IMPACT OF JET ON VANES

OBJECT:To determine the Co-efficient of impact Jet - Vane combination

by comparing the actual force with the theoretical force for stationary vanes of different shapes, Viz., Hemi-spherical, Flat plate, Inclined Plate.

THEORY:When the jet of water is directed to hit the vane of any

particular shape, the force is exerted on it by the fluid in the opposite direction. The amount of force exerted depends on the diameter of jet, shape of 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. The following are the theoretical formulae for different shapes of vane, based on flow rate.

FORMULAE FOR DIFFERENT VANES

1) Hemi - spherical

Ft

= (2 A V2 / g)

2) Flat Plate

Ft

= ( A V2 / g)

3) Inclined - Plate

Ft

= ( A V2 / g) x Sin

= 600

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Where,‘ g ‘ = 9.81 meters / sec2

‘ A ‘ = Area of Jet in m2

‘ ‘ = Density of water = 1000 Kg/m3

‘ V ‘ = Velocity of Jet in m/sec

‘ ‘ = Angle the deflected jet makes with the axis of

the striking jet, in degree = 600

‘ Ft ‘ = The theoretical force acting parallel to the

direction of jet.

‘ Fa ‘ = Actual force developed as indicated by the

analog force indicator.

DESCRIPTION:

It is a closed circuit water re-circulation systems consisting of sump tank,

monoblock pump set, Jet / Vane Chamber, Rota meter for flow rate

measurement, direct reading digital force indicator. The water is drawn from

the sump tank by monoblock centrifugal pump and delivers it vertically to

the nozzle through rotameter.

The rotameter is a direct indicating flow rate instrument which gives the

discharge in LPM (litres per minute) which is determined by the top -

position of the float. The flow control valve is also provided for controlling

the water into the nozzle. The water is issued out of nozzle as jet. The jet is

made to strike the vane, the force of which is tranfered directly to the force

indicator. The force is read in Kgf. The provision is made to change the vane

of different shapes.

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SPECIFICATIONS:

* Vane shapes : Flat, Hemispherical & Inclined.

* Jet Dia : 4, 5 & 7 mm.

* Measurement : Flow rate of water by direct

Reading Rotameter

: Jet force by direct reading from

digital force indicator

* Type : Re-circulating with sump & jet

Chamber made of stainless

steel.

* Jet Chamber : Fixed with toughened glass

windows with leak proof rubber

gasket.

OPERATING INSTRUCTIONS:

1. Fix the nozzle and the vane of required shape in position and set the

force indicator to show zero

2. Close the front transparent cover tightly.

3. Keep the delivery valve closed and switch ON the pump.

4. Open the delivery valve and adjust the flow rate of water as read on

the Rota meter.

5. Observe the force as indicated on force indicator.

6. Note down the diameter of jet, shape of vane, flow rate, force and

tabulate the results.

3

7. Switch OFF the pump after the experiment is over and close the

delivery valve.

8. Repeat the experiment at different flow rates with same jet and vane.

9. Change the vane and carryout the experiment with different flow

rates.

TABULAR COLUMN:

SL.NO

DIAMETER OF THE JET

‘D’mm

TYPE OF VANE

WATER FLOW RATE

‘Q’Lpm

ACTUAL FORCE

‘Fa’Kg

1. 4

FLAT

INCLINED = 60

HEMI-SPHERE

2. 5

FLAT

INCLINED = 60

HEMI-SPHERE

LIST OF FORMULAE

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DATA:

* Diameter of the Jets ‘d‘ = 4, 5 & 7mm

* Accleration due to Gravity ‘g‘ = 9.81 m/Sec2

* Density of water ‘w‘ = 1000 Kg/m3

1. Discharge (Q) :

Q Q

D = -------------- m3 / Sec

60 x 1000

Where,

60 & 1000 are conversion factors to m3 / Sec

Q = Rota meter reading in LPM 2. Velocity (V):

QD

V = ----- m/sec A

Where,

A = Area of jet considered,

= d2 / 4 m2

3. Theoretical force (Ft ) :

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a) For Flat Vane:

A V2 F

T1 = ----------- Kg

g

b) For Flat Inclined Vane: A V2

FT2

= ------------x Sin Kg

g Where,

= 600

c) For Hemispherical or Curved Vane:

A V2 FT3 = ---------------- Kg

g

4) Co-efficient of Impact: F

A

CI = --------

FT

Where,

F

A = Actual force, obtained directly from Scale

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TABLE OF CALCULATION:

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Tabular Column(Sample Calculation)

MODELJET DIA

LPM, Q

ACTUAL FORCE in kg, FA

Qd AREA, AVelocity,

VFt1 Ft2 Ft3

Co-Efficien

t of Impact,

CI

HEMI - SPHERICAL

7.00

26.5 0.680 4.42E-04 3.85E-05 11.48

 

1.034 0.65825.0 0.590 4.17E-04 3.85E-05 10.83 0.920 0.64120.0 0.390 3.33E-04 3.85E-05 8.67 0.589 0.66215.0 0.190 2.50E-04 3.85E-05 6.50 0.331 0.574

FLAT - PLATE 7.00

27.5 0.600 4.58E-04 3.85E-05 11.92 0.557

 

1.07825.0 0.450 4.17E-04 3.85E-05 10.83 0.460 0.97820.0 0.280 3.33E-04 3.85E-05 8.67 0.294 0.95115.0 0.150 2.50E-04 3.85E-05 6.50 0.166 0.906

INCLINED -PLATE

7.00

26.5 0.400 4.42E-04 3.85E-05 11.48

 

0.448

 

0.89325.0 0.380 4.17E-04 3.85E-05 10.83 0.398 0.95420.0 0.250 3.33E-04 3.85E-05 8.67 0.255 0.98015.0 0.130 2.50E-04 3.85E-05 6.50 0.143 0.906

HEMI - SPHERICAL

5.00

18.5 0.540 3.08E-04 1.96E-05 15.71

 

0.988 0.54715.0 0.360 2.50E-04 1.96E-05 12.74 0.649 0.55410.0 0.150 1.67E-04 1.96E-05 8.49 0.289 0.5205.0 0.030 8.33E-05 1.96E-05 4.25 0.072 0.416

FLAT - PLATE 5.00

19.0 0.490 3.17E-04 1.96E-05 16.14 0.521

 

0.94115.0 0.310 2.50E-04 1.96E-05 12.74 0.325 0.95510.0 0.100 1.67E-04 1.96E-05 8.49 0.144 0.6935.0 0.030 8.33E-05 1.96E-05 4.25 0.036 0.832

INCLINED -PLATE

5.00

19.0 0.400 3.17E-04 1.96E-05 16.14

 

0.451

 

0.88715.0 0.240 2.50E-04 1.96E-05 12.74 0.281 0.85410.0 0.080 1.67E-04 1.96E-05 8.49 0.125 0.6405.0 0.030 8.33E-05 1.96E-05 4.25 0.031 0.960

HEMI - SPHERICAL

4.00

13.5 0.400 2.25E-04 1.26E-05 17.91

 

0.822 0.48710.0 0.330 1.67E-04 1.26E-05 13.27 0.451 0.7328.0 0.190 1.33E-04 1.26E-05 10.62 0.289 0.6585.0 0.100 8.33E-05 1.26E-05 6.63 0.113 0.887

FLAT - PLATE 4.00

14.0 0.350 2.33E-04 1.26E-05 18.58 0.442

 

0.79210.0 0.120 1.67E-04 1.26E-05 13.27 0.225 0.5327.5 0.070 1.25E-04 1.26E-05 9.95 0.127 0.5525.0 0.040 8.33E-05 1.26E-05 6.63 0.056 0.710

INCLINED -PLATE

4.00

14.0 0.290 2.33E-04 1.26E-05 18.58

 

0.383

 

0.75810.0 0.090 1.67E-04 1.26E-05 13.27 0.195 0.4618.0 0.050 1.33E-04 1.26E-05 10.62 0.125 0.4005.0 0.020 8.33E-05 1.26E-05 6.63 0.049 0.410

GUIDANCE OF CALCULATION:

DATA:

* Diameter of the Jets ‘d‘ = 4, 5 & 7mm

* Acceleration due to Gravity ‘g‘ = 9.81 m/sec2

* Density of water ‘w‘ = 1000 Kg/m3

1. Discharge (Q):

Q Q

D = --------------

60 x 1000

15= -------------- = 2.50 x 10-4 m3 / sec 60 x 1000

Where,

60 & 1000 are conversion factors

to m3 / Sec

Q = Rota meter reading in LPM = 15 LPM

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2. Velocity (V):

QD

V = ----- m/sec A

2.50 x 10-4

-------------- = 12.74 m/sec1.16 x 10-5

Where,

A = Area of jet considered,

= d2 / 4 m2

= x 0.0052 / 4 = 1.16 x 10-5 m2

3. Theoretical force (Ft):

a) For Flat Vane: A V2

FT1

= ----------- Kg

g 1000 x 1.16 x 10-5 x 12.742

= ---------------------------------- 9.81

= 0.325 kg

b) For Flat Inclined Vane: A V2

FT2

= ------------x Sin Kg

g Where,

= 600

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c) For Hemispherical or Curved Vane:

AV2 FT3 = ---------------- Kg

g

4) Co-efficient of Impact :

FA 0.31

CI = -------- = -------- = 0.955

FT

0.325

Where, FA

= Actual force, obtained directly from meter = 0.31 kg

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