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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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References

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Figures

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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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