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Measuring stations

Measuring stations for fansFans (standard EN ISO 5801 Fans -- Performance testing using standardized airways)

Pa power in Wpt total pressure in Papst static pressure in Pa𝜂𝑟 efficiency in %𝜂𝑠𝑟 static efficiency in %

Fig.: example of the measured characteristics at constant speed for constant (above) and for variable pitch (bottom)

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Measuring stations

Fans (standard EN ISO 5801 Fans --Performance testing using standardized airways)4 installations:A - free inlet and free outletB - free inlet and ducted outletC - ducted inlet and free outletD - ducted inlet and ducted outlet

So ... fans are located in measuring stations at the inlet, ducted or at the exit

The characteristics of the fan (flow, pressure) can not be measured unless it is built in the measuring station.

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Measuring stations

Hidria Rotomatika- measuring station for aerodynamic characteristics- a reverberation room for acoustics

(1) Measuring station according to ISO 5801: 2006 standard(2) Reverberation room(3) The location of the axial fan assembly(4) Grid(5) Nozzles for measuring volume flow(6) Sensors for measuring temperature and relative humidity(7) Barometer pressure sensor(8) Sound attenuators(9) Air filter(10) Flow control(11) Auxiliary fan(12) Sound attenuators(13) Direction of airflow

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Measuring stations

Kategorija A - prost vstop in prost izstopin postaja na vstopupretok določamo na naslednje načine- šobo na vstopu (zgoraj)- zaslonko na vstopu (v sredini)- zaslonko v cevi- traverziranjem s Pitojevo cevjo (spodaj)- več šobami v komori- zaslonko v komori

Ni dušilne lopute. Del med merilnikom pretoka in ventilatorjem mora biti plinotesen.Za pomožnim ventilatorjem usmernik.Pred merjenim ventilatorjem umirjevalnik.Enačba velja za vse tri primere.

Na sliki:1 - pomožni ventilator2 - merjeni aksialni ventilator3 - merjeni radialni ventilator4 - konus za prehod na premer merilne postaje5 - usmerjevalnik toka6 - Pitojeva cev7 - mrežica za umirjanje toka

∆𝑝tot= ∆𝑝st + ∆𝑝izg𝑃𝐿3−𝑃𝐿1

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Measuring stations

Installation A - free inlet and free outletin postaja na izstopuflow rate determination- with several nozzles or orifices in the station- the flow is determined by the nozzles, there is no damping flap

Before the nozzle is grid. Straightener is not needed because the chamber cross section is large before the nozzles.

In fig. :1 - measured fan2 - flow straightener3 - auxiliary fan

∆𝑝tot= ∆𝑝st + ∆𝑝izg𝑃𝐿2−𝑃𝐿4

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Measuring stations

Installation B - free inlet and ducted outletflow rate is determined:- the orifice at the exit (top)- orifice in pipe(middle)- with the Pitot's tube- several nozzles in the chamber- several orifices in the chamber

Between the fan and the location of static pressure measurement, the flow straightener. In front of the orifice flow straightener.Fig. top (without damping) and middle (damping):1 - measured fan2 - cone3 - stream router4 - chokePL4 - static pressurePL6 - PL8 - Pressure tappingsFig. bottom:4 - nozzles in the chamber5 - auxiliary fan

∆𝑝tot= ∆𝑝st +1

2𝜌𝑐2𝑃𝐿4 + ∆𝑝izg𝑃𝐿2−𝑃𝐿4

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Measuring stations

Installation C - dusted inlet and free outletflow is determined:- orifice at inlet (top)- orifice in pipe (bottom)- traversing with Pitot tube

Fig. top: (no damping, auxiliary fan):1 - cone2 - auxiliary fan3 - transition to the rectangular pipe4 - measured fanPL3 - static pressure tappingPL1 and PL2 - fan limitsPL7 - orificePL5 - orifice Pressure Measurement

Fig. bottom (damping , no auxiliary fan):1 - throttle hatch4 - the flow straightenerPL5 and PL7 - orifice pressure tapping ∆𝑝tot= ∆𝑝st −

1

2𝜌𝑐2𝑃𝐿3 + ∆𝑝izg𝑃𝐿1−𝑃𝐿3

∆𝑝tot= ∆𝑝st −1

2𝜌𝑐2𝑃𝐿3 + ∆𝑝izg𝑃𝐿1−𝑃𝐿4

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Measuring stations

Installation D - ducted inlet and ducted outletflow is determined in a similar way to installations B and C, if diametersbefore and after the fan are different, we take into account the change in dynamic pressure

Fig. top:1,3 - cone2 - measured fanPL3 - static pressure tapping and traversingPL1 and PL2 - fan limits

Fig. bottom:1 - measured fan2 - flow straightenerPL1 and PL2 - fan limitsPL4 - static pressure measurement

∆𝑝tot= ∆𝑝st −1

2𝜌𝑐2𝑃𝐿1 +

1

2𝜌𝑐2𝑃𝐿2 + ∆𝑝izg𝑃𝐿3−𝑃𝐿1 +∆𝑝izg𝑃𝐿2−𝑖𝑧𝑠𝑡𝑜𝑝

∆𝑝tot= ∆𝑝st + ∆𝑝izg vstop−𝑃𝐿1 +∆𝑝izg𝑃𝐿2−𝑃𝐿4

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Measuring stations

It is not enough to just build a measuring stationTo determine the characteristics, power and efficiency, we have to measure the following variables (not necessarily all simultaneously):- volume flow- mass flow (temperature, pressure, density)- static pressure- total pressure- speed- torque- mechanical power- electric power

When measuring water turbines or pumps, cavitation (NPSH) is also measured.

Fig: 3: container with free surface.The air is pumped out with a vacuum pumpto change NPSH.

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Measuring stations

Measurement of volume flow- orifices- nozzles- venturi tubes- traversing with Pitot's tube- electromagnetic flowmeter

When the liquid passes through the constriction, the velocity increases, and the static pressure decreases according to the Bernoulli equation. This phenomenon is used to determine the volume or mass flow.The disadvantage of these methods is the pressure loss.The weakness of the traversing is high measurement uncertainty.

Fig. top: orifice, middle: of two different nozzle designs, bottom: traversing positions

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Measuring stations

Flow rate measurement with orifice- flow coefficientα- expansion coefficient ε- orifice diameter d- pressure in the front of the orifice 𝑝𝑢

The flow coefficient is read from tables and graphs or calculated from equations.

Fig: Flow coefficient α depending on diameter ratio β and Re

ሶ𝑉𝑚 = 𝛼 ∙ 𝜀 ∙ 𝜋 ∙𝑑2

42𝜌𝑢∆𝑝

𝑅𝑒 =𝐷 ∙ 𝑐𝐷𝜈

𝜀 = 1 − 0,41 + 0,35𝛽4Δ𝑝

𝜅𝑝𝑢

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Measuring stations

Measurement of mass rate with orifice, continuation

- Expansion coefficient ε is for low pressure rates almost 1

Fig.: flow coefficient α depending on the pressure ratio of the orifice and the pressure in front of the orifice

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Measuring stations

Mass flow measurement - airflow densityThe density of the air ρa must be determined to get flow rate. For this we need:- dry Ta = Td and wet bulb temperatureTw

(in equation θa [K])- barometric pressure pa

- relative pressure in front of orifice pu

- partial pressure of water pv , for this we need psat and equation on the right- Aw= 6,6×10−4/°C for Tw between 0 °C and150 °C- or equations for 0-30 °C or 0-100 °C

𝜌𝑎 =𝑝𝑎 − 0,378 ∙ 𝑝𝑣

287 ∙ θ𝑎

𝑝𝑣 = 𝑝𝑠𝑎𝑡 𝑇𝑤 − 𝑝𝑎𝐴𝑤 𝑇𝑑 − 𝑇𝑤 1 + 0,00115𝑇𝑤

θ𝑎 = 𝑇𝑎 + 273,15

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Measuring stations

Measurement of static and total pressure- pressure drop on the wall, at least 4x, aerodynamic or hydrodynamic averages- flush mount to prevent changes in flow velocity in the vicinity of the connection (dynamic pressure)- leakage- pressure meters now have accuracy better than 0.1%, including, for example, 0.025%- absolute, gauge, differential

In the picture above there are two types of pressure averagins, chamber and ring.Below the differential pressure transducer and installation on the model turbine.

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Measuring stations

Drive or braking to measure mechanical/electric power

- electric motor / generator- brake: vortex current- hydraulic brake P n3

- mechanical brake, torque from 0

Torque measurement on the bearing housing - hydrostatic bearing. Hydrostatic bearing is used for very accurate measurements. Mostly we measure without.For losses in bearings and seals, the water turbine and the pump are rotated in the air, and the fan without the runner, if possible.

𝑃𝑒𝑙 ∙ 𝜂 = 𝑃𝑎𝑒𝑟𝑜 = ∆𝑝𝑡𝑜𝑡 ∙ ሶ𝑉

𝑃𝑚𝑒ℎ = 𝑀 ∙ 𝜔

𝑀𝑚 = 𝑀

𝑀𝑚 = 𝑀 ±𝑀𝑙𝑚

Measuring stations

Measurement of mechanical or electrical power

A) electric (top) at point 2:1 - electric power delivered2 - losses of the frequency converter (but it can also be 2 power analyzer)3 - losses in electric motor4 - losses in the belt transmission5 - losses in bearings6 - losses in the runner and the casing (heat)7 - aerodynamic powerCalibration of the electric motor is required

B) mechanical (below):- rotational speed- trque

The torque can be measured dynamically or statically (the bottom image, measuring cell does not rotate).

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Measuring stations

Measurement of mechanical power1. Motor (dynamic) on the measuring station:- strain gauge on the shaft (rotating) - wireless - strain gauge on the shaft (rotating) - transmission with slip rings (fig. below)

2. Motor (static) attached to torque measuring cell:- strain gauge between the motor and the casing,the measuring cell must be compensated

3. Motor can rotate (fig. middle)- bearing on motor or load or both- hydrostatic bearing on the load and or motor- "weighing" of torque, possible with counterweight - protection of the measuring cell with springs- point load

Top: slip rings, Middle: weighing of the torque (cell left and weights), Bottom: mounting of the stain gauges on the shaft of the ship's turbine, wireless transmission

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Measuring stations

Measuring rotational speed1. magnetic encoder2. incremental counter, inductive or optical3. handheld meter, optical or contact4. stroboscope (TI exercises, cavitation observation)5. Hall's sensor6. etc.

In the figure above, the frequency meter(magnetic encoder) at the top of the motorgenerator in TI, middle: incremental counter, bottom: hand-held instrument

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Measuring stations

Measuring stations for water turbinesTurboinštitut:1: turbine model with motorgenerator2: high pressure vessel with grid3: low pressure vessel4: circulation pumps5: flow straightener6: electromagnetic flow meter

Fig top: point 1bottom: point 1 is exchanged when different model turbines are tested

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Measuring stations

model measurement in the institute

- flow, pressure, power, efficiency- measurement of force on the blade, axial forces, geometric similarity, runaway speed, cavitation (but not erosion)- measuring devices are similar to those of fans- additional possibility of measuring the head H- venting of connection tubes for pressure measurement- mounting height of pressure transducer- hydrostatic bearing of the turbine for precise measurement of torque, power and efficiency

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Measuring stations

examples of different types of water turbinesand pump types

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Measuring stations

for exercises: Kaplan turbine, case of HPP Solkan, double regulation

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Measuring stations

For exercises: Bulb turbine, here HPP Dubravadouble regulation

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Measuring stations

Measuring stations for measuring the characteristics of pumps KSB