EfficienSea | Matthieu Michou, Camille Letetrel
Established in 2018, we focus our work on the design of marine propellers. Our applications range from hydrogeneration turbines to propulsion propellers, in open-water or nozzle and even sometime in tube.
Our propellers are used on a large scale and on the most demanding application : for example the fleet of IMOCA racing monohull rely for their energy on various shapes of hydrogeneration turbines designed by us, where we made our best to maintain a low drag with high energy output.
We have developed our own in-house codes to answer the problematic of design of marine propellers. The first motivation was to develop our own propeller turbines for racing sailing boats.
VLM design code : written in Julia and based on various PhD Thesis about the optimisation of propellers with the Vortex Lattice Method, we have a very specific knowledge brick to manage the case of the hydrogeneration case : that is the optimization of propeller for energy harvesting versus its drag.
This tool and underlying theory is however versatile and can handle the more common propulsion case where the Thrust is specified and the Torque has to be minimized.
With changing the fluid parameters, we are able to design efficient propellers for other fields of application, for example for small-scale wind-turbine
Coupled cavitation / load design process : our workflow evaluates cavitation and blade constraints at each design iteration. This is very valuable for multi-parametric optimization process as it ensures that all the designs comply with same cavitation and load constraints and thus are comparable.
Multi-parametric optimization is useful to check the impact of all main parameters governing a propeller design :
– diameter
– number of blades
– rotation rate …etc.
3D geometry generation : based on a work to redefine the NACA sections into modern NURBS definitions, we are able to generate smooth and CAD-friendly shapes with good curvature continuity. This revealed mandatory to be able to alter the final shape ( e.g. to add fillets at the root ) in a robust way and allow automated CFD optimization.
CFD validation : we have developed a specific workflow with OpenFOAM solver to compute any propeller shape in open-water conditions. Some of our propellers have been tested in towing tanks allowing to check the accuracy of design and computations.
CFD optimization : we are able to run optimization sets on specific parameters to maximize the efficiency and account 3D flow effects
Global optimization : propellers are not intended to work alone and not always at the same operating point. That’s why we have developped skills to run global optimization processes. Including motor / generator efficiency map, or usage scenarii, we are able to design a propeller that will outperform globally on its use, not only for a specific case.
We’ve recently designed a customized propeller for naval architects L2O naval Their project is a hybrid sail + electric boat that carries passengers on regular lines in Brittany. Since the boat is battery-powered, a propeller optimization has been carried to outperform the best available traditional B-series propeller. The gains are following : Cavitation maps comparison …
Continue reading “Electrical passengers boat propeller design”
After validation of performance of a first prototype machined in aluminium for SV GRAIN DE SAIL 2, we designed a second iteration of propeller according to bronze properties. Since it has much more strength than aluminium, bronze alloy allows thinner blade sections and an increase in performances. It helps to reduce tip cavitation as well. …
Continue reading “Hydrogeneration propeller design for sailing cargo : second iteration”
We designed a large scale propeller for a hydrogenerator for the sailing cargo Grain De Sail 2. The goal was to minimize the drag while producing the requested power and maintain a low cavitation despite the proximity of water surface We designed the propeller geometry which was successfully tested on a transatlantic trip France –> …
Continue reading “Hydrogeneration propeller design for sailing cargo ship”
https://www.sciencedirect.com/science/article/abs/pii/S0029801821011872
The energy ship is a new concept for offshore wind energy capture. It consists of a wind-propelled ship that generates electricity using water turbines attached underneath its hull. Since it is not grid-connected, the generated energy is stored aboard the ship (for instance, using batteries or through conversion to hydrogen using an electrolyzer). This concept has received little attention until today. Particularly, there had not been yet an experimental proof-of-concept. In order to bridge this gap, an experimental platform has been developed at Centrale Nantes. It consists of a 5.5 m long catamaran equipped with a 240 mm diameter water turbine. The platform was tested in July 2019 on the river Erdre (France). Results show that a full-scale energy ship could deliver high levels of power production (megawatts); and that it is essential to optimize the water turbine induced drag in order to maximize energy production.
