Objective:
The performance of a radial flow rotor in air is to be determined over a wide range of operating conditions and for interchangeable impellers with forward, backward and radial blades.
Apparatus:
Single stage radial flow fan equipped with interchangeable impellers, with forward-curved, backward-curved and radial blades, variable speed D.C. electric motor with swinging field dynamometer, a counter for speed measurements, three single column manometers, standard 75 mm nozzle.
The fan draws air from the atmosphere by way of the measuring nozzle, a flow straighter, and a diffuser, while the fan discharge into the atmosphere is regulated by a throttle valve.
Procedures:
The fan is to run at a series of constant speeds not exceeding 3000 rev/min, and the flow rate is to be varied in each test by means of the throttle. Measure the speed N; torque T by noting the balancing force, the pressure rise H generated by the fan and measurable by a manometer across the machine graduated in cm of water. For each run N is kept constant and the throttle is altered from open to fully shut, thus changing T, H and Q.
Theory:
The fan total pressure rise is defined as the difference between the total pressures at fan outlet and fan inlet i.e. it is a measure of the total pressure difference imposed on air by the fan. In the apparatus (fan) the cross-sectional area at inlet and exit are equal.
It follows that the velocity pressure at inlet and exit are equal and the fan total pressure rise is equal to the difference between the corresponding static pressure.
If Q = volumetric rate of flow (m3/s) and is calculated by:
Where:
T = air temperature in oK
h1 = drop in head at the standard nozzle in cm H2O
Pa = atmospheric pressure in N/m2
The total air power of the fan or the useful work done is equal to the product of fan total pressure and volumetric rate of flow:
Note h3> 0 and h2 < t =" Torque" f =" Load" n =" Angular" r =" 17.9" cm =" 0.179" power =" Powershaft">
The performance of a radial flow rotor in air is to be determined over a wide range of operating conditions and for interchangeable impellers with forward, backward and radial blades.
Apparatus:
Single stage radial flow fan equipped with interchangeable impellers, with forward-curved, backward-curved and radial blades, variable speed D.C. electric motor with swinging field dynamometer, a counter for speed measurements, three single column manometers, standard 75 mm nozzle.
The fan draws air from the atmosphere by way of the measuring nozzle, a flow straighter, and a diffuser, while the fan discharge into the atmosphere is regulated by a throttle valve.
Procedures:
The fan is to run at a series of constant speeds not exceeding 3000 rev/min, and the flow rate is to be varied in each test by means of the throttle. Measure the speed N; torque T by noting the balancing force, the pressure rise H generated by the fan and measurable by a manometer across the machine graduated in cm of water. For each run N is kept constant and the throttle is altered from open to fully shut, thus changing T, H and Q.
Theory:
The fan total pressure rise is defined as the difference between the total pressures at fan outlet and fan inlet i.e. it is a measure of the total pressure difference imposed on air by the fan. In the apparatus (fan) the cross-sectional area at inlet and exit are equal.
It follows that the velocity pressure at inlet and exit are equal and the fan total pressure rise is equal to the difference between the corresponding static pressure.
If Q = volumetric rate of flow (m3/s) and is calculated by:
Where:
T = air temperature in oK
h1 = drop in head at the standard nozzle in cm H2O
Pa = atmospheric pressure in N/m2
The total air power of the fan or the useful work done is equal to the product of fan total pressure and volumetric rate of flow:
Note h3> 0 and h2 < t =" Torque" f =" Load" n =" Angular" r =" 17.9" cm =" 0.179" power =" Powershaft">
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