Introduction Impact Jet 3v2u18

INTRODUCTION: Water turbines are widely used throughout the world to generate power. In the type of water turbine referred to as a Pelton† wheel, one or more water jets are directed tangentially on to vanes or buckets that are fastened to the rim of the turbine disc. The impact of the water on the vanes generates a torque on the wheel, causing it to rotate and to develop power. Although the concept is essentially simple, such turbines can generate considerable output at high efficiency. Powers in excess of 100 MW, and hydraulic efficiencies greater than 95%, are not uncommon. It may be noted that the Pelton wheel is best suited to conditions where the available head of water is great, and the flow rate is comparatively small. For example, with a head of 100 m and a flow rate of 1 m3/s, a Pelton wheel running at some 250 rev/min could be used to develop about 900 kW. The same water power would be available if the head were only 10 m and the flow were 10m3/s, but a different type of turbine would then be needed. To predict the output of a Pelton wheel, and to determine its optimum rotational speed, we need to understand how the deflection of the jet generates a force on the buckets, and how the force is related to the rate of momentum flow in the jet. In this experiment, we measure the force generated by a jet of water striking a flat plate or a hemispherical cup, and compare the results with the computed momentum flow rate in the jet. The Impact of a Jet experiment shows students the force produced by a jet of water as it strikes a flat plate or hemispherical cup. They can then compare this to the momentum flow rate in the jet. To extend the range of investigations, the 120DegreeConical Plate and 180-Degree Angled Plate are available separately To perform experiments, level the apparatus and zero the weigh beam assembly. Set the flow from the hydraulic bench to maximum, and measure the jet force. Then reduce the flow from the hydraulic bench in several increments. At each increment ,record the force of the jet on the plate and the flow rate. Then repeat the experiments for different test plates. All test plates are all easily interchangeable, taking only a few seconds and needing no tools. Compare the results to those calculated from theory, working out graphs of rate of delivery of momentum against force on the plate

OBJECTIVE: The objectives of this experiment are: 1. To measure the force produced by a jet on flat and curved surfaces. 2. To compare the experimental results with the theoretically calculated values i.To compare the forces obtained from the experiment and the actual force using theoretical formula. ii. To understand correctly how a turbine (a Pelton wheel for example) works, students need to understand how jet deflection produces a force on turbine vanes. iii. To understand how this force affects the rate of momentum flow in the jet

EXPERIMENTAL PROCEDURE: 1.The water valve is closed and pump is off. 2. The top plate was removed. The diameter of the nozzle was measured and recorded. 3. The flat target was placed (screwed) on the rod attached to the weight pan. 4. The top plate was placed back and the knurled screws were tightened. 5. The apparatus was leveled by adjusting the stands. 6. The level gauge was adjusted to a point at the white line on the side of the weight pan. It was tightened. This was considered as balance position. 7. Some mass was placed on the weight pan. The mass was recorded. The balance position was offset. 8. The pump was switched on. 9. The flow rate was increased by opening slowly the water valve until the level gauge points at the white line on the side of the weight pan. The balanced position was achieved. 10. The flow rate was measured and recorded. 11. More mass was added and step 9 and 10 were repeated. 5 different values of mass were taken. 12. The valve was closed and the pump was turned off.

DATA AND CALCULATION: Impact of jet Jet (nozzle) diameter : d = 8 mm = 0.008 m Jet Area : A Jet = 5.027 x 10-5 m3 Gravitational acceleration : g = 9.81 ms-2 Mass density of water : ρ = 1000 kgm-3

CONCLUSION: As a conclusion, the experiment that have been carried out were successful, even though the data collected are a little bit difference compared to the theoretical value. The difference between the theoretical value and the actual value may mainly due to human and servicing factors such as parallax error. This error occur during observer captured the value of the water level. Besides that, error may occur during adjusting the level gauge to point at the white line on the side of the weight pan. Other than that, it also maybe because of the water valve. This error may occur because the water valve was not completely close during collecting the water. This may affect the time taken for the water to be collected. There are a lot of possibilities for the experiment will having an error. Therefore, the recommendation to overcome the error is ensure that the position of the observer’s eye must be 90° perpendicular to the reading or the position. Then, ensure that the apparatus functioning perfectly in order to get an accurate result.

REFERENCE: 1. http://www.cee.mtu.edu/~dwatkins/ce3600_labs/impact_of_jet.pdf 2. http://www.eng.ucy.ac.cy/EFM/Manual/HM%2015008/HM15008E-ln.pdf 3.http://staff.fit.ac.cy/eng.fm/classes/amee202/Fluids%20Lab%20Impact%20of%20a%2 0Jet.pdf