MAN Diesel celebrated 75 years of turbocharging technology in 2009. First patented in Germany in 1904 by Alfred Büchi, the new technology was embraced by the Augsburg, Germany, engine manufacturer in 1934 for its four-stroke units. MAN Diesel has realized several technological milestones in these 75 years — the adoption in 1940 of plain bearings inboard the rotor shaft, or the design of its first radial-flow turbocharger in 1955, for example. In later years, MAN Diesel introduced its new axial turbocharger generation TCA in 2001 and its new radial turbocharger generation TCR in 2004.
This year marks another important milestone for the company with the introduction of the new TCA33 axial turbocharger for high-speed engines, the smallest turbocharger in MAN Diesel’s axial range. The new model has been specifically designed for the newly uprated MAN Diesel V28/33D engine, using a two-turbocharger configuration. Asingle frame size will fit the 12V-, 16Vand 20V28/33D engines, with common interfaces across all ranges. There is a smaller rotor version for the 12V and 16V units, and a larger rotor for the 20V.
Emanuel Bölt, turbochargers project manager, explained that the new TCA33 benefits from the technologies of the existing TCA and TCR series, and uses as many common components as possible. “In particular, the compressor side derives more from our radial range, with the same shaft-fixing arrangement,” he said. “The unit reaches a 5.2 pressure ratio, fulfilling the IMO Tier 2 emissions limits, and we utilized specific compressor wheels.”
MAN Diesel also revealed that the introduction of a compressor pressure ratio of 5.8 is in development phase for future engine generations. Bölt clarified that, despite the special compressor wheel design, the high pressure ratio still brought problems with high temperatures in the compressor wheel. “The use of titanium to overcome these problems was ruled out because of the high costs and other technical disadvantages. We decided then for a completely different approach and introduced water cooling in the region of the sealing plate, behind the compressor wheel,” added Bölt.
The cooling system is integrated with the engine, so the temperature problem was solved with a minimum of complexity. As far as the turbine side, the TCA33 derives some features from the other TCA turbochargers, but with a design aimed at the integration with the V28/33D engine. “The angled turbine inlet casings are designed to match the engine exhaust. As the configuration on the V28/33D engine is for two turbochargers, each unit uses the same inlet casing, which is simply rephrased to the opposite angle,” said Bölt. He emphasized that the turbine outlet casing was also newly designed, resulting from the requirement of the engine package to fit compact ship engine rooms. The rectangular profile of the TCA outlet casing was adjusted to reduce its width and then provide a direct connection to the round exhaust system. This was achieved with very low pressure losses in the connection itself and in the downstream exhaust duct. To allow flexibility in installation, Bölt also added, “The gas outlet casing can be indexed by 15° angle increments, and the compressor casing can be adjusted to any angle.”
Although the TCA33 model was developed specifically for the V28/33D, MAN Diesel anticipates the potential for other applications. “The TCA33 is mar ketable for engines with a power output between 3000 and 5000 kW, potentially also by other engine builders,” said Jörg Albrecht, head of sales, MAN Diesel turbochargers. According to Albrecht, the product is well suited for sequential turbocharging applications and is ready for the company’s variable turbine area (VTA) technology.
The next step at MAN Diesel is to obtain comprehensive validation of the TCA33 in the test rig and on a laboratory engine. Three prototypes have been delivered for rig testing in the Augsburg headquarters, and for engine testing in the French plant of St. Nazaire. After that, the V28/33D engine, with its new turbochargers, will undergo field testing. At the moment, it looks like the first application of the new engine/turbochargers package will be on a new catamaran by Australian shipbuilder Austal, which has been ordered by the Denmark-based Nordic Ferry Service, for the vehicle-passenger route between Rønne, Denmark, and Ystad, Sweden.
The new 113 m vessel will be powered by four MAN Diesel 20V28/33D engines, each with two TCA33 turbochargers that will allow a pressure of up to 500 kW per cylinder. The four engines will deliver 9100 kW at 1000 r/min, for 100% maximum continuous revolution (MCR). These engines also have an overload capacity for a limited time: 10 000 kW at 1032 r/min for a maximum of one hour every six hours.
The whole 28/33D family has been improved in design and boosts a limited overload power output of 6, 8 and 10 MW for the 12-, 16- and 20-cylinder versions, respectively. Besides the TCA33 turbochargers, these new units feature an engine mounted SaCoSone safety and control system. Optimized crankshaft design, injection system and combustion chamber all contribute to reaching a very high power density, while at the same time complying with IMO Tier 2 emissions limits. These goals were also obtained by the increased use of Miller cycling, a high-efficient charge-air cooler, and an improved NOx/SFC/soot tradeoff.
The Technical Manager/COO of Nordic Ferry Services, Bent B. Hansen, said, “Service and reliability are keywords for our company. For the Rønne-Ystad route, built-in surplus power was a must, and the new vessel by Austal will deliver that without incurring large increases in fuel consumption or maintenance costs.”
On the specific performance of the MAN Diesel engines with new TCA33 turbochargers, he said, “We feel comfortable with the guarantees that MAN Diesel has given us regarding the running of the engines. Even though, from a technical point of view, you could say that an order has been placed for four engines that, as of yet, have not been type approved.” Sounds like a nice declaration of faith in the capabilities of MAN Diesel.