Dynamometer
- 1. DYNAMOMETER Mohammed Rajpurwala – 150050119540 Sai Rao – 150050119541
- 2. CONTENT 1. INTRODUCTION 2. TYPES OF DYNAMOMETER 3. ABSORPTION DYNAMOMETER • PRONY BRAKE DYNAMOMETER • ROPE BRAKE DYNAMOMETER • HYDRAULIC DYNAMOMETER 4. TRANSMISSION DYNAMOMETER • BELT TRANSMISSION DYNAMOMETER • EPICYCLIC TRAIN DYNAMOMETER • TORSION DYNAMOMETER • BAVIS-GIBSON FLASH LIGHT TORSION DYNAMOMETER
- 3. INTRODUCTION Defination: Dynamometer is a device which is used to measure the frictional resistance. By know ing frictional resistance we can determine the torque transmitted and hence the power of the engine.
- 4. Types of dynamometers: 1)Absorption dynamometer: Prony brake dynamometer Rope brake dynamometer Hydraulic dynamometer 2) Transmission dynamometer: Belt transmission dynamometer Epicyclic dynamometer Torsion dynamometer
- 5. Absorption dynamometers: • This dynamometers measure and absorb the power output of the engine to which they are coupled, the power absorbed is usually dissipated as heat by some means. • Examples such dynamometers are: 1. Prony brake dynamometer 2. Rope brake dynamometer 3. Hydraulic dynamometer
- 6. Prony brake dynamometer • A simplest form of an Absorption type Dynamometer is a Prony Brake Dynamometer . It consists of Two wooden blocks around a Pulley fixed to the shaft of an engine , whose power is required to be measured . The blocks are clamped by means of Two Bolts and Nuts . A Helical Spring is provided between the nut and the upper block to adjust the Pressure on the Pulley to Control its Speed . The upper block has a long lever attached to it and carries a weight W at its outer end . A Counter Weight is placed at the other end of the lever which balances the Brake when Unloaded . Two stops S1 and S2 are provided to limit the motion of the Lever .
- 7. -In Prony Brake Dynamometer , when the Brake is to be put in operation , the long end of the lever is loaded with suitable weights W and the nuts are tightened until the engine shaft runs at a constant speed and the lever is in Horizontal Position . Under these conditions , the moment due to the weight W must balance the moment of the Frictional Resistance between the Blocks and Pulleys . Work done per Minute = T * 2πN N-m Brake Power of the Engine = B.P. = ( Work done per minute ) / ( 60 ) = (T * 2πN / 60 ) = ( W * L * 2πN / 60 ) Watts
- 8. Rope brake dynamometer: • It is another form of Absorption type Dynamometer which is most commonly used for measuring the Brake Power of the Engine . It consists of one , two or more ropes wound around the flywheel or rim of a pulley fixed rigidly to the shaft of an engine . The upper end of the ropes is attached to a spring balance while the lower end of the ropes is kept in position by applying a dead weight . Brake Power of the Engine = B.P. = ( Work done per minute ) / ( 60 ) = ( W – S ) * π * ( D + d ) * N / 60 Watts If the Diameter of the Rope (d) is neglected , then Brake Power of the Engine, B.P. = ( W – S ) * ( πDN/60 ) Watts
- 9. Hydraulic dynamometer: • It 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 output 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.
- 11. Transmission Dynamometers : • Power-measuring dynamometers may be transmission dynamometers or absorption dynamometers. The former utilize devices that measure torque, in terms of the elastic twist of the shaft or of a special torquemeter inserted between sections of the shaft. The torque is produced by the useful load that the prime mover, motor, or machine is carrying.
- 12. 1) Belt Transmission Dynamometer : • It consists of endless or continuous belt run over the driving pulley. • The driving pulley is rigidly fixed to the shaft of an engine whose power is to be transmitted. • The intermediate pulleys rotates on a pin fixed to a lever having a fulcrum at the midpoint of the two pulley centers. • A balancing weight is provided in the lever to initially keep it in equilibrium. • The weight of suspended mass at one end of the lever balances the difference in tensions of tight and slack sides of the belt. • power of engine P = ( T1 – T2 ) * ( πDN/60 )
- 14. 2) Epicyclic Train Dynamometer : • Epicyclic train dynamometer which measures power while it is being transmitted from driving to the driven shaft. • It consist of simple epicyclic gear train. • The pinion is free to rotate on a pin fixed to the lever arm. • The lever is pivoted about common axis of the driving and driven shaft. • When the dynamometer is in operation, two tangential forces acts at the end of pinion. Torque Transmitted by Engine T = F * R = ( W * L / 2 * a ) * R Power Transmitted by Engine P = T * ω = ( W * L / 2 * a ) * R * ( 2πN/60 )
- 16. 3) Torsion Dynamometer : • When power is transmitted along a shaft, the driving end twists through a small angle relative to the driven end. • Torque transmitted is directly proportional to the angle of twist. • Therefore, a torsion dynamometer works on the principle of angle of twist. • Torsion dynamometers can measures large powers as in case of power transmitted along the angle of twist in radians is given by, By Torsion Equation , T/J =C*Ɵ / l Power Transmitted P = T * ( 2πN/60 ) Watts
- 17. 4) Bevis-Gibson flash light torsion dynamometer : • It consists of two discs A and B fixed on shaft at convenient distance. • A radial narrow slit is made in each of the two discs. • Behind disc A powerful electric lamp is fixed on the bearing of shaft. • To the right of the disc B an eye-piece is fitted on shaft bearing. • When torque or power is transmitted through the shaft, it twists so that disc B lags behind the disc A.