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counterrotating screw propeller /contra prop / contrarotatif
This article provides an example design of a pair of contra-rotating propellers with software HELICIEL counterrotating propeller is used

stator en amont d'une turbine

For completeness, the Heliciel software must enable the design of contra-rotating propellers, incorporating a parameter tangential flow upstream ...explanation:
The counterrotating propeller consists of two counter-rotating propellers:

contra rotatif

The first propeller is optimized as a normal propeller.We therefore use héliciel to calculate and create a normal propeller.

For example we will use (let's open a model of air proppeller and set parameters):

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The second propeller, which is located downstream, will receive a diverted fluid stream (tangential component) and accelerated (axial component) by the upstream propeller. The second propeller must therefore be twisted, and pitch optimized with fluid parameters speed, different from the first. It will of course also have a reverse rotation. To create our downstream propeller, we will use the results of our upstream propeller to determine the fluid velocity at the inlet and the tangential component parametrer:
In the results area, from our upstream propeller, at the element at around 0.75 times the radius of the blade (element 4) (most effective area of the propeller), we note the downstream axial velocity: 60.2 m/sec (ce sera la vitesse fluide de notre seconde helice) et la vitesse avale tangentielle:7.7rad/sec (ce sera la valeur de l' introduction de flux tangentiel de notre seconde hélice)

vitesse tangentielle en aval de l'hélice

After you have saved our upstream propeller, we transform it, to downstream propeller by changing the fluid velocity from 56 m/sec to 60.2 m/sec, because it is this axial speed that receive our downstream propeller.

helice aval contrarotative

The propeller also diverted upstream flow, in rotation,we will use the parameters menu / introduce tangential flow, to enter our value of 7.7 rad / sec previously noted. Note that the value of the tangential flow introduced must be negative, in our case, because it is contrary to the direction of rotation:

introduction vitesse tangentielle helice contra rotative

We have to rebuild with this new data, to calculate the twist and the performance of our downstream propeller:

helice contrarotative avale

We reverse the direction of rotation in the 3D tab to rebuild an inverted geometry before export to a cad to igs formats

 

the thrust forces, of the upstream and downstream propeller, will be cumulative, as well as their torque to the shaft and power, if you want to know the power, torque and total thrust from our counterrotating propeller. The efficiency can sometimes exceed 1 at the downstream propeller, because it is calculated without taking into account the contribution of the tangential flow of energy that is brought​​, and thus gives a surplus of abnormal power. But the average efficiencies of the two propellers will give us an overall efficiency therefore more realistic and less than 1.
The design function of contrarotating propellers, has been made ​​possible by the ability to parameterize a contribution tangential flow upstream of the propellers. This also allows the calculation of rotor stator pairs ... This feature is in beta, feel free to send me your comments to improve it..