The heat required for the water vaporisation comes from the air compressed by the turbocharger and partly by the water preheated through heat rejected by the engine (exhaust gas or jacket cooling water). The water is introduced in a large vessel, developed by a Swedish Company named MUNTERS, through a net of injectors, and water droplets are separated from the humidified air by water separators. This excess water is then recirculated in a closed loop as shown on figure 15. As the vaporisation process cools down the air, there is no more need of an air cooler in the turbocharging system.

　

Fig.15 - HAM system

　

Such device called Humid Air Motor (HAM) has been extensively tested on the 3-cylinder PC2.6B engine. A first industrial application was started in July on a 12PC2.6 engine of M/S Mariella, a car ferry of Viking Line (Fig.16) where the NOx reduction amounts to 70% and even more at part loads. During inspection of cylinder component made at regular intervals (i.e. after 1200, 2400 and 3500 running hours), an excellent condition of pistons, pistons rings, liners and valves has been found.

　

Fig.16 - M/S Mariella

　

As the water used is sea water, the operating cost is almost negligible which makes this system most cost attractive when compared to a classical SCR (Selective Catalytic Reduction) system using ammonia or urea (Tables 1 and 2).

Investment cost: 15 years amortisation with an Interest rate of 2.5%

= Annual cost: 8.08% of the capital

Operating profile: 6000 h/year at 80% MCR

NOx reduction: 70% (14 g/kWh without treatment)

Investment (supply + installation):

- HAM: 80 $/kW

- SCR: 55 $/kW

Operating Cost (consumables + maintenance):

- HAM: 0.01 $/kg Nox reduction

- SCR: 0.29 $/kg Nox reduction

Table 1 - HAM/SCR cost comparison - Hypothesis

Table 2 - HAM/SCR cost comparison - Results

　

5. PC ENGINES IN JAPAN

　

PC engines have been manufactured for many years by Diesel United Ltd., NKK Corporation and Niigata and have been very popular in the domestic ship propulsion market.

A survey of all ships, above 1000 GT and with more than 4000 hp, registered in Japan since 1960 shows that 60% of the total installed power amounting to 4,546,000 hp is produced by Pielstick engines. The remaining 40% is split between other medium-speed engines (28%) and slow-speed engines (12%). The corresponding types of ships are: ferries (2/3 of the total installed power), cargoes (including Ro-Ro), cruisers, coast guards and special purpose ships.

When looking at the evolution of the Pielstick engines, in the market (Fig.17 and Table 3), we can see that this share has been constantly progressing and that it went to 78% over the last five years, the remaining 22% being distributed between other medium-speed (15%) and slow-speed engines (7%). This is the best proof of the confidence given by Japanese shipowners in the reliability of the Pielstick engines in spite of cylinder power ratings, which keep increasing step by step over time.

　

Fig.17 - Distribution of diesel engines installed on ships registered in Japan

　

Table 3 - Ships registered in Japan

　

　

　

BACK　　　CONTENTS　　　NEXT