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Ng Eng Chung

on 16 December 2012

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Transcript of IMPACT OF JET

Open-Ended Test IMPACT OF JET OBJECTIVE CONCLUSION To determine the reaction force produced by the impact of jet of water of variety type of target vanes.
To experimentally determine the force required to keep a target at a datum level while it is subjected to the impact of water jet.
The experimentally measured force is compare with the theoretical calculated force A jet of water is produced when water is fed to a vertical pipe terminating in a tapered nozzle. The jet will impinge on a vane, of different shapes. Vanes usually used are flat plate, inclined plate, curved plate and hemispherical cup THEORY OF THE EXPERIMENT 1. First, the top plate of the transparent cylinder was taken off. Then, the diameter of the nozzle was measured. The flat lat was assembled to the lever that carries the jockey weight.

2.The top plate and the cylinder was assembled to the apparatus. After that, the supply pipe from the hydraulic bench was connected to the inlet pipe of the apparatus.

3.The apparatus was first leveled and the lever was set to a balance position (as indicated by a tally supported from it). This action was completed by placing the jockey weight at its zero position, and then, the knurled nut above the spring was adjusted.

4.Any force generated by impact of the jet on the vane was measured by moving the jockey weight along the lever until the tally shows that it has been restored to its original balanced position.

5.Nominal weight was placed on the lever first (initial weight=10g) and (incremental weight = 20g). Then, the water was admitted through the bench supply valve.

6.The lever was displaced by the force on the vane, which it was then restored to its balanced position by sliding the jockey weight along the lever. Then,the opening at the base of the hydraulic bench was covered.

7.The volume of water and the time was recorded to determine the flow rate. The weight on the lever also recorded.

8.The procedure (step1-7) was repeated for 120'' curved cup and hemispherical cup PROCEDURE Results Group Member NG ENG CHUNG






AF110242 Equation used to determine the force of jet impact (Fy) is given as:

Fy = Q ( Vy1 - Vy2 cos ) ,
Vy1 = initial velocity
Vy2 = final velocity (after impingement)
V= Q/A FLAT PLATE Equation of Flat Plate 120" Plate Equation of the 120'' Plate velocity after impingement Hemispherical Plate velocity after impingement EQUIPMENT

Hydraulic bench

Jet impact apparatus

Stop watch

Diameter of nozzle = 10 mm
Gravity acceleration, g = 9.81 ms– 2

From analysis, slope of the graph as in theory is given by: Given: ANALYSIS Flat Plate 120'' Plate Hemispherical Plate Theoretically Comparisons Several factors that had influenced the result of the experiment.
When velocity is high, the flow rate of the water will getting higher.
When the weight of load is high, the distance between the flat plates, 120 curved plate and hemispherical plate will be getting closer and thus the rate of the water flow will be increase. Discussion From the result, the forces generated by the nozzles to withstand the weight are 0.53N, 0.36N, 0.46N respectively. We assumed that the hemispherical cup (0.46N) should be has flower force produced because it has smaller area to withstand the forces produced by nozzle. Gradient of theory is increased follow by flat plate, 120°plate and hemispherical cup. It is same with the slope of experiment graph.

From the results, we assumed the errors occurred during the experiment. Then, some of precautions should be taken, for example :
a)Avoid shaking the water bench, so that the water level is set to a balanced position.
b)Adjust the adjusting nut above the spring correctly, make sure the nut is clean and in fine condition.
c)Prevent the zero error or systematic error during the experiment i.e make sure the weight at correct position.

With the measurement taken, it can lower to the minimum error and get accurate reading, to avoid the great differences of gradient of slope value. However, in this experiment we have success to prove that when the greater surface area of vane plate, the larger the forces that can withstand by the plate.

As the 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.
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. Theory Fy GENERAL EQUATION Flate Plate Vy1 = Q/A
Vy2 = 0 , due to the plate is flat, and so striking force splitting into zero velocity when the water striking on it. 120'' Plate Vy1 = Q/A

Where, from analysis

Hemispherical Plate Vy1 = Q/A

Where from analysis THANK YOU ! =D
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