Development continues as sales pick up

Recently the market for waterjets has undergone something of a depression.

The uncertainty in the ferry market caused by the abolition of duty-free sales, and the recovery lag following the economic downturn in the Asian economies, combined to depress sales of waterjets last year. Hans Yansson, marketing director for Kamewa, says the company is seeing only 30 per cent of the sales level of two years ago. Although it is still too early to make predictions of a recovery, the company reports some important deals signed in the first couple of months of this year.

In March Rolls-Royce, which acquired the company along with the Vickers Group in November, announced that it is to supply the largest Kamewa water jets yet developed for a fast monohull ferry being built by French shipyard Chantiers de L?Atlantique for NEL Lines in Greece. Delivery is scheduled for late 2000 and they are due to be operational by the summer of 2001. The two 200cm inlet diameter waterjets are each powered by a 25,000kW (33,512 bhp) gas turbine, while the two 140cm units are each powered by 8,100kW (10,858 bhp) diesels. The ship is 140m long and has a service speed of 37.5 knots.

The yard is also building a 100m vessel to be propelled by three Kamewa 125 SII waterjets powered by three diesel engines, each of 8,100kW (10,858 bhp). Its service speed will be 35 knots.

Investment in research

Anders Petterson, communications manager at Kamewa, says that the company is investing heavily in waterjet research and development at its hydrodynamic research centre, and predicts that there is still a way to go regarding vessel speeds. “Today there are large high-speed ferries equipped with Karnewa waterjets operating at speeds close to 60 knots, and there are ongoing projects and tests for considerably higher speeds,” he says.

Lips Jets is also seeing a trend toward larger and faster vessels using waterjets, coupled with a downturn in activity over the past two years compared with 1996/97. “However we expect the market to revive from 2000,” says Mr Kruyt.

Lips Jets markets waterjets based upon two different pump designs. The recently developed six-bladed model combines high efficiency with a cavitation margin which, says Lips, allows for a compact and light installation, making it suitable for relatively high ship speeds. As an alternative, Lips Jets offers a three-bladed waterjet designed for use at relatively low ship speeds. The cavitation margin characteristics of this more axial-flow type of pump results in a slightly larger installation, says Lips.

Niche market

Nils Morén, sales manager at MJP, sees waterjets as very much a niche market item. They are most suited to: “Vessels requiring high speeds, shallow draught, protected propulsion, high manoeuvrability at all speeds, low noise emissions for military applications and low vibration,” he says. The company has introduced a new hub unit design, which says Mr Morén, is stronger than the previous unit and allows service access from aft. He says it has improved the pump geometry and increased the efficiency of the jet.

Low speeds

High-speed waterjets acting as axial water pumps are not the only units on the market. The Schottel Pump-Jet (SPJ) is a low-flow-rate waterjet designed for low ship speeds of up to 12 knots in shallow water operation.

The SPJ operates on the principle of a centrifugal pump. An impeller sucks in water from under the hull and forces it into a pump housing. The outlet nozzles are fitted in the bottom plate, making it possible for the jet to be installed in a flat-bottomed hull.

The company says it has improved the efficiency of the SPJ by using larger flow areas while keeping the outside dimensions the same. This was achieved with the development of a new ring diffuser system. This replaces the previously-used impeller and converts kinetic energy into pressure energy. This is done by continuously increasing the cross-section of the flow channel, a process which is carried out three-dimensionally, both radially and axially. A new nozzle geometry was developed with the aim of maximising the nozzle in a minimum space and giving the unit a shallow outlet angle. With the outside dimensions held constant, the flow cross-sections could be increased by approximately 47 per cent, says Schottel.

New materials

Kurt Scholz, public relations manager at Schottel, says that the company is doing continuous development work with new materials in order to reduce the unit?s weight. Last year it carried out tests on an impeller with carbon fibre blades.

However, emissions regulations applied to the propulsion plant of waterjets could have a derogatory effect on efficiency says Mr Scholz. “These regulations will reduce the torque safety of the engines or the reserve for overload or partial load,” he predicts. “For special operating conditions the torque reserve will be lower than today. Propellers and impellers will be designed for lower torque absorption and higher revs/min at the same power. That results in reduced efficiency for normal operations.”

Bigger and faster

With order books beginning to pick up, a cautious note of optimism is beginning to enter the waterjet industry. No one is making any bold predictions about recovery, but it could be that the worst is over. The move towards ever larger units producing as much as 50MW (67,025 bhp) of propulsive power and with operating speeds being pushed ever higher, new market sectors are set to open up for the technology. Also, the high efficiency of waterjets will give them a head start in the race to reduce emissions from propulsive plants.

Improving the public image

Australia?s high-speed ferry builders suggest that a public education campaign may appease concerns that water jet-powered ships may threaten the marine environment.

For the fast ferry industry, which builds vessels that travel at more than twice the speed of conventional ships, water jets ? or the surface piercing super-cavitating propeller ? often win favour above conventional propellers.

Larger builders in the vehicle-carrying sector claim that a greater public awareness may become increasingly important with the “inevitable rising demand” for high-speed craft powered by water jets.

In enumerating the virtues of this type of propulsion, Tasmanian builder Incat espouses that water jets offer a superior solution for night speed operation and rapid manoeuvring in a harbour.

Also, unlike a conventional ship?s propeller, the water jet?s enclosed impeller can provide more thrust for a given diameter because energy is directed radially off the tips and redirected to increase the thrust.

The pump?s body is enclosed in the ship, creating an absence of external parts to cause drag, thereby allowing the fast ferry to operate in shallower water than a conventional ship.

Better cavitation performance enables the water jet to provide more thrust at a faster rate, enabling the vessel to reach its cruising speed quicker than a conventional ship.

Austal Ships, which made headlines with record-breaking speeds achieved with Villum Clausen in Denmark, cited similar advantages.

When asked the extent to which these companies felt emissions regulations would impact on future designs in respect of the propulsion plant, both Incat and Austal were circumspect about stating their public position.

However it is clear the issue has potential to be a nagging source of vexation.

Incat?s position is that it intends to abide by the regulations set, and it believes they will have a minimal impact on future design expectations in relation to the propulsion equipment.

On the other hand Austal, which supplied the 86m Villum Clausen, powered by gas-turbine four Kamewa 112 S11waterjets , became “intimately familiar” with the restrictions the industry is likely to encounter in the coming years when complying with the Danish administration.

The builder?s experience in complying with the world?s most stringent environmental regulations could present a sign of things to come for ferry operators as the world?s legislative authorities strive to promote a “clean green image.”