Engineering Explanation

7. STUDY PERFORMANCE CHARACTERISTICS TEST OF A PELTON TURBINE.

2020-11-01T14:03:00.000+05:30

Experiment Name: Study Performance characteristics test of a Pelton Turbine.

Objective:

(i) To study different components of a Pelton Turbine.

(ii) To obtain the operating characteristics of the Pelton Turbine.

(iii) To find the efficiency of the Pelton Turbine.

Apparatus Used:

1. Pelton Turbine,

2. Pressure Gauges,

3. Venturimeter,

4. Brake drum.

Specification:

Rated Supply head (H)=30 metre

Rated Discharge (Q)= 500 lpm

Normal Speed (N)= 1000 rpm

Maximum Jet diameter = 22mm

Theory:

It is a type of tangential flow impulse turbine used to generate electricity in the hydroelectric power plant. This turbine was discovered by the American engineer L.A. Pelton.

Pelton turbine working principle is that, here high speed jets of water emerge from the nozzles that surround the turbine. These nozzles are arranged such a way that the water jet will hit the buckets at splitters, the center of the bucket where the water jet is divided into two streams. The two separate streams then flow along the inner curve of the bucket and leave in the opposite direction that it came in. This change in momentum of the water creates an impulse on the blades of the turbine, generating torque and rotation in the turbine.

The energy available at the inlet of the Pelton turbine is only kinetic energy. The pressure at the inlet and outlet of the turbine is atmospheric pressure. This type of turbine is used for the high head.

Experimental procedure:

1. The Pelton turbine is placed on the sump tank level and a pump used for supply water to the turbine.

2. Set venturimeter to measure the flow rate to the turbine. The gate valve is placed at the inlet side of the turbine to regulate supply head.

3. A spear and nozzle arrangement is used to control amount water supply to the turbine bucket.

4. Check lubrication of the ball bearings, and make sure the pipelines are free from foreign particles.

5. Close the gate valve and the spear at the turbine inlet and make the hanger load free.

6. Start the pumpand then gradually open the gate valve and check the supply head by the reading of the pressure gauge.

7. Slowly open the spear by hand wheel for steady rotation of turbine.

8. Note down Pressure gauge reading.

9. Hang the load on the hanger. And due to the applied load the speed of the turbine will be decreased,

11. Now adjust the speed by changing the spear opening.

Observations:

input power:-

The input power

P_input = γQH/1000 KW

Where,

γ= ρg= specific weight of water,

Q= Discharge in m³/sec,

H= Supply head in meter.

∆h= Difference in pressure gauge reading of venturimeter in terms of head.

A₁= Inlet area of the venturimeter.

A₂= Throat area of the venturimeter.

C_d= Discharge coefficient of the venturimeter = 0.962

Output power:-

The output power P_output =2πNR_eTg/(60×1000) KW

Where,

N= Turbine shaft rotational speed r.p.m.

R_e= Effective radius of the brake drum.

T= Net brake load.

Data to be collected before starting the experiment:-

Temperature of the water= 20°C,

Density of the water (ρg)= 1000 kg/m³

Venturimeter inlet diameter (D₁) = 0.05 m

Venturimeter throat diameter (D₂) =30 m

Brake Drum diameter (D)= 0.2 m

Rope diameter (t)= 0.016 m

Effective radius Re= (D/2+t)= (0.2/2) + 0.016= 0.116 m

Weight of the rope and hanger (W_i)= 1 kg.

Note:- Sample pelton turbine calculation are shown below for input power and efficiency calculation.

Required Graph to be plotted:

A. Input Power vs Discharge.

B. Efficiency vs Discharge.

Note:- Both graphs are drawn on the same graph paper for better understanding.To draw a continuous proper graph some point of reading is to be ignored.

FAQ:

1. Draw the schematic diagram of the setup.

Figure- Pelton turbine setup.

2. Identify each components of Pelton turbine and briefly state the function of each component.

Parts of Pelton Wheel Turbine:-

1. NOZZLE WITH SPEAR ARRANGEMENTS- The water comes out from the circular guide mechanism through nozzle. Then the water Jet strikes the bucket.A conical needle called spear operates manually or automatically inside the nozzle in axial direction to regulate the flow.

2. RUNNER WITH BUCKET- Runner consists of a circular disc, on the Periphery of which the vanes or bucket is fixed. The water jet strikes the bucket and power is generated.

3. CASING- The casing generally made of cast or fabricated parts but does not perform any hydraulic function. it is used to safeguard the runner against accident and to prevent splashing of water.

4. BREAKING JET- In order to bring the runner to rest in a short time, an opposite jet is used for reducing the speed of the runner called Breaking jet.

3. Provide sample calculation.

4. Write Advantages and Disadvantages of Pelton wheels Impulse Turbine and pelton turbine application.

Pros:-

1. Simple in construction and easy to maintain.

2. They work at atmospheric pressure so no problem of leakage.

3. High efficiency.

4. It is easy to assemble.

Cons:-

1. This is not suitable for low-pressure streams by a high flow rate.

2. Impulse turbines are large in size compare to others.

3. Efficiency decreases with time.

4. Initial cost is high.

Applications:-

It's used for hydro-power when the available water source has a relatively high hydraulic head at low flow rates.

5. Why Pelton turbine is high head turbine?

The Pelton turbine is design to face the enormous kinetic energy of water jet. So the energy present at the inlet of the Pelton turbine is mostly and heavily kinetic energy that is why it is known as high head turbine.

Written by- SOUMIK.

6. FLOW MEASUREMENT IN OPEN CHANNEL BY V-NOTCH AND RECTANGULAR WEIR.

2020-10-26T11:47:00.000+05:30

Experiment Name: Flow measurement in open channel by V-Notch & rectangular weir.

V-Notch & rectangular weir Laboratory Setup.

Objective:

(i) To determine the coefficient of discharge of V-notch and rectangular weir for different rates of

flow.

(ii) To compare the results by plotting Q_actual vs H and Qₜₕₑₒ vs H in log-log graph for each results.

Apparatus Used:

1. An Open channel attached with V-notch, Rectangular weir.

2. Volumetric tank.

3. Stop watch

Theory:

Weirs are the instruments, which used to measure the discharge in open channel flow. Triangular weir which is often called V-notch is used when the discharge is small. The theoretical discharge formula for the V-notch is,

Where,

C_d=coefficient of discharge (Q_actual/Qₜₕₑₒ)

θ=Angle of V-notch,

H=Head over the weir.

For a particular weir C_dand θ are constant, the flow equation can be written as,

Q=KH5/2

For rectangular Weir,

Where,

C_d=coefficient of discharge (Q_actual/Qₜₕₑₒ)

For a constant value of b, the flow equation can be written as,

Q=KH3/2

Experimental procedure:

1. Fit the required notch in the flow channel.

2. Close the gate valve at the channel and fill up the water in the channel up to sill level.

3. Check if water leaks from the notch.

4. Take down the initial reading of crest level (sill level) by the piezometer.

5. Then open the gate valve (By pass valve) slowly so that water starts flowing over the notch.

6. Let the water level become stable and note down the height of water surface at the upstream side by the sliding depth gauge.

7. Close the drain valve of measuring tank, direct the collector into the measuring tank and measure the discharge.

8. Take several readings for different flow rates.

Observations:

Angle of the V-notch (θ)= 45°,

Cross sectional area of the volumetric tank (A)= 0.3× 0.3= 0.09 m²,

Width of the rectangular weir (b)= 10.7cm.

Total six readings for each V-notch and Rectangular weir is shown below,

Required Graph to be plotted:

(i) ‘Q’ vs ‘H’ in log-log graph paper. [Both Qₜₕₑₒ and Q_actual] [2× 3 cycle graph]

(ii) ‘C_d’ vs ‘H’ in Normal graph paper.

Figure- Q vs H in log-log graph.

Figure- C_d vs H in Normal graph.

FAQ:

1. Draw the schematic diagram of the setup.

2. Show sample calculation.

3. State assumptions taken during experiment.

a. Flow is steady,

b. Flow is laminar,

c. Velocity of approach is assumed small so that kinetic energy can be neglected.

4. Define velocity of approach. State its effect on the flow measurement.

Velocity of approach can be defined as the velocity with which the water reaches the weir or notch before it flows over it.

The velocity of approach is used to find an additional head (hₐ= V²/2g). Again the Q is calculated to get more accurate value.

Written by- SOUMIK.

5. PIPE FRICTIONAL LOSS CHARACTERISTICS FOR DIFFERENT FLOW RATE THROUGH DIFFERENT PIPES CALCULATION LAB EXPERIMENT.

2020-10-21T11:52:00.003+05:30

Experiment Name: Pipe friction characteristics for different flow regimes for flow through pipes.

Figure:- Experiment set-up

Objective:

To determine experimentally the friction factor for flow through different pipes, and to compare it with theoretical value.

Apparatus Used:

a. Pipe friction apparatus consisting of G.I b. Pipes of different diameter,

c. Flow control valve at outlet of pipes,

d. U-tube differential manometer,

e. Volumetric tank,

f. Stop watch.

Theory:

When a fluid is flowing through the pipe, it is subjected to resistance to flow due to shear forces between the pipe wall and fluid particles and between the fluid particles also. This resistance is called frictional resistance. This resistance depends upon the velocity of flow and area of surface in contact. It also depends upon the type of flow, i.e. laminar or turbulent. This frictional resistance causes loss of pressure in the direction of flow.

Reynolds number (Re) is the non-dimensional number which determines whether the flow is laminar or turbulent. For pipe flow transition flow starts when Re exceed 2000 and turbulent when exceeds 4000. For both laminar and turbulent flow, the friction factor which is a measure of frictional resistance offered to fluid motion, depends on Reynolds Number (Re). Besides this, another important factor is the relative roughness (ε/d) for the pipe which determines the level of friction in case of turbulent flow. For constant diameter pipe the energy loss over the length L may be characterized by an equivalent head loss hf which can be expressed according to Darcy-Weisbach equation, as

h_f =f× LU²/(D×2g)

where

f = Darcy’s friction factor

L= length of the pipe

D= diameter of the pipe

U = Average velocity of flow through the pipe

For fully developed laminar flow, theoretically it can be shown that f =64/Re i.e. f is Φ(Re) only.

For turbulent flow no such theoretical relationship exists. In turbulent flow region it has been seen f=Φ(Re, ε/d). However for smooth pipe (ε/d<10⁻⁶),range of Re (2000<Re<10⁵) with the following relation

f= 0.3164/Re¼

And this the variation of friction factor with Re with ε/d is usually shown in form of Moody’s diagram, which is the graphical representation of experimental data on friction of pipes with friction factor as a function of Reynolds Number and Relative roughness.

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Experimental procedure:

1. Start water flow by opening the inlet valve.

2. Check for leakages by closing two of outlet valves one by one for each pipe, and correct the leakage if any.

3. Open the outlet valves of the pipe to be tested.

4. Remove all the existing air bubbles from manometer and connecting pipes.

5. Reduce the flow. Adjust outlet valves then take readings of heads and flow rate.

6. Now, increase the flow and accordingly adjust the outlet valve, so that water will not overflow. Repeat above procedure for other pipes.

Observations:

Length of pipe between pressure tappings (L) = 1m,

Internal diameter of the G.I Pipes (D) = (i) Φ14 mm (ii) Φ19.5 mm,

Specific gravity of the manometric fluid= 13.57,

Cross sectional area of the volumetric tank (A) = 0.3m × 0.3m= 0.09 m²,

Temperature of the water= 20°C,

Kinematic Viscosity of the water from standard chart (ν)= 1.003 × 10⁻⁶ m²/Sec.

Note:- We only show three sample calculation of Φ14 mm diameter pipe, rest can be done in similar way. But in log-log graph we use all the data to plot the graph.

Required Graph to be plotted:

Draw f vs. Re in log-log graph paper

(2×3cycle). (Both Experimental & Theoretical)

[Draw f =64/Re for laminar flow and

f= 0.3164/Re¼ for turbulent flow.]

FAQ:

1. Draw the schematic diagram of the setup.

2. Provide sample calculation.

3. List out the sources of error.

1. There can be a fluctuation in Piezometric tube, so mean position must be taken.

2. The loss of head at valves and fittings can bring error.

3. Previously collected (Non-drained water) in Tank may cause error.

Written by:- SOUMIK.

4. Experimental Verification of Bernoulli's Equation Laboratory Report.

2020-10-16T13:20:00.006+05:30

Experiment Name: Verification of Bernoulli’s Equation.

Figure:- Experimental Setup

Objective:

(i) To find the validity of the Bernoulli’s equation for steady flow of water in a tapered duct.

(ii) To evaluate the different component of mechanical energy possessed by a fluid element at different section of the duct during flow.

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Apparatus Used:

The apparatus consists of a rectangular flow channel, which is tapered along the length. Flow area at inlet is maximum and it goes on decreasing upto the minimum value and then again increases to maximum at the outlet. Water is supplied to flow channel through direct pipe inlet connection. Outlet is directly connected to measuring unit.

Theory:

Bernoulli's Principle is named in honor of Daniel Bernoulli. This principle is the basis of Bernoulli's equation along a streamline, which states that the sum of all forms of energy in a fluid flowing along an enclosed path (a streamline) is the same at any two random points in that path.

When an incompressible fluid is flowing through a closed conduit, it may be subjected to various forces, which cause change of velocity, acceleration or energies involved. The major forces involved are classified as surface force and body forces. Due to change in cross section area of flow, velocity of fluid may change and pressure also changes at the same time. In short, if kinetic energy of fluid is raised, its pressure or flow energy will reduce so that total energy of fluid is constant at any two points along the flow path, for a steady, incompressible fluid flow.

Bernoulli's Principle is essentially a work energy conservation principle which states that for an ideal fluid or for condition where effects of viscosity are neglected, with no work being done on the fluid, total energy remains constant.

Hence, when applied to steady, incompressible, inviscid flow of fluids (i.e. ideal fluid flow) we can write,

P/ρg + V²/2g + z = Constant=H (Total Head)

Where P/ρg + z = Piezometric Head= h+h₁

h = Water rise upto free surface level from top of the channel at zero mark in piezometer tube,

h₁ = Distance from the duct center axis to the zero mark at top of channel. (Take it from given chart)

P = pressure,

V = average velocity at the section,

ρ=density of fluid,

g=gravitational acceleration,

V²/2g= Kinetic Head,

z = Potential head or Datum Head.

Experimental procedure:

1. Fill-up water tank, connected to flow channel.

2. Open the inlet valve, located at end of flow channel and allow the water to flow from supply tank.

3. Reduce flow by inlet gate valve, so that there is only a small rise of water in the last pressure tapping.

4. Now adjust the flow, so that we get a constant head in the supply tank to make flow in and flow out equal.

5. Allow the levels to stabilize in the piezometric tubes and take the readings of the heads.

6. Close outlet valve of the measuring tank, and measure the time to rise water level by a certain level in volumetric tank, at exit from flow channel. This will give the discharge rate through the flow

channel.

7. Now, repeat the procedure by changing the discharge rate, and note the drop of head at outlet for different observation.

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Observations: (Two Sample reading for different flow rate shown below)

For horizontal position of flow passage, the datum level is taken as centre axis of the flow channel, putting z=0 there, as reference level.

Area of Volumetric Tank= 0.15×0.15=0.0225 m²

Note:-

1. Here h is measured from experiment and h₁is taken from given chart. After calculating summation direct reading is written on the table below.

2. Rise of water level is taken as 0.1 m. Multiplying this rise of water level with area of tank we get the volume of water collected in tank in m³.

3. Area for each reading is calculated from the given table.

4 Finally our goal is to show that total head is approximately same for all readings.

1st Observation.

2nd Observation.

Given Table (To be provided to perform this experiment).

Required Graph to be plotted:

1. Length vs Piezometric Head along the length of the duct.

2. Length vs Kinetic Head along the length of the duct.

3. Length vs Total energy head (H) along the duct.

Note:- All graphs are drawn on the same graph paper for better understanding.To draw a continuous proper graph some point of reading is to be ignored. Corresponding readings taken from 1st Observation table above.

FAQ:

1. Draw the schematic diagram of the setup.

2. Provide sample calculation.

3. Explain Hydraulic Grade Line (HGL) and Total Grade Line (TGL).

Hydraulic grade line is a line representing the total head available to the the fluid minus the velocity head can be expressed as HGL= P/ρg + z.

Total grade line is a line that represent the total head (pressure head + velocity head + potential head) available to the fluid can be expressed as

TGL= (P/ρg + z) + V²/2g.

4. Write down the Bernoulli’s equation for Real Fluid.

it states that the sum of pressure head, kinetic head and potential head of a fluid particle is constant along a steam line during steady flow when compressibility and frictional effect are negligible.

Total Head= P/ρg + V²/2g + z = Constant

Where P/ρg= pressure head

V²/2g=kinetic head,

z =datum head or potential head.

5. State the assumptions made to use Bernoulli’s equation from Euler’s equation.

i) Fluid must be ideal that is viscosity is zero.

ii) Flow is continuous,steady and along the streamline.

iii) Fluid must be incompressible.

iv) The velocity of flow is uniform over the section.

Written by- SOUMIK.

3. DETERMINE CHARACTERISTICS OF LAMINAR FLOW AND TURBULENT FLOW WITH EXPERIMENT.

2020-10-13T11:32:00.001+05:30

Experiment: Characteristic of Laminar & Turbulent flow.

Objective:

(i) To study the characteristic of laminar and turbulent flow in a pipe by using simple flow visualization.

(ii)To find out the Critical Reynolds Number for pipe flow.

Apparatus Used:

1. Reynolds Apparatus

2. Measuring Flask

3. Stop Watch

Theory:

The flow of real fluids can basically occur either laminar or turbulent flow. The laminar flow is characterized by fluid particles moving in the form of lamina sliding over each other, such that at any instant the velocity at all the points in particular lamina is the same. The lamina near the flow boundary move at a slower rate as compared to those near the center of the flow passage. This type of flow occurs in viscous fluids, fluids moving at slow velocity and fluids flowing through narrow passages.

The turbulent flow is characterized by constant agitation and intermixing of fluid particles such that their velocity changes from point to point and even at the same point from time to time. This type of flow occurs in low density Fluids flow through wide passage and in high velocity flows. Reynolds conducted an experiment for observation and determination of these regimes of flow. By introducing a fine filament of dye in to the flow of water through the glass tube, at its entrance he studied the different types of flow. At low velocities the dye filament appeared as straight line through the length of the tube and parallel to its axis, characterizing laminar flow. As the velocity is increased the dye filament becomes wavy throughout indicating transition flow. On further increasing the velocity the filament breaks up and diffuses completely in the water in the glass tube indicating the turbulent flow. After conducting his experiment with pipes of different diameters and with water at different temperatures Reynolds concluded that the various parameters on which the regimes of flow depend can be grouped together in a single non dimensional parameter called Reynolds Number.

Reynolds Number is defined as, the ratio of Inertia Force to the Viscous Force, where viscous force is shear stress multiplied surface area and inertia force is mass multiplied acceleration of the fluid particles.

Re₌ρUD/μ= UD/ν

where

Re-Reynolds Number,

U - Velocity of flow,

D - Characteristic length = diameter in case of pipe flow,

ρ - Mass density of fluid,

μ - Dynamic viscosity of fluid,

v = μ/ρ - Kinematic viscosity of fluid.

Reynolds observed that in case of flow through pipe for values of

Re<2000 the flow is laminar,

Re>4000 it is turbulent and for,

2000<Re<4000 it is transition flow.

Experimental Procedure:

1. Fill up sufficient amount of water in the upper head tank.

2. Start water flow through pipe and adjust gradually.Start dye injection.

3. Wait for some time. A steady line of dye will be observed. Adjust dye flow, if required.

4. Slowly increases the water flow keeping water level in supply tank constant. At particular flow rate, dye line will be disturbed.Note down this flow rate.

5. Further increase the flow. The disturbances of dye line will go on increasing and at certain flow; the dye line diffuses over the entire cross section. Note down this flow.

6. Slightly increase the flow and then slowly reduce the flow. Note the flow at which diffused dye tends to become steady. (beginning of transition zone while reducing velocity.)

7. Further reduce the flow and wait for the flow at which dye line becomes straight and steady.

Observations:

1. Internal diameter of the glass tube= Ø.025 m

2. Cross sectional area of the glass tube= 4.9087 × 10⁻⁴ m²

3. Temperature of the water= 20°C

4. Density of the water= 998.2 kg/m³

5. Kinematic Viscosity of the water [from standard table]= 1.0035 ×10⁻⁶ m²/Sec

FAQ :

1. Define Critical Reynolds Number and state its physical significance. State the value of Critical Reynolds Number for the present experiment.

Critical Reynolds number is determined as a limit where the laminar flow changes to turbulent flow.

Significance- As this is proportional to the ratio of inertia force to viscous force. it can be used to study the fluid flow whether it is laminar or turbulent.

From our experiment we get 3 different values of Reynolds number for different flow rate as following,

1245(Laminar)
3462(Transition)
5132(Turbulent)

2. List the sources of the error of the experiment.

a. Take this charge reading accurately.

b. Set the discharge value constant during each flow.

c. During whole experiment fluid storage tank should maintain a constant head. But to prevent turbulence that can not be maintained during experiment.

3. Draw the schematic diagram of the experimental set-up.

Written by:- SOUMIK

2. DETERMINATION OF COEFFICIENT OF DISCHARGE OF VENTURIMETER AND ORIFICE METRE.

2020-10-10T11:46:00.000+05:30

Experiment Name: Determination of Coefficient of Discharge of Flow Measuring Devices.

Figure:- Orifice metre(At back with orifice plate) and Venturi metre(At front with converging and diverging shape).

Objective:

(i) To determine the coefficient of discharge of Venturimeter.

(ii) To determine the coefficient of discharge of Orificemeter.

Apparatus Used:

Venturimeter with pipe line assembly, Orificemeter with pipe line assembly, differential U-tube manometer, Flow Measuring Tank and Stop watch.

Theory:

The discharge Q through the flow meter fitted in a pipeline can be expressed in terms of discharge coefficient C_d of the meter and piezometric head difference H across the meter as follows,

Where, C_d =Coefficient of discharge,

D_i =Pipe diameter.

D_o =Throat diameter for Venturimeter, Orifice diameter for Orificemeter.

A_o=Throat area / Orifice area

H = Piezometric head difference between inlet and throat = x(ρ_m/ρ_w−1)

where x = deflection of manometric fluid in differential U tube manometer.

Experimental procedure:

1. Check the manometer connection and if air is tapped in drive out by opening air cock.

2. Check the valves connection to the setup.

3. Open the inlet valve and the flow control valve of the corresponding flow meter pipe line, keeping other inlet valve close.

4. At a particular opening of the flow control valve, take the manometer reading.

5. Measure the flow rate by the volumetric tank and stop watch.

6. Change the flow control valve opening.

7. Repeat the steps 4, 5 & 6 to take different reading.

8. After Venturi metre reading repeat the same proceedure for Orifice metre.

Observations:(Sample reading shown below)

Specific gravity of the manometric fluid= 13.633
Cross sectional area of the volumetric tank 300 mm × 300 mm
Temperature of the water= 20°C
Density of the water= 998.2 kg/m³
Viscosity of the water from standard chart= 8.90×10⁻⁴Pa.s

Parameter Table:

FAQ:

1. List the sources of the errors of the experiment.

a. when all valve is closed in beginning manometric fluid difference is not zero.

b. The parallax error should be avoided.

c. Maintain a constant discharge during each reading.

d. Keep the other closed during one experiment to prevent leakage.

e. The pipe connection should be dust,dirt free to get proper reading of coefficient of discharge of flow metre.

2. Provide sample calculation.

3. Define co-efficient of discharge for Orificemeter and discuss “Vena-contracta”.

Coefficient of discharge can be defined as the ratio between actual flow of the discharge to the theoretical discharge.

When fluid is passing through a small orifice /hole , sudden contraction is taking place in the stream of fluid. Once the fluid is passing through the orifice even though the contraction of the stream remains continue in the streamwise direction. The minimum flow cross section of the stream is called the point of venacontracta, where velocity is maximum.

4. Draw the schematic diagram of the setup.

5. Compare the use of Orificemeter and Venturimeter as primary elements for flow measurement.

1. A venturi meter can be used to measure flow rate of all incompressible fluids (gases with low pressure variations, as wells as liquids), whereas an orifice meter is generally used for measuring the flow rate of liquid.

2. Venturimeter gives you a better result than Orificemeter as Venturi meter losses are less so coefficient of discharge is higher whereas in orifice meter due to no convergent and divergent cones there are more losses and hence its coefficient of discharge is less.

3. Venturimeters are relatively expensive than orifice.The installation cost is high but lower maintenance and operational cost.

Written by- SOUMIK.

1. DETERMINATION OF AIR FLOW VELOCITY BY USING A PITOT STATIC TUBE.

2020-10-07T20:05:00.007+05:30

Experiment Name: Determination of airflow velocity by using a Pitot static tube.

Objective:

(i) Measurement the air flow velocity through a closed duct by using a Pitot static tube.

Apparatus:

Pitot static tube, differential U-tube manometer, blower with pipe line assembly.

Theory:

The principle of flow measurement by Pitot tube was adopted by Henri Pitot in 1732. To measure the flow by a Pitot tube the necessity of separate piezometer and thus two readings make this arrangement a little awkward. Connecting the piezometer to a manometer would simplify things but there are still two tubes. For a fluid flowing through a closed duct, the Pitot tube measures only the stagnation pressure and so the static pressure must be measured separately. Measurement of static pressure in this case is made at the boundary of the wall by piezometer tube. The Pitot static tube combines the tubes recording the static and the stagnation pressure into one instrument which can then be easily connected to a differential manometer. The tube for sensing static pressure is known as static tube which surrounds the pitot tube that measures the stagnation pressure. A Pitot static tube is shown below in Figure. The holes on the side of the tube connect to one side of a manometer and record the static pressure, while the central hole is connected to the other side of the manometer to record, the stagnation pressure.

Figure:- Pitot static tube with differential manometer.

Now applying Bernoulli’s equation between point 1 and 2 we get,

where, ∆h = difference in manometric fluid level

Experimental procedure:

1. Start the flow of air through a closed duct by starting the blower.

2. Keep the flow control valve fully open and check the connection of the open end of Pitot static tube to the manometer.

3. Note down the reading of deflection of manometric fluid as the liquid in the manometer will be displaced due to differences between stagnation and static pressures.

4. Take reading in observation table.

5. Repeat above steps for different flow control valve opening.

Observations: (Sample reading shown below taken at room temperature)

Temperature= 31°C
Density of working fluid (ρ of air)= 1.1644 kg/m³
Density of manometric fluid (ρ of H₂O)= 995.2 kg/m³

FAQ :

1. List out the sources of error.

a. It requires high velocity flow.

b. It generates very low differential pressure which is difficult to measure.

c. Working fluid must not be dirty or sticky.

d. It block easily, particularly if there is debris in the flow line.

2. Draw the schematic diagram of the setup.

3. Provide sample calculation.

4.Describe- Static pressure, Dynamic pressure and Stagnation pressure.

Static pressure is the internal pressure of a flow if the pressure measuring device travels along with the flow. You can also measure it with a small hole in a surface along which the flow travels.

Dynamic pressure is the kinetic energy per unit volume of a fluid particle it is that pressure of fluid that results from its motion.

Stagnation pressure at a point in a fluid flow is the pressure which could result if the fluid were brought to rest isentropically. it implies that entire kinetic energy of fluid particle is utilised to increase its pressure only.

Stagnation pressure= static pressure + dynamic pressure.

Written by- SOUMIK.

AUTOMATIC TRANSMISSION SYSTEM- Theory in details

2020-10-05T13:42:00.004+05:30

A. WHAT IS AUTO TRANSMISSION SYSTEM :~

Automatic transmission is a type of motor vehicle transmission that can automatically change the gear ratios at the vehicle moves, freeing the driver from having to shift gears manually.

B. DIFFERENT PARTS:~

- Clutch

- The gear box

- Propeller shaft

- Universal joints

- Rear axle

- Wheel

- Tiers

C. FEATURES OF AUTOMATIC TRANSMISSION :~

1. Automatic transmission:-

Shifts gears automatically, does not require a manual clutch.

2. Front-wheel-drive vehicles:-

Combine transmission with differential in transaxle.

3. Most automatic transmissions use a torque converter.

4. Some use a dual clutch arrangement.

D. PARTS OF AUTOMATIC TRANSMISSION:~

Torque Converter

Input Shaft

Transmission Pump

Planetary Gear Set

Governor and Modulator

Valve Body

Multiple Clutch Plate

E. METHODS OF POWER TRANSMISSION:~

Different kind of methods can be use as follows-

I) Fluid, friction, and gears starts working with power input.

II) Torque converter transmits power by using fluid.

III) Planetary holding members starts to work by using fluid and friction.

IV) Gears transmit power and change speed and torque.

F. ADVANTAGES :~

✓ Shifts gear automatically.

✓Doesn’t need to change gear with subsequent speed.

✓ Makes journey more easier and comfortable.

✓ Lower risks at higher speed.

G. DISADVANTAGES :~

✓ More costlier than manual transmitted cars.

✓ Makes the engine design more complicate.

✓ As partly controlled by automation, Electronic faults may occur.

H. APPLICATIONS:~

I) Widely used in high speed cars.

II) Modern luxurious cars, heavy duty trucks.

III) In six strokes and eight strokes heavy

engines.

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