ABB: Dual Rating Configuration for A100-L

ABB Turbocharging reported two achievements with turbochargers from the A100 family.

The first A100 achievement is a new efficiency record. In final testing of the A190-L turbocharger for two -stroke low speed diesels, ABB technicians measured peak efficiency at 75.8%. “The 75.8% figure is all the more impressive because it was measured on a turbocharger featuring a higher pressure ratio than the model that achieved the previous record figure,” said Urs Gribi, Vice President of Engineering at the Baden, Switzerland headquarters of ABB Turbocharging. 

In the second A100 landmark, ABB Turbocharging’s application engineers have devised a new A100-L turbocharger configuration for slow speed engines which facilitates rapid conversion from a higher power output matched to a ship’s normal cruising speed to a lower rating matched to a slower fuel saving speed – i.e. “slow steaming”.

The concept developed by ABB Turbocharging is devised to meet the “dual rating” engine specifications of a series of 10 containership newbuildings contracted by NOL. It takes advantage of the very wide compressor maps of the A100-turbocharger to achieve this aim by varying the number of turbochargers in the engines’ exhaust gas stream rather than by fitting new turbochargers, modifying the internal components of existing turbochargers or using techniques like variable turbine geometry to vary turbocharger air delivery characteristics.

In detail, the ABB system adopted for the new container ships is designed to allow the ten, 12 cylinder 98 cm. bore low speed two-stroke diesel to achieve ratings of  just over 72 MW at 104 rpm or just over 54 MW x 97 rpm. The solution comprises four A190-L turbochargers, one of which can be cut-off from the exhaust gas stream. This is achieved either via a motorized valve or a simple blanking plate. In spite of the reduced level of energy in the engine exhaust gases due to the lower engine power rating, the A190-L’s wide compressor maps allow the three turbochargers still in the exhaust gas flow to efficiently produce charge air at the pressures and volumes needed for the lower engine slow steaming rating.

“Substantially modifying the compressor map of a turbocharger can involve the exchange of many of its internal components,” notes ABB’s head of global turbocharger sales for the low speed engine segment, Arie Smits. “In the extreme case this can mean the turbine and compressor wheels as well as the nozzle ring and diffusers. In any event, the turbocharger has to be opened, dismantled and reassembled. But with the A100-L’s excellent compressor maps it was possible to achieve dual ratings with optimized fuel consumption by, essentially, only reducing the number of the turbochargers providing combustion air to the engines.”

ABB Turbocharging’s A100 turbochargers combine very wide compressor maps while offering high pressure ratios of 4.7 and above in the A100-L versions for low speed two stroke engines and 5.8 in the A100-M and A100-H versions for medium and high speed engines.