Siem Curie as the only ship in SIEM Ship Management is equipped with a unique system called “Grim’s vane wheel” which ensures improvement in required power (5-10%), exceeding the fuel savings that can be expected from most any other ESDs.
Grim vane wheel is located immediately behind the propeller. The vane wheel blades have turbine profiles in this inner section whereas they have propeller profiles at the outer blade section. In the turbine section, kinetic energy is taken from the propeller slipstream, which is directly transformed again within the propeller section into an additional thrust. The main function of the vane wheel is to extract energy from the propeller slipstream in the turbine portion and convert this energy into additional thrust in the propeller portion.
This propulsion system has the following hydrodynamic advantages over normal single-propeller drive:
- Substantial recovery of rotational energy.
- Greater possible jet cross-section of vane wheel, since the low rpm rate and large number of blades enable smaller vertical clearances to be accepted.
- Less resistance from rudder behind the vane wheel. This is reflected in the relative rotative efficiency.
- Better stopping capability.
Moreover, the higher rpm rate associated with the smaller diameter of the engine-driven propeller improves the weight and cost of the propulsion unit.