Impact of Jet

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CVE3208 | Fluid Mechanics | Lab Report | 2012

Experiment 2 Impact of Jet

CVE3208 Fluid Mechanics

Ahmed Sujeeth I11009050 BCEGI - Semester 4

Lecturer: Dr. Khin Maung Win

19th November 2012

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Ahmed Sujeeth | I11009050 | BCEGI

CVE3208 | Fluid Mechanics | Lab Report | 2012 Title : Impact of Jet To investigate the validity of theoretical expressions for the force exerted by a jet on targets of various shapes. The impact of jet on a surface is a common day engineering application. One such example is the application of this principle on the Pelton wheel where power is generated due to the force of the jet which hits the bucket, which in turn rotates the wheel. Although it has been proven that there is loss of energy due to the impact and also loss in pipe flow, this method remains one of the most effective proven principles of generating power. To predict the maximum or minimum output of such engineering applications, the deflection and force of the jet on various geometrical variations must be determined. This experiment deals with verifying the expression of force due to impact of the jet on a variety of geometrical plates. By Newton’s second law of motion, F ma F ṁ changeinvelocity where Mass lowperunittimeṁ F ρav v vcosθ Fy ρQ v vcosθ where v For flat targets (90°) Fy ρQ v v cos 90 Q 0 Fy ρQ A ρQ Fy For 120° targets, Fy ρQ v v cos 120 Q Q0.5 Fy ρQ A A 3ρQ Fy 2A

Objective

:

Theory

:

ρav

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Ahmed Sujeeth | I11009050 | BCEGI

CVE3208 | Fluid Mechanics | Lab Report | 2012 For hemispherical 180° targets, Fy ρQ v vcos180 Fy Fy Theoretical force calculation Fy Mg The flow rate was measured using the apparatus discharge .The force of impact was determined by calculation using the above formulas and compared with the theoretical force. ρQ

Apparatus/ Equipment : Hydraulic bench F1-10, Impact of Jet Apparatus F1-16 Stopwatch Vernier caliper

Schematic Diagram

1) 2) 3) 4) 5) 6) 7) 8) 9)

Outlet hole Container top plate Knurled screws Air vent Weights Level gauge Spirit level Interchangeable target vane Interchangeable nozzle

10) Transparent tank

Procedure

:

Apparatus Functionality The apparatus should be positioned in the bed of the bench top channel and the inlet pipe (11) connected to the bench supply. The feet (12) are adjustable so that the apparatus can be leveled with the aid of the spirit level (7)

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Ahmed Sujeeth | I11009050 | BCEGI

CVE3208 | Fluid Mechanics | Lab Report | 2012 Water issues from the nozzle (9) and after striking the target plate (8) leaves through the outlet holes (1) in the base. An air vent (4) is provided so that the interior remains at atmospheric pressure. The vertical force exerted on the target plate is measured by adding weights to the weight pan (5) until the mark on the weight pan corresponds with the level gauge(6). The top plate (2) and the transparent tank (10) may be removed for the purpose of changing the target (8) plate or obtaining access to the nozzle (9) by undoing the knurled screws (3).

Experimental Procedure 1. The top plate and transparent casing were removed and the nozzle diameter was measured. The flat target was placed on the rod attached to the weight pan. The apparatus was reassembled and the inlet pipe connected to the bench with the apparatus in the open channel. The base of the apparatus was leveled with the top plate loosely assembled. The top plate was then screwed into position to datum on the spirit level. The level gauge was adjusted to suit the datum on the weight pan. A nominal mass was placed on the weight pan and water was allowed to flow by operating the control valve on the bench. The flow rate was then adjusted until the weight pan was adjacent to the level gauge. When testing for level, the weight pan was to be oscillated to minimize the effect of friction. The readings of volume and time were taken for flow rate. The mass on the...
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