Wärtsilä has upgraded its LJX series of modular waterjets to deliver greater efficiency with low levels of cavitation and underwater noise.
The upgrade includes a new axial pump design to boost performance and thrust by around 3 per cent, while the improved cavitation margins reduce environmental impact by minimising noise. The axial waterjets are single stage, compact, and high performance to combine mixed flow properties with an axial construction. This reduces space needed on the vessel’s transom and increases waterjet cavitation margins by up to 35 per cent for operational flexibility of the vessel.
For naval architects, the axial jet technology creates the possibility to apply a larger power density onto narrower hulls in order to achieve maximum vessel performance.
Unlike a non-axial design, the Wärtsilä waterjet does not expand in a radial direction downstream. As the water flow is directed through the pump along the most efficient path, it is easier to fit the jet to the available transom space. The reduced transom size also decreases the weight of the installation significantly. These weight optimisations and savings can be as high as 20 per cent compared to non-axial jet designs.
The modular waterjets will be redesignated as the Wärtsilä WXJ series and aimed at various global market sectors, including high-speed ferries, frigates and other fast speed naval vessels, yachts, shallow draft vessels, large fast crew vessels, and large fast supply vessels.
The new WXJ pump has been tested extensively, both in computational fluid dynamic (CFD) simulation and with model testing.
Leendert Muilwijk, general manager product group waterjets, Wärtsilä, said: “We have been able to keep the notable benefits from the LJX-series, and the interface between the waterjet and the vessel remains identical to that of the LJX. Similarly, the small transom interface dimensions, and best in class weight are unchanged, but overall performance is now improved.”