PROF canal
bojwais
306b_-_power_point_finale..pptxExperiment 2
Group E
Introduction
Abstract:
Introduction
Apparatus Explanation:
The experiment is performed on an apparatus that consists of an aluminum alloy pipe that is connected to a diffuser to the suction eye of a centrifugal fan.
To measure the distribution of static pressure, 14 taps are connected to manometers placed along the pipe. (Tap number 14 reads the static pressure)
A Pitot tube is placed at the end of the pipe to measure stagnation pressure. (Tap number 19 reads the stagnation pressure)
The discharge opening down the stream can be adjusted from 0% to 100% open, also the speed of the fan can be adjusted too.
Motivation
Objective:
A Pitot tube and a manometer were used for in this experiment to measure the radial velocity profile of an air flow inside a pipe.
Using a Pitot tube and manometer to determine the velocity profile.
Determine boundary layer thickness along the wall of the pipe.
Investigate the axial pressure distribution along the pipe
Background
The no-slip condition states that the velocity of the fluid is equal to the velocity of the solid boundary which the fluid is in direct contact with a solid boundary.
As the fluid moves down stream the flow become fully developed where the velocity profile does not change with axial position, unlike with the fluid enters the pipe.
When the fluid enters the pipe it passes through the entrance region which is the distance between the fluid entrance till it becomes a fully developed flow.
The velocity profile has different shapes depending on whether the flow is laminar or turbulent.
Background
The speed of the flow can be calculated by the knowledge of the static and the stagnation pressure in a derived equation from the Bernoulli equation.
A Pitot tube is a device that measures the stagnation pressure of the flow.
The Manometer is used to measure pressure difference by the difference in high appearing on its tubes.
By the use of these two equations the equation that will be very useful for this lab is:
Manometer
Background
The Pitot tube was invented in 1732 by a French Engineer called Henri Pitot (1695-1771).
Due to design weakness the device was not effective and did was not used a lot.
But in 1856 improvements where made to the tube by another French Engineer called Henry Darcy with the assistance of Henri Bazin.
Those improvements brought the Pitot tube to large scale uses.
Application
This experiment provides the knowledge of measuring the velocity of a flow and the boundary layer thickness a long a the wall of the pipe.
This knowledge would be beneficial to calculate the speed of a fluid inside a pipe not just that but learning another method of calculating the speed of a moving object be the velocity of the flow surrounding it.
That method is already used in calculating the speed of aircraft as we can see the use of Pitot tubes on them, and it can be applied on cars or any other object.
Application
Procedure:
Turn on the motor and set it to 1250 RPM.
Make the discharge down stream open 10% and record the high of the manometers.
Repeat that process having the discharge down stream open 30%, 50%70%, and 100%.
Repeat the whole process for 2000 RPM, 2800 RPM, and 3600 RPM.
Application
Procedure:
Set the RPM to be 1250.
Adjust the radial position of the Pitot tube to be 3, 4, 6, 8, 10, 12, 16, 20, 24, 28, 32, and 38 mm and record the manometers 14, 17, and 19.
Repeat the same process for 2600 RPM and 3400 RPM.
Biblography
http://www.britannica.com/biography/Henri-Pitot
https://bae.okstate.edu/faculty-sites/Darcy/Pitot/DarcyAndThePitotTube.doc
Equations
Boundary layer and displacement thickness
δ=0.99 Vmax
δ=Boundary layer thickness (mm)
Vmax=Max velocity
δ*=
Reynolds number
V =
V=Average velocity
Re=Reynolds number
ρ=Density
v=velocity
D=Pipe diameter m
μ=Fluid viscosity
Mach number
Flow rate
Frictional losses in a pipe
Friction factor
Darcy weisbach friction factor
Discussion
Three different speeds were measured to find the velocity and pressure distribution in the duct.
Flow rate was controlled and gradually lowered from 100% to 10%. First at 100% then, 70% , 50% , 30% and finally 10%.
Results
Maximum pressure occurs at the boundary and reaches zero at the center.
Maximum velocity occurs at the center and reaches zero at boundary.
The results of the experiment supports the original theory that the pipe would viscous effect on the flow.
To avoid the errors
Always check the gages are working.
The Tubes should have been labeled clearly for a quick reading.
The actual rpm was different than the one we were measuring.
Summery
Volume flow rate was determined from the boundary layer measurement which yielded a velocity profile for the duct.
Graphs showed that the Velocity is at the max during the center of the duct.
The velocity measured at the boundary was found to be zero due to viscous effect of the duct
A smoother relationship was shown in the graphs between velocity and distance from the center squared.
The pressure does increase as the distance from the center increases; zero pressure at center and maximizes at the boundary.
conclusion
The result of the experiment shows that the flow will always follow the viscous affect no matter what speed it is.
In all three speeds; the velocity and pressure distribution follow the theory.
m S
m
S
Area V max
Area
Vmax
sum of v Number of velocites
sum of v
Number of velocites
kg m3
kg
m
3
kg ms
kg
ms
M = Vmax C
M = Mach number
Vmax = Max velocity m s
C = Speed of sound m s
M=
V
max
C
M=Mach number
V
max
=Max velocity
m
s
C=Speed of sound
m
s
Q = πA
Q = Volume flow rate m 3
s A = Area under the curve
Q=pA
Q=Volume flow rate
m
3
s
A=Area under the curve
q =C * A 2 * Δp Ρ
q = Flow rate C = Flow coefficient A = Cross section area of discharge side Dp = Density of the flow fluid Ρ = Density of the flow fluid g=acceleration of gravity
q=C*A2*
Dp
R
q = Flow rate
C = Flow coefficient
A = Cross section area of discharge side
D
p
=Density of the flow fluid
R=Density of the flow fluid
g=acceleration of gravity
f=0.184 Re−0.2
f=fricton factor
f=0.184 Re
-0.2
f=fricton factor
f = hL
L D
* V 2
2g f = Friction factor HL = height L = Length D = Diameter V =Velocity
f=
h
L
L
D
*
V
2
2g
f = Friction factor
H
L
=height
L=Length
D=Diameter
V=Velocity
