© Photo | ebm-papst

A system­atic approach

Improved flow machine


The effi­ciency of Green­Tech EC motors leaves little to be desired. That said, a high motor effi­ciency level does not neces­sarily guar­antee that the system as a whole will be just as effi­cient. Measure­ments have shown that the successful RadiPac fans still offer poten­tial for improve­ment in this respect. Which is why the flow machine has now come under scrutiny again at ebm-papst.

Luftstrom-betrachtung

Fig. 1: The entire air flow in the AHU was taken into consid­er­a­tion for opti­mi­sa­tion of the new RadiPac.

Following a detailed loss analysis and qual­i­fi­ca­tion process, the modi­fi­ca­tion work mainly concen­trated on the air inlet into the impeller, the posi­tioning of the external rotor motor in the impeller and the blade profile of the impellers. With a view to improving the air flow (Fig. 1), the aim was thus to increase effi­ciency whilst at the same time reducing noise emis­sions. After all, the acoustic perfor­mance of a fan is consid­ered to be one of the impor­tant features in most appli­ca­tions.

Air inlet grille – a useful addi­tion

FlowGrid

Fig. 2: Flow­Grid air inlet grille for centrifugal fans.

Varying degrees of turbu­lence occur in the intake area of the fan due to the often confined instal­la­tion space. Opti­mi­sa­tion of the fan cannot compen­sate for such inflow distur­bance. The turbu­lence arising from the instal­la­tion situ­a­tion can however be reduced by modi­fying or opti­mising the inflow of air to the fan, which also helps to keep down the asso­ci­ated annoying low-frequency noise. This was the reason for devel­oping an optional special air inlet grille which has a straight­ening effect on the inflowing air (Fig. 2). The grille dras­ti­cally reduces noise-gener­ating distur­bance in the inflowing air. Regard­less of the building struc­ture and the instal­la­tion situ­a­tion in the housing, the fans then attain noise levels compa­rable to oper­a­tion under labo­ra­tory test condi­tions (Fig. 3).

Fig. 3: Convincing results: Flow­Grid lowers the sound pres­sure level and distinctly reduces tonal noise.

Inlet nozzle

An intel­li­gent combi­na­tion of compo­nents is the key to achieving good system perfor­mance. Which is why the inlet nozzle of the new RadiPac fans is designed to perfectly match the impeller with its aero­dy­nam­i­cally opti­mised blade channel. This lessens turbu­lence right at the air inlet, thus reducing flow loss and at the same time elim­i­nating one of the causes of noise nuisance. The tran­si­tion from the inlet nozzle to the impeller cover plate has also been modi­fied to produce a clearly defined gap flow. As a result the turbu­lence in the air flow, which would narrow the effec­tive flow cross-section, is reduced at this point as well. This modi­fi­ca­tion again adds to the effi­ciency of the system as a whole. An opti­mally posi­tioned pres­sure tap for air flow measure­ment is also provided as stan­dard, making commis­sioning easier for users.

New blade contour

The mechan­ical design and aero­dy­namic prop­er­ties of the new aluminium
airo­foil blades provide greater effi­ciency. The hollow profile of the blade keeps the weight of the impeller to a minimum whilst maxi­mizing the rigidity. The extremely rigid impeller also permits high circum­fer­en­tial speeds.

Through-flow

On account of the gentle rounding of the blade inlet, there is little inflow loss. The profiled contour guides the air flow through the blade channel with minimal loss before it leaves the impeller with hardly any turbu­lence thanks to the thin trailing edge. The specially shaped impeller base plate routes most of the outflowing air in axial direc­tion. This reduces the deflec­tion losses in the air condi­tioning device as well as the pres­sure drop when installed (Fig. 4). An added advan­tage is a lower noise level.

Luftstrom-technisch

Fig. 4: The influ­ence of the modi­fi­ca­tions on effi­ciency is deter­mined by way of flow simu­la­tion. The outflow char­ac­ter­is­tics have been opti­mised.

 

Opti­mised motor posi­tion

The posi­tion of the motor in the impeller has also been altered to achieve a good compro­mise between the compact design of the fan unit as a whole and the best possible loca­tion of the motor in the impeller from an aero­dy­namic point of view. The centrifugal impellers are attached to the rotor, in other words directly to the “housing” of the external rotor motor. This partic­u­larly helps to reduce the axial dimen­sions whilst at the same time improving cooling, as the motor is cooled by the air conveyed by the fan. In addi­tion, the entire rotating assembly made up of rotor and impeller is dynam­i­cally balanced in two planes at the produc­tion stage to ensure extremely low-vibra­tion oper­a­tion.

System concept rather than indi­vidual compo­nents

There is yet another convincing aspect to the centrifugal fans. Along­side the high-perfor­mance impeller with inlet nozzle, a Green­Tech EC motor and control elec­tronics, the RadiPac product range for use in air handling units includes addi­tional mechan­ical compo­nents (Fig. 5) to provide customers with complete ready-to-install fan units. In contrast to other concepts – employing asyn­chro­nous or PM motors for instance – users do not have to go to the trouble of purchasing, fitting, connecting and matching up indi­vidual motors, frequency converters and impellers.

RadiPac_Update_Explosion

Fig. 5: For ebm-papst a fan is more than just an impeller. It is an opti­mised unit made up of at least the following compo­nents: Preci­sion impeller with inlet nozzle, Green­Tech EC motor and control elec­tronics.

 

Plug & Play

Screenshot

Fig. 6: The product selector shows all the rele­vant fan oper­ating data including an accu­rate record of the data in part load oper­a­tion.

What’s more, there is no need for any addi­tional elec­tronic filters or screened cables with RadiPac fans, as the motor and the elec­tronics inte­grated into the motor system are already perfectly coor­di­nated and situ­ated close together. External motor circuit-breakers are also super­fluous. That’s what Plug & Play for venti­la­tion tech­nology is all about. Our certi­fied product selector (Fig. 6) permits the real­istic model­ling of the oper­ating situ­a­tions to be expected for a specific appli­ca­tion on the basis of the measured perfor­mance data of the fan. Absolute plan­ning reli­a­bility is thus guar­an­teed.

The infi­nitely vari­able speed control typical of EC motors also enables the fan perfor­mance to be exactly adapted to indi­vidual require­ments. Either the stan­dard 0-10 V DC/PWM input or the Modbus-RTU inter­face can be used for commu­ni­ca­tion.

Product selec­tion made easy

Screenshot

Fig. 6: The product selector shows all the rele­vant fan oper­ating data including an accu­rate record of the data in part load oper­a­tion.

As an added feature and to help choose the right fan, the ebm-papst “Product selector” soft­ware with inte­grated “Black Box” module is avail­able for incor­po­ra­tion into customer device config­u­ra­tion programs. With the new selec­tion program, RadiPac fans can be picked out on the basis of the oper­ating point. If there are several fans in the spec­i­fied perfor­mance range, the aero­dy­namic and acoustic data displayed can be used to help choose and docu­ment the most suit­able model. Another option avail­able is calcu­la­tion of the life cycle costs for the fans selected. As well as using the oper­ating point, it is also possible to perform selec­tion by way of the type desig­na­tion. The data sheets can be created in pdf format and show not only the nominal data of the fan but also the perfor­mance data at the spec­i­fied oper­ating point together with the suction and pres­sure side sound power levels over the octave band (Fig. 6). 

 

You can find more infor­ma­tion about the new RadiPac and the ILK report here.

Required fields: Comment, Name & Mail (Mail will not be published). Please also take note of our Privacy protection.