K.Abhilash;(146H1A2402)

Amit Kumar;(146H1A0302)

NRI INSTITUE OF TECHNOLOGY

28-7-2016

INTRODUCTION Measurement of brake

horsepower is the most important measurements in the testing of an engine.

It involves the determination of the torque and the angular speed of the engine’s output shaft.

This torque measuring device is called dynamometers.

TYPES OF DYNAMOMETERSABSORPTION

DYNAMOMETERS-1. Prony Brake

Dynamometer ;2. Rope Brake

Dynamometer;Hdraulic Brake

dynamometer.

TRANSMISSION DYNAMOMETERS -

1. Epicyclic-train Dynamometer ;

2. Belt Transmission Dynamometer ;

3. Torsion Dynamometer.

ABSORPTION DYNAMOMETER This dynamometer measure and absorb the

power out put of the engine to which they are coupled.

The power absorbed is usually dissipated as heat by some means.

Examples of such dynamometers are – 1.Prony brake dynamometer. 2.Rope brake dynamometer. 3.Hydraulic dynamometer.

PRONY BRAKE DYNAMOMETERIt works on the principle of

converting power into heat by dry friction.

In this method of measuring horsepower is to attempt to stop the engine by means of a brake on the flywheel and measure the weight which an arm attached to the brake will support, as it tries to rotate with the flywheel.

ROPE BRAKE DYNAMOMETERIt consists of a number of turns of

rope wound around the rotating drum attached to the output shaft. One side of rope is connected to a spring balance and the other to a loading device.

The power is absorbed in friction between the rope and the drum. The drum therefore require cooling.

Although,It is not very accurate because of changes in the friction coefficient of the rope with temperature.

Power (bp) = π DN (W − S)where, D is the brake drum diameter,W is the weight of the load andS is the spring balance reading.

HYDRAULIC DYNAMOMETERIt works on the principle of

dissipating the power in fluid friction rather than in dry friction.

It consists of an inner rotating member or impeller coupled to the out put shaft of engine. This impeller rotates in a casing filled with fluid.

The heat developed due to dissipation of power is carried away by a continuous supply of working fluid, usually water.

The output can be controlled by regulating the sluice gates which can be moved in and out to partial or wholly obstructive flow of water between impeller and the casing.

TRANSMISSION DYNAMOMETERSIn power transmission dynamometers the

power is transmitted to the load coupled to the engine after it is indicated on some type of scale.

These are also called torque meters.They are mainly- 1.Epi-cyclic train dynamometer. 2.belt transmission dynamometer. 3.torsion dynamometer.

EPI-CYCLIC TRAIN DYNAMOMETER• it consists of a simple epicyclic train of gears,

i.e. a spur gear.• The spur gear is keyed to the engine shaft

and rotates in anticlockwise direction. • The annular gear is also keyed to the

driving shaft and rotates in clockwise direction.

• The pinion or the intermediate gear meshes with both the spur and annular gears. The pinion revolves freely on a lever.

• A weight w is placed at the smaller end of the lever in order to keep it in position.

• The tangential effort P exerted by the spur gear on the pinion and the tangential reaction of the annular gear on the pinion are equal.

.

For equilibrium of the lever, taking moments about the fulcrum F, 2P × a = W.L or P = W.L /2a

R = Pitch circle radius of the spur gear in metres, and

N = Speed of the engine shaft in r.p.m. ∴ Torque transmitted, T = P.R And power transmitted

BELT TRANSMISSION DYNAMOMETER

• When the belt is transmitting power from one pulley to another, the tangential effort on the driven pulley is equal to the difference between the tensions in the tight and slack sides of the belt.

• A belt dynamometer is introduced to measure directly the difference between the tensions of the belt,while it is turning.

TORSION DYNAMOMETERA torsion dynamometer is used for measuring large

powers particularly the power transmitted along the propeller shaft of a turbine or motor vessel.

A little consideration will show that when the power is being transmitted, then the driving end of the shaft twists through a small angle relative to the driven end of the shaft. The amount of twist depends upon many factors such as

torque acting on the shaft (T) length of the shaft (l) diameter of the shaft (D) modulus of rigidity (C) of the material of the shaft.

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THANK YOU Mr.M.venkanna Babu

Sir.

Respected faculties.

My fellow Nri-tians.