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Research Papers

Performance Evaluation of Solid Oxide Fuel Cell Engines Integrated With Single/Dual-Spool Turbochargers

[+] Author and Article Information
So-Ryeok Oh1

Naval Architecture and Marine Engineering,  University of Michigan, Ann Arbor, MI 48109srohum@umich.edu

Jing Sun

Naval Architecture and Marine Engineering,  University of Michigan, Ann Arbor, MI 48109jingsun@umich.edu

Herb Dobbs, Joel King

U.S. Army TARDEC, 6501 E. 11 Mile Road, Warren, MI 48397-5000

1

Corresponding author.

J. Fuel Cell Sci. Technol 8(6), 061020 (Oct 05, 2011) (12 pages) doi:10.1115/1.4004471 History: Received April 26, 2011; Revised May 08, 2011; Published October 05, 2011; Online October 05, 2011

This study investigates the performance and operating characteristics of 5kW-class solid oxide fuel cell and gas turbine (SOFC/GT) hybrid systems for two different configurations, namely single- and dual- spool gas turbines. Both single and dual spool turbo-chargers are widely used in the gas turbine industry. Even though their operation is based on the same physical principles, their performance characteristics and operation parameters vary considerably due to different designs. The implications of the differences on the performance of the hybrid SOFC/GT have not been discussed in literature, and will be the topic of this paper. Operating envelops of single and dual shaft systems are identified and compared. Performance in terms of system efficiency and load following is analyzed. Sensitivities of key variables such as power, SOFC temperature, and GT shaft speed to the control inputs (namely, fuel flow, SOFC current, generator load) are characterized, all in an attempt to gain insights on the design implication for the single and dual shaft SOFC/GT systems. Dynamic analysis are also performed for part load operation and load transitions, which shed lights for the development of safe and optimal control strategies.

Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 2

Finite volume discretization for a tubular SOFC

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Figure 3

(a) Fuel and air channels, PEN structure, and injection tube temperature along the cell length. (b) Fuel channel component mole fraction along the cell length.

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Figure 4

(a) Comparison between predicted and measured voltage-current density characteristics. An experimental data of a tubular Siemens Westinghouse SOFC presented in Ref. [1] has been used for the fuel cell model verification. (b) The predicted cell power versus current density profile.

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Figure 5

Normalized performance map for a compressor. It is based on a generic map from Ref. [15].

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Figure 6

Steady-state operating regimes of a single (LHS) and dual-shaft (RHS) SOFC/GT cycle: Turbine power, shaft speed, fuel cell temperature, and generator load. The efficiency data are plotted along the upper and lower boundaries of the feasible operating region.

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Figure 7

Comparison of power split ratios for single- and dual-shaft designs

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Figure 11

The dual-shaft operating regime to produce the net powers of 5.0kW and 5.7kW. (a) system efficiency, (b) fuel cell temperature as functions of a generator load and a SOFC current density.

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Figure 12

ROA sketch for a single-shaft SOFC/GT model with a net power of 5.7kW and input setting (WFuel ,ICOM ,PGEN ) =(0.002,2100,390). The ROA of a SOFC temperature and a CB mass are computed under four different initial turbine shaft speeds. The equilibrium point is (rpm,TCELL ,mCB ) = (65% rpm, 1039 °C, 0.117kg).

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Figure 13

Load step response of a single shaft SOFC/GT system from 4.7 kW TO 5.7 kW under highest (S1 , S3 , S4 )/lowest S2 efficiency setpoints for current density, fuel, and generator load as a function of load

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Figure 1

SOFC/GT Hybrid schematic: single-shaft (a) and dual-shaft (b)

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Figure 8

Operating envelope with SOFC power constraints: Single-shaft (upper plot) and dual-shaft (lower plot). The numbers on the plots indicate the output power of the SOFC.

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Figure 9

Operating envelope with temperature constraints: Single-shaft (upper plot) and dual-shaft (lower plot). The numbers shown on the plots are cell temperature TCELL in deg K.

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Figure 10

The single-shaft operating regime to produce the net powers of 5.0kW and 5.7kW. (a),(b) system efficiency 3D/2D maps, (c) fuel cell temperature variation at 1000 K, (d) shaft speed (x 105 ) as functions of SOFC current density and a generator load.

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Figure 14

ROA lower boundary for a dual-shaft SOFC/GT model for PNET  = 5.7kW and (WFuel ,ICOM ,PGEN ) = (0.0021,2000,50). The equilibrium point is (rpm,TCELL ,mCB ) = (67% rpm, 1042 °C, 0.15kg).

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Figure 15

System responses of a dual shaft SOFC/GT during a step from 4.6kW to 5.7kW, namely D1 → D3 and D2 → D3 . The same conditions as the single-shaft model simulation have been used.

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