Propellor tunnel design
1. Optimum flow into the propeller
A Servogear propeller tunnel is designed in accordance with propeller momentum theory, to secure optimum water flow through the propeller. The shape of the tunnel, from the propeller to the stern, is designed according to the contraction of water flow calculated from propeller momentum theory. For every project, the tunnel design is tailor made to ensure the optimum result.
2. Optimum propeller diameter
Normally, the propeller diameter is limited by the tip clearance and the draft.
The Ecoflow™ propeller tunnel provides space for the optimum propeller diameter, while maintaining an acceptable inclination of the shaft. The larger the diameter of the propeller, the higher the reduction of axial losses, while a lower speed of rotation combined with the superior finish of a Servogear Ecoflow™ propeller means lower frictional losses.
All together, this is very favourable for high propulsion efficiency, while ensuring low levels of vibration and noise because of the reduced surface pressure and tip speed on the propeller.
3. Reduced shaft angle
The propeller tunnel also minimises the shaft angle, and reduces the thrust variation on the propeller. This again reduces the peak load on the propeller, and in doing so increases the lifespan of the equipment significantly. The minimised shaft angle also helps to reduce drag caused by the shaft and brackets, etc.
4. Reduced ship resistance
Based on extensive experience gathered from sea trials and model tests, Servogear found that a well designed propeller tunnel significantly reduces ship resistance. This is achieved through the use of a smaller transom area, which in turn helps to reduce loss in stern wave energy.