Impact of a Jet
Abstract The objective of this experiment is to measure the force generated by impact of the jet on vanes of various shapes like flat plate, conical cup and hemispherical cup. Besides that, the results from the experiment have to be compared with the theoretical calculations too.
1.0 Introduction Water turbines are widely used throughout the world to generate power. By allowing fluid under pressure to strike the vanes of a turbine wheel, mechanical work can be produced. Rotational motion is then produced by the force generated as the jet strikes the vanes. One way of producing mechanical work from fluid under pressure is to use the pressure to accelerate the fluid to a high velocity in a jet. The jet is directed on to the vanes of a turbine wheel, which is rotated by the force generated in the vanes due to the momentum change or impulse which takes place as the jet strikes the vanes. Water turbines working on this impulse principle have been constructed with outputs of the order of 100,000 kW and with efficiencies greater than 90%. In this experiment, the force generated by a jet of water as it strikes a flat plate, conical plate and hemispherical cup may be measured and compared with the momentum flow rate in the jet.
2.0 Experimental Design
2.1 Apparatus and Materials The jet impact apparatus Volumetric hydraulic bench/water 3 different shapes of vanes : Flat plate Conical cup Hemispherical cup Stopwatch
Figure 1. Arrangement of apparatus.
Procedure Starting with the flat plate, the apparatus is firstly leveled and the lever set to the balanced position (as indicated by the tally) with the jockey weight at its zero position. Water is admitted through the bench supply valve. The rate of flow is then increased to the maximum and the position of the jockey weight which restores the lever to the balanced position is noted, while the discharge is weighed in the weighing tank. A series of about four readings with roughly equally spaced
1.0 Introduction Water turbines are widely used throughout the world to generate power. By allowing fluid under pressure to strike the vanes of a turbine wheel, mechanical work can be produced. Rotational motion is then produced by the force generated as the jet strikes the vanes. One way of producing mechanical work from fluid under pressure is to use the pressure to accelerate the fluid to a high velocity in a jet. The jet is directed on to the vanes of a turbine wheel, which is rotated by the force generated in the vanes due to the momentum change or impulse which takes place as the jet strikes the vanes. Water turbines working on this impulse principle have been constructed with outputs of the order of 100,000 kW and with efficiencies greater than 90%. In this experiment, the force generated by a jet of water as it strikes a flat plate, conical plate and hemispherical cup may be measured and compared with the momentum flow rate in the jet.
2.0 Experimental Design
2.1 Apparatus and Materials The jet impact apparatus Volumetric hydraulic bench/water 3 different shapes of vanes : Flat plate Conical cup Hemispherical cup Stopwatch
Figure 1. Arrangement of apparatus.
Procedure Starting with the flat plate, the apparatus is firstly leveled and the lever set to the balanced position (as indicated by the tally) with the jockey weight at its zero position. Water is admitted through the bench supply valve. The rate of flow is then increased to the maximum and the position of the jockey weight which restores the lever to the balanced position is noted, while the discharge is weighed in the weighing tank. A series of about four readings with roughly equally spaced