Jet Impeller Opti­miza­tion for an Electric Hydro­foil Surf­board (efoil)

An electric hydro­foil surf­board (efoil) is a great expe­ri­ence if you want to try out new things that are related to surfing or kiting. Ve Concepts Inc. (AKA VeFoil) has been working on some­thing new and unique for the efoil vessels and sport with the focus on propul­sion safety. Chris Ver­meulen approached us for help with impeller design and opti­miza­tion, to boost effi­ciency and thrust while keeping the overall impeller diameter size small.

Chris’ unique focus on safety led him to design a jet-powered efoil where the impeller is com­pletely enclosed within the motor housing which elim­i­nates the risk of touching, kicking, or falling in the pro­peller blade. The fol­low­ing pictures show the impeller and the housing com­po­nents, as well as the control that the rider uses for the speed: 

His compact jet drive reduces parasite drag gen­er­ated by larger units uti­liz­ing ducted pro­pellers. What makes the VeFoil product so inter­est­ing is that a user can ride out and into swells and foil without the use of the motor for a true hydro foiling expe­ri­ence. Power free hydro­foil­ing also extends the ride time because constant power is not required. Here is a YouTube clip of his pro­to­type board in action: 

Para­met­ric Design and Opti­miza­tion of eFoil Jet Impeller

In order to optimize the impeller geometry of the electric hydro­foil surf­board, a fully para­met­ric model of it was created in CAESES. Based on an existing impeller geometry from our model pool, the baseline design was quickly remod­eled as a starting point for the opti­miza­tion pro­ce­dure. CAESES provides modeling capa­bil­i­ties for all sorts of blades and impellers, and for con­nect­ing these variable models to sim­u­la­tion codes.

In order to create a variety of dif­fer­ent impeller shapes, a set of design vari­ables was defined. They con­trolled para­me­ters such as the chord lengths, pitch angles, rake values etc. By automat­ing the design creation and the cor­re­spond­ing sim­u­la­tion process, one can readily use the inte­grated opti­miza­tion strate­gies in CAESES for running design explo­rations. For the sim­u­la­tion part, an OpenFOAM setup was linked to CAESES and helped to analyze the per­for­mance of the impeller. During the opti­miza­tion, the pressure and torque values of the gen­er­ated designs were mon­i­tored. Finding the optimal design was finally done through matching a target torque and RPM value, while max­i­miz­ing the thrust. 

Opti­miza­tion Results

The results were a surprise to everyone, i.e. to Chris who was hoping for rather small improve­ments through this opti­miza­tion, but also to our team since we have no track record and expe­ri­ence in opti­miz­ing hydro­foil boards. This is what happened:

• The power con­sump­tion of the efoil under the same tests dropped whopping 26.6%, com­pletely related to this impeller optimization.
• His efoil also increased its top speed to over 35 km/​h from 25 km/​h.

This is an amazing step forward in the product devel­op­ment process of this efoil, while setting up the opti­miza­tion took just a few hours. So, the entire CAESES team is now also eager to test the new pro­to­type in the next months: Chris, we are waiting for the invi­ta­tion to join your tests in Hawaii ;-) 

About Chris Vermeulen

Chris Ver­meulen is an entre­pre­neur, pilot, stock trader, and quasi-mechan­i­cal engineer. He has built several inter­est­ing things from taser/​stun gun, motor­bike w/​sidecar, and floating sand dredge to name a few. His passions are kite­board­ing, spear spearfish­ing and riding electric hydrofoils.

Related Posts

There is a related blog post about gen­er­at­ing pro­peller blades for another efoil surf­board. Check out the appli­ca­tions section for other impeller and pro­peller applications.