_____________________________________________________________Exp No: Date:

IMPACT OF A JET ON VANES

OBJECTIVE This experiment demonstrates the principle of conservation of linear momentum by measuring the force generated on a circular target plate due to an impinging water jet and comparing the measured data with the theoretical results.

To determine the coefficient of impact of jet-vane combination by comparing the actual force with the theoretical force for stationary vanes of given shapes- flat plate, circular plates, Inclined Plates.

Theory:

When the jet of water is directed to hit the vane of any particular shape, force is exerted in it by the fluid in the opposite direction. The amount of force exerted depends on the diameter of the jet, shape of the vane, fluid density and flow rate of water.

More importantly, it also depends on whether the vane is moving or stationary. In our present case, we are concerned about the force exerted on the stationary vanes. Following are the theoretical formulae for different shapes of vanes, based on the flow rate.

Flat Plate:Ft= ρ A V2 /g

Inclined plate:Ft= (ρ Q2 ) (1-cosθ)

Where g = 9.81 m/sec2

A = area of the jet in m2

ρ = Density of water in Kg/m3

v = velocity of the jet in m/secθ = Angle the deflected jet makes with the axis of striking jet , in degreesFt = The theoretical force acting parallel to the direction of the jet Fa = Actual Force developed as indicated by analogue force indicator

Equipment required:

As shown Fig , the water supply from the hydraulic bench is led to a vertical pipe, terminating in a tapered nozzle. This produces a water jet which impinges on a vane in the form of a flat plate. The nozzle and vane are contained in a transparent cylinder. An outlet at the base of the cylinder directs the flow to a catch-tank for measuring the flow rate.

The vane is attached to a pivoted beam which carries a jockey weight and is restrained by a light spring. The lever may be balanced (as indicated by the tally suspended from it) by placing the jockey weight at its zero position and adjusting the knurled knob above the spring. After this initial adjustment, the force generated by the impact of the jet on the vane may now be measured by moving the jockey weight along the lever until the tally shows that the lever has been restored to its original balanced position. The following quantities are required for data analysis:

Diameter of nozzle = ----------- mm Cross-sectional area of nozzle, A = ---------------- mm2

Mass of jockey weight, w = ------------- kg Maximum Jet force = 1 Kgf

Measurements:Flow rate of water by direct measurement of collecting tank water up to a volume in ‘t’sec.Pressure of the jet by pressure gaugeJet force by direct reading of the weights applied to balance the lever.Pump: ---------HP, Single-Phase, 230V, with starterType: Recirculation with sump & jet chamberJet Chamber: Fixed with toughened glass windows with leak proof rubber gaskets.

PROCEDURE 1. Balance the lever (as indicated by the tally) with the jockey weight at the zero position. 2. Admit water into the nozzle by adjusting the bench valve. Increase the flow rate to its maximum value; record the position of the jockey weight, and measure the flow rate using the catch-tank and the stopwatch 3. Record a total of ten different jockey positions (x) for gradually decreasing flow rates (Q), such that the jockey weight is moved to the left in roughly equal distance.

Sample Calculations:

Diameter of the jet d = -----------mVane Type - -------------------------- Discharge ‘Q’ = ----------------------m3/secActual Force ‘Fa’ = ---------------- kgf as calculated on weights

Calculations:Ft= (ρ Q2 ) (1-cosθ)

Where ρ = 1000 Kg/m3

Area = --------------m2

V = Q/A = ---------------------m/secg = 9.81 m/sec2

Ft = ----------kgfCoefficient of Impact = Fa/Ft

READINGS:

Dia of the jet in mm

Vane type Collecting tank time ( t sec)

Discharge in m3/sec

Pressure Head on Gauge P in kgf/cm2

Force Fa

CALCULATIONS:

Dia of the jet in mm

Vane type Discharge in m3/sec

Fa in kgf Force Fth Coefficient of ImpactFa/Ft

RESULTS & DISCUSSIONS:

Coefficient of Impact for the given jet – vane combination = -----------------------------

CONCLUSIONS: