For more efficient engine operation, MAN Diesel & Turbo wants to bring two-stage turbocharging to the marine market. While the new Ecocharge systems, MAN’s two-stage turbocharging technology, are still being tested in power generation applications, the company is certain about their marine future
Two-stage turbocharging is not a new technology, that is for sure. Back in the 1970s MAN Diesel & Turbo first[ds_preview] started to experiment with two-staged systems but stopped the programme because the low-pressure ratios were just not sufficient for an effective use.
In the early 2000s, the company started the two-stage turbocharging programme over. The first serial product was a modular high-pressure and low-pressure two-stage turbocharging solution, a combination of the well proven TCA88 and TCA77 turbochargers on the 18V48/60 TS engine. The new system reached peak turbocharging efficiencies beyond 75% at maximum pressure ratios of around 6. A significant improvement compared to the single-stage turbocharged engine. At a constant specific fuel oil consumption (SFOC) the output per cylinder increased by 14%. Alternatively, at constant output per cylinder SFOC is reduced by 3,4%.
»To fully exploit the potential of two stage-turbocharging we needed a new turbocharger to reach pressure ratios beyond 10 bar«, explains Daniel Albrecht, responsible project manager at MAN Diesel & Turbo. Thus, in MAN’s Ecocharge project, the TCX series has been developed as a dedicated high-pressure stage. The new Ecocharge system supplies engines with improved scavenging air pressures ranging from 5 to well above 10 bar, as well as significantly improving turbocharging efficiencies.
With the new product series the company has developed a turbocharger especially suited for two-stage turbocharging of four-stroke engines, running on HFO or gas. The charge air pressure can be increased substantially. The result is higher power density and, in conjunction with an advanced Miller cycle, reduced exhaust emissions and lower fuel consumption – a requirement that becomes more and more important as pressure through new environmental regulations and emission control areas grows. Additionally, because of the current market situation, owners are interested in lowering their fuel bills.
An in-line set-up of the TCR/TCA for the low pressure-stage and the new TCX for the high-pressure stage increases efficiency through reduction of the compression work via two-stage compression with intercooling. The reduction of thermal stress is also beneficial for the whole system.
»We need a practical field test«
MAN Diesel & Turbo’s latest 35/44G TS gas and 32/44CR TS diesel engines, both available as 12V and 20V, were chosen for the first serial application of the Ecocharge system. Both new engines first of all target the power market, Albrecht says, but he adds, »We need a practical field test. We need to know that it works before putting it on a ship.« But at some point the engines will be available for the marine market. Also Josef Dorner, Sales Support for Power Plants, backs that view, »We are building experience that will support the introduction of two-stage turbocharging in the marine market.« That will mean a minimum risk for marine applications, Dorner adds.
Moreover, MAN tries to widen its market aiming at smaller engines. The experts are working on expanding the TCX program to high-speed engines that benefit from the technology especially at long running times. »Maybe this isn’t suitable for auxiliary engines, but for propulsion also in diesel-electric set-ups this will be the standard technology of the future,« the project manager is convinced. For the high speed segment the marine testing is already under way.
