two springs put into the sprag notches . The outer race is stationary but the inner race is splined to the stator hub and therefore will turn with the stator. During steady running, the stator is not needed and as mentioned will rotate. The sprags have no effect on the forward rotation of the inner race. During acceleration the oil must change direction and the oil is thrown against the front faces of the stator vanes. This produces a backward thrust, or pressure on the stator vanes, which halts the stator and attempts to turn it backwards. As this happens, the sprags jam between the inner and outer races, thereby locking the inner race so that it cannot turn backward. The stator then becomes stationary so that its vanes can effectively change the direction of the oil flow.

2.4.3 Four element torque converter

(a) The four element torque converter contains a driving member, or impeller, a driven member or turbine, plus a primary stator and a secondary stator. Each of these stators is mounted on an overrunning type clutch . When the torque converter is first started, the impeller is rotation much faster than the turbine. The two stators are held stationary and they redirect the oil as it leaves the turbine. This is shown by the arrows in Figure 18. In other words, as the oil comes off the turbine vanes, it strikes the stationary stator vanes and has its direction changed. This enables I to enter the impeller in a direction that does not hinder the impeller rotation.

(b) The turbine speed increases until it nears the speed of the impeller. The oil leaving the turbine vanes gradually changes direction until it begins to strike the back faces of the primary stator vanes. This will cause the primary stator to begin to rotate. The secondary stator still is stationary and will continue to change the direction of oil.

(c) When the speed of the turbine is near equal to that of the impeller the oil will now strike the back of the secondary stator vanes. Now the secondary stator also begins to rotate. Neither stator enters into the action now, and the converter acts as a fluid coupling.

2.4.4 Five element torque converter

(a) The five element torque converter is similar to the four element converter, the main difference is the addition of a secondary impeller. The secondary impeller is not used during heavy load or hard acceleration operation. It is mounted on an overrunning clutch (Figure 17) which allows it to spin faster than the primary impeller, however, the secondary impeller locks when it attempts to rotate slower than the primary impeller. This locking forces both impellers to turn at the same speed.

(b) The force that causes the secondary impeller to spin faster than the primary impeller comes from the oil striking the back faces of its vanes.h. Torque Multiplication FactorsSince torque converters vary considerably in design, the amount of torque multiplication they can achieve also varies with the practical limit being 5:1. The torque multiplications would normally depend on the size of the converter, the number of elements and the piece of equipment the torque converter was designed for.

Efficiency

Transmission efficiency of any hydraulic transmission using torque converter is comparable to any electrical transmission. The efficiency of hydro-mechanical transmission is about 10 % higher. The comparative saving in fuel costs will be substantial especially in high horsepower super-fast train locomotive

Efficiency of the hydraulic coupling is defined as the ratio of power output to power input.

η=power output = t) t) power input p) p)

EFFICIENCY TORQUE

Efficiency of Torque converter η= power output P(O) = (T(t) +T(V)) w (t) Power input P (I) T(p) w(p)

)

Variable Description Metric Units English Units

P(in) Power applied to input shaft Watts Horsepower

P(out) Power applied to the output shaft

Watts Horsepower

P(loss) Power loss (coulomb friction and viscous dissipation)

Watts Horsepower

w (in) Rotational speed of the input shaft

Rad/s RPM

w (out) Rotational speed of the output shaft

Rad/s RPM

T(in) Input torque Newton-meters ft-lbs

T(out) Output torque Newton-meters ft-lbs

η(m) Mechanical Efficiency --- --

 The torque converter receives power from the engine.

P(in) = T(in) * W(in)

η (m) = P(out)/P(in).

This is a function of fluid viscosity, fin design in the turbine and impeller units, T(out), T(in) and other variables. Torque converters run at efficiencies anywhere from 0-95% depending on w(in), w(out), and T(in) and T(out). For example, when a car is stopped at a traffic light, the engine still applies power to the input shaft, but the brakes and transmission prevent the output shaft from rotating. Since P(out) = T(out) * w(out), and w(out) equals zero, P(out) equals zero. Therefore, the efficiency equals zero.

When a car is traveling at highway speeds, the turbine is rotating nearly as fast as the impeller. Recalling that they are attached to the output shaft and the input shaft respectfully, then P(in) » P(out) and therefore efficiency is rather high.

Graph Variables:

Torque Ratio = T(out)/T(in)

Speed Ratio = out)/in)

Efficiency = P(out)/P(in)

REFERENCE

TechOne automatic transmissions By Jack Erjavec

 Mechanical conveyors: selection and operation By Muhammad E. Fayed, Thomas S. Skocir

Light and heavy vehicle technology By Malcolm James Nunney

http://www.reference.com/browse/wiki/Hydrodynamics

http://www.automedia.com/CarCare-Cleaning-Engine/C-35

http://en.wikipedia.org/wiki/Automobile

http://www.torque-converter.net/category/uncategorized