Application of a Large Hybrid Turbocharger
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Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012) 29 Application of a Large Hybrid Turbocharger for Marine Electric-power Generation YOSHIHISA ONO*1 KEIICHI SHIRAISHI*2 YUKIO YAMASHITA*3 The function of our new marine hybrid turbocharger, which has a generator on its rotor shaft, is to supply electric power for consumption onboard a ship and to supercharge the ship’s diesel engine. The generator is driven by the turbocharger shaft, which is rotated by exhaust-gas energy; thus, the generator is an exhaust-heat-recovery device, and energy savings can be expected. A high-speed, high-efficiency, small, high-power generator is required. Mitsubishi Heavy Industries, Ltd. (MHI) has developed the hybrid turbocharger MET83MAG for a large marine diesel engine in collaboration with Nippon Yusen Kabushiki Kaisha (NYK Line), the Monohakobi Technology Institute (MTI), and the Universal Shipbuilding Corporation and installed it in a Capesize bulk carrier. This is the world’s first practical application of a large hybrid marine turbocharger. |1. Introduction A turbocharger consists of a single-stage turbine and a compressor on a shaft. The compressor is driven by engine exhaust gas directed to the turbine, and it supplies pressurized air for combustion to the engine. With recent increases in the efficiency of diesel engine turbochargers, sufficient air can be fed to the engine with partial exhaust-gas capture for electricity generation. A practical use of this technology is for a waste heat-recovery system, feeding approximately 10 % of the exhaust gas to a power turbine to drive the generator. An electric power-recovery system with a generator directly connected to a turbocharger was developed in 2009 by Mitsui Engineering & Ship Building Co., Ltd., using a large turbocharger.1 Our hybrid turbocharger comprises a generator in the turbocharger body, but it only needs a space as wide as a conventional turbocharger and requires only small changes to a conventional diesel engine. The turbocharger can be used as a generator and also as a motor through the application of bidirectional frequency converters. We reduced the size of the generator and designed it to fit inside the turbocharger structure to realize these functions. The turbocharger was installed onboard a ship, and operations were started after successful completion of a turbocharger engine-matching test and sea trials. This report describes the electric power generation effect on the engine performance when the turbocharger is coupled to the engine as well as the results of official trials. |2. Advantages of Our Hybrid Turbocharger A hybrid turbocharger integrated with a generator uses exhaust-gas energy at the turbocharger inlet port to generate electricity, just as a conventional gas power turbine does. However, compared with a conventional power turbine, our hybrid turbocharger has the following advantages: *1 Marine Machinery & Engine Division, Power Systems *2 Manager, Marine Machinery & Engine Division, Power Systems *3 Nagasaki Research & Development Center, Technology & Innovation Headquarters

Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012) 30 (1) Only a few modifications to the engine are required to install the turbocharger, and retrofitting is relatively easy, resulting in only a slight increase in the external dimensions because exhaust-gas piping and valve controls are not required. (2) The system is free from thermal and piping losses, and the turbocharger turbine provides high efficiency. (3) The turbocharger can be accelerated by utilizing the generator as a motor. The power output of the resulting three-phase alternating current (AC) electricity...

Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012) 31 frequency recovered to 1% or less of the rated frequency within 5 seconds. In the temperature-rise test, the temperature at each part was verified to be within the designed values at an environmental o (atmospheric) temperature of 35 C. Figure 3 Results of the sudden load change (decrease) bench test Figure 4 Results of the sudden load change (increase) bench test Figure 5 Results of the temperature-rise bench test (560-kW generating power) 4.2 Engine-matching Test After the bench tests at MHI, the MET83MAG hybrid...

Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012) 32 Also, sudden load change tests were conducted to confirm the effect of transient generator-load changes on the turbocharger operation. The results are shown in Figure 9. The turbocharger rotational speed became stable approximately 30 seconds after the sudden load change, and surging was not observed. 4.3 Results of sea trials Sea trials of the ship in which the MET83MAG was installed were conducted at the Universal Shipbuilding Corporation in April 2011. During the sea trials, parallel operation of the hybrid...

Mitsubishi Heavy Industries Technical Review Vol. 49 No. 1 (March 2012) 33 |5. Conclusion MHI has developed the hybrid turbocharger MET83MAG in collaboration with NYK Line, MTI, and Universal Shipbuilding Corporation. This is the world’s first practical application of a marine hybrid turbocharger. The turbocharger not only recovers electric power from excessive energy in the engine exhaust gas but also controls the air sent to the engine for combustion by controlling the power-generation rate. These characteristics are quite different from those of conventional turbochargers, whose...