INTRODUCTION
Water turbines are widely used throughout the world to generate power. By allowing fluid under pressure to shrike the vanes of a turbine wheel. Mechanical work can be produced rotational motion is the produced by the force generated as the jet strikes the vanes. One of the common types of water turbines is pelt on wheel. In this type of water turbine, one one or more water jets are directed tangentially on to a vanes or buckets that are fastened on 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. To predict the output of a pelt on wheel and to determine its optimum rotational speed, understanding on 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 are needed. This experiment aims at assessing the different forces extorted by the same water jet on a variety of geometrical different plates. Under this experiment, the force generated by a jet of water striking a deflector is measured.
ABSTRACT
This objective of this experiment is to study the jet forces impacting against stationary deflectors. The deflectors used in this experiment can be categorized into three geometries. Plate, hemisphere and cone deflectors are used for this experiment. Calculated force, F th and the percentage of error will be calculated in this e xperiment.
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OBJEKTIF
The designed to investigate jet forces impacting against stationary deflectors. The impact forces are produced by a water jet. The impact forces are measured using a lever mechanism and loading weights. The impact forces of the water jet are set via the Flow rate. Water is supplied either from the HM150 Basic flow module or by way of the laboratory Mains. The HM150 enables a closed water circuit to be Constructed.
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The unit essentially consists of:
Base Plate [7] Inlet connection [8] Drain connection [6] Perspex vessel [5] Nozzle [4] Deflector [3] Lever mechanism [2] Loading weights [1]
Various deflectors can be fitted at position [3]. Plate Hemisphere Slope Con
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Equipment that in use
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PROCEDURES PREPARING AND PERFORMING THE EXPERIMENT
Performance of Experiment:
Place the test set-up on the HM150 so that The drain routes the water into the channel.
Fit connecting hose between HM150 and Unit.
Open HM150 drain. Assemble deflector [1], (Plate, Hemisphere, Slope or Cone). Loosen the 3 screws [3] on the cover [4] and remove cover together with Lever mechanism. Fit appropriate deflector. Do not forget to tighten lock nut [2] on r od. Screw cover back onto vessel.
Use adjusting screw [5] to set pointer to zero (Zero notch [7]). When doing so, do not place Any loading weights on measurement system [8].
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Apply desired loading weight [8] 0.2N; 0.3N; 1N; 2N; 5N or combinations thereof.
Close main HM150 cock.
Switch on HM150 pump.
Carefully open main cock until pointer is on zero again.
Close HM150 drain cock.
Determine volumetric flow. This involves recording time t required to fill up the volumetric Tank of the HM150 from 20 to 30 liters.
Add loading weights and note down time t for 10 liters.
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Add loading weights and note down time for 10 liters
Switch off pump, open drain
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CALCULATION OF THEORETICAL JET FORCE The theoretical jet force is calculated from the principle of linear momentum The density of the water is = 1
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RESULTS OF MEASUREMENT The measured Values for deflectors with Plate, Hemisphere, Slope and Cone face are listed below. A tolerance of ±0 2. N was produced in the measurements by adding further small loading weights. 1. Measured Values for Plate Force F in (N) Measuring time in (s) 0.5 1.0 1.5 2.0 2.5 Measured volume :10 liter o 2. Measured Values for Hemisphere (180 deflection
Force F in (N) 0.5 1.0 1.5 2.0 2.5
Measuring time in (s)
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Flow rate in (m /s)
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Flow rate in (m /s)
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3. Measured Values for Cone (135 deflection ) Force F in (N) 0.5 1.0 1.5 2.0 2.5 Measured volume :10 liter
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Measuring time in (s)
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Flow rate in (m /s)
NOTA: Nozzle diameter = 8 mm 2
Cross Sectional Area of Nozzle = A = d / 4 3/s
Discharge, Q = Volume / Time (m ) Velocity, V = Q/A (m/s) 2
Gravity, g = the gravitational acceleration (9.81 m/s )
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RESULTS The velocity w1 of the jet from the nozzle is calculated from the volumetric flow and the cross-sectional area AD of the nozzle. THE VALUES FOR THE 3 BODIES ARE AS FOLLOWS
1. Plate 3
Flow rate , Q in (m /s)
Velocity , v in (m/s)
Calculated Force Fth in (N)
Measured force F in (N) 0.5 1.0 1.5 2.0 2.5
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2. Hemisphere (180 deflection) 3
Flow rate , Q in (m /s)
Velocity , v in (m/s)
Calculated Force Fth in (N)
Measured force F in (N) 0.5 1.0 1.5 2.0 2.5
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3. Cone (135 deflection ) 3
Flow rate , Q in (m /s)
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Velocity , v in (m/s)
Calculated Force Fth in (N)
Measured force F in (N) 0.5 1.0 1.5 2.0 2.5
EVALUATION OF EXPERIMENT Comparison of Theoretical and Measured Force
Calculation of the jet impact forces from the principle of linear momentum yields a good level of coincidence with the measured Values:
Example value in Plate Hemisphere Cone
Calculated force F th in N
Measured force F in N
Comparison of the Four Bodies
The 3 bodies used have a different geometry. This Is the reason, why the energy of the water jet is Used different by each body. How large the extent Of utilization is, can be seen, for example, on the Amount of water need to raise a body against the Force F:
Example value :0.5 N Plate Hemisphere Cone
It is obvious, that the Hemisphereuses the energy of the water jet best. The lowest extent of utilization is made with the slop.
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ltr
Flow rate /s
QUESTION Question 1 : Comparison of the four bodies with completing the table be low Loading (N)
Calculated Forces , Fth Plate
(N) Hemisphere
Cone
0.5 1.0 1.5 2.0 2.5
Questions 2: Plot the chart of forces (Measured (F) vs. calculated (Fth) for different deflectors.
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CONCLUSION
As a conclusion, the calculated force is correlated with the measured force. Broth of the forces will have directly proportional relation. The erotically, the calculated force should be the same at the measured force. Ho waver, this cannot be achieved experimentally due to the errors made during the experiment. Form this experiment, the flow rate for the hemisphere is found to be the lowest and thus require a longer time for the volumetric tank to raise from 20 to 30 liters.
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.
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