Warships widen market for medium speed engines

Increasing interest by navies in medium speed engines for propelling destroyers, frigates, corvettes and aircraft carriers as well as for genset drives is reported by MAN Diesel.

Since the end of the Cold War the role of many navies has changed, explains Ralf Losch, head of sales for naval and governmental marine applications at the German group’s headquarters in Augsburg.

“Where specifications used to revolve around the defence of well-defined ideological blocs and involved patrols and sorties of limited duration from a homeland base, naval forces now are much more likely to be engaged in missions of longer range. These centre on tasks such as trade route protection, economic or military blockades, exclusion zones, smuggling and illegal immigrant protection, humanitarian aid, anti-terrorist measures and peacekeeping.”

Under these long-endurance operating conditions, he claims, the virtues of MAN Diesel medium speed engines – such as robustness, high availability and excellent operating economy and emission levels – replace speed and acceleration as prime operating requirements.

“In typical medium speed naval or commercial marine applications, the effective life of engines is likely to be counted in decades rather than years. As a result, MAN Diesel builds considerable development potential into its new engines and retrofit capability into new technologies like common rail fuel injection and advanced turbocharging systems.”

MAN Diesel’s high power density/1,000 rpm series 28/33D engine, he asserts, is designed to meet the demands of patrol vessels, destroyers, frigates, corvettes and aircraft carriers, including those with CODOG or CODAG combined prime mover propulsion systems.

Production of the former Ruston 280mm-bore design has started at Augsburg, a programme of V12, 16 and 20-cylinder models covering a power range from 5,400kW to 9,000kW. A sequentially turbocharged version, the 28/33D STC, will be available to enhance the field of application.

In conjunction with electronic fuel injection technology, the STC system is said to significantly extend the engine’s torque envelope in its mid-speed and load ranges. Among the cited benefits are excellent engine response and vessel acceleration, improved reliability due to reduced thermal stresses and better manoeuvrability because of faster load acceptance. In addition, economical operating modes are facilitated, including using a single engine at very high torque in systems with twin input/single output gearing or CODAD, CODAG or CODOG systems.

For larger fighting vessels, MAN Diesel is increasingly responding to enquiries for its medium speed engines. The needs of extended missions far from home bases include operating profiles with long-term running at low load, a doubling of annual operation to as many as 5,000 hours, a quadrupling of availability in the deployment area, radii of operation up to 4,000 nautical miles, and intervals of two years without docking for maintenance or refit.

“These needs translate into the extended service intervals and long times between overhaul typical of medium speed engines like our 32/44CR,” says Mr Losch.

MAN Diesel’s first all-electronic four-stroke engine, the 320mm-bore design, was also the first medium speed engine to be offered exclusively with common rail fuel injection. Yielding a class-leading output of 560 kW/cylinder, the series spans a power band from 3,360kW to 11.2MW with 6-10L and V12-20-cylinder models. An MAN-developed SaCoSone electronic control system manages the engine, the complete propulsion train and all peripheral equipment.

The 32/44CR engine is described as suitable for both fighting ships and logistical support tonnage, such as amphibious force carriers, replenishment cargo vessels and tankers. Its benefits can reportedly be realised equally in both propulsion and power generation applications, along with the flexibility to burn any commonly used heavy or distillate fuels.

Naval references for another MAN Diesel contender, the SEMT-Pielstick PA6B STC high speed design, were extended last year by twin V12-cylinder engine packages for four Horizon-class frigates: two for the French Navy (Forbin and Chevalier Paul) and two for the Italian Navy (Andrea Doria and Caio Duilio). The 4,340kW engines provide the 153m-long/6,000-tons displacement vessels with a cruising speed of 18 knots.

MAN Diesel also targets opportunities for supplying diesel engines to submarine projects. Some 230 Pielstick PA4-series high speed engine-driven gensets with an aggregate rating of 160MW are serving 120 conventional submarines. Among recent references were sets for 25 Daphne and 13 Agosta-class boats for the French, Pakistan, Portuguese, South African and Spanish navies.

With its flanged-on generator, the PA4-200 diesel engine is supplied as a fully integrated, load-bearing frameless package for battery charging and power supply. The compact 200-mm bore/210mm-stroke design is offered in V8- and 12-cylinder SM configurations to cover an output range from 700kW to 1,050kW at 1,300 rpm. An output of 1,330kW at the same speed is offered by the 12PA4-200 SMDS model. MP