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Technical Briefs

Design and Experimental Study of an Over-Under TBCC Exhaust System

[+] Author and Article Information
Jianwei Mo

e-mail: jianweimo12@gmail.com

Jinglei Xu

Professor
e-mail: xujl@nuaa.edu.cn

Liuhuan Zhang

e-mail: zhangliuhuan2008@126.com
Department of Power Engineering
Nanjing University of Aeronautics
and Astronautics
Nanjing 210016, China

Contributed by the Combustion and Fuels Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received February 3, 2013; final manuscript received July 10, 2013; published online October 21, 2013. Assoc. Editor: Piero Colonna.

J. Eng. Gas Turbines Power 136(1), 014501 (Oct 21, 2013) (8 pages) Paper No: GTP-13-1035; doi: 10.1115/1.4025314 History: Received February 03, 2013; Revised July 10, 2013

Turbine-based combined-cycle (TBCC) propulsion systems have been a topic of research as a means for more efficient flight at supersonic and hypersonic speeds. The present study focuses on the fundamental physics of the complex flow in the TBCC exhaust system during the transition mode as the turbine exhaust is shut off and the ramjet exhaust is increased. A TBCC exhaust system was designed using methods of characteristics (MOC) and subjected to experimental and computational study. The main objectives of the study were: (1) to identify the interactions between the two exhaust jet streams during the transition mode phase and their effects on the whole flow-field structure; (2) to determine and verify the aerodynamic performance of the over–under TBCC exhaust nozzle; and (3) to validate the simulation ability of the computational fluid dynamics (CFD) software according to the experimental conditions. Static pressure taps and Schlieren apparatus were employed to obtain the wall pressure distributions and flow-field structures. Steady-state tests were performed with the ramjet nozzle cowl at six different positions at which the turbine flow path were half closed and fully opened, respectively. Methods of CFD were used to simulate the exhaust flow and they complemented the experimental study by providing greater insight into the details of the flow field and a means of verifying the experimental results. Results indicated that the flow structure was complicated because the two exhaust jet streams interacted with each other during the exhaust system mode transition. The exhaust system thrust coefficient varied from 0.9288 to 0.9657 during the process. The CFD simulation results agree well with the experimental data, which demonstrated that the CFD methods were effective in evaluating the aerodynamic performance of the TBCC exhaust system during the mode transition.

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References

Figures

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Fig. 1

Over–under TBCC concept (Ref. [7])

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Fig. 2

Sketch of the TBCC exhaust system

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Fig. 3

Blowdown wind tunnel facility

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Fig. 4

Cut-away perspective view of the over–under TBCC exhaust nozzle model

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Fig. 5

Test points during TBCC exhaust-system mode transition

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Fig. 6

The typical computation grid of the over–under TBCC exhaust system

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Fig. 7

Pressure distributions along ramp relative to different grids and turbulence models

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Fig. 8

Control plane used for nozzle thrust calculations

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Fig. 9

Comparison of experimental static pressure data with CFD prediction at transition point I corresponding to the splitter cowl in the half-closed position

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Fig. 10

Comparison of experimental static pressure data with CFD prediction at transition point II corresponding to the splitter cowl in the half-closed position

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Fig. 11

Comparison of experimental static pressure data with CFD prediction at transition point II corresponding to the splitter cowl in the fully opened position

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Fig. 12

Comparison of Schlieren image with computational Mach contours at transition point II

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Fig. 13

Experimental Schlieren image at transition point II

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Fig. 14

Computational flow field structure of the TBCC exhaust system at transition point II

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