EXPERIMENT NO:1

IMPACT OF JET ON VANES

OBJECTIVE:

To determine the Co-efficient of impact of Jet on vanes combination by comparing the actual force with the theoretical force for stationary vanes of different shapes, Viz., Hemi – spherical , flat plate and 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.

EXPERIMENTAL SET UP:

The apparatus consists of a pipe with a nozzle at one end and a regulating valve at the other end, a vane with an arrangement for measuring the force of jet coming on it ( either a lever arm with an hanger for weights at one end or a platform for directly putting weights on it). The vane and nozzle are enclosed in a transparent container such that the jet strikes the vane centrally the container has an outlet leading to a discharge measurement tank.

SPECIFICATIONS:

Vane shape: Flat, Hemispherical & Inclined

Jet dia : 4, 5 & 6 mm

Measurement: Flow rate of water by direct reading using Rotameter in lpm

Jet : Jet force by direct reading from digital Force indicator in Newton

Type : Re – circulating with sump & jet Chamber madeof Stainless steel.

Jet chamber: Fixed with toughened glass windows with leak proof rubber gasket.

PROCEDURE:

  1. Fix the nozzle and the vane of required shape in position and set the force indicator to show zero.
  2. Close the 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.
  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.

PRECAUTIONS:

  1. The discharge should be changed gradually so as not imbalance the vane suddenly.
  2. Before taking the reading ensure that the vane is perfectly and freely balanced

Sl.no / Diameter
of the jet
‘d’ mm / Type of vane / Water flow rate Q lpm / Actual force fa kg / Theoretical force ft kg / Co-efficient of impact jet on vane: CI
4 / Flat
Hemispherical
Inclined
θ = 600
5 / Flat
Hemispherical
Inclined
θ = 600
6 / Flat
Hemispherical
Inclined
θ = 600

CALCULATIONS:

Diameter of jets d = 4,5 and 6 mm

Acceleration due to gravity g = 9.81m/Sec2

Density of water = 1000 Kg/m3

1. Discharge (Qd)):

Q

Qd = ------m3/sec

60 x 1000

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):

Flat vane:

ρ A V2

Ff = ------Kg

g

inclined vane:

ρAV2

Fi= ------x Sin θ Kg

g

where,

θ = 600

Hemispherical or Curved Vane:

2ρ A V2

Fh = ------Kg

g

4) Co- efficient of impact:

Fa

Ci = ------

Ft

Where,

Fa = actual force, obtained directly from scale

RESULT: Co-efficient of impact Jet of Hemi – spherical vane ______

Co-efficient of impact Jet of flat vane______

Co-efficient of impact Jet of inclined vane_____

JET ON INCLINED VANE

JET ON FLAT VANE

JET ON CURVED VANE

FAQ’sfor LAB

1. Define the term Impact of Jet?

2. Write the formula for force exerted by a jet of water on a stationary & moving plate.

3. Write the formula for force exerted by a jet of water on a curved plate at center .

4. What is an impulse momentum equation?

5. Define the terms momentum, moment & impulse?

6. What is an impulse turbine?

REFERENCES

Reference Books

1.Fluid Mechanics and Fluid Power Engineering by D.S. Kumar, Kotaria & Sons.

2. Fluid Mechanics and Machinery by D. Rama Durgaiah, New Age International.

3. Hydraulic Machines by Banga & Sharma, Khanna Publishers.

4.Fluid Mechanics and Hydraluic Machines by R.K.Bansal ,Lakshmi Publications