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Research Papers

A Novel Gas Generator Concept for Jet Engines Using a Rotating Combustion Chamber

[+] Author and Article Information
Peter Jeschke

Institute of Jet Propulsion and Turbomachinery, RWTH Aachen University,
Templergraben 55,
Aachen 52062, Germany
e-mail: jeschke@ist.rwth-aachen.de

Andreas Penkner

Institute of Jet Propulsion and Turbomachinery,
RWTH Aachen University,
Templergraben 55,
Aachen 52062, Germany
e-mail: penkner@ist.rwth-aachen.de

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received November 6, 2014; final manuscript received November 10, 2014; published online January 7, 2015. Editor: Ronald S. Bunker.

J. Turbomach 137(7), 071010 (Jul 01, 2015) (8 pages) Paper No: TURBO-14-1288; doi: 10.1115/1.4029201 History: Received November 06, 2014; Revised November 10, 2014; Online January 07, 2015

A gas generator—consisting of a single-stage shrouded mixed-flow compressor without a diffusor, a rotating combustion chamber, and a vaneless single-stage shrouded centripetal turbine—is presented and analyzed here. All components comprise a coherent rotating device, which avoids most of the problems usually associated with small gas generators. In other words, the concept avoids all radial clearances; it is vaneless, shortens the combustion chamber, minimizes the wetted area, and enables ceramic materials to be used, due to compressive blade stresses. However, the concept faces severe structural, thermal, and chemical reaction challenges and is associated with a large Rayleigh-type total pressure loss. All these features and their implications are discussed and their benefits and drawbacks for several jet engines are quantified, mainly by means of thermodynamic cycle calculations. As a result, it has been demonstrated that the concept offers a thrust-to-weight ratio which is higher than the standard when incorporated into small unmanned aerial vehicles (UAV)-type jet engines. It also enables an attractive multistage and dual-flow, but fully vaneless design option. However, the concept leads to a decrease in thermal efficiency if these were to be accomplished in the (small) core of turbofans with highest overall pressure ratios (OPRs) and high bypass ratios. In summary, the paper presents a gas generator approach, which may be considered by designers of small jet engines with high power density requirements, like those used in UAV applications. But this has been proven not to be an option for high-efficiency propulsion.

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Figures

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Fig. 1

Schematic sketch of the engine concept

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Fig. 2

Meridional flow channel of the engine concept

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Fig. 3

Gas generator integrated in a counter-rotating turbofan

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Fig. 4

Relative Mach number and velocity vectors at 50% span for the low-speed design

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Fig. 5

Combustor total pressure ratio (high-speed design) over turbine inlet temperature as a function of combustor inlet temperature for fixed Mcax3 = 0.15 and cu = 396 m/s

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Fig. 6

SFC and thermal efficiency over booster stages for case 2 turbofan at test cell conditions

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Fig. 7

Thermal efficiency of case I (conventional turbofan), case II (low-speed gas generator turbofan), and case III (high-speed gas generator turbofan), at test cell conditions

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