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November 2010 www.marinelink.com 83 firm the system’s suitability for highly flexible valve timings on 4-stroke en- gines. VCM is an ideal complements ABB Turbocharging’s Power2 two stage turbocharging system as enabling tech- nologies of Miller Cycles on four-stroke diesel and gas engines. On diesel engines, strong, variable Miller Cycles hold the prospect of attaining the 80% reductions in NOx emissions specified by IMO Tier III limits for Emission Control Areas using only primary, on-engine measures. VCM allows inlet valve timings to be varied at lower engine loads to avoid in- creased emissions of smoke and particu- lates and higher thermal loading, as well as improving engine response, idling and starting. VCM is also a versatile and valu- able tool for closely adapting engine per- formance to the operating profile of a given engine application. Variation in valve timing and lift is achieved by interposing a high pressure oil chamber into the engine valve train between the valve and its mechanical ac- tuation system. A solenoid valve varies the filling of the chamber with engine lube oil pressurized by a camshaft actu- ated pump. This enables both the timing of the opening and closing of the valve to be varied as well as the distance the valve opens (valve lift). The pump also feeds a brake unit above the valve to limit forces when the valve contacts its seat. The VCM system varies valve timing and lift by interposing a high pressure oil chamber into the engine valve train. HamiltonJet Reports HT Orders Strong HamiltonJet reports that it has had success with its new HT series since the first model was introduced less than two years ago with 60 units being sold to date. So far 18 HT1000s have been delivered to South Korea for Coast Guard Patrol boats, with a further 10 jets scheduled for delivery this financial year. A large patrol boat being con- structed in the U.S. at present also uses twin HT1000. Seven twin shipsets of HT810s have been ordered for patrol boat projects in Taiwan with the first of these recently exceeding expectations at sea trial. Already there are orders for 16 HT900s for four fast supply vessels being constructed in the U.S.
