Research Papers: Gas Turbines: Turbomachinery

Micro-Turbojet to Turbofan Conversion Via Continuously Variable Transmission: Thermodynamic Performance Study

[+] Author and Article Information
Kobi Kadosh

Turbomachinery and Heat Transfer Laboratory,
Aerospace Department,
Technion-Israel Institute of Technology,
Technion City,
Haifa 32000, Israel
e-mail: kobi.kadosh@campus.technion.ac.il

Beni Cukurel

Assistant Professor
Turbomachinery and Heat Transfer Laboratory,
Aerospace Department,
Technion-Israel Institute of Technology, Technion City,
Haifa 32000, Israel
e-mail: beni@cukurel.org

1Corresponding author.

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 20, 2016; final manuscript received July 4, 2016; published online September 13, 2016. Editor: David Wisler.

J. Eng. Gas Turbines Power 139(2), 022603 (Sep 13, 2016) (10 pages) Paper No: GTP-16-1249; doi: 10.1115/1.4034262 History: Received June 20, 2016; Revised July 04, 2016

In this study, the viability, performance, and characteristics of a turbojet-to-turbofan conversion through the use of a continuously variable transmission (CVT) are investigated. By an in-house thermodynamic simulation code, the performance of the simple cycle turbojet, a direct shaft joined turbofan, and a CVT coupled turbofan with variable bypass is contrasted. The baseline turbojet and turbofan findings are validated against a commercial software. The comparison indicates high quantitative agreement. Analyzing the results of the turbofan engine equipped with a variable bypass and CVT, it is observed that both the thrust and the efficiency are increased. The augmented thrust is observed to be an artifact of enhanced component matching and wider operational range introduced by variable bypass capability. On the other hand, the introduction of CVT contributes to the reduction in fuel consumption. Therefore, the current research suggests that adaptation of a micro-turbojet into a variable cycle micro-turbofan will greatly improve the performance and efficiency of existing engines, in addition to providing a pathway toward extended use in various applications.

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Nelson, J. , and Dix, D. M. , 2003, “ Development of Engines for Unmanned Air Vehicles: Some Factors to Be Considered,” Institute for Defense Analyses, Alexandria, VA, IDA Document D-2788. http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA412680
Gunston, B. , 1998, World Encyclopaedia of Aero Engines: All Major Aircraft Power Plants, From the Wright Brothers to the Present Day, Haynes Publishing, Yeovil, UK.
Saravanamuttoo, H. , Rogers, G. F. , and Cohen, H. , 2001, Gas Turbine Theory, Pearson Education, Upper Saddle River, NJ.
Sellers, J. , and Daniele, C. , 1975, “ DYNGEN: A Program for Calculating Steady-State and Transient Performance of Turbojet and Turbofan Engines,” National Aeronautics and Space Administration, Washington, DC, Report No. NASA TN D-7901. http://ntrs.nasa.gov/search.jsp?R=19750017548
Chiang, H.-W. D. , Hsu, C.-N. , Lai, A. , and Lin, R. , 2002, “ An Investigation of Steady and Dynamic Performance of a Small Turbojet Engine,” ASME Paper No. GT2002-30577.
Lichtsinder, M. , and Levy, Y. , 2002, “ Steady-State and Transient Performance of Single-Spool Turbojets Using Novel matlab Program,” Int. J. Turbo Jet Engines, 19(3), pp. 139–156. [CrossRef]
Dufour, G. , Carbonneau, X. , Cazalbou, J.-B. , and Chassaing, P. , 2006, “ Practical Use of Similarity and Scaling Laws for Centrifugal Compressor Design,” ASME Paper No. GT2006-91227.
Kurzke, J. , and Riegler, C. , 2000, “ A New Compressor Map Scaling Procedure for Preliminary Conceptional Design of Gas Turbines,” ASME Paper No. 2000-GT-0006.
Michel, U. , 2011, “ The Benefits of Variable Area Fan Nozzles on Turbofan Engines,” AIAA Paper No. 2011-226.
McBride, B. J. , Zehe, M. J. , and Gordon, S. , 2002, “ NASA Glenn Coefficients for Calculating Thermodynamic Properties of Individual Species,” National Aeronautics and Space Administration, John H. Glenn Research Center at Lewis Field, Cleveland, OH, Report No. NASA TP-2002-211556. http://ntrs.nasa.gov/search.jsp?R=20020085330
Lichtsinder, M. , and Levy, Y. , 2006, “ Jet Engine Model for Control and Real-Time Simulations,” ASME J. Eng. Gas Turbines Power, 128(4), pp. 745–753. [CrossRef]
Giffin, R. , Parker, D. , and Dunbar, L. , 1971, “ Experimental Quiet Engine Program Aerodynamic Performance of Fan A,” NASA, Washington, DC, Report No. NASA-CR-120858.
Nissan, 2015, “ XTRONIC CVT,” Nissan Motor Company, Kanagawa Prefecture, Japan. http://www.nissan-global.com/EN/TECHNOLOGY/OVERVIEW/cvt.html
Smithson, R. , Pohl, B. P. , Lohr, C. B. , Solis, J. , Nielsen, T. , McBroom, S. T. , and Munguia, N. , 2012, “ Auxiliary Power Unit Having a Continuously Variable Transmission,” U.S. Patent No. US8845485 B2. https://www.google.com/patents/US8845485
Youssef, N. , 2012, “ Gas Turbine Aircraft Engine With Power Variability,” U.S. Patent No. US8181442 B2. https://www.google.com/patents/US8181442


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Fig. 1

Existing engines of less than 1000 lbs of thrust. (Reproduced with permission from Nelson and Dix [1]. Copyright 2002, 2003 by Institute for Defense Analyses.)

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Fig. 2

Baseline turbojet component maps: (a) compressor, (b) turbine efficiency, and (c) turbine mass flow rate

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Fig. 4

Schematic drawing of a turbojet

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Fig. 5

Turbojet simulation flowchart

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Fig. 6

Schematic drawing of a turbofan

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Fig. 7

Fixed-gear turbofan simulation flowchart

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Fig. 8

Illustration of CVT coupled turbofan with variable bypass nozzle: (1) fan, (2) CVT gearbox, and (3) variable bypass nozzle

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Fig. 9

Turbojet compressor map from gasturb 11 and in-house simulation

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Fig. 10

CVT coupled turbofan—fuel flow versus thrust

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Fig. 11

CVT coupled turbofan—operating lines on maps of (a) fan, (b) compressor, (c) turbine efficiency, and (d) turbine mass flow

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Fig. 12

Turbofan with variable bypass nozzle—operating lines on maps of (a) fan, (b) compressor, (c) turbine efficiency, and (d) turbine mass flow

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Fig. 13

Fan map of the CVT coupled turbofan with variable bypass nozzle—maximum efficiency operating line

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Fig. 14

Comparison of various cycles—fuel flow versus thrust



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