Impact of a Jet

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  • Topic: Mass, Velocity, Mass flow rate
  • Pages : 9 (2030 words )
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  • Published : April 21, 2013
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Impact Of a Jet

Introduction:

Over the years, engineers have found many ways to utilize the force that can be imparted by a jet of fluid on a surface diverting the flow. For example, the pelt on wheel has been used to make flour. Further more, the impulse turbine is still used in the first and sometimes in the second stages of steam turbine. Firemen make use of the kinetic energy stored in a jet to deliver water above the level in the nozzle to extinguish fires in high-rise buildings. Fluid jets are also used in industry for cutting metals and debarring. Many other applications of fluid jets can be cited which reveals their technological importance. This experiment aims at assessing the different forces exerted by the same water jet on a variety of geometrical different plates. The results obtained experimentally are to be compared with the ones inferred from theory through utilizing the applicable versions of the Bernoulli and momentum equations.

Objectives:
i.To measure the force produced by a jet on flat and curved surfaces. ii.To compare the experimental results with the theoretically calculated values

Procedure:

1.Stand the apparatus on the hydraulic bench, with the drainpipe immediately above the hole leading to the weighing tank, see figure 4. Connect the bench supply hose to the inlet pipe on the apparatus, using a hose-clip to secure the connection.

2.Fit the flat plate to the apparatus. If the cup is fitted, remove it by undoing the retaining screw and lifting it out, complete with the loose cover plate. Take care not to drop the cup in the plastic cylinder.

3.Fit the cover plate over the stem of the flat plate and hold it in position below the beam. Screw in the retaining screw and tighten it.

4.Set the weigh-beam to its datum position. First set the jockey weight on the beam so that the datum groove is at zero on the scale, figure 5. Turn the adjusting nut, above the spring, until the grooves on the tally are in line with the top plate as shown in figure 6. This indicates the datum position to which the beam must be returned, during the experiment, to measure the force produced by the jet.

5.Switch on the bench pump and open the bench supply valve to admit water to the apparatus. Check that the drainpipe is over the hole leading to the weighing tank.

6.Fully open the supply valve and slide the jockey weight along the beam until the tally returns to record the reading on the scale corresponding to the groove on the jockey weight. Measure the flow rate by limiting the collection of 8Kg of water in the bench-weighing bank.

7.Move the jockey weight inwards by 10 to 15cm and reduce the flow rate until the beam is approximately level. Set the beam to exactly the correct position (as indicated by the tally) by moving the jockey weight, and record the scale reading. Measure the flow rate.

8.Repeat step 6 until you have about 6 sets of readings over the range flow. For the last set, the jockey should be set at about 10cm from the zero position. At the lower flow rates you can reduce the mass of water collected in the weighing tank to 8Kg.

9.Switch off the bench pump and fit the hemispherical cup to the apparatus using the method in steps 2 and 3. Repeat step 4 to check the datum setting. 10.Repeat steps 5 to 9, but this time move the jockey in steps of about 25cm and take the last set of readings at about 20cm.

11.Switch of the bench pump and record the mass m of the jockey weight, the diameter d of the nozzle, and the distance s of the vanes from the outlet of the nozzle.

Data and Results:

Table 1: Results for Flat Plate

Water
Mass,
Mw
(KgTime,
t
(S)Distance,
y
(m)Mass Flow,
m
(Kg/s)Velocity,
u
(m/s)
Initial
Velocity,
uo
(m/s)
Momentum,
muo
(N)Force
on vane,
F
(N)
240.560.6642.86546.47545.782342125.89
240.560.6742.86546.47545.782342126.29
240.560.64...
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