Experiment Report
Name:
Ahmed Essam Mansour
Section: "1", Monday 2-5 pm
Title:
Impact of a Jet
Date:
October 9, 2006
Objectives:
• Study the relation between the force produced and the change of momentum when a jet strikes a vane.
• Compare between force exerted by a jet on a flat plate and on a hemispherical surface.
Theory:
In order to calculate the force caused by impact of a jet into a flat plate or curved vane, the change in momentum principle is applied;
Force = Rate of change in momentum
F = ρ Q ΔV
F = ρ Q (Vin – Vout)
Where;
F: the force exerted by the jet on the plate. ρ: the mass density of water (= 1000 kg/m3).
Q: volumetric rate of flow (m3/s).
ΔV: the change in velocity just after and before impact.
The volumetric flow rate in the equation 'Q' is calculated in the experiment by taking an amount of volume in a known period of time and then use;
Q=v/t
Vin is calculated in the experiment by first knowing the velocity at the nozzle and then using the motion equations.
Vnozzel is measured by know the diameter of the nozzle (dia = 10mm) and the volumetric flow rate
'Q' calculated previously,
Vnozzel = Q/ A
Then Vin is calculated by;
Vin2 = Vnozzel 2 – 2 g S
Where;
g: the gravitational acceleration (9.81 m/s2).
S: the distance between the jet and the plates (35mm)
Vout generally equals Vin cos θ, where θ represents the change in direction of the jet.
For the flat plat θ = 90◦, so that Vout = 0.0 .
For the Hemispherical cup θ = 180◦, so that Vout = -Vin
So the following relations are used for calculating the Predicted values of the force;
For the Flat plate:
F = ρ Q Vin
For the Hemi spherical cup:
F =2 ρ Q Vin
The measured force from the experiment is calculated by using the equilibrium of moment equation.
And the final relation for calculating the measured force is;
F = 4 * 9.81 * d
Where 'd' is the ruler reading for the jockey weight.
Apparatus: