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Research Papers: Gas Turbines: Marine

Miller-Cycle Regulatable, Two-Stage Turbocharging System Design for Marine Diesel Engines

[+] Author and Article Information
Yi Cui

e-mail: ycui@sjtu.edu.cn

Zhilong Hu

e-mail: huzhilong_hrbeu@163.com

Kangyao Deng

e-mail: kydeng@sjtu.edu.cn

Qifu Wang

e-mail: holyvitas@163.com
Key Laboratory for Power
Machinery and Engineering of
Ministry of Education,
School of Mechanical Engineering,
Shanghai Jiaotong University,
Shanghai 200240, China

Contributed by the Marine Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 14, 2013; final manuscript received September 14, 2013; published online November 1, 2013. Assoc. Editor: Joost J. Brasz.

J. Eng. Gas Turbines Power 136(2), 022201 (Nov 01, 2013) (8 pages) Paper No: GTP-13-1050; doi: 10.1115/1.4025486 History: Received February 14, 2013; Revised September 14, 2013

The increasingly stringent NOx emission regulations of the International Marine Organization (IMO) have demanded new design concepts and architectures for diesel engines. The Miller cycle, which reduces the in-cylinder combustion temperature by reducing the effective compression ratio, is the principal measure used for reducing NOx specific emissions; however, this is at the cost of volumetric efficiency and engine power. Therefore, it is essential to combine the Miller cycle with a highly boosted turbocharging system, two-stage turbocharging for example, to recover the power. While much work has been done in the development of Miller-cycle regulatable two stage turbocharging system for marine diesel engines, there are nonetheless few, if any, thorough discussions on system optimization and performance comparison. This study presents a theoretical optimization design process for a Miller-cycle regulatable, two-stage turbocharging system for marine diesel engines. First, the different scenarios and regulation methods of two-stage turbocharging systems are compared according to the system efficiency and equivalent turbine flow characteristics. Then, a multizone combustion model based on a one-dimensional cycle simulation model is established and used for the optimization of valve timings according to the IMO NOx emission limits and fuel efficiencies. The high- and low-stage turbochargers are selected by an iterative matching method. Then, the control strategies for the boost air and high-stage turbine bypass valves are also studied. As an example, a Miller-cycle regulatable, two-stage turbocharging system is designed for a highly boosted high-speed marine diesel engine. The results show that NOx emissions can be reduced by 30% and brake specific fuel consumption (BSFC) can also be improved by a moderate Miller cycle combined with regulatable two-stage turbocharging.

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References

Figures

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Fig. 1

Configuration of regulatable two stage turbo charging system

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Fig. 2

The influence of regulation methods on system overall efficiency and equivalent turbine flow area

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Fig. 3

Design process of Miller cycle two-stage turbocharging system

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Fig. 4

Simulated and tested heat release rate and NOx emissions (overall NOx multiplier = 1)

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Fig. 5

The comparison of tested and simulated cylinder pressure curve of 100% load

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Fig. 6

The comparison of tested and simulated fuel consumption under propeller loads

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Fig. 7

Comparisons of tested and simulated maximum cylinder pressure under propeller loads

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Fig. 8

The effects of valve timing on NOx emissions and fuel efficiency

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Fig. 9

Design and matching method of two stage turbocharging system

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Fig. 10

The influence of volumetric efficiency on turbine’s equivalent flow area

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Fig. 11

The influence of volumetric efficiency on compressor’s pressure ratio

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Fig. 12

The influence of volumetric efficiency on reduced mass flow rate of compressors

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Fig. 13

The variations of excess air coefficients

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Fig. 14

Propeller operation points on high stage compressor map

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Fig. 15

Propeller operation points on low stage compressor map

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Fig. 16

Maximum cylinder pressures and exhaust temperatures of propeller operation points (without bypass)

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Fig. 17

The comparisons of BSFC and BSNOx between the new and the original engine

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Fig. 18

The comparison of system efficiency between regulatable two-stage and single stage turbocharging system

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